CA1251843A - Door or gate obstruction control - Google Patents
Door or gate obstruction controlInfo
- Publication number
- CA1251843A CA1251843A CA000496197A CA496197A CA1251843A CA 1251843 A CA1251843 A CA 1251843A CA 000496197 A CA000496197 A CA 000496197A CA 496197 A CA496197 A CA 496197A CA 1251843 A CA1251843 A CA 1251843A
- Authority
- CA
- Canada
- Prior art keywords
- motor
- operating characteristic
- operating
- control arrangement
- change
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
- H02H7/085—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against excessive load
- H02H7/0851—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against excessive load for motors actuating a movable member between two end positions, e.g. detecting an end position or obstruction by overload signal
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/44—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to the rate of change of electrical quantities
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
- H02H7/085—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against excessive load
- H02H7/0854—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against excessive load responsive to rate of change of current, couple or speed, e.g. anti-kickback protection
Abstract
ABSTRACT
An obstruction sensing and control arrangement for door or gate opening-closing mechanisms.
The arrangement compares the operating rate of change of a predetermined characteristic with a preset rate of change and stops or reverses the motor in the opening/
closing mechanism. The characteristic preferred is motor body temperature which is monitored indirectly. The control arrangement also includes a back up static control threshold to sense a second static operating characteristic of the motor and a second comparator means set at a preset threshold level to stop or reverse the motor. A common motor sensor is used for both the dynamic and static control thresholds. The invention also includes means to sense operating temperature and to alter the preset static threshold level automatically in response to temperature changes.
An obstruction sensing and control arrangement for door or gate opening-closing mechanisms.
The arrangement compares the operating rate of change of a predetermined characteristic with a preset rate of change and stops or reverses the motor in the opening/
closing mechanism. The characteristic preferred is motor body temperature which is monitored indirectly. The control arrangement also includes a back up static control threshold to sense a second static operating characteristic of the motor and a second comparator means set at a preset threshold level to stop or reverse the motor. A common motor sensor is used for both the dynamic and static control thresholds. The invention also includes means to sense operating temperature and to alter the preset static threshold level automatically in response to temperature changes.
Description
COMPLETE SPECIFICATI)ON FOR C A N A D A
, BE IT KNOWN THAT , RAYMOND LESLIE SEIDEL, of 8 Pascoe Croydon, ~ictoria, Aus-tralia, and MARIAN UIOLA, of 8 Kiama Street, Redwood Park, South Australia, Australia, having made an invention entitled:
"DOOR OR GATE OBSTRUCTION CONTROL"
the following disclosure contains a correct and full description of th einvention and of the best mode known to the inventors of taking advantage oF the sarne.
DOOR O~ GA~ OB'~TF~(`T~ CONTROL
The present invention rela-tes generally -to power operated gates and dGors and mcre particularly -to a safety control arrangement associated wi-th such doors ar,d gates.
It has become reasonably common in recent times to provide garage doors and property access gates with power operated opening and closing mechan-isms. Commonly such arrangements include a sui-table opera-ting mechanism (dependent upon the nature of -the door or gate being opened 10 or closed) and an electric motor (which might be an AC or DC motor) tc power the operating mechanism. The operating mechanism might be directly controlled by suitable switching associated with the equiprnent or it might be remotely controlled using radio signals directed to a 15 suitable receiver arranged with the mechanism. The more common usage of remote control arrangements with such equipment has led to the substantial danger of seriously injuring persons or equipment which might be accidently located in the path of movement of the gate or door. For 20 example the operating mechanism could conceivably be operated either inten-tionally or unintentionally from a position beyond the view of the opera-tor and in such circumstances it would be possible for a person such as a child or perhaps a less agile elderly person to be seriously hurt by -t~!e door or gate. There have been many proposals fcr providing safety mechanisms with such doors and gates to try to avoid this danger. One such arrangement required the positioning of a mechanical trip bar which would be hit by any obs-truction in the pa-th of -travel of the dcor or ga-te, the trip bar being operably connected to a suitable mechanical linkage for actua-ting a switch to either stop or perhaps reverse -the operating motor. A
similar concept in a mechanical system where a chain drive for the door or gate was employed, used deflections in -the chain indicative of an obs-truction being hit, to physically actuate sui-table switching to stop or reverse the electric operatiny mo-tor. These mechanical systems have been found '~
~Z~ 3 in practice to lack sensitivi-ty and reliability and moreover are relatively complieated and expensive -to produce.
A second approach to this problem recognized that 5 when a signiflcant obstruc-tion was engaged by the door or gate, the operating motor would draw significantly more current than was usual. Thus monitoring motor current, theoretically, gave some idea of whether or not -the door or gate was operating freely. In a known static safety control 10 system, it has been known to monitor motor current (after a predetermined start up period) during the period when motor current should be theoretically relatively stable and to compare this current to a preset value such that if this preset curren-t is exceeded indicative of an obstruction 15 being engaged, a suitable control actua-tes to either stop or reverse the operating motor. While -this known system is theoretically func-tional, it has proved to have significant problems in practice. In prac-tice the current drawn by -the motor during -the opening or closing operation is never 20 uni-rorm. For example, on very cold days, lubrica-ting grease will be vas-tly s-tiffer than on ho-t days thereby resulting in significant friction increases. Similarly wind loading varies considerably and has significant effects on loading of the door or gate during opening or closing. Furthermore, 25 -the current drawn by the motor running in one direction could vary up to 10% from -that which would occur wi-th the motor running in -the reverse direction regardless of all these factors. In addition with cer-tain -types of doors or ga-tes (typically lifting and tilting garage doors) the load 30 during opening and closing is i-tself not constant and the theore-tical current drawn by the motor increases substantially midway through its cycle. To achieve a sensitive safety control operation i-t is desired to place the set poin-t as close as possible above the theoretieal 35 curren-t drawn, however, beeause of the above factors, it has been found in prac-tice tha-t -the set point must be ~zs~
placed greatly above the theoretical current drawn to avoid the safety con-trol operating when it is no-t necessary.
Often this has resulted ln the safety control set point being set that high that it has very lit-tle appreciable 5 effect in controlling the door or gate when an obstruction is in fact met.
The principal objective of the present invention is to provide a safety control for door or gate operating mechanism of improved performance charac-teristics which 10 will be activated by the door or gate effec-tively meeting an obstruction in its path of travel. A so called "dynamic set point" or dynamic control threshold is achieved effectively by sensing rate of change of operating characteristics of the opera-ting motor of the door or ga-te 15 mechanism which follows the normal motor load characteristic curve.
Accordingly the present inven-tion provides an obstruction control arrangement for a door or gate opening/closing mechanism having an electric operating motor, said control arrangement comprising first mo-tor sensor means adapted to sense a first operating character-istic of said motor, circui-t con-trol means arranged to determine an operating rate of change of the first operating characteristic sensed by said motor sensor means, first compari-tor means arranged to compare said operating rate of change of the opera-ting characteristic with a preset rate of change level, and activating means arranged to stop or reverse said elec-tric motor in response -to an activating signal from said cornparitor means upon said operating rate of change of the operating characteristic exceeding said prese-t rate of change level being indicative of said door or gate being obstructed in its normal course of travel.
Conveniently the con-trol arrangemen-t further includes filter means arranged to pass signals only in a predetermined frequency range from said motor sensor means to the comparitor means. The frequency range transmitted would normally be less than lO Hertz and preferably in the range o-f 5 -to lO Hertz.
In accordance with a preferred embodiment the control arrangement further includes a back-up static control threshold of the type including a second motor sensor means adapted to sense a second static operating characteristic level of said motor and second comparitor means arranged -to compare the sensed static operating 10 characteristic level with a preset static threshold level whereby an activating output signal is generated upon said sensed static operating characteristic level exceeding said preset threshold level and is delivered to said ac-tivating means to stop or reverse said electric motor. Conveniently a common motor sensor means is used for both the dynamic control threshold and the static control threshold. The arrangement may further include temperature compensa-tion means arranged to sense operating temperature and to move the preset static -threshold level automatically in response to temperature changes.
Preferably the temperature compensation includes a thermal sensor such as a Silicon diode or a Germanium diode arranged in a vol-tage divider network used to establish the present rate of change level for the comparitor means.
In a preferred embodiment the operating temperature of the mo-tor body is monitored indirectly as it is not desirable to have the thermal sensor physically attached to the motor body as this is most often remo-te from circuitry associated with the con-trol of the door or gate opening/closing mechanism and would require additional wires tc carry the required information back -tc the main circuitry. Accordingly the present invention preferably proposes using the thermal sensor in contact with a power supply bridge rec-tifier for the operating motor as the entire motor current mus-t flow -through this bridge rectifier. Consequently it follows -that the temperature of the bridge rec-tifier will rise ln proportion -to -that o~ -the remote operating motor. It is, however, desirable tha-t the thermal inertia of the operating mo-tor and -the bridge rectifier circuit, be perfec-tly matched to achieve optimum results. Simultaneously, the same thermal sensor will also sense ambient temperature changes and consequently compensation is achieved fc,r opera-ting temperatures resulting from both ambient changes and changes due to the operation of the equipment.
A possible alternative location for the thermal sensor could be against a series resistor used tc, monitor the operating motor current. However, this is not quite as good a location as the power supply bridge rectifier circuit as the temperature rise of -the monitoring resistor is much lower than the rectifier circuit where the power developed in heat is much higher.
In accordance with a further preferred embodiment, the first sensor means comprises at least one sensor arrangemen-t adapted -tc sense -the first opera-ting characteristic of said motor at r~pea-ted predetermined time intervals, said circui-t control means including a firs-t circuit operatiny to determine an actual change of the operating characteris-tic over said predetermined time intervals and said first comparitor means including a second circuit operating to compare said change of operating characteris-tic over said prede-termined time intervals with a preset change whereby said ac:tivating signal is generated if said actual change exceeds said preset change. Conveniently -the first sensor means comprises a plurality of said sensor arrangernents each being arranged to sense the opera-ting characteristic at said prede-termined intervals of time, all the sensor arrangements subsequent to a first one of said sensor arrangements commencing their respective prede-termined time intervals within the predetermined time interval of said first sensor arrangement whereby the sensor arrangements are staggered with respect to one another so as to reduce -the response -time required tc activa-te said con-trol arrangement. Preferably the preset change is determined by accumulating incremental changes in -the operating characteristic over a predetermined number of said -time 5 intervals immediately prior to the actual change of the operating characteristic compared at the end of any said time interval.
In some embodiments of this lnvention there is provided inhibitor means arranged -to inhibi-t operation of 10 the control arrangement during an initial time period of each operating cycle.
The present invention will now be described with reference to several preferred embodiments illustrated in the accompanying drawings, in which:
15Figure 1 illustrates typical theore-tical and prac-tical operating characteristics of a door or gate operating mechanisms during both opening and closing cycles of opera-tion;
Figure 2 shows, in block di.agram form, a control arrangement in accordance wi-th a first preferred embodiment of the present invention employing both a dynamic threshold control and a temperature compensated back-up static control;
Figure 3 shows typical circuitry for a temperature compensated static control system;
Figure ~ shows typical circuitry for a dynamic tracking control system;
Figure 5 shows typical circuitry for a control system employing both -temperature compensated static control and dynamic tracking control;
Figure 6 il.lustrates graphically operating characteristics according to the present invention;
Figure 7 shows a circuit diagram illustrating a second preferred embodiment of the presen-t invention;
35Figure 8 illustra-tes graphically the operation of an embodiment of -the type shown in Figure 7;
S~ 3 Figure 9 illustrates graphically -the operation of a control arrangement similar -to figure 7 bu-t incorporating multiple sensors adapted to sense operational characteristic changes o~er predetermined in-tervals with 5 the intervals commencing in staggered time relationship relative to one another; and Figure lO shows graphically a typical operating motor current variation during a door opening cycle with a control arrangement according -tc Figure 7.
Figure 2 of the drawings schema-tically shows in block diagram format a first preferred control arrangement employing two independent control level sensing mGdes of operation. In the drawings M represents the operating motor for a gate or door opening/closing mechanism. Rs is a 15 sensing resistor used to sense load or current drawn by the motor M. LPF represents a filter adapted to pass signals in a low frequency band (typically from 5 to lO Hz) from the sensor Rs to the control circuit. An amplifier A amplifies and transmits -the signal from the low frequency pass filter 20 LPF to a temperature compensated comparitor CA and separately to dynamic tracking controlled comparitor CB
which is adap-ted to compare ra-tes of change of the current drawn by the motor M with a prese-t level. ~aturally, if desired the comparators CA and CB could be used in quite 25 separate control arrangements. Each of the comparitors CA
and CB generate an activating signal in response to the load sensed by Rs exceeding a predetermined limit indicative of the door or gate hitting an obstruction. The activating signals are then combined by an OR gate combiner 30 circuit C and used to either stop or re-verse operation of the motor M. Finally an inhibitor circui-t In is used to inhibit the control circuit for a prede-termined period a-t start up of the operating motor for reasons which will be explained hereinafter.
Typical load operating characteristics of the motor M are shown in the drawings (Figures 1 and 6). Figure ~L~5~ 3 l shows both an opening and a closing characteristic which can be up to 10% difEerent from each o-ther. These graphs show motor current I against time but it will be appreciated that other operating charac-teris-tics might also 5 be employed. I~mediately upon s-tart up -there is a rapid rise in motor current drawn which peaks quickly and se-ttles back almost as quickly into a theoretical substantially uniform load current. The full line graph (a) in Figure l demonstrates a typical theoretical opening and closing load 10 curve against time t. The critical start up period is irrelevant from a safety viewpoint and moreover the high load experienced in this period makes monitoring of the load pointless with regard to safety con-trol. For this reason the inhibitor circuit In is included to override the 15 control circuit for the initial start up period ts. There-after the control circuit becomes effective. In the conventional static control system a constant set point SP
is es-tablished above the theoretical load curve such that if an obs-truction is hit by the door or ga-te, -the load 20 curve rises rcpidly as indicated at (c) and the door or gate is stopped or reversed. However as indicated in the introduction -to this specification, the practical load curve (b) for m~ny reasons will vary considerably from the theoretical curve (a) and it will be obvious from -these 25 graphs that either the se-t point SP must be located tco high for safe operation or the control system will activate itself when there is in fact no obstruc-tion.
According to a preferred aspect of -the present invention it has been recognized tha-t -the rotary ac-tion of 30 the armature of the mo-tor M with the re~sulting commu-tation of the brushes agains-t -the commu-tator give rise -tG finite opening and closing of the motor circui-t a-t a relatively high "chopping" rate. Typically -the frequency of this occurs at around 300 per second but of course this high frequency chopping rate depends on the speed of the motor which is variable. In addition where the primary power source is derived from the 240V main supply there will also ~S~ 3 be high components of 50Hz and lOOHz. I-t is also recognized that frequencies resulting from an obstruc-tion being hit by a door or gate will occur with a relatively well defined low frequency range width (normally within the range of 5 5 to lOHz). In the proposed system the aforementioned chopping high frequency component (and in o-ther higher frequency component) is filtered out leaving only a DC
average and frequency components up to a prede-termined level, typically lOHz. This is achieved by the low 10 frequency pass filter LPF shown in the drawings.
Figure 6 of the drawings illustrates graphically the performance of the control system according to the preferred arrangement of Figure 2. Firstly there is provided a movable constant static set poin-t Ssp. The set 15 point is movable in response to tempera-ture changes arld in particular to both sensed ambien-t temperature changes AHS
and sensed motor temperature changes MHS. If the temperature is generally cold then -the motor is likely to draw more current and thus the set point Ssp is moved 20 upwardly. Conversely if -the temperature is hot the motor is likely to draw less current and the se-t poin-t Ssp will move down. Conveniently both ambient and motor temperature changes can be sensed by single tempera-ture sensing Silicon or Germanium diode Di. The posi-tioning of this diode is conveniently as previously discussed. As shown in Figure 3 the signal from the mo-tor sensing resistor Rs is fil-tered and amplified by an amplifier A and supplied tc one inpu-t terminal of a non inverting voltage comparitor IC2. The temperature sensing diode Di directs its signal tG the o-ther terminal of -the comparitor and in this manner an automatic variation of the set point Ssp is achieved in response to temperature variations. Normally when the static tempera-ture compensated control is being used as back-up in a combined system of the -type shown in Figures 2 and 5, the basic set point wi]l be arranged at a relatively high point such that i-t would only be used should the .,,~ .
.,~ , 12S~ 3 dynamic con-trol fail for whatever reason.
Figure 6 also illustra-tes -the automatic tracking or dynamic threshold capability of the filter Al`F to provide an au-tomatic dynamic se-t poin-t Dsp above the actual 5 load (b) regardless of changes in this load. Thus in the monitoring zone beyond the initial inhibi-t period -ts should an obstruction be hit by the door or gate, the lc,w frequency increase in load is passed by the filter LPF to the control system comprising the tracking filter ATF and 10 the comparitor CB. The load thus follows the curve (c) and the comparitor CB will sense when the load exceeds the dynamic set point Dsp and will send a signal in response thereto -to stop or reverse the motor M.
Suitable circuitry for the automatic -tracking 15 *ilter ATF is shown in Figure 4. This circuit maintains its DC output at Vbb/2 for all input componen-ts up to 5Hz such -that it is not responsive to these components and more particularly maintains its ou-tput at Vbb/2 regardless of the absolute magnitude of the magni-tude of t~]e DC input.
Its response is basically a high pass fil-ter and allows through only those motor "impulse" components within the range SHz tc lOHz.
Experiments have shown tha-t for most applica-tions requiring a motorized door/gate to sense an obstruction, the impulse components predominantly lie within this spectrum. If required the band of interest could be lowered by changing R3/C1 and raised by appropriately decreasing the component values of -the input fil-ter LPF.
The combination R3/C1 gives this filter -the required tracking characteristic in tha-t the voltage across Cl follows (with some -time delay) the input voltage being examined.
The integrated circui-t IC3 arranged in -the manner illustrated is in fact an Inverting Amplifier such that an impulse rising at Vin will cause the outpu-t to fall from i-ts quiescent Vbb/2 level toward ground potential and vice versa. The gain (AC gain) is de-termined by the ratio of the componen-ts R2/Rl. The resistors Rl and R3 should preferably be equal and similarly the resistors R2 and R4 should pre-ferably be equal -to achieve good common 5 mode operation. Should the components no-t be matched in this manner, the outpu-t voltage will not remain itself at Vbb/2 for all input components up to 5Hz and consequently erratic operation could result. Normally components matched within +2% would provide satisfactory operation. The 10 magnitude of the output impulse response has been found to be adequate to trigger the following level compari-tor IC4 of the comparitor circuit CB, if the gain of the integrated circuit IC3 is set within the range of 5 to 10. It is preferred for the capacitor Cl to be a low leakage type 15 whose value could be of the order of 10 microfarad when Rl and R3 are of the order o-f lOOK ohm. The time constant R3Cl is typically 0.1 second but could be lowered -to 0.5 second if required.
Once a sufficiently high impulse component at -the 20 input has been allowed through to the -tracking fil-ter ATF
and consequen-tly causes the output to swing below a predetermined value as set by the comparitor CB, then an overload signal is generated which will stop the motor M.
Subsequently, depending on -the exis-ting motor control 25 logic, either a dwell will resul-t or the motor will be instantly reversed. In either case the ou-tput of the tracking fil-ter ATF will over shoot in the opposite direction, however, this is of no concern to the circuitry as an inhibit signal from the Inhibitor In holds the total 30 response of -t~e control circuitry in an "off" state.
Figure 7 of the accompanying drawings shows a second preferred con-trol arrangement in accordance with the present invention. In this embodiment, -the con-trol arrangemen-t comprises circuitry which monitors -the rate of 35 change of current (i.e. the slope of the current versus time graph) during the opera-tion of opening the door or gate. The measured rcte of change of current is -then compared wi-th a preset rate of change, and if this preset rate of change is exceeded the safe-ty control circuit wil reverse or stop the operation of the motor. Therefore by 5 comparison with a system which requires the mo-tor current to reach a static threshold point, the present system will sense when the motor current is likely to exceed a threshold value thereby allowing much quicker opera-tion of the safety circuit.
Figure 7 of the drawings shows a circuit using a rate of current change measurement method. The curren-t drawn by Motor M is monitored by me~asuring the voltage across a resistor Rs~nse, which is in series with the motor coil. This voltage reading will be proportional to 15 the current being drawn by the mo-tor. This signal is then fed to an amplifier A via a low pass filter LPF. The low pass filter has a cut off frequency typically of 10 Hertz.
The voltage signal is then amplified and inverted and subsequently becomes an input to the comparator. The other 20 voltage input tc -the comparator is generator by an R-C
integrator. Both -the comparator and R-C integra-tor are connected -to a microprocessor at points A and B
respec-tively. Point B provides a pulsed output varying between a logic "high" voltage and a logic "low" voltage.
25 When the output of point B goes high the transistor Q1 is switched on, thereby discharging capacitor Cref. Upon output B going low the transistor Q1 is switched off and a counter internal to the microprocessor is initiated. When the transistor Q1 is switched off the voltage Vr~f 30 increases from a zero value. This rate of increase is Y r~!f ref integrator). The output of the comparator VOUt remains a-t a logic "high" level ur~til V ~f exceeds -the voltage value of the other comparator input, Vin, whereupon VOUt goes 35 to a logic "low" level. When the ou-tput voltage of the comparator, VOUt goes to a logic "low" level, the internal counter of the microprocessor is stopped and the ~2Si~3~3 value of -this counter is -thereby proportional -to the motor current. This count is used as a digital number representing the motor current for tha-t particular measurement interval.
The microprocessor is programmed to calcula-te the actual rate of change of curren-t of the motor M, -to compare this rate of change with a preset rate of change, and to activate the control arrangement of t~le motor M in the case where the actual rate of change of current of the motor M
10 exceeds the prese-t value. The value of the motor current is sampled by the microprocessor at a r2te of 500 Hertz (i.e.
at a 2 msec intervals). Four such motor current samples are accumulated by the microprocessor to obtain an accumulation of current change over those four sample points thereby 15 magnifying and noise averaging the change in current. The microprocessor uses the firs-t sample point as the base value of motor current and to this is added the incremen-t in current that will give the preset ra-te of change. The microprocessor will then compare the actual rate of change 20 with this preset rate of change, and if -the actual rate of change exceeds the preset rate, -the safety control circuits will be activated.
Figure 8 shows a graphical representation of the operating charac-teristics of the con-trol arrangement in 25 accordance with Figure 7. The graph i]lustrates a portion of cycle showing motor current I against time and the slope measurement time intervals as shown on -the graph represent the time intervals in which the rate of change of motor current is de-termined. Each set of four samples are 30 compared with the prese-t rate of change. As shown in this graph when the actual rate of change equals or exceeds the preset overload value during that time interval -the safety control sys-tem is activated. Also shown on this graph are two horizontal lines one representing the average current 35 level and another representing a trip current. The trip current line is positioned at a level equivalent to a ~2S~8~
maximum current which is not to be exceeded by the motor, and is typically the current level used by a safety control system which simply monitors current levels. It can be seen from Figure 8 tha-t the slope comparison technique will 5 enable the safety control circuits within a considerably shorter time that a system using only instantaneous current comparison -techniques.
In order to further reduce the response time of the safety control system, a fur-ther embodimen-t of this 10 invention incorporates a plurality of sensing means which have staggered measurement time intervals. Figure 9 shows a graphical representation similar tc Figure 8 of the operation of such a system. As can be seen from Figure 9 the sensing means circui-ts 1, 2, 3, and 4 are arranged such 15 that they operate in parallel, but have their slope measurement -time intervals staggered in relation to one another, i.e. -the measurement time intervals of circuit 2 commence slightly after circuit 1, -the measuremen-t time intervals of circui-t 3 commence sligh-tly after circuit 2, 20 the measurement time intervals of circuit 4 commence slightly after circuit 3 and at the end of -the circui-t 4 time measuremen-t period, circuit 1 again commences measurement. As can be seen from the graph the current draw of the mo-tor M begins -to be excessive at point A. However, 25 the measurement time intervals of circuit 1 would produce an average curren-t slope less than the required overload slope even though -the measurement -time interval overlaps point A. The same occurs with circuit 2. However circuit 3 includes enough data points to give a measured slope which 30 equals or exceeds -the overload slope and -therefore activates -the safe-ty con-trol c'rcui-t. It can be seen from the graph that if circuit 1 was -the only sensing means being used it would require a further measuremen-t time interval so as to sense the overload slope, and would 35 -therefore result in a significan-t delay in -the activation of the safety control circui-ts. It can be seen therefore, that by using multiple sensing means which have st,aggered ;~ZS18'~3 measurement time intervals, ~the reac-tion time of such a sys-tem can be ~reatly improved.
Figure lO shows a curve of curren-t I vs time t during the opening of a door, and illustrates the variation 5 of the current level during the cycle from closed to open.
It can be seen that part way through the cycle, the current decreases, and in relation to -the trip current level, conventional safety circuit would have an increased response time to an overload or obstruction (and hence 10 force), thereby resulting in poor sensitivity. Superimposed over the current level are a representative sample of preset overload slopes, which show the r~te of current increase required to opera-te the safety control circuits.
The graph demonstrates that this type of system has a 15 constant degree of sensitivity, since the rate of change measuremen-t sys-tem "follows" the current curve providing a dynamic tracking control similar to the embodiment of Figure 2.
The current peak shown in Figure lO results during 20 motor start up. During this period, the safety control circuit is provided with a sensing means to control the operation of the motor and the safety control circuit. This sensing means monitors the rise and fall of the star-t up peak, checking that it both reaches a peak, and falls again 25 to normal opera-ting conditions. If the motor stalls, the current peak will not fall and therefore the safe-ty control circuit will prevent further operation. Also, if as a result of some other failure, the motor fails to start or we have a failure in -the measuring circui-t, then again the 30 safety control circuit will prevent further opera-tion. This will be the case for bo-th directions of operation.
The use of such a system has several advantages over previously used static current sensing means. Because the measurement of curren-t slope is a rela-tive measurement 35 no complicated field adjustment is required upon installation to check and adjus-t set points. The overload .. . .
:~2Sl~
rate of curren-t change c~n be simply programmed into a microprocessor, and the use of such microprocessors will a7so greatly reduce the cost of such a control circuit and allow other functions such as swi-tching, tG be incorporated 5 in its operation. The use of a safety control arrangement which employs a ra-te of current change sensing system means that normal variations in current drawn by -t~'e mo-tor, which result from wind loading or variation in bearing friction, guide effects will nGt result in activation of the safety 10 control circuit, and only those curren-t variations which are excessively high will result in activation of the safety circuit. In addition the use of multiple sensing circuits will result in a very fast response time, where only 0.15 of a second is required to sense and produce 15 action as a result of an overload. Also the overload sensitivity will be -the same for both direc-tions of travel of such a door or gate, the force required to activate the safety circuit will be constant over the full operating range, and -the sys-tem will automa-tically adapt to any 20 number of drive motors used.
, BE IT KNOWN THAT , RAYMOND LESLIE SEIDEL, of 8 Pascoe Croydon, ~ictoria, Aus-tralia, and MARIAN UIOLA, of 8 Kiama Street, Redwood Park, South Australia, Australia, having made an invention entitled:
"DOOR OR GATE OBSTRUCTION CONTROL"
the following disclosure contains a correct and full description of th einvention and of the best mode known to the inventors of taking advantage oF the sarne.
DOOR O~ GA~ OB'~TF~(`T~ CONTROL
The present invention rela-tes generally -to power operated gates and dGors and mcre particularly -to a safety control arrangement associated wi-th such doors ar,d gates.
It has become reasonably common in recent times to provide garage doors and property access gates with power operated opening and closing mechan-isms. Commonly such arrangements include a sui-table opera-ting mechanism (dependent upon the nature of -the door or gate being opened 10 or closed) and an electric motor (which might be an AC or DC motor) tc power the operating mechanism. The operating mechanism might be directly controlled by suitable switching associated with the equiprnent or it might be remotely controlled using radio signals directed to a 15 suitable receiver arranged with the mechanism. The more common usage of remote control arrangements with such equipment has led to the substantial danger of seriously injuring persons or equipment which might be accidently located in the path of movement of the gate or door. For 20 example the operating mechanism could conceivably be operated either inten-tionally or unintentionally from a position beyond the view of the opera-tor and in such circumstances it would be possible for a person such as a child or perhaps a less agile elderly person to be seriously hurt by -t~!e door or gate. There have been many proposals fcr providing safety mechanisms with such doors and gates to try to avoid this danger. One such arrangement required the positioning of a mechanical trip bar which would be hit by any obs-truction in the pa-th of -travel of the dcor or ga-te, the trip bar being operably connected to a suitable mechanical linkage for actua-ting a switch to either stop or perhaps reverse -the operating motor. A
similar concept in a mechanical system where a chain drive for the door or gate was employed, used deflections in -the chain indicative of an obs-truction being hit, to physically actuate sui-table switching to stop or reverse the electric operatiny mo-tor. These mechanical systems have been found '~
~Z~ 3 in practice to lack sensitivi-ty and reliability and moreover are relatively complieated and expensive -to produce.
A second approach to this problem recognized that 5 when a signiflcant obstruc-tion was engaged by the door or gate, the operating motor would draw significantly more current than was usual. Thus monitoring motor current, theoretically, gave some idea of whether or not -the door or gate was operating freely. In a known static safety control 10 system, it has been known to monitor motor current (after a predetermined start up period) during the period when motor current should be theoretically relatively stable and to compare this current to a preset value such that if this preset curren-t is exceeded indicative of an obstruction 15 being engaged, a suitable control actua-tes to either stop or reverse the operating motor. While -this known system is theoretically func-tional, it has proved to have significant problems in practice. In prac-tice the current drawn by -the motor during -the opening or closing operation is never 20 uni-rorm. For example, on very cold days, lubrica-ting grease will be vas-tly s-tiffer than on ho-t days thereby resulting in significant friction increases. Similarly wind loading varies considerably and has significant effects on loading of the door or gate during opening or closing. Furthermore, 25 -the current drawn by the motor running in one direction could vary up to 10% from -that which would occur wi-th the motor running in -the reverse direction regardless of all these factors. In addition with cer-tain -types of doors or ga-tes (typically lifting and tilting garage doors) the load 30 during opening and closing is i-tself not constant and the theore-tical current drawn by the motor increases substantially midway through its cycle. To achieve a sensitive safety control operation i-t is desired to place the set poin-t as close as possible above the theoretieal 35 curren-t drawn, however, beeause of the above factors, it has been found in prac-tice tha-t -the set point must be ~zs~
placed greatly above the theoretical current drawn to avoid the safety con-trol operating when it is no-t necessary.
Often this has resulted ln the safety control set point being set that high that it has very lit-tle appreciable 5 effect in controlling the door or gate when an obstruction is in fact met.
The principal objective of the present invention is to provide a safety control for door or gate operating mechanism of improved performance charac-teristics which 10 will be activated by the door or gate effec-tively meeting an obstruction in its path of travel. A so called "dynamic set point" or dynamic control threshold is achieved effectively by sensing rate of change of operating characteristics of the opera-ting motor of the door or ga-te 15 mechanism which follows the normal motor load characteristic curve.
Accordingly the present inven-tion provides an obstruction control arrangement for a door or gate opening/closing mechanism having an electric operating motor, said control arrangement comprising first mo-tor sensor means adapted to sense a first operating character-istic of said motor, circui-t con-trol means arranged to determine an operating rate of change of the first operating characteristic sensed by said motor sensor means, first compari-tor means arranged to compare said operating rate of change of the opera-ting characteristic with a preset rate of change level, and activating means arranged to stop or reverse said elec-tric motor in response -to an activating signal from said cornparitor means upon said operating rate of change of the operating characteristic exceeding said prese-t rate of change level being indicative of said door or gate being obstructed in its normal course of travel.
Conveniently the con-trol arrangemen-t further includes filter means arranged to pass signals only in a predetermined frequency range from said motor sensor means to the comparitor means. The frequency range transmitted would normally be less than lO Hertz and preferably in the range o-f 5 -to lO Hertz.
In accordance with a preferred embodiment the control arrangement further includes a back-up static control threshold of the type including a second motor sensor means adapted to sense a second static operating characteristic level of said motor and second comparitor means arranged -to compare the sensed static operating 10 characteristic level with a preset static threshold level whereby an activating output signal is generated upon said sensed static operating characteristic level exceeding said preset threshold level and is delivered to said ac-tivating means to stop or reverse said electric motor. Conveniently a common motor sensor means is used for both the dynamic control threshold and the static control threshold. The arrangement may further include temperature compensa-tion means arranged to sense operating temperature and to move the preset static -threshold level automatically in response to temperature changes.
Preferably the temperature compensation includes a thermal sensor such as a Silicon diode or a Germanium diode arranged in a vol-tage divider network used to establish the present rate of change level for the comparitor means.
In a preferred embodiment the operating temperature of the mo-tor body is monitored indirectly as it is not desirable to have the thermal sensor physically attached to the motor body as this is most often remo-te from circuitry associated with the con-trol of the door or gate opening/closing mechanism and would require additional wires tc carry the required information back -tc the main circuitry. Accordingly the present invention preferably proposes using the thermal sensor in contact with a power supply bridge rec-tifier for the operating motor as the entire motor current mus-t flow -through this bridge rectifier. Consequently it follows -that the temperature of the bridge rec-tifier will rise ln proportion -to -that o~ -the remote operating motor. It is, however, desirable tha-t the thermal inertia of the operating mo-tor and -the bridge rectifier circuit, be perfec-tly matched to achieve optimum results. Simultaneously, the same thermal sensor will also sense ambient temperature changes and consequently compensation is achieved fc,r opera-ting temperatures resulting from both ambient changes and changes due to the operation of the equipment.
A possible alternative location for the thermal sensor could be against a series resistor used tc, monitor the operating motor current. However, this is not quite as good a location as the power supply bridge rectifier circuit as the temperature rise of -the monitoring resistor is much lower than the rectifier circuit where the power developed in heat is much higher.
In accordance with a further preferred embodiment, the first sensor means comprises at least one sensor arrangemen-t adapted -tc sense -the first opera-ting characteristic of said motor at r~pea-ted predetermined time intervals, said circui-t control means including a firs-t circuit operatiny to determine an actual change of the operating characteris-tic over said predetermined time intervals and said first comparitor means including a second circuit operating to compare said change of operating characteris-tic over said prede-termined time intervals with a preset change whereby said ac:tivating signal is generated if said actual change exceeds said preset change. Conveniently -the first sensor means comprises a plurality of said sensor arrangernents each being arranged to sense the opera-ting characteristic at said prede-termined intervals of time, all the sensor arrangements subsequent to a first one of said sensor arrangements commencing their respective prede-termined time intervals within the predetermined time interval of said first sensor arrangement whereby the sensor arrangements are staggered with respect to one another so as to reduce -the response -time required tc activa-te said con-trol arrangement. Preferably the preset change is determined by accumulating incremental changes in -the operating characteristic over a predetermined number of said -time 5 intervals immediately prior to the actual change of the operating characteristic compared at the end of any said time interval.
In some embodiments of this lnvention there is provided inhibitor means arranged -to inhibi-t operation of 10 the control arrangement during an initial time period of each operating cycle.
The present invention will now be described with reference to several preferred embodiments illustrated in the accompanying drawings, in which:
15Figure 1 illustrates typical theore-tical and prac-tical operating characteristics of a door or gate operating mechanisms during both opening and closing cycles of opera-tion;
Figure 2 shows, in block di.agram form, a control arrangement in accordance wi-th a first preferred embodiment of the present invention employing both a dynamic threshold control and a temperature compensated back-up static control;
Figure 3 shows typical circuitry for a temperature compensated static control system;
Figure ~ shows typical circuitry for a dynamic tracking control system;
Figure 5 shows typical circuitry for a control system employing both -temperature compensated static control and dynamic tracking control;
Figure 6 il.lustrates graphically operating characteristics according to the present invention;
Figure 7 shows a circuit diagram illustrating a second preferred embodiment of the presen-t invention;
35Figure 8 illustra-tes graphically the operation of an embodiment of -the type shown in Figure 7;
S~ 3 Figure 9 illustrates graphically -the operation of a control arrangement similar -to figure 7 bu-t incorporating multiple sensors adapted to sense operational characteristic changes o~er predetermined in-tervals with 5 the intervals commencing in staggered time relationship relative to one another; and Figure lO shows graphically a typical operating motor current variation during a door opening cycle with a control arrangement according -tc Figure 7.
Figure 2 of the drawings schema-tically shows in block diagram format a first preferred control arrangement employing two independent control level sensing mGdes of operation. In the drawings M represents the operating motor for a gate or door opening/closing mechanism. Rs is a 15 sensing resistor used to sense load or current drawn by the motor M. LPF represents a filter adapted to pass signals in a low frequency band (typically from 5 to lO Hz) from the sensor Rs to the control circuit. An amplifier A amplifies and transmits -the signal from the low frequency pass filter 20 LPF to a temperature compensated comparitor CA and separately to dynamic tracking controlled comparitor CB
which is adap-ted to compare ra-tes of change of the current drawn by the motor M with a prese-t level. ~aturally, if desired the comparators CA and CB could be used in quite 25 separate control arrangements. Each of the comparitors CA
and CB generate an activating signal in response to the load sensed by Rs exceeding a predetermined limit indicative of the door or gate hitting an obstruction. The activating signals are then combined by an OR gate combiner 30 circuit C and used to either stop or re-verse operation of the motor M. Finally an inhibitor circui-t In is used to inhibit the control circuit for a prede-termined period a-t start up of the operating motor for reasons which will be explained hereinafter.
Typical load operating characteristics of the motor M are shown in the drawings (Figures 1 and 6). Figure ~L~5~ 3 l shows both an opening and a closing characteristic which can be up to 10% difEerent from each o-ther. These graphs show motor current I against time but it will be appreciated that other operating charac-teris-tics might also 5 be employed. I~mediately upon s-tart up -there is a rapid rise in motor current drawn which peaks quickly and se-ttles back almost as quickly into a theoretical substantially uniform load current. The full line graph (a) in Figure l demonstrates a typical theoretical opening and closing load 10 curve against time t. The critical start up period is irrelevant from a safety viewpoint and moreover the high load experienced in this period makes monitoring of the load pointless with regard to safety con-trol. For this reason the inhibitor circuit In is included to override the 15 control circuit for the initial start up period ts. There-after the control circuit becomes effective. In the conventional static control system a constant set point SP
is es-tablished above the theoretical load curve such that if an obs-truction is hit by the door or ga-te, -the load 20 curve rises rcpidly as indicated at (c) and the door or gate is stopped or reversed. However as indicated in the introduction -to this specification, the practical load curve (b) for m~ny reasons will vary considerably from the theoretical curve (a) and it will be obvious from -these 25 graphs that either the se-t point SP must be located tco high for safe operation or the control system will activate itself when there is in fact no obstruc-tion.
According to a preferred aspect of -the present invention it has been recognized tha-t -the rotary ac-tion of 30 the armature of the mo-tor M with the re~sulting commu-tation of the brushes agains-t -the commu-tator give rise -tG finite opening and closing of the motor circui-t a-t a relatively high "chopping" rate. Typically -the frequency of this occurs at around 300 per second but of course this high frequency chopping rate depends on the speed of the motor which is variable. In addition where the primary power source is derived from the 240V main supply there will also ~S~ 3 be high components of 50Hz and lOOHz. I-t is also recognized that frequencies resulting from an obstruc-tion being hit by a door or gate will occur with a relatively well defined low frequency range width (normally within the range of 5 5 to lOHz). In the proposed system the aforementioned chopping high frequency component (and in o-ther higher frequency component) is filtered out leaving only a DC
average and frequency components up to a prede-termined level, typically lOHz. This is achieved by the low 10 frequency pass filter LPF shown in the drawings.
Figure 6 of the drawings illustrates graphically the performance of the control system according to the preferred arrangement of Figure 2. Firstly there is provided a movable constant static set poin-t Ssp. The set 15 point is movable in response to tempera-ture changes arld in particular to both sensed ambien-t temperature changes AHS
and sensed motor temperature changes MHS. If the temperature is generally cold then -the motor is likely to draw more current and thus the set point Ssp is moved 20 upwardly. Conversely if -the temperature is hot the motor is likely to draw less current and the se-t poin-t Ssp will move down. Conveniently both ambient and motor temperature changes can be sensed by single tempera-ture sensing Silicon or Germanium diode Di. The posi-tioning of this diode is conveniently as previously discussed. As shown in Figure 3 the signal from the mo-tor sensing resistor Rs is fil-tered and amplified by an amplifier A and supplied tc one inpu-t terminal of a non inverting voltage comparitor IC2. The temperature sensing diode Di directs its signal tG the o-ther terminal of -the comparitor and in this manner an automatic variation of the set point Ssp is achieved in response to temperature variations. Normally when the static tempera-ture compensated control is being used as back-up in a combined system of the -type shown in Figures 2 and 5, the basic set point wi]l be arranged at a relatively high point such that i-t would only be used should the .,,~ .
.,~ , 12S~ 3 dynamic con-trol fail for whatever reason.
Figure 6 also illustra-tes -the automatic tracking or dynamic threshold capability of the filter Al`F to provide an au-tomatic dynamic se-t poin-t Dsp above the actual 5 load (b) regardless of changes in this load. Thus in the monitoring zone beyond the initial inhibi-t period -ts should an obstruction be hit by the door or gate, the lc,w frequency increase in load is passed by the filter LPF to the control system comprising the tracking filter ATF and 10 the comparitor CB. The load thus follows the curve (c) and the comparitor CB will sense when the load exceeds the dynamic set point Dsp and will send a signal in response thereto -to stop or reverse the motor M.
Suitable circuitry for the automatic -tracking 15 *ilter ATF is shown in Figure 4. This circuit maintains its DC output at Vbb/2 for all input componen-ts up to 5Hz such -that it is not responsive to these components and more particularly maintains its ou-tput at Vbb/2 regardless of the absolute magnitude of the magni-tude of t~]e DC input.
Its response is basically a high pass fil-ter and allows through only those motor "impulse" components within the range SHz tc lOHz.
Experiments have shown tha-t for most applica-tions requiring a motorized door/gate to sense an obstruction, the impulse components predominantly lie within this spectrum. If required the band of interest could be lowered by changing R3/C1 and raised by appropriately decreasing the component values of -the input fil-ter LPF.
The combination R3/C1 gives this filter -the required tracking characteristic in tha-t the voltage across Cl follows (with some -time delay) the input voltage being examined.
The integrated circui-t IC3 arranged in -the manner illustrated is in fact an Inverting Amplifier such that an impulse rising at Vin will cause the outpu-t to fall from i-ts quiescent Vbb/2 level toward ground potential and vice versa. The gain (AC gain) is de-termined by the ratio of the componen-ts R2/Rl. The resistors Rl and R3 should preferably be equal and similarly the resistors R2 and R4 should pre-ferably be equal -to achieve good common 5 mode operation. Should the components no-t be matched in this manner, the outpu-t voltage will not remain itself at Vbb/2 for all input components up to 5Hz and consequently erratic operation could result. Normally components matched within +2% would provide satisfactory operation. The 10 magnitude of the output impulse response has been found to be adequate to trigger the following level compari-tor IC4 of the comparitor circuit CB, if the gain of the integrated circuit IC3 is set within the range of 5 to 10. It is preferred for the capacitor Cl to be a low leakage type 15 whose value could be of the order of 10 microfarad when Rl and R3 are of the order o-f lOOK ohm. The time constant R3Cl is typically 0.1 second but could be lowered -to 0.5 second if required.
Once a sufficiently high impulse component at -the 20 input has been allowed through to the -tracking fil-ter ATF
and consequen-tly causes the output to swing below a predetermined value as set by the comparitor CB, then an overload signal is generated which will stop the motor M.
Subsequently, depending on -the exis-ting motor control 25 logic, either a dwell will resul-t or the motor will be instantly reversed. In either case the ou-tput of the tracking fil-ter ATF will over shoot in the opposite direction, however, this is of no concern to the circuitry as an inhibit signal from the Inhibitor In holds the total 30 response of -t~e control circuitry in an "off" state.
Figure 7 of the accompanying drawings shows a second preferred con-trol arrangement in accordance with the present invention. In this embodiment, -the con-trol arrangemen-t comprises circuitry which monitors -the rate of 35 change of current (i.e. the slope of the current versus time graph) during the opera-tion of opening the door or gate. The measured rcte of change of current is -then compared wi-th a preset rate of change, and if this preset rate of change is exceeded the safe-ty control circuit wil reverse or stop the operation of the motor. Therefore by 5 comparison with a system which requires the mo-tor current to reach a static threshold point, the present system will sense when the motor current is likely to exceed a threshold value thereby allowing much quicker opera-tion of the safety circuit.
Figure 7 of the drawings shows a circuit using a rate of current change measurement method. The curren-t drawn by Motor M is monitored by me~asuring the voltage across a resistor Rs~nse, which is in series with the motor coil. This voltage reading will be proportional to 15 the current being drawn by the mo-tor. This signal is then fed to an amplifier A via a low pass filter LPF. The low pass filter has a cut off frequency typically of 10 Hertz.
The voltage signal is then amplified and inverted and subsequently becomes an input to the comparator. The other 20 voltage input tc -the comparator is generator by an R-C
integrator. Both -the comparator and R-C integra-tor are connected -to a microprocessor at points A and B
respec-tively. Point B provides a pulsed output varying between a logic "high" voltage and a logic "low" voltage.
25 When the output of point B goes high the transistor Q1 is switched on, thereby discharging capacitor Cref. Upon output B going low the transistor Q1 is switched off and a counter internal to the microprocessor is initiated. When the transistor Q1 is switched off the voltage Vr~f 30 increases from a zero value. This rate of increase is Y r~!f ref integrator). The output of the comparator VOUt remains a-t a logic "high" level ur~til V ~f exceeds -the voltage value of the other comparator input, Vin, whereupon VOUt goes 35 to a logic "low" level. When the ou-tput voltage of the comparator, VOUt goes to a logic "low" level, the internal counter of the microprocessor is stopped and the ~2Si~3~3 value of -this counter is -thereby proportional -to the motor current. This count is used as a digital number representing the motor current for tha-t particular measurement interval.
The microprocessor is programmed to calcula-te the actual rate of change of curren-t of the motor M, -to compare this rate of change with a preset rate of change, and to activate the control arrangement of t~le motor M in the case where the actual rate of change of current of the motor M
10 exceeds the prese-t value. The value of the motor current is sampled by the microprocessor at a r2te of 500 Hertz (i.e.
at a 2 msec intervals). Four such motor current samples are accumulated by the microprocessor to obtain an accumulation of current change over those four sample points thereby 15 magnifying and noise averaging the change in current. The microprocessor uses the firs-t sample point as the base value of motor current and to this is added the incremen-t in current that will give the preset ra-te of change. The microprocessor will then compare the actual rate of change 20 with this preset rate of change, and if -the actual rate of change exceeds the preset rate, -the safety control circuits will be activated.
Figure 8 shows a graphical representation of the operating charac-teristics of the con-trol arrangement in 25 accordance with Figure 7. The graph i]lustrates a portion of cycle showing motor current I against time and the slope measurement time intervals as shown on -the graph represent the time intervals in which the rate of change of motor current is de-termined. Each set of four samples are 30 compared with the prese-t rate of change. As shown in this graph when the actual rate of change equals or exceeds the preset overload value during that time interval -the safety control sys-tem is activated. Also shown on this graph are two horizontal lines one representing the average current 35 level and another representing a trip current. The trip current line is positioned at a level equivalent to a ~2S~8~
maximum current which is not to be exceeded by the motor, and is typically the current level used by a safety control system which simply monitors current levels. It can be seen from Figure 8 tha-t the slope comparison technique will 5 enable the safety control circuits within a considerably shorter time that a system using only instantaneous current comparison -techniques.
In order to further reduce the response time of the safety control system, a fur-ther embodimen-t of this 10 invention incorporates a plurality of sensing means which have staggered measurement time intervals. Figure 9 shows a graphical representation similar tc Figure 8 of the operation of such a system. As can be seen from Figure 9 the sensing means circui-ts 1, 2, 3, and 4 are arranged such 15 that they operate in parallel, but have their slope measurement -time intervals staggered in relation to one another, i.e. -the measurement time intervals of circuit 2 commence slightly after circuit 1, -the measuremen-t time intervals of circui-t 3 commence sligh-tly after circuit 2, 20 the measurement time intervals of circuit 4 commence slightly after circuit 3 and at the end of -the circui-t 4 time measuremen-t period, circuit 1 again commences measurement. As can be seen from the graph the current draw of the mo-tor M begins -to be excessive at point A. However, 25 the measurement time intervals of circuit 1 would produce an average curren-t slope less than the required overload slope even though -the measurement -time interval overlaps point A. The same occurs with circuit 2. However circuit 3 includes enough data points to give a measured slope which 30 equals or exceeds -the overload slope and -therefore activates -the safe-ty con-trol c'rcui-t. It can be seen from the graph that if circuit 1 was -the only sensing means being used it would require a further measuremen-t time interval so as to sense the overload slope, and would 35 -therefore result in a significan-t delay in -the activation of the safety control circui-ts. It can be seen therefore, that by using multiple sensing means which have st,aggered ;~ZS18'~3 measurement time intervals, ~the reac-tion time of such a sys-tem can be ~reatly improved.
Figure lO shows a curve of curren-t I vs time t during the opening of a door, and illustrates the variation 5 of the current level during the cycle from closed to open.
It can be seen that part way through the cycle, the current decreases, and in relation to -the trip current level, conventional safety circuit would have an increased response time to an overload or obstruction (and hence 10 force), thereby resulting in poor sensitivity. Superimposed over the current level are a representative sample of preset overload slopes, which show the r~te of current increase required to opera-te the safety control circuits.
The graph demonstrates that this type of system has a 15 constant degree of sensitivity, since the rate of change measuremen-t sys-tem "follows" the current curve providing a dynamic tracking control similar to the embodiment of Figure 2.
The current peak shown in Figure lO results during 20 motor start up. During this period, the safety control circuit is provided with a sensing means to control the operation of the motor and the safety control circuit. This sensing means monitors the rise and fall of the star-t up peak, checking that it both reaches a peak, and falls again 25 to normal opera-ting conditions. If the motor stalls, the current peak will not fall and therefore the safe-ty control circuit will prevent further operation. Also, if as a result of some other failure, the motor fails to start or we have a failure in -the measuring circui-t, then again the 30 safety control circuit will prevent further opera-tion. This will be the case for bo-th directions of operation.
The use of such a system has several advantages over previously used static current sensing means. Because the measurement of curren-t slope is a rela-tive measurement 35 no complicated field adjustment is required upon installation to check and adjus-t set points. The overload .. . .
:~2Sl~
rate of curren-t change c~n be simply programmed into a microprocessor, and the use of such microprocessors will a7so greatly reduce the cost of such a control circuit and allow other functions such as swi-tching, tG be incorporated 5 in its operation. The use of a safety control arrangement which employs a ra-te of current change sensing system means that normal variations in current drawn by -t~'e mo-tor, which result from wind loading or variation in bearing friction, guide effects will nGt result in activation of the safety 10 control circuit, and only those curren-t variations which are excessively high will result in activation of the safety circuit. In addition the use of multiple sensing circuits will result in a very fast response time, where only 0.15 of a second is required to sense and produce 15 action as a result of an overload. Also the overload sensitivity will be -the same for both direc-tions of travel of such a door or gate, the force required to activate the safety circuit will be constant over the full operating range, and -the sys-tem will automa-tically adapt to any 20 number of drive motors used.
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An obstruction control arrangement for a door or gate opening/closing mechanism having an electric operating motor, said control arrangement comprising motor sensor means adapted to sense a first operating characteristic of said motor, circuit control means arranged to determine an operating rate of change of the first operating characteristic sensed by said motor sensor means, first comparitor means arranged to compare said operating rate of change of the operating characteristic with a preset rate of change level, and activating means arranged to stop or reverse said electric motor in response to an activating signal from said comparitor means upon said operating rate of change of the operating characteristic exceeding said preset rate of change level being indicative of said door or gate being obstructed in its normal course of travel.
2. An obstruction control arrangement according to claim 1 further including filter means arranged to pass signals only in a predetermined frequency range from said motor sensor means to the comparitor means.
3. An obstruction control arrangement according to claim 2 wherein the predetermined frequency range is from O
to 10 Hertz.
to 10 Hertz.
4. An obstruction control arrangement according to claim 1 further including a further motor sensor means adapted to sense a second static operating characteristic level of said motor and second comparitor means arranged to compare the sensed static operating characteristic level with a preset static threshold level whereby an activating output signal is generated upon said sensed static operating characteristic level exceeding said preset threshold level and is delivered to said activating means to stop or reverse said electric motor.
5. An obstruction control arrangement according to claim 4 wherein a common motor sensor means is used for said first mentioned and second further motor sensor means such that one operating characteristic of said motor is sensed thereby.
6. An obstruction control arrangement according to claim 4 or 5 further including temperature compensation means arranged to sense operating temperature and to move the preset static threshold level automatically in response to temperature changes.
7. An obstruction control arrangement according to claim 4 or 5 further including temperature compensation means arranged to sense operating temperature and to move the preset static threshold level automatically in response to temperature changes and wherein said temperature compensation means comprises a thermal sensor located in thermal exchange relation with a power supply bridge rectifier for the motor.
8. An obstruction control arrangement according to claim 1 wherein said first mentioned sensor means comprising at least one sensor arrangement adapted to sense the first operating characteristic of said motor at repeated predetermined time intervals, said circuit control means including a first circuit operating to determine an actual change of the operating characteristic over said predetermined time intervals and said first comparitor means including a second circuit operating to compare said change of operating characteristic over said predetermined time intervals with a preset change whereby said activating signal is generated if said actual change exceeds said preset change.
9. An obstruction control arrangement according to claim 8 wherein said first mentioned sensor means comprises a plurality of said sensor arrangements each being arranged to sense the operating characteristic at said predetermined intervals of time, all the sensor arrangements subsequent to a first one of said sensor arrangements commencing their respective predetermined time intervals within the predetermined time interval of said first sensor arrangement whereby the sensor arrangements are staggered with respect to one another so as to reduce the response time required to activate said control arrangement.
10. An obstruction control arrangement according to claim 8 or 9 wherein the preset change is determined by accumulating incremental changes in the operating characteristic over a predetermined number of said time intervals immediately prior to the actual change of the operating characteristic compared at the end of any said time interval.
11. An obstruction control arrangement according to any one of claims 1 to 3 further including inhibitor means arranged to inhibit operation of the control arrangement during an initial time period of each operating cycle.
12. An obstruction control arrangement according to any one of claims 1 to 3 wherein the operating characteristic is current drawn by said motor or a voltage drop characteristic of said motor.
13. An obstruction control arrangement according to claim 2 further including a further motor sensor means adapted to sense a second static operating characteristic level of said motor and second comparitor means arranged to compare the sensed static operating characteristic level with a preset static threshold level whereby an activating output signal is generated upon said sensed static operating characteristic level exceeding said preset threshold level and is delivered to said activating means to stop or reverse said electric motor.
14. An obstruction control arrangement according to claim 3 further including a further motor sensor means adapted to sense a second static operating characteristic level of said motor and second comparitor means arranged to compare the sensed static operating characteristic level with a preset static threshold level whereby an activating output signal is generated upon said sensed static operating characteristic level exceeding said preset threshold level and is delivered to said activating means to stop or reverse said electric motor.
15. An obstruction control arrangement according to claim 13 wherein a common motor sensor means is used for said first mentioned and second further motor sensor means such that one operating characteristic of said motor is sensed thereby.
16. An obstruction control arrangement according to claim 14 wherein a common motor sensor means is used for said first mentioned and second further motor sensor means such that one operating characteristic of said motor is sensed thereby.
17. An obstruction control arrangement according to claim 15 or 16 further including temperature compensation means arranged to sense operating temperature and to move the preset static threshold level automatically in response to temperature changes.
18. An obstruction control arrangement according to claim 2 or 3 wherein said first mentioned sensor means comprising at least one sensor arrangement adapted to sense the first operating characteristic of said motor at repeated predetermined time intervals, said circuit control means including a first circuit operating to determine an actual change of the operating characteristic over said predetermined time intervals and said first comparitor means including a second circuit operating to compare said change of operating characteristic over said predetermined time intervals with a preset change whereby said activating signal is generated if said actual change exceeds said preset change.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPG8291 | 1984-11-26 | ||
| AUPG829184 | 1984-11-26 | ||
| AUPH238285 | 1985-09-11 | ||
| AUPH2382 | 1985-09-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1251843A true CA1251843A (en) | 1989-03-28 |
Family
ID=25642877
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000496197A Expired CA1251843A (en) | 1984-11-26 | 1985-11-26 | Door or gate obstruction control |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4701684A (en) |
| CA (1) | CA1251843A (en) |
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| CA1326280C (en) * | 1987-07-18 | 1994-01-18 | Osamu Yaguchi | Motor-powered opening/closing apparatus for a window or door |
| US4922168A (en) * | 1989-05-01 | 1990-05-01 | Genie Manufacturing, Inc. | Universal door safety system |
| US4924159A (en) * | 1989-06-21 | 1990-05-08 | Ronald Olson | Method and apparatus for remotely reversing electromechanical door openers |
| US5218282A (en) * | 1990-03-22 | 1993-06-08 | Stanley Home Automation | Automatic door operator including electronic travel detection |
| US5351439A (en) * | 1992-04-21 | 1994-10-04 | Koito Manufacturing Co., Ltd. | Power window apparatus having improved safety device |
| US5406179A (en) * | 1993-09-08 | 1995-04-11 | Techstrip, Inc. | Garage door edge electrical interface |
| US5625980A (en) * | 1993-09-15 | 1997-05-06 | Rmt Associates | Garage door opener with remote safety sensors |
| US5493812A (en) * | 1993-09-15 | 1996-02-27 | Rmt Associates | ge door opener with remote safety sensors |
| US5596840A (en) * | 1993-09-15 | 1997-01-28 | Rmt Associates, Inc. | Garage door opener with remote safety sensors |
| US5543692A (en) * | 1994-05-28 | 1996-08-06 | Trw Inc. | Method and apparatus for controlling an electric motor for moving a member |
| US5729104A (en) * | 1994-12-02 | 1998-03-17 | Nissan Motor Co., Ltd. | Power window apparatus for vehicle |
| USRE38400E1 (en) * | 1995-02-06 | 2004-01-27 | Daimlerchrysler Corporation | Control function-power operated lift gate |
| DE69633324T2 (en) * | 1995-06-06 | 2005-09-15 | The Chamberlain Group, Inc., Elmhurst | MOVABLE BARRIER OPERATING DEVICE WITH LEARNING FOR POWER AND POSITION |
| FR2741651B1 (en) * | 1995-11-23 | 1999-09-10 | Rohee Rene Denis Georges | DEVICE FOR AUTOMATIC STOPPING AND SYNCHRONIZATION OF SWING SHUTTERS MOTORIZED ON OPENING AND CLOSING |
| US5929580A (en) * | 1997-08-05 | 1999-07-27 | Wayne-Dalton Corp. | System and related methods for detecting an obstruction in the path of a garage door controlled by an open-loop operator |
| GB9821674D0 (en) * | 1998-10-05 | 1998-12-02 | Intellitec Mv Ltd | Ramp |
| US6326751B1 (en) | 1999-08-25 | 2001-12-04 | Wayne-Dalton Corp. | System and related methods for detecting and measuring the operational parameters of a garage door utilizing a lift cable system |
| US20010042820A1 (en) * | 2000-01-04 | 2001-11-22 | Wilson Robert H. | Optoelectronic system for an automatic vehicle door closure |
| US6936984B2 (en) | 2000-08-28 | 2005-08-30 | Lear Corporation | Method and system for detecting the position of a power window of a vehicle |
| DE60141595D1 (en) * | 2000-09-18 | 2010-04-29 | Telair Int Ab | METHOD AND DEVICE FOR CONTROLLING THE OPERATION OF AN OPERATING UNIT |
| US6407522B1 (en) | 2000-09-18 | 2002-06-18 | Telair International Ab | Method and a device for controlling the operation of an actuator unit |
| US6870334B2 (en) * | 2002-12-31 | 2005-03-22 | The Chamberlain Group, Inc. | Movable barrier operator auto-force setting method and apparatus |
| GB2446315B (en) * | 2004-01-06 | 2008-10-08 | Chamberlain Group Inc | Movable barrier operator auto force setting method and apparatus |
| US6943511B2 (en) * | 2004-02-09 | 2005-09-13 | Mechanical Ingenuity Corp | Electronic industrial motor operator control system |
| JP2006064594A (en) * | 2004-08-27 | 2006-03-09 | Aisin Seiki Co Ltd | Pinching detection device |
| US8675838B2 (en) * | 2006-10-02 | 2014-03-18 | The Chamberlain Group, Inc. | Intercom unit for providing a status alert for a movable barrier |
| US7548036B2 (en) * | 2006-10-10 | 2009-06-16 | Square D Company | DC motor mechanical shock protection system |
| KR101545022B1 (en) * | 2008-11-14 | 2015-08-17 | 엘지전자 주식회사 | Ice making device and method for controlling the same |
| US8375635B2 (en) | 2009-08-26 | 2013-02-19 | Richard Hellinga | Apparatus for opening and closing overhead sectional doors |
| US8690027B2 (en) * | 2012-06-14 | 2014-04-08 | General Electric Company | Ice dispenser duct door motor with adjustable drive |
| EP2865629B1 (en) * | 2013-10-24 | 2016-11-30 | Kone Corporation | Stall condition detection |
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| GB1395749A (en) * | 1972-06-05 | 1975-05-29 | Westinghouse Brake & Signal | Controlling the operation of a door |
| NL7711968A (en) * | 1977-10-31 | 1979-05-02 | Antonius Franciscus Huitink | SAFETY CIRCUIT FOR CONSTANT SPEED ELECTRIC MOTOR DRIVEN SHUT-OFF DEVICE SUCH AS A WINDOW, A DOOR, A VALVE ETC. |
| DE2756972A1 (en) * | 1977-12-21 | 1979-06-28 | Daimler Benz Ag | PROCEDURE FOR OPERATING SERVO OPERATED LOCKING DEVICES |
| US4234833A (en) * | 1978-01-19 | 1980-11-18 | A. E. Moore Company, Inc. | Door operator system using counter circuit for determining limit positions |
| US4220900A (en) * | 1978-06-16 | 1980-09-02 | Sky-Top Sunroofs Ltd. | Motor control system for a linearly reciprocating load device such as automotive vehicle closure including sun roof |
| DE2926938A1 (en) * | 1979-07-04 | 1981-01-22 | Rau Swf Autozubehoer | SWITCHING ARRANGEMENT FOR DRIVING A MOVABLE ELEMENT, ESPECIALLY FOR DRIVING DISCS OR THE LIKE. IN MOTOR VEHICLES |
| JPS56123783A (en) * | 1980-02-29 | 1981-09-29 | Nippon Denso Co Ltd | Control unit for load driving |
| DE3034118C2 (en) * | 1980-09-11 | 1983-12-29 | Fa. Leopold Kostal, 5880 Lüdenscheid | Process for the electronic monitoring of the opening and closing process of electrically operated units |
| DE3226614A1 (en) * | 1982-07-16 | 1984-01-19 | Robert Bosch Gmbh, 7000 Stuttgart | CIRCUIT ARRANGEMENT FOR INPUTING AND EXTENDING A MOTOR-DRIVEN ANTENNA |
| US4563623A (en) * | 1982-08-23 | 1986-01-07 | Hitachi, Ltd. | Motor speed control apparatus |
| ZA847740B (en) * | 1983-10-12 | 1985-05-29 | Byrne & Davidson Ind Ltd | Obstruction detection means |
| JPS6149086A (en) * | 1984-08-14 | 1986-03-10 | アルプス電気株式会社 | Automatic rising falling apparatus of window glass |
-
1985
- 1985-11-26 CA CA000496197A patent/CA1251843A/en not_active Expired
- 1985-11-26 US US06/801,956 patent/US4701684A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| US4701684A (en) | 1987-10-20 |
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