merited using digital and integrated circuit technology DUAL-MOTOR CONTROL APPARATUS and is advantageously software programmable.
DESCRIPTION BRIEF DESCRIPTION OF THE DRAWINGS
1. Technical Field 5 For a better understanding of the present dual motor This invention relates generally to motor control control apparatus, reference may be made to the accom
apparatus and, more particularly, to apparatus for regu- panying drawings in which:
lating the supply of power to a pair of independently FI<J-1 is a schematized top view of a vehicle incor
controlled vehicle drive motors. porating the present invention;
2. Background Art 10 FIGS. 2A and 2B are block diagrams of one embodiSeveral classes of powered vehicles incorporate a ment of the present dual motor control apparatus;
plurality of independently controllable drive motors. FIG. 3 illustrates pulse trains associated with certain
For example, many types of electric vehicles include operational modes of the apparatus diagrammed in FIG.
two drive wheels, each of the drive wheels being driven 2;
independently by an associated motor. A control circuit 15 FIGS. 4A and 4B are block diagrams of an alternative
is employed to regulate the supply of electrical power embodiment of the present invention; and,
to the motors and, thus, the speed of the driven wheels. FIG. 5 is a flowchart of the software for an embodi
To drive the vehicle in a straight path, the same ment of the present invention, power is supplied to each of the drive motors under
control of the control circuit. These motors thus oper- 20 BEST MODE FOR CARRYING OUT THE
ate at the same speed to drive the respective wheels at INVENTION
the same speed. When the vehicle is traversing a curved Fig. 1 shows a vehicle control system 16 having a
path, the inner wheel must rotate slower than the outer control circuit 10 for independently controlling the
wheel. Therefore, the control circuit controls the sup- suppiy of electrical power to first and second electric
ply of power to the drive motors and makes the speed of 25 drfve ... n u M Qne example> the vehide contfol
the motor driving the inner wheel slower than the speed system 16 controls m electric vehicle 18 having a first
of the motor driving the outer wheel. As the radius of driye whed 20 ^ a second drive wheel n The first
the curved path is made progressively smaller the speed motQr n rotates the first drfve whed 20 th h a first
differential between the inner and outer wheels be- shaft u &nd the second motor 14 rotates the second
comes progressively greater culminating in the extreme 30 ^ ^ ^ h ^ ^
case in which the inner and outer wheels are counter ... ., . ,, . . , ,.
The vehicle control system 16 includes a direction
v ■ t i • v. u J1J4. switch 33 having forward, reverse, and neutral switch
Existing control circuits have been developed to , TM_ , , .
control the supply of power to dual motors. A disad- command, P^ons. The con rol circuit 10 receives vantage common to these control circuits is that they 35 command direction input signals in response to any one are based upon out-dated, linear or analog design con- P°^10n the direction switch via an associated line 31. cepts. Moreover, existing multiple motor controls typi- The vehl°le contro1 svstem 16 als° lncludes an accrd" cally include dedicated logic circuitry. Consequently, erator Pedal 28 that can be Positioned at any one of a the motor speed control functions cannot be easily var- plurality of positions, each representing a desired or ied or tailored to, for example, supply appropriate 40 command motor speed. The control circuit 10 receives power to different rated motors for different sized vehi- command speed input signals in response to any one cles position of the accelerator pedal 28 via an associated
The present invention is directed to overcoming one line 30- Tile vehicle control system 16 also includes a or more of the problems as set forth above. steerable wheel 35 associated with a steering wheel 32.
45 The steerable wheel 35 rotates through a plurality of DISCLOSURE OF THE INVENTION angular positions in response to rotation of the steering
In one aspect of the present invention, a vehicle con- wheel 32 to steer the vehicle 18 along a straight or trol system for controlling first and second power curved path. Signals corresponding to any one of the switching means for coupling power to first and second rotational or angular positions of the steerable wheel 35 respective drive motors includes first and second con- 50 are delivered to the control circuit 10 via an associated trollable means for controllably operating the first and line 34.
second power switching means and first and second In response to the vehicle 18 being driven along a transducer means for generating first and second com- straight path, the first drive motor 12 and the second mand motor speed signals. The improvement comprises drive motor 14 are supplied with equivalent mean first means for generating first digital numbers in re- 55 power and driven at the same speed to rotate the wheels sponse to the first command motor speed signals, sec- 20,22 at the same speeds. Conversely, in response to the ond means for generating second digital numbers in vehicle 18 being driven along a curved path, differential response to the second command motor speed signals, mean power is supplied to the first drive motor 12 and and means for generating first and second pulse trains in the second drive motor 14 to rotate the inner one of the response to the respective first and second digital num- 60 first and second wheels 20,22 slower than the outer one bers and for delivering the pulse trains to the first and of the first and second wheels 20,22; inner and outer in second controllable means. this case referring to the relative position of the wheels
Prior control circuits do not offer the advantages of 20,22 with respect to the center of the radius of the arc the present vehicle control system and are implemented described by the curved path, the inner one of the essentially as linear or analog circuits which inherently 65 wheels 20,22 being nearer the center than the outer one are not as reliable, cost-effective, fast and space-saving of the wheels 20,22.
as are digital and integrated circuits. The control appa- FIG. 2 further illustrates the apparatus or control ratus of the present invention is designed and imple- circuit 10 for controlling the supply of electrical power