US 3708029 A
An automatic steering mechanism for mounting on a steerable vehicle to guide it along a slot in a track has a feeler mounted forwardly of the front wheels of the vehicle to engage in and sense the position of the slot. Movements of the feeler laterally with respect to the vehicle are transmitted through a system of incompressible links to control an hydraulic ram. The ram movement is damped and applied to the track rod of the vehicle.
Description (OCR text may contain errors)
United States Patent m1 [111 3,708,029
Sedgfield et al. Jan. 2, 1973 s41 SYSTEM FOR GUIDING VEHICLES 2,925,875 2/1960 Bourdon 104/247 lnventors: B-
late of Esher, Ekstrom i England; Norman Kenneth Brown 3,393,762 7/1968 Matson Bmfield; Eric James m FOREIGN PATENTS 0R APPLICATIONS Bracknell, both of England 299,756 10 1928 G t8 '1: ..l80 79 73 Assignee: Sperry Rand Limited, London, En- I gland Primary Examiner-Kenneth H. Betts  Filed: Feb. 16, 1970 Assistant Examiner-John A. Pekar [211 App]. No; 11,637 Attorney-S. C. Yeaton 30 F A H P"  ABSTRACT orei ti 't D ta gn pp ca on on y a An automatic steering mechanism for mounting on a Feb. l5, 1969 Great Britain ..8,344/69 steerable vehicle to guide it along a Iot in a tragk has a feeler mounted forwardly of the front wheels of the g 3$; vehicle to engage in and sense the position of the slot. I? Movements of the feeler lateral), with respect to the  Field of Search ..l80/79; l04/244.l, 247 vehicle are transmitted through a system of incmm pressible links to control an hydraulic ram. The ram  References cued movement is clamped and applied to the track rod of UNITED STATES PATENTS the vehicle 3,492,949 2 1970 Brown ..l04/244.l 15 Claims, 6 Drawing Figures PATENTED 2 m 3,708,029
SHEET 1 OF 4 INVENTORS HUGH B. SEDGF/ELD NORMA/V A. BROWN ERIC J. B/RCH/VALL ATTORNEY INVENTOES HUGH B. SEDGF/ELD NORMA/V K. BROWN ER/C J. B/RCH/VALL B) SHEET 2 [IF 4 PATENTEDJAM 2197s SHEET t [1F 4 PATENTEU JAN 2 975 I/VE/VTORS HUGH B. SEDGF/ELD NORMAN K. BROWN ER/C K B/RCH/VALL ATTORNEY SYSTEM FOR GUIDING VEHICLES CROSS-REFERENCES TO RELATED APPLICATIONS matic guidance using an electrical control circuit. The 0 present invention is both simpler and more reliable than the prior one.
BACKGROUND OF THE INVENTION The invention relates to methods of automatically guiding steerable vehicles along a track.
It has been desired for many years to dispense with manual steering of vehicles and many systems have been proposed including the basic system used in the present invention of following a guide slot by a feeler sliding in the slot. However all prior systems have only been capable of use at very slow speeds.
This invention relates to a system for guiding vehicles along a track. More particularly the invention relates to an automatic steering mechanism carried by the vehicle arranged to co-operate with a guide slot in the track.
The invention provides an automatic steering mechanism for mounting on a steerable vehicle to guide it along a guide slot in a track, said mechanism comprising a feeler for entering the guide slot and sensing its lateral position relative to the vehicle, an arm extending forwardly of the mechanism and carrying said feeler at its forward end so that in use the feeler is in advance of the front wheels of the vehicle, a mounting for the rear end of said arm allowing the arm freedom about a vertical axis, auxiliary power means adapted for connection to drive steering gear of the vehicle, and a system of incompressible links linking movement of said arm about said vertical axis to control said auxiliary power means in the sense that, in use, lateral displacement of said vehicle from a predetermined position relative to the guide slotresults in a steering adjustment tending to restore said predetermined position.
It has been found that if the automatic steering mechanism is to steer a road vehicle at the relatively high speeds, e.g. 50 to 70 m.p.h., of whichthe vehicle may be capable, then certain criteria must be fulfilled.
Firstly there must be a measure of anticipation of required steering adjustments so that the steering correction, which inevitably takes a finite time to achieve, is effected in time and the vehicle follows a pursuit course. With the steering arrangement of the specific embodiment it is found that a satisfactory degree of'anticipation is secured by positioning the sensing feeler about inches in advance of the axis of the front steering wheels of the vehicle. This allows smooth steering without setting up oscillations, at speeds up to m.p.h. The second criterion is that the feeler must not bear heavily against the sidesof the slot since this reduces the sensitivity of the error sensing. It follows that the feeler movement should not in normal operation be used directly to effect steering corrections, and in the present embodiment the feeler movement is used to control an hydraulic valve which supplies the power necessary to adjust the steering wheels. The third criterion is that there must be minimum play in any linkage through which the error signal is transmitted. Excessive play in the linkage would be likely to mean that an oscillatory path would be followed by the vehicle. According to the present embodiment therefore the error signal is applied to the hydraulic valve through a system of rigid (i.e. incompressible) links with minimum free play therebetween.
The specific embodiment of the invention is now described in detail, with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic plan layout (not to scale) of an automatic steering mechanism,
FIG. la is a side view of a follower arm of FIG. 1,
FIG. 2 is a detail to scale of the connections of the automatic steering mechanism to the track rod steering of a vehicle,
FIG. 3 is a detail to scale of the follower arm and follower lifting gear of FIGS. 1 and In,
FIG. 4 is a plan view of the follower arm and lifting gear of FIG. 3, and
FIG. 5 is a detail to scale of follower pin erecting gear of FIGS. 1 and 1a.
- Referring first to FIGS. 1 and In for a brief description of the overall system, the front wheels 11 of a vehicle which travels in the direction of arrow A are shown with their conventional associated steering track rod 12 connected to be manually steered through a drag link 13. Provision is also made for automatic steering through a linkage which comprises track rod link 15 connected to track rod 12 by means shown in FIG. 2, output lever 16, clutch l7 and actuator lever 18. Clutch 17 comprises a dog clutch which is manually operated by cable l9'by, the driver of the vehicle. When the driver wishes to steer manually therefore he disengages the clutch 17.
A mechanical signal for controlling the automatic steering is derived from a follower pin or feeler 21, which depends from the vehicle and engages in a guide slot (not shown) formed in the roadway along whichthe vehicle travels. The pin and slot are described in more detail in our U.S. Pat. No. 3,492,949, Steering Vehicles Along A Track issued Feb. 3, 1970 and in British Pat. 1,151,932 System For Controlling a Vehicle by H. Sedgfield, published May 14, 1969. The pin is mounted at the lower end of an aluminum follower arm 22, 50 inches long, which'points forward and down from a pivotal mounting 23 which gives the arm freedom to pivot abouta horizontalaxis so that the pin can be raised by a lifting mechanism 24 for operation of the vehicle on a normal roadway without automatic steering. Mounting 23 itself is mounted to be pivotal about a verticalaxis a few inches in front of the wheel axis of the vehicle and is connected to rotate an input lever 25. The end of input lever 25 is pinnedat 27't0 a valve operating-lever 28, which positions the spool of an hydraulic valve 29 controlling a ram 30. The movement of the ram 30 in turn operates the linkage describedabove to effect a steering'adjustment. A pair of centering and bias springs 32normally operate to tend to maintain the lever 25 and arm 22 in a central:
position. If, however, the slot in which pin 21 is running departs from a central position in front of the vehicle, as when achange in direction of the guide slot occurs or when the vehicle wanders with respect to the slot,
then the pin 21 moves in a horizontal plane relative to the vehicle, so causing mounting 23 and levers 25 and 28 to rotate. A steering adjustment in the sense to return the vehicle to a central position relative to the slot is therefore made. As can best be seen in FIG. 1, pin 21 is about 55 inches in advance of the wheels 11, so that the need for a steering adjustment is detected before the wheels reach the point at which the pin detected the requirement. The angle through which the arm 22 moves when sensing an error is approximately equal to the angle through which the wheels 11 are adjusted.
Valve operating lever 28 has an extension from pin 27 which is secured to a collar 99 which in turn is fixedly secured on a rod 53. Rod 53 is slidably mounted in extensions of the body of ram and has one end secured to the piston of a stationary dashpot 54. A pair of springs 55 surround the rod 53 and act between the collar 99 and the ram extensions.
If the mechanical signal from the arm 22 is followed exactly by the steering gear, it is found that lateral accelerations of a level which might cause some passenger discomfort can be demanded at speeds of 60 m.p.h. In order to avoid this, the springs 55 and dashpot 54 in conjunction with the geometry of the mounting of lever 28 afford a measure of phase advance compensation which modifies the relationship between the follower arm signal and the consequent change in steering wheel angle.
When a steering adjustment is called for by movement of input lever 25, pivot point 27 is moved thereby. The dashpot 54 resists movement of the collar 99 via the rod 53 upon movement of the lever 25. Additionally, the springs 55 are substantially incompressible by the force applied to the lever 28 and therefore assist in preventing movement of the collar 99 with respect to the ram body 30. Thus the lever 28 pivots about its mounting in the collar 99 to open the valve 29. This causes the ram body 30 to move in the appropriate direction so beginning a steering adjustment. The ram 30 moving in the appropriate direction compresses one of the springs 55 which in turn reacts on the collar 99 and hence the dashpot 54. The resultant movement of the dashpot 54 moves the rod 53, the collar 99 and the lever 28 in a sense to close the valve thereby backingoff the operation of the ram 30. The springs 55 and the dashpot 54 thus act to introduce a delay in this backing-off of the input originally applied to the valve 29 and provide the required phase advance compensation referred to above. Thus it will be appreciated that the dashpot 54 provides the necessary initial resistance to movement of the collar 99 when a steering change is first commanded and subsequently assists in delaying the backing-off of the command signal, i.e. in providing the phase advance compensation, in conjunction with the springs 55. The motion of the ram body 30, therefore, is controlled to prevent any sudden steering adjustment. Moreover, the motion of the ram body 30 applying the force through the springs 55, move the collar 99 whereby the lever 28 is pivoted to a position in which the valve 29 is partially closed.
The ram comes to rest at a position where the road wheels are steered by the required amount, the valve spool remaining open sufficiently to maintain the ram holding the wheels in this position. A stable response which gives a smooth passenger ride is thereby established Turning to a more detailed description of the parts of the system, FIG. 2 shows the connection of the automatic steering lever 16 to the conventional track rod 12 of the vehicle. A short track rod link 15 is used connected pivotally at one end to the lever 16 and at the other end pivotally to the center point of the track rod 12. Both pivotal connections are made by l-inch diameter balls 35, 35' carried on tapers which fit into corresponding tapered openings in lever 16 and track rod 12. Should the arm 22 become seriously damaged, e.g. bent in operation, an electrically operated quick release mechanism schematically illustrated at 100 causes ball 35 to be sheared from its taper thereby interrupting the drive from the arm to the steering gear.
FIGS. 3 and 4 show in more detail part of the follower arm 22 and the lifting gear 24 which have the same reference numerals as in FIGS. 1 and la. Main chassis members 36 and front axle members 36' of the vehicle on which the automatic steering system is mounted are also shown.
The lifting gear comprises a pair of levers 37 spaced apart along a shaft 43, and joined at their ends by bar 45. A fixed beam of the chassis carries a pair of brackets 39 in which the shaft 43 is mounted with freedom to rotate therein. Near one end shaft 43 carries a pulley 38 keyed thereto, which pulley has a V- section groove around its circumference. A pair of operating cables 40, extend in opposite senses around the V groove and are secured by a clamp 44 at their ends. The free ends of the cables extend to the drivers cab where by pulling cable 40 the driver causes pulley 38 to rotate anticlockwise as viewed in FIG. 3, and so turns levers 37. As best seen from FIGS. la and 4, this causes bar 45 to engage the follower arm 22 to lift the arm and pin 21 to a retracted position shown in dotted lines in FIG. la. When the driver pulls the other cable 40' the levers 37 rotate in the clockwise sense to return the follower arm to the operative position.
Levers 37 are each formed in two parts one capable of pivotal motion relative to the other and spring maintains the two parts normally aligned. Since the arm 22 is mounted on a member of the front axle assembly and the lifting gear 24' on the chassis, some differential motion takes place due to motion of the chassis springs. This motion is allowed for by the spring 50'.
As best seen in FIG. la, the pin 21 is rotated to lie horizontally when the arm is in its retracted position and FIG. 5 shows in more detail the arrangements for effecting this rotation. The pin 21 and arm 22 are shown in the operative position. Pin 21 is carried on a lever 48 which is pivotally mounted to rotate about a horizontal axis 47 at the end of arm 22.0ne end of lever 48 is urged by a coil spring 50 in the anticlockwise sense as viewed in FIG. 5, while the other end has a cable 51 attached thereto. The cable 51 extends between the lever 48 and the pulley 38 (FIG. 3) of the lifting gear 24. When the pulley 38 is rotated in the sense to lift arm 22, cable 51 is pulled thereby so as to rotate lever 48 against the force of spring 50 until the pin lies parallel to arm 22. When the pulley 38 is rotated in the opposite sense, cable 51 is released and spring 50 returns the pin to the operative position.
When the vehicle reaches a junction in the track at which a choice of two routes is available, the choise is determined by the driver of the vehicle prior to reaching the junction. The driver operates cable 58 so as to cause springs 32 to be displaced in the sense to apply a torque to the lever 25 and arm 22 causing the pin to be bias urged against one side or the other of the guide slot. When a junction of two guide slots is reached therefore the pin follows the side of the guide slot against which it is urged and so enters the guide slot on that side. The centring and bias springs 32 are relatively light springs; in normal unbiassed operation of the system the pin experiences a resistance to movement of less than 1 oz per inch, while in biassed operation the pin is urged against the side of the slot with a pressure of about ozs.
It will be particularly noted that the linkage between pin 21 and the valve 29 consists of rigid levers linked together with minimum play being allowed at the links so as to reduce the dead movements of the linkage to a minimum. No compressible members e.g. springs are included in the operating linkage.
Should the hydraulic actuator 30 fail, due for instance to a failure of the hydraulic pressure supply, a link 52 from pin 27 to actuator lever 18 ensures the continued operation of the automatic steering by direct drive from the pin 21 to the steering linkage. In normal usage this link is redundant, and is connected with sufficient end play (about 0.02 inches) to ensure that the normal ram output movement does not affect it. In these circumstances, of course, the side pressure on the pin will be severe, the characteristics of the control would deteriorate, speed would have to be decreased to about 20 mph. for comfort, and the wear on the pin will be increased. However, the failure of the actuator v does not result in total loss of automatic steering ability.
As seen best in FIG. 5, the pin 21 comprises a tubular base on which a wear-resistance ceramic outer coating 56 of titania alumina is formed. A collar 57 prevents the pin from dropping too far into the guide slot. The mounting on lever 48 allows the pin to rotate slowly while running on the side of the guide slot, so as to reduce the effects of wear.
- Varios electrical sensing switches (not shown) sense theposition of the movable parts of the system, and operate indicators in the drivers cab to show that the system is operating properly.
Although the above describedembodiment of the invention was explained in terms of a forwardly extending arm 22, it may alternatively be desirable for certain applications to mount the arm 22 in a rearwardly extending direction. This may be accomplished by positioning the mounting 23 on the vehicle chassis in advance of the steering wheelssuch that the entire arm 22 and the feeler 21 is extending rearwardly from the mounting 23 but located forward of the steering wheel axle.
What is claimed is:
1. An automatic steering mechanism for mounting on a steerable vehicle to guide it along a guide slot in a track, said mechanism comprising:
a. a feeler for entering the guide slot and sensing its lateral position relative to the vehicle,
b. an arm extending from the mechanism and carrying said feeler at one end thereof,
trol element in normal automatic steering opera tion for linking movement of said arm about said vertical axis to control said auxiliary power means.
2. An automatic steering mechanism as claimed in claim 1, wherein said auxiliary power means is an hydraulic ram having mechanical linkage for driving said steering gear, and a control valve connected to said system of incompressible links.
3. An automatic steering mechanism as claimed in claim 2 further including a quick-release mechanism for severing said mechanical linkage thereby disconnecting said hydraulic ram from said steering gear.
4. An automatic steering mechanism as claimed in claim 3 in which said mechanical linkage includes links and a ball and taper pin, said ball being connected in one of said links and said taper being connected in another of said links, and
said quick-release mechanism includes means for shearing said ball from said taper.
5. An automatic steering mechanism as claimed in claim 2 including feedback means for applying a feedback movement from the output of the auxiliary power means to the systemof mechanical links comprising resilient means connecting said hydraulic ram to said mechanical links in a manner tending to close said control valve in response to the steering movement of said hydraulic ram.
6. An automatic steering mechanism as claimed in claim 5 in which said resilient means comprises spring means resiliently coupling said hydraulic ram to said mechanical links, and
further including mechanical damping means coupled to said mechanical links,
said spring means and said damping means being so constructed and arranged with respect to said mechanical links that said feedback movement from said auxiliary power means to the system of mechanical links is initially resisted, thereby providing phase advance compensation.
7. An automatic steering mechanism as claimed in claim 1, further including mechanical means for applying a feedback movement from the output of the auxiliary power means to the system of mechanical links.
8. An automatic steering mechanism as claimed in claim 1 in which I said arm extends forwardly of said mechanism and carries said feeler at its forward end, and
said mounting being at the rear end of said arm.
9. An automatic steering mechanism as claimed in claim 1 further including mechanical coupling means for mechanically coupling said links to said steering gear to maintain control of said vehicle in the event of failure of said steering mechanism.
10. An automatic steering mechanism for mounting on a steerable vehicle to guide it along-a guide slot in a track, said mechanism comprising:
a. an arm extending from the mechanism,
said feeler being mounted at the forward end of said arm.
14. A vehicle having steering gear connected to steerable wheels and automatic means for controlling b. a mounting at one end of the arm allowing said said steering gear to guide the vehicle along a guide slot arm freedom for pivoting movement about vertical and horizontal axes,
. means engaging said arm for lifting it about its horizontal axis to an inoperative position,
. a feeler mounted at the opposite end of said arm,
. auxiliary power means for connection to drive the steering gear of the vehicle,
. said auxiliary power means including a power control element, and
. a system of rigid, mechanical links having substantially no free play mechanically connecting said arm only to said power control element in normal automatic steering operation for linking movement of said arm about said vertical axis to control said auxiliary power means.
11. An automatic steering mechanism as claimed in claim 10, wherein said feeler comprises a pin pivotable about a horizontal axis at said opposite end of the arm, and wherein there is provided means for rotating said pin between a vertical, operative position and an inoperative position parallel to the arm when said engaging means lifts said arm to said inoperative position.
12. An automatic steering mechanism as claimed in claim 10, wherein said feeler comprises a pin mounted with freedom for rotation about its axis and having a wear-resistant outer surface.
13. An automatic steering mechanism as claimed in claim 10 in which said arm extends forwardly of said mechanism,
said mounting being at the rear end of said arm, and
in a track, said automatic means comprising:
a. an arm extending longitudinally and downwardly from forward of the steering wheels,
. a feeler mounted at one end of said arm for entering said guide slot and sensing its lateral position relative to the vehicle,
. a mounting at the opposite end of said arm secured to the vehicle and providing freedom for said arm about a vertical axis,
. a system of substantially incompressible mechanical links having substantially no free play con- V nected to said arm,
. auxiliary power means connected to be controlled by said system of mechanical links and to drive said steering gear in the sense to maintain the vehicle in a predetermined position relative to the guide slot, 1 said auxiliary power means including a power control element, and i said system of mechanical links mechanically connecting said arm only to said power control element in normal automatic steering operation for linking movement of said arm about said vertical axis to control said auxiliary power means.
15 The vehicle as claimed in claim 14 in which said arm extends forwardly and downwardly from adjacent the steering wheels, said feeler being mounted at the forward end of said arm, and said mounting being at the rear end of said arm.