GB2063788A - Vehicle steering control system - Google Patents

Abstract

A steering system for a vehicle has an optical control apparatus for controlling the steering of the wheels or tracks, the optical control apparatus being profiled optically so that, in the turn, the steerable wheels or tracks are steered around a common center. Control valves 17A, 17B, 17C, 17D supplying pressure fluid to hydraulic cylinders for turning the individual wheels or tracks are actuated by separate outputs derived from a steering lever 50 through movable windows 37, 38, 39 of varying opacity interposed between light sources 31, 32, 33 and optical sensors 34, 35, 36, summing junctions 41, 42, 43, 44 receiving signals from the optical sensors and from feedback potentiometers 19A, 19B, 19C, 19D coupled to the wheels or tracks, and amplifiers 46, 47, 48, 49. <IMAGE>

Description

SPECIFICATION Vehicle steering control system This invention relates to steering of wheeled or tracked vehicles and, in particular, to insuring that each of the wheels or tracks are steered about a common center when it is desired to turn the vehicle.

The conventional method of steering the ground engagement means, which may be the tracks or wheels of a vehicle, over different radii, but where the radii have a common center or intersection point, is to use tie rods interconnecting the wheels or tracks of the vehicle. However, there are many types of vehicles which do not permit the use of mechanical linkages for making these adjustments. For example, gantry cranes are built with a clearance between the wheels upon which the crane is propelled so that the crane may bridge the articles which it is transporting. Tie rods would interfere with the operation of the crane insofar as they would make it impossible for the crane to move over these articles.The present invention is particularly useful, therefore, on those vehicles where the tie rods are inappropriate to the proper functioning or ultilization of the vehicle. Moreover, the present invention allows a much more flexible arrangement for providing the tie rod function without using the mechanical tie rods which are subject to the normal difficulties associated with mechanical arrangements.

According to the invention, there is provided a steering system for a vehicle, the vehicle having two steerable ground engagement means, one on each side of the vehicle, said steering system comprising steering control means adapted to steer said two steerable ground engagement means; and optical control means connected to said steering control means, said optical control means being optically profiled so that, in a turn, both said two steerable ground engagement means are steered about a common center.

An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic circuit drawing of a vehicle steering system in accordance with the present invention; Figure 2 is a detailed drawing showing the contents of the control apparatus of the system shown in Fig. 1; and, Figures 3 and 4 show the vehicle turning counter-clockwise and clockwise respectively wherein the wheels or tracks of the vehicle have common centers of turning.

In Fig. 1, vehicle 10 has four steerable ground engagement means, which may be tracks or wheels, 1 1 A to 1 1 D, for steering and driving the vehicle 10 along its direction of travel. Each of the ground engagement means 11 A to 11 D is steerable about a re- spective vertical axis 12A to 12D and has associated therewith respective gears 13A to 13D which, together with corresponding racks 14A to 14D turn ground engagement means 11 A to 11 D around their axes 12A to 12D.

Racks 14A to 14D are extensions of pistons 15A to 15D contained within hydraulic motors or cylinders 16A to 16D. Pistons 15A to 15D are moved by the hydraulic pressure differential across these pistons within cylinders 16A to 16D. This hydraulic pressure is supplied by respective pilot valves 17A to 17D each of which is controlled by an output from controller 30. Each valve 17A to 17D is supplied with hydraulic fluid from pump 18.

To insure that each piston 15A to 15D is in its proper linear orientation, each piston is connected to a wiper arm of corresponding potentiometers 19A to 19D. These wiper arms provide separate electrical inputs to controller 30 as shown.

Controller 30 is shown in more detail in Fig. 2 and includes a plurality of iights 31 to 33 forming a light source. Optical sensor 34 cooperates with light source 31, sensor 35 cooperates with light source 32 and sensor 36 cooperates with light source 33. Each of the sensors provides an output the magnitude of which will depend upon the amount of light received from corresponding light sources 31 to 33. Mounted between each light source and its corresponding sensor is a variable transmissive window 37, 38 and 39 having an optical profile selected to steer the wheel associated therewith about the desired radius depending upon the direction of turn. Sensor 34 is connected to one input of each of summing junctions 41 and 42.Summing junction 41 receives a second input from the wiper arm of feedback potentiometer 19B and summing junction 42 receives a second input from the wiper arm of feedback potentiometer 19D. Sensor 36 is connected to summing junctions 43 and 44. Summing junction 43 receives a second input from the wiper arm of feedback potentiometer 19A and summing junction 44 receives a second input from the wiper arm of feedback potentiometer 19C.

The output of summing junction 41 is connected to the negative input of amplifier 46 whereas the output from summing junction 42 is connected to the positive input of amplifier 47. This arrangement is desired in order to produce the opposite steering affect on the wheels of one side of the vehicle. For example, when it is desired to turn left, ground engagement means 11 A and 11 B are rotated counter-clockwise but ground engagement means 11 C and 11 D are rotated clockwise.

Such opposite action between 11 A to 11 B and 11 C to 11 D is assured since the output from sensor 34 is connected to opposite inputs of its associated amplifiers and the output from sensor 36 is connected to opposite inputs of its associated amplifiers. As shown, the output from summing junction 43 is connected to the negative input of amplifier 48 and the output from summing junction 44 is connected to the positive input of amplifier 49.

Variable light transmissive windows 37, 38 and 39 are all mechanically connected together to be operated by a steering lever 50.

The arrangement of light sources 31 to 33, light sensors 34 to 36 and windows 37 to 39 together with the control handle 50 may take the general form shown in our copending U.S. Patent Application No. 910,043. The optical control handle disclosed therein may be easily modified for providing a third variably light transmissive window to form the reference sensor as disclosed herein and for insuring that all windows are simultaneously active rather than separately active as shown in that application. The reference sensor 35 is connected to the second or other inputs of amplifiers 46 to 49. Window 38 may be profiled as desired so that temperature effects on sensors 34 to 36 are minimized or may be eliminated with the other inputs of amplifiers 46 to 49 connected to an appropriate resistance bridge for providing corresponding set points.

As shown in Fig. 3, a left hand turn results in ground engagement means 11 A and 11 B being rotated or steered counterclockwise and ground engagement means 11 C: and 11 D being rotated or steered clockwise. However, the center of rotation of wheels 11 A and 11 c must be the same as the center of rotation of 11 B and 11 D to prevent skidding of either the inside or outside ground engagement means. This common center is represented by point F in Fig. 3. In a right hand turn, just the opposite action must be taken such that the ground engagement means 11 A and 11C must have the same center of rotation as the ground engagement means 11 B and 11 D.

This point is represented by point G in Fig. 4.

When the vehicle is to be turned into a left hand turn as shown in Fig. 3, steering lever 50 is operated to increase the opacity of window 37 between source 31 and sensor 34 while at the same time decreasing the opacity between light source 33 and sensor 36. Thus, the output from sensor 34 decreases while the output from sensor 36 increases. A decreasing output from sensor 34 will result in an increasing output from amplifier 46 and a decreasing output from amplifier 47. An increasing output from sensor 36 results in a decreasing output from amplifier 48 and an increasing output from amplifier 49. Valve 1 7B is connected to cylinder 16B in such a manner that an increasing output from amplifier 46 will drive rack 1 4B in a direction to rotate ground engagement means 11 D in a counter-clockwise direction.Likewise, valve 17D is connected to cylinder 16D in such a manner that a decreasing output from amplifier 47 drives rack 1 4D in a direction to rotate ground engagement means 11 D in a clockwise direction. Valve 1 7A and 17C are similarly arranged for providing similar rotation of ground engagement means 11A and 11C as shown in Fig. 3.

As rack 1 4B moves in a direction to rotate ground engagement means 11 B in a counterclockwise direction, the signal on wiper arm potentiometer 1 9B increases to balance the decreasing input to summing junction 41.

Similarly, the decreasing input to summing junction 42 from light sensor 34 is balanced by an increasing signal from the wiper arm of potentiometer 19 D. The increasing inputs to summing junctions 43 and 44 from light sensor 36 are balanced by corresponding decreasing inputs from the feedback potentiometers 1 9A and 19C.

As shown in Fig. 2, the opacity of the variable light transmissive windows 37 and 39 vary from dark at one end of the window to light at the other end of the window. The gradation of change between light and dark is selected to give the desired steering rotation of ground engagement means 11 A to 11 D depending upon the sharpness of the turn to be made. Specifically, points F and G will vary, although they will remain the common center point for all ground engagement means, depending upon the sharpness of the turn. The profile or gradation of the variable light transmissive windows 37 and 39 is selected to provide the common steering center movable dependent upon the sharpness of the turn. The variable light transmissive window 38 may be uniform from one end to the other to provide the desired reference to am amplifiers 46 to 49 but may be varied in order to characterize the turn as desired. Instead of the reference light source 32, the reference light sensor 35 and the reference light transmissive window 38, the second inputs to amplifiers 46 to 49 may be connected to an appropriate resistance bridge.

Claims (11)

1. A steering system for a vehicle, the vehicle having two steerable ground engagement means, one on each side of the vehicle, said steering system comprising steering control means adapted to steer said two steerable ground engagement means; and optical control means connected to said steering control means, said optical control means being optically profiled so that, in a turn, both said two steerable ground engagement means are steered about a common center.

2. A system of Claim 1, wherein said optical control means comprises a light source, a light sensor and light control means interposed between said light source and said light sensor, said light sensor being connected to said steering control means, said light control means being profiled with variable opacity such that, in a turn, both said two steerable ground engagement means are steered around a common center.

3. The system of Claim 2, wherein said light control means includes at least one variable light transmissive window.

4. The system of Claim 3, wherein said light sensor includes first and second sensors, said first sensor being associated with a first variable light transmissive window and said second sensor being associated with a second variable light transmissive window, said first sensor being connected to said steering control means for controlling one of said two steerable ground engagement means and said second sensor being connected to said steering control means for controlling the other said two steerable ground engagement means, said first and second variable light transmissive windows being profiled so that, in a turn, both said two steerable ground engagement means are steered around a common center.

5. The system of Claim 4, wherein said steering control means comprises first and second amplifiers, said first amplifier being connected to the output of said first sensor and said second amplifier being connected to the output of said second sensor, the outputs of the amplifiers being applied to the pilot valves of the piston and cylinder units of respective steering control means.

6. The system of Claim 5, including a first summing junction having a first input connected to said first sensor and a second second input connected to a feed-back potentiometer which senses the turning of one of said two ground engagement means, said second summing junction having a first input connected to said second sensor and a second input connected to a feedback potentiometer for sensing the turning of said other of said two steerable ground engagement means.

7. The system of Claim 5 or 6, wherein said first and second amplifiers have a second input each, said second input of each being connected to a third sensor having a third reference variable light transmissive window operated in conjunction with said first and second variable light tranmissive windows and controlling the light falling on said third sensor from said light source.

8. The system of Claims 5 6 or 7, wherein the vehicle includes a further two steerable ground engagement means, and wherein said first sensor is connected to said steering control means for controlling said front and back, right steerable ground engagement means and said second sensor is connected to said steering control means for controlling said front and back, left steerable ground engagement means, said first and second variable light transmissive windows being profiled so that, in a turn, said front and back, right and left steerable ground engagement means are steered around a common center.

9. The system of Claim 8 as appendant to Claim 5, 6 or 7, wherein said steering control means includes third and fourth amplifiers, said first and third amplifiers being connected to the output of said first sensor and said second and fourth amplifiers being connected to the output of said second sensor.

10. The system of Claim 9 as appendant to Claim 8, including third and fourth summing junctions, said first summing junction having a first input connected to said first sensor, a second input connected to a feedback potentiometer which senses the turning of said front, right steerable ground engagement means, and an output connected to one input of said first amplifier, said third summing junction having a first input connected to said first sensor, a second input connected to a potetiometer for sensing the turning of said back, right steerable ground engagement means and an output connected to one input of said third amplifier, said second summing junction having a first input connected to said second sensor, a second input connected to a feedback potentiometer which senses the turning of said left, front steerable ground engagement means, and an output connected to one input of said second amplifier, and said fourth summing junction having a first input connected to said second sensor, a second input connected to a feedback potentiometer which senses the turning of said left, back steerable ground engagement means, and an output connected to one input of said fourth amplifier.

11. The system of Claim 9 or 10, wherein said first, second, third and fourth amplifiers have a second input each, said second input of each being connected to a third sensor having a third reference variable light transmissive window operated in conjunction with said first and second variable light transmissive windows and controlling the light falling on said third sensor from said light source means.