GB2235170A - Control arrangement for a motor vehicle - Google Patents

Abstract

A control system is provided for a motor vehicle comprising an accelerator pedal and an automatic control such as a wheel slip detector. Means are provided for selectively connecting either a first controlling member 8 operated by the accelerator pedal or a second controlling member 9 actuated by the automatic control to a controlled element 5 which determines the position of the throttle. The arrangement is such that the controlling member which is tending to move the control element furthest towards the right is connected to the controlled element with the other controlling member then being disconnected from the controlled element. <IMAGE>

Description

DESCRIPTION OF INVENTION Improvements in or relating to a control arrangement THE PRESENT INVENTION relates to a control arrangement and more particularly relates to a control arrangement in which the position of a controlled element which is movable between a first position and a second position is to be controlled by two controlling members each capable of moving the controlled element between the two terminal positions, the arrangement being such that the controlled element is maintained at the position which is closest to one of the terminal postions as dictated by either of the controlling members.

Such a control system may be utilised, for example, in a so-called "cruise-control" for a motor vehicle. In such a cruise control, the degree of throttle opening is controlled by a foot-operated accelerator pedal, and the degree of throttle opening is also controlled by a control arrangement which is adapted to ensure that the speed of the vehicle is maintained as close as possible to a predetermined value which may, for example, be 70 kilometres per hour. In operation of such a device, when a person is driving the car and the cruise control is activated, the cruise control opens the throttle so that the car travels at 70 kilometres per hour without the accelerator pedal being depressed at all. If the accelerator pedal is pressed, the cruise control can be over-ridden causing the car to go faster than 70 kilometres per hour.Thus, in the cruise control arrangement the throttle, which is normally biassed to be closed, is opened against the bias to the greatest extent dictated by either the cruise control, or the accelerator pedal. Such an arrangement is relatively easy to engineer.

It is desirable to provide an arrangement in which the throttle is opened against the bias by the lesser extent is dictated by a control arrangement or the accelerator pedal, and the present invention seeks to provide such a device.

According to this invention there is provided a control system comprising a controlled element adapted to be moved between a first terminal position and a second terminal position, the controlled element being biassed towards the first terminal position, a first controlling member adapted to be moved between a first terminal position and a second terminal position while effecting a corresponding movement of the controlled element, and a second controlling member also movable between a first terminal position and a second terminal position, again effecting a control over the controlled element, means being provided for selectively connecting either the first controlling member or the second controlling member to the controlled element, the means being adapted so that it is the controlling member which is tending to move the controlled element towards the first terminal position which is connected to the controlled element by the connecting means, with the other controlling member then being operatively disconnected from the controlled element.

Preferably the controlled element presents two opposed planar faces, and each controlling member presents a planar face which is in contact with or biassed towards a respective one of the planar faces of the controlled element, the said connecting means comprising means adapted to project from a planar face or planar faces and co-operating recess means in the opposed planar face or faces adapted to receive the projecting means.

Conveniently the or each recess has one abrupt edge and one inclined edge.

Advantageously the controlling members are spring-biassed towards the controlled element.

Conveniently the controlled element defines two opposed said recesses therein, each controlling member having a projection adapted to be received within a corresponding recess of the controlled element, comprising said projecting means.

Preferably the controlled element has means adapted to project from the opposed faces thereof, each controlling member defining at least one said recess in the planar face thereof abutting the controlled element.

Advantageously the controlled element is provided with a projection formed integrally therewith which projects from the two opposed planar faces thereof.

In one embodiment the controlled element has an aperture therein receiving a movable element which can move to project beyond the two opposed planar faces thereof.

Preferably the movable element is a freely mounted movable element.

Conveniently the movable element comprises a ball.

Alternatively the movable element comprises a plug.

In another embodiment the movable element consists of a pivotally mounted movable element.

Preferably the controlled element and the controlling members are all in the form of plate-like elements which are movable relatively to one another longitudinally with the plane of the planar elements, the controlling members being on opposed sides of the controlled element.

Conveniently the controlled element and the two controlling members are mounted for relative rotational movement about a common axis.

Advantageously means are provided for adjusting the position of the first controlling member and the second controlling member in response to commands or signals from two different sources.

Preferably one of the controlling members is adapted to be positioned by means of a manual control or a foot control.

Conveniently the second controlling member is adapted to be positioned mechanically, hydraulically, pneumatically or electrically.

Advantageously the controlled element is adapted to operate a throttle on a motor vehicle engine.

Preferably the second controlling member is adapted to be controlled in response to signals derived from a wheel-spin sensor.

Alternatively the second controlling member is adapted to be moved in response to signals from a system responsive to the speed of the motor vehicle.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which FIGURE 1 is a diagrammatic sectional view through the components of one embodiment of the invention, FIGURES 2 and 3 are views corresponding to Figure 1 illustrating the components in different relative positions, FIGURE 4 is a corresponding view of another embodiment of the invention, FIGURE 5 is a view corresponding to Figure 4 showing that embodiment with the components thereof in a different condition, FIGURE 6 is a diagrammatic view of yet another embodiment of the invention, FIGURE 7 is a view corresponding to Figure 6 showing the components of the embodiment illustrated therein in a different condition, FIGURE 8 is a diagrammatic view of yet another embodiment of the invention, FIGURE 9 is a diagrammatic view of a further embodiment of the invention, FIGURE 10 is an elevational view of an alternative embodiment of the invention, FIGURE 11 is an exploded view of some of the components of the embodiment as illustrated in Figure 10, FIGURE 12 is a sectional view of that part of the embodiment of Figure 10 as illustrated in Figure 11 in one condition, and FIGURE 13 is a view corresponding to Figure 12 showing the illustrated components in another condition.

Referring now to the drawings, Figure 1 is a diagrammatic view illustrating one embodiment of the invention.

The control system illustrated in Figure 1 may be considered to be a control system such as a control provided on a motor vehicle to prevent wheels-pin occurring. The control arrangement is adapted to control the position of a throttle linkage 1 which is movable between two terminal positions as indicated by the line 2. The throttle linkage 1 is biassed towards the right, (or the closed position of the throttle) as indicated by arrow 3, by means of an appropriate spring 4.

The throttle linkage is connected to a controlled element 5 in the form of an elongate plate, having two opposed substantially planar faces. Formed within the plate 5 is an aperture 6, of circular form, and retained within the aperture is a ball 7 having a diameter which is less than the diameter of the aperture 6, but which is greater than the thickness of the plate. Thus the ball projects beyond the plate.

Located on one side of the plate 5 is first controlling member 8, and located on the other side of the plate 5 is a second controlling member 9. The controlling members 8 and 9 are each of plate-like form, each presenting a planar face which is directed towards a respective one of the planar faces of the controlled element 5. Thus the controlling members 8 and 9 are sandwiched together with the controlled element 5. An appropriate housing or the like may be provided to retain the elements together in a "sandwich" form, while still permitting relative axial movement of the elements, as will be described hereinafter. Springs or other resilient means are provided to bias the controlling members 8 and 9 towards the controlled element 5. The controlling members 8 and 9 may move slightly away from the controlled element 5.

The controlling member 8 has a recess 10 formed in the surface thereof which abuts the controlled element 5, and similarly the controlling member 9 has a recess 11 therein in the face thereof abutting the controlled element 5. Each recess is of non-symmetrical form. Each recess has an abrupt leading edge 12,13, towards the left as shown in Figure 1 and an oblique or inclined trailing edge 14,15, towards the right as shown in Figure 1. The abrupt edge forms an abutment to engage the ball 7 as will be described, and the oblique or inclined edge is intended to be rolled across by the ball.

Each of the controlling members 8 and 9 are provided with a mechanism, schematically indicated at 16,17 adapted to impart respective forces to the con trolling members 8 and 9 to move the controlling members each controlling member being movable between two terminal positions as indicated by the lines 18 and 19.

It is envisaged that one controlling member 8 may be controlled by means of a first operated pedal, such as an accelerator pedal, whereas the second controlling member 9 may be electronically controlled by a device which senses wheel-spin. However, in alternative embodiments of the invention the controlling members may be hydraulically or pneumatically moved by appropriate mechanisms. Also, whilst the controlled element 5 has been shown as being connected directly to the throttle linkage 1, the connection between the controlled element and the throttle linkage may be electronic, hydraulic or pneumatic.

It is to be appreciated that in an initial condition of the control system, as illustrated in Figure 1, the ball 7 will be received partly within the aperture 6 and partly within the recess 10 formed in the first controlling member 8. The recess 11 in the second controlling member 9 will not be aligned with the ball 6. Thus, a flat part of the upper surface of the second controlling member 9 will help keep the ball 7 in an elevated position, so that the upper part of the ball is contained within the recess 10.

The lower controlling member 9 will normally be positioned as far as possible to the left as illustrated in Figure 1 when the apparatus is in an initial condition.

When the driver of the car operates the accelerator pedal, a force is applied, by the mechanism schematically illustrated at 16, to move the upper controlling member 8 towards the left. The ball 7 is thus moved towards the left, consequently moving the con trolled element 5 to the left, thus moving the throttle linkage 1 to the left, opening the throttle. Should a condition of wheel-spin be detected, the lower controlling member 9 will be moved by the mechanism schematically illustrated at 17 from its initial position towards the right as shown in Figure 1. When the recess 11 is co-aligned with the recess 10 the ball 7 will tend to fall, as illustrated in Figure 2, so that the lower part of the ball is located within the recess 11.

The lower controlling member 9 will also move towards the controlled element 5 under the spring bias applied thereto, so that the relevant flat faces of the controlling member 9 and the controlled element 5 abut.

The abrupt edge 13 of the recess 11 will thus engage the ball. As the controlling member 9 continues to move towards the right, the upper part of the ball 6 will slide or roll along the oblique edge 14 of the recess 10 in the upper controlling member 8, forcing that controlling member 8 slightly away from the controlled element 5 against a spring bias imparted thereto, as illustrated in Figure 3.

It will be observed that the lower controlling member 9 now effectively dictates the position of the controlled element 5. Thus, if the lower controlling member 9 continues to move towards the right as illustrated in Figure 3, under the influence of signals provided from the sensor which senses wheel-spin, until such time that wheel-spin no longer exists, the controlled element 5 moves the same way, thus closing the throttle. Once the wheel-spin condition has terminated, the controlling member 9 may move towards the right, until again the apparatus is in the condition illustrated in Figure 2.If the controlling member 9 then continues to move further towards the right the ball 6 will engage the oblique trailing edge 15 of the recess 11 and, as the lower controlling member 9 continues to move towards the right the ball 7 will rise up until it is again in a condition as illustrated in Figure 1.

It is then again the mechanism 16 that determines the position of the controlled element 5 and thus the position of the throttle linkage 1.

In the embodiment described, it will be appreciated that the degree of opening of the throttle is always dictated by the controlling member 8 or 9 which is towards the right as shown in Figure 1. In other words the degree of opening of the throttle is always dictated by the controlling member which requires the minimum opening of the throttle.

Whilst in the embodiment described above the second controlling member is associated with a mechanism 17 which is responsive to a sensed wheel-spin, the mechanism 17 might equally be a controller mechanism responsive to the speed of the vehicle and provided to ensure that the vehicle does not exceed a predetermined speed.

It will be appreciated that in the embodiment illustrated in Figures 1 to 3 the two controlling members 8 and 9 are biassed towards the controlled element 5 by means of springs or the like (not shown) to enable the ball 7 to operate in the manner described.

Figure 4 illustrates the essential components of an alternative embodiment of the invention which in many respects closely resemble the components of the first described embodiment of the invention. In the embodiment of Figure 4 the controlled element 25 which corresponds with the controlled element 5 of Figures 1 to 3 has an aperture 26 therein, this aperture accommodating a plug 27 having a cylindrical lower portion and a dome-shaped hemi-spherical upper portion. A first controlling member 28 which engages the upper surface of the control element 25 has a recess 30 therein which receives the dome-shaped part of the plug 27. The recess 30 has an abrupt leading edge 32 and an oblique trailing edge 34. A second controlling member 29 has a recess 31 therein, the recess accommodating a helical compression spring 33.

When the plug 27 is in the position illustrated in Figure 4, the dome-shaped portion of the plug 27 is received within the recess 30 and thus as the first controlling member 28 (which corresponds with the controlling member 8 of the embodiment of Figures 1 to 3) moves, so the control element 5 moves. However, when the plug 27 is brought into alignment with the recess 31, if the upper controlling member 28 tends to move towards the left as illustrated in Figure 4 (or if the lower controlling member 29 tends to move towards the right) the dome-shaped part of the plug 27 will move along the inclined trailing edge 34 of the recess 30, thus forcing the lower part of the plug 27 into the recess 31, compressing the spring 33.When the plug 27 has been forced downwardly in this way the control system has the condition illustrated in Figure 5, and it will then be appreciated that the position of the controlled element 25 is dictated by the position of the lower controlling member 29.

Thus, effectively, the apparatus of Figure 4 and 5 will operate in the same way as the apparatus of Figures 1 to 3, but there is no need to spring bias the controlling members 8 and 9 towards the controlled element 5.

Figure 6 illustrates a modified embodiment of the invention, illustrating a controlled element 45 and controlling members 48 and 49 having recesses 50 and 51 therein. The embodiment, as thus far described, thus corresponds precisely with the embodiment of Figures 1 to 3. However, instead of the controlled element having an aperture therein accommodating a ball, the controlled element is formed with enlarged protrusion 46 of generally spherically form, protruding on the two opposed sides of the plate-like controlled element 45. This protrusion 46 acts in the same manner as the ball 7 of the embodiment of Figure 1, being selectively received within the recess 50 or the recess 51. The recesses 50 and 51 have abrupt edges and oblique edges, in just the same way as the recesses 10 and 11 have abrupt edges and oblique edges.Thus the embodiment of Figure 6 and 7 will operate in the same way as the embodiment of Figures 1 to 3.

Figure 8 illustrates another embodiment which has certain similarities to the embodiment of Figure 6 and 7. In this embodiment the controlled element 55 defines, on its two opposed faces, two recesses 54 which, in this embodiment, are inthe form of a through-aperture. Each of the recesses has an abrupt edge 56 and an oblique edge 57. Each of the controlling members 58,59 which are spring-biassed into contact with the controlled element 55, has a projection or protrusion 60,61 thereon of dome-shaped or hemi-spherical form which can be introduced into the recesses 54 formed in the controlled element 55. It will be appreciated that with the projection 60 of the upper controlling member 58 inserted into the recess 54, the position of the upper controlling member 58 will dicatate the position of the controlled element 55.However, when the projection 60 is brought into alignment with the projection 61, then the projection 61 will also be inserted into the recess 54. If the controlling member 59 then moves towards the right as indicated in Figure 8 the projection 60 will slide up the inclined edge 57 of the recess 54, and then the position of the controlled element 55 will be dictated by the position of the controlling member 59.

It will therefore be appreciated that this embodiment again operates in a very similar manner to that described above with reference to earlier-described embodiments.

Figure 9 illustrates another embodiment of the invention in which the controlled element 75 has pivotally connected to it, by means of a horizontal pivot axis 76 a mass 77 presenting two diverging linear sides 78,79 and an arcuate inter-connecting side 80, the pivot axis 76 being remote from the arcuate side 80.

The mass 77 is retained within an appropriate aperture 81 formed within the controlled element 75 with the first axis extending transverely to the line of movement of the controlled element 75. The controlling members 82,83 are provided each with a recess therein. The recess 84 in the lower controlling member 83 has an abrupt edge 85 and an oblique edge 86 and the recess 87 formed in the upper controlling member 82 is of a similar configuration. In this embodiment the controlled element 75 is biassed towards the right by means of a spring 88 and the upper controlling member 82 is biassed towards the right by means of a spring 89. The controlling members 82 and 83 are spring-biassed towards the controlled element 75.

In the initial position illustrated the mass 77 has the lower linear edge 78 thereof engaging the upper planar surface of the lower controlling member 83. The upper part of the mass 77 is thus received within the recess 87, with the linear edge 89 abutting the inclined edge of the recess and with the arcuate edge 80 engaging the abrupt edge. As the upper con trolling member 82 is moved towards the left or the right, so the controlled element is moved to the left or right. If the mass 77 is brought into alignment with the recess 84, the mass 77 will pivot downwardly so that at least part is within the recess 84. The dimension of the arcuate part is such that when the mass is fully within the recess 84 the upper-most part of the arcuate part 80 still projects above the upper surface of the controlled element 75.

If the lower controlling member 83 then moves towards the right as shown in Figure 9, the linear side 79 of the mass 77 will slide down the inclined face of the recess 87, thus forcing the upper controlling member 82 slightly away from the controlled element 75 against the spring bias, and the lower part of the mass 77 will be firmly engaged within the recess 84.

Thus the position of the controlling member 83 will dictate the position of the controlled element 75. If the controlling member 83 then moves again towards the left as shown in Figure 9 until the recesses 84 and 87 are again brought into alignment, the upper-most part of the arcuate edge 80 will be received partly within the recess 87. If the upper controlling member 82 then moves towards the right, since the upper part of the arcuate face 80 engages the abrupt edge of the recess 87, the mass 77, together with the controlled element 75 will be moved towards the right. The linear edge 78 of the mass 77 will then ride up the oblique or inclined face 86 of the recess 84, thus returning the apparatus to the condition illustrated in Figure 9.

Whilst, in the embodiments described above, springs have been utilised to impart a bias to certain elements, other means may be utilised to impart such a bias.

The embodiments described above have all involved a linear relative movement between the controlled element and the controlling members. It is, however, to be appreciated that an alternative embodiment of the invention may be a rotary embodiment as will now be described.

Referring now to Figure 10 of the accompanying drawings a cable 90 is connected to a foot-operated accelerator pedal, and is adapted to rotate a first controlling member 91 in the form of a wheel or disc, to which the cable 90 is attached. Adjacent the first controlling member 91 is a controlled element 92 in the form of a wheel or disc of corresponding diameter. A cable 93 mounted on and attached to the controlled element 92 extends to a throttle linkage. A second controlling member, which is not visible in Figure 10, is mounted concentrically within the controlled element 92, and is driven by means of a shaft coming from a motor 95. The motor 95 is controlled by means of a control arrangement 96 which receives signals from a driven wheel 97 and from a non-driven wheel 98 in order to determine when wheel-slip or wheel-spin is occurring.The arrangement is such that when wheel-slip or wheel-spin is occurring the motor 95 is actuated to move the second controlling member, to adjust the position of the controlled element 92 to reduce the opening of the throttle, so that the wheel-spin is terminated.

Figure 11 illustrates the various components present in the assembly of Figure 10 with greater clarity. A fixed shaft 94 of generally cylindrical form, has, at one end, a portion 99 of narrower diameter having a circumferential groove 100. Various components to be described are rotatably mounted on the shaft 94. Mounted on the shaft 94 is a spring-plate 101 which serves to bias, towards the left, a switch-wheel 102. The switch-wheel 102 has a peripheral flange 103 which extends towards the right and thus defines, within the switch-wheel 102 a cavity. The spring-plate 101 is located within the cavity and serves to bias the switch-wheel 102 towards the second controlling member 104.The second controlling member 104 consists of a disc or plate 105 provided with an axially extending boss 106 which extends towards the right terminating in a splined portion 107 which accepts a drive from the motor 95. The plate 105 has recesses 108 therein at diametrically opposed positions. The switch wheel 102 is mounted on the portion 107 and is rotatable with the second controlling member 104.

The control element 92 is in the form of a disc-like wheel having a central aperture 109 to enable the wheel to be rotatably mounted on the shaft 94 and a peripheral groove 110 adapted to receive the cable 93.

Two diametrically opposed apertures 111 are formed within the controlled element 92 which receive two balls 112, the axes of the apertures being parallel with the axis defined by the shaft 94 The first controlling member 91 is again in the form of a disc-like wheel having a central through-bore to enable the wheel to be rotatably mounted on the shaft 94 and also having two diametrically opposed recesses 114 in the face thereof which is adjacent the controlled element 92. A peripheral groove 115 is provided to accommodate the cable 90.

Also mounted on the shaft 94, in a non-rotatable manner is a fastening element 116 which is fixed in position and which is secured to one end of a spiral spring 117, the other end of which is connected to an axially extending flange 118 provided on the first controlling member 91. The spring 117 thus serves to im part a bias to the first controlling member 91. A further spring-plate 118 is also mounted on the shaft to engage the first controlling member 91 and impart a spring bias thereto. The spring plate 118 is retained in position by means of a circlip 119 which engages the groove 100 provided on the shaft 94.

Figures 12 and 13 illustrate the components of Figure 11 when in the assembled state. Figures 12 and 13 illustrate various features present on the components of Figure 11 which are not clearly visible from Figure 11. For example, it is to be noted that the switch-wheel 102 is adapted to rotate with the second controlling member 104. The switch-wheel 102 has an axially extending peg 120 which passes through one of the apertures 108 formed in the second controlling member 104. The switch-plate 102 has the flange 103 thereof aligned with a micro-switch 121 and, when in the condition illustrated in Figure 13, serves to actuate the micro-switch.

The micro-switch 121 is mounted on a fixed plate 122 which carries two arc-shaped potentiometer tracks 123 which are shorted out by brushes 124 carried on a plate 125 which is mounted to co-rotate with the second controlling member 104. Thus the position of the second controlling member can be determined.

In operation of the embodiment illustrated in Figures 10 to 13, initially the second controlling member 104 is so located that a planar part of the leading face thereof is aligned with the apertures 111 formed in the controlled element 92, thus forcing the balls 112 towards the right so that the balls engage with the recesses 114 formed in the first controlling member 91.

It will be appreciated that when the apparatus is in this condition, movement of the cable 90, in response to operation of the accelerator pedal, will cause a rotation of the first controlling member 91, and a directly equivalent rotation of the controlled element 92 will occur, thus causing an equivalent movement in the cable 93 that is connected to the throttle. As in the previously described embodiments each of the recesses 114 will have an abrupt leading edge and inclined trailing edge, thus serving to bias the balls 112 towards the right as illustrated. If a wheel-spin is detected, the second controlling member will be rotated, being rotated in an anti-clockwise sense as viewed in Figure 11.The recesses 108 therein will become aligned with the recesses 111, and the balls will then move to the condition illustrated in Figure 13, with the balls engaged in the apertures 111 and also engaging the recesses 108. As the recess 108 is engaged, so the switch-wheel 102 is moved towards the right, thus activating the micro-switch. The operative part of each recess 108 will again have an abrupt edge and an inclined edge to perform a function equivalent to that performed by the recesses in the embodiments described above.

Whilst the invention has been described with reference to various embodiments in which balls are utilised which engage recesses which have an abrupt edge and an inclined or oblique edge, it is to be appreciated that all of these embodiments may be modified to utilise, instead of the balls, plugs or equivalent transversely movable elements, which may be mounted on appropriate guides to ensure that the elements moved in the intended manner, with the elements presenting an abrupt leading edge and an inclined trailing edge. Thus the operative part of each of these elements may have a substantially triangular form.

While the invention has been described in the context of a vehicle, and with regard to a control system to limit wheel-spin, it is to be understood that the invention may find other different applications, for example, in controlling the winding gear of a crane, where the speed of winding may have to be restricted in dependence of the magnitude and the moment of the load.

Claims (27)

CLAIMS:

1. A control system comprising a controlled element adapted to be moved between a first terminal position and a second terminal position, the controlled element being biassed towards the first terminal position, a first controlling member adapted to be moved between a first terminal position and a second terminal position while effecting a corresponding movement of the controlled element, and a second controlling member also movable between a first terminal position and a second terminal position, again effecting a control over the controlled element, means being provided for selectively connecting either the first controlling member or the second controlling member to the controlled element, the means being adapted so that it is the controlling member which is tending to move the controlled element towards the first terminal position which is connected to the controlled element by the connecting means, with the other controlling member then being operatively disconnected from the controlled element.

2. A control system according to Claim 1 wherein the controlled element presents two opposed planar faces, and each controlling member presents a planar face which is in contact with or biassed towards a respective one of the planar faces of the controlled element, the said connecting means comprising means adapted to project from a planar face or planar faces and co-operating recess means in the opposed planar face or faces adapted to receive the projecting means.

3. A control system according to Claim 2 wherein the or each recess has one abrupt edge and one inclined edge.

4. A control system according to Claim 2 or 3 wherein the controlling members are spring-biassed towards the controlled element.

5. A control system according to any one of Claims 2 to 4 wherein the controlled element defines two opposed said recesses therein, each controlling member having a projection adapted to be received within a corresponding recess of the controlled element, comprising said projecting means.

6. A control system according to any one of Claims 2 to 4 wherein the controlled element has means adapted to project from the opposed faces thereof, each controlling member defining at least one said recess in the planar face thereof abutting the controlled element.

7. A control system according to Claim 6 wherein the controlled element is provided with a projection formed integrally therewith which projects from the two opposed planar faces thereof.

8. A control system according to Claim 6 wherein the controlled element has an aperture therein receiving a movable element which can move to project beyond the two opposed planar faces thereof.

9. A control system according to Claim 8 wherein the movable element is a freely mounted movable element.

10. A control system according to Claim 9 wherein the movable element comprises a ball.

11. A control system according to Claim 9 wherein the movable element comprises a plug.

12. A control system according to Claim 8 wherein the movable element consists of a pivotally mounted movable element.

13. A control system according to any one of the preceding Claims wherein the controlled element and the controlling members are all in the form of plate-like elements which are movable relatively to one another longitudinally with the plane of the planar elements, the controlling members being on opposed sides of the controlled element.

14. A control system according to any one of Claims 1 to 12 wherein the controlled element and the two controlling members are mounted for relative rotational movement about a common axis.

15. A control system according to any one of the preceding Claims wherein means are provided for adjusting the position of the first controlling member and the second controlling member in response to commands or signals from two different sources.

16. A control system according to Claim 15 wherein one of the controlling members is adapted to be positioned by means of a manual control or a foot control.

17. A control system according to Claim 16 wherein the second controlling member is adapted to be positioned mechanically, hydraulically, pneumatically or electrically.

18. A control system according to any one of Claims 1 to 17 wherein the controlled element is adapted to operate a throttle on a motor vehicle engine.

19. A control system according to Claim 18 wherein the second controlling member is adapted to be con trolled in response to signals derived from a wheel-spin sensor.

20. A control system according to Claim 18 wherein the second controlling member is adapted to be moved in response to signals from a system responsive to the speed of the motor vehicle.

21. A control system substantially as herein described with reference to and as shown in Figures 1 to 3 of the accompanying drawings.

22. A control system substantially as herein described with reference to and as shown in Figures 4 and 5 of the accompanying drawings.

23. A control system substantially as herein described with reference to and as shown in Figures 6 and 7 of the accompanying drawings.

24. A control system substantially as herein described with reference to and as shown in Figure 8 of the accompanying drawings.

25. A control system substantially as herein described with reference to and as shown in Figure 9 of the accompanying drawings.

26. A control system substantially as herein described with reference to and as shown in Figures 10 to 13 of the accompanying drawings.

27. Any novel feature or combination of features disclosed herein.