CA2074593A1 - Vehicle steering control device - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

To enable a vehicle to be equipped with a single air-bag arranged, when it is not inflated, in a housing extending over the entire width of the vehicle's dashboard and which protects both the driver and a passenger sitting beside him in the event of an accident, the vehicle's steering control device comprises a hand-actuated control stick movable in a plane and which replaces the steering wheel of conventional vehicles. An electronic circuit slaves the angular position of the vehicle's wheels to the position of this hand-actuated control stick.

Description

2 ~3 7 ~ J -j Case ~6 HM/clb VE~ICLE STEERING CONTRO~ DEVICE

The present invention concerns a device for controlling the steering of a vehicle having at least one steerable wheel angularly mobile relative to a pivoting axis to determine the direction of travel of said vehicle, said device comprising control means manually actuable by the vehicle's driver to steer said vehicle and slaving means coupled to said wheel and to said control means for slaving the angular position of said wheel about said pivoting axis to the position of said control means.

BACKGROUND OF THE INVENTION

In all vehicles such as motor cars or lorries manufactured and sold at the present time, the control means manually actuable by the driver to steer the vehicle are constituted by a steering wheel mounted on a shaft, generally called the steering column, which is mechanically coupled to the steerable wheels.
In the event of an accident, for instance a collision with a fixed obstacle or with another vehicle, the vehicle's driver may be seriously injured, or even killed, by being violently projected against the steering wheel or, if the latter is deformed or breaks, against the end of the steering column which may itself be projected inside the passenger compartment towards the driver.
Likewise, a passenger sitting beside the driver may be seriously injured, or even killed, by being violently projected against the vehicle's dashboard and/or windscreen.
One of the most effective expedients proposed and implemented to eliminate or at least reduce this danger consists in equipping the vehicle with protective air-bags that are normally empty and folded away in suitable 2 ~ r~ ` '3 housings, and are abruptly inflated in the event of a collision. These air-bags are arranged and dimensioned so that, when inflated, they dampen the shock of the driver and of the passenger, respectively against the steering wheel and against the dashboard or the windscreen.
The housing adapted to contain the driver's protective air-bag during normal use, i.e. when the air-bag is empty and folded, can obviously only be arranged in the hub of the steering wheel.
Consequently, on ~he one hand, this hub must have relatively large dimensions, which may detract from the visibility of the dashboard instruments, and on the other hand, this air-bag cannot be inflated to large dimensions, which limits its effectiveness in the case of accident.
A further consequence is that the driver~s protective air-bag and the passenger~s protective air-bag must be separate from one another, which increases their cost.
An object of the invention is to propose a vehicle steering control device by means of which these drawbacks are eliminated, specifically by means of which the effectiveness of the protection afforded to the driver in the event of an accident may be increased, and the cost of the protective device for the driver and his passenger may be reduced.

SUMMARY OF THE INVENTI~N

This object is achieved by the device according to the invention, wherein the manually-actuable control means for steering the vehicle comprises at least one hand-actuated control stick that is mobile in a plane, and wherein the means for slaving the angular position of the vehicle's steerable wheel to the position of the control means is arranged to slave the angular position of this wheel to the position of this hand-actuated control stick in said plane.

f~ ~ ~ f, '-~ ' 5 3 Further objects and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTICN OF T~E DRAWINGS

- Figure 1 ls a schematic partial plan view of a vehicle including a steering control device according to the invention;
- Figure 2 is a schematic partial side view of the vehicle of Figure 1;
- Figure 3 schematically shows the vehicle's steering control device of Figure 1;
- Figure 4 is a schematic partial plan view of a vehicle including another steering control device according to the invention;
- Figure 5 schematically shows a steering control device for the vehicle of Figure 4; and - Figure 6 schematically shows another steering control device for the vehicle of Figure 4.

DETAILED DESCRIPTION

The vehicle shown schematically and partially in Figure 1 in plan view includes two steerable wheels 1 and 2 fixed to an axle, not shown, in such a manner that each wheel can turn about a respective pivot la, 2a having a substantially vertical axis, i.e. substantially perpendicular to the plane of Figure 1.
The wheels 1 and 2 are both mechanically coupled to a rack 3 by articulated rods designated by references 4 and 5, which are shown only schematically and will not be described in detail because such elements are well known to specialists.
The rack 3 is guided in slides, not shown, allowing it to move lengthwise only, and the rods 4 and 5 are arranged in such manner that the wheels 1 and 2 pivot in ~ ~ ri~

the same direction about axes la and 2a in response to thls displacement of the rack 3. Pivoting of the wheels 1 and 2 is limited, on either side, by abutments not shown.
The teeth of rack 3 engage with a toothed wheel 6 itself coupled mechanlcally to the rotor of an electric motor 7. This rotor is not shown separately. Depending on the requirements of each case, this toothed wheel 6 may be directly fixed to the motor 7~s rotor shaft or may be connected to this shaft via a gear train, not shown.
The motor 7 is controlled by an electronic circuit 8 an example of which will be described below. At this point it will simply be mentioned that this circuit 8 has an input 8a and is arranged so as to slave the angular position of the motor 7's rotor, and hence the angular position of the wheels 1 and 2 about their pivots la and 2a, to a variable signal applied to input 8a.
This variable signal is supplied by a device 9 which in the present example is incorporated in the elbow rest lOa of the vehicle driver's seat 10.
Device 9 includes a hand-actuated control stick 11 extending upwardly from the upper surface of the elbow rest lOa ~see Figure 2) and which is disposed in such a manner that the vehicle's driver can hold it easily to incline it to the right or to the left, i.e. in a plane at least substantially perpendicular to the vehicle's longitudinal axis, between two end stops, not shown. The possible movements of the upper end of the hand-actuated control stick 11 are represented in Figure 1 by dashed arrows g (left) and d (right).
The device 9 also includes a position detector, which is not shown in Figure 1 but an example thereof will be described later. This detector is mechanically coupled to the hand-actuated control stick 11 and supplies an electric signal representative of the position of this hand-actuated control stick 11.
This signal supplied by this detector is applied to the input 8a of the electronic circuit 8 and is used by 2~ ij i 3 the latter to control the angular position of the motor 7's rotor.
Of course, the vehicle shown in Figure 1 also has driving wheels, which may be the steerable wheels themselves, at least one motor coupled to these driving wheels and means, for instance constituted by pedals, that can be actuated by the driver to make the vehicle go forward or in reverse or to apply brakes.
All these elements, along with the many other usual elements equipping a vehicle, have not been shown in Figure 1 as they are not directly related to the present invention. The same applies to the other figures described later.
The device 9 also includes means for returning the hand-actuated control stick 11 back to its median or rest position, which are also not shown in Figures 1 and 2.
It can readily be seen that the control means manually actuable by the driver to steer the vehicle shown in Figure 1 are constituted, in this example, by the hand-actuated control stick 11.
In operation, for each and every position into which the vehicle driver places the hand-actuated control stick 11, the device 9 produces an electric signal representative of this position.
In response to this signal, the electronic circuit 8 causes a rotation of the motor 7's rotor which adopts an angular position determined by the position of the hand-actuated control stick 11.
The wheels 1 and 2, which are connected to motor 7's rotor via wheel 6, rack 3 and rods 4 and 5, thus pivot about pivots la and 2a respectively and adopt an angular position also determined by the position of hand-actuated control stick 11.
The vehicle steering device of Figure 1 thus has no steering wheel. As a result, the space situated between the dashboard and the vehicle driver is free. It is thus possible to provide a single air-bag that is inflated in ~ ~ r~ "

case of accident to protect simultaneously the driver and his passenger, which reduces the cost of the safety device because the cost price of such a single air-bag is less than the sum of the cost prices of two separate air-bags.
Moreover, when this air-bag is empty and folded, it can be packed in a housing extending over the entire length of the dashboard.
The dimensions of this housing may thus be chosen so that when the air-bag is inflated it occupies a greater part of the space separating the driver from the dashboard than in known vehicles, which enhances the protection of the driver in the case of an accident.
In addition to the already-described elements, Figure 2 shows the vehicle's dashboard 12 and a housing 13 provided in the dashboard 12 to receive the air-bag for protecting the vehicle driver and passenger.
In the example shown in Figure 3, the position detector of the hand-actuated control stick 11 of Figure 1 consists of a potentiometer 14 whose cursor 14a is mechanically connected to this hand-actuated control stick 11 and whose terminals 14b and 14c are respectively connected to a positive voltage V+ and to a negative voltage V- of equal and opposite values relative to earth.
These voltages V+ and V- are supplied by a voltage source, not shown.
Cursor 14a is connected to the hand-actuated control stick 11 so that it moves substantially all the way along potentiometer 14 when this hand-actuated control stick 11 is moved from one of its end positions to the other. Thus, in one of these end positions of the hand-actuated control stick 11, for example the position it occupies when it is pushed to the left against its stop, cursor 14a is substantially at voltage V+, and in the other end position, in this example when it is pushed completely to the right, the cursor 14a is substantially at voltage V-.
The above-mentioned means for returning the hand-actuated control stick 11 back to its median position are schematically represented by two oppositely-acting springs lla and llb each having a first end connected to the hand-actuated control stick 11 and a second end connected to a fixed point.
The cursor 14a of potentiometer 14 is electrically connected to the input 8a of the electronic circuit 8, which is itself connected to the non-inverting input 15a of a differential amplifier 15 forming part of the electronic circuit 8.
In the given example, circuit 8 includes a second input 8b connected on the one hand to the inverting input 15b of amplifier 15 and on the other hand to the cursor 16a of a second potentiometer 16 whose terminals 16b and 16c are respectively connected to the same voltages V+ and V- as the terminals 14b and 14c of potentiometer 14.
Cursor 16a of potentiometer 16 is mechanically connected to the motor 7, possibly via a gear train that may include a part of the gear train connecting motor 7 to toothed wheel 6, so as to move substantially all the way along this potentiometer 16 when the wheels 1 and 2, not shown in Figure 3, are displaced by the motor 7 from one of their extreme angular positions to the other. For the vehicle given above by way of example, where the cursor 14a of potentiometer 14 is substantially at voltage V+
when the hand-actuated control stick 11 is pushed fully to the left, the cursor 16a of potentiometer 16 is connected to motor 7 in a corresponding manner, i.e. so that the cursor 16a is also substantially at voltage V+ when the wheels 1 and 2 are turned completely to the left about pivots la and 2a, and also substantially at voltage V-when the wheels 1 and 2 are turned completely to the right.
In a well known manner, the voltage of output 15c of differential amplifier 15 is positive when the voltage of its input 15a is more positive than the voltage of its input 15b, negative in the opposite case, and zero when the voltages of its inputs are equal.

8 2 ~ 7 ,~

The electronic circuit 8 further comprises a power amplifier 16 whose input is connected to the output 15c of differential amplifier 15 and whose output is connected to motor 7.
The structure of amplifier 16 depends evidently on the type of motor 7 and will not be described herè because this ampllfier can be designed without any problem by skilled persons knowing the motor 7.
It will simply be mentioned here that amplifier 16 is arranged so that, depending on whether its input voltage is positive or negative, motor 7's rotor turns in the direction producing pivoting of wheels 1 and 2 to the left or to the right, and the rotor is stopped when the input voltage of amplifier 16 is zero.
Operation of the device of Figure 3 will not be described in detail as it is obvious from the preceding explanations. It will simply be noted that this device does effectively slave the angular position of the vehicle~s wheels 1 and 2 to the position of hand-actuated control stick 11.
It is further noted that the device of Figure 3 may very well be used in the instance where the hand-actuated control stick 11 is arranged in such a manner as to move in a plane substantially vertical and parallel to the vehicle~s longitudinal axis, i.e. forwards or backwards.
In such a case, the device should be arranged so that the wheels 1 and 2 pivot in a first direction when hand-actuated control stick 11 is moved forwards, and in their second direction when hand-actuated control stick 11 is moved backwards.
The vehicle shown schematically and partially in Figure 4 in plan view includes, as that of Figure 1, steerable wheels 1 and 2 coupled to a rack 3 by articulated rods 4 and 5, the teeth of rack 3 engaging with a toothed wheel 6 which is mechanically coupled to an electric motor 7. All of these elements are similar to or 9 ~ J ~ ~

identical with those bearing the same references in ~igure 1 and will not be described again here.
As in the case of Figure 3, motor 7 is mechanically coupled to a detector of the angular position of wheels 1 and 2, which detector is not shown in Figure 4.
The vehicle of Figure 4 further comprises two identical devices 31 and 32 incorporated respectively in this example in the right-hand elbow-rest 33a and in the left-hand elbow-rest 33b of the driver~s seat 33.
Devices 31 and 32 each include a hand-actuated control stick 34, 35 respectively, which extends upwardly from the upper surface of the respective elbow-rest and is arranged in such a manner that the vehicle driver can easily hold it to move it manually forwards or rearwards in a plane substantially vertical and parallel to the vehicle~s longitudinal axis, between two end positions defined by stops not shown.
As will be described in detail below, each of these devices 31 and 32 further comprises a detector of the position of the corresponding hand-actuated control stick 34 or 35 and an electric motor whose rotor is mechanically coupled to this hand-actuated control stick. These position detectors and motors, which are not shown in Figure 4, are electrically connected to an electronic circuit 36, as are the motor 7 and the above-mentioned detector of the angular position of the wheels 1 and 2.
The electronic circult 36, an example of which will be described below, is arranged so that any displacement of one of the hand-actuated control sticks 34 and 35 in one direction or the other produces a displacement of the same amplitude but in the opposite direction of the other hand-actuated control stick, as well as a rotation of motor 7 in a direction such that the wheels 1 and 2 pivot to the left when hand-actuated control stick 34 is moved forwards or when hand-actuated control stick 35 is moved backwards, and such that these wheels 1 and 2 pivot to the right when hand-actuated control stick 34 is moved backwards or when hand-actuated control stick 35 is moved forwards.
Moreover, any pivoting of wheels 1 and 2 to the left or to the right, caused for instance by an irregularity of the ground on which the vehicle is being driven, produces a movement of hand-actuated control stick 34 forwards and a movement of hand actuated control stick 35 backwards or, respectively, movement of hand-actuated control stick 34 backwards and hand-actuated control stick 35 forwards.
Circuit 36 thus provides an electric coupling of the hand-actuated control sticks 34 and 35 with one another and with the wheels 1 and 2, by means of position detectors and motors mechanically coupled to ~he hand-actuated control sticks 34 and 35 and to the wheels 1 and 2.
This coupling is reciprocal, i.e. each displacement of any one of the three coupled elements, namely the hand-actuated control stick 34, hand-actuated control stick 35 and wheels 1 and 2, causes a well-defined displacement of the other two elements.
Thus, not only can the driver steer the vehicle by means of the hand-actuated control sticks 34 and 35, but the latter enable him to feel the reactions of the vehicle to the changes of direction initiated by him and/or to the state of the ground on which the vehicle is being driven, which procures a great sensation of safe driving.
In the example shown in Figure 5, the device 31 includes a motor 51 whose rotor, not shown separately, is mechanically connected to the hand-actuated control stick 34 and to the cursor 52a of a potentiometer 52 which constitutes the position detector of this hand-actuated control stick 34 and whose terminals are respectively connected to a positive voltage V+ and to a negative voltage V-, these two voltages being provided by an electric energy supplying source not shown. According to the case, the hand-actuated control stick 34 and/or the cursor 52a of potentiometer 52 may be connected directly 11 ~J ~ s '3 to the motor 51~s rotor shaft or may be connected to this shaft via a suitable gear train.
Likewise, the device 32 includes a motor 53 whose rotor, also not shown separately, is mechanically connected directly or via a gear train to the hand-actuated control stick 35 and to the cursor 54a of a potentiometer 54 which constitutes the position detector of this hand-actuated control stick 35 and whose terminals are also respectively connected to the voltages V+ and V-.
For reasons that will become apparent later in this description, the motors 51 and 53 are preferably identical, as are the potentiometers 52 and 54 and the mechanical connections between these motors, the cursors 52a and 54a of potentiometers 52 and 54, and the hand-actuated control sticks 34 and 35.
Moreover, these mechanical connections should preferably be arranged so that cursors 52a and 54a each move over substantially the entire length of the respective potentiometer 52, 54 when the corresponding hand-actuated control stick 34, 35 respectively is moved from one of its end positions to the other.
Furthermore, motors 51 and 53 as well as their mechanical connections with the hand-actuated control sticks 34 and 35 respectively, and their supply circuit should be dimensioned so that when these motors supply their maximum torque, the maximum force that is exerted on the upper ends of these hand-actuated control sticks is of the same order of magnitude or less than the force that the driver of a conventional vehicle with power-assisted steering must exert on the steering wheel to make the vehicle change direction, or the force that the steering wheel exerts on the driver~s hands when the vehicle's wheels touch an obstacle or pass over a hole.
Still in the example of Figure 5, the motor 7's rotor, which is also not separately shown and which is connected to wheels 1 and 2 via the toothed wheel 6 as described previously, is also mechanically connected to 1 2 ~ s the cursor 55a of a potentiometer 55 which constitutes the detector of the angular position of wheels 1 and 2 and whose terminals are also respectively connected to the voltages V+ and V-. In this case also, the mechanical connection between the motor 7's rotor, the toothed wheel 6 and/or potentiometer 55's cursor 55a may be direct or indirect.
The electronic circuit 36, also shown in Figure 5, includes three differential amplifiers 61, 62 and 63 whose non-inverting inputs designated by a + sign and whose inverting inputs designated by a - sign are connected to the cursors 52a, 54a and 55a of potentiometers 52, 54 and 55 in the indicated manner.
This electronic circuit 36 further comprises three additional differential amplifiers 64, 65, 66 whose non-inverting and inverting inputs also designated by + signs and - signs respectively are connected to the outputs of amplifiers 61, 62 and 63 in the indicated manner.
All of the differential amplifiers 61 to 66 are supplied by the same voltages V+ and V- as those applied to the terminals of potentiometers 52, 54 and 55.
Moreover, for reasons that will become apparent further on in the description, these amplifiers 61 to 66 are all arranged so that their output voltage is equal to the difference of the voltages applied to their inputs, as precisely as possible. The means for imparting this characteristic to amplifiers 61 to 66 will not be described here as they are well known to specialists.
The electronic circuit 36 further comprises three power amplifiers 67, 68 and 69 whose inputs are respectively connected to the outputs of amplifiers 64, 65 and 66 and whose outputs are respectively connected to motors 51, 53 and 7. These three power amplifiers 67 to 69 are of course adapted to the motors to which they are connected, and they are furthermore preferably arranged so that the torque supplied by these motors is at least substantially proportional to the applied voltage at their ~ ~ r~
input. In the following description, the direction in which these motors turn when the applied voltage at the input of amplifier 67, 68 or 69 is positive will arbitrarily be called positive, and vice versa.
AS will become apparent from the following description, for the device of Figure 5 to operate as set out in the description of Figure 4, it is necessary for the electrical connections between amplifiers 67, 68 and 69 and motors 51, 53 and 7 and for the mechanical connections between motors 51, 53 and 7 and the elements driven thereby, nameîy the hand-actuated control stick 34 and cursor 52a, the hand-actuated control stick 35 and cursor 54a, and the toothed wheel 6 and cursor 55a, respectively, to be so arranged that a rotation of the rotor of motor 51, motor 53 or motor 7 in the positive direction causes respectively a forward displacement of hand-actuated control stick 34, a backward displacement of hand-actuated control stick 35 and a rotation of toothed wheel 6 in the direction producing pivoting of the steerable wheels 1 and 2 towards the left, and that the same rotations of these rotors also cause a displacement of cursors 52a, 54a and 55a towards the ends of potentiometers 52, S4 and 55 connected to the voltage V+, and vice versa.
In the following description of operation of the circuit of Figure 5, the voltages of cursors 52a, 54a and 55a of potentiometers 42, 54 and 55 will be designated by Ul, U2 and U3 respectively, and the output voltages of amplifiers 61 to 66 will be designated by the letter U
followed by the reference number of the amplifier in question.
It can easily be seen that, whatever may be the voltages Ul, U2 and U3, the output voltages of amplifiers 61 to 63 are given by the equations :
U61 = U2 - Ul U62 = U3 - U2 and U63 = Ul - U3 14 2 ~

Likewise, the output voltages of amplifiers 64 to 66 are given by the equations :
U64 = U61 - U63 = U2 + U3 - 2Ul (1) U65 = U62 - U61 = U3 + Ul - 2U2 (2) and U66 = U63 - U62 = Ul + U2 - 2U3 (3) If the voltages Ul, U2 and U3 are equal, the voltages U64, U65 and U66 are consequently zero, and the torques supplied by motors 51, 53 and 7 are also zero. The system is in equilibrium.
If now the vehicle driver moves for instance the hand-actuated control stick 34 forwards, the voltage of cursor 52a increases and takes a new value that will be designated by Ul + DUl.
The voltage U64 applled to the input of amplifier 67 now being negative, motor 51's rotor tends to turn in the negative direction, hence tending to return the hand-actuated control stick 34 to its previous position. The vehicle's driver must thus exert some force on hand-actuated control stick 34 to maintain it in its new position.
The voltage U65 applied to the input of amplifier 68 now being positive, motor 53's rotor tends to turn in the positive direction and thus to move hand-actuated control stick 35 backwards. If the vehicle's driver does not oppose this movement, the voltage of cursor 54a becomes positive. This voltage is evidently variable as long as the hand-actuated control stick 54a is moving and will be called U2 + DU2, U2 being its original value and DU2 representing its variation.
Likewise, the voltage U66 applied to the input of amplifier 69 now being positive, motor 7 tends to turn in its positive direction and thus tends to pivot the wheels 1 and 2 towards the left. If nothing opposes this pivoting, the voltage of cursor 55a also becomes positive.
As above, this voltage is variable as long as the wheels ~, 6~
pivot, and will be called U3 + DU3, U3 also being its original value and DU3 representing its variation.
It can easily be seen that when the hand-actuated control stick 35 and wheels 1 and 2 respectively reach the positions where DU2 and DU3 are equal to DU1, the voltages U64, U65 and U66 once again become zero.
The system is thus once again in equilibrium, wheels 1 and 2 having plvoted to the left by an angle determined by the amplitude of the forward displacement of the hand-actuated control stick 34 imparted by the vehicle driver, and the hand-actuated control stick 35 having moved rearwards by the same distance as hand-actuated control stick 34.
Operation of the device of Figure 5 in the event where the vehicle driver moves the hand-actuated control stick 34 backwards can be deduced easily from the explanations given above and will not be described in detail here.
The same applies to operation of the device of Figure 5 when the vehicle driver moves the hand-actuated control stick 35 forwards or backwards, or when wheels 1 and 2 pivot to the left or to the right without the vehicle driver moving the hand-actuated control sticks 34 or 35, for example because of an irregularity of the ground on which the vehicle is driven.
The device of Figure 5 thus provides a total and reciprocal slaving of the position of hand-actuated control sticks 34 and 35 and wheels 1 and 2. Thanks to this particularity of the device, the vehicle driver may not only steer the vehicle, but he permanently feels, through the hand-actuated control sticks 34 and 35, the reactions of the vehicle to the changes of direction he imparts it and to the irregularities of the ground on which it is driven. As a result, the driver has a great sensation of safely driving his vehicle.
Such safe driving of the vehicle can be further enhanced by incorporating in the electronic circuit 36 of Figure 5 suitable additional compensating circuits, for instance arranged respectively between the outputs of amplifiers 64 to 66 and the inputs of amplifiers 67 to 69 and arranged in such a manner as to eliminate any risk of oscillation of the device. Such compensation circuits may for example be of the well known proportional-differential type.
These compensation circuits may also for instance be arranged so as to modify the respective ratios between the torques supplied by motors 51, 53 and 7 and the output signals of amplifiers 64, 65 and 66, as a function of the speed of the vehicle and/or of the amplitude of displacement of the hand-actuated control sticks 34 and 35 or of pivoting of the wheels 1 and 2.
These compensation circuits will not be described in detail here because their structure depends evidently on the function they must perform, and knowing this function the skilled person will not have any particular problems to solve in producing them.
The principle of the device of Figure 5 may also apply to controlling the steering of a vehicle similar to that of Figure 1, i.e. having only a single hand-actuated control stick that the vehicle driver can move to the right or to the left to steer the vehicle in these directions.
In such a case, of course there will be no device 32, the circuit 36 will not include amplifiers 62, 65 and 68, the inverting input of amplifier 63 will be connected to the non-inverting input of amplifier 61 and the output of the latter is connected to the inverting input of amplifier 66. Moreover, the electrical and mechanical connections between the various components must of course be so arranged that any displacement of the hand-actuated control stick 34 towards the left or the right causes a corresponding pivoting of the wheels 1 and 2, and vice versa.

The same principle may also be applied to controlling the steering of a vehicle having more than two steerable wheels, like some cars available at present ~hat have four steerable wheels, or like certain special vehicles designed to transport very long loads, that can have quite a large number of these steerable wheels.
In such cases, each pair of steerable wheels must be coupled to a unit comprising a motor similar to the motor 7 and an angular position detector similar to potentiometer 55. Moreover, the electronic circuit of the control device must have, for each pair of steerable wheels, a power ampllfier, similar to amplifier 69 of Figure 5, connected to the motor controlling pivoting of these steerable wheels, and a computing circuit similar to the circuits each formed by the amplifiers 61 and 64, 62 and 65, and 63 and 66 of Figure 5.
If the total number of mobile members, i.e. the hand-actuated control sticks and pairs of steerable wheels that must be slaved to one another is designated by N, it can be seen that each computing circuit must be arranged so as to apply to the power amplifier associated therewith a signal equal to the difference between, on the one hand, the sum of all the signals produced by the position detectors of the N mobile members and, on the other hand, N times the signal produced by the position detector associated with the motor controlled by this power amplifier.
In an equivalent manner, which corresponds to the manner in which the equations (1) to (3) above have been written, one can say that each computing circuit must supply to the power amplifier associated therewith a signal equal to the difference between, on the one hand, the sum of the signals supplied by the (N-l) position detectors associated with the (N-l) motors that are not controlled by this amplifier and, on the other hand, (N-l) times the signal supplied by the position detector associated with the motor controlled by this amplifier.

18 ~

An example of such a steering control device of a vehicle having more than three mobile members, control hand~
actuated control sticks and pairs of steerable wheels, slaved to one to another, will not be described here because its construction flows easily from the explanations given above.
The modifications that may be made to the hereinabove described device within the scope of the invention are very numerous, and only a few of them will be mentioned below by way of non-limiting examples.
Thus, the various potentiometers which, in the device described above, constitute the position detectors of the mobile elements, may advantageously be replaced by position detectors involving no mechanical contact such as capacitative or inductive detectors, to eliminate problems that may be caused in the potentiometers due to wear of the cursor and/or of the resistive element against which this cursor rubs.
These position detectors, which deliver analogue signals, may also advantageously be replaced by position detectors delivering numeric-type signals, i.e. signals formed of series of pulses transmitted along a single conductor, or signals transmitted in parallel along a plurality of conductors and each representing a bit of a binary number. The above-described computing circuits, also of the analogue type and formed by the various differential amplifiers described above, must of course be replaced then by suitable numeric computing circuits that will not be described here as their construction causes no problem to the person skilled in the art.
Likewise, the hand-actuated control sticks 11, 34 and may have a form different from that shown in the drawings. These hand-actuated control sticks 11, 34 and 35 may also be mechanically connected to the respective devices 9, 31 and 32 so as to move parallel to one another, and not pivot about an axis as is shown in the drawings.

~J '~ }
The device according to the invention may also be arranged without difficulty so that it can be supplied by two voltages not equal and opposite relative to earth, or even by a single voltage that is positive or negative relative to earth. Ilhe advantage of a device arranged in this latter manner resides in the fact that the circuit for supplying this single voltage is considerably simpler than a circuit that must supply two distinct voltages.
The present invention also applies without difficulty to the case where the steerable wheels of the vehicle are situated at its rear. In such a case, the motor corresponding to motor 7 of the above-described examples must evidently be connected to its control circuit and/or to these wheels in such a manner that, in all circumstances, these wheels pivot in a direction opposite to their direction of pivoting in the given examples.
It is further noted that the present invention applies without change to the case of a vehicle having only a single steerable wheel arranged in the middle of the front or rear part of the vehicle. Only the means for mechanically connecting this single wheel to the motor for pivoting it to the left or to the right would, possibly, be different from those that have been described in the case of vehicles with two steerable wheels.
All of the components of the vehicle steering control device shown in Figure 5 are again present, with the same references, in the device shown in Figure 6 and will thus not be described again here. These components are also connected to one another as in the device of Figure 5, with the exception of amplifiers 66 and 69 whose output and input respectively are no longer connected directly as will be described below.
In addition to these components, the device of Figure 6 comprises two sensors 71 and 72 each delivering an electric signal having a value representative of the force exerted by the vehicle driver respectively on the hand-actuated control stick 34 and on the hand-actuated control stick 35, in the direction of arrows d or g of Figure 4, to steer the vehicle.
In this example, each of these sensors 71 and 72 is made of a strain gauge associated with a suitable amplifier and fixed directly on the respective hand-actuated control stick 34, 35. This strain gauge and this amplifier have not been shown separately.
Each of sensors 71 and 72 may also be made ln well known manner by two strain gauges fitted on opposite sides of the respective hand-actuated control stick 34, 35 and associated with a differential amplifier.
The strain gauge(s) of each sensor 71 and 72 may also be fixed on the shaft of motor 51~s or motor 53's rotor respectively or, if these two motors 51 and 53 are connected to the hand-actuated control sticks 34 and 35 by gear trains, on the shaft of any one of the toothed wheels making up these gear trains.
In such embodiments, which have not been described because producing them is no problem for the skilled person, ~he value of the signal delivered by each of the sensors 71 and 72 is representative of the torque transmitted by the shaft on which the strain gauge(s) is/are fixed. sut as this torque is evidently proportional to the force exerted on the corresponding hand-actuated control stick 34 or 35, the value of the signal delivered by the sensor 71 or sensor 72 is also representative of this force.
The device of Figure 6 also has a sensor 73 delivering an electrical signal having a value representative of the torque that tends to pivot the vehicle's wheels 1 and 2 about their pivots la and 2a (see Figure 4).
This sensor 73 may for example consist of a strain gauge fixed on the motor 7's rotor shaft and associated with a suitable amplifier.
If the motor 7 is connected to the toothed wheel 6 (Figure 4) by a gear train, the strain gauge of sensor 73 may evidently be fixed on the shaft of any one of the toothed wheels making up this gear train.

2 1 ~ J c3 This strain gauge may also be fixed on either of the steering rods 4 and 5 connecting the rack 3 to wheels 1 and 2, or on this rack 3 (see Figure 4).
In such an embodiment, which has not been described because producing it is no problem for the skilled person, the value of the signal delivered by the sensor 73 is representative of the force exerted on the element to which the strain gauge is fixed. sut as this force is evidently proportional to the torque tending to pivot the wheels 1 and 2 about their pivots la and 2a, the value of the signal produced by the sensor 73 is also representative of this torque.
In the following description, it will be assumed that the signals produced by the sensors 71, 72 and 73 are constituted by voltages, that will be respectively designated by references U71, U72 and U73.
The computing circuit 36 of the device of Figure 6 further comprises an adding circuit 74 having four inputs connected respectively to the sensors 71, 72 and 73 and to the output of amplifier 66, as well as an output connected to the input of amplifier 69. This adding circuit 74 is a circuit well known to specialists and will therefore not be described here, if only to mention that the voltage U74 it supplies at its output, and thus to the input of amplifier 69, is given by the equation :
U74 = U66 + U71 + U72 + U73 (4) It should be noted here that equations (1), (2) and (3) mentioned above in connection with the operation of the device of Figure 5 are equally valid in the case of a device according to Figure 6 because, in both these devices, the amplifiers 61 to 66 and the position detectors formed by potentiometers 52, 54 and 55 are identical and are connected together in the same manner. The term U66 of equation (4) above can thus be replaced by its value given by equation (3) to obtain the following equation :
U74 = Ul + U2 - 2U3 + U71 + U72 +U73 (5) 22 (., ~:

It will also be assumed that sensors 71 and 72 are arranged in such a manner that voltages U71 and U72 are positive when the vehicle's driver exerts on the hand-actuated control stick 34 and the hand-actuated control stick 35 respectively a force tending to move this hand-actuated control stick 34 or 35 in the direction of the arrows designated by g in Figure 4, namely when the driver desires to turn the vehicle towards the left, and when the corresponding motor 51 or 53 produces a torque opposing this movement, i.e. a torque tending to move the hand-actuated control sticks in the direction of arrows d of Figure 4. It will be recalled that by using the same conventions as in the case of Figure 5, motors 51 and 53 produce such a torque when the voltages U64 and U65 respectively are negative.
It will further be assumed that the sensor 73 is arranged in such a manner that voltage U73 is positive when the wheels 1 and 2 are subjected to a torque, due for example to the reaction of the ground on which they are rolling, tending to pivot them towards the left about their pivots la and 2a (Figure 4), and that motor 7 produces a torque opposing this pivoting. Using once again the same conventions as in the case of Figure 5, the motor 7 produces such a torque when the voltage applied to the input of amplifier 69 is negative.
As operation of the device of Figure 6 is very complex and depends on the respective characteristics of each of its components, it will be described here only in a very general way. Moreover, to simplify this description, it will be assumed that to steer the vehicle, the driver of a vehicle equipped with this device acts only on the hand-actuated control stick 34 and thus exerts no force on the hand-actuated control stick 35. In this example, the voltage U72 is thus always zero.
When the vehicle follows a straight line on perfectly flat ground, the voltages Ul to U3 and U71 to U73 are of course zero. Equations (1), (2) and (5) above show that the 2 3 ~ ';

voltages U64, U65 and U74 are thus also zero. The motors 51, 53 and 7 therefore produce no torque.
If the vehicle~s driver then for example desires to turn left, he acts on the hand-actuated control stick 34 to move it ln the direction of arrow g extending from this hand-actuated control stick 34 in Figure 4.
Voltage Ul then tends to become positive, so that, as shown by equation (1), the voltage U64 tends to become negative. Motor 51 thus produces a torque opposing the displacement of hand-actuated control stick 34.
If the gain of amplifier 67 is high, which is desirable for a reason that will be given later, this torque is also high, so that the hand-actuated control stick 34 practically does not move, with voltage Ul thus remaining very low.
But, simultaneously, as a result of the force exerted by the vehicle~s driver on the hand-actuated control stick 34 and the torque produced by motor 51 as just described, the voltage U71 produced by sensor 71 becomes positive.
Equation (5) shows that the voltage U74 becomes consequently also positive. Motor 7 then begins to turn in the direction that causes pivoting of wheels 1 and 2 towards the left about their pivots la and 2a (Figure 4).
The voltage U3 thus becomes positive which, as shown by equation (1), notably results in the voltage U64 becoming less negative, or even positive. The torque produced by motor 51 and which opposed the displacement of hand-actuated control stick 34 thus diminishes, or even changes direction, so that hand-actuated control stick 34 can now move in response to the force exerted thereon by the vehicle's driver.
sut following this displacement of hand-actuated control stick 34, voltage Ul becomes more positive, so that voltage U64 once more becomes more negative and the torque produced by motor 51 in the direction opposing this displacement increases once again.
The fact that voltage Ul becomes more positive tends to make voltage U74 also more positive, but this variation of 24 ~! r~ J

voltage u74 is counterbalanced by the increase of voltage U3 and by the fact that, at the same time, as a result of the pivoting of wheels 1 and 2 towards the left, the voltage U73 produced by sensor 73 becomes negative because the ground on which the wheels 1 and 2 are rolling produces a reactive torque opposing their pivoting.
It can be understood that, a given rather short time after the vehicle's driver has begun to act on hand-actuated control stick 3~, the device assumes a stable state.
Theoretical considerations which will not be set out here show that, in this stable state, voltage U74 is always positive, its value being such that the torque produced by motor 7 exactly balances that exerted by reaction of the ground on wheels 1 and 2.
Moreover, this reactive torque prevents the wheels 1 and 2 from reaching the angular position in which voltage U3 would be equal to voltage Ul. This voltage U3 is thus less than voltage Ul.
Additionally, because, in the present example, the vehicle~s driver does not act on hand-actuated control stick 35, the latter adopts a position in which voltage U65 is zero.
Equation (2) shows that, in this case, voltage U2 is equal to the mean value of voltages Ul and U3 or, in other words, that U2 = Ul + U3 By inserting this value in equation (1), it can be seen that U64 = 3U3 - 3Ul Because voltages Ul and U3 are both positive and the former is greater than the latter as has been seen above, voltage U64 is negative, i.e. motor 51 produces a torque tending to displace hand-actuated control stick 34 in the direction of arrow d extending from this hand-actuated control stick 34 in Figure 4. The vehicle's driver must thus ~! ,~--1 7 permanently exert a force on hand-actuated control stick 34 to maintain it in the desired position, and voltage U71 remains positive.
It can easily be seen that, in equation (5), the term (U1 + U2 - 2U3) is positive. Also, as has been seen above, voltage U71 is positive, voltage U72 is zero, and voltage U73 is negative. The term (U71 + U72 + U73) of equatlon (5) is thus positive or negative according to whether the absolute value of voltage U73 is respectively smaller or larger than voltage U71.
However, as the device of Figure 6 is in equilibrium and voltage U74 is necessarily positive, it can be seen that if this term (U71 + U72 + U73) is negative, its absolute value is less than the value of the term (U1 + U2 - 2U3).
This state of the device of Figure 6 remains stable as long as the vehicle~s driver holds hand-actuated control stick 34 in the same position and the ground on which the wheels 1 and 2 are rolling is perfectly flat.
It can easily be seen that if the driver changes the position of hand-actuated control stick 34 to modify the vehicle~s trajectory, the device assumes another stable state, depending on the new position of hand-actuated control stick 34.
Moreover, if the pivoting torque exerted by the ground by reaction on wheels 1 and 2 is modified, for example due to a change in the vehicle's speed, the device also assumes a new stable state depending on the new value of this torque. In particular, lf the driver wishes to maintain the vehicle on the same trajectory, he must consequently modify the force he exerts on hand-actuated control stick 34.
It is obvious that analogous considerations apply in the case where the driver wishes to turn the vehicle to the right and thus exerts on hand-actuated control stick 34 a force in the direction of arrow d extending from this hand-actuated control stick 34 in Figure 4, and also in the case where the driver acts solely on the hand-actuated control stick 35 to steer the vehicle, or in the case where he acts 2 6 h v 7 ~ ~ ~

simultaneously on the two hand-actuated control sticks 34 and 35.
In practice, a stable state such as that just described above is rarely achieved because, on the one hand, the trajectory of a vehicle is practically never exactly circular for a relatively long time and, on the other hand, the ground on which the vehicle's wheels roll is hardly ever perfectly flat.
It can however be seen that, in all situations, the driver keeps a very good control of the vehicle's steering because each modification in the posit~on of hand-actuated control stick 34 and/or of hand-actuated control stick 35 produces a corresponding modification of the angular position of wheels 1 and 2, and conversely.
The equations (1) to (3) used above to explain operation of the device of Figure 5 show, as previously mentioned, that any displacement of one of the mobile members, namely the hand-actuated control sticks 34 or 35 or the wheels 1 and 2, results in the voltage U64, U65 or U66, applied to the input of amplifier 67, 68 or 69 supplying the control signal to the motor 51, 53 or 7 that is associated with this mobile member, assuming a value such that this motor 51, 53 or 7 produces a torque opposing such displacement of the mobile member~
It can be seen that, in the case of the device of Figure 5, the gain of amplifiers 67 to 69 must not be too high, because otherwise absolutely no movement of anv of the mobile members would be possible, and the device would thus be practically blocked.
But if the gain of amplifiers 67 to 69 is sufficiently low to allow the device of Figure 5 to operate, the slaving of the position of each of the mobile members to the position of the other mobile members becomes imprecise, as though the connections between these mobile members were to some extent elastic.
In the device of Figure 6, on the other hand, the presence of force or torque sensors 71 to 73, and the fact 27 ~ "~ , r~ ~

that the signals U71 to U73 supplied by these sensors are combined with signal U66 in the adding circuit 74 in the manner described above to supply the control signal of motor 7 has for result that the gain of amplifiers 67 to 69 may be very high, what gives a very high precision to the reciprocal slaving of the different mobile members, without however blocking the device.
So, even if this gain of amplifiers 57 to 69 is very high, any variation of the force or torque exerted on one of the mobile members produces a variation of voltage U74 and, in cascade, of the angular position of wheels 1 and 2, of voltage U3, of voltages U64 and U65, and of position of hand-actuated sticks 34 and 35.
In other embodiments of the device according to the present invention, the latter comprises exactly the same components as the device o' Figure 6, but the output of amplifier 66 is directly connected to the input of amplifier 69. Moreover, the output of adding circuit 74 is connected, in a first of these other embodiments, to the input of amplifier 67 and, in a second of these other embodiments, to the input of amplifier 68. Further, three of the inputs of this adding circuit are respectively connected to the force or torque sensors 71, 72 and 73, and its fourth input is connected to the output of amplifier 64 in the above first other embodiment, and to the output of amplifier 65 in the above second other embodiment.
Any person skilled in the art will easily see that these other embodiments, which have not been shown, both function in a way very similar to that of the device of Figure 6 and have the same advantages as the latter.
It is evident that all the modifications which may be made in the device of Figure 5 and some of which have been mentioned in the description of that device may also be made in the device of Figure 6. These modifications will thus not be mentioned here.

Claims (13)

WHAT W CLAIM IS

1. A device for controlling the steering of a vehicle having at least one steerable wheel angularly mobile relative to a pivoting axis to determine the direction of travel of said vehicle, said device comprising control means manually actuable by the vehicle's driver for steering said vehicle and slaving means coupled to said wheel and to said control means for slaving the angular position of said wheel about said pivoting axis to the position of said control means, wherein said control means comprises at least one hand-actuated control stick that is mobile in a first plane, and said slaving means is arranged to slave the angular position of said wheel to the position of said hand-actuated control stick in said plane.

2. A device according to claim 1, wherein said plane is substantially perpendicular to the longitudinal axis of said vehicle, and said slaving means is arranged to cause said wheel to pivot in a first direction in response to a displacement of said hand-actuated control stick in a first direction in said plane and said wheel to pivot in a second direction in response to a displacement of said hand-actuated control stick in a second direction in said plane.

3. A device according to claim 2, wherein said slaving means is further arranged to cause a displacement of said hand-actuated control stick in said first and second directions in response to a pivoting of said wheel in its first and second directions, respectively.

4. A device according to claim 3, wherein said slaving means comprises :
- a first motor mechanically coupled to said hand-actuated control stick and means electrically coupled to said first motor for causing a displacement of said hand-actuated control stick in said plane, by means of said first motor, in response to a first control signal, the amplitude and the direction of displacement of said hand-actuated control stick being dependent on the value of said first control signal;
- a first position detector mechanically coupled to said hand-actuated control stick for producing a first detection signal representative of the position of said hand-actuated control stick in said plane;
- a second motor mechanically coupled to said wheel and means electrically coupled to said second motor for causing a pivoting of said wheel, by means of said second motor, in response to a second control signal, the amplitude and direction of pivoting of said wheel being dependent on the value of said second control signal;
- a second position detector mechanically coupled to said wheel for producing a second detection signal representative of the angular position of said wheel; and - computing means for producing said first control signal with a value equal to the difference between said second detection signal and said first detection signal and for producing said second control signal with a value equal to the difference between said first detection signal and said second detection signal.

5. A device according to claim 3, wherein said slaving means comprises :
- a first motor mechanically coupled to said hand-actuated control stick and means electrically coupled to said first motor for causing a displacement of said hand-actuated control stick in said plane, by means of said first motor, in response to a first control signal, the amplitude and the direction of said displacement of said hand-actuated control stick being dependent on the value of said first control signal;
- a first position detector mechanically coupled to said hand-actuated control stick for producing a first detection signal representative of the position of said hand-actuated control stick in said plane;
- a second motor mechanically coupled to said wheel and means electrically coupled to said second motor to cause a pivoting of said wheel, by means of said second motor, in response to a second control signal, the amplitude and direction of said pivoting of said wheel being dependent on the value of said second control signal;
- a second position detector mechanically coupled to said wheel for producing a second detection signal representative of the angular position of said wheel;
- a first sensor coupled to said hand-actuated control stick for producing a third detection signal representative of a force exerted on said hand-actuated control stick;
- a second sensor coupled to said wheel for producing a fourth detection signal representative of a pivoting torque exerted on said wheel ; and - computing means for producing said first control signal with a value equal to the difference between said second detection signal and said first detection signal, and for producing said second control signal with a value equal to the sum of the difference between said first detection signal and said second detection signal, of said third detection signal and of said fourth detection signal.

6. A device according to claim 3, wherein said slaving means comprises :
- a first motor mechanically coupled to said hand-actuated control stick and means electrically coupled to said first motor for causing a displacement of said hand-actuated control stick in said plane, by means of said first motor, in response to a first control signal, the amplitude and the direction of said displacement of said hand-actuated control stick being dependent on the value of said first control signal;
- a first position detector mechanically coupled to said hand-actuated control stick for producing a first detection signal representative of the position of said hand-actuated control stick in said plane;
- a second motor mechanically coupled to said wheel and means electrically coupled to said second motor to cause a pivoting of said wheel, by means of said second motor, in response to a second control signal, the amplitude and direction of said pivoting of said wheel being dependent on the value of said second control signal;
- a second position detector mechanically coupled to said wheel for producing a second detection signal representative of the angular position of said wheel ;
- a first sensor coupled to said hand-actuated control stick for producing a third detection signal representative of a force exerted on said hand-actuated control stick;
- a second sensor coupled to said wheel for producing a fourth detection signal representative of a pivoting torque exerted on said wheel; and - computing means for producing said first control signal with a value equal to the sum of the difference between said second detection signal and said first detection signal, of said third detection signal and of said fourth detection signal, and for producing said second control signal with a value equal to the difference between said first detection signal and said second detection signal.

7. A device according to claim 1, wherein said control means comprises a second hand-actuated control stick movable in a second plane at least substantially parallel to said first plane, said first and second hand-actuated control sticks are respectively disposed on opposite sides of said driver who can move them manually in a first and in a second direction in said first plane and in said second plane respectively, and said slaving means is arranged to cause a pivoting of said wheel in a first direction in response to a displacement of said first hand-actuated control stick in its first direction and of said second hand-actuated control stick in its second direction, and to cause a pivoting of said wheel in a second direction in response to a displacement of said first hand-actuated control stick in its second direction and of said second hand-actuated control stick in its first direction.

8. A device according to claim 7, wherein said slaving means further comprises means responsive to a displacement of one of said first and second hand-actuated control sticks for causing a displacement of the other hand-actuated control stick by the same amplitude but in the opposite direction.

9. A device according to claim 8, wherein said slaving means further comprises means responsive to an angular displacement of said wheel in its first direction for causing a displacement of said first hand-actuated control stick in its first direction and of said second hand-actuated control stick in its second direction, and responsive to an angular displacement of said wheel in its second direction for causing a displacement of said first hand-actuated control stick in its second direction and of said second hand-actuated control stick in its first direction.

10. A device according to claim 9, wherein said slaving means comprises :
- a first motor mechanically coupled to said first hand-actuated control stick and means electrically coupled to said first motor for causing a displacement of said first hand-actuated control stick in said first plane, by means of said first motor, in response to a first control signal, the amplitude and the direction of displacement of said first hand-actuated control stick being dependent on the value of said first control signal;
- a first position detector mechanically coupled to said first hand-actuated control stick for producing a first detection signal representative of the position of said first hand-actuated control stick in said first plane;
- a second motor mechanically coupled to said second hand-actuated control stick and means electrically coupled to said second motor for producing a displacement of said second hand-actuated control stick in said second plane, by means of said second motor, in response to a second control signal, the amplitude and direction of displacement of said second hand-actuated control stick being dependent on the value of said second control signal;
- a second position detector mechanically coupled to said second hand-actuated control stick for producing a second detection signal representative of the position of said second hand-actuated control stick in said second plane;
- a third motor mechanically coupled to said wheel and means electrically coupled to said third motor for causing a pivoting of said wheel, by means of said third motor, in response to a third control signal, the amplitude and direction of pivoting of said wheel being dependent on the value of said third control signal;
- a third position detector mechanically coupled to said wheel for producing a third detection signal representative of the angular position of said wheel; and - computing means for producing:
- said first control signal with a value equal to the difference between, on the one hand, the sum of said second detection signal and said third detection signal and, on the other hand, two times said first detection signal;
- said second control signal with a value equal to the difference between, on the one hand, the sum of said first detection signal and said third detection signal and, on the other hand, two times said second detection signal; and - said third control signal with a value equal to the difference between, on the one hand, the sum of said first detection signal and said second detection signal and, on the other hand, two times said third detection signal.

11. A device according to claim 8, wherein said slaving means comprises :
- a first motor mechanically coupled to said first hand-actuated control stick and means electrically coupled to said first motor for causing a displacement of said first hand-actuated control stick in said first plane, by means of said first motor, in response to a first control signal, the amplitude and the direction of displacement of said first hand-actuated control stick being dependent on the value of said first control signal;
- a first position detector mechanically coupled to said first hand-actuated control stick for producing a first detection signal representative of the position of said first hand-actuated control stick in said first plane;
- a second motor mechanically coupled to said second hand-actuated control stick and means electrically coupled to said second motor for causing a displacement of said second hand-actuated control stick in said second plane, by means of said second motor , in response to a second control signal, the amplitude and direction of displacement of said second hand-actuated control stick being dependent on the value of said second control signal;
- a second position detector mechanically coupled to said second hand-actuated control stick for producing a second detection signal representative of the position of said second hand-actuated control stick in said second plane;
- a third motor mechanically coupled to said wheel and means electrically coupled to said third motor for causing a pivoting of said wheel, by means of said third motor, in response to a third control signal , the amplitude and direction of pivoting of said wheel being dependent on the value of said third control signal;
- a third position detector mechanically coupled to said wheel for producing a third detection signal representative of the angular position of said wheel;
- a first sensor coupled to said first hand-actuated control stick for producing a fourth detection signal representative of a force exerted on said first hand-actuated control stick;
- a second sensor coupled to said second hand-actuated control stick for producing a fifth detection signal representative of a force exerted on said second hand-actuated control stick;
- a third sensor coupled to said wheel for producing a sixth detection signal representative of a pivoting torque exerted on said wheel; and - computing means for producing:
- said first control signal with a value equal to the difference between, on the one hand, the sum of said second detection signal and said third detection signal and, on the other hand, two times said first detection signal;
- said second control signal with a value equal to the difference between, on the one hand, the sum of said first detection signal and said third detection signal and, on the other hand, two times said second detection signal; and - said third control signal with a value equal to the difference between, on the one hand, the sum of said first, second, fourth, fifth and sixth detection signals and, on the other hand, two times said third detection signal.

12. A device according to claim 8, wherein said slaving means comprises :
- a first motor mechanically coupled to said first hand-actuated control stick and means electrically coupled to said first motor for causing a displacement of said first hand-actuated control stick in said first plane, by means of said first motor, in response to a first control signal, the amplitude and the direction of displacement of said first hand-actuated control stick being dependent on the value of said first control signal;
- a first position detector mechanically coupled to said first hand-actuated control stick for producing a first detection signal representative of the position of said first hand-actuated control stick in said first plane;
- a second motor mechanically coupled to said second hand-actuated control stick and means electrically coupled to said second motor for causing a displacement of said second hand-actuated control stick in said second plane, by means of said second motor, in response to a second control signal, the amplitude and direction of displacement of said second hand-actuated control stick being dependent on the value of said second control signal;
- a second position detector mechanically coupled to said second hand-actuated control stick for producing a second detection signal representative of the position of said second hand-actuated control stick in said second plane;
- a third motor mechanically coupled to said wheel and means electrically coupled to said third motor for causing a pivoting of said wheel, by means of said third motor, in response to a third control signal, the amplitude and direction of pivoting of said wheel being dependent on the value of said third control signal;
- a third position detector mechanically coupled to said wheel for producing a third detection signal representative of the angular position of said wheel;
- a first sensor coupled to said first hand-actuated control stick for producing a fourth detection signal representative of a force exerted on said first hand-actuated control stick;
- a second sensor coupled to said second hand-actuated control stick for producing a fifth detection signal representative of a force exerted on said second hand-actuated control stick;
- a third sensor coupled to said wheel for producing a sixth detection signal representative of a pivoting torque exerted on said wheel; and - computing means for producing:
- said first control signal with a value equal to the difference between, on the one hand, the sum of said second, third, fourth, fifth and sixth detection signals and, on the other hand, two times said first detection signal;
- said second control signal with a value equal to the difference between, on the one hand, the sum of said first and third detection signals and, on the other hand, two times said second detection signal; and - said third control signal with a value equal to the difference between, on the one hand, the sum of said first and second detection signals and, on the other hand, two times said third detection signal.

13. A device according to claim 8, wherein said slaving means comprises :
- a first motor mechanically coupled to said first hand-actuated control stick and means electrically coupled to said first motor for causing a displacement of said first hand-actuated control stick in said first plane, by means of said first motor, in response to a first control signal, the amplitude and the direction of displacement of said first hand-actuated control stick being dependent on the value of said first control signal;
- a first position detector mechanically coupled to said first hand-actuated control stick for producing a first detection signal representative of the position of said first hand-actuated control stick in said first plane;
- a second motor mechanically coupled to said second hand-actuated control stick and means electrically coupled to said second motor for causing a displacement of said second hand-actuated control stick in said second plane, by means of said second motor, in response to a second control signal, the amplitude and direction of displacement of said second hand-actuated control stick being dependent on the value of said second control signal;
- a second position detector mechanically coupled to said second hand-actuated control stick for producing a second detection signal representative of the position of said second hand-actuated control stick in said second plane;
- a third motor mechanically coupled to said wheel and means electrically coupled to said third motor for causing a pivoting of said wheel, by means of said third motor, in response to a third control signal, the amplitude and direction of pivoting of said wheel being dependent on the value of said third control signal;

- a third position detector mechanically coupled to said wheel for producing a third detection signal representative of the angular position of said wheel;
- a first sensor coupled to said first hand-actuated control stick for producing a fourth detection signal representative of a force exerted on said first hand-actuated control stick;
- a second sensor coupled to said second hand-actuated control stick for producing a fifth detection signal representative of a force exerted on said second hand-actuated control stick;
- a third sensor coupled to said wheel for producing a sixth detection signal representative of a pivoting torque exerted on said wheel; and - computing means for producing:
- said first control signal with a value equal to the difference between, on the one hand, the sum of said second detection signal and said third detection signal and, on the other hand, two times said first detection signal;
- said second control signal with a value equal to the difference between, on the one hand, the sum of said first, third, fourth, fifth and sixth detection signals and, on the other hand, two times said second detection signal; and - said third control signal with a value equal to the difference between, on the one hand, the sum of said first and second detection signals and, on the other hand, two times said third detection signal.