FR3008466A1 - METHOD AND SYSTEM FOR CONTROLLING THE DRIVING OF A VEHICLE HAVING A RIGHT TRANSMISSION AND A LEFT TRANSMISSION - Google Patents

Abstract

A method of controlling the drive of a vehicle having a right transmission and a left transmission, each powered by a variable displacement pump (13, 23), wherein a speed control is defined by means of a pedal and a angular control by means of a steering wheel, a reference threshold angular value and reference control laws corresponding to the minimum and maximum speed of the vehicle, the actual angular control defined by the steering wheel is compared to the reference threshold angular value and a correction coefficient of the pump displacement is calculated on the basis of the actual speed, by interpolation on a segment connecting the reference control law corresponding to the minimum and maximum speed, which segment is located respectively on either side of the reference threshold angular value depending on whether the actual angular control is less than or greater than the reference threshold angular value.

Description

GENERAL TECHNICAL FIELD The present invention relates to the field of vehicle controls having two transmissions; one side of the vehicle, for example a crawler machine for which the turns are made by varying the speed for each side of the vehicle. STATE OF THE ART Transmission vehicles per side are commonly equipped with two throttles; a right joystick controlling the transmission on the right side of the vehicle, and a left joystick controlling the transmission on the left side of the vehicle.

The piloting is done with both hands; - To go forward, the two joysticks are actuated jointly, - To turn on one side, a separate force is applied to both joysticks, which leads to an asymmetry in the transmission, and thus to a turning of the machine, the turn is variable depending on the command difference applied. Pivoting of the vehicle, ie a turn made on the spot, can be achieved by transmissions operating in opposite directions for both sides of the vehicle; the wheels or tracks on one side of the vehicle then rotate in one direction, and the wheels or tracks on the other side of the vehicle turn in the opposite direction. It is understood that such a control system is impractical, and that an unexpected operation of one of the joysticks can cause a reversal of direction of one of the transmissions of the vehicle while the latter is traveling at high speed, this which can be dangerous for the user.

The same problem is encountered when the steering or pivoting control is formed of a steering wheel or equivalent means and it is rotated to a large angle at high speed of the vehicle.

Examples of systems proposed according to the state of the art can be found in the documents EP 0151207, US 5487437, EP 2327607 and EP 1118581. PRESENTATION OF THE INVENTION The present invention thus aims to propose a control of a transmission vehicle by side, by means of a steering wheel defining an angle setpoint, and pedals defining a speed setpoint, which eliminates the disadvantages of the state of the art.

The invention thus proposes a method for controlling the drive of a vehicle having a right transmission for its right side and a left transmission for its left side, said right and left transmissions being each powered by a variable displacement pump, respectively a right pump and a left pump, in which the said pumps are controlled by a computer applying a control law to each of the said pumps defined as a function of: the maximum displacement of each of the pumps, a speed control, a angular control, in which - a speed control is defined by means of a pedal and an angular control by means of a steering wheel, - a reference threshold angular value is defined, - a reference control law corresponding to a minimum vehicle speed and a reference control law corresponding to a maximum speed of the vehicle, - the angular control is compared real re defined by the flywheel at the reference threshold angular value, a correction coefficient of pump displacement is calculated on the basis of the real speed, situated between the minimum speed and the maximum speed, by interpolation on a segment connecting the law of reference command corresponding to the minimum speed and the reference control law corresponding to the maximum speed, which segment is located respectively on either side of the reference threshold angular value depending on whether the actual angular control is less than or greater than the reference threshold angular value. Alternatively, a parallelism coefficient is determined, which is applied to control laws determining the displacement of each of the left and right pumps so as to compensate for structural asymmetries in the system. According to other advantageous features of the invention: when the angular control is non-zero, the displacement of the pump 20 located outside the requested turn remains constant, while the displacement of the pump located inside the turn gradually decreases, at least to zero cubic capacity; - at minimum speed and at maximum rotation angle, the two pumps are at equal speed but in opposite directions; At minimum speed, the pump located inside the turn is at zero displacement when the angular control is equal to the reference threshold angular value; for a non-zero angular value, the displacement of one of the pumps gradually decreases, preferably linearly, to a point of inflection corresponding to the reference threshold angular value, from which the displacement continues to evolve but more rapidly, preferably linearly, until reaching a final value for a maximum angular value; for an intermediate speed between the minimum speed and the maximum speed, the method implements a control law for which the displacement is zero when the speed is maximum; the method comprises a step of parameterizing the characteristic points of the control laws; the parameterization step comprises the parameterization of at least one of the following characteristic points: To which corresponds to the cubic capacity in a straight line at minimum speed,. F which corresponds to the displacement in a straight line at maximum speed, preferably equal to the maximum displacement of the pumps, B which corresponds to an inflection point of the minimum speed reference control curve, to the reference threshold angular value,. D which corresponds to the point of inflection of the maximum speed reference control curve, to the reference threshold angular value,. C which corresponds to the displacement for an angle of 100%, preferably symmetrical of A, at minimum speed, - E which corresponds to the displacement for an angle of 100%, at maximum speed; the parameterization step comprises the parameterization of a maximum speed value taken into account for applying the reference control law to a maximum speed of the vehicle, used to calculate the corrective coefficient of displacement of the pump on the basis of the speed real, even if the vehicle can go faster; the parameterization step comprises the parameterization of a coefficient of parallelism; the parameterization step comprises the parameterization of an interpolation coefficient implemented during the interpolation on segments connecting the reference control law corresponding to the minimum speed and the reference control law corresponding to the speed. Maximum, located respectively on either side of the reference threshold angular value depending on whether the actual angular command is lower or higher than the reference threshold angular value, is a linear interpolation; interpolation on segments connecting the reference control law corresponding to the minimum speed and the reference control law corresponding to the maximum speed, located respectively on either side of the reference threshold angular value depending on whether the actual angular control is less than or greater than the reference threshold angular value, is a linear interpolation; the minimum speed corresponding to the minimum speed reference control law of the vehicle is a zero forward speed, making it possible to control a pivoting of the vehicle on itself if the angular control exceeds a threshold; in a variant, the method comprises the following steps: the speed control is compared with a speed control threshold value,. if the control speed is greater than or equal to said speed control threshold value, a control law is applied to said right and left transmissions so that they operate in the same driving direction, if the control speed is lower than said speed control threshold value, a control law is applied to said right and left transmissions so that for angular control whose absolute value is greater than or equal to the threshold angular value reference, said right and left transmissions operate in reverse drive directions; the method uses a speed control threshold value for which the control law imposes the same drive direction on the two pumps regardless of the angular control and for speed values below this speed control threshold value, it is possible to drive the pumps in opposite directions. The invention also proposes a system for controlling the drive of a vehicle, comprising a right transmission for its right side and a left transmission for its left side, said right and left transmissions being each powered by a variable displacement pump. , respectively a right pump and a left pump, said system further comprising a computer configured so as to drive said pumps by applying a control law to each of said pumps defined as a function of: the maximum displacement of each of the pumps; a speed control, - an angular control, the system comprising a pedal defining a speed control and a steering wheel defining an angular control, the computer being furthermore configured so as to define a reference threshold angular value, - defining a control law reference command corresponding to a minimum speed of the vehicle and a law of c reference wheel corresponding to a maximum speed of the vehicle, - comparing the actual angular command defined by the steering wheel to the reference threshold angular value, - calculating a corrective coefficient of displacement of the pump on the basis of the real speed, situated between the speed minimum and the maximum speed, by interpolation on a segment connecting the reference control law corresponding to the minimum speed and the reference control law corresponding to the maximum speed, which segment is located respectively on either side of the value angular reference threshold depending on whether the actual angular control is lower or higher than the reference threshold angular value. Alternatively, said computer is further configured to determine a parallelism coefficient, which is applied to control laws determining the displacement of each of the left and right pumps so as to compensate for structural asymmetries of the system. PRESENTATION OF THE FIGURES Other features, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which should be read with reference to the accompanying drawings, in which: FIG. 1 shows schematically one transmission per side for a vehicle; FIGS. 2 and 3 show two laws controlling the displacement of the left and right pumps as a function of the angular control applied by the user, respectively when the speed control is at minimum speed, which minimum speed can be zero speed , and when the speed control is equal to a speed Vmax which corresponds to a maximum speed taken into account for calculations of corrective coefficients of displacement, even if the vehicle can go faster; FIG. 4 diagrammatically represents the method of calculating and applying the displacement controls according to one aspect of the invention; and FIG. 5 represents a control law of the displacement of the right pump when the speed control is equal to a speed such that the drive of the pumps always remain in the same direction whatever the angular command requested by the steering wheel. compared to the control laws of the displacement of the same right pump shown in FIGS. 2 and 3, shown in FIG. 5, respectively when the speed control corresponds to the minimum speed and when the speed control corresponds to the maximum speed. . DETAILED DESCRIPTION Figure 1 schematically shows a transmission per side for a vehicle.

This figure shows two crawler trains, respectively a left crawler 1 and a crawler 2. It is well understood that the crawlers are represented by way of example, and that the following description also applies to a wheeled vehicle. having one transmission per side. Each crawler has a clean transmission system, shown here for the left crawler 1 by a left transmission comprising: - a left drive chain 11, - A left hydraulic motor 12, - A left hydraulic pump 13 feeding the left hydraulic motor 12 In the same way, the right crawler 2 is represented by a straight transmission comprising: a right drive chain 21, a right hydraulic motor 22, a right hydraulic pump 23 supplying the right hydraulic motor 22. A controller 3 Pilot the left and right transmissions, for example by controlling the displacement and the direction of operation of the hydraulic pumps 13 and 23. The hydraulic pumps left 13 and right 23 are here represented as being distinct elements. Other equivalent arrangements are of course possible, for example by means of a double displacement pump. The left and right hydraulic pumps 23 are typically identical. The computer 3 is connected to a steering wheel 4 and a pedal 5, respectively delivering an angular control and a speed control.

The computer 3 is configured to, depending on the angular control and the speed control applied by a user, control the left and right transmissions of the vehicle to obtain the desired behavior; trajectory in a straight line, slow or fast turn, or pivoting. The computer thus defines in particular the speed variations of the left transmission and the right transmission, these variations being more or less important according to the command applied.

The computer 3 is configured to take into account the speed of the vehicle when driving the left and right pumps, in particular to prevent a reversal of the direction of rotation of one of the transmissions of the vehicle while the latter moves to high speed. The computer 3 is configured to: define a reference threshold angular value CA1, define a reference control law corresponding to a minimum speed of the vehicle illustrated in FIG. 2 and a reference control law corresponding to a speed maximum vehicle illustrated in Figure 3, - compare the actual angular control defined by the flywheel to the reference threshold angular value CA1, - calculate a corrective coefficient of displacement of the pump on the basis of the actual speed, located between the minimum speed and the maximum speed, by interpolation on a segment connecting the reference control law corresponding to the minimum speed and the reference control law corresponding to the maximum speed, which segment is located respectively on either side of the angular value. reference threshold CA1 according to whether the actual angular command is less than or greater than the angular value the reference threshold.

This process will be detailed below with reference to FIG. 4. In order to ensure the parallelism between the left transmission and the right transmission of the vehicle, a parallelism coefficient is advantageously applied to correct a structural asymmetry, for example a difference in circumference between the tracks of the vehicle, a difference in diameter between the wheels, or different pumps or hydraulic motors between the right transmission and the left transmission of the vehicle.

FIGS. 2 and 3 show two laws controlling the displacement of the left 13 and right pumps 23, respectively C13 and C23, as a function of the angular control applied by the user. FIG. 2 represents a control law for the minimum speed which may be zero speed, and FIG. 3 represents a control law for the speed Vmax which corresponds to the maximum speed taken into account for the calculation. In practice, the vehicle can sometimes move at a speed greater than the speed Vmax, but the speed Vmax is the maximum speed taken into account for calculating the corrective coefficients even if the pedal corresponds to a higher speed control value. On each of the graphs, we represent the control law of the left hydraulic pump 13 and the right hydraulic pump 23.

The angular control is here expressed as a percentage. Null angular control corresponds to a straight line displacement. Negative values are arbitrarily chosen to correspond to a left-turn command, and positive values to correspond to a right-turn command. The cubic displacement of the hydraulic pumps is represented on the ordinate, here also in percentage. The negative values of displacements correspond to a reversal of the direction of circulation of the fluid in the pump, that is to say to a drive in reverse, as opposed to the positive values which correspond to a drive forward for the transmission considered. .

FIG. 2 represents an example of a control law of the left 13 and right pumps 23 for zero speed control. As can be seen in FIG. 2, for zero angular control, the two left 13 and right 23 pumps are of equal displacement, which corresponds fictitiously to a displacement in a straight line, in fact the vehicle remaining stationary if the speed control overall vehicle is zero.

When the angular control is non-zero, the displacements are unequal. This allows the machine to turn off. We take the example of a turn command to the right, here corresponding to a positive angular command.

The displacement of the left pump 13 remains constant, here equal to a value CL less than the maximum displacement of said left and right pumps 23, while the displacement of the right pump 23 decreases progressively from the point A, which causes a vehicle turn, which is increasingly marked as the angular control increases. According to FIG. 2, at the angular value CA1, the displacement of the right pump 23 is zero, corresponding to point B. When the angular control is beyond the threshold angular value CA1, the right pump 23 changes direction of operation , which corresponds to a drive of the crawler (or wheels) right 2 of the vehicle in reverse, and allows a pivoting of the vehicle. When the angular control is at 100%, that is to say at its maximum, we are at point C of the control curve, the two pumps are equal in displacement but in reversed directions of operation, and provided that By entering the parameters A and C, the user has chosen A = -C, the two tracks (or if necessary the wheels) and turn at the same speed but in the opposite direction. The pump displacement can therefore be positive or negative depending on the choice of parameters by the user. Point C can be above or below zero. When the angular control is equal to the threshold angular value CA1, the right pump 23 is zero displacement. The same reasoning applies by symmetry for a left turn. This results in a turn of the variable vehicle as a function of the applied angular control, with a vehicle pivoting function performed when the angular control is greater than a given threshold angular value. The following points are defined in this figure: Point A, with coordinates [0; CL (more generally a coefficient less than or equal to 100% chosen by the user)]; - Point B, coordinates [CA1 (more generally an angle between 0 and 100% of the capabilities of the steering wheel, chosen by the user); 01; 25 - Point C, coordinates [100% of the capabilities of the steering wheel; -CL (more generally a positive or negative coefficient less than or equal to 100% chosen by the user)]. Note: the user can choose C at his or her discretion, he can choose it so that he never has a reversal of meaning. He can choose it positive or negative.

The two segments [AB] and [BC] therefore have distinct slopes, representing the modification of the velocity law beyond a threshold angular command CA1.

FIG. 3 represents a control law of the left 13 and right pumps 23 when the speed command is greater than or equal to the maximum speed control threshold value V max that is taken into account in the calculation.

As seen in this figure, the control law of the displacement of the left 13 and right pumps 23 is different from that shown in Figure 2. When the angular control is non-zero, the displacements are unequal. Here we also take the example of a right-turn command, here corresponding to a positive angular command. The same reasoning applies by symmetry for a left turn. The cubic capacity of the left pump 13 remains constant, here equal to its maximum value F. The displacement of the right pump 23 decreases progressively, here linearly up to the threshold angular value CA1 where it reaches a value Y1, from which it continues to decrease but more rapidly, that is to say linearly but with a steeper slope until it reaches a value Y2 less than Y1 and greater than zero. When the angular control is at 100%, that is to say at its maximum, the right pump 23 keeps a non-zero and positive displacement, that is to say that the crawler (or wheels) right 2 continues to turn in the same direction as the left crawler 1, but at a lower speed. This displacement value given by point E must be greater than or equal to that of point C, if C is positive.

Note: Theoretically, E could be negative also, if located above C. In practice, this point E being for a maximum speed of the machine, it is desirable to avoid it in general. However, it can be considered for existing slow working machines.

The following points are defined in this FIG. 3: Point F, with coordinates [0; 100%]; Point D, of coordinates [CA1; Y1 (more generally a coefficient of displacement chosen by the user, between 0% and 100% inclusive)]; - Point E, coordinates [100% of the angular capacity of the steering wheel; Y2 (more generally a coefficient of displacement chosen by the user, positive or negative, but which must be greater than or equal to C)].

As for FIG. 2, the two segments [FD] and [DE] therefore have distinct slopes, representing the modification of the speed law beyond a threshold angular control CAl.

This control law of the left and right transmissions which varies according to the speed of the vehicle thus makes it possible to ensure that the angular control applied by the user does not cause a reversal of the direction of the transmission of one of the sides. the vehicle is moving at a high speed, especially if E is positive. For very slow machines, E can be chosen negative. For fast machines, E must be advantageously chosen positive. Choosing a positive and fairly high E value can eliminate any risk of machine rollover during high speed turns. This is determined by the parameters of the machine, for example its type, use, maximum speed and stability, which can vary for example depending on the load transported.

It will be understood that FIGS. 2 and 3 represent the control laws for two extreme speed values, corresponding, for example, respectively to the minimum speed of the vehicle and to its maximum speed.

Intermediate control laws between these two laws represented in FIGS. 2 and 3 are defined for the intermediate speeds. It is thus clear that there exists a speed control threshold value beyond which the two pumps always have a displacement. positive, that is to say, always work in the same direction. This threshold value is the speed value corresponding to the control law for which the point L has a zero ordinate. The corresponding control law is represented under the reference I in FIG.

Figure 4 shows schematically the method of calculating and applying the displacement controls. Two hydraulic pumps 13 and 23 are referred to as P1 and P2. Once the process is started (step E0), the first step (E1) consists in identifying whether or not the angular control applied is lower than the threshold angular value. reference. The absolute value of the command applied to the reference threshold angular value is compared in order to determine on which portion of the control laws one is. It is determined (steps E2 and E'2) in the first place the displacement control for the pump which remains at constant displacement, the right pump 23 in the case of a right turn, and the left pump 13 in the case of a left turn. This is done by interpolation of the actual speed on the AF segment.

Next, the cubic capacity control for the pump whose displacement is modified, which is identified by P2, is determined (steps E3, E4, E5, E'3, E'4 and E'5). For this purpose, for the given angular control, an interval of values in which the displacement control is included is determined. For example, for angular control greater than the reference threshold angular value, for a given angular control, this interval is defined by the ordinate of the projection of the angular control on the segment [BC] corresponding to the point P (step E3 ), and by the ordinate of the projection of the angular control on the segment [DE] corresponding to the point Q (step E4). The displacement control is then determined as a function of the vehicle speed (step E5) by interpolation of the actual speed on the PQ segment. Similarly, for an angular control less than the reference threshold angular value, for a given angular control, this interval is defined by the ordinate of the projection of the angular control on the segment [AB] corresponding to the point M (step E '3), and by the ordinate of the projection of the angular control on the segment [FD] corresponding to the point N (step E'4). The displacement control is then determined as a function of the vehicle speed (step E'5) by interpolation of the actual speed on the segment MN. Once the displacement controls for the two pumps determined, it is checked whether the angular control applied is zero or not (step E6).

If the angular control is zero, the displacement controls are applied to the left and right pumps, which operate in the same direction. The displacement controls are then identical, where appropriate to a coefficient of parallelism as defined above. If the angular control is non-zero, it is determined which side the vehicle should turn (step E8). We take the example of a right turn, a similar reasoning applying for a left turn. It is then determined whether the displacement control of the right pump is negative (step E9). If this is the case, it reverses its direction of operation (step E92). Otherwise, both left and right pumps operate in the same direction (step E91). The displacement controls are then applied to the two right and left pumps (step E93), before the end of the process (step E10).

The present invention thus makes it possible to carry out a control for a vehicle with side transmission by means of a speed pedal and a steering wheel, by preventing a reversal of direction at a high speed which would be dangerous for a user.

FIG. 5 shows an exemplary law for controlling the displacement of the right pump when the speed command is equal to a speed control threshold value for which the displacement remains always positive, or even zero, whatever the angular control value. FIG. 5 also shows the control law of the displacement of the same right pump illustrated in FIG. 2 when the speed control is minimal and under the reference III the control law of the displacement of the engine of the engine. right pump illustrated in Figure 3 when the speed control is maximum.

The control laws applicable to the left pump are symmetrical to those shown in Figure 5 relative to the ordinate axis.

This control law I corresponds to a constant control value, between A and F, for a zero or negative angle, a value that decreases progressively, for example linearly, for an angle between 0 and CA1 and a value that also changes. progressively, in this case gradually decreases, but with a higher slope, for an angle between CA1 and 100%. For an angle CA1 the control value is K, positive. For an angle of 100%, the control value referenced L in FIG. 5 is zero. For a speed control lower than the speed control value corresponding to the curve I, that is to say a speed control which changes between J and A, the threshold angular value which determines a drive reversal of a pump, is between 100% and CA1.

The system according to the invention is programmed to define the control law (more precisely the correction coefficient) which corresponds to the real speed and the real rotation angle of the vehicle on the basis of laws II and III. As indicated above, for this the computer 3 calculates on an MN segment or on a PQ segment as the case, that is to say according to whether the applied angular control is less than or greater than the reference threshold angular value. Thus, the system according to the invention is programmed to define the control law on the basis of the following predefined characteristic points: A (which corresponds to the corrective coefficient to be applied to the cubic capacity defined elsewhere, for a displacement in a straight line at minimum or zero speed),. F (which corresponds to the corrective coefficient to be applied to the displacement in a straight line at maximum real speed greater than or equal to the value Vmax taken into account in the calculations (this value is fixed at 100%)),. B (which corresponds to the point of inflection of the minimum speed control curve to the reference threshold angular value, for example for an angle at which the displacement is zero),. D (which corresponds to the point of inflection of the maximum speed control curve for the same angle as B),. C (which corresponds to the corrective coefficient to be applied to the pump displacement defined elsewhere for an angle of 100% of the capacity of the flywheel, preferably symmetrical to A, minimum speed), this value can be zero or negative,. E (which corresponds to the corrective coefficient to be applied to the cubic capacity for an angle of 100%, at maximum speed greater than or equal to Vmax). E must be greater than or equal to C. It can be positive or negative, and therefore between C and 100%. The following singular points are also recalled which result from a calculation from curves II and III, for a particular parameterization: J (which corresponds for an instantaneous speed of the machine, between 0 and Vmax, measured in real time in a straight line to the corrective coefficient to be applied to the pump capacity defined elsewhere),. K (which corresponds to the point of inflection of the control curve for an instantaneous speed of the machine, between 0 and Vmax, measured in real time for the same angle as B), and. L (which corresponds to the corrective coefficient to be applied to the pump displacement defined elsewhere for an angle of 100%, control for an instantaneous speed of the machine, between 0 and Vmax, measured in real time).

K L are calculated according to the real speed of the machine, to be located between the curves II and III. They are located on right segments, and are placed proportionally.

The system defines the slopes of the control law on the basis of the aforementioned points A, B, C and D, E, F. Preferably according to the invention there is also provided means allowing the user to modify at will, that is to say to parameterize or personalize each of the points A, B, C, D, E and F, and / or alternatively the corresponding regulation slopes, and if necessary the coefficients of parallelism and the limit for the Vmax speed calculation, in order to configure the system optimally according to the desired evolutions. 20

Claims (18)

REVENDICATIONS1. A method of controlling the drive of a vehicle having a right transmission for its right side and a left transmission for its left side, said right and left transmissions being each powered by a variable displacement pump, respectively a right pump (23) and a left pump (13), in which said pumps are driven by a computer applying (3) a control law to each of said pumps (13, 23) defined as a function of: the maximum displacement of each of the pumps, a speed control, an angular command, in which a speed command is defined by means of a pedal and an angular command by means of a steering wheel; a reference threshold angular value is defined; a reference control law corresponding to a minimum speed of the vehicle and a reference control law corresponding to a maximum speed of the vehicle, - the angular command it is defined by the flywheel at the reference threshold angular value, - a corrective coefficient of displacement of the pump is calculated on the basis of the real speed, situated between the minimum speed and the maximum speed, by interpolation on a segment connecting the law of reference command corresponding to the minimum speed and the reference control law corresponding to the maximum speed, which segment is located respectively on either side of the reference threshold angular value depending on whether the actual angular control is less than or greater than the reference threshold angular value. 2. Method according to claim 1, wherein a coefficient of parallelism is determined, which is applied to the control laws determining the displacement of each of the left (13) and right (23) pumps so as to compensate for structural asymmetries of the system. . 3. Method according to one of claims 1 or 2, characterized in that when the angular control is non-zero, the displacement of the pump 10 (13, 23) located outside the required turn remains constant, while the The displacement of the pump (23, 13) inside the turn decreases gradually, at least to zero displacement. 4. Method according to one of claims 1 to 3, characterized in that at minimum speed and maximum angle of rotation, the two pumps (13, 23) are equal in displacement but in opposite directions. 5. Method according to one of claims 1 to 4, characterized in that at minimum speed, the pump located inside the turn is zero displacement when the angular control is equal to the reference threshold angular value. 6. Method according to one of claims 1 to 5, characterized in that for a non-zero angular value, the displacement of one of the pumps 25 decreases gradually, preferably linearly, to a point of inflection which corresponds to the reference threshold angular value, from which the displacement continues to evolve but more rapidly, preferably linearly, until reaching a final value for a maximum angular value. 30 7. Method according to one of claims 1 to 6, characterized in that for a speed between the minimum speed and the maximum speed, it implements a control law (I) for which the displacement is zero when the speed is Max. 8. Method according to one of claims 1 to 7, characterized in that it comprises a step of setting the characteristic points of the control laws. 9. The method according to claim 8, characterized in that the parameterizing step comprises the parameterization of at least one of the following characteristic points: To which corresponds to the cubic capacity in a straight line at minimum speed,. F which corresponds to the displacement in a straight line at maximum speed, preferably equal to the maximum displacement of the pumps, B which corresponds to a point of inflection of the minimum speed reference control curve, to the reference threshold angular value,. D which corresponds to the point of inflection of the maximum speed reference control curve, to the reference threshold angular value,. C which corresponds to the displacement for an angle of 100%, preferably symmetrical of A, at minimum speed, 20. E which corresponds to the displacement for an angle of 100%, at maximum speed. 10. Method according to one of claims 8 or 9, characterized in that the parametering step comprises the parameterization of a maximum speed value (Vmax) taken into account to apply the reference control law to a speed vehicle, used to calculate the pump displacement correction coefficient based on the actual speed, even if the vehicle can go faster. 30 11. Method according to one of claims 8 to 10, characterized in that the parametering step comprises the parameterization of a coefficient of parallelism. 12. Method according to one of claims 8 to 11, characterized in that the parameterization step comprises the parameterization of an interpolation coefficient implemented during the interpolation on segments connecting the reference control law. corresponding to the minimum speed and the reference control law corresponding to the maximum speed, situated respectively on either side of the reference threshold angular value depending on whether the actual angular command is lower or higher than the reference threshold angular value. , is a linear interpolation. 13. Method according to one of claims 1 to 12, characterized in that the interpolation on segments connecting the reference control law corresponding to the minimum speed and the reference control law corresponding to the maximum speed, respectively located on either side of the reference threshold angular value depending on whether the actual angular command is lower or higher than the reference threshold angular value, is a linear interpolation. 14. Method according to one of claims 1 to 13, characterized in that the minimum speed corresponding to the minimum speed reference control law of the vehicle is a zero forward speed, for controlling a pivoting of the vehicle on him -Even if the angular control exceeds a threshold. 15. Method according to one of claims 1 to 14, characterized in that the speed control is compared with a speed control threshold value, if the control speed is greater than or equal to said control threshold value. of speed, a control law is applied to said right and left transmissions so that they operate in the same drive direction, - if the control speed is lower than said speed control threshold value, a control law to said right and left transmissions so that for an angular control whose absolute value is greater than or equal to the reference threshold angular value (CA1), said right and left transmissions operate in reverse drive directions. 16. The method of claim 15, characterized in that it exploits a speed control threshold value (I) for which the control law imposes the same direction of drive to the two pumps (13, 23) whatever the angular control and for speed values below this speed control threshold value, it is possible to drive the pumps in opposite directions. A vehicle drive control system, comprising a right transmission for its right side and a left transmission for its left side, said right and left transmissions being each powered by a variable displacement pump, respectively a right pump. (23) and a left pump (13), said system further comprising a computer (3) configured to control said pumps (13, 23) by applying (3) a control law to each of said pumps (13). , 23) defined according to: - the maximum displacement of each of the pumps, - a speed control, - an angular control, the system comprising a pedal (5) defining a speed control and a steering wheel (4) defining a control angular, the computer (3) being furthermore configured so as to define a reference threshold angular value, to define a reference control law corresponding to a minimum speed of the vehicle ule and a reference control law corresponding to a maximum speed of the vehicle, - compare the actual angular control defined by the steering wheel to the reference threshold angular value, - calculate a corrective coefficient of displacement of the pump on the basis of the actual speed , between the minimum speed and the maximum speed, by interpolation on a segment connecting the reference control law corresponding to the minimum speed and the reference control law corresponding to the maximum speed, which segment is respectively located on the other than the reference threshold angular value depending on whether the actual angular command is less than or greater than the reference threshold angular value. The system of claim 17, wherein said computer (3) is further configured to determine a parallelism coefficient, which is applied to the control laws determining the displacement of each of the left (13) and right (23) pumps. ) to compensate for structural asymmetries in the system.