IL294716A - Rolling assembly comprising a towing vehicle and a trailer and method of controlling such a rolling assembly - Google Patents

Description

TITLE: Rolling assembly comprising a towing vehicle and a trailer and method of controlling such a rolling assembly The present invention relates to a rolling assembly comprising a towing vehicle and a trailer and a method for controlling such a rolling assembly. In the field of rolling assemblies comprising a towing vehicle and a trailer coupled to the towing vehicle, it is known to equip the trailer with drive wheels to assist in the maneuverability of the rolling assembly. It is known from DE 10 2019 202 781 A1 to control the trajectory of such a trailer by adapting the driving torque provided by each driving wheel of the trailer as a function, on the one hand, of the steering angle of the towing vehicle and, on the other hand, of the angle between the towing vehicle and the trailer, calculated from the rotation speed of the driving wheels of the trailer. However, such a rolling assembly cannot evolve in a complex environment, such as in an unstructured environment with many obstacles or in an environment with variable adhesion, because it does not allow to detect with precision the trajectory of the trailer. This is, in particular, prohibitive for a military vehicle equipped with a trailer and advancing over ground which can for example be very uneven during combat or after a bombardment. It is to these disadvantages that the invention more particularly intends to remedy by proposing an improved rolling assembly. To this end, the invention relates to a rolling assembly comprising at least: - a towing vehicle comprising at least two steerable wheels and a steering angle sensor for the steered wheels; and - a trailer configured to be coupled to the towing vehicle by means of a coupling, the trailer comprising at least two driving wheels, each driving wheel comprising an electric motor controlled by a control unit. According to the invention, the rolling assembly also comprises a device for measuring the angle of rotation of the trailer relative to the towing vehicle. In addition, the control unit is configured to correct the trajectory of the trailer by modifying the command to drive the electric motor of each driving wheel of the trailer as a function of the steering angle of the steered wheels of the towing vehicle and as a function of the angle of rotation of the trailer relative to the towing vehicle. Thanks to the invention, the measuring device makes it possible to know precisely the angle of rotation of the trailer relative to the towing vehicle, without having to resort to indirect calculations based on the rotation of the wheels, which could be distorted by loss 35 of adhesion. This makes it possible to correct the trajectory of the trailer, even in complex environments, when the adhesion of the trailer wheels is not stable. Indeed, since the angle of rotation of the trailer relative to the towing vehicle being measured, it does not depend on the speed of rotation of the trailer wheels, which in turn depends on the adhesion of these wheels to the ground. According to advantageous, but not obligatory aspects of the invention, this rolling assembly incorporates one or more of the following features, taken alone or in any technically permissible combination: - The device for measuring the angle of rotation of the trailer relative to the towing vehicle comprises at least two distance sensors, each distance sensor measuring a distance between the towing vehicle and the trailer, and the control unit calculates the angle of rotation of the trailer relative to the towing vehicle from the distances measured by the distance sensors of the measuring device. - The device for measuring the angle of rotation of the trailer relative to the towing vehicle comprises an angle sensor arranged in the coupling. According to another aspect, the invention also relates to a method for controlling a rolling assembly as described above, this controlling method comprising at least the following steps: a) measuring the steering angle of the steerable wheels of the towing vehicle of the rolling assembly; b) determining the trajectory of the towing vehicle; and c) measuring the angle of rotation of the trailer relative to the towing vehicle; d) determining the trajectory of the trailer of the rolling assembly; and e) correcting the trajectory of the trailer on the basis of the trajectories determined in steps b) and d). This controlling method induces the same advantages as mentioned above with respect to the rolling assembly of the invention. According to advantageous, but not obligatory aspects of the invention, this controlling method incorporates one or more of the following features, taken alone or in any technically permissible combination: - The controlling method is implemented when the rolling assembly is moving in reverse, so that the trailer anticipates the trajectory of the towing vehicle. - The controlling method is implemented when the rolling assembly is moving forward, so that the corridor in which the trailer is moving is identical to the corridor in which the towing vehicle is moving. 35 - The controlling method is implemented when the rolling assembly is moving in a straight line, to avoid yawing of the trailer. - In step e), the correction of the trajectory of the trailer is performed by the electric motor of each driving wheel by applying a driving torque or a braking torque to said driving wheel. - Steps a) to e) are implemented in real time by the control unit. - Steps a) to e) are implemented without the intervention of a driver of the towing vehicle of the rolling assembly. The invention will be better understood, and other advantages thereof will become clearer in the light of the following description of an embodiment of a rolling assembly and a method for controlling this rolling assembly, in accordance with the invention, given only by way of example and made with reference to the appended drawings in which: [Fig. 1] Figure 1 is a schematic representation of a rolling assembly in accordance with the invention, running in reverse; and [Fig. 2] Figure 2 is a schematic representation of the trajectory of the rolling assembly of Figure 1 running in forward motion. A rolling assembly 10 is shown in Figures 1 and 2. This rolling assembly 10 includes a towing vehicle 12. The towing vehicle 12 is an independent motorized vehicle, such as a car or a truck. The towing vehicle 12 comprises a chassis 14, a driving position 13 that comprises a steering wheel 132 and a driving seat 134, steerable wheels 16 controlled from the steering wheel 132, and non-steerable wheels 18. In the example shown in Figures 1 and 2, the towing vehicle 12 comprises two steerable wheels 16 and two non-steerable wheels 18. The wheels 16 are called "steerable" because they can turn, that is, be oriented, under the effect of a command received from the steering wheel 132, so as to modify the trajectory of the towing vehicle 12. Thus, a steering angle α of the towing vehicle 12 is defined, which corresponds to the angle formed between the direction in which the steerable wheels 16 are oriented and a direction parallel to a longitudinal axis X12 of the towing vehicle 12, which corresponds in practice to the direction of travel of the towing vehicle 12 when the towing vehicle is moving in a straight line. Thus, when the towing vehicle 12 is moving in a straight line, the angle α is zero. When the angle α is non-zero, then the towing vehicle 12 rotates in the direction of orientation of the steerable wheels 16. 35 The towing vehicle 12 comprises a steering angle sensor 20, which measures the angle α. The steering angle sensor 20 is, for example, a sensor measuring the orientation of the steering wheel 132 controlling the orientation of the steerable wheels 16, a sensor measuring a control signal sent to the steerable wheels 16, or a sensor measuring the angle of one of the steerable wheels 16 relative to the chassis 14. Advantageously, the steerable wheels 16 and/or the non-steerable wheels 18 are drive wheels of the towing vehicle 12. The drive wheels are then either connected to a motor, not shown, of the towing vehicle 12, or each include a motor, not shown, for example an electric motor. The towing vehicle 12 also comprises a control unit 22. The control unit 22 allows the towing vehicle 12 to be controlled based on steering commands provided by a driver of the towing vehicle, not shown. The control unit 22 is for example an on-board computer. Advantageously, the driver of the towing vehicle 12 providing controlling commands to the control unit 22 is physically installed on board the towing vehicle, in the cab of the driver 13. Alternatively, the driver can also control the towing vehicle 12 remotely, that is remotely control the towing vehicle 12. Advantageously, the control unit 22 can control the rotational speed of the drive wheels of the towing vehicle 12. In addition, the value of the angle α measured by the steering angle sensor 20 is transmitted to the control unit 22. In Figure 1, this transmission is shown by way of example via a data transmission cable 24. The rolling assembly 10 also comprises a trailer 30. The trailer 30 comprises a chassis 32 and drive wheels 34. In the example shown, the trailer 30 comprises two drive wheels 34. The wheels 34 are referred to as "drive wheels" because each wheel 34 comprises an electric motor 36 to deliver driving torque to the wheel. Thus, the trailer 30 comprises as many electric motors 36 as there are drive wheels 34. The trailer 30 is further coupled to the towing vehicle 12 by means of a coupling 38. The coupling 38 allows the trailer 30 to be mechanically linked to the towing vehicle 12, so that the towing vehicle 12, when moving forward or backward, drives the trailer 30.

The coupling 38 is, for example, a hitch hook, a hitch ball, or any manual or automatic system providing a mechanical connection between the towing vehicle and the trailer. Preferably, the coupling 38 also electrically connects the towing vehicle 12 to the trailer 30, in order to transmit, for example, electrical power and/or information. The electric motors 36 of the trailer 30 are controlled by the control unit 22. The control unit 22 exchanges data with each electric motor 36, for example to send commands to the electric motors 36, or to retrieve operating information from the electric motors 36, such as their rotational speed. The exchange of data between the control unit 22 and the electric motors 36 is carried out via an information transmission system, not shown. This information transmission system is, for example, a physical network, such as an electric cable, which passes through the coupling 38, or a wireless network, such as a secure radio link. When the towing vehicle 12 is in motion and the electric motors 36 of the drive wheels 34 of the trailer 30 are not in operation, the trailer 30 is pulled, in a known manner, by the towing vehicle 12. The trajectory of the trailer 30 is then passively dependent on the trajectory of the towing vehicle. When the electric motors 36 are turned on, the trajectory of the trailer 30 is then modified, so that it does not depend solely on the trajectory of the towing vehicle. Examples of such modification of the trajectory of the trailer 30 by the electric motors are detailed below. In practice, the electric motor 36 of a drive wheel 34 is used to apply torque to that drive wheel 34. The torque applied to the wheel 34 is either driving, that is, it accelerates the rotational speed of the wheel 34, or braking, that is, it slows the rotational speed of the wheel 34. A forward direction of travel of the rolling assembly 10 is defined as a direction of travel of the rolling assembly in which the towing vehicle 12 moves in the opposite direction of the trailer 30, that is, the towing vehicle pulls the trailer and does not push it. A direction of travel of the rolling assembly 10 in reverse is defined as a direction of travel of the rolling assembly in which the towing vehicle 12 advances in the direction of the trailer 30. In the remainder of the description, the terms "left" and "right" are understood as viewed from above and with respect to the direction of travel of the rolling assembly 10 in forward motion. 35 The rolling assembly further comprises a measuring device 50. This measuring device allows, together with the control unit 22, to measure the angle of rotation β of the trailer 30 relative to the towing vehicle 12. This angle of rotation β corresponds in practice to the angle formed between the longitudinal axis X30 of the trailer 30 and the longitudinal axis X12 of the towing vehicle 12. When the rolling assembly 10 is moving in a straight line, the angle of rotation β is zero. In the example embodiment of Figure 1, the device 50 comprises a first distance sensor 52, which comprises a transmitter 54 and a receiver 56, and a second distance sensor 58, which comprises a transmitter 60 and a receiver 62. In practice, the transmitters 54 and 60 are located at the rear of the towing vehicle 12, in other words, on the side of the towing vehicle 12 facing the trailer 30 and from which the coupling 38 extends. In practice, the receivers 56 and 62 are located at the front of the trailer 30, in other words, on the side of the trailer 30 facing the towing vehicle 12 and from which the coupling 38 extends. Thus, the transmitters 54 and 60 on the one hand and the receivers 56 and 62 on the other hand are located opposite each other. The first sensor 52 measures the distance between the transmitter 54 and the receiver 56, noted "L1", and the second sensor 58 measures the distance between the transmitter 60 and the receiver 62, noted "L2". Advantageously, the measurement of distance between a transmitter and a receiver is performed by causing the transmitter to emit a signal, such as an ultrasonic sound signal, or a light signal, then measuring the time to travel between the transmitter and the receiver. The distance between a transmitter and a receiver is then calculated from the measured time to travel and the propagation speed of the transmitted signal. In practice, as seen in Figure 1, the first sensor 52 is located on the left side of the rolling assembly 10 and the second sensor 58 is located on the right side of the rolling assembly. When the rolling assembly 10 is traveling in a straight line, in other words, when the steering angle α of the steerable wheels 16 of the towing vehicle 12 is zero, the distances L1 and L2 are equal. When the rolling assembly 10 makes a turn, in other words, when the steering angle α is non-zero, then the distances L1 and L2 are no longer equal. The distance L1 or L2 on the inside of the turn is then less than the distance L1 or L2 on the outside of the turn. 35 In the example shown in Figure 1, the distance L2 measured by the second sensor located on the right side of the rolling assembly 10, is less than the distance L1 measured by the first sensor 52 located on the left side of the rolling assembly 10, due to the steering angle of the steerable wheels 16. The distances L1 and L2 measured by the sensors 52 and 58 are transmitted to the control unit 22. In Figure 1, this transmission is shown for example, as a data cable 64. From the distance values L1 and L2 measured by the measuring device 50, and the dimensions of the towing vehicle 12 and the trailer 30, which are known, the control unit accurately calculates the angle of rotation β, of the trailer 30 relative to the towing vehicle 12. For example, when the rear face of the towing vehicle 12 is perpendicular to its longitudinal axis X12 and the front face of the trailer 30 is perpendicular to its longitudinal axis X30, the angle between these faces is equal to the angle β and the device 50 allows this angle to be measured quasi-directly. In the case where the rear face of the towing vehicle 12 is not perpendicular to its longitudinal axis X12 or the front face of the trailer 30 is not perpendicular to its longitudinal axis X30, the result of the measurement performed with the device 50 is adapted depending on the exact geometry of the rolling assembly. A calibration of the device can take place when the rolling assembly is moving in a straight line. It is advantageous to measure the angle of rotation β of the trailer 30 relative to the towing vehicle 12 using the measuring device 50, because the measurement obtained is then accurate and independent of the operating parameters of the trailer 30. In particular, this measurement is independent of the speed of rotation of the drive wheels 34 of the trailer 30, which is generally highly variable, particularly in a complex environment, and which therefore does not allow the angle β to be calculated accurately. By "complex medium" is meant any medium over which the rolling assembly travels that is unstructured, that is, has many obstacles such as bumps, holes, or rocks, or has variable traction, for example due to the presence of mud or ice. A complex environment can also be referred to as "rough terrain". Such an environment is found as soon as the rolling assembly 10 leaves the structured environment (roads, marked paths) or travels in degraded conditions of the structured environment (snowfall, deterioration of the roadway, ice, etc.). The trailer 30 is a so-called "self-supporting" trailer, in other words, the weight of the trailer 30 is mostly supported by the drive wheels 34, and the coupling 38 transmits only a small portion of the weight of the trailer 30 to the towing vehicle 12 according to the regulatory guidelines currently in effect. A method for controlling the rolling assembly 10 is now described in more detail. This method for controlling the rolling assembly 10 allows the trajectory of the trailer to be corrected, depending on the trajectory of the towing vehicle 12. In practice, the controlling method is carried out by the control unit 22 of the rolling assembly. To this end, the method for controlling the rolling assembly 10 comprises at least the following steps: a) A first step of measuring the steering angle α of the steerable wheels 16 of the towing vehicle 12. During this first step, the steering angle sensor 20 measures the steering angle α of the steerable wheels 16 of the towing vehicle unit 12, then transmits this measurement to the control unit 22. b) A second step of determining the trajectory of the towing vehicle 12 of the rolling assembly 10. During this second step, the control unit 22 detects whether the rolling assembly is moving forwards or backwards. This detection of the direction of travel is established, for example, depending on the direction of rotation of the wheels 16 and/or 18 of the towing vehicle 12. Then, still in the second step, the control unit 22 determines the trajectory of the towing vehicle 12, from the direction of travel of the rolling assembly 10, the speed of the towing vehicle 12 and the steering angle α of the steerable wheels 16 of the towing vehicle. c) A third step of measuring the angle of rotation β of the trailer 30 relative to the towing vehicle 12. In this third step, the measuring device 50 measures the distances L1 and L2 and then transmits these distance measurements to the control unit 22. Next, the control unit 22 calculates the angle of rotation β of the trailer 30 relative to the towing vehicle 12 as described above. Thus, the angle of rotation β is measured indirectly by the device 50. d) A fourth step of determining the trajectory of the trailer 30 of the rolling assembly 10. In this fourth step, the control unit 22 determines the trajectory of the trailer 30, from the trajectory of the towing vehicle 12 determined in step b) and the angle of rotation β of the trailer 30 determined in step c). 35 e) A fifth step of correcting the trajectory of the trailer 30 of the rolling assembly 10. In this fifth step, the control unit 22 corrects the trajectory of the trailer 30 based on the trajectory of the trailer determined in step d) and the trajectory of the towing vehicle determined in step b). The order of steps a) to e) of the controlling method may be different. In particular, steps b) and c) can be reversed so that the angles α and β are measured before determining the trajectories of the towing vehicle 12 and the trailer 30. Advantageously, the five steps a) to e) of the controlling method are executed cyclically, in real time, by the control unit 22. The frequency of iteration of steps a) to e) is a function of the speed of movement of the towing vehicle. Preferably, the trajectory correction carried out during the fifth step of the controlling method consists of modifying the trajectory of the trailer 30 so that this trajectory is identical to the trajectory of the towing vehicle 12. In practice, this correction of the trajectory of the trailer 30 is achieved by modifying the driving torques applied by the electric motors 36 to the drive wheels 34 of the trailer 30. Thus, the control unit 22 corrects the trajectory of the trailer 30 by modifying the drive command of the electric motor 36 of each drive wheel 34 of the trailer as a function of the steering angle α and angle of rotation β. Preferably, when the rolling assembly 10 is moving in a straight line, in other words, when no correction of the trajectory of the trailer 30 is required, the electric motors 36 deliver zero torque to the drive wheels 34. Thus, the movement of the trailer 30 is driven solely by the movement of the towing vehicle 12 and the wheels 34 rotate without being driven. Two examples of correcting the trajectory of the trailer 30 are shown in Figures and 2. In Figure 1, the rolling assembly 10 is moving in reverse, in that, the towing vehicle 12 is pushing the trailer 30 backwards. In addition, the steerable wheels 16 of the towing vehicle 12 are steered to the right, in other words, the towing vehicle turns to its right side. In other words, the trajectory of the towing vehicle 12 is similar to an arc of a circle whose center is located on the right side of the rolling assembly. In this example, during step e), the control unit 22 corrects the trajectory of the trailer by sending a corrected or modified steering command to the electric motors 36 leading to the application of a driving or braking torque to each drive wheel 34. These driving or braking torques are equivalent to applying a force to the drive wheels.

In the example, a force F1 is applied to the drive wheel 34 on the left side of the trailer 30 and a force F2 is applied to the drive wheel 34 on the right side of the trailer. To allow the trailer 30 to follow the trajectory of the towing vehicle 12, in other words, an arc of a circle whose center is located on the right of the rolling assembly, the torque applied to the left drive wheel is driving, in other words, the force F1 is directed in the direction of movement of the rolling assembly 10, leading this wheel to accelerate, and the torque applied to the right drive wheel to brake, in other words, the force F2 is directed opposite to the direction of movement of the rolling assembly, leading this wheel to slow down. Advantageously, the absolute value of the forces F1 and F2 is adapted by the control unit 22 to control the trajectory of the trailer 30 with precision. Thus, according to the correction to be applied to the trajectory of the trailer, the absolute value of the force F2 may be greater than, or equal to, the absolute value of the force F1 or vice versa depending on the adhesion encountered. The forces F1 and F2 lead the trailer 30 to turn to its right, so as to follow the same trajectory as the towing vehicle 12. The trailer 30 then anticipates the trajectory of the towing vehicle 12. As the rolling assembly 10 moves in reverse, the trailer 30 moves in front of the towing vehicle 12, in the direction of travel of the rolling assembly. Thus, the trailer 30 is said to anticipate the trajectory of the towing vehicle 12 because the trajectory of the trailer 30 is modified so that it moves in a corridor identical to the corridor that the towing vehicle will use, although the trailer uses this corridor before the towing vehicle. This controlling method is particularly advantageous when the rolling assembly is moving in reverse. Indeed, it is well known that maneuvering a trailer coupled to a towing vehicle in reverse is complex. Improper maneuvering of a rolling assembly in reverse can lead to jackknifing of the trailer, in other words, turning the trailer so that the orientation of the trailer is reversed. The controlling method of the invention therefore prevents such jackknifing. This is particularly important in the case where it is not possible to uncouple the trailer 30 from the towing vehicle 12 for a reverse maneuver, which is the case in a theater of military operations where the driver or passengers of the towing vehicle must not leave the vehicle, without being exposed to enemy fire. In Figure 2, the rolling assembly 10 moves forward, in other words, the towing vehicle 12 precedes the trailer 30 by pulling it.

In addition, the rolling assembly 10 follows a trajectory that consists of a turn to its left of approximately 90 degrees. To show this entire trajectory, the rolling assembly is shown simultaneously in three different positions. The first position corresponds to the start of the left turn of the rolling assembly 10. In this position, the rolling assembly is referenced as "10A". In the second position, the rolling assembly 10 is shown during its left turn. The steerable wheels 16 of the towing vehicle 12 are turned to the left. In this position, the rolling assembly is referred to as "10B". The third position corresponds to a straight-line trajectory, after the rolling assembly has completed its rotation to the left. In this position, the rolling assembly is referenced as "10C". The corridor C12 in which the towing vehicle 12 moves during its trajectory is shown by two continuous curves. The corridor C'30 in which the trailer 30 would move during its trajectory, in the case where the trajectory of the trailer 30 would not be corrected by the controlling method of the invention, is shown by two dotted curves. It can be seen that these two corridors are not superimposed, in other words, that without correction, the trajectory of the trailer 30 differs from the trajectory of the towing vehicle 12. In particular, the trajectory of the trailer 30 is shifted towards the inside of the turn, with respect to the trajectory of the towing vehicle 12. Thus, in this example of a rolling assembly 10 moving forward, the controlling method of the invention allows the trajectory of the trailer 30 to be corrected so that it is identical to the trajectory of the towing vehicle 12. Thanks to the controlling method of the invention, after correction of the trajectory of the trailer 30 by action of the electric motors 36 on the drive wheels 34, controlled by the control unit 22, the corridor C30 in which the trailer 30 moves is identical to the corridor Cin which the towing vehicle 12 moves. In another example, not shown, when the rolling assembly 10 is moving in a straight line, the electric motors 36 apply driving and braking torques to the wheels 34 so as to compensate for oscillations of the trailer 30 and keep the trailer 30 in a straight line. Such oscillations typically occur when the trailer assembly is traveling at high speeds and are commonly referred to as "yawing". Thanks to the controlling method of the invention and the accuracy of the measuring device 50, the trajectory of the trailer 30 is accurately corrected in real time so that it is identical to the trajectory of the towing vehicle 12, whether the rolling assembly 10 is moving forward or in reverse. Thus, the method for controlling the rolling assembly 10 described above is effective for controlling the rolling assembly 10, including in complex environments. Moreover, the controlling method of the invention is implemented independently by the control unit 22, without intervention of the driver of the towing vehicle 12, which is advantageous. This avoids, for example, complicating the driving of the rolling assembly 10. A driver who is not trained to maneuver trailers can then drive the rolling assembly 10 without any particular precautions, since the trajectory of the trailer 30 adapts independently to the steering of the towing vehicle. In one variant of the invention, not shown, the transmission of the angle value α from the angle sensor 20 to the control unit 22 is performed wirelessly, for example by radio link. In one variant of the invention, not shown, the towing vehicle 12 comprises a different number of steerable wheels 16, for example four steerable wheels 16. In one variant of the invention, not shown, the towing vehicle 12 comprises a different number of non-steerable wheels 18, for example four non-steerable wheels 18. In one variant of the invention, not shown, the towing vehicle 12 comprises only steerable wheels 16, for example four steerable wheels 16. In such a variant, the towing vehicle 12 comprises, for example, a front axle with steerable wheels and a rear axle with steerable wheels. The steerable wheels on the rear axle may be turned in the same or opposite direction to the steerable wheels on the front axle. In this variant, the driver of the towing vehicle 12 can then control the direction of the towing vehicle according to two distinct strategies: in a first strategy, the front axle wheels and the rear axle wheels are steered in two opposite directions, thereby reducing the turning radius of the towing vehicle; and in a second strategy, the front axle wheels and the rear axle wheels are steered in the same direction, for example being parallel to each other, thereby allowing the towing vehicle to crab. Preferably, when the towing vehicle 12 is moving in reverse according to this second strategy, then the trajectory of the trailer 30 is corrected using the drive wheels 34, based on the steering angles α and the angle of rotations β, so that the trailer follows a trajectory parallel to the trajectory according to which the towing vehicle is moving. In one variant of the invention, not shown, the steerable wheels 16 of the towing vehicle 12 are drive wheels. In one variant of the invention, not shown, the trailer 30 comprises a different number of drive wheels 34, for example four drive wheels 34. In such a variant, the towing vehicle 35 comprises, for example, a front axle with driving wheels and a rear axle with driving wheels. In this variant, the driver of the towing vehicle 12 can advantageously choose his mode of travel between three distinct modes of travel: in a first mode, only the wheels of the front axle contribute to the travel of the towing vehicle, the wheels of the rear axle then being followers; in a second mode, only the wheels of the rear axle contribute to the travel of the towing vehicle, the wheels of the front axle then being followers; in a third mode, the wheels of both the front and the rear axles contribute simultaneously to the travel of the towing vehicle. In one variant of the invention, not shown, the trailer 30 also comprises non-driving wheels, which do not comprise an electric motor. In one variant of the invention, not shown, the electric motors 36 that deliver driving torque to the drive wheels 34 are not in the wheels 34 and are connected to the wheels by a drive shaft. In this variant, a motor 36 is associated with a drive wheel 34, each drive wheel 34 is said to comprise an electric motor 36. In one variant of the invention, not shown, the receivers 56 and 62 are replaced by reflectors, so that the signals emitted by the transmitters 54 and 60 are reflected by the reflectors and then detected by the transmitters 54 and 60. Thus, the sensors 52 and measure the travel time of a round trip of a signal between the transmitter and the reflector. The distance between an emitter and a reflector is then calculated from the measured travel time and the propagation speed of the emitted signal. In one variant of the invention, not shown, the measuring device 50 comprises two sensors 52 and 58 without receivers, configured to measure respectively the distance Land the distance L2 only from a transmitter, for example by measuring the distance between a transmitter and the closest point of the trailer 30. In one variant of the invention, not shown, the device 50 for measuring the angle of rotation β of the trailer 30 relative to the towing vehicle 12 comprises an angle sensor arranged within the coupling 38, instead of the first sensor 52 and second sensor 58. In this case, the angle measurement is direct and does not require a calculator in the control unit 22. In one variant of the invention, not shown, the calculation of the angle β from the measurements made by the measuring device 50 is performed by a second control unit, separate from the control unit 22. Preferably, this second control unit is arranged in the trailer 30 and communicates with the control unit 22, either through a data cable or by wireless link. 35 In one variant of the invention, not shown, when the rolling assembly 10 is moving in a straight line, the electric motors 36 of the trailer 30 all deliver an identical driving torque to the drive wheels 34. Thus, in this variant, the trailer 30 is not merely towed by the towing vehicle 12, but actively contributes to the movement of the rolling assembly 10. This configuration is particularly advantageous for improving the performance of the rolling assembly 10, for example when the rolling assembly 10 is climbing a significant slope. In this variant, when a correction of the trajectory of the trailer 30 is required, for example when turning to the right in reverse, in a manner similar to the example of Figure 1, then the electric motors 36 each deliver a driving torque to the drive wheels 34, corresponding then to two forces F1 and F2 directed in the direction of travel of the rolling assembly 10, but of different absolute value. The difference in driving torque applied to the drive wheels 34 then makes it possible to turn the trailer 30 so as to correct its trajectory. Furthermore, such a correction also allows the trajectory of the trailer 30 to be stabilized when the rolling assembly 10 is moving in a straight line, to avoid yawing of the trailer. In one variant of the invention, not shown, when the rolling assembly 10 is traveling in a straight line and downhill, the electric motors 36 of the trailer 30 all deliver the same braking torque to the drive wheels 34 to help the rolling assembly 10 control its downhill speed. In this variant, when a correction of the trajectory of the trailer 30 is required, then the electric motors 36 each deliver a braking torque to the driving wheels 34, corresponding then to two forces F1 and F2 directed in the opposite direction to the direction of travel of the rolling assembly 10, but of different absolute value. The difference in braking torque applied to the drive wheels 34 then makes it possible to turn the trailer 30 so as to correct its trajectory. In addition, such a correction also stabilizes the trajectory of the trailer 30 when the rolling assembly 10 is traveling in a straight line, to avoid yawing of the trailer. Any feature described for one embodiment or variant in the foregoing may be implemented for the other embodiments and variants described above, so long as technically feasible.

Claims (10)

1.CLAIMS 1. A rolling assembly (10) comprising at least: - a towing vehicle (12) comprising at least two steerable wheels (16) and a steering angle ( α) sensor (20) for the steerable wheels; and - a trailer (30) configured to be coupled to the towing vehicle by a coupling (38), the trailer comprising at least two drive wheels (34), each drive wheel comprising an electric motor (36) controlled by a control unit (22), characterized in that the rolling assembly (10) also comprises a device (50) for measuring the angle of rotation ( β) of the trailer (30) relative to the towing vehicle (12), and in that the control unit is configured to correct the trajectory of the trailer (30) by modifying the command to drive the electric motor (36) of each driving wheel (34) of the trailer as a function of the steering angle ( α) of the steerable wheels (16) of the towing vehicle (12) and as a function of the angle of rotation ( β) of the trailer relative to the towing vehicle.

2. The rolling assembly (10) according to claim 1, characterized in that the device (50) for measuring the angle of rotation ( β) of the trailer (30) relative to the towing vehicle (12) comprises at least two distance sensors (52, 58), each distance sensor measuring a distance (L1, L2) between the towing vehicle and the trailer, and in that the control unit (22) calculates the angle of rotation ( β) of the trailer (30) relative to the towing vehicle (12) from the distances (L1, L2) measured by the distance sensors (52, 58) of the measuring device (50).

3. The rolling assembly (10) according to claim 1, characterized in that the device (50) for measuring the angle of rotation ( β) of the trailer (30) relative to the towing vehicle (12) comprises an angle sensor arranged within the coupling (38).

4. A method for controlling a rolling assembly (10) according to any of claims to 3, this controlling method comprising at least the following steps: a) measuring the steering angle ( α) of the steerable wheels (16) of the towing vehicle (12) of the rolling assembly (10); b) determining the trajectory of the towing vehicle (12); c) measuring the angle of rotation ( β) of the trailer (30) relative to the towing vehicle (12) 35 d) determining the trajectory of the trailer (30) of the rolling assembly (10); and e) correcting the trajectory of the trailer (30) based on the trajectories determined in steps b) and d).

5. The method for controlling a rolling assembly (10) according to claim 4, characterized in that the controlling method is implemented when the rolling assembly (10) is moving in reverse, so that the trailer (30) anticipates the trajectory of the towing vehicle (12).

6. The method for controlling a rolling assembly (10) according to claim 4, characterized in that the controlling method is implemented when the rolling assembly (10) is moving forward, so that the corridor (C30) in which the trailer (30) is moving is identical to the corridor (C12) in which the towing vehicle (12) is moving.

7. The method for controlling a rolling assembly (10) according to claim 4, characterized in that the controlling method is implemented when the rolling assembly (10) is moving in a straight line, to avoid yawing of the trailer (30).

8. The method for controlling a rolling assembly (10) according to any one of claims 4 to 7, characterized in that in step e), the correction of the trajectory of the trailer (30) is performed by the electric motor (36) of each drive wheel (34) by applying a driving torque or a braking torque to said driving wheel.

9. The method for controlling a rolling assembly (10) according to any one of claims 4 to 8, characterized in that steps a) to e) are implemented in real time by the control unit (22).

10. The method for controlling a rolling assembly (10) according to any one of claims 4 to 9, characterized in that steps a) to e) are implemented without intervention of a driver of the towing vehicle (12) of the rolling assembly (10).