WORK VEHICLE WITH WHEELS AND CONTROL METHOD FOR CONTROLLING A STEERING ACTUATOR IN THIS WORK VEHICLE WITH WHEELS

Description

Domaine technique

[0001] The invention relates to the field of mobile work vehicles comprising at least two steering wheels, a lifting arm, and a steering control system. In particular, the invention relates to a load-handling vehicle such as a telescopic handler. Arrière-plan technologique

[0002] Work vehicles, especially load handling vehicles, are generally equipped with a steering wheel allowing an operator to control a steering movement of the wheels.

[0003] However, steering the wheels can affect vehicle stability, particularly lateral stability. Turning the wheels too quickly can cause the vehicle to roll over. A steering maneuver can therefore be dangerous or not, depending on factors that can affect vehicle stability, such as the vehicle's speed and the position of the lifting arm. These are factors that must be considered when performing steering maneuvers.

[0004] US20060180381 A1 describes a container handling vehicle comprising a computing unit configured to determine steering movement limitations based on various operational parameters. Résumé

[0005] One idea behind the invention is to provide a steering control system that preserves the stability of a work vehicle under various operating conditions, particularly during load handling operations, and that allows an operator to control the direction of the vehicle according to their needs.

[0006] To this end, according to one embodiment, the invention provides a mobile work vehicle comprising: a main body, a lifting arm movably mounted on the main body and intended for handling loads, a sensor configured to detect an orientation parameter of the lifting arm, a steering axle including at least two steering wheels, a steering actuator coupled to the steering wheels to modify a steering angle of the steering wheels, a steering control device actuable by an operator to produce a steering request signal, and a steering control system configured to receive the steering request signal and the orientation parameter of the lifting arm and to generate a steering setpoint signal representative of a steering angle of the steering wheels and intended to control the steering actuator, the steering control system including a filtering module configured to: determine a first ceiling of speed variation as a function of the orientation parameter of the lifting arm,generate the steering setpoint signal based on the steering request signal such that the rate of change of the steering setpoint signal does not exceed the first rate of change ceiling.

[0007] Thanks to these features, the first speed limit allows for a more or less rapid steering movement depending on the orientation of the lifting arm. The speed at which the steering wheel angle changes can thus be limited according to the lifting arm's orientation parameter, ensuring safe wheel steering.

[0008] According to embodiments, such a work vehicle may include one or more of the following characteristics.

[0009] According to one embodiment, the lifting arm orientation parameter includes an angle of the lifting arm.

[0010] According to one embodiment, the angle of the lifting arm is measured with respect to a reference frame chosen from the main body and the terrestrial reference frame.

[0011] The lifting arm orientation parameter can relate to one or more degrees of freedom of the lifting arm, for example, one degree of freedom in elevation about a horizontal axis and / or one degree of freedom in orientation about a vertical axis. In a preferred embodiment, the angle of the lifting arm is an angle of elevation about a horizontal axis.

[0012] According to one embodiment, the first speed variation ceiling decreases as the lifting arm's elevation angle increases.

[0013] According to one embodiment, the filtering module is further configured to: determine a direction of variation of the steering request signal between a direction of turning and a direction of return, determine the first ceiling of speed of variation as the first value of the ceiling when the direction of variation is the direction of turning and as the second value of the ceiling when the direction of variation is the direction of return, the second value of the ceiling being higher than the first value of the ceiling.

[0014] According to one embodiment, the filtering module is configured to: determine a minimum speed of variation among a speed of variation of the steering request signal and the first ceiling of speed of variation, generate the steering setpoint signal so that the speed of variation of the steering setpoint signal corresponds to the minimum speed of variation.

[0015] In one embodiment, the work vehicle includes a sensor for detecting the vehicle's speed. In said embodiment, the filtering module is further configured to: determine a second speed variation ceiling based on the vehicle's travel speed, generate the steering command signal based on the steering request signal so that a speed variation of the steering command signal does not exceed the second speed variation ceiling.

[0016] According to one embodiment, the second speed variation ceiling decreases as the walking speed increases.

[0017] According to one embodiment, the filtering module is further configured to: determine a direction of variation of the steering request signal between a direction of turning and a direction of return, determine the second ceiling of speed of variation as the third ceiling value when the direction of variation is the direction of turning and as the fourth value of variation when the direction of variation is the direction of return, the fourth ceiling value being higher than the third ceiling value.

[0018] According to one embodiment, the filtering module is configured to: determine a minimum speed of change among a speed of change of the steering request signal, the first speed of change ceiling and the second speed of change ceiling, generate the steering setpoint signal so that the speed of change of the steering setpoint signal corresponds to the minimum speed of change.

[0019] In one embodiment, the work vehicle includes a sensor for detecting the vehicle's travel speed. According to said embodiment, the steering control system includes a renormalization module configured to: receive the steering request signal from the steering control unit, determine a multiplicative renormalization coefficient based on the vehicle's travel speed, generate a renormalized steering request signal based on the steering request signal and the renormalization coefficient, provide the renormalized steering request signal to the filtering module.

[0020] According to one embodiment, the multiplicative renormalization coefficient decreases as walking speed increases.

[0021] According to one embodiment, the multiplicative renormalization coefficient reaches a plateau from a threshold vehicle speed.

[0022] In one embodiment, the threshold speed is a parameter configurable via a user interface. For example, the threshold speed is 20 kilometers per hour.

[0023] According to one embodiment, the values ​​of the renormalization coefficient, in particular the plateau value, are configurable using a user interface. For example, the plateau value is 25%.

[0024] According to one embodiment, the steering control system includes a correction module configured to: receive the steering request signal from the steering control unit, generate a steering request signal corrected by applying a gain function to the position signal, the gain function being a convex function.

[0025] In one embodiment, the work vehicle includes a sensor for detecting the vehicle's travel speed. In said embodiment, the steering control system includes a conversion module configured to: determine a steering angle ceiling based on the vehicle's travel speed, in which the steering angle ceiling decreases as travel speed increases, generate the steering setpoint signal by applying a capping law to said steering demand signal, such that the steering setpoint signal represents a steering angle value less than or equal to the steering angle ceiling.

[0026] According to a preferred embodiment, the steering control system includes a derivative proportional-integral (PID) controller.

[0027] According to one embodiment, the steering control system can be implemented in a distributed manner.

[0028] The steering control device can take various forms, such as a lever, a steering wheel, buttons, a touchscreen, etc. In a preferred embodiment, the steering control device is a joystick that can be operated by the operator's hand or finger. A steering device such as a joystick allows the operator to control the steering movement of the wheels without making large movements.

[0029] The steering lever does not offer as wide a range of motion as the steering wheel, which can raise issues related to the precision of the operator's control. However, the control system, particularly the filtering module, can be configured to prevent excessively abrupt movement of the steering lever from being fully transmitted to the steering actuator. Thus, the steering control system is advantageous both in terms of operator ergonomics and operational safety.

[0030] In one embodiment, the work vehicle has two steering axles, including at least four steering wheels. According to this embodiment, the steering actuator is coupled to the four steering wheels to modify the steering angle of the four steering wheels.

[0031] According to one embodiment, the invention also provides a control method for controlling a steering actuator in a mobile work vehicle, the work vehicle comprising a main body, a lifting arm movably mounted on the main body and intended for handling loads, a steering axle including at least two steering wheels, and said steering actuator coupled to the steering wheels to modify a steering angle of the steering wheels, the method comprising: receive a steering request signal from a steering control device operable by an operator, receive a lifting arm orientation parameter, determine a first speed of variation ceiling as a function of a lifting arm orientation parameter, generate a steering setpoint signal representative of a steering angle of the steering wheels as a function of the steering request signal so that a speed of variation of the steering setpoint signal does not exceed the first speed of variation ceiling, control the steering actuator as a function of the steering setpoint signal.

[0032] Such a method can be implemented by a unitary or distributed steering control system. The invention also provides a steering control system configured to implement this method. Brève description des figures

[0033] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings. [ Fig.1 ] There [ Fig.1 [ ] is a schematic side view of a rolling work vehicle in the form of a telescopic forklift truck to which a lifting arm is articulated according to one embodiment. Fig.2 ] There [ Fig.2 ] is a schematic perspective view of a steering control lever that can be used in the forklift of the [ Fig.1 ] according to one embodiment. [ Fig.3 ] There [ Fig.3 ] is a functional schematic representation of a steering control system that can be used in the forklift of the [ Fig.1 ] interacting with sensors, a steering control unit, and actuators according to one embodiment. Fig.4 ] There [ Fig.4 ] is a functional schematic representation of different modules that can be used in the steering control system of the [ Fig.3 ] according to one embodiment. [ Fig.5 ] There [ Fig.5 ] is a graphical representation of a gain function according to a particular embodiment. Fig.6 ] There [ Fig.6 ] is a graphical representation of a renormalization function according to a particular embodiment. Fig.7 ] There [ Fig.7 ] is a graphical representation of a first filtering function according to one embodiment. Fig.8 ] There [ Fig.8 ] is a graphical representation of a second filtering function according to one embodiment. Fig.9 ] There [ Fig.9 ] is a graphical representation illustrating the operation of a filtering module according to one embodiment. Fig.10 ] There [ Fig.10 ] is a graphical representation of a conversion function that converts a steering request signal into a wheel position signal, according to one embodiment. Fig.11 ] There [ Fig.11 ] is a graphical representation of a capping law that can be implemented in the conversion function of the [ Fig.10 ]. Description des modes de réalisation

[0034] There [ Fig.1 [ ] represents a work vehicle 1 in the form of a telescopic handler with a telescopic arm comprising a main body 2 mounted to roll on a front axle having two front wheels 5a and a rear axle having two rear wheels 5b. A lifting arm 4, shown here in the raised position, is mounted to pivot about a horizontal axis 23 arranged at the rear of the main body 2. The main body 2 is surmounted by a driver's cab 3 inside which an operator can be seated to drive the work vehicle 1 and control the actuation of the lifting arm 4.

[0035] The lifting arm 4 can be a telescopic arm with an adjustable length between a retracted and extended position. The lifting arm allows loads to be carried. A degree of rotational freedom between the main body 2 and the lifting arm 4 allows the lifting arm to be raised or lowered by means of a lifting cylinder (not shown). A tool 21 can be attached to a tool holder 25 on the lifting arm. In a preferred embodiment, the tool holder 25 can be designed to removably mount various handling tools such as forks, a jib, a bucket, or others. A digging cylinder 22 allows the tool 21 to be oriented relative to the lifting arm 4. A telescoping cylinder (not shown) allows the length of the telescopic arm to be adjusted.

[0036] The work vehicle 1 has at least one steering axle, for example, the front or rear axle. Alternatively, both axles are steerable, i.e., four-wheel steering. The work vehicle 1 is propelled by rotating wheels 5 in contact with the ground using a traction system, which will not be described in detail. The drive system can be internal combustion or electric. The transmission can be mechanical or hydraulic.

[0037] With reference to figures 2 à 11 will be described the structure and operation of a steering control system embedded in the work vehicle 1 to allow an operator to control steering movements of the steering wheels.

[0038] The operator can control the steering movements of wheels 5a and 5b using a steering lever 6 located in the cab 3, for example on an armrest 32 of an operator seat 31. The steering lever sends a position signal A to a steering control system 10.

[0039] The control system 10 generates a wheel position signal E which is transmitted to a steering actuator 12 coupled to the steering wheels to change the steering angle of the steering wheels and thus change the direction of travel of the vehicle 1. The steering angle is, for example, the same for all steering wheels. The steering actuator 12 is, for example, hydraulic or electric. A hydraulic distribution system 11 is used to control the steering actuator 12 in the case where the steering actuator 12 is hydraulic.

[0040] A walking speed sensor 7 is located on the work vehicle 1 and transmits a walking speed of the vehicle v to the steering control system 10.

[0041] An elevation angle sensor 8 is disposed on the lifting arm 4 and transmits an elevation angle value x of the lifting arm 4 measured between a plane of the main body 2 and the lifting arm 4, to the steering control system 10.

[0042] At least one elevation angle sensor 8 of the lifting arm 4 is disposed on the lifting arm 4 and transmits a value of said lifting arm orientation parameter x to the control system 10.

[0043] There [ Fig.2 [ ] represents the steering control lever 6. The steering control lever 6 is located inside the driver's cab 3 and consists of a handle mounted on a base, the handle being fixed to the base. The handle is connected to the base by a ball joint. The steering control lever 6 can be tilted in a transverse direction, the transverse direction being perpendicular to a direction of the seat arm. In a preferred embodiment, tilting the lever in the transverse direction allows control of the steering movement of the wheels.

[0044] The tilt direction of the steering lever 6, namely to the right as illustrated by arrow 18 or to the left as illustrated by arrow 19, indicates the direction of wheel steering. The tilt angle of the steering lever allows for quantitative control of the steering angle, via processing of the position signal A generated by the steering lever 6, as will be explained below.

[0045] There [ Fig.3 ] represents a summary diagram of the elements enabling the steering movement and the interaction of said elements with each other according to an embodiment.

[0046] The steering lever 6 generates a position signal A. The speed sensor 7 measures the vehicle's travel speed v. The lift angle sensor 8 measures the lift angle x. A wheel angle sensor 9 measures the angular position of the wheels.

[0047] The position signal A, the vehicle's travel speed v, the lifting arm's angle x, and the angular position of the wheels are processed by the steering control system 10, which generates a wheel position signal E, representing a new wheel position angle. This wheel position signal E is transmitted to a hydraulic control valve system 11, and then to a front actuator 12a and a rear actuator 12b, which control the steering movement of the wheels.

[0048] The wheel position signal E is calculated every 10 milliseconds and transmitted to the hydraulic control valve system 11 every 20 milliseconds, giving the operator an impression of immediacy, namely real-time control.

[0049] There [ Fig.4 [ ] represents modules comprising the control system 10 and their interactions. A correction module 101 receives the position signal A as input and returns a corrected demand signal B as output. A renormalization module 102 receives the corrected demand signal B as input and returns a renormalized demand signal C as output. A filtering module 103 receives the renormalized demand signal C as input and returns a filtered steering demand signal D as output. 104 is a conversion module, which takes a filtered steering demand signal D as input and returns a wheel position signal E as output.

[0050] The correction module 101 includes a gain function 51 which allows correction of the position signal A.

[0051] The renormalization module 102 includes a renormalization function 61 which returns a multiplicative normalization coefficient value αdepending on the vehicle's speed v.

[0052] The filtering module 103 evaluates a ceiling of a speed of variation of the steering angle as a function of the walking speed v and the elevation angle x of the lifting arm 4. The filtering module includes a first filtering function 70-71 dependent on the orientation parameter of the lifting arm x and a second filtering function 72-73 dependent on the walking speed v.

[0053] The conversion module 104 converts the filtered steering request signal D into the wheel position signal E and optionally applies a variable capping law to the wheel position signal E.

[0054] There [ Fig.5 ] represents the gain function 51 used in the correction module 101, according to one embodiment. The [ Fig.5 The x-axis represents the position signal A, expressed as a percentage. A value of 0% means that the steering lever 6 is vertical (default return position) and therefore no steering input is being made by the operator. A value of 100% means that the steering lever 6 is tilted to its maximum right or left. The gain function 51 is the same for right and left turn inputs.

[0055] The gain function 51 is convex and inferior to the identity function. The gain function 51 allows finer control of wheel movement for small-amplitude steering lever 6 movements.

[0056] There [ Fig.6 ] represents the renormalization function 61 used in the renormalization module 102.

[0057] The renormalization function 61 takes as input a vehicle speed v, represented on the x-axis and expressed in km / h, and returns a multiplicative renormalization coefficient α , dimensionless and expressed as a %, which is subsequently applied to the corrected steering request signal B and which corresponds to a maximum permitted steering request as a function of the vehicle's travel speed.

[0058] The renormalization function 61 is a decreasing and positive function.

[0059] One effect of the renormalization function 61 is to increase the sensitivity of the steering lever 6 over permissible angle ranges. Indeed, after the renormalization function 61 is applied, a maximum amplitude of movement of the steering control element 6 corresponds to a lower maximum steering input, which results in increased sensitivity.

[0060] There [ Fig.7 ] represents a first filtering function 68 dependent on the lifting arm's elevation angle. This first filtering function is used in the filtering module 103. The [ Fig.7 ] represents on the x-axis the angle of elevation x of the lifting arm 4, expressed in degrees and returns a first ceiling of speed of variation w, expressed in %.

[0061] The first filtering function is a low-pass filter. This first filtering function takes on a constant initial step value after a threshold angle is reached. The threshold angle value is 40° in the example shown.

[0062] The first filtering function 68 includes a first turning ceiling value 70 if the direction of change of the steering request signal is a turning direction, and a first return ceiling value 71 if the direction of change is a return direction. The first filtering function 68 returns a first speed ceiling.

[0063] The first return ceiling value 71 is higher than the first turn ceiling value 70, which has the effect of allowing the vehicle to straighten out faster than the turning speed.

[0064] There [ Fig.8 ] represents a second filtering function 69 dependent on the running speed v. Said second filtering function 69 is used in the filtering module 103. The [ Fig.8 ] represents on the x-axis the vehicle's walking speed v, expressed in km / h and returns a second speed variation ceiling w', expressed in %.

[0065] The second filtering function 69 is a low-pass filter. This second filtering function takes a second constant step value after a threshold walking speed is reached. The step value is 40 kilometers per hour in the example shown.

[0066] The second filtering function 69 includes a second turning ceiling value 72 if the direction of change of the steering request signal is the turning direction and a second return ceiling value 73 if the direction of change is the return direction, the second return ceiling value 73 being greater than the second turning ceiling value 72. The second filtering function 69 returns a second speed ceiling.

[0067] The operation of filter module 103 will now be explained with reference to the [ Fig.9 ].

[0068] There [ Fig.9 ] represents on the left an example of a renormalized demand signal C as a function of time and the corresponding filtered steering demand signal D, after processing by the filtering module 103.

[0069] The renormalized steering request signal C increases linearly with a first input slope 81 up to 20 milliseconds, then follows a second input slope 82 up to 60 milliseconds, and then remains constant thereafter. The second input slope 82 is lower than the first slope 81.

[0070] The filtering module 103 applies the speed of variation ceilings shown in the figures 8 et 9 to produce the filtered steering request signal D. The speed variation ceiling is a minimum value between the first speed ceiling, generated by the first filtering function, and the second speed ceiling, generated by the second filtering function. For example, if the speed variation ceiling is equal to 10%, then the first input slope 81 is higher than the speed variation ceiling and the second input slope 82 is lower than the speed variation ceiling.

[0071] Every 20 milliseconds, the filtering module 103 transmits a new filtered steering request signal D. Up to 40 milliseconds, the filtered steering request signal D follows a first output slope 91, which is equal to the maximum speed variation. Beyond this point, the filtered steering request signal D follows a second output slope 92, which is equal to the second input slope 82.

[0072] The operation of the 104 conversion module will now be explained with reference to figures 10 et 11 .

[0073] There [ Fig.10 ] represents a conversion function between the filtered steering request signal D and the wheel position signal E. The [ Fig.10 The x-axis represents the dimensionless, filtered steering input signal D, and the y-axis returns the wheel position signal E, expressed in degrees. The filtered steering input signal D takes algebraic values, with negative values ​​corresponding to a leftward steering input and positive values ​​corresponding to a rightward steering input. By convention, the filtered steering input signal D takes values ​​between -1000 and +1000. The conversion function is linear and takes both positive and negative angle values. Negative angle values ​​correspond to leftward steering, and positive angle values ​​correspond to rightward steering.

[0074] In this embodiment, the conversion module 104 implements a speed-dependent capping function. Specifically, the maximum steering angle value depends on the vehicle's speed. This maximum steering angle value is determined by applying a capping law represented in [ Fig.11 ]

[0075] There [ Fig.11 ] represents the law governing the maximum wheel angle as a function of the vehicle's speed. The [ Fig.11 The x-axis represents the filtered steering request signal D and the y-axis returns the wheel position signal E. Thresholds 41, 42, and 43 correspond to vehicle speed values ​​beyond which the slope of the limiting law is modified. The limiting law is decreasing, piecewise linear, and constant after a third threshold 43.

[0076] Alternatively, the conversion function implemented by the conversion module 104 could be independent of the walking speed, namely the capping law of the [ Fig.11 ] could be a constant function.

[0077] Alternatively, the lifting arm 4 may not be telescopic.

[0078] Alternatively, there may be two steering actuators, a first actuator 12a being coupled to the front wheels 5a and a second actuator 12b being coupled to the rear wheels 5b.

[0079] Alternatively, the gain function 51 can be piecewise affine, polynomial, exponential, etc.

[0080] Alternatively, the renormalization function 61 can be affine, piecewise affine, polynomial, exponentially decreasing, etc.

[0081] Alternatively, the control system 10 may also include fewer steering request signal processing functions and / or other functions. For example, one or more modules from the correction module 101 and the renormalization module 102 could be omitted. The second filtering function 72-73 of the filtering module 103 could be omitted. Some modules of the control system could be arranged in a different order than shown.

[0082] Preferably, the control system 10 includes a user interface (not shown) that allows configuration of the parameter values ​​influencing the processing of the steering request signal, namely, for example: the values ​​of the gain function 51 implemented by the correction module 101, the values ​​of the renormalization function 61 implemented by the renormalization module 102, the values ​​of the first and second filtering functions implemented by the filtering module 103, the values ​​of the capping law implemented by the conversion module 104.

[0083] The steering control system described above is primarily intended to ensure the safe operation of the mobile work vehicle during handling operations. It is possible that another steering control system could be used in other situations, for example, when the work vehicle is traveling on public roads, if such travel is permitted.

[0084] We have described a telescopic arm load handling trolley, but the steering control system can be applied to another wheeled work vehicle with a lifting arm, for example a rotating turret loader, a bucket loader or other.

[0085] Alternatively, in addition to or instead of the lift arm elevation angle sensor, other lift arm orientation parameters can be measured and taken into account by the steering control system, for example, an angle of orientation of the arm in an azimuthal direction relative to the longitudinal direction of the vehicle.

[0086] Some of the elements shown, particularly control system 10, can be implemented in various forms, either individually or in a distributed manner, using hardware and / or software components. Usable hardware components include ASICs (Automatic System Integrated Circuits), FPGAs (Field Programmable Gate Arrays), and microprocessors. Software components can be written in various programming languages, such as C, C++, Java, or VHDL. This list is not exhaustive.

[0087] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention as defined by the claims.

[0088] The use of the verb "comporter", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0089] In claims, any reference sign in parentheses should not be interpreted as a limitation of the claim.

Claims

1. A rolling work vehicle (1) comprising: a main body (2), a lifting arm (4) mounted to be movable on the main body (2) and intended to handle loads, a sensor (8) configured to detect an orientation parameter of the lifting arm (4), a steering axle including at least two steering wheels (5), a turning actuator (12) coupled to the steering wheels (5) to modify a turning angle of the steering wheels (5), a steering control member (6) that can be actuated by an operator to produce a turning request signal (A), and a steering control system (10) configured to receive the turning request signal (A) and the orientation parameter of the lifting arm and to generate a turning setpoint signal (D, E) representative of a turning angle of the steering wheels and intended to drive the turning actuator (12), characterized in that the steering control system (10) comprises a filtering module (103) configured to: determine a direction of variation of the turning request signal (A) out of a turn direction and a reverse direction, determine a first rate-of-variation cap as a function of the lifting arm orientation parameter, the first rate-of-variation cap being determined as first cap value when the direction of variation is the direction of turn to increase the turning angle and as second cap value when the direction of variation is the reverse direction to reduce the turning angle, the second cap value being higher than the first cap value, generate the turning setpoint signal (D, E) as a function of the turning request signal (A) such that a rate of variation of the turning setpoint signal does not exceed the first rate-of-variation cap.

2. The work vehicle as claimed in claim 1, wherein the lifting arm orientation parameter comprises a lifting arm angle.

3. The work vehicle as claimed in claim 2, wherein the angle of the lifting arm is an elevation angle about a horizontal axis.

4. The work vehicle as claimed in claim 3, wherein the first rate-of-variation cap decreases when the elevation angle of the lifting arm increases.

5. The vehicle as claimed in one of claims 1 to 4, wherein the filtering module (103) is configured to: determine a minimum rate of variation out of a rate of variation of the turning request signal and the first rate-of-variation cap, generate the turning setpoint signal (D, E) such that the rate of variation of the turning setpoint signal (D, E) corresponds to the minimum rate of variation.

6. The work vehicle as claimed in one of the preceding claims, comprising a sensor (7) for detecting a speed of movement (v) of the vehicle and wherein the filtering module (103) is further configured to: determine a second rate-of-variation cap as a function of the speed of movement of the vehicle, generate the turning setpoint signal (D, E) as a function of the turning request signal (A) such that a rate of variation of the turning setpoint signal (D, E) does not exceed the second rate-of-variation cap.

7. The work vehicle as claimed in claim 6, wherein the second rate-of-variation cap decreases when the speed of movement increases.

8. The work vehicle as claimed in claim 6 or 7, wherein the filtering module (103) is further configured to: determine a direction of variation of the turning request signal (A) out of a direction of turn to increase the turning angle and a reverse direction to reduce the turning angle, determine the second rate-of-variation cap as third cap value when the direction of variation is the direction of turn and as fourth variation value when the direction of variation is the reverse direction, the fourth cap value being higher than the third cap value.

9. The vehicle as claimed in one of claims 6 to 8, wherein the filtering module (103) is configured to: determine a minimum rate of variation out of a rate of variation of the turning request signal, the first rate-of-variation cap and the second rate-of-variation cap, generate the turning setpoint signal (D, E) such that the rate of variation of the turning setpoint signal (D, E) corresponds to the minimum rate of variation.

10. The work vehicle as claimed in one of the preceding claims, comprising a sensor (7) for detecting a speed of movement (v) of the vehicle and wherein the steering control system (10) comprises a renormalization module (102) configured to: receive the turning request signal (A) from the steering control member (6), determine a multiplying renormalization coefficient (61) as a function of the speed of movement (v) of the vehicle, generate a re-normalized turning request signal (C) as a function of the turning request signal (A) and of the multiplying renormalization coefficient (61), supply the re-normalized turning request signal (C) to the filtering module (103).

11. The work vehicle as claimed in claim 10, wherein the multiplying renormalization coefficient (61) decreases when the speed of movement (v) increases.

12. The work vehicle as claimed in one of the preceding claims, wherein the steering control system (10) comprises a correction module (101) configured to: receive the turning request signal (A) from the steering control member (6), generate a corrected turning request signal (B) by application of a gain function (51) to the turning request signal (A), the gain function (51) being a convex function.

13. The work vehicle as claimed in one of the preceding claims, comprising a sensor (7) for detecting a speed of movement (v) of the vehicle and wherein the steering control system (10) comprises a conversion module (104) configured to: determine a turning angle cap as a function of the speed of movement (v) of the vehicle, wherein the turning angle cap decreases when the speed of movement (v) increases, generate the turning setpoint signal (E) by application of a capping law to said turning request signal, such that the turning setpoint signal represents a turning angle value less than or equal to the turning angle cap.

14. The work vehicle as claimed in one of the preceding claims, wherein the steering control member (6) is a steering joystick that can be actuated by a hand or by a finger of the operator.

15. The work vehicle as claimed in one of the preceding claims, comprising two steering axles including at least four steering wheels (5), and wherein the turning actuator (12) is coupled to the four steering wheels to modify a turning angle of the four steering wheels.

16. A control method for controlling a turning actuator (12) in a rolling work vehicle (1), the work vehicle (1) comprising a main body (2), a lifting arm (4) mounted to be movable on the main body (2) and intended to handle loads, a steering axle including at least two steering wheels (5) and said turning actuator (12) coupled to the steering wheels (5) to modify a turning angle of the steering wheels, said method comprising: receiving a turning request signal (A) from a steering control member (6) that can be actuated by an operator, receiving an orientation parameter of the lifting arm, determining a direction of variation of the turning request signal (A) out of a direction of turn and a reverse direction, determining a first rate-of-variation cap as a function of an orientation parameter of the lifting arm, the first rate-of-variation cap being determined as first cap value when the direction of variation is the direction of turn to increase the turning angle and as second cap value when the direction of variation is the reverse direction to decrease the turning angle, the second cap value being higher than the first cap value, generating a turning setpoint signal (D, E) representative of a turning angle of the steering wheels as a function of the turning request signal (A) such that a rate of variation of the turning setpoint signal (D, E) does not exceed the first rate-of-variation cap, driving the turning actuator (12) as a function of the turning setpoint signal (D, E).