Patent Application
20250178875
The invention relates to the field of rolling work vehicles comprising at least two steering wheels and a lifting arm and a steering control system. In particular, the invention relates to a load handling vehicle such as a power lift truck with telescopic arm.
Work vehicles, in particular load handling vehicles, are generally equipped with a steering wheel allowing an operator to control a wheel turning movement.
However, the turning of the wheels can affect the stability of the vehicle, in particular the lateral stability. An excessively fast turning of the wheels can culminate in the overturning of the vehicle. A turning movement can thus prove dangerous or not, depending on factors likely to affect the stability of the vehicle, such as, for example, a speed of movement of the vehicle and a position of the lifting arm. These are therefore factors to be taken into account for carrying out wheel turning movements.
US20060180381 A1 describes a container-handling vehicle comprising a computation unit configured to determine limitations of the turning movements as a function of different operational parameters.
One idea on which the invention is based is to propose a steering control system which preserves the stability of a work vehicle in various operating conditions, in particular during load handling operations, and which allows an operator to control the steering of the vehicle according to his or her needs.
For that, according to one embodiment, the invention provides a rolling work vehicle comprising:
By virtue of these features, the first rate-of-variation cap makes it possible to allow a more or less rapid turning movement as a function of an orientation of the lifting arm. A rate of variation of an angle of the steering wheels can thus be limited as a function of the lifting arm orientation parameter, in order to ensure a totally safe turning of the wheels.
According to embodiments, such a work vehicle can comprise one or more of the following features.
According to one embodiment, the lifting arm orientation parameter comprises an angle of the lifting arm.
According to one embodiment, the angle of the lifting arm is measured with respect to a reference frame chosen from among the main body and the Earth's reference frame.
The lifting arm orientation parameter can relate to one or more degrees of freedom of the lifting arm, for example a degree of freedom in elevation about a horizontal axis and/or a degree of freedom in orientation about a vertical axis. According to a preferred embodiment, the angle of the lifting arm is an elevation angle about a horizontal axis.
According to one embodiment, the first rate-of-variation cap decreases when the elevation angle of the lifting arm increases.
According to one embodiment, the filtering module is further configured to:
According to one embodiment, the filtering module is configured to:
According to one embodiment, the work vehicle comprises a sensor for detecting a speed of movement of the vehicle. According to said embodiment, the filtering module is further configured to:
According to one embodiment, the second rate-of-variation cap decreases when the speed of movement increases.
According to one embodiment, the filtering module is further configured to:
According to one embodiment, the filtering module is configured to:
According to one embodiment, the work vehicle comprises a sensor for detecting a speed of movement of the vehicle. According to said embodiment, the steering control system comprises a renormalization module configured to:
According to one embodiment, the multiplying renormalization coefficient decreases when the speed of movement increases.
According to one embodiment, the multiplying renormalization coefficient reaches a plateau from a threshold speed of the vehicle.
According to one embodiment, the threshold speed is a parameter that can be configured using a user interface. For example, the threshold speed is 20 kilometres per hour.
According to one embodiment, the values of the renormalization coefficient, notably the value of the plateau, can be configured using a user interface. For example, the value of the plateau is 25%.
According to one embodiment, the steering control system comprises a correction module configured to:
According to one embodiment, the work vehicle comprises a sensor for detecting a speed of movement of the vehicle. According to said embodiment, the steering control system comprises a conversion module configured to:
According to a preferred embodiment, the steering control system comprises a proportional integral derivative (PID) corrector.
According to one embodiment, the steering control system can be implemented in a distributed manner.
The steering control member can have various forms, for example a lever, a steering wheel, buttons, a touchscreen, etc. According to a preferred embodiment, the steering control member is a steering joystick that can be actuated by a hand or by a finger of the operator. A steering member such as a steering joystick allows the operator to control the turning movement of the wheels without effectuating any movement of great amplitude.
The steering joystick does not offer a displacement amplitude that is as wide as the steering wheel, which can raise issues linked to the accuracy of the control exerted by the operator. However, the control system, in particular the filtering module, can be configured to avoid an excessively abrupt movement of the steering joystick from being fully transmitted to the steering actuator. Thus, the steering control system is advantageous both for the ergonomics offered to the operator and for the safety of operation obtained.
According to one embodiment, the work vehicle comprises two steering axles including at least four steering wheels. According to said embodiment, the turning actuator is coupled to the four steering wheels to modify a turning angle of the four steering wheels.
According to one embodiment, the invention also provides a control method for controlling a turning actuator in a rolling work vehicle, the work vehicle comprising a main body, a lifting arm mounted to be movable on the main body and intended to handle loads, a steering axle including at least two steering wheels and said turning actuator coupled to the steering wheels to modify a turning angle of the steering wheels, the method comprising:
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.
The invention will be better understood, and other aims, details, features and advantages thereof will become more clearly apparent from the following description of several particular embodiments of the invention, given in a purely illustrative and nonlimiting manner, with reference to the attached drawings.
The lifting arm 4 can be a telescopic arm of a length that is adjustable between a retracted position and an extended position. The lifting arm makes it possible to bear loads. A degree of freedom in rotation between the main body 2 and the lifting arm 4 makes it possible to lift or lower the lifting arm by means of a lifting cylinder which is not represented. A tool 21 can be fixed to a tool-holder 25 of the lifting arm. According to a preferred embodiment, the tool-holder 25 can be designed to removably mount various handling tools such as forks, a boom, a bucket or the like. An excavation cylinder 22 makes it possible to orient the tool 21 with respect to the lifting arm 4. A telescoping cylinder not represented makes it possible to adjust the length of the telescopic arm.
The work vehicle 1 comprises at least one steering axle, for example the front axle or the rear axle. In a variant, both of the axles are steering axles, namely four steering wheels. The driving of the work vehicle 1 in displacement is made possible by the rotating of wheels 5 in contact with the ground by means of a traction system which will not be described in detail. The motorization can be heat engine-based or electrical. The transmission can be mechanical or hydraulic.
Referring to
The operator can control the turning movements of the wheels 5a and 5b using a steering joystick 6 situated in the cabin 3, for example on an armrest 32 of an operator seat 31. The steering joystick sends a position signal A to a steering control system 10.
The control system 10 generates a wheel position signal E which is transmitted to a turning actuator 12 coupled to the steering wheels to modify a turning angle of the steering wheels and thus modify a direction of displacement of the vehicle 1. The turning angle is for example identical for all the steering wheels. The turning actuator 12 is for example hydraulic or electrical. A hydraulic distribution system 11 is used to drive the turning actuator 12 in the case where the turning actuator 12 is hydraulic.
A speed-of-movement sensor 7 is disposed on the work vehicle 1 and transmits a speed of movement of the vehicle v to the steering control system 10.
An elevation angle sensor 8 is disposed on the lifting arm 4 and transmits a lifting 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.
At least one sensor 8 of elevation angle x 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.
A direction of inclination of the steering joystick 6, namely to the right as illustrated by the arrow 18 or to the left as illustrated by the arrow 19, indicates a turning direction of the wheels. An angle of inclination of the steering joystick allows a quantitative control of the turning angle, via a processing of the position signal A generated by the steering joystick 6, as will be explained below.
The steering joystick 6 makes it possible to generate a position signal A. The speed sensor 7 measures the speed of movement of the vehicle v. The elevation angle sensor 8 measures the lifting arm elevation angle x. A wheel angle sensor 9 measures an angular position of the wheels.
The position signal A, the speed of movement of the vehicle v, the elevation angle of the lifting arm x and the angular position of the wheels are processed by the steering control system 10, which generates a wheel position signal E, which is a new wheel position angle. Said wheel position signal E is transmitted to a hydraulic control valve system 11, then to a front actuator 12a and a rear actuator 12b, which control the turning movement of the wheels.
The wheel position signal E is calculated every 10 milliseconds and is transmitted to the hydraulic control valve system 11 every 20 milliseconds, which gives the operator an impression of immediacy, namely real-time control.
The correction module 101 comprises a gain function 51 which makes it possible to correct the position signal A.
The renormalization module 102 comprises a renormalization function 61 which returns a multiplying normalization coefficient value a dependent on the speed of movement of the vehicle V.
The filtering module 103 assesses a rate-of-variation cap of the turning angle as a function of the speed of movement v and of the elevation angle x of the lifting arm 4. The filtering module comprises a first filtering function 70-71 dependent on the lifting arm orientation parameter x and a second filtering function 72-73 dependent on the speed of movement v.
The conversion module 104 converts the filtered turning request signal D into the wheel position signal E and possibly applies a variable capping law to the wheel position signal E.
The gain function 51 is convex and less than the identity function. The gain function 51 allows a finer control of the movement of the wheels for the movements of the steering joystick 6 that are of low amplitude.
The renormalization function 61 takes as input a speed of movement of the vehicle v, represented on the X axis and expressed in km/h, and returns a multiplying renormalization coefficient α, adimensional and expressed as a percentage, which is subsequently applied to the corrected turning request signal B and which corresponds to an authorized maximum turning request as a function of the speed of movement of the vehicle.
The renormalization function 61 is a decreasing and positive function.
One effect of the renormalization function 61 is to increase a sensitivity of the steering joystick 6 over authorized angle ranges. Indeed, after application of the renormalization function 61, a maximum amplitude of the movement of the orientation control member 6 corresponds to a lower maximum turning request, which provokes an increase in sensitivity.
The first filtering function is a low-pass filter. The first filtering function takes a first, constant level value after a threshold angle value is reached. The threshold angle value is 40° in the example represented.
The first filtering function 68 comprises a first turn cap value 70 if a direction of variation of the turning request signal is a turn direction and a first reverse cap value 71 if the direction of variation is a reverse direction. The first filtering function 68 returns a first speed cap.
The first reverse cap value 71 is higher than the first turn cap value 70, which has the effect of making it possible to straighten the direction of the vehicle more rapidly than the turning speed.
The second filtering function 69 is a low-pass filter. The second filtering function takes a second, constant level value after a threshold speed-of-movement value is reached. The level speed-of-movement value is 40 km/h in the example represented.
The second filtering function 69 comprises a second turn cap value 72 if the direction of variation of the turning request signal is the turn direction and a second reverse cap value 73 if the direction of variation is the reverse direction, the second reverse cap value 73 being greater than the second turn cap value 72. The second filtering function 69 returns a second speed cap.
The operation of the filtering module 103 will now be explained with reference to
The re-normalized turning 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, then remains constant beyond. The second input slope 82 is less than the first slope 81.
The filtering module 103 applies the rate-of-variation caps represented in
Every 20 milliseconds, the filtering module 103 transmits a new filtered turning request signal D. Up to 40 milliseconds, the filtered turning request signal D follows a first output slope 91 which is equal to the rate-of-variation cap. Beyond that, the filtered turning request signal D follows a second output slope 92 which is equal to the second input slope 82.
The operation of the conversion module 104 will now be explained with reference to
In this embodiment, the conversion module 104 implements a capping function that is variable as a function of the speed. Indeed, a maximum turning angle value y depends on the speed of movement of the vehicle. The maximum turning angle value y is determined by application of a capping law represented in
As a variant, the conversion function implemented by the conversion module 104 could be independent of the speed of movement, namely the capping law of
As a variant, the lifting arm 4 may not be telescopic.
As a variant, there can be two turning actuators, a first actuator 12a being coupled to the front wheels 5a and a second actuator 12b being coupled to the rear wheels 5b.
As a variant, the gain function 51 can be piecewise affine, polynomial, exponential, etc.
As a variant, the renormalization function 61 can be affine, piecewise affine, polynomial, exponentially decreasing, etc.
As a variant, the control system 10 can also comprise fewer turning request signal processing functions and/or other functions. For example, one or more modules out of the correction module 101 and the renormalization module 102 could be eliminated. The second filtering function 72-73 of the filtering module 103 could be eliminated. Some modules of the control system could be placed in an order other than that represented.
Preferably, the control system 10 comprises a user interface (not represented) which makes it possible to configure the values of the parameters that influence the processing of the turning request signal, namely for example:
The steering control system described above is used mainly to secure the use of the rolling work vehicle when handling operations are in progress. The fact that another steering control system could be used in other conditions, for example when the work vehicle is travelling on the road network, if such travelling is permitted, is not excluded.
A load handling truck with telescopic arm has been described, but the turning control system can be applied to another rolling work vehicle having a lifting arm, for example a rotary turret handling truck, a bucket loading machine or the like.
As a variant, in addition to or instead of the lifting arm elevation angle sensor, other lifting arm orientation parameters can be measured and taken into account by the turning control system, for example an orientation angle of the arm in an azimuthal direction with respect to the longitudinal direction of the vehicle.
Some of the elements represented, notably the control system 10, can be produced in different forms, unitary or distributed, by means of hardware and/or software components. Hardware components that can be used are specific integrated circuits ASIC, programmable logic arrays FPGA or microprocessors. Software components can be written in different programming languages, for example C, C++, Java or VHDL. This list is not exhaustive.
Although the invention has been described linked to a number of particular embodiments, it is quite obvious that it is in no way limited thereto and that it encompasses all the technical equivalents of the means thus described and the combinations thereof if the latter fall within the context of the invention.
The use of the verb “comprise” or “include” and its conjugate forms does not preclude the presence of elements or steps other than those stated in a claim.
In the claims, any reference symbol between parentheses should not be interpreted as a limitation of the claim.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2200508 | Jan 2022 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/051439 | 1/20/2023 | WO |
