Wheel slip boost function for large vehicle

Abstract

To provide a vehicle motion management method which has more recovery force to an error in an approximate relation between a wheel slip and a generated longitudinal wheel force.SOLUTION: A computer mounting method for controlling at least one driven wheel and / or brake wheel (102) of a large vehicle (100) includes: acquiring a motion request (areq, Fx) indicating desired longitudinal acceleration and / or desired longitudinal force relating to the vehicle; setting a wheel slip limit value (λlim) indicating a maximum allowable wheel slip by at least the one driven wheel and / or brake wheel (102) at a nominal value; increasing the wheel slip limit value (λlim) to a boost wheel slip value from the nominal value according to detection of a boost signal; and controlling at least the one driven wheel and / or brake wheel (102) depending on the motion request (areq, Fx) according to the wheel slip limit value (λlim).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a method and control unit for ensuring safe and efficient vehicle motion management of heavy vehicles. This method is particularly suitable for use in freight transport vehicles such as trucks and semi-trailers. However, the present invention may also be applied to other types of heavy vehicles, such as construction machinery, mining vehicles, and automobiles. [Background technology]

[0002] Heavy-duty vehicles have traditionally been controlled using torque request signals determined based on the position of the accelerator or brake pedal and transmitted via a digital interface to motion support devices (MSDs) such as service brakes and propulsion devices. However, advantages can sometimes be gained by controlling actuators using wheel slip requests or wheel speed requests transmitted from a central vehicle controller to different actuators. This brings actuator control closer to the wheel side (wheel end), reducing latency and enabling faster and more precise control of the MSD. The wheel slip-based MSD control approach is particularly well-suited for use in wheel end electromechanics in battery or fuel cell-powered vehicles, where high bandwidth and precise control are possible. Wheel slip-based vehicle motion management and its associated advantages are described, for example, in International Publications 2017 / 215751 and 2021 / 144010. [Overview of the project] [Problems that the invention aims to solve]

[0003] Wheel slip or wheel speed-based control of large vehicles often relies on an approximate relationship between wheel slip and the resulting longitudinal wheel force, often referred to as the inverse tire model. However, large vehicles are complex dynamic mechanical systems that are difficult to model accurately and can rapidly change their behavior in response to changes in road friction conditions, for example. Therefore, the inverse tire model is not always perfectly accurate, which can lead to performance degradation.

[0004] A vehicle motion management method that is more resilient to errors in the approximate relationship between wheel slip and the resulting longitudinal wheel force is desired. [Means for solving the problem]

[0005] The object of this disclosure is to overcome, at least partially, the aforementioned shortcomings and to provide an improved method for controlling a heavy vehicle. This object is achieved by a computer-implemented method (a method implemented in a computer) for controlling at least one driven wheel and / or braking wheel of a heavy vehicle. The method includes the step of obtaining a motion request indicating a desired longitudinal acceleration and / or a desired longitudinal force generated by one or more wheels related to the vehicle. The method also includes the step of setting a wheel slip limit to a nominal wheel slip limit, depending on (based on) an inverse tire model, where the inverse tire model represents the relationship between wheel slip and wheel force at a wheel, and the wheel slip limit indicates the maximum allowable wheel slip by at least one driven wheel and / or braking wheel. The method further includes the steps of increasing the magnitude of the set wheel slip limit from the nominal wheel slip limit to a boost wheel slip limit in response to detection of a boost signal, and controlling at least one driven wheel and / or braking wheel according to the set wheel slip limit and depending on the motion request. In this way, the generation of a boost signal can temporarily increase the acceptable wheel slip. This feature can be useful, for example, when driving uphill in difficult conditions, or in other scenarios where the driver, remote controller, or autonomous driving algorithm determines that it is desirable to provide a further boost to exceed the nominal wheel slip limit. The fact that the wheel slip limit is set depending on the reverse tire model is particularly advantageous because it links the wheel slip limit to the longitudinal force that can be generated by the vehicle's wheels. The disclosed method provides a vehicle motion management method that is more resilient to errors in the approximate relationship between wheel slip and the generated longitudinal wheel force.

[0006] According to an aspect, the method includes a step of determining a nominal wheel slip limit value based on an inverse tire model, where the inverse tire model represents the relationship between the wheel slip and the wheel force of at least one driven wheel and / or braking wheel. The inverse tire model is a convenient means for converting between the desired longitudinal force generated by a given wheel and the corresponding wheel slip. The nominal wheel slip limit value may be determined, for example, as a point somewhat away from (a point with some margin) the peak of the inverse tire model, i.e., the wheel slip corresponding to the maximum longitudinal force. Since the inverse tire model can be determined depending on the current operating state of the vehicle, the wheel slip limit is also adjusted according to the operating state of the vehicle, which is an advantage.

[0007] The motion requirement is obtained, for example, as a function of the accelerator pedal position or the brake pedal position, whereby the driver can conveniently enter the boost mode by depressing the pedal by a significant amount, for example, exceeding a certain threshold value. It is understood that this method may be most useful in relation to acceleration, i.e., forward propulsion, but may also find important applications during deceleration, i.e., during hard braking.

[0008] Alternatively, or as a supplement to the pedal position trigger for the boost mode, the motion requirement may be obtained from the motion support device (MSD) adjustment function of the vehicle motion management (VMM) system provided in a large vehicle, and / or from an autonomous or semi-autonomous driving function provided in the vehicle, as will be described in more detail below. This means that the vehicle control function has the option of temporarily increasing the wheel slip to obtain a boost when the wheel slip limit is set to be, for example, quite conservative at least temporarily. This improves the degree of freedom of control of the autonomous or semi-autonomous control algorithm, which is an advantage.

[0009] The method also includes, optionally, a step of determining a target wheel slip value as a nominal target wheel slip value depending on a motion requirement and also depending on an inverse tire model representing the relationship between wheel slip and wheel longitudinal force. Then, the method includes a step of increasing the target wheel slip value from the nominal target wheel slip value to a boost target wheel slip value in response to detecting a boost signal, and a step of controlling at least one driven wheel and / or braking wheel depending on the target wheel slip value. Accordingly, in addition to increasing the wheel slip limit value, the target wheel slip used for vehicle control can be temporarily increased to enhance the driving force of the vehicle. This feature can be advantageously used, for example, in a driving scenario where the nominal target wheel slip value is too conservative for some reason.

[0010] The boost signal can be triggered (induced), for example, when the accelerator pedal position or the brake pedal position exceeds a threshold value. The boost signal may be manually triggered by operating a trigger device such as a button or a switch inside the cab. Also, the boost signal may be triggered by the accelerator pedal position or the brake pedal position exceeding the threshold value over a predetermined period.

[0011] To avoid compromising vehicle stability, the boost signal is optionally conditional (necessary condition) that the vehicle is operating at a speed below the vehicle speed tolerance threshold. Therefore, if the vehicle's motion is too fast, the boost signal will not be generated. The generation of the boost signal may also be conditional that the vehicle is operating with yaw motion below the vehicle yaw motion tolerance threshold. This means that the method can be configured so that the boost mode is not permitted when the vehicle is cornering, as this could jeopardize the success of the turning maneuver. This is because the ability to generate lateral force decreases as longitudinal wheel slip increases. Similarly, the method, of course, also includes a step of determining the lateral force requirements of at least the driven wheels and / or braking wheels, and the boost signal is conditional on the lateral force requirements being below the lateral force requirement threshold. In this way, the stability and safety of the vehicle are not compromised by an increase in wheel slip. Otherwise, a rapid increase in longitudinal wheel slip could reduce the ability to generate lateral force to dangerously low levels.

[0012] The method may also include a step of increasing the set wheel slip limit from the nominal wheel slip limit to a boosted wheel slip limit only for a predetermined period of time. After this period, the wheel slip limit setting may return to, for example, the nominal value or some other provisional or intermediate value. This prevents the vehicle's wheels from digging into the road surface, which is, of course, an advantage.

[0013] In some embodiments, the boost signal is configured to be remotely triggered by the operation of a remotely controlled trigger device. This allows an autonomous function or operator outside the vehicle to trigger the boost mode, enabling the vehicle to, for example, navigate a difficult incline. In this way, additional functionality can be granted to the vehicle by a remote authority (remote mechanism), which can be advantageous in certain situations, for example, within a limited area where an autonomous vehicle needs to operate at a fairly conservative wheel slip value to ensure safe operation. The remote authority may allow an autonomous or semi-autonomous vehicle to temporarily operate at a higher wheel slip value to temporarily improve the vehicle's maneuverability.

[0014] The method may also include a step of updating the reverse tire model associated with at least one driven wheel and / or braking wheel in response to the detection of a boost signal. This means that the reverse tire model used to manage the vehicle's motion is refined over time, thereby resulting in a more accurate reverse tire model, which is an advantage.

[0015] The objective can also be achieved by a computer-implemented method for controlling at least one driven wheel and / or braking wheel of a large vehicle. This method includes the steps of: obtaining a motion request indicating a desired longitudinal force (intended) generated by one or more wheels of the vehicle; and setting a nominal relationship between wheel slip and longitudinal force, i.e., an inverted tire model, etc., wherein the relationship is at least partially based on a slip stiffness value. The method further includes the steps of: obtaining a driver input signal indicating a desired adjustment of the nominal slip stiffness value; resetting (reconfiguring) the nominal relationship between wheel slip and longitudinal force to take into account the adjustment of the nominal slip stiffness value; and controlling at least one driven wheel and / or braking wheel in accordance with the motion request and based on the adjusted relationship between wheel slip and longitudinal force.

[0016] Therefore, a driver input signal, which may be the aforementioned boost signal, is used to adjust the characteristics of the perceived vehicle dynamics. In this way, by adjusting the relationship between wheel slip and longitudinal force, an effect similar to that of the aforementioned boost mode can be obtained. Alternatively or as a supplement, a similar method may be considered in which the estimated peak longitudinal force of the reverse tire model is shifted in response to the driver input signal.

[0017] The adjustment of the reverse tire model can, of course, be made a function of the time the driver holds down the pedal; that is, the longer the pedal is held down, the more the model's slip stiffness changes. The other functions mentioned above can, of course, also be applied to this type of adjustment of the reverse tire model.

[0018] This specification also discloses control units, vehicle units, computer programs, computer-readable media, and computer program products related to the aforementioned advantages.

[0019] In general, all terms used in the claims should be interpreted according to their common meaning in the art unless otherwise explicitly defined herein. All references to “one (a / an) element, apparatus, component, means, step, etc.” should be interpreted openly as referring to at least one instance of such element, apparatus, component, means, step, etc., unless otherwise explicitly stated. Steps of any method disclosed herein do not need to be performed in the exact order disclosed unless expressly stated otherwise. Further features and advantages of the present invention will become apparent when considering the appended claims and the following description. As those skilled in the art will see, different features of the present invention can be combined without departing from the scope of the present invention to produce embodiments other than those described below.

[0020] The above, as well as further objectives, features, and advantages, can be better understood through the following illustrative and non-limiting detailed description of a typical embodiment. [Brief explanation of the drawing]

[0021] [Figure 1] This is a diagram illustrating an example of a large vehicle. [Figure 2] This graph illustrates tire force as a function of wheel slip. [Figure 3] This is a diagram illustrating an example of a control configuration for an exercise support device. [Figure 4] This is a diagram illustrating an example configuration for wheel slip boosting. [Figure 5] This is a diagram illustrating an example of a vehicle control function architecture. [Figure 6] This is a flowchart showing the method. [Figure 7] This is a schematic diagram of the control unit. [Figure 8] This is an example of a computer program product. [Modes for carrying out the invention]

[0022] Herein, the present disclosure will be fully described below with reference to the accompanying drawings illustrating typical embodiments. However, the present disclosure may be embodied in many different forms and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided to be thorough and complete. Throughout the description, similar reference letters refer to similar elements.

[0023] Figure 1 shows an example of a large vehicle 100, in the form of a truck. The vehicle has a plurality of wheels 102, and at least a subset of the plurality of wheels 102 is equipped with a motion support device (MSD) 104. Although the embodiment shown in Figure 1 shows an MSD for each wheel 102, it should be easily understood that, for example, a pair of wheels 102 may be arranged without such MSDs 104. Also, the MSDs may be arranged connected to two or more wheels, for example, via a differential.

[0024] The methods and control units disclosed herein can be advantageously applied to other types of heavy vehicles, such as trucks, construction machinery, and buses, with towing couplings. Vehicle 100 may also comprise three or more vehicle units, i.e., it may tow two or more trailers using dolly vehicle units.

[0025] The MSD 104 may be positioned to generate torque acting on each wheel of the vehicle or on both wheels of the axle. The MSD may also be a propulsion device such as an electromachine 106 configured to impart longitudinal wheel force to the wheels of the vehicle 100. Thus, such an electromachine may be configured to generate propulsion torque, as well as to be configured in a regenerative braking mode for charging the vehicle 100's battery (not shown) or other energy storage system. Alternatively, the electromachine may generate braking torque without storing energy. For example, by using a braking resistor, excess energy can be dissipated from the electromachine during braking.

[0026] Furthermore, the MSD104 may also be equipped with friction brakes, such as disc brakes or drum brakes, configured to generate braking torque by the wheels 102 to decelerate the vehicle. Here, the term acceleration should be interpreted broadly to include both positive acceleration (propulsion) and negative acceleration (braking).

[0027] The methods disclosed herein primarily relate to controlling the propulsion, i.e., acceleration, of large vehicles. However, the disclosed methods can also be used when decelerating large vehicles, i.e., during braking.

[0028] Furthermore, each MSD 104 is connected to its own MSD control system 330, which is configured to control the operation of the MSD 104. The MSD control system 330 is preferably a distributed motion support system 330, but a centralized implementation is also possible. Furthermore, it can be seen that a part of the MSD control system may be implemented on a processing circuit located away from the vehicle, such as on a remote server 120 accessible from the vehicle via a wireless link. Moreover, each MSD control system 330 is connected to the vehicle motion management (VMM) system or function 360 of the vehicle 100 via a data bus communication device 114, which may be wired, wireless, or both wired and wireless. This allows control signals to be transmitted between the vehicle motion management system 360 and the MSD control system 330. The vehicle motion management system 360 and the MSD control system 330 will be described in more detail below with reference to Figures 3 and 5.

[0029] The VMM system 360 and the MSD control system 330 may include a microprocessor, microcontroller, programmable digital signal processor, or other programmable device. The system may further or alternatively include an application-specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. If the system includes a programmable device such as the aforementioned microprocessor, microcontroller, or programmable digital signal processor, the processor may further include computer executable code that controls the operation of the programmable device. Different vehicle unit processing circuit implementations are described in more detail below with reference to Figure 7.

[0030] In general, MSDs on vehicle 100 can also be implemented as, for example, power steering devices, active suspensions, etc. While these types of MSDs cannot be used to directly generate longitudinal forces, they are still part of the overall vehicle motion management of large vehicles and can therefore form part of the vehicle motion management methods disclosed herein.

[0031] In particular, the MSD of a large vehicle 100 is often adjusted to obtain a desired motion (movement) from the vehicle. For example, by using two or more MSDs together, a desired propulsion torque or braking torque, a desired yaw motion from the vehicle, or some other dynamic behavior can be generated.

[0032] Figure 2 is a graph showing an example of achievable tire force 200 as a function of longitudinal wheel slip. (Longitudinal wheel slip λ) x This can be defined as follows, in accordance with SAE J370 (SAE Vehicle Dynamics Standards Committee, January 24, 2008):

number

[0033] Here, R is the effective wheel radius in meters, ω x ν is the angular velocity of the wheel. x λ is the longitudinal velocity of the wheel (in the wheel's coordinate system). Therefore, λ x It is limited between -1 and 1, and quantifies how much the wheel is slipping relative to the road surface. Wheel slip is essentially the speed difference measured between the wheel and the vehicle. Thus, the techniques disclosed herein can be adapted for use with any type of wheel slip definition. It can also be seen that the wheel slip value is equal to the wheel speed value given by the speed of the wheel across the surface in the wheel's coordinate system. VMM360 and optionally the MSD control system 330 also optionally use ν x Maintain information (in the wheel's reference coordinate system), while using wheel speed sensors, etc., to determine ωx The rotational speed of the wheel can be determined (specified).

[0034] In order for the wheel (or tire) to generate wheel forces, slip must occur. When the slip value is small, the relationship between slip and the generated force is approximately linear, and the proportionality constant is often expressed as the slip stiffness of the tire. The tire is subject to a longitudinal force F x , a lateral force F y , and a normal force F z . The normal force F z is crucial in determining several important vehicle characteristics. For example, since typically F x ≦ μF z , the normal force determines, to a large extent, the lateral tire force F y achievable by the wheel, where μ is the friction coefficient related to the road surface friction condition. The maximum available lateral force for a given lateral slip can be represented by the so-called magic formula, as described in "Tyre and vehicle dynamics" by Hans Pacejka, Elsevier Ltd. 2012, ISBN 978 - 0 - 08 - 097016 - 5.

[0035] By using an inverse tyre model, the desired longitudinal tyre force F xIt is possible to convert between torque and wheel slip. The interface between the VMM and MSD, which can also deliver steering and optionally torque to the vehicle's wheels, has traditionally focused on torque-based requests from the VMM to each MSD without considering wheel slip, as mentioned above. However, this approach has significant performance limitations. In the event of a safety-critical or excessive slip situation, relevant safety functions (such as traction control and anti-lock brakes), usually operated by separate control units, intervene and request a torque override to return the slip to its original control. The problem with this approach is that the primary control of the actuator and the slip control of the actuator are assigned to different electronic control units (ECUs), and the delays in communication between them significantly limit the performance of the slip control. Furthermore, the assumptions about the relevant actuators and slip made by the two ECUs used to implement the actual slip control may not match, which may result in suboptimal performance. Alternatively, significant advantages can be gained by using wheel speed or wheel slip-based requests in the interface between the VMM360 and one or more MSD controllers 330, thereby allowing the complex actuator speed control loop to be migrated to the MSD controllers, which generally operate with much shorter sample times compared to the sample times of the VMM functions. Such an architecture can result in much better disturbance rejection compared to torque-based control interfaces, thus improving the predictability of forces generated at the tire's road contact patch (contact patch).

[0036] Referring again to Figure 2, the longitudinal tire forces Fx1 and Fx2 show a portion 210 that increases almost linearly with respect to small wheel slip, followed by a portion 220 that exhibits more nonlinear behavior with respect to larger wheel slip. Tire model Fx1 represents a high-friction scenario, i.e., a dry road with good tires, while Fx2 represents a reduced-friction scenario. Note that the maximum achievable tire force decreases with the friction coefficient μ. Furthermore, the wheel slip value corresponding to the peak wheel force is slightly shifted between the two curves, with the peak 240 in curve Fx1 occurring at a higher wheel slip compared to the peak 260 in curve Fx2. Therefore, if curve Fx1 is actually closer to the actual relationship between wheel slip and wheel force, the wheel slip limit λ is set somewhat away from the peak of curve Fx2 (with some margin). lim It may be excessively understated.

[0037] Referring to curve Fx2, it is desirable to maintain vehicle operation in the linear region 210 where the longitudinal force obtained in response to the applied brake command is more predictable and sufficient lateral tire force can be generated as needed. To ensure operation in this region, for example, a wheel slip limit λ of about 0.1 is desirable. lim A value of 230 can be imposed on a given wheel. For example, in the case of large wheel slips exceeding 0.1, a greater nonlinear region of 220 is observed. Controlling the vehicle in this region can be difficult and is therefore often avoided. It may be interesting in towing, such as in off-road conditions where a larger slip limit for towing control may be preferred, but not so much in on-road operation.

[0038] Setting the wheel slip limit based on the reverse tire model, rather than as a predetermined or hardcoded parameter, is advantageous. For example, a wheel slip limit set in relation to the peak value of the assumed reverse tire model is adapted to the vehicle's current operating state.

[0039] However, it is still desirable to override the slip limits set based on the assumed reverse tire model. For example, the reverse tire model may be unnecessarily conservative, meaning that the slip limits prevent the vehicle from fully utilizing its potential traction or braking force because they prevent it from operating at the desired wheel slip.

[0040] For example, suppose the motion management of a large vehicle uses an inverted tire model following curve Fx2, but in reality, assume that curve Fx1 more accurately models the true relationship between wheel slip and longitudinal wheel force. Furthermore, assume that the wheel slip limit is set to 230 to ensure operation in the linear region 210. At this slip limit, the vehicle is no longer able to generate a wheel force greater than approximately 5.5 kN, which is far below the maximum achievable wheel force of approximately 9 kN. Of course, this is undesirable.

[0041] To enable a driver, or other form of vehicle controller such as an autonomous or semi-autonomous drive system, to override a set nominal wheel slip limit, it is proposed herein that the wheel slip limit be temporarily increased to a boost wheel slip limit in response to the detection of a boost signal, which may be triggered, for example, by the driver pressing the accelerator or brake pedal beyond a certain threshold, or by the driver operating some in-cabin manual controller, such as a boost button on the dashboard. In certain vehicles or use cases, including both autonomous driving modes and human-centered driving modes, it may be desirable to grant the human driver more control than the automated driver, and the technology disclosed herein may be used to provide such an increased level of control over the allowable wheel slip.

[0042] A boost signaling mechanism may be used by some remote authority, such as an air traffic control tower, to allow some vehicles to operate at temporarily high slip values, for example, when it is desirable that such high wheel slip operation be considered advantageous and safe.

[0043] Furthermore, if the reverse tire model is updated in real time based on the observed vehicle behavior, it may be beneficial in some situations to allow wheel slip to exceed the peak of the current "known" tire model. When the vehicle is driven by a human driver, using the accelerator pedal can "force" a higher slip target in certain situations, and additional traction can be obtained if (for example) the parameterization of the current tire model is overly conservative. In this way, the vehicle controller can "explore" the relationship between wheel force and wheel slip, even if it exceeds the set nominal wheel slip limit, at least temporarily.

[0044] In any functional safety discussion, adding this type of wheel slip limit "override" can reduce the number of functional safety requirements imposed on the reverse-tire model. This is because a human driver can always override to a higher slip target in critical situations (e.g., being stuck on train tracks and attempting to start moving).

[0045] Referring here to Figure 3, the entire vehicle control system 300 may be implemented on one or more vehicle unit computers (VUCs). The VUC may be configured to perform a vehicle control method organized according to a hierarchical functional architecture in which some functions may be included in a higher-level traffic situation management (TSM) domain 370, and other functions may be included in a lower-level vehicle motion management (VMM) domain 360.

[0046] Figure 3 schematically illustrates a function 300 for controlling an exemplary wheel 310 of a vehicle 100 by several exemplary MSDs, which here include a friction brake 320 (such as a disc brake or drum brake), a propulsion device 340, and a steering device 330. The friction brake 320 and the propulsion device are examples of wheel torque generating devices, which may be controlled by one or more motion support device control units 330. The control is based on measurement data obtained, for example, from a wheel speed sensor 350, as well as from other vehicle state sensors 370, such as radar sensors, lidar sensors, and vision-based sensors such as camera sensors and infrared detectors. The MSD control system 330 may be configured to control one or more actuators. For example, it is not uncommon for the MSD control system 330 to be configured to control both wheels on an axle.

[0047] The TSM function 370 plans driving operations within a planning period of approximately 10 seconds. This period (time frame) corresponds, for example, to the time it takes for the vehicle 100 to pass through a curve, etc. The vehicle movements planned and executed by the TSM function may be associated with acceleration profiles and curvature profiles that describe the desired target vehicle speed in a turn, maintained with respect to the vehicle's forward direction and a given operation. The TSM function receives the desired acceleration profile a from the VMM function unit 360, which safely and robustly executes force distribution to meet the requirements from the TSM function. req and steering angle (or curvature profile c) req ) continuously requests. The VMM function 360 operates on a timescale of less than 1 second and is described in more detail below.

[0048] Wheel 310 has a longitudinal velocity component v x and transverse velocity component v y Possesses. Vertical wheel force F x and lateral wheel force F y There is a normal force F acting on the wheel. zThere are also (not shown in Figure 3). Unless otherwise explicitly stated, wheel forces are defined in the wheel's coordinate system, that is, longitudinal forces are directed toward the wheel's plane of rotation, and transverse wheel forces are directed perpendicular to the wheel's plane of rotation. The wheel rotates at a speed w x It has a radius R.

[0049] The type of tire model 200 shown in Figure 2 can be used by the VMM 360 to generate a desired tire force on a wheel. Instead of requesting a torque corresponding to the desired tire force, the VMM can convert the desired tire force into an equivalent wheel slip (or wheel speed relative to ground speed) and request this slip instead. The main advantage is that the MSD control device 330 can obtain the vehicle speed ν from, for example, the wheel speed sensor 350. x and wheel rotation speed ω x The advantage is that by using this, the requested torque can be delivered in a higher bandwidth by maintaining operation with the desired wheel slip. x This information can be obtained from various vehicle sensors, such as radar, lidar, and vision-based sensors, combined with a Global Positioning System (GPS) receiver.

[0050] One or more control units control a predetermined reverse tire model f -1The reverse tire model can be configured to be stored in memory, for example, as a lookup table. The reverse tire model is configured to be stored in memory as a function of the current operating state of the wheel 310. This means that the behavior of the reverse tire model is adjusted depending on the operating state of the vehicle, thereby providing a more accurate model compared to a model that does not consider the operating state. The model stored in memory may be determined based on experiment and trial, or on analytical derivation, or a combination of the two. For example, the control unit may be configured to access a set of different models selected according to the current operating state. One reverse tire model may be adjusted for high-load driving with a large normal force, and another reverse tire model may be adjusted for slippery road conditions with low road friction, and so on. The selection of the model to be used can be based on a set of predetermined selection rules. The model stored in memory can also be a function of the operating state, at least partially. Thus, the model may be configured to take, for example, normal force or road friction as input parameters, thereby obtaining a reverse tire model depending on the current operating state of the wheel 310. While many modes of operation can be approximated by default operation state parameters, other modes of operation can be broadly classified into fewer classes. Therefore, obtaining a reverse tire model depending on the current operation state of wheel 310 does not necessarily mean that it is necessary to store a large number of different models or a complex analytical function that can consider changes in operation state at a fine granularity. Rather, two or three different models selected according to the operation state are sufficient. For example, one model can be used when the vehicle load is high, and another model can be used otherwise. In either case, the mapping between tire force and wheel slip changes in some way depending on the operation state, thereby improving the accuracy of the mapping.

[0051] Furthermore, the reverse tire model may be implemented at least partially as an adaptive model configured to automatically or at least semi-automatically adapt to the current operating state of the vehicle. This can be achieved by constantly monitoring the response of a given wheel with respect to the wheel force generated in response to a given wheel slip request, and / or by monitoring the response of the vehicle 100 in response to the wheel slip request. The adaptive model can then be adjusted to more accurately model the wheel force obtained from the wheel in response to a given wheel slip request.

[0052] The reverse tire model can be configured automatically from a remote server 120, for example, as a software update, or it can be configured manually by a technician performing routine vehicle maintenance.

[0053] Assume that the TSM function 370 transmits motion requests 375 via the interface between the TSM and the VMM, for example, as a function of the accelerator pedal position or as a control decision made by some autonomous driving algorithm operating in a higher-level control function. The VMM function performs vehicle control based on the aforementioned principles, namely ensuring operation in the linear force region 210 and the wheel slip limit value λ. lim Excessive wheel slip is avoided by setting the nominal wheel slip limit value λ. In this case, as mentioned above, this wheel slip limit value represents the maximum allowable wheel slip by one or more of the vehicle's multiple wheels 102. The VMM module 360 ​​receives the set wheel slip limit value λ. lim The system also includes a wheel slip boost module 361 configured to increase the magnitude of the boost from the nominal wheel slip limit to the boost wheel slip limit in response to the detection of the boost signal 361. This means that the positive drive wheel slip limit becomes larger, and the negative braking wheel slip limit becomes smaller (more negative).

[0054] Therefore, the VMM system and MSD controller are made capable of controlling the wheels with wheel slip exceeding the nominal wheel slip limit, at least temporarily. For example, if the reverse tire model used by the VMM function is the Fx2 function in Figure 2, and the Fx1 function is actually close to the true relationship, the boost mode allows the vehicle to approach the peak force of 240, at least for a limited period. It may be difficult to precisely determine the optimal offset of 250 from the nominal wheel slip limit to the peak force wheel slip limit. However, by enabling a boost above the set wheel slip limit, the achievable wheel force can be increased, at least to some extent. As a result, a driver who wants to navigate an uphill road with difficult road friction conditions can be made capable of temporarily increasing the wheel slip beyond the nominal wheel slip limit to see if this gives more longitudinal wheel force. This function is essentially similar to the "step-down" or "kick-down" acceleration boost mode found in many passenger cars today.

[0055] The magnitude of the increase in the nominal wheel slip limit can be set to a fixed value, for example, a wheel slip increase of approximately 0.05. Alternatively, the magnitude of the increase may be settable by the driver. The system may also include gradually increasing the wheel slip limit. For example, when the driver presses the accelerator or brake pedal beyond a certain threshold, the wheel slip limit is increased by some predetermined preset amount. Subsequently, the amount of increase exceeding the nominal wheel slip limit can be increased, for example, linearly as a function of how far the pedal is pressed beyond the threshold.

[0056] Figure 4 shows an exemplary configuration 400 for wheel slip boosting according to the principle described above. In this example, the accelerator pedal position (which may also be the brake pedal position) is mapped to a wheel force requirement Fx or torque requirement Tq to generate a desired acceleration of the vehicle 100. This desired wheel force is mapped to a desired nominal wheel slip value λ 0 or equivalently, the wheel speed value ω 0This is mapped to the boost signal. The boost signal is triggered by monitoring the pedal position and generating a boost signal when the pedal position exceeds a predetermined amount, for example, from 50% to 80% or fully depressed. If the driver depresses the pedal enough to trigger the boost signal, the magnitude of the set wheel slip limit is increased from the nominal wheel slip limit to the boost wheel slip limit. The increased wheel slip value (or equivalent wheel speed value) is then sent to the MSD controller 330 to control the wheels.

[0057] Figure 5 shows an example of a vehicle control function architecture applicable to the method disclosed herein, where the TSM function 370 generates a vehicle motion request 375, which is a desired steering angle δ or an equivalent curvature c that the vehicle should follow. req It may include the desired vehicle unit acceleration areq and other types of vehicle motion requirements, which together describe the desired motion (movement) of the vehicle along a desired path at a desired speed profile. It is understood that the motion requirements can be used as a basis for determining or predicting the required amounts of longitudinal and lateral forces that need to be generated to successfully complete the maneuver.

[0058] The VMM function 360 operates with a planning period of approximately 1 second, and the acceleration profile a from the TSM function req and curvature profile c req The system continuously converts the data into control commands to control the vehicle motion functions operated by different MSDs of the vehicle 100, and the different MSDs of the vehicle 100 report the functions used as constraints on vehicle control back to the VMM. The VMM function 360 performs vehicle state or motion estimation 510. That is, the VMM function 360 continuously determines the vehicle state s, including the position, velocity, acceleration, and coupling angle of different units in the vehicle combination, by monitoring the motion using various sensors placed on the vehicle 100, which are not always but often associated with the MSDs.

[0059] The result of motion estimation 510, i.e., the estimated vehicle state s, is input to the force generation module 520, which then generates the requested acceleration profile and curvature profile a of the vehicle 100. req , c req The global force V = [V1, V2] required for different vehicle units to move according to and to operate according to the desired vehicle behavior is determined. The required global force vector V is input to the MSD adjustment function 530, which assigns wheel forces to adjust other MSDs such as steering and suspension. The MSD adjustment function outputs an MSD control assignment for the i-th wheel, and this MSD control assignment is the torque T i , vertical wheel slip λ i , wheel rotation speed ω i , and / or wheel steering angle δ i This may include any of the following. The adjusted MSD then provides the vehicle unit with the desired lateral force Fy and longitudinal force Fx, as well as the required moment Mz, in order to obtain the desired motion (movement) by the vehicle combination 100.

[0060] For example, by determining the motion of a vehicle unit using a global positioning system, vision-based sensors, wheel speed sensors, radar sensors, steering angle sensors, and / or lidar sensors, and by converting this motion of the vehicle unit to the local coordinate system of a given wheel 310 (for example, with respect to longitudinal and lateral velocity components), as described above, it becomes possible to accurately estimate wheel slip in real time by comparing the motion of the vehicle unit in the wheel reference coordinate system with data obtained from a wheel speed sensor 350 connected to the wheel 310. Using the tire model described above in relation to Figure 2, a desired longitudinal tire force Fx for a given wheel i can be determined. i And, the equivalent longitudinal wheel slip λ with respect to the wheel i It can be converted between [this] and [that].

[0061] Accordingly, according to some aspects of this disclosure, the VMM function 360 manages both force generation and MSD adjustment, that is, determines the forces required in the vehicle unit to accelerate the vehicle according to a required acceleration profile requested by the TSM, and / or to generate a specific curvature motion by the vehicle, as also requested by the TSM, in order to satisfy the requirements from the TSM function 370. The forces may include, for example, a yaw moment Mz, longitudinal forces Fx and lateral forces Fy, as well as different types of torque to be applied to different wheels. The forces are determined in response to the control inputs generated by the TSM function 370, in order to produce the vehicle behavior expected by the TSM function.

[0062] In summary, with reference to the flowchart in Figure 6, a computer implementation method for controlling at least one wheel 102 of a large vehicle 100 is disclosed herein. The wheel 102 may be a driven wheel and / or a braking wheel, but this technique is probably most advantageously used for propulsion. The slip control method disclosed herein is particularly suited to implementation using wheel end electromechanics, but can also be used with a combustion engine, a hybrid electromechanics, or a differential drive driven by an electromechanics. This method is used to express motion requirements a, which represent a desired longitudinal acceleration and / or longitudinal force Fx related to the vehicle 100. req This includes the step (S1) of obtaining the motor request a. req As mentioned above in relation to Figure 5, this can be obtained as described above as a function of the accelerator pedal position or brake pedal position from the MSD adjustment function 530 of the VMM system included in the vehicle 100 (S12), or from the autonomous or semi-autonomous drive function included in the vehicle 100 (S11). Therefore, the motion request a, which indicates the desired longitudinal acceleration by the vehicle 100, can be obtained as described above. req The step of obtaining (S1) should be interpreted broadly in this specification.

[0063] The functions or features discussed herein may be configured or parameterized depending on the application and / or vehicle type. It will be apparent that driver control interfaces may differ between different vehicles, and such variations must, of course, be taken into consideration.

[0064] Furthermore, the method involves the wheel slip limit value λ. lim The step (S2) includes setting the nominal wheel slip limit value λ. lim This indicates the maximum allowable wheel slip by at least one driven wheel and / or braking wheel 102. This essentially means that the wheel speed is limited by the system so that the resulting wheel slip does not exceed the wheel slip limit. Similarly, the wheel speed relative to the vehicle speed can be limited so that the wheel slip does not exceed the wheel slip limit. The nominal wheel slip limit may simply be predetermined, i.e., hardcoded at assembly. However, some aspects of the method also include a step (S22) of determining the nominal wheel slip limit based on an inverse tire model, where the inverse tire model represents the relationship between the wheel slip λ and the wheel force Fx of at least one driven wheel and / or braking wheel 102. An example of this inverse tire model is described above, for example, in relation to Figure 2. The inverse tire model may be used to set the wheel slip limit by, for example, selecting a wheel slip corresponding to 0.9 of the peak wheel force. This provides some margin with respect to nonlinear regions where operation is often undesirable. The reverse tire model may be fixed, or it may be dynamically updated based on the measured vehicle behavior with various wheel slip values.

[0065] The nominal wheel slip limit may be too small in some cases due to, for example, an incorrect reverse tire model, an error in the estimated road surface friction condition, or an inaccurate tire model. Therefore, the method is to set the wheel slip limit value λ. lim The process includes step (S3) of increasing the magnitude of the boost wheel slip limit from the nominal wheel slip limit to the boost wheel slip limit in response to the detection of the boost signal 361. As previously mentioned, this may mean increasing the positive wheel slip value (propulsion wheel slip limit) and / or decreasing the negative wheel slip value (braking wheel slip limit).

[0066] The generation of a boost signal can be based on one or more triggers and, in some cases, also conditioned on one or more parameters. A trigger is some form of event that causes the generation of a boost signal only when all set conditions are met. For example, the generation of a boost signal S32 optionally includes an accelerator pedal position exceeding a threshold. Thus, a boost signal is generated when the driver fully depresses the pedal, for example, beyond 80% of the full pedal range, and all set conditions are also met. The boost signal may be configured to be generated by a mechanical or electrical switch when the accelerator pedal or brake pedal is fully depressed. In a further embodiment, the boost signal is triggered when the accelerator pedal position or brake pedal position exceeds a threshold for a predetermined period of time (S38). In this case, the driver must depress the pedal for a specific period of time prior to the boost function discussed herein being triggered.

[0067] The boost signal S33 may be configured to be triggered by the operation of a manual trigger device. This manual trigger device may be, for example, a button inside the cabin or a menu selection option in the vehicle's control system. Thus, a driver who wants to obtain further wheel slip beyond the set nominal wheel slip limit can activate the manual trigger device to shift the wheel slip limit to a larger value.

[0068] Of course, the boost signal S39 may be configured to be triggered remotely by the operation of a remote control trigger device. For example, a remote control tower may have a remote control system that implements a function to remotely activate the boost function to increase the magnitude of the set wheel slip limit from the nominal wheel slip limit to the boost wheel slip limit. In this case, the remote control trigger device implements a function that allows a given vehicle to operate at a higher wheel slip limit compared to the nominal setting, which may be desirable in some scenarios. For example, when there are no other vehicles nearby, operating at a higher wheel slip may be considered safer, and it may be determined that a further increase in wheel slip is beneficial from the standpoint of vehicle motion management performance.

[0069] The boost signal S34 may be conditional on the vehicle 100 operating at a speed below the vehicle speed tolerance threshold. This means that if the vehicle is moving too fast, an increase in the magnitude of the wheel slip limit is not permitted, otherwise there is a higher risk that the vehicle may become unstable or otherwise enter an undesirable state. The boost signal generation S35 may also be conditional on the vehicle 100 operating with yaw motion below the vehicle yaw motion tolerance threshold. Therefore, if the vehicle is turning excessively, i.e., following a path with too much curvature, an increase in the wheel slip limit is not permitted. It can be seen that if the vehicle is moving very slowly, the yaw motion condition can be ignored. Therefore, if the vehicle 100 is operating at a speed below the vehicle speed tolerance threshold, more yaw motion may be permitted compared to when the vehicle is moving faster.

[0070] The method may further include the step (S36) of determining the lateral force requirement (lateral force requirement) of at least the driven wheel and / or the braking wheel 102. In this case, the generation of the boost signal may be conditional on the lateral force requirement being less than the lateral force requirement threshold. The rationale for this is that the lateral force that can be generated when the wheel is operating with too much longitudinal wheel slip is very small. Therefore, if a lateral force is generated, it may not be wise to increase the wheel slip to a level where such a lateral force cannot be generated. However, it can be seen that the low speed condition may take precedence over the lateral force requirement condition.

[0071] The method involves setting a wheel slip limit value λ. lim The method may further include the step (S37) of increasing the wheel slip limit from the nominal wheel slip limit to the boost wheel slip limit only for a predetermined period of time. This means that the increase in the wheel slip limit to the boost level is only temporary, for example, to prevent the vehicle from getting stuck in the road. The predetermined period can be set to, for example, 1 to 5 seconds. Another period of increased wheel slip may be permitted after, for example, a pause of a few seconds. The method also includes a set wheel slip limit λ lim In accordance with, and the motor requirement a req The step (S4) also includes controlling at least one driven wheel and / or braking wheel 102 depending on the set wheel slip limit value λ. lim In accordance with, and the motor requirement a req Methods for controlling driven wheels and / or braking wheels by relying on the above are known in the art and will therefore not be described in further detail herein. Several examples of such methods are given in relation to Figure 5 above.

[0072] The methods disclosed herein optionally include a motor request a reqThe process also includes the steps of: determining a target wheel slip value λ as a nominal target wheel slip value (S21) depending on and on an inverted tire model 200 that represents the relationship between wheel slip λ and longitudinal wheel force Fx; increasing the target wheel slip value λ from the nominal target wheel slip value to a boost wheel slip value in response to the detection of a boost signal 361 (S31); and controlling at least one driven wheel and / or braking wheel 102 depending on the target wheel slip value λ (S41).

[0073] In a further embodiment, the method also includes the step (S5) of updating the reverse tire model associated with at least one driven wheel and / or braking wheel 102 in response to the detection of a boost signal 361. These embodiments are meaningful when the reverse tire model is adjusted continuously or periodically (periodically), for example, based on estimated longitudinal wheel force. In this case, the VMM system can maintain a record of wheel slip and corresponding estimated or measured wheel force values. For example, some electromachines emit an output signal that indicates the applied torque in real time, which can be converted into wheel force. However, the reverse tire model will be inaccurate with respect to large slip values ​​that exceed a set wheel slip limit, because such values ​​will not occur unless those slip values ​​are temporarily tolerated using a boost mode.

[0074] The objective can also be achieved by a computer-implemented method for controlling at least one driven wheel and / or braking wheel of a large vehicle. This method includes the steps of: obtaining a motion request indicating a desired longitudinal force (intended) generated by one or more wheels of the vehicle; setting a nominal relationship (such as an inverted tire model) between wheel slip and longitudinal force based at least partially on slip stiffness values; obtaining a driver input signal indicating a desired adjustment of the nominal slip stiffness values; resetting (reconfiguring) the nominal relationship between wheel slip and longitudinal force to take into account the desired adjustment of the slip stiffness values; and controlling at least one driven wheel and / or braking wheel depending on the motion request and based on the adjusted relationship between wheel slip and longitudinal force.

[0075] Therefore, a driver input signal, which may be the aforementioned boost signal, is used to adjust the characteristics of the perceived vehicle dynamics. In this way, by adjusting the relationship between wheel slip and longitudinal force, an effect similar to the aforementioned boost mode can be obtained. The parameterization of this type of inverse tire model can, of course, also be used to adjust the assumed peak point of force application in the relationship between tire force and wheel slip, which, of course, affects the wheel slip limit when this wheel slip limit is set depending on the peak position, as explained in relation to Figure 2 above.

[0076] Figure 7 schematically shows the components of the control unit 700 according to the embodiments described herein, such as either the MSD control system 330 or the VMM system 360, with respect to some functional units. The processing circuit 710 is provided using one or more of any combination of suitable central processing units (CPUs), multiprocessors, microcontrollers, digital signal processors (DSPs), etc., which can execute software instructions stored in a computer program product, for example, in the form of a storage medium 730. The processing circuit 710 may further consist of at least one application-specific integrated circuit (ASIC) or field-programmable gate array (FPGA). In particular, the processing circuit 710 is configured to cause the control unit 700 to execute a set of operations or steps, such as the method generally described herein in relation to Figure 9. For example, the storage medium 730 may store a set of operations, and the processing circuit 710 may be configured to retrieve a set of operations from the storage medium 730 and cause the control unit 700 to execute the set of operations. The set of actions may be given as a set of executable instructions. Thus, the processing circuit 710 is configured to perform the method disclosed herein. In particular, the processing circuit 710 receives motion requests a that indicate a desired longitudinal acceleration or a desired longitudinal force to be generated by the vehicle 100. req Obtain the wheel slip limit value λ which indicates the maximum allowable wheel slip by at least one driven wheel and / or braking wheel 102. lim The nominal wheel slip limit value is set to λ, and the set wheel slip limit value λ lim In response to the detection of the boost signal 361, the boost wheel slip limit is increased from the nominal wheel slip limit to the boost wheel slip limit, and motion request a req Depends on and the set wheel slip limit value λ lim It is configured to control at least one driven wheel and / or braking wheel 102 accordingly.

[0077] Furthermore, the storage medium 730 may include a persistent storage device which can be any one or a combination of, for example, magnetic memory, optical memory, solid memory, or remotely implemented memory.

[0078] The control unit 700 may further include an interface 720 for communicating with at least one external device. Accordingly, the interface 720 may include one or more transmitters and receivers having analog and digital components and an appropriate number of ports for wired or wireless communication.

[0079] The processing circuit 710 controls the general operation of the control unit 700, for example, by transmitting data and control signals to the interface 720 and the storage medium 730, by receiving data and reports from the interface 720, and by retrieving data and instructions from the storage medium 730. Other components and related functions of the control node are omitted in order to avoid obscuring the concepts presented herein.

[0080] Figure 11 shows a computer-readable medium 810 that holds a computer program including program code means 820 for performing the method shown in Figure 6 and the techniques described herein when the program product is executed on a computer. The computer-readable medium and the code means together can form a computer program product 800.

Claims

1. 1. A computer-implemented method for controlling at least one driven wheel and / or braking wheel (102) of a heavy vehicle (100), comprising: A motion demand (a) indicating a desired longitudinal acceleration and / or a desired longitudinal force associated with the vehicle (100). ｒｅｑ , F ｘ ) (S1); The wheel slip limit (λ ｌｉｍ ) to the nominal wheel slip limit (S2); and The set wheel slip limit value (λ ｌｉｍ increasing (S3) the magnitude of the boost wheel slip limit (361) from the nominal wheel slip limit to a boost wheel slip limit in response to detecting a boost signal (361); Including, the inverse tire model represents a relationship (200) between wheel slip and wheel force at the wheel (102); The wheel slip limit value (λ ｌｉｍ ) denotes the maximum allowable wheel slip by said at least one driven wheel and / or braking wheel (102), The method comprises: The set wheel slip limit value (λ ｌｉｍ ) and according to the exercise request (a ｒｅｑ , F ｘ (S4) controlling the at least one driven wheel and / or braking wheel (102) depending on Also includes a method.

2. Wheel slip (λ) and longitudinal wheel force (F ｘ ) and the motion demand (a ｒｅｑ , F ｘ determining a target wheel slip value (λ) as a nominal target wheel slip value (S21), In response to detecting the boost signal (361), increasing the target wheel slip value (λ) from the nominal target wheel slip value to a boost target wheel slip value (S31); and controlling (S41) the at least one driven wheel and / or braking wheel (102) in dependence on the target wheel slip value (λ); The method of claim 1 further comprising:

3. the movement demand (a) as a function of the accelerator pedal position or the brake pedal position; ｒｅｑ , F ｘ 2. The method of claim 1, further comprising: obtaining (S11) the first and second data sets.

4. The motion request (a) is sent from a motion support device (MSD) adjustment function (530) of a vehicle motion management (VMM) system provided in the large vehicle (100). ｒｅｑ , F ｘ 2. The method of claim 1, further comprising: obtaining (S12) the first and second data sets.

5. The vehicle (100) is provided with an autonomous or semi-autonomous driving function to request the movement (a ｒｅｑ , F ｘ 2. The method of claim 1, further comprising: obtaining (S13) the first and second data sets.

6. Determining (S22) the nominal wheel slip limit based on an inverse tire model (200), the inverse tire model comprising a function of wheel slip (λ) and wheel force (F) of the at least one driven wheel and / or braking wheel (102). ｘ 2. The method of claim 1, wherein the relationship between

7. 2. The method of claim 1, wherein the boost signal (S32) is triggered by an accelerator pedal position or a brake pedal position exceeding a threshold value.

8. The method of claim 1 , wherein the boost signal (S33) is configured to be manually triggered by operation of a triggering device.

9. 2. The method of claim 1, wherein the boost signal is conditioned on the vehicle being operated at a speed below a vehicle speed tolerance threshold.

10. 2. The method of claim 1, wherein the boost signal is conditioned on the vehicle being operated with a yaw motion less than a vehicle yaw motion tolerance threshold.

11. 2. The method of claim 1, comprising determining (S36) a lateral force demand of at least a driven wheel and / or a braking wheel (102), wherein the boost signal is conditioned on the lateral force demand being less than a lateral force demand threshold.

12. The set wheel slip limit value (λ ｌｉｍ 2. The method of claim 1, further comprising: increasing (S37) the nominal wheel slip limit from the nominal wheel slip limit to the boost wheel slip limit only during a predetermined period of time.

13. 2. The method of claim 1, wherein the boost signal (S38) is triggered by an accelerator pedal position or a brake pedal position exceeding a threshold for a predetermined period of time.

14. The method of claim 1 , wherein the boost signal (S39) is configured to be remotely triggered by operation of a remotely controlled triggering device.

15. 2. The method of claim 1, comprising updating (S5) an inverse tire model associated with the at least one driven wheel and / or braking wheel (102) in response to detecting the boost signal (361).

16. A computer program comprising program code means for performing the steps of any one of claims 1 to 15 when the computer program is run on a computer.

17. A control unit (300, 400, 500, 700) for controlling at least one driven wheel and / or braking wheel (102) of a heavy vehicle (100), comprising a processing circuit (710), said processing circuit comprising: A motion demand (a) indicating a desired longitudinal acceleration and / or a desired longitudinal force associated with the vehicle (100). ｒｅｑ , F ｘ ) and a wheel slip limit value (λ ) indicating the maximum allowable wheel slip by said at least one driven wheel and / or braking wheel (102); ｌｉｍ ) to the nominal wheel slip limit, The set wheel slip limit value (λ ｌｉｍ ) from the nominal wheel slip limit to a boost wheel slip limit in response to detecting a boost signal (361); It is also structured as follows: The set wheel slip limit value (λ ｌｉｍ ) and according to the exercise request (a ｒｅｑ , F ｘ ) controlling the at least one driven wheel and / or braking wheel (102) depending on The control unit is configured to:

18. A heavy vehicle (100) comprising a control unit according to claim 17.

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