Reverse tire model boost function for large vehicles

Abstract

A computer-implemented method for controlling at least one driven and / or braked wheel (102, 310) of a heavy vehicle (100), comprising: setting (S1) a default inverse tire model and a boost inverse tire model, each of the inverse tire models representing a respective relationship (200) between longitudinal wheel slip (λ) and longitudinal wheel force (Fx) at the wheel (102, 310), the boost inverse tire model providing a higher maximum wheel slip value (λ) of the wheel (102, 310) compared to the default inverse tire model. lim ) and the desired longitudinal force (F) generated by the wheels (102, 310). x ) indicating the motor demand (a req ) (S2); in response to detecting a boost signal, selecting a boost inverse tire model as the active inverse tire model, and if not, selecting a default inverse tire model as the active inverse tire model (S3); and req and controlling (S4) at least one driven and / or braked wheel (102, 310) based on an active inverse tire model in response to the determined vehicle speed.

Description

[Technical Field]

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

[0002] Traditionally, large vehicles have been controlled using torque request signals determined based on accelerator or brake pedal position and transmitted via a digital interface to motion support devices (MSDs) such as service brakes and propulsion systems. However, advantages can sometimes be gained by controlling actuators using wheel slip requests or wheel speed requests transmitted from a central vehicle controller to various actuators. This brings actuator control closer to the wheel ends, reducing latency and enabling faster and more precise control of the MSDs. The wheel slip-based MSD control approach is particularly well-suited for use in wheel end electromechanics of battery or fuel cell vehicles, allowing for high-bandwidth and precise control of axle speed. Wheel slip-based vehicle motion management and its associated advantages are described, for example, in WO2017 / 215751 and WO2021 / 144010.

[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, and is frequently referred to as the inverse tyre model. However, large vehicles are complex dynamic mechanical systems that are difficult to model accurately, and their behavior can change rapidly in response to changes in road friction conditions or wheel normal force, for example. Therefore, the inverse tyre model is not always perfectly accurate and can lead to performance degradation in wheel slip-based or wheel speed-based control systems for large vehicles.

[0004] There is a need for a vehicle motion management method that is more tolerant of errors in the approximate relationship between wheel slip and the resulting longitudinal wheel force. [Overview of the Initiative]

[0005] The object of this disclosure is to overcome at least partially the aforementioned shortcomings and to provide an improved method for controlling heavy vehicles. This object is achieved by a computer implementation method for controlling at least one driven and / or braked wheel of a heavy vehicle. The method involves setting a default inverse tyre model and at least one boost inverse tyre model, each inverse tyre model representing the respective relationship between longitudinal wheel slip and longitudinal wheel force at the wheel, and the boost inverse tyre model having a higher maximum wheel slip value (λ) of the wheel compared to the default inverse tyre model. limThe method also includes: obtaining a motion request indicating a desired longitudinal force generated by a wheel; selecting a boosted reverse tire model as the active reverse tire model in response to detecting a boost signal, or, if not detected, selecting a default reverse tire model as the active reverse tire model; and controlling at least one driven and / or braked wheel based on the active reverse tire model in response to the motion request.

[0006] In this way, for example, the maximum acceptable wheel slip, determined by the wheel slip limit associated with the active reverse tire model, can be temporarily increased by generating a boost signal. This function may 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 wheel slip exceeding the default wheel slip limit is desirable and provides an additional boost. The disclosed method provides a vehicle motion management method that is more tolerant of errors in the approximate relationship between wheel slip and the resulting longitudinal wheel force. The proposed method can selectively activate the boost reverse tire model for a single wheel, axle wheels, or three or more wheels of the vehicle, depending on the driving scenario and the desired effect on the overall motion of the vehicle.

[0007] The default reverse tire model and boost reverse tire model can be configured in several different ways, and two or more boost reverse tire models can also be configured and selected, for example, by using a boost signal where each boost signal level has two or more levels corresponding to the activation of each boost reverse tire model from a set of boost reverse tire models.

[0008] In some embodiments, the method includes configuring a boosted inverted tire model to have a peak longitudinal wheel force corresponding to a higher wheel slip value compared to the peak longitudinal wheel force of the default inverted tire model, such that the maximum force requirement results in higher wheel slip when using the boosted inverted tire model compared to when using the default inverted tire model. In other embodiments, the boosted inverted tire model is configured with a smaller slip stiffness value compared to the default inverted tire model, which also results in a given wheel force mapping to a higher wheel slip in the boosted inverted tire model compared to the default inverted tire model. In further embodiments, the boosted inverted tire model simply has a higher wheel slip limit compared to the default inverted tire model; that is, the two models are essentially the same, but the wheel slip limit is configured differently to allow higher wheel slip to occur by the wheel compared to when using the default inverted tire model. For example, the wheel slip limit may be configured at a first distance from the peak force position of the default inverted tire model and at a second distance from the peak force position of the boosted inverted tire model.

[0009] The motion demand can be obtained, for example, as a function of the accelerator pedal position or brake pedal position, allowing the driver to conveniently initiate boost mode by, for example, pressing the pedal fairly hard beyond a predetermined threshold or for a predetermined period of time. This method is most useful in relation to acceleration, i.e., forward movement, but it is understood that important applications can also be found in relation to deceleration, i.e., sudden braking.

[0010] Alternatively, or as a supplement to the boost mode pedal position trigger, motion requests may be obtained from the MSD coordination function of the VMM (vehicle motion management) system included in the large vehicle, and / or from the autonomous or semi-autonomous driving function included in the large vehicle, as will be described in more detail below. This means that the vehicle control function has the option to temporarily increase wheel slip to obtain a boost, for example, if an overly conservative slip limit is considered to be set, at least temporarily. This increases the degree of freedom of control for the autonomous or semi-autonomous control algorithm, which is an advantage.

[0011] The boost signal may be triggered, for example, when the accelerator pedal position or brake pedal position exceeds a threshold. The boost signal may also be manually triggered by operating a trigger device such as a button or switch in the cabin. Naturally, this type of trigger device may consist of two or more levels as described above, and may therefore be used to select a boosted reverse tire model from a set of two or more reverse tire models that should be the active reverse tire model. The boost signal may also be triggered when the accelerator pedal position or brake pedal position exceeds a threshold for a predetermined period of time.

[0012] To ensure that the stability of the vehicle (a large vehicle) is not impaired, the boost signal is optionally conditioned on the vehicle operating at a speed below the allowable threshold of the vehicle speed. Thus, even if the driver fully depresses the pedal or presses the manual boost signal generation button in the passenger compartment, if the vehicle's moving speed is too high, the boost signal is not generated (and the boost reverse tire model is not selected as the active reverse tire model). The generation of the boost signal can also be conditioned on the vehicle operating with a yaw motion below the allowable threshold of the vehicle yaw motion, and as a result, the boost reverse tire model is not selected if the yaw motion is too large. This means that when the vehicle is cornering, the method can be configured so that the boost mode is not permitted because the normal completion of the turning operation may be jeopardized. The reason is that as the longitudinal wheel slip increases, the ability to generate lateral force decreases, which can occur when the boost reverse tire model is the active reverse tire model. Similarly, this method naturally includes determining at least the lateral force requirements of the driven and / or braked wheels, and the boost signal can be conditioned on the lateral force requirement being below the lateral force requirement threshold. In this way, the stability and safety of the vehicle are not impaired by the potential increase in wheel slip allowed when the boost reverse tire model is the active reverse tire model.

[0013] This method may also include selecting the boost reverse tire model as the active reverse tire model for only a predetermined period. After this period, the reverse tire model setting can be returned to, for example, the default setting or some other provisional value, i.e., gradually returned to the default reverse tire model. This can prevent, for example, the vehicle's wheels from biting into the road surface, which is of course an advantage.

[0014] According to an aspect, the boost signal is configured to be remotely triggered by an operation of a remote control trigger device. Thereby, an operator or an autonomous function outside the vehicle triggers the boost mode, for example, enabling the vehicle to pass through a difficult slope or the like. In this way, additional functions may be imparted to the vehicle by a remote agency, which may be an advantage in some situations, for example, in a limited area where an autonomous vehicle needs to operate with a fairly conservative wheel slip value to ensure safe operation. The remote agency may temporarily allow an autonomous vehicle or a semi-autonomous vehicle to operate at a higher wheel slip value in order to temporarily enhance the maneuverability of the vehicle and get out of a situation where the vehicle cannot move or where an improvement in starting performance is required.

[0015] This method may also include updating a default inverse tire model associated with at least one driven and / or braked wheel in response to the detection of the boost signal. This means that the inverse tire model used to manage the movement of the vehicle under normal operating conditions is improved over time, leading to a more accurate inverse tire model, which is an advantage. When updating the inverse tire model in this way, it may be advantageous to check what happens when wheel slip is temporarily allowed to increase beyond a set wheel slip limit that is permitted when the boost inverse tire model is selected as the active inverse tire model.

[0016] Also disclosed herein are control units, vehicle units, computer programs, computer-readable media, and computer program products associated with the advantages described above.

[0017] In general, all terms used in the claims should be interpreted according to their ordinary meaning in the art unless otherwise explicitly stated herein. All references to “elements, apparatus, components, means, steps, etc.” should be openly interpreted as referring to at least one example of elements, apparatus, components, means, steps, etc. unless otherwise explicitly stated. The steps of any method disclosed herein do not need to be performed in the exact order disclosed unless otherwise explicitly stated. Further features of the invention and the advantages associated with the invention will become apparent upon consideration of the appended claims and the following description. As those skilled in the art will understand, different features of the invention can be combined to create embodiments other than those described below without departing from the scope of the invention.

[0018] The foregoing, as well as any additional purposes, features, and benefits, will be better understood through the non-limiting detailed description for the following exemplary embodiments. [Brief explanation of the drawing]

[0019] [Figure 1] This is a diagram illustrating a large vehicle. [Figure 2] This graph shows an example of tire force as a function of wheel slip. [Figure 3] This figure shows an example of a control configuration for an exercise support device. [Figure 4] This figure shows an exemplary configuration of wheel slip boost. [Figure 5] This figure shows an example of a vehicle control function architecture. [Figure 6] This figure shows several exemplary default and boost reverse tire models. [Figure 7] This figure shows several exemplary default and boost reverse tire models. [Figure 8] This figure shows several exemplary default and boost reverse tire models. [Figure 9] This is a flowchart of the method. [Figure 10] This is a schematic diagram of the control unit. [Figure 11] This figure shows examples of computer program products. [Modes for carrying out the invention]

[0020] This disclosure is described in its entirety below with reference to the accompanying drawings illustrating exemplary embodiments. However, this disclosure may be embodied in many different forms and should not be construed as being limited to the embodiments described herein, but rather these embodiments are provided for the sake of completeness and completeness. Throughout this description, similar reference letters refer to similar elements.

[0021] Figure 1 shows an exemplary heavy vehicle 100, in the form of a truck. The vehicle has a plurality of wheels 102, and at least a subset of the wheels 102 are equipped with a motion assist device (MSD) 104. Although the embodiment shown in Figure 1 shows an MSD for each wheel 102, of course, a pair of wheels 102 may be configured without such an MSD 104. Also, the MSDs may be connected to two or more wheels, for example, via a differential device.

[0022] Naturally, the methods and control units disclosed herein can also be advantageously applied to other types of heavy vehicles, such as trucks, construction machinery, and buses, equipped with drawbar connections. Vehicle 100 may include three or more vehicle units; that is, it may use a bogie vehicle unit to tow two or more trailers.

[0023] The MSD 104 may be positioned to generate torque on each wheel or on both wheels of the axle of the vehicle. The MSD may be a propulsion device such as an electromachine 106 configured to provide longitudinal wheel force to the wheel(s) of the vehicle 100. Thus, such an electromachine may be adapted to generate propulsion torque as well as to be configured in a regenerative braking mode for charging the battery(s) of the vehicle 100 or other energy storage system(s) (not shown). The electromachine may generate braking torque without storing energy. For example, excess energy may be dissipated from the electromachine during braking using a braking resistor or the like.

[0024] The MSD104 may also be equipped with friction brakes, such as disc brakes or drum brakes, arranged to generate braking torque by the wheels 102 to decelerate the vehicle. Here, the term acceleration is to be interpreted broadly to include both positive acceleration (propulsion) and negative acceleration (braking).

[0025] The methods disclosed herein primarily relate to controlling the propulsion, i.e., acceleration, of large vehicles. However, the disclosed methods may also be used during deceleration, i.e., braking, of large vehicles.

[0026] Furthermore, each MSD 104 is connected to its respective MSD control system or control unit 330, which is positioned 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 should be understood that some components of the MSD control system, such as a remote server 120 accessible from the vehicle via a wireless link, may be implemented on a processing circuit located away from the vehicle. In addition, 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 are described in more detail below with reference to Figures 3 and 5.

[0027] 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(s) include 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. Various implementations of vehicle unit processing circuits are described in more detail below in relation to Figure 10.

[0028] In general, MSDs on vehicle 100 may be implemented as, for example, a power steering system, an active suspension system, etc. While these types of MSDs cannot be used to directly generate longitudinal forces that accelerate or brake the vehicle, they can constitute part of the vehicle motion management methods disclosed herein, as they are part of the overall vehicle motion management of the large vehicle. In particular, the MSDs of large vehicle 100 are often coordinated to obtain a desired motion by the vehicle. For example, two or more MSDs can be used together to generate a desired propulsion torque or braking torque, a desired yaw motion by the vehicle, or some other dynamic behavior.

[0029] Figure 2 is a graph showing two examples of tire forces achievable as a function of longitudinal wheel slip. This type of relationship between wheel slip and the resulting tire force is referred to here as the inverse tire model. The inverse tire model can be expressed as a function as shown in Figure 2, or as a simple piecewise linear approximation over a portion of the wheel slip range, as shown in Figures 7 and 8, which will be discussed in more detail below. The example in Figure 2 is for positive wheel force, i.e., acceleration. A similar relationship exists between wheel slip and negative wheel force, i.e., braking.

[0030] Vertical wheel slip λ x According to SAE J370 (SAE Vehicle Dynamics Standards Committee, January 24, 2008), it can be defined as follows:

number

[0031] For a wheel (or tire) to generate wheel forces, slip needs to occur. When the slip value is small, the relationship between slip and the generated force is approximately linear, and the proportionality constant is often the slip stiffness C x of the tire, represented as 260, 270. The tire is subjected to a longitudinal force F x , a lateral force F y , and a normal force F z . The normal force F z is the key to determining several important vehicle characteristics. For example, the normal force determines to a significant extent the tire longitudinal force F x that can be achieved by the wheel. This is because usually F x ≦μF z . Here, μ is the friction coefficient associated with the road friction conditions. The maximum available lateral force for a given wheel slip can be described by the so-called Magic Formula as explained in "Tyre and vehicle dynamics", Elsevier Ltd. 2012, ISBN 978-0-08-097016-5 (by Hans Pacejka), and the wheel slip and tire forces are also described in detail.

[0032] Using the reverse tire model, the desired tire longitudinal force F x This can be converted to wheel slip λ. The interface between the VMM and MSD, which can transmit 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 situations where safety is paramount or excessive slip occurs, relevant safety functions (such as traction control and anti-lock brakes), operating on separate control units, typically intervene and request torque override to bring the slip back into control. The problem with this approach is that the slip control performance is significantly limited by the latency associated with communication between the primary control of the actuator and the slip control of the actuator, as these are assigned to different electronic control units (ECUs). Furthermore, the assumptions about the relevant actuators and slip made in the two ECUs used to implement the actual slip control may not match, which can lead to suboptimal performance. Alternatively, significant advantages can be realized by using wheel speed or wheel slip-based requirements in the interface between the VMM360 and one or more MSD controllers 330, thereby offloading the complex actuator speed control loop to the MSD controllers, which generally operate with significantly shorter sample times compared to the VMM functions. Such an architecture provides far superior disturbance rejection compared to torque-based control interfaces, thus improving the predictability of forces generated at the tire road contact.

[0033] Referring again to Figure 2, the exemplary tire longitudinal forces Fx1 and Fx2 show a nearly linearly increasing portion 210 for small wheel slips, followed by a more nonlinear behavior in portion 220 for large wheel slips. It is desirable to maintain vehicle operation in the linear region 210. In the linear region 210, the longitudinal forces obtainable in response to applied brake commands are more predictable, and sufficient tire lateral forces can be generated as needed. To ensure operation in this region, a wheel slip limit λ of, for example, about 0.15 is desirable. lim A force of 230 can be imposed on a given wheel.

[0034] Tire model Fx1 represents a high-friction scenario, i.e., a dry road with good tires, while Fx2 represents a reduced-friction scenario. It should be noted that the maximum achievable tire force decreases with increasing friction coefficient μ. Also, note that the wheel slip values ​​corresponding to peak wheel force shift slightly between the two curves; the peak of 240 in curve Fx1 occurs at a higher wheel slip compared to the peak of 245 in curve Fx2. Therefore, the wheel slip limit λ is set with some margin to the left of the peak of 245 in curve Fx2. lim This could be overly conservative if the curve Fx1 actually closely resembles the real relationship between wheel slip and wheel force.

[0035] Generally, it is advantageous to set the wheel slip limit 230 in accordance with the reverse tire model rather than as a predetermined or hardcoded parameter. For example, a wheel slip limit set for the peak value of the assumed reverse tire model will match the vehicle's current operating conditions. However, it may still be desirable to override the slip limit set based on the assumed reverse tire model and generate higher wheel slip than normally permitted by the system with the default reverse tire model. For example, the default reverse tire model may be unintentionally overly conservative, meaning that the slip limit of the default reverse tire model prevents operation at the desired wheel slip, thus preventing the vehicle from utilizing its full potential traction or braking force. In fact, it may be desirable to temporarily use a more "aggressive" reverse tire model that allows for more wheel slip compared to the default reverse tire model used in other ways. Such a more aggressive reverse tire model may be desirable for one or more wheels or one or more axles of the vehicle.

[0036] For example, suppose that heavy vehicle motion management uses the reverse tire model with curve Fx2 as the default reverse tire model, and that in reality curve Fx1 more accurately models the true relationship between wheel slip and longitudinal wheel force. Furthermore, suppose that to ensure operation in the linear region 210, the wheel slip limit is set at 230 for the default reverse tire model Fx2. This slip limit prevents the vehicle from generating more wheel force than indicated by the dashed line F in Figure 2, which is far below the maximum achievable wheel force F' at the true peak 240.

[0037] To enable a driver or any other form of vehicle controller, such as an autonomous or semi-autonomous driving system, to override a default reverse tire model that is set not to potentially allow sufficient wheel slip to be generated by some of the wheels on the vehicle 100, it is proposed herein to allow a temporary shift to a boost reverse tire model that enables the generation of more wheel slip. One or more such boost reverse tire models can be set by the system and then temporarily activated as needed in response to some form of boost signal, for example, this boost signal can be triggered, for example, by the driver pressing down on the accelerator or brake pedal beyond a certain threshold, or by the driver operating an in-cabin manual control such as a boost button on the dashboard. In certain vehicles and use cases, including both autonomous and human-centered driving modes, it may be desirable to give the human driver more control authority than the automated driver, and the techniques disclosed herein may be used to provide such an increased level of control over acceptable wheel slip and general vehicle behavior.

[0038] The boost signaling mechanism may also be used by some remote engines, such as control towers, to allow some vehicles to temporarily operate at high slip values ​​when it is desirable that such high wheel slip operation may be considered advantageous and safe.

[0039] Furthermore, if the reverse tire model is updated in real time based on observed vehicle behavior, it may be beneficial in some situations for wheel slip to exceed the peak of the current "known" tire model. When the vehicle is being driven by a human driver, the accelerator pedal can be used to "force" a higher slip target in certain situations, and some additional traction performance can be obtained (for example) if the parameterization of the current tire model is overly conservative. In this way, the vehicle controller can "probe" the relationship between wheel force and wheel slip beyond the assumed peak wheel force slip of the default reverse tire model, at least temporarily.

[0040] In discussions of functional safety, adding this type of wheel slip limit "override" can reduce the number of functional safety requirements that would be placed in the reverse tire model, as a human driver can always override to a higher slip target in critical situations (e.g., stopping on a train track and attempting to start again).

[0041] Referring 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.

[0042] Figure 3 schematically illustrates a function 300 for controlling an exemplary wheel 310 of a vehicle 100 by several exemplary MSDs, including a friction brake 320 (such as a disc brake or drum brake), a propulsion system 340, and a power steering system 330. The friction brake 320 and the propulsion system are examples of wheel torque generating devices and can be controlled by one or more motion assistance control units 330. The control is based, for example, on measurement data obtained from a wheel speed sensor 350 and measurement data obtained from other vehicle condition 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.

[0043] The TSM function 370 plans driving operations within a planning period of approximately 10 seconds. This time frame corresponds, for example, to the time it takes for vehicle 100 to pass through a curve. The vehicle operations planned and executed by the TSM function can be associated with acceleration profiles and curvature profiles that describe the desired target vehicle speeds in the forward direction and turning direction of the vehicle to be maintained by a given operation. The TSM function receives the desired acceleration profile from the VMM function 360, which executes force distribution to meet the requirements from the TSM function in a safe and robust manner. req and steering angle (or curvature profile c) req ) continuously requests. VMM function 360 operates on a timescale of less than approximately 1 second. VMM function 360 is described in more detail below.

[0044] Wheel 310 has a longitudinal velocity component v x and the lateral velocity component v y It has a longitudinal wheel force F. x and lateral wheel force F y There is a normal force F on the wheel. zThis also acts (not shown in Figure 3). Unless otherwise specified, wheel forces are defined in the wheel's coordinate system. That is, longitudinal forces are directed towards the wheel's plane of rotation, and lateral wheel forces are directed perpendicular to the wheel's plane of rotation. The rotational speed of the wheel is ω x The radius is R.

[0045] The type of inverted tire model illustrated by graph 200 in Figure 2 can be used by the VMM360 to generate a desired tire force on a given 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 (i.e., wheel speed relative to ground speed) and request this slip instead. The main advantage is that the MSD control device 330 can, for example, obtain the vehicle speed v from the wheel speed sensor 350. x and wheel rotation speed ω x By using this, the required torque can be transmitted over a much higher bandwidth by maintaining operation at the desired wheel slip. x This information can be obtained from various vehicle sensors, such as radar, lidar, and vision-based sensors, in combination with a Global Positioning System (GPS) receiver.

[0046] The control unit can be configured to store one or more predetermined reverse tire models in memory, for example, as a lookup table or a parameterized function. The reverse tire models may also be configured to be stored in memory as a function of the current operating conditions of the wheel 310. This means that the behavior of the reverse tire model is adjusted according to the vehicle's operating conditions, which means that a more accurate model is obtained compared to one that does not consider the operating conditions. The models stored in memory can be determined based on experimentation and trial, or on analytical derivation, or a combination of the two. For example, the control unit can be configured to access a set of different models selected according to the current operating conditions. One reverse tire model may be adjusted for high-load driving with large normal forces, while another reverse tire model may be adjusted for slippery road conditions, such as low road friction. The selection of the model to be used can be based on a predetermined set of selection rules. Furthermore, the models stored in memory can be, at least partially, a function of the operating conditions. Therefore, the model may be configured to take, for example, normal force or road friction as input parameters, thereby obtaining a reverse tire model according to the current operating conditions of the wheel 310. While many aspects of operating conditions can be approximated by initial operating condition parameters, it is understood that other aspects of operating conditions can be broadly classified into a smaller number of classes. Therefore, obtaining a reverse tire model depending on the current operating conditions of wheel 310 does not necessarily mean that it is necessary to memorize a large number of different models or a complex analytical function that can account for variations in operating conditions at a fine granularity. Rather, it may suffice to have two or three different models that are selected depending on the operating conditions. For example, one model can be used when the vehicle is heavily loaded, and another model when the vehicle is not heavily loaded. In all cases, the mapping between tire force and wheel slip changes in some way depending on the operating conditions, improving the accuracy of the mapping.

[0047] 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 conditions of the vehicle. This can be achieved by continuously 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.

[0048] The reverse tire model can be automatically configured from the remote server 120, for example, as a software update, or it can be manually configured by a technician performing routine vehicle maintenance.

[0049] The VMM module 360 ​​in the example in Figure 3 has at least two different reverse tire models, consisting of a default reverse tire model 361 and a boost reverse tire model 362, the boost reverse tire model 362 being associated with a higher maximum wheel slip value for one or more wheels of the vehicle compared to the default reverse tire model. Thus, the boost reverse tire model allows for more aggressive vehicle control compared to the default reverse tire model. The VMM module also includes a reverse tire model selection module, which is adapted to set the default reverse tire model 361 as the active reverse tire model unless a boost signal is detected. When a boost signal is detected, the reverse tire model selection module sets the boost reverse tire model 362 as the active reverse tire model instead. This means that, at least temporarily, positive drive wheel slip can be greater and negative brake wheel slip can be smaller (more negative) compared to when the default reverse tire model is selected as the active reverse tire model.

[0050] Therefore, the VMM system and MSD controller are made capable of controlling the wheels with wheel slip exceeding the nominal wheel slip limit of the default reverse-tire model, at least temporarily, in order to obtain more aggressive wheel slip behavior compared to the default wheel behavior. For example, if the reverse-tire model used by the VMM function is the Fx2 function in Figure 2, and the Fx1 function is close to the actual relationship, then in boost mode, the vehicle can approach a peak force of 240, at least for a limited period of time. As a result, a driver who wants to drive uphill on a road with difficult road friction conditions can temporarily increase the wheel slip beyond the wheel slip limit of the default reverse-tire model to see if this increases the longitudinal wheel force. This function is essentially similar to the "step-down" or "kick-down" acceleration boost mode found in many passenger cars today.

[0051] Figure 4 shows an example of the tire model selection function 400. There is one input port for motion requests and one input port for boost signals. The tire model module 410 converts the motion request signal into a torque request with wheel slip limits, and / or a wheel slip or wheel speed request, and sends it to the MSD controller 330. The selection module 420 receives the boost signal, which may be a signal indicating, for example, that the accelerator pedal or brake pedal has been pressed down beyond some threshold. Based on the state of the boost signal, the selection module 420 sets the active reverse tire model to be used for controlling the vehicle. In response to detecting a boost signal, it selects the boost reverse tire model 430 as the active reverse tire model; otherwise, it selects the default reverse tire model 440 as the active reverse tire model. In this example, the selection module selects parameters to parameterize the active reverse tire model. Some examples of parameters that can be used to define a reverse tire model are described below in relation to Figures 6-8. However, it should be understood that reverse tire model parameters may include not only a set of tire model parameters, but also the entire tire model.

[0052] 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 specifies a desired steering angle δ or equivalent curvature c that the vehicle should follow. req This may include a desired vehicle unit acceleration a req This may also include other types of vehicle motion requirements, which together describe the desired motion of the vehicle along a desired path at a desired speed profile. It is understood that 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.

[0053] 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 signals are continuously translated into control commands to control the vehicle motion functions operated by various MSDs of the vehicle 100, the MSDs report their capabilities to the VMM, and these are then used as constraints for vehicle control. 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 various units of the vehicle combination, by monitoring the operation using various sensors placed on the vehicle 100, which are often but not necessarily connected to the MSDs.

[0054] The result of motion estimation 510, i.e., the estimated vehicle state s, is input to the force generation module 520, and the force generation module 520 generates the required acceleration profile a for the vehicle 100. req and curvature profile c reqThe overall force V = [V1, V2] required for various vehicle units to move and operate according to the desired vehicle behavior is determined. The required total force vector V is input to the MSD coordination function 530, which assigns wheel forces and coordinates other MSDs such as steering and suspension. The MSD coordination function outputs an MSD control assignment for the i-th wheel, which 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 linked MSDs together provide the desired lateral Fy and longitudinal Fx forces, as well as the required moment Mz, to the vehicle unit in order to obtain the desired motion by the vehicle coupling 100.

[0055] 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 transforming this motion of the vehicle unit into a local coordinate system of a given wheel 310 (for example, with respect to longitudinal and lateral velocity components), 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 positioned in relation to the wheel 310 as described above.

[0056] Accordingly, in some aspects of this disclosure, the VMM function 360 manages both force generation and MSD coordination. That is, the VMM function 360 determines the forces required in the vehicle unit to satisfy a request from the TSM function 370 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, also requested by the TSM. The forces may include, for example, a yaw moment Mz, a longitudinal force Fx, and a lateral force Fy, as well as different types of torque applied to different wheels. The forces are determined in response to a control input generated by the TSM function 370 to produce, for example, the vehicle behavior expected by the TSM function.

[0057] Using the tire model 540 described above in relation to Figure 2, the desired longitudinal tire force Fxi of a given wheel i and the equivalent longitudinal wheel slip λ of the wheel are given. i It is possible to convert between and . This tire model is adapted based on the boost signal as described above, meaning that the active reverse tire model is selected depending on the boost signal, either as the default reverse tire model or as a boosted reverse tire model that can generate more wheel slip for a particular wheel.

[0058] In summary, referring to the flowchart in Figure 9, this specification discloses a computer implementation method for controlling at least one driven and / or braked wheel 102, 310 of a heavy vehicle 100. The method involves setting a default reverse tire model and a boost reverse tire model (S1), where each reverse tire model represents the respective relationship between longitudinal wheel slip λ and longitudinal wheel force Fx in the wheel 102, 310, and the boost reverse tire model represents the maximum wheel slip value λ of the wheel 102, 310 compared to the default reverse tire model. lim This includes a higher correlation. It is understood that two or more boost reverse tire models can be set up, and the boost reverse tire model to use can be selected depending on the vehicle's operating conditions, such as estimated road gradient and friction coefficient.

[0059] In some embodiments, this method includes setting up a boosted inverted tire model having a peak longitudinal wheel force 240 corresponding to a higher wheel slip value compared to the peak longitudinal wheel force of the default inverted tire model (S11). This means that the position of the peak wheel force is shifted to a higher wheel slip value compared to the default inverted tire model. This also means that a system that uses the position of the peak force to set a wheel slip limit, for example, can control a higher wheel slip when using the boosted model compared to when using the default model, as intended. Figure 6 shows an example of this type of reconfiguration, where the default inverted tire model is shown as curve Fx3 with a peak force position 610, and the boosted inverted tire model is shown as curve Fx4 with a peak force position 620. Curve Fx4 is a simply shifted version of curve Fx3, meaning that the position of the peak is shifted towards a higher wheel slip value compared to the peak of the default inverted tire model. The offset of the wheel slip 630 can be set, for example, to wheel slip 0, 1, etc. Two or more offset values ​​can also be used for two or more boosted inverted tire models. The offset can also be gradually increased in response to the detection of a boost signal, and then gradually decreased to zero after a certain period of time. As shown by the dotted line 640 in Figure 6, optional adjustments can be added to the offset curve to zero out the tire force generated to correspond to a zero slip value.

[0060] In another embodiment, this method includes setting up a boosted inverted tire model having a smaller slip stiffness value compared to the default inverted tire model (S12). Figure 7 shows an example of two inverted tire models 700. In this case, the inverted tire models are approximated as linear models given rise by slip stiffnesses Cx1 and Cx2, in which case the slip stiffness value Cx2 of the boosted inverted tire model is smaller compared to the default inverted tire model Cx1. Each inverted tire model is associated with the respective wheel slip limit values ​​710 and 720 at assumed peak force positions 730 and 740. Note that the boosted inverted tire model with slip stiffness Cx2 is associated with a higher maximum wheel slip value compared to the default inverted tire model. Figure 8 shows an example of the default inverted tire model 810 and the boosted inverted tire model 820, where the peak force position p2 of the boosted inverted tire model is higher compared to the peak position p1 of the default inverted tire model. This also means that the boosted reverse tire model can control higher wheel slip compared to the default reverse tire model, which does not allow wheel slip beyond the expected peak position wheel slip limit.

[0061] In another embodiment, this method includes setting up a boosted inverted tire model having a higher wheel slip limit of 230 compared to the default inverted tire model (S13). Thus, the same basic inverted tire model can be used for both the default and boosted models, and it is understood that the wheel slip limit may be changed to distinguish between the two. For example, the wheel slip limit may be defined as 10% wheel slip from the peak for the default inverted tire model, and as wheel slip at the peak for the boosted inverted tire model, or it may be defined as wheel slip exceeding 10% from the peak for the boosted inverted tire model.

[0062] Continuing to refer to Figure 9, this method shows the motion requirement a which represents the desired longitudinal force Fx generated by the wheels 102, 310. reqThis includes obtaining (S2). The motion request may be determined as a function of the accelerator pedal position or brake pedal position of the large vehicle 100, as described above. Motion request a req This information can also be obtained from the MSD coordination function 530 of the VMM system included in the large vehicle 100, or from the autonomous or semi-autonomous driving function included in the vehicle 100.

[0063] Furthermore, this method selects the boost reverse tire model as the active reverse tire model in response to the detection of a boost signal 550, and if it is not detected, selects the default reverse tire model as the active reverse tire model (S3), and motion request a req (S4) includes controlling at least one driven and / or braked wheel 102, 310 based on an active reverse tire model.

[0064] The generation of a boost signal may be based on one or more triggers and may also be conditional 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 S31 optionally includes an accelerator pedal position exceeding a threshold. Thus, when the driver presses the pedal down sufficiently, such as beyond 80% of the full pedal range, a boost signal is generated if all set conditions are also met. The boost signal can also be configured to be generated by a mechanical or electrical switch when the accelerator or brake pedal is fully pressed down. 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. In this case, the driver must press down the pedal for a certain period of time before the boost function described herein is triggered.

[0065] As mentioned above, the boost signal can contain two or more levels, and each level of the boost signal causes the system to select a corresponding boost reverse tire model from among several boost reverse tire models. For example, if the driver presses the accelerator pedal between 70% and 90%, the first boost reverse tire model is selected as the active reverse tire model, and if the driver then presses the same pedal more than 90%, the second boost reverse tire model is selected as the active reverse tire model used for controlling the large vehicle.

[0066] The boost signal S32 may also be configured to be triggered by the operation of a manual trigger device. This manual trigger device may be, for example, a button in the cabin or a menu selection option on the vehicle's control system. Thus, a driver who wants to obtain additional wheel slip beyond the set nominal wheel slip limit may activate the manual trigger device to shift the wheel slip limit to a higher value. This manual trigger device may also, of course, have two or more levels, each corresponding to a boost reverse tire model.

[0067] Naturally, the boost signal can also 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 and increase the magnitude of the set wheel slip limit from the nominal wheel slip limit to the boost wheel slip limit. The remote control trigger device then implements a function that allows a given vehicle to operate at a higher wheel slip limit compared to the nominal configuration, 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 safe, and from the standpoint of vehicle motion management performance, it may be deemed beneficial to further increase the wheel slip.

[0068] The boost signal S33 may be conditional on the vehicle 100 operating at a speed below an acceptable threshold for vehicle speed. This means that an increase in the magnitude of the wheel slip limit is not permitted if the vehicle speed is too high, otherwise there is an increased risk that the vehicle may enter an unstable or undesirable state. Furthermore, the generation of the boost signal S34 may be conditional on the vehicle 100 operating in yaw motion below an acceptable threshold for vehicle yaw motion. Therefore, if the vehicle is making a large turn, i.e., following a path with too much curvature, an increase in the wheel slip limit is not permitted. It is understood that if the vehicle is moving very slowly, the yaw motion condition may be ignored. Therefore, if the vehicle 100 is operating at a speed below an acceptable threshold for vehicle speed, a larger yaw motion may be permitted compared to when the vehicle is moving faster.

[0069] This method may further include determining the lateral force requirements of at least the driven and / or braked wheels 102 (S35). The generation of a boost signal may be conditional on the lateral force requirements being below a lateral force requirement threshold. This is because little lateral force is generated when the wheels are operating with excessively large longitudinal wheel slip. Therefore, if lateral force needs to be generated, it may be inappropriate to allow an increase in wheel slip to a level where such lateral force cannot be generated. However, it is understood that conditions relating to low speed may take precedence over conditions relating to lateral force requirements.

[0070] In a further embodiment, the method also includes updating the default reverse tire model associated with at least one driven and / or braked wheel 102 in response to the detection of a boost signal (S5). These embodiments are relevant when the reverse tire model is adjusted continuously or periodically based, for example, on estimated longitudinal wheel forces. In this case, the VMM system can maintain a record of wheel slip and the corresponding estimated or measured wheel force values. For example, some electromachines can provide an output signal indicating the applied torque in real time, which can be converted into wheel force. However, the reverse tire model becomes inaccurate because large slip values ​​exceeding the set wheel slip limit will not occur unless temporarily permitted using boost mode.

[0071] Figure 10 schematically shows the components of the control unit 1000 according to the embodiments described herein, such as either the MSD control system 330 or the VMM system 360, in the form of several functional units. The processing circuit 1010 is provided using one or more arbitrary combinations of suitable central processing units (CPUs), multiprocessors, microcontrollers, digital signal processors (DSPs), etc., which can execute software instructions stored in a computer program product in the form of a storage medium 1030. The processing circuit 1010 may further be provided as at least one application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). In detail, the processing circuit 1010 is configured to cause the control unit 1000 to perform a set of operations or steps, such as in relation to Figure 9 and in the methods generally described herein. For example, the storage medium 1030 may store a set of operations, and the processing circuit 1010 may be configured to read a set of operations from the storage medium 1030 and cause the control unit 1000 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Therefore, the processing circuit 1010 is configured to perform the method disclosed herein.

[0072] For example, the storage medium 1030 may also include a persistent storage device which is any single or combination of magnetic memory, optical memory, solid-state memory, or further remotely mounted memory.

[0073] The control unit 1000 may further include an interface 1020 for communicating with at least one external device. Thus, the interface 1020 may include analog and digital components and one or more transmitters and receivers having an appropriate number of wired or wireless communication ports.

[0074] The processing circuit 1010 controls the normal operation of the control unit 1000, for example, by transmitting data and control signals to the interface 1020 and the storage medium 1030, by receiving data and reports from the interface 1020, and by acquiring data and instructions from the storage medium 1030. Other components of the control node and related functions are omitted in order to avoid obscuring the concepts presented herein.

[0075] Figure 10 shows an example of a control unit 1000 for controlling at least one driven and / or braked wheel 102, 310 of a large vehicle 100. The control unit includes a processing circuit 1010 arranged to set a default reverse tire model and a boost reverse tire model, each reverse tire model representing the respective relationship between longitudinal wheel slip λ and longitudinal wheel force Fx in the wheel 102, 310, and the boost reverse tire model representing a higher maximum wheel slip value λ for the wheel 102, 310 compared to the default reverse tire model. lim The processing circuit also indicates the motion requirement a which represents the desired longitudinal force Fx generated by the wheels 102, 310. req Upon obtaining the boost signal, the boost reverse tire model is selected as the active reverse tire model in response to the boost signal detection; otherwise, the default reverse tire model is selected as the active reverse tire model, and the motion request a reqDepending on the active reverse tire model, it is configured to control at least one driven and / or braked wheel 102, 310.

[0076] Figure 11 shows a computer-readable medium 1110 carrying a computer program comprising program code means 1120 for performing the method shown in Figure 9 and the techniques described herein when the above program product is executed on a computer. The computer-readable medium and the code means together may form a computer program product 1100.

Claims

1. A computer implementation method for controlling at least one driven and / or braked wheel (102, 310) of a large vehicle (100), (S1) Setting a default reverse tire model and a boost reverse tire model, wherein each reverse tire model represents the respective relationship between longitudinal wheel slip (λ) and longitudinal wheel force (Fx) in the wheel (102, 310) and is associated with the respective wheel slip limit, and the boost reverse tire model is associated with a higher wheel slip limit (λlim, 230) of the wheel (102, 310) compared to the default reverse tire model. A motion request (a) indicating a desired value of the longitudinal wheel force (Fx) generated by the wheels (102, 310). ｒｅｑ ) to obtain (S2), In response to detecting a boost signal (550), the boost reverse tire model is selected as the active reverse tire model, and if no boost signal is detected, the default reverse tire model is selected as the active reverse tire model (S3), wherein the boost signal (S32) is set to be manually triggered by the operation of a trigger device in order to give a human driver more control authority than an automated driver. The aforementioned movement request (a ｒｅｑ (S4) controlling the at least one driven and / or braked wheel (102, 310) in accordance with and based on the active reverse tire model, wherein the active reverse tire model converts the motion request into a wheel slip request or a wheel speed request, Methods that include...

2. The method according to claim 1, comprising setting up a boosted inverted tire model having a peak longitudinal wheel force (240) corresponding to a higher wheel slip value compared to the peak longitudinal wheel force of the default inverted tire model (S11).

3. The method according to claim 1 or 2, comprising setting the boosted inverted tire model having smaller slip stiffness values ​​(260, 270) compared to the default inverted tire model (S12).

4. The motion request (a ｒｅｑ The method according to any one of claims 1 to 3, comprising obtaining (S21).

5. From the motion support device MSD coordination function (530) of the vehicle motion management VMM system included in the large vehicle (100), or from the autonomous or semi-autonomous driving function included in the large vehicle (100), the motion request (a ｒｅｑ The method according to any one of claims 1 to 4, comprising obtaining (S22).

6. The method according to any one of claims 1 to 5, wherein the boost signal (S31) is triggered when the accelerator pedal position or brake pedal position exceeds a predetermined threshold.

7. The method according to any one of claims 1 to 6, wherein the boost signal (S33) is provided on the condition that the large vehicle (100) is operating at a speed below an allowable threshold for vehicle speed.

8. The method according to any one of claims 1 to 7, wherein the boost signal (S34) is conditional on the large vehicle (100) operating with yaw motion below an allowable threshold for vehicle yaw motion.

9. The method according to any one of claims 1 to 8, comprising determining the lateral force requirement of at least the driven and / or braked wheel (102) (S35), wherein the boost signal is conditional on the lateral force requirement being below a lateral force requirement threshold.

10. The method according to any one of claims 1 to 9, comprising updating the default reverse tire model in response to detection of the boost signal (550) (S5).

11. A computer program that, when the program is executed on a computer, includes code means for the program to perform the steps described in any one of claims 1 to 10.

12. A control unit (300, 400, 500, 1000) for controlling at least one driven and / or braked wheel (102, 310) of a large vehicle (100), wherein the control unit comprises a processing circuit (1010), and the processing circuit is The method involves setting a default reverse tire model and a boost reverse tire model, wherein each reverse tire model represents the respective relationship between longitudinal wheel slip (λ) and longitudinal wheel force (Fx) in the wheel (102, 310) and is associated with the respective wheel slip limit, and the boost reverse tire model is associated with a higher wheel slip limit (λlim, 230) of the wheel (102, 310) compared to the default reverse tire model. A motion request (a) indicating a desired value of the longitudinal wheel force (Fx) generated by the wheels (102, 310). ｒｅｑ ) to obtain, In response to detecting a boost signal, the boost reverse tire model is selected as the active reverse tire model, and if no boost signal is detected, the default reverse tire model is selected as the active reverse tire model, wherein the boost signal (S32) is set to be manually triggered by the operation of a trigger device in order to give the human driver more control authority than the automated driver. Controlling the at least one driven and / or braked wheel (102, 310) based on the active reverse tire model in response to the motion request (areq), wherein the active reverse tire model converts the motion request into a wheel slip request or a wheel speed request. It is configured to do so. Control units (300, 400, 500, 1000).

13. A large vehicle (100) comprising the control unit described in claim 12.

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