Vehicle Motion Management Based on Torque Request with Speed Limit

Abstract

A vehicle motion management system (260) for a vehicle, the vehicle motion management system being capable of being connected to a motion support system (230230) for transmitting control signals between the vehicle motion management system and the motion support system, wherein the vehicle motion management system is configured to: - determine a desired torque for operating the vehicle in a current vehicle operating condition; - determine a wheel slip rate limit of at least one wheel of the vehicle; - determine a wheel speed limit of the at least one wheel of the vehicle based at least on the wheel slip rate limit; and - transmit a control signal indicating the desired torque and the wheel speed limit to the motion support system (230).

Description

Technical Field

[0001] The present disclosure relates to vehicle motion management for heavy vehicles, i.e., coordinated control of motion support devices such as service brakes and propulsion equipment.

[0002] The present invention can be applied to heavy vehicles such as trucks, buses, and construction machinery. Although the present invention will be described for freight transport vehicles (e.g., semi-trailers and trucks), the present invention is not limited to this particular type of vehicle, but can also be used in other types of vehicles such as cars. Background Art

[0003] Vehicles are becoming increasingly complex in terms of mechanics, pneumatics, hydraulics, electronics, and software. Modern heavy vehicles may include various different physical devices such as combustion engines, electric motors, friction brakes, regenerative brakes, shock absorbers, air bellows, and power steering pumps. These physical devices are commonly referred to as motion support devices (MSDs). MSDs can be individually controllable. For example, a friction brake (i.e., negative torque) can be applied at one wheel while another wheel on the vehicle (even possibly another wheel on the same axle) is simultaneously used to generate positive torque via an electric motor.

[0004] Recently proposed vehicle motion management (VMM) functions, e.g., executed on a central vehicle unit computer (VUC), rely on combinations of MSDs to operate the vehicle in order to obtain a desired motion effect while maintaining vehicle stability, cost efficiency, and safety. WO2019072379A1 discloses an example where wheel brakes are selectively used to assist in the turning operation of a heavy vehicle.

[0005] A common scheme for controlling various MSDs is to use torque control at the actuator level without any consideration of wheel slip. However, this scheme is not without performance limitations. For example, in the case of an excessive wheel slip condition (where one or more wheels slip in an uncontrolled manner), then safety functions such as traction control and anti-lock braking functions intervene and request torque override to bring the slip back under control. These safety functions are typically operated by separate control units. If the primary control of the actuator and the slip control function associated with the actuator are assigned to different control units, the latencies involved in their communication may limit the slip control performance. In addition, the relevant actuator and slip assumptions made in multiple control units for implementing slip control may be inconsistent, which may in turn lead to suboptimal performance.

[0006] There is a need for an improved vehicle control method that better handles wheel slip. Summary of the Invention

[0007] The object of the present disclosure is to provide a control unit and method that facilitate vehicle control based on a slip ratio request or a wheel speed request (instead of the conventional torque request), where the speed request or slip ratio request is obtained based on an improved tire behavior model.

[0008] According to a first aspect, there is provided a vehicle motion management system for a vehicle, the vehicle motion management system being capable of being connected to a motion support system for transmitting control signals between the vehicle motion management system and the motion support system, wherein the vehicle motion management system is configured to determine a desired torque for operating the vehicle in a current vehicle operating condition; determine a wheel slip ratio limit of at least one wheel of the vehicle; determine a wheel speed limit of the at least one wheel of the vehicle based at least on the wheel slip ratio limit; and transmit a control signal indicating the desired torque and the wheel speed limit to the motion support system.

[0009] The vehicle motion management system and the motion support system are control systems of the vehicle, wherein each of these control systems is arranged to perform various control functions for controlling the operation of the vehicle, in particular for controlling the operation of the wheels. According to an example, vehicle motion management is just normal driver control input, i.e., manual steering, acceleration, and braking inputs. The vehicle motion management system is preferably configured to receive and determine higher-level wheel parameters, i.e., the vehicle motion management system determines the desired torque and the wheel slip ratio limit in a more generalized form, while the motion support system is arranged as a lower-level control system that is configured to convert the parameters received from the vehicle motion management system into appropriate parameters for the actuator. Before forwarding the actuator signal to the actuator, the motion support system takes into account the current driveline state. For example, the current driveline state may relate to the current vehicle transmission state, the gear of the vehicle transmission, or the transmission clutch actuation state.

[0010] For example, the desired torque can be received from the vehicle operator depressing the accelerator pedal and / or depressing the brake pedal. The desired torque can also be received from a system that autonomously controls the vehicle propulsion operation or from an advanced driver assistance system (ADAS).

[0011] To ensure that excessive slip does not occur, in addition to the torque request, two speed limits: an upper speed limit and a lower speed limit, can also be sent to the motor controller. If the current motor speed is within the range defined by the upper and lower limits, the electric motor should apply torque according to the torque requested in the VMM torque request.

[0012] At a given time step, if the current motor speed is higher than the upper limit, the motor controller shall reduce the applied motor torque with respect to the previous time step. The motor torque shall continue to decrease until the motor speed is lower than or equal to the speed upper limit. Additionally, at a given time step, if the motor speed is measured to be lower than the speed lower limit, the torque applied to the motor shall increase with respect to the last time step. The motor torque shall continue to increase until the motor speed is higher than or equal to the speed lower limit.

[0013] Alternatively, the control can be based on reducing the magnitude of the applied torque without allowing the sign of the applied torque to change.

[0014] This "override" of torque control can be terminated if the motor speed returns to a value within the range defined by the speed upper and lower limits, or if the VMM torque request received by the motor control is less than the value output from the upper speed limiter. The "override" of torque control can also be terminated if the VMM torque request received by the motor control is greater than the value output from the lower speed limiter.

[0015] The speed upper and lower limits can be calculated based on the current vehicle speed and the longitudinal slip rate limit, which can be determined according to an inverse tire model, as will be discussed in more detail below. Thus, according to one example, the speed limits are similar to an allowable motor or wheel speed window centered around the current motor or wheel speed. This means that if a section with reduced friction is encountered, the motor speed may change rapidly, but without causing excessive wheel slip, because the speed limit will be exceeded and the torque will then be adjusted to keep the speed within the allowable range defined by the speed upper and lower limits.

[0016] Note that all the states and speed limits described above should have signs. For example, when "torque increases" due to the speed lower limit, this will cause a negative torque value to increase to a less negative torque value; or from a positive torque value to a more positive torque value; or even from a negative value to a positive value. Similar behavior can be implemented for the speed upper limit.

[0017] In addition to (or instead of) speed limits or wheel slip rate limits, rotational acceleration limits can be sent to the motor controller. These can help prevent the speed limiter or any other motor control function from transmitting an undesired torque step change to the wheel.

[0018] The wheel slip ratio limit should be interpreted as the maximum allowable wheel slip ratio of at least one wheel during operation. Wheel slip is the relative longitudinal movement between the vehicle's wheels and the ground, i.e., the amount of "skidding". Considering the wheel radius, the wheel slip ratio can be determined as the relationship between the wheel longitudinal speed and the wheel rotational speed. Thus, the wheel speed limit is based on the wheel speed relative to the road surface, as seen in a wheel-based coordinate system. According to an example embodiment, the vehicle motion management system can be configured to determine the current rotational wheel speed and the current longitudinal wheel speed of at least one wheel of the vehicle; and determine the wheel slip ratio of the at least one wheel based on the current rotational wheel speed and the current longitudinal wheel speed.

[0019] This disclosure is at least partially based on the recognition that by transmitting a control signal indicating the desired torque in combination with the wheel speed limit to the motion support system, the calculation of the wheel slip ratio limit can be performed by a higher-level vehicle motion management system. When calculating the wheel slip ratio, the denominator in the wheel slip ratio equation consists of the rotational wheel speed of the wheel. At low vehicle speeds, the denominator thus approaches zero or tends to zero, which can lead to a source of error when calculating the wheel slip ratio. Therefore, it is advantageous to perform the wheel slip ratio in a higher-level vehicle motion management system because potential inconsistencies when calculating the wheel slip ratio by a separate motion support system can be avoided. Thereby, improved wheel slip ratio consistency is achieved.

[0020] Furthermore, when operating the vehicle using an electric motor, it is particularly advantageous to transmit a control signal indicating the desired torque and the wheel speed limit to the motion support system because the electric motor can be speed and torque controlled. In contrast to slip control, speed control is also easier to implement for, e.g., service brakes because the rotational speed is a common output of the tire torque balancing system and does not include any non-linearity present in the wheel slip ratio equation.

[0021] According to an example embodiment, the wheel speed limit can be further based on the desired torque. Thus, the desired torque (i.e., the torque request) is used to calculate the slip ratio limit, which is the slip ratio limit used when calculating the wheel speed limit.

[0022] According to an example embodiment, the wheel speed limit can include a wheel speed upper limit and a wheel speed lower limit. The vehicle motion management system can be further configured to transmit the wheel speed upper limit to the motion support system at least when the desired torque is higher than zero; and transmit the wheel speed lower limit to the motion support system at least when the desired torque is lower than zero.

[0023] An advantage is that different wheel speed limits can be used according to vehicle acceleration or vehicle deceleration.

[0024] According to an example embodiment, the vehicle motion management system may be further configured to: determine an offset wheel speed parameter; obtain a signal indicative of the wheel speed of the vehicle; and determine a wheel slip ratio limit based on the offset wheel speed parameter when the wheel speed is below a threshold vehicle speed limit.

[0025] The offset wheel speed parameter is advantageously used when the wheel speed is relatively low, e.g., close to zero. As described above, due to the denominator of the wheel slip ratio calculation model, it may be difficult to correctly calculate the wheel slip ratio limit at low speeds. Therefore, setting the offset wheel speed parameter advantageously remedies this potential inconsistency. The offset wheel speed parameter may be an upper offset wheel speed parameter and a lower offset wheel speed parameter, wherein the upper offset wheel speed parameter is higher than the current vehicle speed and the lower offset wheel speed parameter is lower than the current vehicle speed. The offset wheel speed parameter may be obtained by mapping the offset wheel speed parameter to a desired torque using a tire model.

[0026] According to an example embodiment, the wheel slip ratio limit may be within a predetermined wheel slip ratio range. Thus, the wheels of the vehicle will not be exposed to too severe a wheel slip or too low a wheel slip ratio.

[0027] According to an example embodiment, the vehicle motion management system may be further configured to obtain a signal indicative of the current accelerator pedal position of the accelerator pedal of the vehicle; and determine a desired torque based on the current accelerator pedal position. However, according to an example embodiment, the desired torque may alternatively be determined based on a signal received from an autonomous vehicle operating system. According to another alternative as shown above, the vehicle motion management system may also be configured to obtain a signal indicative of the brake pedal position for determining the desired torque, or obtain a signal from a so-called retarder lever position of a retarder of the vehicle. Thus, the vehicle motion management system may be arranged in an autonomously controlled vehicle as well as a driver-controlled vehicle.

[0028] According to an example embodiment, the vehicle motion management system may be further configured to determine a wheel friction level between at least one wheel and the road surface; and determine a current vehicle operating condition based on the determined wheel friction level. There are also other alternative ways to determine the current vehicle operating condition. For example, when determining the current vehicle operating condition, the current weight of the vehicle (i.e., the weight of a fully loaded vehicle), the road topology on which the vehicle is currently operating, etc. may also be used as input parameters alternatively or in combination with the wheel friction level.

[0029] According to a second aspect, there is provided a motion support system for a vehicle, the motion support system being connectable to the above-mentioned vehicle motion management system and at least one actuator, the at least one actuator being configured to apply a torque to at least one wheel of the vehicle, wherein the motion support system is configured to receive a control signal from the vehicle motion management system, the control signal indicating a desired torque for operating the vehicle in a current vehicle operating condition and indicating a wheel speed limit of the at least one wheel of the vehicle; determine a current vehicle driveline state of the vehicle; determine an operating torque and an actuator rotation speed limit based on the current vehicle driveline state, the desired torque, and the wheel speed limit; and transmit an actuator signal to the actuator to cause the actuator to generate the operating torque on the at least one wheel without exceeding the actuator rotation speed limit.

[0030] The current driveline state should be interpreted as the current operating mode of the driveline, particularly the transmission of the driveline. According to an example embodiment, the current vehicle driveline state may be one of the following: the current vehicle transmission state, the gear of the vehicle transmission, or the transmission clutch actuation state. Thus, as shown above, the motion support system is arranged as a lower-level control system that is configured to transform the parameters received from the vehicle motion management system into appropriate parameters for the actuator while taking into account the current driveline state.

[0031] According to an example embodiment, the wheel motion system may be a decentralized wheel motion system connectable to a wheel-specific actuator, the wheel-specific actuator being configured to control a single wheel of the vehicle.

[0032] Using a decentralized wheel motion system enables a rapid response to the specific actuator to which it is connected, thereby improving the running propulsion / braking performance of the vehicle. The decentralized wheel motion system may be connected to a separate vehicle motion management system or to a central vehicle motion management system that is connected to a plurality of decentralized wheel motion systems.

[0033] Other effects and features of the second aspect are largely similar to those described above with respect to the first aspect. Thus, through the above first and second aspects, there is provided a vehicle control system that includes a vehicle motion management system defined by any one of the embodiments of the first aspect and a motion control system defined by any one of the embodiments of the second aspect.

[0034] According to a third aspect, there is provided a method for controlling an actuator of a vehicle, the actuator being configured to apply a torque to at least one wheel of the vehicle, wherein the method includes: determining a desired torque for operating the vehicle in a current vehicle operating condition; determining a wheel slip rate limit of the at least one wheel of the vehicle; determining a wheel speed limit of the at least one wheel of the vehicle based at least on the wheel slip rate limit; determining an operating torque and an actuator rotational speed limit based on the desired torque, the wheel speed limit, and a current vehicle driveline state; and controlling the actuator to generate an operating torque on the at least one wheel without exceeding the actuator rotational speed limit.

[0035] The effects and features of the third aspect are largely similar to those described above with respect to the first aspect and / or the second aspect. Accordingly, the features described above with respect to the vehicle motion management system and the motion support system apply to the method described in the third aspect.

[0036] According to a fourth aspect, there is provided a control signal representing an instruction to be executed by a motion support system, the control signal including: a torque component that enables the motion support system to determine an operating torque; and a wheel speed limit component representing wheel speed limit data that, when executed by the motion support system, causes the motion support system to generate an actuator signal corresponding to an operating torque that is subject to an actuator rotational speed limit, the actuator rotational speed limit being determinable based on the wheel speed limit component in consideration of a current vehicle driveline state.

[0037] According to a fifth aspect, there is provided a computer program including program code components for performing the steps of the third aspect described above when the program is run on a computer.

[0038] According to a sixth aspect, there is provided a computer-readable medium carrying a computer program, the computer program including program components for performing the steps of the third aspect described above when the program components are run on a computer.

[0039] According to an example of the method, a VMM (Vehicle Motion Management) sends a torque request to an electric motor, and the torque request may (for example) represent a torque request from a driver's accelerator pedal (a positive torque request), or it may be a request representing a braking torque request (a negative torque request).

[0040] This object is also achieved, at least in part, by a control unit for controlling a heavy vehicle. The control unit is arranged to obtain input data indicative of a desired wheel force to be generated by at least one wheel of the vehicle and to convert the input data into a corresponding equivalent wheel speed (or equivalently, motor speed) or wheel slip ratio to be maintained by the wheel, in order to generate the desired wheel force based on an inverse tire model of the wheel. The control unit is arranged to obtain the inverse tire model according to the current operating condition of the wheel and to control the heavy vehicle based on the equivalent wheel speed or the wheel slip ratio.

[0041] Thus, instead of requesting torque from different actuators as is usually the case, a wheel slip ratio limit request is sent to the wheel torque actuators at the wheel ends, and then the task of these wheel torque actuators at the wheel ends is to maintain the operation below the requested wheel slip ratio limit. In this way, the control of the MSD is moved closer to the wheel ends, and higher bandwidth control is possible due to reduced control loop latency and faster processing available closer to the wheel ends. Therefore, the MSD can respond faster to changes in, for example, road friction and thus provide more stable wheel forces under variable operating conditions. Compared to traditional torque-based control, this MSD control scheme improves both the startability of the heavy vehicle and the maneuverability in higher speed driving scenarios. For example, if a wheel temporarily leaves the ground or experiences a significantly reduced vertical force due to a road bump, the wheel will not spin out of control. Instead, the MSD control will quickly reduce the applied torque to maintain the wheel slip ratio at the requested value (i.e., below the slip ratio limit), so that when the wheel contacts the ground again, an appropriate wheel speed will be maintained.

[0042] Another advantage is to adjust the inverse tire model to account for changes in the current operating condition of the wheel, as this improves the accuracy and robustness of the mapping between the desired wheel force and the equivalent wheel speed or wheel slip ratio. In this way, when the operating condition changes, the inverse tire model will be adjusted to better model the current operating condition. Therefore, when the operating condition of a given wheel changes, the mapping between the wheel force and the wheel slip ratio (or wheel speed) also changes to compensate for the change in the operating condition.

[0043] In addition to the wheel slip ratio or wheel speed, the control unit can also be arranged to allocate (i.e., request) a steering angle to be maintained on one or more steering wheels of the vehicle. This steering angle will have an impact on the lateral slip of the wheel. Therefore, jointly processing steering and wheel torque (slip ratio or speed) is generally an advantage, as this typically improves the overall vehicle control in terms of robustness and efficiency.

[0044] According to some aspects, the data indicating the desired wheel forces includes the desired wheel torque and the wheel rolling radius. This means that the inverse tire model interface can accommodate the function of outputting the requested torque, such as a conventional vehicle control function, which, together with the wheel radius, represents or indicates the desired wheel forces.

[0045] According to some aspects, the current operating conditions include the vehicle or wheel ground speed vector. Knowing the wheel ground speed allows the rotational speed of the wheel to be controlled to maintain the wheel slip ratio at a desired level. The wheel ground speed also affects the mapping between the wheel force and the wheel slip ratio. For example, the contact surface between the ground and the wheel may change with the vehicle speed.

[0046] According to some aspects, the current operating conditions include the normal load on the wheel or the vertical force acting on the wheel. The normal load on the wheel, together with the coefficient of friction, determines the maximum achievable wheel force. Therefore, it is preferable to adjust the inverse tire model to account for changes in the normal load. By measuring or otherwise determining the normal load, the inverse tire model can be made more accurate.

[0047] According to some aspects, the current operating conditions include the estimated or otherwise determined tire stiffness of the wheel. The tire stiffness has a greater impact on the inverse tire model in the linear range of low to medium tire slip. By considering changes in the tire stiffness, a more accurate inverse tire model can be obtained. Optionally, the tire stiffness is corrected for factors related to the tire on a given wheel, such as wear, age, temperature, inflation pressure, etc. The tire stiffness can be just the longitudinal slip stiffness that can be used as a basis for proportionally adjusting the lateral slip stiffness, or it can be a vector including both the longitudinal slip stiffness and the lateral slip stiffness.

[0048] According to some aspects, the current operating conditions include the tire-road friction coefficient associated with the wheel. Among other factors, the tire-road friction coefficient also affects the mapping between the wheel force and the wheel slip ratio because it affects the maximum achievable tire force. The estimated road friction parameter can be used to adjust the tire force curve to limit the allowed peak force and can also change the peak force slip ratio position of the inverse tire model.

[0049] According to some aspects, the current operating conditions include the minimum required lateral force of the wheel. This means that operation may be required with the minimum lateral force generating capacity of a given wheel. For example, if the vehicle is turning, in order to successfully complete the turn, a certain amount of lateral force may be required. Due to the requirement for lateral force, it may be necessary to limit the wheel speed to a wheel slip ratio lower than the requested wheel slip ratio. Similarly, the current operating conditions optionally include the maximum allowable lateral slip angle of the wheel. In the case of the minimum required lateral force and the maximum allowable lateral slip angle, the generated longitudinal slip request is limited to a certain search space, in which the maximum allowable lateral slip angle is used to ensure the minimum lateral force capacity. Although both are optional arguments, they can be advantageously used to request longitudinal force in a safe manner that does not cause problems such as yaw instability. The vehicle controller can use the minimum required lateral force parameter to ensure that there is still sufficient lateral force capacity to be able to pass through a given path with a specific acceleration profile and curvature profile. The maximum longitudinal speed of the vehicle during the entire maneuver is typically limited by roll stability and road friction. In order to know how much lateral acceleration a vehicle unit passing through a turning maneuver can support, it may be necessary to know the lateral force capacity. Therefore, being able to specify the minimum required lateral force capacity is an advantage.

[0050] The vehicle controller can use the maximum allowable lateral slip angle to ensure that the yaw moment balance or the sideslip of the vehicle is maintained at an acceptable level consistent with the maneuver to be performed. This feature is particularly beneficial in critical applications of autonomy or functional safety, in which it is desired to keep the tire operating within its linear combined slip ratio range to prevent any traction control or yaw stability intervention that may cause unpredictable effects.

[0051] According to some aspects, the inverse tire model is configured to provide the remaining lateral force capacity of the wheel. The remaining lateral force capacity can be used to adjust the boundaries of the request sent to the wheel end, or as feedback to the control distributor to adapt its control request to increase the lateral force capacity of the wheel (if the lateral force capacity of the wheel is too low for the current driving scenario).

[0052] According to some aspects, the inverse tire model is configured to provide the desired wheel force gradient for the tire operating point associated with the desired wheel force and the current operating conditions of the wheel. This output can be used, for example, to custom tune the gain of the speed controller in the actuator according to the priority of the control distributor. For example, if the vehicle is turning and the lateral gradient value is high, this indicates that poor speed control performance will reduce the lateral turning performance, so the gain of the speed controller can be adjusted to alleviate this problem. Knowing the gradient also helps to perform stability and control robustness analysis, which is an advantage.

[0053] According to some aspects, the control unit is arranged to store a predetermined inverse tyre model in a memory, wherein the inverse tyre model is stored in the memory as a function of the current operating condition of the wheel. This means that the control unit can access a range of different models and it can select a suitable model from this range of models.

[0054] According to some aspects, the control unit is arranged to: in response to the control of a heavy vehicle based on the equivalent wheel speed or the wheel slip ratio, adapt the inverse tyre model based on the measured wheel behaviour and / or vehicle behaviour. Thus, advantageously, the control unit monitors the actual response of the wheel (and possibly also the actual response of the vehicle) and adjusts the inverse tyre model accordingly. This means that the control method becomes less sensitive to assumptions about vehicle performance in different scenarios or the influence of different parameters on vehicle controllability. Furthermore, if the operating condition changes in an unexpected way, the inverse tyre model will adapt to this change, thus providing robust control also in scenarios not yet encountered.

[0055] According to some aspects, the inverse tyre model is adjusted, as a function of the wheel slip ratio or the wheel speed, to always lie within a predetermined upper and / or lower limit of the wheel force. This means that model adjustment of the inverse tyre model is allowed, but only within certain predetermined boundaries. Thus, one or more boundaries represent a safety precaution against unforeseen errors during the model adaptation process. An example of an adaptive inverse tyre model is an artificial neural network which is continuously or at least regularly trained based on the control input and the actual wheel response or the vehicle's response to the control input.

[0056] Also disclosed herein are a computer program, a computer-readable medium, a computer program product and a vehicle associated with the advantages discussed above.

[0057] In general, all terms used in the claims should be interpreted according to their ordinary meaning in the technical field, unless otherwise clearly defined herein. References to "an / the element, apparatus, component, device, step etc." should be construed openly as referring to at least one instance of the element, apparatus, component, device, step etc., unless otherwise clearly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed, unless clearly stated. Further features and advantages of the present invention will become apparent when studying the appended claims and the following description. Those skilled in the art will recognize that, without departing from the scope of the present invention, different features of the present invention can be combined to yield embodiments other than those described hereinafter.

[0058] It should also be understood that, even though some features are discussed separately from other features, all features discussed herein can be advantageously implemented and used to control the same vehicle. Accordingly, the various features, algorithms, and devices disclosed herein should be considered in combination as well as separately from one another. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] With reference to the accompanying drawings, a more detailed description of embodiments of the invention, cited by way of example, follows.

[0060] In these figures:

[0061] Figure 1 An example heavy vehicle is shown;

[0062] Figure 2 The arrangement of the motion support device is schematically shown;

[0063] Figure 3 The vehicle control function is shown;

[0064] Figure 4 Is a graph showing tire force as a function of wheel slip ratio;

[0065] Figure 5 The adaptation of the wheel behavior model to measured data is shown;

[0066] Figure 6 An example motion support device control system is shown;

[0067] Figure 7 Is a flowchart showing a method;

[0068] Figure 8 The control unit is schematically shown;

[0069] Figure 9 An example computer program product is shown;

[0070] Figure 10 A road scenario with a large difference in friction between the left and right wheels (split friction) is shown;

[0071] Figures 11 to 14 Is a flowchart showing a method;

[0072] Figure 15 A tire is shown; and

[0073] Figures 16 to 18 Is a flowchart showing a method. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0074] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain aspects of the invention are shown. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. Throughout the specification, like reference numerals refer to like elements.

[0075] It should be understood that the present invention is not limited to the embodiments described and shown in the drawings; rather, those skilled in the art will recognize that many modifications and variations can be made within the scope of the appended claims.

[0076] Figure 1 An example vehicle 100 for goods transportation is shown, in which the techniques disclosed herein can be advantageously applied. The vehicle 100 includes a tractor or towing vehicle 110 supported on front wheels 150 and rear wheels 160, at least some of the front wheels 150 and rear wheels 160 being drive wheels. Typically (but not necessarily), all wheels on the tractor are braking wheels. The tractor 110 is configured to tow in a known manner a first trailer unit 120 supported on trailer wheels 170 via a fifth-wheel coupling. Trailer wheels are typically braking wheels, but may also include drive wheels on one or more axles.

[0077] It can be understood that the methods and control units disclosed herein can also be advantageously applied to other types of heavy vehicles, such as trucks with drawbar couplings, construction equipment, buses, etc. The present disclosure presents various complementary techniques, methods, and control units for controlling heavy vehicles at least partially based on the relationship between wheel forces and wheel slip ratios, as recited in the appended list of claims.

[0078] The tractor 110 includes a vehicle unit computer (VUC) or control unit 130 for controlling various functions, namely, for implementing propulsion, braking, and steering. Some trailer units 120 also include a VUC or control unit 140 for controlling various functions of the trailer, such as braking of the trailer wheels and sometimes also propulsion of the trailer wheels. The VUCs 130, 140 can be centralized or distributed over several processing circuits. A part of these vehicle control functions can also be executed remotely, for example, on a remote server 190 connected to the vehicle 100 via a wireless link 180 and a wireless access network 185.

[0079] The VUC 130 on the tractor 110 (and possibly the VUC 140 on the trailer 120) can be configured to perform a vehicle control method organized according to a hierarchical functional architecture, where some functions can be included in the traffic situation management (TSM) domain at a higher layer, while some other functions can be included in the vehicle motion management (VMM) domain at a lower functional layer.

[0080] Figure 2 Function 200 for controlling the wheel 210 is schematically shown by way of some exemplary MSDs or actuators, where the some exemplary MSDs or actuators include a friction brake 220 (such as a disc brake or a drum brake) and a propulsion device 250. The friction brake 220 and the propulsion device are examples of wheel torque generating devices, which may also be referred to as actuators and can be controlled by one or more motion support device control units 230. This control is based on measurement data obtained, for example, from a wheel speed sensor 240 and from other vehicle state sensors 280 (such as radar sensors, lidar sensors, and vision-based sensors such as camera sensors and infrared detectors). Other exemplary torque generating motion support devices that can be controlled according to the principles discussed herein include engine retarders and power steering devices. The MSD control unit 230 can be arranged to control one or more actuators. For example, it is not uncommon for the MSD control unit 230 to be arranged to control two wheels on an axle.

[0081] Here, the terms "MSD controller", "MSD control function", "motion support system", "actuator control system", and "wheel motion system" can be used interchangeably with the term "MSD control unit".

[0082] The TSM function 270 plans driving operations over a time span of, for example, about 10 seconds. This time range corresponds to, for example, the time required for the vehicle 100 to pass through a curve. The vehicle maneuvers planned and executed by the TSM can be associated with the desired vehicle speed and the acceleration profiles and curvature profiles describing a given maneuver. The TSM continuously requests the desired acceleration profile a req and curvature profile c req from the VMM function 260, and the VMM function 260 performs force distribution in order to meet the requests from the TSM in a safe and robust manner. The VMM function 260 continuously feeds back capability information to the TSM function, which details the current capabilities of the vehicle in terms of, for example, force, maximum speed, and achievable acceleration.

[0083] Acceleration profiles and curvature profiles can also be obtained from the driver of a heavy vehicle via normal control input devices such as the steering wheel, accelerator pedal, and brake pedal. The sources of the acceleration profiles and curvature profiles are not within the scope of this disclosure and will not be discussed in more detail herein. The advanced VMM function can be combined with traditional manual driver control inputs to form an advanced driver assistance system (ADAS).

[0084] Also referring to Figure 3 which shows the vehicle control function 300, the VMM function 260 operates over a time span of about 1 second and continuously transforms the acceleration profile a req and the curvature profile c req into control commands for controlling vehicle motion functions actuated by different MSDs 220, 250 of the vehicle 100, which report capability information 321a - 321c to the VMM, and these capability information 321a - 321c are in turn used as constraints in vehicle control. The VMM function 260 performs vehicle state or motion estimation 305, i.e., by using various sensors 306 typically (but not always) connected to the MSDs 220, 250 arranged on the vehicle 100 to monitor the operation, the VMM function 260 continuously determines the vehicle state s including the positions, velocities, accelerations, and articulation angles of different units in the vehicle combination.

[0085] The result of the motion estimation 305 (i.e., the estimated vehicle state s) is input to the force generation module 310, which determines the global forces V = [V1, V2] required for different vehicle units to move the vehicle 100 according to the requested acceleration profile a req and curvature profile c req The required global force vector V is input to the MSD coordination function 320, which distributes wheel forces and coordinates other MSDs (such as steering and suspension). Then, the coordinated MSDs together provide the desired lateral force Fy and longitudinal force Fx and the required moment Mz on the vehicle units to obtain the desired motion of the vehicle combination 100.

[0086] The vehicle unit motion is determined by using, for example, a global positioning system, vision - based sensors, wheel speed sensors, radar sensors, and / or lidar sensors and converting the vehicle unit motion into a local coordinate system of a given wheel 210 (e.g., in terms of longitudinal and lateral velocity components). By comparing the vehicle unit motion in the wheel reference coordinate system with the data obtained from the wheel speed sensor 240 (which is arranged to be connected to the wheel 210), the wheel slip rate can be accurately estimated in real - time.

[0087] The tire model, which will be discussed in more detail below in conjunction with Figure 4 Figure 4 can be used to convert between a desired longitudinal tire force Fx for a given wheel i i and the equivalent wheel slip ratio λ of that wheel i The wheel slip ratio λ involves the difference between the wheel rotational speed and the ground speed and will be discussed in more detail below. The wheel speed ω is the rotational speed of the wheel and is given in units of angular velocity expressed, for example, in revolutions per minute (rpm) or in radians per second (rad / s) or degrees per second (deg / s).

[0088] Here, the tire model is a wheel behavior model that describes the wheel forces generated as a function of the wheel slip ratio in the longitudinal direction (rolling direction) and / or the lateral direction (orthogonal to the longitudinal direction). In "Tyre and vehicle dynamics" (Elsevier Publishing Company, 2012, ISBN 978 - 0 - 08 - 097016 - 5), Hans Pacejka presents the basics of the tire model. See, for example, Chapter 7, which discusses the relationship between the wheel slip ratio and the longitudinal force.

[0089] In summary, the VMM function 260 manages the force generation and the MSD coordination, i.e., it determines what forces are required at the vehicle unit to meet the requests from the TSM function 270, such as accelerating the vehicle according to the requested acceleration profile requested by the TSM and / or also generating a certain curvature motion of the vehicle requested by the TSM. These forces can include, for example, the yaw moment Mz, the longitudinal force Fx, and the lateral force Fy, as well as different types of torques that will be applied to different wheels.

[0090] The interface 265 between the VMM and the MSD that can transfer torque to the vehicle wheels has traditionally focused on torque - based requests from the VMM to each MSD without any consideration of the wheel slip ratio. However, this scheme has significant performance limitations. If a safety - critical situation or an excessive slip situation occurs, the relevant safety functions (traction control, anti - lock braking, etc.) running on separate control units usually intervene and request torque override to bring the slip back under control. The problem with this scheme is that since the main control of the actuator and the slip control of the actuator are assigned to different electronic control units (ECUs), the time delay involved in their communication significantly limits the slip control performance. In addition, the relevant actuators and slip assumptions in the two ECUs used to implement the actual slip control may not be consistent, which may in turn lead to sub - optimal performance.

[0091] Conversely, significant benefits can be achieved by using requests based on wheel speed or wheel slip ratio at interface 265 between one or more VMMs and MSD controller 230, thereby shifting the difficult actuator speed control loop to the MSD controller, which typically operates with a shorter sampling time compared to the sampling time of the VMM function. Compared with the torque-based control interface, such an architecture can provide better immunity to interference, thereby improving the predictability of the forces generated at the tire-road contact surface.

[0092] Reference Figure 3 , the inverse tire model functional block 330 converts the required wheel forces Fx i , Fy i determined by the MSD coordination functional block 320 for each wheel or subset of wheels into an equivalent wheel speed ω wi or wheel slip ratio λ i . These wheel speeds or wheel slip ratios are then sent to the corresponding MSD controller 230. The MSD controller reports back capabilities 231a - 231c, which can be used as constraints, for example, in the MSD coordination functional block 320.

[0093] According to SAE J670 (SAE Vehicle Dynamics Standards Committee, January 24, 2008), the longitudinal wheel slip ratio λ can be defined as:

[0094]

[0095] where R is the effective wheel radius in meters, ω x is the angular velocity of the wheel, and v x is the longitudinal speed of the wheel (in the coordinate system of the wheel). Thus, λ ranges between - 1 and 1 and quantifies the degree to which the wheel slips relative to the road surface. The wheel slip ratio is essentially the speed difference between the wheel and the vehicle. Therefore, the techniques disclosed herein are applicable to any type of wheel slip ratio definition. It can also be understood that in the coordinate system of the wheel, the wheel slip ratio value is equivalent to the wheel speed value of the speed of a given wheel on the surface.

[0096] The VMM 260 (optionally also the MSD control unit 230) maintains information about v x (in the reference frame of the wheel), while wheel speed sensors 240, etc., can be used to determine ω x (the rotational speed of the wheel).

[0097] To generate wheel forces in the wheel (or tire), slip must occur. For small slip ratio values, the relationship between the slip ratio and the generated force is approximately linear, where the proportionality constant is typically expressed as the slip stiffness of the tire. The tire 210 is subjected to a longitudinal force Fx , the lateral force F y and the normal force F z . The normal force F Z is the key to determining some important vehicle properties. For example, the normal force largely determines the achievable longitudinal tire force F x of the wheel, because: under normal circumstances, F x ≤μF z , where μ is the friction coefficient associated with the road friction conditions. The maximum available lateral force for a given longitudinal slip ratio can be described by the so-called Magic Formula, as described by Hans Pacejka in "Tyre and Vehicle Dynamics" (published by Elsevier, 2012, ISBN 978-0-08-097016-5).

[0098] Instead of directly requesting the wheel slip ratio or wheel speed from the MSD, a torque request with a speed limit interface can be used. Then, as long as the wheel speed remains between the high wheel speed limit and the low wheel speed limit, the torque request is allowed to affect the wheel behavior. The wheel slip ratio or wheel speed limit can be configured based on the above-mentioned desired wheel slip ratio to obtain a given force, or can be configured with a certain margin from the desired wheel slip ratio or wheel speed.

[0099] To ensure that excessive slip does not occur, in addition to the torque request, two speed limits: a speed upper limit and a speed lower limit can be sent to the motor controller. Some example embodiments may only use the speed upper limit. From a functional perspective, the limit of the wheel speed can be considered equivalent to the limit of the motor speed. Similarly, in the reference frame of a given wheel, given the current vehicle ground speed, the limit of the wheel speed or motor speed can be converted into the limit of the wheel slip ratio.

[0100] If the current motor speed is within the range defined by the upper and lower limits, the electric motor should apply torque according to the torque requested in the VMM torque request. It is realized that the wheel speed and the motor speed are closely related. If the motor is connected to one or more wheels via a transmission, the transmission determines the conversion between the motor speed and the wheel speed. If the wheels are connected to the motor via a differential, the torque and the wheel speed are distributed on the wheels in a known manner.

[0101] At a given time step, if the current motor speed is higher than the speed upper limit, the motor controller operates to decrease the applied motor torque relative to the previous time step. This causes the wheel speed to decrease and eventually fall below the configured wheel speed limit. The motor torque should continue to decrease until the motor speed is lower than or equal to the speed upper limit. Additionally, at a given time step, if the motor speed is measured to be lower than the speed lower limit, the torque applied to the motor should increase relative to the last time step. This causes the wheel speed to increase. The motor torque should continue to increase until the motor speed is higher than or equal to the speed lower limit. Other ways to implement the actual control could be to use a variable step size for torque control or to switch to wheel speed control if the wheel speed or wheel slip ratio exceeds the configured limits.

[0102] The method disclosed herein need not be implemented by performing control in discrete time steps. Thus, alternatively, if the current motor speed (or wheel speed) is detected to be higher than the configured upper limit, the motor controller continuously decreases the applied motor torque in a controlled manner while observing the motor speed and / or wheel speed. The motor torque should continue to decrease until the motor or wheel speed is lower than or equal to the speed upper limit. Additionally, if the motor speed (or wheel speed) is detected to be measured lower than the speed lower limit, the torque applied to the motor continuously increases. The motor torque should continue to increase until the motor speed is higher than or equal to the speed lower limit.

[0103] Alternatively, the control can be based on reducing the magnitude of the applied torque without allowing the sign of the applied torque to change.

[0104] This "override" of torque control can be terminated if the motor speed returns to a value within the range defined by the speed upper and lower limits, or if the VMM torque request received by the motor controller is less than the value output from the upper speed limiter. The "override" of torque control can also be terminated if the VMM torque request received by the motor controller is greater than the value output from the lower speed limiter.

[0105] The speed upper and lower limits can be calculated based on the current vehicle speed and the longitudinal slip ratio limit, which can be determined based on an inverse tire model, as will be discussed in more detail below.

[0106] Note that all the states and speed limits described above are signed values. Also note that, for example, when "torque increases" due to the speed lower limit, this will cause a negative torque value to increase to a less negative torque value; or increase from a positive torque value to a greater positive torque value; or even increase from a negative value to a positive value. Similar behavior can be implemented for the speed upper limit.

[0107] Instead of (or in addition to) speed limits or wheel slip rate limits, rotational acceleration limits can also be sent to the motor controller. These can help prevent the governor or any other motor control function from delivering an undesired torque step change to the wheels. Of course, wheel slip rate limits can also be used, as will be explained in more detail below.

[0108] The upper and lower speed limits can be calculated based on the current vehicle speed and a longitudinal slip rate limit, which can be determined based on an inverse tire model, as will be discussed in more detail below. Thus, according to one example, the speed limit is similar to an allowable motor or wheel speed window centered around the current motor or wheel speed. This means that if a section with reduced friction is encountered, the motor speed may change rapidly, but without causing excessive wheel slip, because the speed limit will be exceeded and the torque will then be adjusted to keep the speed within the allowable range defined by the upper and lower speed limits.

[0109] Note that all the states and speed limits described above should have positive and negative signs. For example, when "torque increases" due to the lower speed limit, this will cause a negative torque value to increase to a less negative torque value; or from a positive torque value to a more positive torque value; or even from a negative value to a positive value. A similar behavior can be implemented for the upper speed limit.

[0110] Figure 4 is a graph showing an example of achievable tire forces as a function of wheel slip rate. The longitudinal tire force Fx has a section 410 that exhibits an almost linear increase for small wheel slip rates, and then a section 420 with more non-linear behavior for larger wheel slip rates. Even at relatively small longitudinal wheel slip rates, the achievable lateral tire force Fy decreases rapidly. It is desirable to keep the vehicle operation within the linear region 410, where the achievable longitudinal force in response to an applied braking command is more predictable and, if needed, sufficient lateral tire force can also be generated. To ensure operation in this region, a wheel slip rate limit λ of, for example, about 0.1 can be applied to a given wheel. LIM For larger wheel slip rates (e.g., above 0.1), a more non-linear region 420 can be seen. Controlling the vehicle in this region can be difficult, so the increase is often avoided. Of particular interest is traction in off-road conditions etc. (where larger slip rate limits for traction control may be preferred), rather than for on-road operation.

[0111] This type of tire model can be used by the VMM 260 to generate the desired tire forces at a wheel. Instead of requesting the torque corresponding to the desired tire forces, the VMM can convert the desired tire forces into an equivalent wheel slip ratio (or equivalently, into the wheel speed relative to the ground speed) and request that slip ratio. The main advantage is that the MSD control device 230 will be able to maintain operation at the desired wheel slip ratio and transmit the requested torque at a much higher bandwidth by using the vehicle speed v x and the wheel rotational speed ω x to maintain operation at the desired wheel slip ratio and transmit the requested torque at a much higher bandwidth.

[0112] The control units 130, 140 can be arranged to store a predetermined inverse tire model f -1 (e.g., as a look-up table) in a memory. The inverse tire model is arranged to be stored in the memory as a function of the current operating conditions of the wheel 210. This means that the behavior of the inverse tire model is adjusted according to the operating conditions of the vehicle, which means that a more accurate model is obtained compared to a model that does not take into account the operating conditions. The model stored in the memory can be determined based on experiments and tests, or based on analytical derivations, or based on a combination of both. For example, the control unit can be configured to access a different set of models selected according to the current operating conditions. One inverse tire model can be customized for high-load driving with a large normal force, and another inverse tire model can be customized for slippery road conditions with low road friction, etc. The selection of the model to be used can be based on a set of predetermined selection rules. The model stored in the memory can also be at least partially a function of the operating conditions. Thus, the model can be configured to take, for example, the normal force or the road friction as input parameters to obtain the inverse tire model according to the current operating conditions of the wheel 210. It can be understood that many aspects of the operating conditions can be approximated by default operating condition parameters, while other aspects of the operating conditions can be roughly classified into a smaller number of categories. Thus, obtaining the inverse tire model according to the current operating conditions of the wheel 210 does not necessarily mean that a large number of different models need to be stored, or that complex analytical functions that can consider the changes in the operating conditions in fine granularity are required. Instead, it may be sufficient to select two or three different models according to the operating conditions. For example, one model can be used when the vehicle is heavily loaded, and another model can be used in other cases. In all cases, the mapping between the tire forces and the wheel slip ratio changes in some way according to the operating conditions, which improves the accuracy of the mapping.

[0113] The inverse tire model can also be implemented at least in part as an adaptive model that is 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 in terms of wheel forces generated by a given wheel in response to a given wheel slip rate request, and / or monitoring the response of the vehicle 100 in response to a wheel slip rate request. The adaptive model can then be adjusted to more accurately model the wheel forces obtained in response to a given wheel slip rate request for the wheel.

[0114] Figure 5 Graph 500 shows the inverse tire model that maps the longitudinal tire force Fx to the wheel slip rate. Also plotted are the measured values 510 of the pairs (F, λ) of wheel slip rate and the corresponding tire force F. According to some aspects, the control unit disclosed herein is arranged to: adapt the inverse tire model f based on the measured wheel behavior and / or vehicle behavior in response to the control of the heavy - duty vehicle 100 based on the equivalent wheel speed or wheel slip rate -1 One such type of measurement is the resistance encountered when the motor attempts to generate a specific wheel speed. This “torque state” output signal of the motor can be directly converted into an equivalent wheel force via the effective wheel radius R. Wheel force samples can also be obtained from the VMM function as part of the force distribution process. For example, if the VMM notices that too small a longitudinal force is always obtained in response to the wheel slip rate of a given request, the model can be adjusted to address the discrepancy, for example, by scaling it to better match the desired wheel force. In this case, note that the inverse tire model does not need to be correct in an absolute reference frame, i.e., the inverse tire model is able to accurately predict the force (in Newtons) generated for a given wheel slip rate. Instead, it is sufficient if the inverse tire model allows the VMM function 260 to successfully control the vehicle. Notably, by adjusting the inverse tire model in this way in response to a wheel slip rate request based on the measured wheel forces, other characteristics of the vehicle will automatically be included in the modeling to more accurately represent the mapping between wheel slip rate and wheel force.

[0115] In a first example of adapting the inverse tire model, pairs of samples (F, λ) of the generated force F and the current wheel slip rate λ are continuously obtained. The generated force F (longitudinal force Fx and lateral force Fy) and the yaw moment Mz can be determined based on vehicle behavior (i.e., relationships of the Newton's second - law type), where both the mass m and the acceleration a can be measured using basic sensor technology together with the current wheel slip rate.

[0116] Then the inverse tire model is continuously updated to fit the current measurements. For example, a Kalman filter can be applied to track the coefficients {c of the polynomial model i}, and this polynomial model can then be used as an inverse tire model. Polynomial fitting can also be performed to fit the measurement data 510 to the model, and then this model can be used as an inverse tire model.

[0117] In a second example, a neural network or other form of AI-based method is applied to continuously update the inverse tire model. For example, the network is trained using samples of the generated force F and the current wheel slip ratio λ, i.e., pairs (F,λ). The inputs to the network can be, for example, the vehicle load, tire specifications, and road conditions such as friction. The output can be a set of coefficients of a polynomial model that can be used as a representation of the inverse tire model.

[0118] It can be understood that this model adaptation does not need to be performed on the vehicle 100. Instead, the measurement data can be uploaded to a remote server 190, whose task is to find a suitable model for controlling the vehicle based on the wheel slip ratio rather than on torque requests. The model can then take into account measurement data from more than one vehicle (possibly from a group of the same type) or an operational design domain. The model or group of models can then be fed back from the remote server 190 to the vehicle for controlling the vehicle 100.

[0119] The entire inverse tire model can of course also be implemented as a neural network, which is trained during different types of operating conditions. Then, as the operating conditions of the heavy vehicle change, the inverse tire model also changes, such that the corresponding wheel slip ratio for a given wheel force changes over time, which is an advantage.

[0120] Inverse tire model f -1 It can also be adjusted according to the wheel slip ratio or wheel speed so that it always remains within a predetermined upper and lower limit of the wheel force. These limits can be obtained, for example, as statistical limits derived from the measurement data 510. For example, an upper limit 520 and a lower limit 530 can be set so as to confine the inverse tire model within one or two standard deviations from the mean, and so on.

[0121] A safety margin can also be applied to the adaptation itself, i.e., a constrained adaptation can be performed without allowing the inverse tire model to deviate outside a fenced region around a certain nominal model curve. This fenced region can be predetermined or adjusted according to the operating conditions, or by a predefined dynamic driving task (DDT) on a known operational design domain (ODD), which will reduce the amount of verification and validation required.

[0122] Referring again to Figure 2, the MSD control unit 230 may be configured to control one or more MSDs associated with the wheel 210. The one or more MSDs may include at least one service brake 220 and a propulsion unit 250. The at least one service brake 220 is arranged to generate negative torque through the wheel 210, and the propulsion unit 250 is arranged to generate positive torque and / or negative torque of the wheel 210, such as an electric motor and / or a combustion engine. Other torque generating devices that can be controlled by the MSD control unit include an engine retarder and a power steering device. The MSD control unit 230 is communicatively coupled to the VMM unit 260 to receive control commands including wheel speed and / or wheel slip rate requests from the VMM unit 260 to control vehicle movement through the one or more MSDs.

[0123] It can be understood that the MSD control unit discussed herein may also be configured to control one or more MSDs associated with other wheels than the wheel 210, such as for controlling the wheels of a given axle, or the MSDs of the wheels on one side of a trailer unit or all the wheels of a trailer unit. Figure 6 A system of MSD control units 230a - 230f is schematically shown, which is arranged to control the corresponding wheels 210a - 210f based on control signals received from the central VMM unit 260. One or more additional vehicle units may also be controlled in this way, and the one or more additional vehicle units are, for example, one or more trailers 120 that may be connected via a bogie unit. In this case, there may be more than one VMM function, and one VMM function may be designated as the master role, while other VMM functions may be configured to operate in the slave mode.

[0124] In summary, the VMM function 260 performs force distribution to meet a specific acceleration profile and / or curvature profile. The force is converted into an equivalent wheel slip rate (or wheel rotational speed), and this slip rate or speed (instead of the classical torque request) is sent to the MSD control unit 230. The conversion from the desired force to the equivalent slip rate or wheel rotational speed is based on the inverse tire model f -1 (). The inverse tire model is not only a function of the requested wheel torque or wheel force, but also takes into account the current operating scenario of the current operation of the vehicle 100. According to an example embodiment, the inverse tire model for controlling the vehicle 100 is given by the following formula:

[0125] [ω req , F y，rem , dF x / dω, dF y / dω] = f -1 (T req , v x, v y , F z，act , R w , C est , μ est , F y，min , α max )

[0126] Wherein

[0127] T req - Torque request at the wheel

[0128] v x - Longitudinal ground speed

[0129] v y - Lateral ground speed

[0130] F z，act - Normal load on the wheel

[0131] R w - Wheel rolling radius

[0132] C est - The estimated tire stiffness at the wheel (optionally, the lateral tire stiffness C est，y and the longitudinal tire stiffness C est , either one of them)

[0133] μ est - The estimated tire-road friction at the wheel

[0134] F y，min - Minimum required lateral force capacity

[0135] α max - Maximum allowable lateral slip ratio for achieving F y，min

[0136] ω req - Wheel rotational speed request, i.e., the target wheel speed to be controlled

[0137] F y，rem - Remaining lateral force capacity of a given wheel

[0138] dF x / dω - F x Gradient with respect to the wheel speed at the requested tire operating point

[0139] dF y / dω - F y Gradient with respect to the wheel speed at the requested tire operating point

[0140] Tire stiffness C est ​It can be the estimated tire stiffness, which can be corrected for factors such as tire wear, age, temperature, inflation pressure, etc. This can be just the longitudinal slip stiffness that can be used as a basis for scaling the given tire lateral slip stiffness, or it can be a vector including both the longitudinal slip stiffness and the lateral slip stiffness of the tire. The tire stiffness can have a significant impact on the force of the slip rate curve 400. In the absence of this argument, the nominal stiffness of the tire can be used in the tire model.

[0141] The estimated friction μ est can be used to adjust the tire force curve 400 to limit the allowed peak force, and to change the peak force slip rate position in the model. In the absence of this optional input, the nominal dry asphalt tire force curve can be used.

[0142] The minimum required lateral force capacity F y，min and the maximum allowed lateral slip angle limit α max are optional constraints of the tire model, which can communicate via an interface such as the interface 265 between the VMM function 260 and various MSD control units 230. With these additional inputs, the resulting longitudinal slip rate request is restricted in a vector space, in which the maximum lateral slip angle α max ensures the lateral force capacity F y，min . Both of these optional arguments can be used to request longitudinal force in a safe manner that does not cause significant yaw instability, etc. F y，min can be used to ensure that sufficient lateral force capacity is maintained so that it is possible to pass through a specific curve or complete some other maneuvers that require the generation of lateral force (i.e., F y ), while α max can be used to ensure that the yaw moment balance or the sideslip of the vehicle is maintained within a reasonable pre-configured or dynamically determined limit. This feature may be particularly beneficial in autonomous or functional safety-critical applications, in which it is desired to keep the tire operating within its linear combined slip rate range (e.g., Figure 3 the range 410 shown), thus preventing any traction control or yaw stability intervention.

[0143] On the output side, ω req is the wheel speed request, and this is the main request from the tire model. Given μ est and without violating F y，min and α max constraints, it should result in the required T req as long as it is possible to do so. It can be understood that the wheel speed request ω x can be continuously updated over time according to the ground speed v y ​req , so that it is equivalent to the wheel slip ratio, such as defined in the wheel slip ratio equation discussed above. Alternatively, the wheel slip ratio value λ can be transmitted req instead of the wheel speed value. Given the wheel speed relative to the ground, the wheel slip ratio and the wheel speed are equivalent amounts of information.

[0144] The remaining lateral force capacity F y，rem can be used to adjust the boundaries of the requests being sent, or as feedback to the control allocator to adapt its control requests to increase F y，rem , for example, if it is too close to zero.

[0145] Finally, dF x / dω and dF y / dω represent the gradients of the longitudinal and lateral forces with respect to the wheel rotational speed ω tgt at the requested operating point. For example, these parameters can be used to customize the gain of the speed controller in the actuator according to the priorities of the control allocator. For example, if the vehicle is turning and the dF y / dω value is high, it indicates that poor speed control performance will reduce the lateral turning performance, so the gain of the speed controller can be adjusted to prevent this.

[0146] Certain variants of the above function interface are of course possible. One possibility is to simply remove the rolling radius input and change the torque and rotational speed T req , R w to force and linear velocity respectively, then the inverse tire model becomes:

[0147] [ω req , F y，rem , dF x / dω, dF y / dω] = f -1 (F x，req , v x , v y , F z，act , C est , μ est , F y，min , α max )

[0148] Another alternative is to simply send all the tire parameters as a single structure argument with a predefined layout (e.g., p tyre ). Any value in the structure fields can be used to update the existing values, and default values can be used in place of non-existent fields.

[0149] Other options for the output of the inverse tire model can be to send the actual or maximum lateral tire force F y，maxor the currently utilized tire friction force capacity μ in the y direction y，util This gives rise to a model function according to the following formula

[0150] [ω req , F y，act , dF x / dω, dF y / dω] = f -1 (F x，req , v x , v y , F z，act , p tyre , F y，min , α max )

[0151] [ω req , F y，max , dF x / dω, dF y / dω] = f -1 (F x，req , v x , v y , F z，act , p tyre , F y，min , α max )

[0152] [ω req , μ y，util , dF x / dω, dF y / dω] = f -1 (F x，req , v x , v y , F z，act , p tyre , F y，min , α max )

[0153] As mentioned above, the inputs and outputs of many inverse tire models in the above examples are optional. For example, the default values of the parameters F z，act , R w , C est , μ est , F y，min , α max can be used in place of the actual measured values. It should also be understood that the outputs F y，act , dF x / dω, dF y / dω are not necessary for controlling the vehicle at an equivalent wheel speed or wheel slip rate corresponding to the desired wheel force.

[0154] It is also possible to add a steering angle request δ to the inverse tire model req , or a target steering angle value to be maintained. In this case, the input includes the required longitudinal wheel force F x，req and the lateral wheel force F y，req , and in addition to the wheel speed or wheel slip ratio, the output includes the target steering angle δ for a given wheel tgt , that is

[0155] [ω req , δ req , dF x / dω, dF y / dω] = f -1 (F x，req , F y，req , v x , v y , F z，act , p tyre , F y，min , α max )

[0156] It should also be understood that the wheel rotational speed ω req (i.e., the speed at which a given wheel 210 rotates) can be replaced by the wheel slip ratio λ. This is because: for a given wheel ground speed v x , the wheel speed request ω req and the wheel slip ratio request λ req are directly related via the wheel radius R. In other words, the wheel speed and the wheel slip ratio are often equivalent information quantities.

[0157] Summarizing the above discussion, this document discloses control units 130, 140 for controlling a heavy vehicle 100. The control unit is arranged to obtain input data indicating the desired wheel forces Fx, Fy to be generated by at least one wheel 210 of the vehicle 100, and to convert the input data into a corresponding equivalent wheel speed or wheel slip ratio to be maintained by the wheel 210, in order to generate the desired wheel forces Fx, Fy based on the inverse tire model f -1 of the wheel 210. The input data indicating the desired wheel forces to be generated can be obtained, for example, from a force distribution process in which the forces required to make the vehicle follow a desired acceleration profile and / or a desired curvature are determined. The acceleration profile and the curvature can be obtained from the manual control input of the driver of the vehicle 100 or from an autonomous or semi-autonomous control algorithm running on the VUC. The desired wheel forces can also be obtained at least in part via a wireless link from a remote server 190.

[0158] Data indicating the desired wheel forces Fx, Fy may include the desired wheel torque Treq and the wheel rolling radius R. By providing the torque and the radius, the equivalent desired wheel force can be determined, for example, as Fx = Treq * R.

[0159] The control units 130, 140 are arranged to obtain an inverse tire model based on the current operating conditions of the wheel 210 and are also arranged to control the heavy vehicle 100 based on the equivalent wheel speed or the wheel slip ratio. This means that the control units are configured to adapt the inverse tire model to the current operating conditions of the vehicle in some way. For example, if the vehicle is loaded with heavier goods, the inverse tire model used to control the vehicle will be adjusted to account for the change in the operating conditions. Various types of operating condition parameters can be considered, as discussed below. By obtaining an inverse tire model that depends on the current operating conditions, more accurate control can be achieved, and more robust control can also be achieved. Therefore, it can be understood that the inverse tire model considered here is a dynamic model, which, unlike a constant model, is adapted to fit the current operating conditions of the heavy vehicle. This improves vehicle performance and safety.

[0160] The current operating conditions may include the vehicle ground speed or the wheel ground speed vector having components v x 、v y The vehicle ground speed can be used to determine the wheel rotational speed corresponding to a given slip amount, for example, by calculating the normalized wheel slip difference discussed above. The performance of some tires also varies depending on whether the wheel is rotating slowly or quickly. Therefore, some inverse tire models may exhibit differences in the operating speed range from 0 km / h to 150 km / h of the ground speed. It can be understood that wheel control based on the requested wheel rotational speed requires a relatively fast interface between the VMM function 260 and the MSD control unit 230. This is because the wheel rotational speed required to obtain a given wheel slip ratio depends on the ground speed, which may change relatively quickly over time.

[0161] Optionally, the current operating conditions further include the normal load Fz or the vertical tire force associated with the wheel 210. The normal load may have a significant impact on the inverse tire model (i.e., the mapping between the desired wheel force and the wheel speed or the wheel slip ratio). For example, the maximum available longitudinal tire force Fx is limited by the normal force and the friction coefficient. Therefore, by parameterizing the inverse tire model based on the normal load Fz, a more accurate inverse tire model that more closely models the current operating conditions of the vehicle 100 can be obtained.

[0162] According to some other aspects, the current operating conditions include the estimated tire stiffness Cest of the wheel 210. If the tire stiffness is estimated explicitly, a more accurate inverse tire model can be obtained. For example, the tire stiffness can be estimated based on a feedback system, where measured values of tire forces are mapped to wheel slip rates, and a linear or semi-linear relationship can be determined. The tire stiffness can also be obtained, for example, from a database maintained in the remote server 190 or a memory connected to the VUC, and if the tire can be identified, it can be indexed. Identifying the tire attached to a given wheel can be done, for example, by embedding a radio frequency identification (RFID) device in the tire or by manual configuration.

[0163] The current operating conditions can also include the estimated tire-road friction coefficient μ of the wheel. This road friction force can be estimated in real time using known methods, such as the methods disclosed in US 9,475,500 B2, US 8,983,749 B1, or EP 1719676 B1. Then, the inverse tire model can be adjusted to match the current road friction force.

[0164] The current operating conditions can also include the minimum required lateral force capacity Fy,min and / or the maximum allowable lateral slip α of the wheel 210. The minimum lateral force capacity Fy,min and the maximum lateral slip angle limit α are optional constraints of the tire model. If these data are used as inputs to the inverse tire model function, these parameters can be used as constraints to determine the output. For example, it can be determined that the output wheel speed or wheel slip rate will not result in insufficient lateral force capacity or lateral slip, which is an advantage.

[0165] Conversely, the inverse tire model f -1 can also be configured to provide the remaining lateral force capacity Fy,rem of the wheel 210. The remaining lateral force capacity Fy,rem can be used to adjust the boundaries of the requests being sent or as feedback to the control dispenser to adapt its control requests, so as to increase the remaining lateral force capacity when the remaining lateral force capacity becomes too low.

[0166] The inverse tire model f -1 can also be configured to provide the gradients dFx, dFy of the desired wheel forces with respect to the wheel speed or wheel slip rate, which are the wheel speed or wheel slip rate at the tire operating point associated with the desired tire forces and under the current operating conditions of the wheel 210. If the input parameters change slightly, this gradient provides information about the model behavior and can be advantageously used to adjust, for example, the control algorithms in the MSD control unit 230. For example, these gradients can be used to adjust the gains of control functions such as PID controllers.

[0167] Figure 7is a flowchart showing methods that summarize at least some of the discussions above. Shown are methods executed in control units 130, 140 for controlling a heavy vehicle 100. The method includes: obtaining S1 input data indicating desired wheel forces Fx, Fy to be generated by at least one wheel 210 of the vehicle 100; and, obtaining S2 an inverse tire model f associated with the wheel 210 -1 , where the inverse tire model depends on the current operating conditions of the wheel 210. The method further includes: converting S3 the input data into corresponding equivalent wheel speeds or wheel slip ratios to be maintained by the wheel 210 based on the inverse tire model of the wheel 210 to generate the desired wheel forces Fx, Fy; and, controlling S4 the heavy vehicle 100 based on the equivalent wheel speed or wheel slip ratio.

[0168] Figure 8 The components of the control unit are schematically shown in terms of a number of functional units, such as VUCs 130, 140. According to the embodiments discussed herein, the control unit may implement one or more of the above functions of the TSM 270, VMM 260, and / or MSD control function 230. The control unit is configured to perform at least some of the functions for controlling the heavy vehicle 100 discussed above. Processing circuitry 810 is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc. capable of executing software instructions stored in a computer program product in the form of, for example, a storage medium 820. The processing circuitry 810 may further be provided as at least one application specific integrated circuit ASIC or field programmable gate array FPGA.

[0169] Specifically, the processing circuitry 810 is configured to cause the control unit 101 to perform a set of operations or steps, such as in connection with Figure 7 the method discussed. For example, the storage medium 820 may store the set of operations, and the processing circuitry 810 may be configured to retrieve the set of operations from the storage medium 820 to cause the control unit 900 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 810 is arranged to perform the methods disclosed herein.

[0170] The storage medium 820 may also include a persistent storage device, for example, the persistent storage device may be any one of a magnetic memory, an optical memory, a solid state memory, or even a remotely mounted memory or a combination thereof.

[0171] The control unit 900 may also include an interface 830 for communicating with at least one external device. Thus, the interface 830 may include one or more transmitters and receivers, including analog and digital components and a suitable number of ports for wired or wireless communication.

[0172] The processing circuit 810 controls the general operation of the control unit 900, for example, by sending data and control signals to the interface 830 and the storage medium 820, receiving data and reports from the interface 830, and retrieving data and instructions from the storage medium 820. Other components of the control node and related functions are omitted to avoid obscuring the concepts presented here.

[0173] Figure 9 A computer-readable medium 910 carrying a computer program is illustrated, the computer program including program code components 920 for performing a method according to Figure 7 as shown in. The computer-readable medium and the code components together may form a computer program product 900.

[0174] Figure 10 An exemplary vehicle start-up scenario 1000 is shown, in which the techniques disclosed herein may be advantageously used. The vehicle 100 will experience varying friction conditions 1030, 1040, 1050 as it accelerates 1020. The road 1010 may also be uneven and / or inclined. Since rapid control of wheel torque is required when road or vehicle conditions change, torque-based start control without a wheel speed limit will face challenges. For example, the VMM may operate at an update rate of approximately 10 milliseconds, while the MSD control unit 230 may operate at an update rate of approximately 1 millisecond (i.e., 10 times faster). This means that compared to VMM-based control, the MSD control unit 230 can adjust to transient effects faster and thus overcome unforeseen resistances during vehicle start-up in a better way, while VMM-based control responds more slowly to unforeseen changes in driving conditions. On the other hand, the proposed technique simply determines appropriate target wheel slip rate values to be maintained by different MSD control units on each driven wheel and transmits these target wheel slip rate values (or associated wheel speed limits determined based on the desired wheel slip rate values) to the MSD control units, which then control the motor to maintain the wheel slip rate at or below the requested value by setting appropriate wheel speeds according to the vehicle speed and the configured target wheel slip rate or wheel slip rate limit. In this way, the control is moved down in the control stack, closer to the actual motor, which improves the overall vehicle start-up performance. For example, if Figure 10If the current motor speed at one or more wheels of the vehicle 100 is higher than the wheel speed upper limit, the motor controller reduces the applied motor torque. The motor torque continues to decrease until the motor speed is lower than or equal to the speed upper limit. Additionally, if the motor speed is measured to be lower than the speed lower limit, the torque applied to the electric machine should be increased relative to the last time step. The motor torque should continue to increase until the motor speed is higher than or equal to the speed lower limit.

[0175] Figure 11 A method for moving a heavy vehicle 100 is shown, the method comprising: obtaining SB1 a movement instruction for moving the vehicle 100; determining SB2 a target wheel slip ratio limit value λ associated with a wheel slip ratio suitable for executing the movement instruction target and controlling SB3 the wheel speed ω to keep the wheel slip ratio of the vehicle 100 below the target wheel slip ratio limit value λ target . As discussed herein, the wheel slip ratio limit (or equivalently, the wheel speed limit value) can be configured based on the wheel speed. For example, generally, the wheel speed limit can be configured based on the desired wheel slip ratio such that excessive wheel slip does not occur. In this way, a controlled vehicle start is obtained in an efficient manner because: contrary to torque-only control, the control is directly based on the wheel speed relative to the vehicle speed. The control can be shifted more towards one or more propulsion units away from central vehicle control, which is an advantage because a higher bandwidth control loop (faster loop) can be achieved in this way. Since the bandwidth of local control is increased compared to the bandwidth of central control, unforeseen resistances and transients can be better handled.

[0176] According to the present disclosure, the electric machine WEM is requested to keep the wheel slip ratio below the target wheel slip ratio limit value λ that has been determined based on the movement instruction for moving the vehicle (or equivalently, the target wheel speed limit corresponding to the wheel slip ratio limit). target . For example, during a start operation, the electric machine can simply apply a wheel speed close to the configured wheel speed limit value. For example, if the target wheel slip ratio limit value is set to 0.1, the wheel rotational speed will be continuously set by the WEM with a relative difference of 0.1 higher than the vehicle speed, so that the wheel will always slip by the configured amount or slightly less than the configured amount. In other words, the target wheel speed difference relative to the vehicle speed is configured and then controlled. This is possible at least in part because the electric machine is capable of quickly delivering high torque, i.e., it can generally produce any wheel slip ratio requested of it (although it is not recommended to request too large a slip ratio as this will cause tire burnout). The peak torque capacity of the electric machine is usually high but can only be obtained for a limited time. Therefore, it may be advantageous to draw peak torque from one or more electric machines during vehicle start.

[0177] A known method of controlling a vehicle during startup is torque-based control, which means sending a torque request to the motor, and then the motor tries to achieve these torque requests to the best of its ability under the constraint of a certain slip rate limit. Compared with the known startup methods for heavy vehicles, the proposed method brings the control closer to the motor.

[0178] According to some aspects, the method includes controlling the wheel speed ω of the SB31 to keep the wheel slip rate of the corresponding wheel of the vehicle 100 below the target wheel slip rate limit value λ based on the following relationship target :

[0179]

[0180] where ω represents the wheel speed, and λ target represents the target wheel slip rate limit value, v ref is the reference speed, and v x is the vehicle speed in the wheel reference frame, and R represents the wheel radius.

[0181] According to some aspects, the motion command SB11 includes the requested acceleration a of the vehicle 100 req , and the target wheel slip rate limit λ target is determined for SB21 based on the longitudinal force Fx' required to achieve the requested acceleration.

[0182] According to some aspects, the method includes determining the target wheel slip rate limit value λ of SB212 based on the longitudinal force Fx' required to achieve the requested acceleration and the predetermined relationship 400 between the lateral force Fy and the longitudinal wheel slip rate target .

[0183] According to some aspects, the method includes determining the longitudinal force Fx' required to achieve the requested acceleration for SB211 based on the relationship Fx' = m * a req , where m is the mass of the vehicle 100, and a req is the requested acceleration of the vehicle 100.

[0184] According to some aspects, the predetermined relationship 400 between the lateral force Fy and the longitudinal wheel slip rate is pre-configured for SB213 based on the estimated road conditions.

[0185] According to some aspects, the motion command SB12 includes the requested final velocity v of the vehicle 100 req , and the target wheel slip rate limit λ target is the pre-configured wheel slip rate limit value SB22.

[0186] According to some aspects, the method includes controlling the SB311 wheel speed ω based on the following relationship to keep the wheel slip ratio of the vehicle 100 below the target wheel slip ratio limit value λ target :

[0187]

[0188] where v ref is set to the requested final speed v of the vehicle 100 req .

[0189] According to some aspects, the method includes controlling the SB32 wheel speed ω to keep the vehicle acceleration below a preconfigured maximum acceleration value.

[0190] According to some aspects, the method includes controlling the SB33 speed ω to keep the wheel speed below a preconfigured maximum wheel speed value.

[0191] According to some aspects, the method includes: if the vehicle speed v x is higher than the configured threshold speed v lim , then controlling the SB34 vehicle speed v based on a torque request with a fixed wheel slip ratio limit x .

[0192] According to some aspects, the motion command SB13 includes the distance d traveled by the vehicle 100 from stop to stop req , and the method includes integrating the SB4 wheel speed over time to reach the following distance d req :

[0193] d req = ∫ωR dt

[0194] According to some aspects, the motion command corresponds to a request to apply peak torque over a limited time period.

[0195] According to some aspects, the method includes transmitting an SB5 wheel speed request to the motor connected to the drive wheels through an open differential device, where the method includes the motor controlling the wheel speed ω to keep the wheel slip ratio of the vehicle 100 below the target wheel slip ratio limit value λ target .

[0196] According to some aspects, the method includes: increasing the target wheel slip ratio limit value λ target from an initial value to a predetermined final value within a configured time period.

[0197] Figure 12A method for controlling at least one actuator 220, 250 of a vehicle 100 is shown, the actuators 220, 250 being configured to apply torque to at least one wheel 210 of the vehicle 100. The applied torque is determined by a control function associated with a control bandwidth. The method includes: configuring an SC1 control function to control the applied torque to reduce the difference between a first parameter value related to the current rotational speed of the wheel 210 and a second parameter value related to the target rotational speed limit of the wheel 210; obtaining SC2 data indicative of the current operating condition of the vehicle; and setting the control bandwidth of an SC3 control function according to the current operating condition of the vehicle 100. The method further includes using the control function to control SC4 actuators 220, 250.

[0198] The control function should be interpreted as an operating function configured to apply torque to at least one actuator. Through this control bandwidth, torque can be applied with various response times according to the current operating condition. According to one example, a reduced bandwidth can be associated with an increased torque response time of the actuator. Thus, as the bandwidth increases, torque is applied more quickly. In addition, the value related to the current rotational speed of the wheel and the value related to the target rotational speed of the wheel should be interpreted as values that can be related to both the rotational wheel speed and the wheel slip amount (i.e., the difference between the wheel ground speed and the actual wheel speed). In the latter case, the first parameter can thus be the current wheel slip ratio of the wheel, and the second parameter can be the target wheel slip ratio of the wheel. An advantage is that the bandwidth is controlled based on the current operating condition, which will result in a fast torque response when needed and a lower, milder torque response in other conditions. Thus, since fast, energy-consuming operations are only performed when needed, comfort during operation is improved, and the total energy consumption of the vehicle can be reduced. In addition, when overall vehicle control is optimized, the increased configurability allows additional degrees of freedom. In addition, the control function obtains parameters related to the wheel rotational speed. A common scenario for requesting a certain tire force from the wheel is to use torque control at the actuator level based on a torque request sent from a higher-level control function. However, the latency involved in the communication between different control functions (e.g., via a Controller Area Network (CAN) bus) greatly limits the slip control performance. Thus, a speed-based control function that is advantageous compared to, for example, torque-based control is obtained. In particular, for an electric motor, the locally executed speed-based wheel slip control is faster compared to centrally managed torque control, mainly due to the CAN message cycle time.

[0199] As will be described in further detail below, the method can preferably be carried out using a vehicle motion management system and an actuator control system. When implementing such a vehicle motion management system and an actuator control system, the bandwidth can be controlled in a variety of different ways. For example, the vehicle motion management system can be arranged to transmit a control signal to the actuator control system, the signal including data related to the target bandwidth and the vehicle operating conditions. Thus, the target bandwidth is set / determined by the vehicle motion management system. Based on the target bandwidth, the actuator control system determines the control bandwidth based on various parameters to achieve the target bandwidth.

[0200] The first parameter value mentioned above can be, for example, the rotational speed of the wheel or the current wheel slip ratio of the wheel. Thus, the second parameter value can be the target rotational speed of the wheel or the target wheel slip ratio of the wheel.

[0201] Figure 13 A method for controlling at least one of the actuators 220, 250 to apply torque to at least one wheel 210 of the vehicle 100 is shown. The actuator control system includes a control function, and the applied torque is determined by the control function in association with the control bandwidth. The method includes: determining SC10 a first parameter value related to the current rotational speed of the wheel 210; configuring SC20 the control function to control the applied torque to reduce the difference between the first parameter value and a second parameter value related to the target rotational speed of the wheel 210; and obtaining SC30 data indicating the current operating condition of the vehicle. The method further includes setting SC40 the control bandwidth of the control function according to the current operating condition of the vehicle, and using the control function to control SC50 the actuator.

[0202] According to some aspects, the control function is configured to control the speed of the actuators 220, 250.

[0203] According to some aspects, the increased bandwidth of the control function is associated with an increased torque response of the actuator.

[0204] According to some aspects, a predetermined set of feedback gains of the actuator is used to control the control bandwidth of the control function, each feedback gain being associated with a specific operating condition of the vehicle.

[0205] According to some aspects, the control function is a PID controller.

[0206] According to some aspects, the control function is a proportional controller, and the method further includes obtaining a signal indicating the target bandwidth for the control function and configuring the control function using the target bandwidth and a proportional parameter related to the current operating condition of the vehicle.

[0207] Figure 14A method executed in a vehicle motion management system 260 of a vehicle 100 is shown. The vehicle motion management system is capable of connecting to an actuator control system for transmitting control signals between the vehicle motion management system and the actuator control system. The method includes: obtaining the current speed of the vehicle 100 of SC100; determining the current operating condition of the vehicle 100 of SC200; and transmitting a control signal of SC300 to the actuator control system. The control signal represents an instruction that, when executed by the actuator control system, causes the control function of the actuator control system to apply torque on at least one wheel of the vehicle in association with a control bandwidth to reduce the difference between a first parameter value and a second parameter value: the first parameter value is related to the current rotational speed of the wheel based on the current speed of the vehicle, and the second parameter value is related to the target rotational speed of the wheel. The control bandwidth can be determined according to the current operating condition of the vehicle.

[0208] According to some aspects, the method further includes determining a target speed of the vehicle based on the current operating condition, wherein the target rotational speed of the wheel is based on the target speed of the vehicle.

[0209] According to some aspects, the method further includes determining a desired operating performance of the vehicle based on the current operating condition, wherein the control bandwidth can also be determined according to the desired operating performance of the vehicle.

[0210] According to some aspects, the method further includes determining a target bandwidth and transmitting a control signal including the determined target bandwidth, wherein the control bandwidth can also be determined according to the target bandwidth.

[0211] According to some aspects, the current operating condition of the vehicle is based on at least one of the current vehicle condition and the current road conditions on which the vehicle is operating.

[0212] According to some aspects, the current operating condition is at least one of the current vehicle mass, the road inclination when the vehicle is operating, the vehicle speed, the friction level between the vehicle wheels and the road surface, and the current tire stiffness.

[0213] An actuator control system of the vehicle 100 is also disclosed herein. The actuator control system is configured to at least control actuators 220, 250 to apply torque on at least one wheel of the vehicle. The actuator control system includes a control function, and the applied torque is determined by the control function in association with a control bandwidth. The actuator control system is configured to determine a first parameter value related to the current rotational speed of the wheel, configure the control function to control the applied torque so as to reduce the difference between the first parameter value and a second parameter value related to the target rotational speed of the wheel, obtain data indicating the current operating condition of the vehicle, set the control bandwidth of the control function according to the current operating condition of the vehicle; and use the control function to control the actuator.

[0214] The present disclosure also discloses a vehicle motion management system 260 for a vehicle 100. The vehicle motion management system 260 is capable of connecting to an actuator control system for transmitting control signals between the vehicle motion management system and the actuator control system. The vehicle motion management system is configured to obtain the current speed of the vehicle, determine the current operating condition of the vehicle, and transmit a control signal to the actuator control system. The control signal represents an instruction which, when executed by the actuator control system, causes the control function of the actuator control system to apply torque to at least one wheel of the vehicle in association with a control bandwidth to reduce the difference between a first parameter value and a second parameter value. The first parameter value is related to the current rotational speed of the wheel based on the current speed of the vehicle, the second parameter value is related to the target rotational speed of the wheel, and the control bandwidth is determined according to the current operating condition of the vehicle.

[0215] In addition, the present disclosure discloses a control signal representing an instruction to be executed by the actuator control system of the vehicle 100. The control signal includes a vehicle speed component that enables the actuator control system to determine the current rotational speed of the wheel 210 and a vehicle operating condition component representing the instruction. When executed by the actuator control system, these instructions cause the control function of the actuator control system to apply torque to at least one wheel of the vehicle in association with a control bandwidth to reduce the difference between a first parameter value and a second parameter value. The first parameter value is related to the current rotational speed of the wheel based on the current speed of the vehicle, the second parameter value is related to the target rotational speed of the wheel, and the control bandwidth can be determined according to the current operating condition of the vehicle.

[0216] Referring to Figure 8 、 Figure 15 and Figure 16, shows control units 130, 140 for controlling a vehicle wheel 210 provided with a tire 1502. The control unit includes or is operatively connected to a data storage device 820 having stored therein tire models 400, 1504 for the tire, wherein in the tire model, the longitudinal tire force Fx is represented at least as a function of the longitudinal wheel slip ratio λ, which depends on the rotational speed of the wheel and the speed of the vehicle. The control unit is configured to receive at least one tire parameter input, which includes a measurement of at least one parameter affecting the longitudinal slip stiffness of the tire, and to correct the function in the stored tire model based on the received tire parameter input. The control unit is further arranged to obtain or generate a wheel torque request, convert the obtained or generated wheel torque request into a wheel rotational speed limit request based on the corrected function, and send the wheel rotational speed limit request to an actuator to provide a wheel rotational speed below the wheel rotational speed limit request. This concept is based on the recognition that by providing torque control at the same vehicle subsystem as slip control, latency problems can be avoided. Such a subsystem has a relatively short response time compared to a vehicle control unit that conventionally sends torque requests. More specifically, it has been recognized that by using a tire model in which the longitudinal tire force is at least a function of the longitudinal wheel slip ratio, a slip control subsystem can be used to provide a slip request corresponding to a desired longitudinal force. In particular, it has been recognized that in addition to providing the advantage of a fast response time, for this control to be accurate, the tire model should be capable of being corrected based on one or more parameters affecting the tire slip stiffness. Thus, in general, by adapting the force / slip ratio-based tire model to the current state or current driving conditions of the tire, accurate and fast control of the wheel can be achieved. The wheel slip ratio limit value and / or the wheel speed limit value can be determined and configured in a similar manner.

[0217] As previously explained, in order to provide accurate control of the wheel 210 based on the tire model 400, the tire model should be updated to the current conditions. Here, the control of the wheel should be interpreted broadly to include control actions such as torque control, where the applied torque is controlled to follow a target torque, speed control, or wheel slip control, where in speed control, the wheel rotational speed is controlled to follow a target speed, and in wheel slip control, the wheel speed or torque is controlled to follow the target wheel slip ratio as closely as possible.

[0218] The tire can be affected by various different factors such as ambient temperature, inflation pressure, normal load, age, wear, etc. These and other factors can be appropriately quantified as measurable parameters and provided as tire parameter inputs. Thus, referring to Figure 3, when the VMM 260 obtains a wheel torque request or otherwise determines the desired tire force to be generated at the wheel 210, it can convert the obtained wheel torque request or the desired tire force into a wheel rotational speed request or a wheel slip ratio request based on the calibration function of the tire model. Equivalently, a wheel speed limit and / or a wheel slip ratio limit can be determined and sent as a request to the MSD control unit 230.

[0219] According to some aspects, the tire 1502 forms part of a kit 1500 that also includes a tire model 1504, which is described in Figure 15 by a flash drive (e.g., a USB flash drive). However, the tire model signal 1504 can be stored on various conceivable media and does not have to be physically transmitted with the tire 1502, but can be accessed by downloading the tire model 1504 from a remote server or the like.

[0220] The at least one parameter is optionally selected from the group consisting of:

[0221] - The age t of the tire act ,

[0222] - The ambient temperature T act

[0223] - The inflation pressure P of the tire act ,

[0224] - The normal load on the tire, and

[0225] - The wear of the tire, suitably approximated as the distance d traveled by the tire act .

[0226] According to some aspects, the control unit is configured to correct the function in the stored tire model 400 by applying a slip stiffness correction factor c p , c T , c a , c w to the function, where the slip stiffness correction factor varies with respect to the parameter.

[0227] According to some aspects, the control unit is configured to receive a plurality of different tire parameter inputs, each tire parameter input including a measured value of a respective one of the plurality of parameters that affect the longitudinal slip stiffness of the tire. The control unit is also configured to correct the function in the stored tire model 400 by applying a combined correction factor to the function, the combined correction factor being a function of a plurality of slip stiffness correction factors, where each slip stiffness correction factor varies with respect to the respective parameter of the plurality of parameters.

[0228] According to some aspects, the at least one tyre parameter input is a primary tyre parameter input, and the at least one parameter is a primary parameter, wherein the control unit is further configured to correct the function in the stored tyre model 400 based on at least one secondary tyre parameter input, the secondary tyre parameter input including measured values of at least one secondary parameter selected from the group consisting of:

[0229] - rolling radius,

[0230] - nominal peak friction, and

[0231] - coefficient of rolling resistance.

[0232] According to some aspects, the control units 130, 140 are configured to calculate a slip ratio request based on the corrected function when converting a wheel torque request into a wheel rotational speed request, and convert the slip ratio request into a wheel rotational speed request using the following slip ratio formula:

[0233]

[0234] where λ is the longitudinal wheel slip ratio, where Rω is the rotational speed of the wheel, where R is the radius of the wheel in metres, ω is the angular velocity of the wheel, and where v x is the longitudinal speed of the wheel.

[0235] Figure 16 Illustrated is a method for controlling torque applied to a vehicle wheel provided with a tyre, comprising: receiving at least one tyre parameter input, the tyre parameter input including measured values of at least one parameter affecting the longitudinal slip stiffness of the tyre; and correcting a tyre model based on the received tyre parameter input, wherein in the tyre model, the longitudinal tyre force is represented as a function of the longitudinal wheel slip ratio, the longitudinal wheel slip ratio depending on the rotational speed of the wheel and the speed of the vehicle, wherein the step of correcting the tyre model includes correcting the function. The method further includes:

[0236] obtaining or generating a wheel torque request, converting the obtained or generated wheel torque request into a wheel rotational speed request based on the corrected function, and sending the wheel rotational speed request to an actuator to provide a wheel rotational speed corresponding to the wheel rotational speed request.

[0237] According to some aspects, the at least one parameter is selected from the group consisting of:

[0238] - age of the tyre,

[0239] - ambient temperature,

[0240] - The inflation pressure of the tire,

[0241] - The normal load of the tire, and

[0242] - The wear of the tire, suitably approximated as the distance traveled by the tire.

[0243] According to some aspects, the action of correcting SD2 includes applying a slip stiffness correction factor to the function, the slip stiffness correction factor varying with respect to the parameter.

[0244] According to some aspects, the method further includes receiving a plurality of different tire parameter inputs, each tire parameter input including a measured value of a respective one of a plurality of parameters that affect the longitudinal slip stiffness of the tire, wherein the correcting step includes applying a combined correction factor to the function, the combined correction factor being a function of a plurality of slip stiffness correction factors, each slip stiffness correction factor varying with respect to a respective one of the plurality of parameters.

[0245] According to some aspects, the at least one tire parameter input is a primary tire parameter input, and the at least one parameter is a primary parameter, wherein the action of correcting SD2 includes correcting the function in the stored tire model based on at least one secondary tire parameter input, the secondary tire parameter input including a measured value of at least one secondary parameter selected from the group consisting of:

[0246] - Rolling radius,

[0247] - Nominal peak friction force, and

[0248] - Rolling resistance coefficient.

[0249] According to some aspects, the action of converting SD4 includes calculating a slip ratio limit request based on the corrected function and converting the slip ratio limit request into a wheel rotational speed limit request using a slip ratio formula:

[0250]

[0251] where λ is the longitudinal wheel slip ratio, where Rω is the rotational speed of the wheel, where R is the radius of the wheel in meters, ω is the angular velocity of the wheel, and where V x is the longitudinal speed of the wheel.

[0252] Refer to Figure 2, according to a non-limiting example, the vehicle motion management system 260 includes a torque module 202, a wheel slip ratio module 204, and a friction module 206. The vehicle motion management system 260 is also arranged to receive a vehicle operation signal s, which includes data that can be operated by the vehicle motion management system 260 and its various modules 202, 204, 206. The vehicle operation signal s provided to the vehicle motion management system 260 may include, for example, data in the form of signals indicating the current environment of the vehicle, the current traffic conditions, the vehicle weight parameters (e.g., if the vehicle is fully loaded, unloaded, partially loaded, etc.). The vehicle motion management system 260 may also receive other signals indicating specific vehicle conditions, such as the current vehicle operating conditions as described below. The torque module 202, the wheel slip ratio module 204, and the friction module 206 are configured to transmit communication signals among each other, that is, different modules are configured to communicate with each other, which will be apparent from the following disclosure. It should be readily understood that the torque module 202, the wheel slip ratio module 204, and the friction module 206 are shown as separate components only for illustrative purposes. Of course, the vehicle motion management system 260 may also simply include various control functions themselves that perform the functions described below.

[0253] According to another example, vehicle motion management includes normal driver control inputs (i.e., manual steering inputs) and acceleration and braking inputs indicating the desired torque.

[0254] Accordingly, a vehicle motion management system for a vehicle is provided, which is capable of being connected to a motion support system for communicating control signals between the vehicle motion management system and the motion support system. The vehicle motion management system is configured to determine a desired torque for operating the vehicle in a current vehicle operating condition; determine a wheel slip rate limit of at least one wheel of the vehicle; determine a wheel speed limit of the at least one wheel of the vehicle based at least on the wheel slip rate limit; and transmit a control signal indicating the desired torque and the wheel speed limit to the motion support system. The vehicle motion management system and the motion support system are control systems of the vehicle, and each of these control systems is arranged to perform various control functions for controlling the operation of the vehicle, particularly for controlling the operation of the wheels. The vehicle motion management system is preferably configured to receive and determine wheel parameters at a higher level, that is, the vehicle motion management system determines the desired torque and the wheel slip rate limit in a more generalized form, while the motion support system is arranged as a lower-level control system, which is configured to convert the parameters received from the vehicle motion management system into appropriate parameters of the actuator. Before forwarding the actuator signal to the actuator, the motion support system takes into account the current driveline state(s). For example, the current driveline state may relate to the current vehicle transmission state, the gear of the vehicle transmission, or the transmission clutch actuation state. For example, the desired torque may be received from the vehicle operator stepping on the accelerator pedal and / or stepping on the brake pedal. The desired torque may also be received from a system for autonomously controlling the vehicle propulsion operation or from an advanced driver assistance system (ADAS). The wheel slip rate limit should be interpreted as the maximum allowable wheel slip rate of the at least one wheel during operation. The wheel slip rate is the relative longitudinal motion between the vehicle wheel and the ground, i.e., the amount of "slip". Considering the wheel radius, the wheel slip rate can be determined as the relationship between the wheel longitudinal speed and the wheel rotational speed. Thus, the wheel speed limit is based on the wheel speed relative to the road surface, as seen in a wheel-based coordinate system. According to an example embodiment, the vehicle motion management system may be configured to determine a current rotational wheel speed and a current longitudinal wheel speed of at least one wheel of the vehicle; and determine the wheel slip rate of the at least one wheel based on the current rotational wheel speed and the current longitudinal wheel speed. As discussed above, the configured wheel slip rate limit is equivalent to the configured wheel speed limit in many aspects, where the wheel speed limit is determined in real time according to the vehicle ground speed.

[0255] The present disclosure is based on the recognition that the calculation of the wheel slip rate limit can be performed by a higher-level vehicle motion management system by transmitting a control signal indicating the desired torque in combination with the wheel speed limit to a motion support system. When calculating the wheel slip rate, the denominator in the wheel slip rate equation consists of the wheel rotational speed of the wheel. Thus, at low vehicle speeds, this denominator approaches zero or tends to zero, which can lead to sources of error when calculating the wheel slip rate. Therefore, it is advantageous to perform the wheel slip rate in a higher-level vehicle motion management system because potential inconsistencies when calculating the wheel slip rate by a separate motion support system can be avoided. Thereby, improved wheel slip rate consistency is achieved.

[0256] In addition, when operating a vehicle using an electric motor, it is particularly advantageous to transmit a control signal indicating the desired torque and the wheel speed limit to the motion support system because the electric motor can be speed and torque controlled. In contrast to slip rate control, speed control is also easier to implement for, e.g., service brakes because the rotational speed is a common output of a tire torque balancing system and does not include any non-linearity present in the wheel slip rate equation.

[0257] According to an example embodiment, the wheel speed limit may further be based on the desired torque. Thus, the desired torque (i.e., the torque request) is used to calculate the slip rate limit, which is used when calculating the wheel speed limit.

[0258] According to an example embodiment, the wheel speed limit may include a wheel speed upper limit and a wheel speed lower limit. The vehicle motion management system may further be configured to transmit the wheel speed upper limit to

[0259] The functional operation of the vehicle motion management system 260 will be described below. In particular, the vehicle motion management system 260 is arranged to receive an input signal having information related to the current vehicle operating condition. For example, the current vehicle operating condition may include data indicating the wheel friction level between the wheels of the vehicle and the road surface, or the current weight of the vehicle, i.e., if the vehicle is unloaded, fully loaded, or partially loaded, or the road topology on which the vehicle is currently operating. Thus, the various operating conditions may be received by the vehicle motion management system 260 as separate components, or as components using all the different operating conditions as an overall vehicle operating condition. Suitable sensors may be used to determine the different operating conditions of the vehicle and transmit them to the vehicle motion management system 260.

[0260] As described above, the vehicle motion management system 260 further includes a friction module 206. According to an exemplary embodiment, the vehicle motion management system 260 is arranged to use the friction module 206 to determine the wheel friction level between at least one wheel and the road surface. The vehicle motion management system 260 may determine the current vehicle operating condition based on the determined wheel friction level.

[0261] The torque module 202 is adapted to determine the desired torque for operating the vehicle in the current vehicle operating condition. Thus, the vehicle motion management system 260 determines a torque request in the above-mentioned higher-level vehicle motion management system 260 to appropriately control the vehicle 100 in the current operating condition.

[0262] For example, the desired torque may be determined based on the current accelerator pedal position, brake pedal position, or a signal received from the autonomous vehicle operating system.

[0263] The wheel slip ratio module 204 is arranged to determine the wheel slip ratio limit of at least one wheel 210 of the vehicle 100. Thus, the maximum allowable wheel slip ratio of the vehicle is determined, where the wheels of the vehicle are not allowed to exceed such a wheel slip ratio limit.

[0264] The wheel slip ratio limit can be determined by using, for example, the model 400 discussed in conjunction with Figure 4 Accordingly, the vehicle motion management system 260 can convert a force request into a slip ratio request, and thereby set the slip ratio limit based on the slip ratio request. According to another example, the slip ratio limit can be set to a fixed value independently of the force request. The slip ratio limit can also be based on a signal indicating the current friction level between the road surface and the tire surface.

[0265] Based on the wheel slip ratio limit, the wheel slip ratio module 204 is configured to determine the wheel speed limit of at least one wheel. Thus, the vehicle motion management system 260 performs a wheel slip ratio limit calculation and a wheel speed limit calculation. According to a non-limiting example, the wheel speed limit ω w,sl can be determined according to the following equation:

[0266]

[0267] where:

[0268] λ lim is the wheel slip ratio limit; and

[0269] T Reg is the desired torque.

[0270] In the case where the wheel speed is relatively low (i.e., close to zero), the vehicle motion management system 260 may be arranged to determine the wheel slip ratio based on the offset wheel speed parameter. Thus, the offset wheel speed limit may be calculated according to the following non - restrictive equation:

[0271] ω w，ol =V x，w / Rw+max(|λ lim |k ol ,ω w，ol，max )sgn(λ)

[0272] Where:

[0273] ω w,ol is the wheel speed limit calculated according to the speed offset limit;

[0274] k ol,ω and ω ol,max are the gain and the maximum speed offset parameter used to convert the slip ratio limit into the offset limit; and

[0275] sgn(λ) is the sign function, which is equal to 1 during acceleration and equal to - 1 during deceleration.

[0276] In addition, the wheel speed limit may also include a wheel speed upper limit and a wheel speed lower limit. Among them, the wheel speed upper limit is used during acceleration, that is, during propulsion, while the wheel speed lower limit is used during deceleration, that is, during braking. When the wheel slip ratio limit is positive and the desired torque is greater than zero (i.e., during acceleration), the wheel speed upper limit is used, and when the wheel slip ratio limit is negative and the desired torque is less than zero (i.e., during deceleration), the wheel speed lower limit is used. In addition, the wheel slip ratio limit is within a predetermined range and is defined as:

[0277] -1<λ lim <1

[0278] In Figure 4 the wheel slip ratio characteristics with respect to the longitudinal tire force and the lateral tire force are depicted. Thus, Figure 4 shows a model 400 representing the relationship between the calculated longitudinal wheel slip ratio and the estimated longitudinal wheel force value. This model can also represent the relationship between the maximum available lateral wheel force for a given longitudinal wheel slip ratio. For a predetermined lateral slip angle of the tire, this model can also represent the lateral wheel force achieved for a given longitudinal wheel slip ratio. The vertical axis represents the tire force generated between the surface supporting the wheel and the wheel 210 itself, while the horizontal axis represents the longitudinal wheel slip ratio of the wheel.

[0279] Referring again to Figure 2, when the wheel speed limit and the desired torque have been determined, the vehicle motion management system 260 transmits a control signal to the motion support system or the MSD control unit 230 via the interface 265, wherein the control signal indicates the desired torque and the wheel speed limit.

[0280] The motion support system 230 may include an actuator torque module. The actuator torque module is configured to determine an actuator-specific torque, that is, to convert the data of the desired torque from the vehicle motion management system 260 into data related to the actuator. Specifically, the actuator torque module determines the operating torque based on the desired torque received from the vehicle motion management system 260 and based on the current driveline state of the vehicle 100.

[0281] The actuator torque module also determines the actuator rotational speed limits of the actuators 220, 250. The actuator rotational speed limits are based on the wheel speed limits received from the vehicle motion management system 260. The actuator rotational speed limits may also be based on the current driveline state. Thus, the motion support system 230 has converted the wheel speed limits received from the vehicle motion management system 260 into wheel-specific rotational wheel speed limits.

[0282] Thereafter, the motion support system 230 transmits actuator control signals 590 to the actuators 220, 250 to generate an operating torque on the wheels 210 without exceeding the actuator rotational speed limits.

[0283] In summary, a vehicle motion management system 260 for a vehicle is disclosed herein. The vehicle motion management system is capable of being connected to a motion support system 230 for transmitting control signals between the vehicle motion management system 260 and the motion support system 230, wherein the vehicle motion management system is configured to determine the desired torque for operating the vehicle under current vehicle operating conditions, determine the wheel slip rate limit of at least one wheel of the vehicle, determine the wheel speed limit of the at least one wheel of the vehicle based at least on the wheel slip rate limit; and transmit a control signal indicating the desired torque and the wheel speed limit to the motion support system 230.

[0284] According to some aspects, the wheel speed limit is further based on the desired torque.

[0285] According to some aspects, the wheel speed upper limit and the wheel speed lower limit or the wheel slip rate limit are determined and transmitted to the motion support system 230.

[0286] According to some aspects, the wheel speed limit includes an upper wheel speed and a lower wheel speed, and the vehicle motion management system is configured to transmit the upper wheel speed to the motion support system 230 at least when the desired torque is higher than zero, and transmit the lower wheel speed to the motion support system 230 at least when the desired torque is lower than zero.

[0287] According to some aspects, the vehicle motion management system 260 is further configured to determine an offset wheel speed parameter, obtain a signal indicative of the vehicle wheel speed, and determine a wheel slip ratio limit based on the offset wheel speed parameter when the wheel speed is lower than a threshold vehicle speed limit.

[0288] According to some aspects, the vehicle motion management system 260 is further configured to determine the current rotational wheel speed and the current longitudinal wheel speed of at least one of the vehicle's wheels, and determine the wheel slip ratio of the at least one wheel based on the current rotational wheel speed and the current longitudinal wheel speed.

[0289] According to some aspects, the wheel slip ratio limit is within a predetermined wheel slip ratio range.

[0290] According to some aspects, the vehicle motion management system 260 is further configured to obtain a signal indicative of the current accelerator pedal position of the vehicle's accelerator pedal, and determine the desired torque based on the current accelerator pedal position.

[0291] According to some aspects, the desired torque is determined based on a signal received from the autonomous vehicle operating system.

[0292] According to some aspects, the vehicle motion management system 260 is further configured to determine the wheel friction level between at least one wheel and the road surface, and determine the current vehicle operating condition based on the determined wheel friction level.

[0293] Also disclosed herein is a motion support system 230 for a vehicle, the motion support system 230 being connectable to a vehicle motion management system 260 and at least one actuator, the at least one actuator being configured to apply torque to at least one wheel of the vehicle. The motion support system 230 is configured to receive a control signal from the vehicle motion management system 260, the control signal indicating the desired torque for operating the vehicle in the current vehicle operating condition and indicating the wheel speed limit of the at least one wheel of the vehicle, determine the current vehicle driveline state of the vehicle, determine an operating torque and an actuator rotational speed limit based on the current vehicle driveline state, the desired torque, and the wheel speed limit, and transmit an actuator signal to the actuator to cause the actuator to generate an operating torque on the at least one wheel without exceeding the actuator rotational speed limit.

[0294] According to some aspects, the current vehicle driveline state is one of the gear position of the current vehicle transmission state of the vehicle transmission or the transmission clutch actuation state.

[0295] According to some aspects, the wheel motion system 230 is a decentralized wheel motion system 230 that can be connected to a wheel-specific actuator, which is configured to control an individual wheel of the vehicle.

[0296] Figure 17 A method for controlling an actuator of a vehicle is described, the actuator being configured to apply torque to at least one wheel 210 of the vehicle, wherein the method includes: determining SE1 the desired torque for operating the vehicle in the current vehicle operating condition, determining SE2 the wheel slip rate limit of the at least one wheel of the vehicle, determining SE3 the wheel speed limit of the at least one wheel of the vehicle based at least on the wheel slip rate limit, determining SE4 the operating torque and the actuator rotational speed limit based on the desired torque, the wheel speed limit, and the current vehicle driveline state, and controlling SE5 the actuator to generate an operating torque on the at least one wheel without exceeding the actuator rotational speed limit.

[0297] Note that the torque request may come from the propulsion management system (possibly not considering lateral motion, etc.). In an intuitive way, the wheel speed limit or the wheel slip rate limit can be directly converted into a motor speed limit. Therefore, such limits are considered equivalent herein. Additionally, as discussed herein, at lower speeds, "speed offset" can be used instead of wheel slip.

[0298] A control signal representing an instruction to be executed by the motion support system 230 is disclosed herein, the control signal including a torque component that enables the motion support system 230 to determine the operating torque and a wheel speed limit component representing wheel speed limit data, which, when executed by the motion support system 230, causes the motion support system 230 to generate an actuator signal corresponding to the operating torque that is subject to the actuator rotational speed limit, and the actuator rotational speed limit can be determined based on the wheel speed limit component in consideration of the current vehicle driveline state.

[0299] A motion support device MSD control unit 230 for a heavy vehicle 100 is also disclosed herein, the control unit 230 being configured to control one or more MSDs 220, 250 associated with at least one wheel 210 on the vehicle 100.

[0300] Wherein, the MSD control unit 230 is arranged to be communicatively coupled 265 to a vehicle motion management VMM unit 260 for receiving control commands including wheel speed limits and / or wheel slip ratio limit requests from the VMM unit 260 to control vehicle motion via the one or more MSDs 220, 250,

[0301] Wherein, the MSD control unit 230 is arranged to obtain a range of capabilities indicating the range of wheel behavior of the wheel 210 for which the VMM unit 260 is permitted to influence the behavior of the wheel via the control commands, and

[0302] Wherein, the MSD control unit 230 is arranged to monitor the wheel behavior and detect whether the wheel behavior is outside the range of capabilities,

[0303] Wherein, the MSD control unit 230 is arranged to trigger a control intervention function in the case where the monitored wheel behavior is outside the range of capabilities.

[0304] According to some aspects, the one or more MSDs include at least one service brake 220 arranged to generate negative torque via the wheel 210.

[0305] According to some aspects, the one or more MSDs include at least one propulsion unit 250 arranged to generate positive and / or negative torque via the wheel 210.

[0306] According to some aspects, the range of capabilities includes upper limits of allowable positive and / or negative longitudinal wheel slip ratios and / or wheel rotational speeds.

[0307] According to some aspects, the range of capabilities includes upper limits of allowable positive and / or negative longitudinal wheel accelerations.

[0308] According to some aspects, the range of capabilities includes upper limits of allowable positive and / or negative vehicle yaw rates.

[0309] According to some aspects, the range of capabilities includes lower limits of allowable positive and / or negative longitudinal wheel slip ratios and / or wheel rotational speeds.

[0310] According to some aspects, the range of capabilities includes lower limits of allowable positive and / or negative longitudinal wheel accelerations.

[0311] According to some aspects, the range of capabilities includes lower limits of allowable positive and / or negative vehicle yaw rates.

[0312] According to some aspects, the MSD control unit 230 is arranged to receive wheel speed data associated with the wheel 210 from the wheel speed sensor 240 and to detect whether the wheel behavior is outside the capability range based on the wheel speed data.

[0313] According to some aspects, the MSD control unit 230 is arranged to obtain a fixed capability range as a parameter loaded from a memory or received from an external configuration entity.

[0314] According to some aspects, the MSD control unit 230 is arranged to continuously obtain an updated capability range.

[0315] According to some aspects, the control intervention function includes performing an intervention function by one or more of the MSDs 220, 250.

[0316] According to some aspects, wherein the control intervention function includes triggering a request for an external arbiter function for direct MSD control by the MSD control unit 230.

[0317] According to some aspects, the MSD control unit 230 is arranged to monitor the wheel behavior by filtering samples of the wheel behavior over time and to detect whether the wheel behavior is outside the capability range based on the result of the filtering.

[0318] Also disclosed herein is a vehicle motion management (VMM) unit 260, which is arranged to perform vehicle motion management for controlling the motion of a heavy vehicle 100 by means of one or more motion support devices (MSDs) 220, 250 associated with at least one wheel 210 on the vehicle 100.

[0319] Wherein, the VMM unit 260 is arranged to be communicatively coupled 265 to the MSD control unit 230 for transmitting a control command including a wheel speed and / or a wheel slip rate request to the MSD control unit 230, thereby controlling the vehicle motion by means of the one or more MSDs 220, 250.

[0320] Wherein, the VMM unit 260 is arranged to obtain a capability range indicating the range of wheel behavior of the wheel 210, for which the VMM unit 260 is allowed to influence the behavior of the wheel by means of the control command, and

[0321] Wherein, the VMM unit 260 is arranged to generate the control command such that the wheel behavior is within the capability range.

[0322] According to some aspects, the VMM unit 260 includes an arbitration function configured to receive requests directly controlled by the MSD control unit 230 and cede vehicle control to the MSD control unit 230 when the wheel behavior is within a predetermined wheel behavior safety range.

[0323] Figure 18 A method for controlling the movement of a heavy vehicle 100 is shown, the method including:

[0324] Configuring the SF1 motion support device MSD control unit 230 to control one or more MSDs 220, 250 associated with at least one wheel 210 on the vehicle 100,

[0325] Configuring the SF2 vehicle motion management VMM unit 260 to perform vehicle motion management by the one or more MSDs 220, 250 via control commands transmitted to the MSD control unit 230,

[0326] Defining an SF3 capability range that indicates a range of wheel behavior of the wheel 210 for which the VMM unit 260 is allowed to influence the wheel behavior via the control commands,

[0327] Monitoring the SF4 wheel behavior, and

[0328] Triggering an SF5 control intervention function by the MSD control unit 230 when the monitored wheel behavior is outside the defined capability range.

Claims

1. A vehicle motion management system (260) for a vehicle, the vehicle motion management system being capable of being connected to a motion support system (230) for transmitting control signals between the vehicle motion management system and the motion support system, the vehicle motion management system (260) transmitting a control signal to the motion support system (230), the motion support system (230) controlling at least one actuator configured to receive the control signal from the vehicle motion management system (260) and apply torque to at least one wheel of the vehicle, the at least one actuator including an electric motor, wherein, The vehicle motion management system is configured to: Determine a desired torque for operating the vehicle under the current vehicle operating conditions; Determine a wheel slip rate limit for at least one wheel of the vehicle; Determine a wheel speed limit for at least one wheel of the vehicle based at least on the wheel slip rate limit and the wheel ground speed (vx) of at least one wheel of the vehicle; And Transmit a control signal indicating the desired torque and the wheel speed limit to the motion support system (230).

2. The vehicle motion management system (260) according to claim 1, wherein, The wheel speed limit is further based on the desired torque and / or the current wheel speed.

3. The vehicle motion management system (260) according to claim 2, wherein, The wheel speed limit includes a wheel speed upper limit and a wheel speed lower limit, and the vehicle motion management system is configured to: Transmit the wheel speed upper limit to the motion support system (230) at least when the desired torque is higher than zero; and Transmit the wheel speed lower limit to the motion support system (230) at least when the desired torque is lower than zero.

4. The vehicle motion management system (260) according to any one of claims 1-3, wherein, The vehicle motion management system (260) is further configured to: Determine an offset wheel speed parameter; Obtain a signal indicating the wheel speed of the vehicle; and When the wheel speed is lower than a threshold vehicle speed limit, determine the wheel slip rate limit based on the offset wheel speed parameter.

5. The vehicle motion management system (260) according to any one of claims 1-3, wherein, The vehicle motion management system (260) is further configured to: Determine the current rotational wheel speed and the current longitudinal wheel speed of at least one of the wheels of the vehicle; and Determine the wheel slip rate of at least one wheel based on the current rotational wheel speed and the current longitudinal wheel speed.

6. The vehicle motion management system (260) according to any one of claims 1-3, wherein, The wheel slip rate limit is within a predetermined wheel slip rate range.

7. The vehicle motion management system (260) according to any one of claims 1-3, wherein, The vehicle motion management system (260) is further configured to: Obtain a signal indicating the current accelerator pedal position of the accelerator pedal of the vehicle; and Determine the desired torque based on the current accelerator pedal position.

8. The vehicle motion management system (260) according to any one of claims 1-3, wherein, The desired torque is determined based on a signal received from an autonomous vehicle operating system.

9. The vehicle motion management system (260) according to any one of claims 1-3, wherein, The vehicle motion management system (260) is further configured to: Determine the wheel friction level between at least one wheel and the road surface; and Determine the current vehicle operating conditions based on the determined wheel friction level.

10. A motion support system (230) for a vehicle, the motion support system (230) being connectable to a vehicle motion management system (260) and being connectable to at least one actuator configured to apply torque to at least one wheel of the vehicle, the at least one actuator including an electric motor, the vehicle motion management system (260) transmitting a control signal to the motion support system (230), and the motion support system (230) receiving the control signal from the vehicle motion management system (260) to control the actuator, wherein, The motion support system (230) is configured to: Receive a control signal from the vehicle motion management system (260), the control signal indicating the desired torque for operating the vehicle under the current vehicle operating conditions and indicating the wheel speed limit of at least one wheel of the vehicle, the wheel speed limit being based on the wheel slip rate limit of at least one wheel of the vehicle and the wheel ground speed (vx) of at least one wheel of the vehicle; Determine the current vehicle driveline state of the vehicle; Determine an operating torque and an actuator rotational speed limit based on the current vehicle driveline state, the desired torque, and the wheel speed limit; And Transmit an actuator signal to the actuator (220, 250) to cause the actuator to generate the operating torque on at least one wheel without exceeding the actuator rotational speed limit.

11. The motion support system (230) according to claim 10, wherein, The current vehicle driveline state is one of the following: the current vehicle transmission state, the gear of the vehicle transmission, or the transmission clutch actuation state.

12. The motion support system (230) according to claim 10 or 11, wherein, The motion support system (230) is a decentralized motion support system (230) that can be connected to a wheel-specific actuator, and the wheel-specific actuator is configured to control an individual wheel of the vehicle.

13. A method for controlling an actuator of a vehicle, the actuator including at least an electric motor, a vehicle motion management system (260) transmits a control signal to a motion support system (230), and the motion support system (230) receives the control signal from the vehicle motion management system (260) to control the actuator, the actuator being configured to apply a torque to at least one wheel (210) of the vehicle, wherein, The method includes: Determining a desired torque for operating the vehicle in a current vehicle operating condition; Determining a wheel slip rate limit for at least one wheel of the vehicle; Determining a wheel speed limit for at least one wheel of the vehicle based at least on the wheel slip rate limit and the wheel ground speed (vx) of at least one wheel of the vehicle; Determining (S4) an operating torque and an actuator rotational speed limit based on the desired torque, the wheel speed limit, and the current vehicle driveline state; and Controlling the actuator to generate the operating torque on at least one wheel without exceeding the actuator rotational speed limit.

14. A control signal representing an instruction to be executed by a motion support system (230), the control signal being transmitted by a vehicle motion management system (260) to the motion support system (230), the control signal for the motion support system (230) being used to control at least one actuator configured to receive the control signal from the vehicle motion management system (260) and apply a torque to at least one wheel of the vehicle, the at least one actuator including an electric motor, the control signal including: A torque component that enables the motion support system (230) to determine an operating torque; And A wheel speed limit component representing wheel speed limit data that, when executed by the motion support system (230), causes the motion support system (230) to generate an actuator signal corresponding to the operating torque that is subject to an actuator rotational speed limit, and the actuator rotational speed limit can be determined based on the wheel speed limit component in consideration of the current vehicle driveline state, and the wheel speed limit component is based on the wheel slip rate limit of at least one wheel of the vehicle and the wheel ground speed (vx) of at least one wheel of the vehicle.

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