Capability feedback for heavy vehicle dynamics support systems

Abstract

A control unit (230) for controlling at least one motion support device (MSD) (220, 250, 280) on a large vehicle (100), the control unit (230) configured to determine limit operating points of the MSD (220, 250, 280) associated with performance limits of the MSD, determine preferred operating points of the MSD (220, 250, 280) indicating operating points of the MSD associated with an improvement in a quadratic objective function value compared to the limit operating points, and send a capability message including the limit operating points of the MSD and the preferred operating point of the MSD to a vehicle motion management (VMM) function (260).

Description

[Technical field]

[0001] This disclosure relates to vehicle dynamics management for heavy vehicles, i.e., coordinated control of propulsion actuators and other dynamics aids, such as service brakes and power steering.

[0002] The present invention may be advantageously applied to large vehicles such as trucks, buses, and construction machinery. [Background technology]

[0003] Vehicles are becoming more and more complex in terms of mechanics, pneumatics, hydraulics, electronics, and software. Modern heavy vehicles may include a wide range of different actuators, such as a combustion engine, one or more electric machines, friction brakes, electromagnetic brakes, and power steering devices on one or more steering axes. These physical devices are commonly known as Motion Assist Devices (MSDs) and can be controlled by respective MSD control units, which are often placed in direct connection to the MSD actuators. The local MSD control units are then typically connected to a central vehicle controller, which is configured to perform the entire Vehicle Dynamics Management (VMM) by coordinating the different MSDs to obtain a desired motion by the vehicle, for example in response to control inputs by the driver or control signals generated by some Autonomous Driving (AD) algorithm or Advanced Driver Assistance System (ADAS).

[0004] WO21144065 discloses an example of a hierarchical control system for a large vehicle that includes a VMM function configured to perform force generation and MSD coordination in response to motion requests from a traffic situation management (TSM) layer and send control requests to a motion support device (MSD) control layer. The VMM function optimizes the allocation of MSD control commands to satisfy the motion requests.

[0005] Energy efficiency, component wear, potential component failure, and passenger comfort are becoming increasingly important performance metrics for large vehicles, such as trucks and semi-trailers used in freight transportation. It is therefore desirable to perform MSD coordination taking these metrics into account in addition to satisfying motion requests from higher layer controllers. To this end, improvements in VMM functionality for large vehicles are desired. Summary of the Invention [Problem to be solved by the invention]

[0006] An objective of the present disclosure is to provide an improved vehicle control architecture that enables more fine-grained optimization of MSD coordination in large vehicles, seeking improvements in one or more secondary objectives, such as increased energy efficiency, reduced component wear, reduced likelihood of component-level failures, and / or increased occupant comfort, in addition to the primary objective of controlling vehicle motion in response to motion requests from the driver or AD algorithms. [Means for solving the problem]

[0007] This object is at least partially achieved by an MSD control unit for controlling at least one MSD on a heavy vehicle. The control unit is configured to determine at least one limit operating point of the MSD associated with a performance limit of the MSD and to determine a preferred operating point or range of operating points of the MSD indicating an operating point or range of operating points of the MSD associated with an improvement in a secondary objective function value compared to the limit operating point. The MSD control unit is also configured to send a capability message including the limit operating point of the MSD and the preferred operating point of the MSD to a VMM function.

[0008] Thus, the normal capability reports from the MSD control units are supplemented by a preferred operating point or range of operating points, or at least by data indicating the preferred operating points. This allows the higher layer controller to not only set an operating point within the range of operating points that the MSDs can provide, but also to perform optimization according to a secondary objective function. This feature is particularly suitable for VMM systems that include MSD cooperation capabilities, where multiple MSDs cooperate to obtain some desired vehicle motion. This cooperation can often be performed in many different ways that result in the same vehicle motion, and the availability of preferred operating points of the different MSDs can then be used to select a cooperation solution that meets the vehicle motion requirements and also improves the secondary objective function, which may include energy efficiency, component wear, passenger comfort, likelihood of MSD failure, etc.

[0009] According to some aspects, the capability message includes a timestamp and / or a validity duration indicator, which allows a central VMM controller to use the capability message to determine the validity of the message. An advantage is that expired messages can be detected and discarded.

[0010] The limit operating point may, for example, indicate a peak torque of the electric machine, and the preferred operating point may then indicate a torque value associated with improved energy efficiency of the electric machine compared to the peak torque operating point. Thus, in a vehicle actuator system including more than one electric machine, possibly of different types, MSD coordination may be performed with the secondary objective of increasing energy efficiency, leading to benefits such as increased range, which is of course highly desirable in most heavy duty vehicles.

[0011] The limit operating point may also be the peak torque of the friction brakes and the preferred operating point may relate to a torque value associated with reduced friction brake pad wear as compared to the peak torque operating point, allowing the MSD coordination module to perform MSD coordination with a secondary objective of controlling the vehicle to avoid increased component wear, i.e., not wearing the brakes as fast as they would otherwise.

[0012] The limit operating point may also be selected as the maximum steering angle of the power steering device, and the preferred operating point may be a steering angle range associated with reduced wear on the steering system compared to operation at the maximum steering angle.

[0013] The capability message also optionally includes a vector of operating points with associated quadratic objective function values ​​and / or a function approximation indicating the relationship between the operating points and the quadratic objective function values.

[0014] According to a further aspect, the capability message indicates an estimated inverse tire model, which allows the MSD controller that has information regarding the inverse tire model to share this information with the central VMM controller in an efficient manner.

[0015] In general, the advantage is that capability messages are distributed as hard capabilities with soft additions, allowing backward compatibility in systems that cannot take into account preferred operating point data provided by some MSD controllers, and allowing design freedom and independence between layers in a hierarchical control structure by relying on higher layer controllers to decide how to use the preferred operating point data.

[0016] Also disclosed herein are computer programs, computer readable media, computer program products, and vehicles associated with the above advantages.

[0017] Generally, all terms used in the claims should be interpreted according to their ordinary meaning in the art, unless otherwise specified herein. All references to "a / an / the element, apparatus, component, means, step, etc." should be openly interpreted as referring to at least one example of the element, apparatus, component, means, step, etc., unless otherwise specified. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless otherwise specified. Further features of the present invention and advantages associated with the present invention will become apparent upon review of the appended claims and the following description. Those skilled in the art will understand that different features of the present invention can be combined to create embodiments other than those described below without departing from the scope of the present invention.

[0018] Below follows a more detailed description of embodiments of the invention, cited as examples, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0019] [Figure 1] An example of a large vehicle is shown below. [Diagram 2] FIG. 2 is a diagram illustrating a control device of the exercise support device. [Diagram 3] 1 shows a layered vehicle control function architecture. [Figure 4] 1 illustrates an exemplary first capability function. [Figure 5A] 1 illustrates an example soft capabilities message. [Figure 5B] 1 illustrates an example soft capabilities message. [Figure 6] 3 illustrates an example efficiency map for an electric machine. [Figure 7] 1 is a graph showing an example of an inverse tire model. [Figure 8] 1 shows an example of a fitted model based on measurements. [Figure 9] 1 is a flow chart illustrating a method. [Figure 10] 1 shows a schematic representation of a control unit. [Figure 11] 1 illustrates an exemplary computer program product. [Figure 12A] 13 shows an example of an additional cost function that takes into account capability reports. [Figure 12B] 13 shows an example of an additional cost function that takes into account capability reports. [Figure 12C] 13 shows an example of an additional cost function that takes into account capability reports. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, which show certain aspects of the invention. However, the present invention may be embodied in many different forms and should not be construed as being limited to the embodiments and aspects set forth herein. Rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0021] It should be understood that the invention is not limited to the embodiments described herein and shown in the drawings, but rather, those skilled in the art will recognize that many variations and modifications may be made within the scope of the appended claims.

[0022] 1 illustrates an exemplary vehicle 100 for transporting cargo to which the technology disclosed herein may be advantageously applied. The vehicle 100 includes a tractor or towing vehicle 110 configured to tow a first trailer unit 120 by its fifth wheel in a known manner. The trailer wheels are typically brake wheels, but may also include driven wheels on one or more axles. There may be one or more pairs of total steering wheels on the vehicle 100.

[0023] It will be appreciated that the methods and control units disclosed herein may also be advantageously applied in other types of heavy vehicles such as rigid trucks, trucks with drawbar connections, construction equipment, buses, etc.

[0024] The tractor 110 includes a vehicle unit computer (VUC) 130 for controlling various types of functions, i.e., propulsion, braking, and steering. Some trailer units 120 also include a VUC 140 for controlling various functions of the trailer, such as braking of the trailer wheels, and possibly propulsion and steering of the trailer wheels. It will be understood that the VUCs 130, 140 may be centralized or distributed among several processing circuits. Some of the vehicle control functions may also be performed remotely, for example on a remote server 170 connected to the vehicle 100 via a wireless link 150 and a wireless access network 160.

[0025] One or more sensor devices mounted on the vehicle 100 are configured to provide input data to the VUC. Vision-based sensors such as cameras, wheel speed sensors, radar sensors and lidar sensors, as well as Global Positioning System (GPS) sensors, are commonly used in this context. These sensor devices can be used for vehicle state estimation, i.e., to estimate the current motion and attitude of the vehicle, and also for vehicle environment estimation, i.e., to obtain information about the surrounding environment in which the vehicle 100 is operating.

[0026] The VUC 130 of the tractor 110, and possibly also the VUC 140 of the trailer 120, may be configured to execute vehicle control methods that are organized according to a layered functional architecture in which some functions may be included in a traffic situation management (TSM) domain at a higher layer and some other functions may be included in a vehicle dynamics management (VMM) domain that resides in a lower functional layer.

[0027] 2 shows a schematic of a function 200 for controlling wheels 210 by some exemplary MSDs, here including friction brakes 220 (such as disc or drum brakes), steering means 280 such as a power steering device, and an exemplary propulsion device 250, although it is understood that more than one propulsion device can be used on a single axle. In general, one or more propulsion devices may be used to power the vehicle 100. For example, a central propulsion device may be connected to the wheels of the drive axle via a differential. Separate electric machines may also be connected to some of the wheels of the vehicle. These (optional) separate electric machines allow greater freedom of control of the actuators, since they can be controlled independently of each other.

[0028] Friction brakes 220 and propulsion devices 250 are examples of wheel torque generating devices, sometimes referred to as torque actuators, that may be controlled by one or more motion support device control units 230. Other examples of torque generating motion support devices that may be controlled according to the principles described herein include engine retarders and power steering devices. MSD control unit 230 may be arranged to control one or more actuators. For example, it is not uncommon for MSD control unit 230 to be arranged to control both wheels on an axle.

[0029] The TSM function 270 plans driving maneuvers over a time horizon, such as 10 seconds. This period corresponds, for example, to the time it takes the vehicle 100 to negotiate a curve. Vehicle maneuvers planned and executed by the TSM can be associated with acceleration and curvature profiles that represent the desired vehicle speed and turning for a given maneuver. According to one example, the TSM function 270 receives the desired acceleration profile a from the VMM function 260 and distributes forces to satisfy requests from the TSM in a safe and robust manner. req and curvature profile c reqThe VMM function 260 continuously requests (275) capability information to the TSM function 270 detailing the current capabilities of the vehicle in terms of, for example, forces, maximum speed, and acceleration that can be generated.

[0030] Of course, the acceleration and curvature profiles may be obtained from the driver of the large vehicle via conventional control input devices such as a steering wheel, accelerator pedal, and brake pedal, etc. The sources of said acceleration and curvature profiles are not within the scope of this disclosure and will not be described in greater detail herein.

[0031] The wheel 210 has a longitudinal velocity component v x and the lateral velocity component v y The longitudinal tire force F x and lateral tire force F y Unless otherwise stated, tire forces are defined in the wheel's coordinate system, i.e. longitudinal forces are directed in the plane of rotation of the wheel and lateral tire forces are directed perpendicular to the plane of rotation of the wheel. The rotational speed of the wheel is ω x , the radius is R.

[0032] Referring also to FIG. 3, the VMM function 260 operates in a time range of about 1 second and has an acceleration profile a req and curvature profile c req into control commands 231, 232, 233 for controlling vehicle motion functions actuated by various MSDs 220, 250, 280 of the vehicle 100. The MSDs 220, 250, 280 report capabilities 234, 235, 236 to the VMM function 260, which are then used as constraints for vehicle control, particularly during MSD cooperation.

[0033] The VMM function 260 performs vehicle state or motion estimation 305, i.e., the VMM function 260 continuously determines the current vehicle state s(t) at time t, including the positions, speeds, accelerations, and articulation angles of the various units of the vehicle combination, by monitoring the operation using various sensors 306 located on the vehicle 100, which are often but not necessarily connected to the MSDs 220, 250, 280. The VMM function 260 also optionally performs motion prediction 310, i.e., estimates the future vehicle state s(t+T) at one or more time points t+T in the future. Both motion estimation 305 and motion prediction 310 are commonly known techniques, and several exemplary implementations exist in the literature. These sub-functions are therefore not described in further detail herein.

[0034] The results of the motion estimation 305 and optional motion prediction 310, i.e. the estimated vehicle state s(t) and possibly also the future predicted vehicle state s(t+T), are input to a force generation module 320, which generates the total forces V=[V 1 ,V 2 ] and determine the required acceleration profile a req and curvature profile c req The vehicle 100 is driven in accordance with the above.

[0035] The total required force vector V is input to the MSD coordination module 330, which allocates tire forces and coordinates other MSDs such as steering and suspension. Together the coordinated MSDs then provide the desired lateral and longitudinal forces Fy and Fx, as well as the required moments Mz, on the vehicle units to obtain the desired motion through the vehicle linkage 100.

[0036] The MSD coordination module 330 optimizes the MSD allocation with the primary objective of meeting the total required power, under constraints imposed by the limit operating points of the different MSDs, which are obtained at least in part by the capability data feedback from the MSD controllers. For example, the reported capabilities 234, 235, 236 from the different MSDs may include the estimated maximum torque (positive and / or negative) that can be generated in the current operating conditions, the maximum longitudinal tire force (Fx) that can be generated, the wheel slip limit, the maximum lateral force (Fy) that can be generated, the maximum steering angle, etc. The reported capabilities may also include status signals, such as warning and error messages, that indicate faults in a known manner.

[0037] The capacity data reported from the MSD controllers to the VMM function 260 via interface 265 is often scalar in nature, i.e., uses a single value to indicate the current capacity of the MSD actuators. This reduces the ability of the VMM function 260 to perform MSD co-optimization and optimize its operating points and allocation of MSD setpoints with respect to some secondary objective such as energy efficiency, component wear, probability of failure, and / or passenger comfort. It is an object of the present disclosure to remove this limitation and provide an improved control architecture for heavy vehicle motion management.

[0038] To enable the VMM function 260 to perform optimization with respect to a primary objective function (which often includes satisfying motion demands from the TSM function 270) and also optimize vehicle control based on one or more secondary objective functions, it is proposed herein to feed back capability data indicating a preferred operating point to the various MSD controllers, in addition to the operating limits. Thus, instead of simply feeding back capability limits to the VMM function, the MSD controllers also feed back "soft" data indicating a preferred operating point, or a range of preferred operating points where, for example, energy efficiency is higher than average and / or wear on components is not as great as when operating at the limit points.

[0039] This soft capability data fed back to the VMM function 260 from one or more MSD controllers 230 can be used to dictate preferred operating points for the various actuators. In addition to just indicating the limits (upper and / or lower) of what the MSD can handle, the VMM can now perform more fine-grained optimizations targeting power consumption, component wear, likelihood of failure, etc., in addition to the motion control objectives received as requests from the TSM function 270.

[0040] For example, the VMM function 260 may be configured to optimize an objective function such as:

number

number

number

number

[0041] The soft capability information can be included in known MSD co-optimization routines as a weighting function or in some other manner. For example, further constraints can be added to the above optimization problem formulation, using additional variables (often called slack variables) as well as further cost terms in the objective function.

[0042] It is interesting to note that the MSD controller 230 has the option to send back soft capability data if necessary, supporting this type of functionality. Similarly, the VMM optimization routines are free to ignore the soft capability data. This means that compatibility between the MSD controller and the VMM functionality is maintained even if one layer does not support a soft capability feature.

[0043] The soft capacity information is preferably time-dependent, meaning that the MSD controller can update its capacity depending on the state of the MSD actuator as it changes over time. For example, the temperature of the friction brake may change the preferred operating point. That is, the preferred applied negative torque may be reduced if the friction brake is at a high temperature where the wear of the components is relatively high. The soft capacity of the friction brake may also be generated, for example, from brake pad wear rate data stored locally to the MSD controller or remotely, for example, in the server 170. The soft capacity of the power steering device 280 may be generated based on wear and bias the control requests made to the steering device away from "difficult" steering angles. Thus, the capacity data from the local steering controller indicates the maximum steering angle that can be achieved, while also indicating the preferred steering angle range to extend the life of the steering equipment.

[0044] In summary, disclosed herein is an MSD control unit 230 for controlling at least one MSD 220, 250, 280 on a heavy vehicle 100. The control unit 230 is configured to determine a limit operating point of the MSD 220, 250, 280 that is related to the performance limits of the MSD, and also to determine a preferred operating point of the MSD 220, 250, 280 that, compared to the limit operating point, indicates an operating point of the MSD that is related to an improvement in a secondary objective function value. The secondary objective function may be, for example, an objective function indicative of the energy efficiency of the MSD 220, 250, 280, wear of components of the MSD 220, 250, 280, likelihood of failure, and / or passenger comfort value.

[0045] Feedback of performance data indicative of failure probability is of particular interest in heavy vehicles, which are usually associated with very stringent requirements regarding operational safety. By obtaining information from the MSDs indicative of the failure probability for a given setpoint, the MSD coordination module 330 can control the vehicle to always keep the overall failure probability at an acceptable level. For example, a friction brake device can report a capability indicative of the probability of fade for a given torque, which can be determined, for example, as a function of brake temperature and brake pad wear and / or brake pad aging. An electric machine can also be associated with an increased probability of failure due to overheating when operating near its maximum capacity. These probability values ​​can be pre-tabulated and stored in a memory device of the MSD controller. These values ​​can also be periodically updated, for example, from a remote server 170, which may have access to failure rate statistics from other vehicles.

[0046] FIG. 4 shows a graph 400 that diagrammatically illustrates the secondary objective function values ​​depending on the operating point of an exemplary MSD. This particular MSD has both a low limit operating point and a high limit operating point beyond which it is not possible to operate. Thus, the MSD coordination module 330 is free to allocate any operating point between the limits (which may be, for example, a range of steering angles). However, looking at the secondary objective function values ​​over the span between the limits, it can be seen that a set point approximately in the middle is preferred. The MSD coordination module 330 can now utilize this additional information in the control allocation optimization, if desired, to achieve its primary objective of meeting maneuver demands while outputting a solution associated with an increased secondary objective function value compared to when no such consideration was made in the MSD control allocation.

[0047] Figures 12A-C show some examples of additional cost function components that can be added to the primary objective function of an optimization problem to account for soft capability reports of different MSDs. Figure 12A shows an example where there is a preferred value and an approximately quadratically increasing perceived cost associated with deviation from the preferred value. In Figure 12B, the additional cost is instead zero as long as the operating point is kept within some preferred operating point range, while in Figure 12C, there is an increasing cost associated with exceeding the preferred operating point range.

[0048] According to a first example, the limit operating point may indicate a peak torque of the electric machine, and the preferred operating point may indicate a torque value associated with improved energy efficiency of the electric machine compared to the peak torque operating point. FIG. 6 shows an example efficiency map 600 of an electric machine. Efficiency maps of electric machines are generally known and will not be described in more detail herein. However, it is understood that this efficiency map may be used to determine a soft capability message for transmission from the MSD controller of the electric machine to the VMM function 260. For example, assuming that the electric machine is currently operating at a speed indicated by the dashed line 610, it is clearly preferred to operate at a torque around the value indicated by the solid line 620 rather than operating at a peak torque 630. In this case, the soft capability message may also include, for example, an indication of the obtainable peak torque and an indication that a set point close to the solid line is preferred for improved efficiency levels. The MSD coordination module 330 may then decide to take this additional information into account during optimization or to ignore the additional information as appropriate.

[0049] Related to the first example, it may be desirable to penalize operating the electric machine near its peak torque to avoid thermal overload of the electric machine and / or drive and subsequent overheating of the electric machine and possible reduced life. Considerations such as these may also be incorporated into the capability report.

[0050] According to a second example, the limit operating point is the peak torque of the friction brake and the preferred operating point or range of operating points is a torque value or torque range associated with reduced wear of the friction brake pads compared to the peak torque operating point.

[0051] According to a third example, the limit operating point is a maximum steering angle of the power steering device and the preferred operating point is a steering angle range associated with reduced wear on the steering system compared to operation at the maximum steering angle.

[0052] MSD control unit 230 is further configured to send a capabilities message including the limit operating point of the MSD and the preferred operating point of the MSD to VMM function 260. The capabilities message may simply be formatted as a two or three part message indicating the minimum and / or maximum operating point of the MSD, along with data indicating the preferred operating point, as shown generally by message format 500 in FIG.

[0053] According to some aspects, the capability message includes a timestamp and / or a validity duration indicator, as also shown in Figure 5 A. This information can be used by the VMM function to determine the time window when the capability message is relevant and when received soft capability information has expired and therefore needs to be discarded.

[0054] According to another aspect, the capability message includes a vector of operating points with associated secondary objective function values ​​and / or a function approximation indicating the relationship between the operating points and the secondary objective function values. This type of soft capability message 510 is shown diagrammatically in FIG. 5B, where a vector of sample operating points is matched with the corresponding secondary objective function values. Of course, this type of message enables the MSD coordination module 330 to perform a finer-grained optimization that aims to achieve the primary objective function (satisfying the motion demand by generating the required total force) while the secondary objective function is improved.

[0055] Also disclosed herein are VUCs 130, 140 configured for vehicle motion management of a large vehicle 100. The VUCs 130, 140 receive an acceleration profile a from a traffic situation management (TSM) function. req and / or curvature profile c req , perform vehicle state and / or motion estimation 305, 310 to estimate the current state and / or future state of the large vehicle 100, and perform force generation 320 to drive the vehicle 100 according to the motion request, generating a total force V=[V 1 ,V 2] and coordinate a plurality of motion support devices (MSDs) by an MSD coordination module 330 to generate a set of MSD actuator requests 231, 232, 233. In particular, the MSD coordination module 330 is configured to receive at least one capability message from the MSD control unit 230, the capability message including a limit operating point of the MSD and a preferred operating point of the MSD, and the MSD coordination module 330 is configured to coordinate the plurality of MSDs based on the received at least one capability message.

[0056] According to some further aspects, the VMM function 260 is configured to set various MSD controller behaviors by parameterizing the control functions of the actuators. For example, loop gains, etc. can be changed by the VMM to obtain more responsive actuators at the cost of reduced driver comfort. In this case, the MSD controller may send a capability signal indicating a preferred set point depending on multiple different parameter settings.

[0057] Referring back to FIG. 3 , the output of the MSD coordination module 330 is the classical torque demand T i and steering angle requirement δ i These requests may include: . These requests are transmitted over an interface 265 between the central controller and one or more local MSD controllers. This interface may be based on a Controller Area Network (CAN) bus, or some other network technology, such as an Ethernet link. A problem in many large vehicle architectures is that the interface between the central controller and the local MSD controllers has limited bandwidth, which can result in significant delays in requests transmitted over the interface. This means that the response time of the vehicle actuators to a change in operating conditions, such as a sudden decrease in road friction, may not be fast enough to successfully compensate for the change in operating conditions.

[0058] Longitudinal wheel slip λ x can be defined as follows in accordance with SAE J670 SAE Vehicle Dynamics Standards Committee January 24, 2008:

number

[0059] For a wheel or tire to generate tire force, slip must occur. For small slip values, the relationship between slip and the force generated is approximately linear, and the proportionality constant is often expressed as the tire's slip stiffness. The normal force F acting on the tire of the wheel 210 is z is key to determining several important vehicle characteristics. For example, normal force is the lateral tire force F that can be achieved by the wheel. y To a large extent, this is because, usually, F x ≦μF zwhere μ is the friction coefficient associated with the current road friction conditions. The maximum available lateral force for a given lateral slip can be expressed by the so-called magic formula, as described in "Tyre and vehicle dynamics" by Hans Pacejka, Elsevier Ltd. 2012, ISBN 978-0-08-097016-5. The inverse tire model is a model of wheel behavior that describes the tire forces generated in the longitudinal (rolling direction) and / or lateral (perpendicular to the longitudinal) directions as a function of the wheel slip.

[0060] FIG. 7 is a graph 700 showing an example of achievable tire forces as a function of wheel slip λ, i.e., an example of an inverse tire model, with the notation that the tire force values ​​on the axles are merely example values ​​and should not be construed as limiting the present disclosure. The longitudinal tire force Fx shows a portion 710 that increases approximately linearly for small wheel slips, followed by a portion 720 with a more nonlinear behavior for larger wheel slips. Note that there is a peak 730, beyond which the tire force decreases with wheel slip, i.e., if the wheel speed increases beyond a given wheel speed, the tire force generated decreases. The resulting lateral tire force Fy decreases rapidly even with relatively small longitudinal wheel slips. It is desirable to keep the vehicle running in the linear region 710, where the longitudinal force obtainable in response to the applied brake command is easy to predict and sufficient lateral tire force can be generated as required. A more nonlinear region 720 is found where the wheel slip is larger, e.g., above 0.1. Control of the vehicle in this region can be difficult and is therefore often avoided. It may be interesting for traction in off-road conditions, etc., where a larger slip limit for traction control may be preferable, but not for on-road driving. To ensure driving in this region, a wheel slip limit λ of the order of magnitude of, for example, 0.1 may be used. LIM can be imposed on a given wheel.

[0061] Classic torque control loops for large vehicles, as mentioned above, are typically associated with time constants on the order of 10 ms or so, which may not be fast enough to react to changes in, for example, road friction. To improve vehicle dynamics management, the VMM 260 can use an inverse tire model to instead generate a desired tire force at a wheel. Then, instead of requesting a torque corresponding to the desired tire force, the VMM can convert the desired tire force to an equivalent wheel slip (or, equivalently, wheel speed relative to ground speed) and request this slip instead. The main advantage is that the MSD control device 230 can calculate the torque based on the vehicle speed v x and the wheel rotation speed ω x The advantage of this approach is that it is possible to provide the requested torque at a much higher bandwidth by using a tread pattern to maintain running at the desired wheel slip, because the control loop is now local on the MSD side of the interface 265, avoiding the delay 340 at the interface between the central VMM controller and the local MSD controller. These concepts are explained in WO2021144010A1. Of course, this approach assumes that the inverse tire model is at least approximately known, and furthermore that the vehicle speed v x and the wheel rotation speed ω x 7. This requires that reasonably accurate data regarding the maximum slip capability of the MSD be available to the central VMM control unit 260. Nevertheless, it will be appreciated that the type of soft capability message can be determined based on this type of inverse tire model. For example, the maximum slip capability of the MSD to generate torque can be determined as the peak location 730, and a preferred operating point can be set with a preferred margin to the peak, such as the dashed slip limit 740 at which at least some lateral force can be generated. Also, running below the dashed set point 740 will most likely be associated with a significant reduction in tire wear compared to running at set point 730.

[0062] Referring to the example 700 of FIG. 7, it is now assumed that the inverse tire model is Fx and the vehicle 100 is accelerating (the wheel force request is positive). A tire force of about 6 kN is initially set, corresponding to a wheel slip of about 0.05. Further acceleration is then desired and the tire force is increased to about 9 kN, which corresponds to the peak tire force that can be obtained in this example. If the VMM control unit 260 requests a further increase in tire force, the tire enters the nonlinear region 720 and the wheel speed increases, resulting in a reduction in the tire force generated, which is undesirable in most situations. Notably, this reduction in the tire force generated is also seen as a reduction in the torque generated at the wheel axle, as long as the wheel speed remains at least constant for slowly changing vehicle speeds.

[0063] For a permanent magnet synchronous machine PMSM, the following relationship holds in many cases, at least approximately:

number

[0064] In “Accurate Torque Estimation for Induction Motors by Utilizing Globally Optimized Flux Observers”, 2020 International Symposium on Power Electronics, Electrical Drives, Automation and Motion SPEEDAM, 2020, pp. 219-226, M. Stender, O. Wallscheid and J. Bocker discuss torque estimation for induction motors.

[0065] US8080956B2 provides an example of how the applied torque can actually be estimated.

[0066] Of course, torque applied to an axle can also be measured by a mechanical or electrical torque sensor. A torque sensor, also known as a torque transducer or torque meter, is a device for measuring, and possibly recording, torque in a rotating system, such as the drive axle of the wheels 210. It is relatively easy to measure static torque. Dynamic torque, on the other hand, is not as easy to measure, since it generally requires some effect, either electrical or magnetic, to be transferred from the shaft being measured to the static system. One way to achieve this is to coordinate the shaft or a member attached to the shaft with the magnetic field of a series of permanent magnets. The magnetic properties of these fields vary with the applied torque, and so can be measured using a non-contact sensor. Generally, torque sensors or torque transducers use strain gauges applied to a rotating shaft or axle. This method requires a means to power the strain gauge bridge as well as a means to receive a signal from the rotating shaft. This can be accomplished using slip rings, radio telemetry, or rotary transformers. Newer types of torque transducers add electronics and an A / D converter that coordinate with the rotating shaft. The stator electronics then reads the digital signals and converts them into high level analog output signals.Yet another method of measuring torque is by torsion angle or phase shift measurement, whereby the torsion angle due to an applied torque is measured by using two angular position sensors and measuring the phase angle between them.

[0067] By estimating the torque currently applied by the MSD and correlating the change in applied torque with the change in wheel or axle speed ω, it is assumed that both the applied torque and the controlled wheel speed change much faster than the ground vehicle speed. During propulsion with positive generated torque, if an increase in wheel speed ω results in a decrease in the estimated applied torque, it can be inferred that the peak 730 in the inverse tire model has been passed and that the nonlinear region to the right of the peak has been entered. When this occurs, the MSD controller can send a capability message to the central VMM controller, which can include, for example, a maximum wheel slip that can be supported corresponding to the peak force wheel slip 730, and also a preferred wheel slip value that can be selected a little lower than the peak, for example, set to take into account the tire wear rate. The MSD coordination module 330 in the VMM function 260 can then perform vehicle motion optimization, knowing approximately what the peak wheel slip of a given wheel is and what wheel slip is preferred to avoid premature tire wear. It will be appreciated that the above concept can also be applied during braking, i.e., during the generation of negative torque by one or more torque generating MSDs.

[0068] The MSD control unit 230 optionally controls the target wheel speed ω iand the torque generated by the torque generating MSD 220, 250 based on a sequence of estimated applied torque and corresponding set wheel speeds. In simple terms, this relationship can be just a linear relationship between applied torque and wheel speed, preserving information about the linear region 710 of the current inverse tire model. Polynomial models or other more advanced models can of course also be used. Filtering can be applied to reduce measurement noise. This relationship can be estimated from the wheel speed and estimated applied torque pair, for example by fitting a model curve such as a straight line, or by applying a model-based filter such as a Kalman filter, particle filter, etc., as shown in example 800 of FIG. 8, where the crosses 810 represent the measured pairs of estimated torque and wheel speed, and the dashed line 820 represents the fitted model curve. This fitted model is of course only valid for a given vehicle speed, but the VMM function 260, knowing the vehicle speed, can infer the true inverse tire model from this type of feedback data. According to one example, the control unit 230 is configured to output data indicative of the determined model as soft capability signals 234, 235 to the VMM control unit 260. The VMM control unit 260 may have information related to the vehicle speed and the radius of the wheels 210 and can therefore convert the model into an approximation of the current inverse tire model.

[0069] 9 is a flow chart illustrating a method summarizing at least a portion of the preceding description. The computer-implemented method executed by the MSD control unit 230 for controlling at least one MSD 220, 250, 280 on the heavy vehicle 100 is illustrated. The method includes determining (S1) a limit operating point of the MSD 220, 250, 280 associated with a performance limit of the MSD, determining (S2) a preferred operating point of the MSD 220, 250, 280 indicating an operating point of the MSD associated with an improvement in a quadratic objective function value compared to the limit operating point, and transmitting (S3) a capability message to the VMM function 260 including the limit operating point of the MSD and the preferred operating point of the MSD.

[0070] 10 illustrates components of a control unit such as the VUC 130, 140, in terms of several functional units. The control unit may implement one or more of the above-mentioned functions of the TSM 270, the VMM 260, and / or the MSD control function 230 according to the embodiments described herein. The control unit is configured to perform at least some of the above-mentioned functions for the control of the heavy vehicle 100. For example, the processing circuit 1010 is provided using any combination of one or more suitable central processing units (CPUs), multiprocessors, microcontrollers, digital signal processors (DSPs), etc. capable of executing software instructions stored in a computer program product in the form of a storage medium 1020. The processing circuit 1010 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array (FPGA).

[0071] In particular, the processing circuitry 1010 is configured to cause the control unit 101 to perform a set of operations or steps, such as the methods described in relation to Figure 9. For example, the storage medium 1020 may store a set of operations, and the processing circuitry 1010 may be configured to read the set of operations from the storage medium 1020 and cause the control units 130, 140, 1000 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 1010 is configured to perform the methods disclosed herein.

[0072] Storage medium 1020 may also include persistent storage, which may be any single or combination of, for example, magnetic memory, optical memory, solid-state memory, or even remotely attached memory.

[0073] The control unit 130, 140, 1000 may further comprise an interface 1030 for communicating with at least one external device. The interface 1030 may thus include one or more transmitters and receivers with analog and digital components and an appropriate number of ports for wired or wireless communication.

[0074] The processing circuit 1010 controls the normal operation of the control units 130, 140, 1000, for example, by sending data and control signals to the interface 1030 and the storage medium 1020, by receiving data and reports from the interface 1030, and by retrieving data and instructions from the storage medium 1020. Other components and associated functions of the control nodes are omitted so as not to obscure the ideas presented herein.

[0075] Figure 11 illustrates a computer readable medium 1110 carrying a computer program comprising program code means 1120 for performing the method illustrated in Figure 9 when the program product is executed on a computer. The computer readable medium and the code means together may form a computer program product 1100.

Claims

1. A driving assistance device control unit (230) for controlling at least one driving assistance device (220, 250, 280) on a large vehicle (100), comprising: determining a limit operating point of the driving assistance device (220, 250, 280) related to a performance limit of the driving assistance device; determining a preferred operating point or range of operating points for the driving assistance device (220, 250, 280) indicating an operating point or range of operating points for the driving assistance device associated with an improvement in a quadratic objective function value compared to the limit operating point; sending a capability message to a vehicle dynamics management function (260) including the limit operating point of the driving assistance device and the preferred operating point of the driving assistance device; A control unit (230) configured to:

2. The control unit (230) of claim 1, wherein the secondary objective function indicates energy efficiency of the driving assistance device (220, 250, 280).

3. The control unit (230) of claim 1 or 2, wherein the secondary objective function indicates wear of a component of the driving assistance device (220, 250, 280).

4. The control unit (230) of any one of claims 1 to 3, wherein said secondary objective function indicates an occupant comfort value.

5. The control unit (230) of any one of claims 1 to 4, wherein the secondary objective function indicates a likelihood of failure of the driving assistance device (220, 250, 280).

6. A control unit (230) according to any one of the preceding claims, wherein the capability message includes a timestamp and / or an indication of validity duration.

7. A control unit (230) according to any one of claims 1 to 6, wherein the limit operating point indicates a peak torque of the electric machine and the preferred operating point indicates a torque value associated with improved energy efficiency of the electric machine compared to the peak torque operating point.

8. A control unit (230) according to any one of claims 1 to 6, wherein the limit operating point is a peak torque of a friction brake and the preferred operating point is a torque value associated with reduced friction brake pad wear compared to the peak torque operating point.

9. A control unit (230) according to any one of claims 1 to 6, wherein the limit operating point is a maximum steering angle of a power steering device and the preferred operating point is a steering angle range associated with reduced wear on the power steering device compared to operation at the maximum steering angle.

10. A control unit (230) according to any one of claims 1 to 9, wherein the capability message comprises a vector of operating points with associated quadratic objective function values ​​and / or a function approximation indicating a relationship between operating points and quadratic objective function values.

11. The control unit (230) of any one of claims 1 to 10, wherein the capability message indicates an estimated inverse tire model (700).

12. A vehicle (100) comprising at least one driving assistance device control unit (230) according to any one of the preceding claims.

13. A vehicle unit computer (130, 140) configured for vehicle dynamics management of a large vehicle (100), comprising: Acceleration profile (a ｒｅｑ ) and / or curvature profile (c ｒｅｑ ) from a traffic situation management function; performing vehicle state and / or motion estimation (305, 310) to estimate a current state and / or a future state of the large vehicle (100); Force generation (320) is performed to generate a total force (V = [V １ , V ２ ]) and coordinating the plurality of driving assistance devices by a driving assistance device coordination module (330) to generate a set of driving assistance device actuator requests (231, 232, 233); It is configured as follows: the driving assistance device cooperation module (330) is configured to receive at least one capability message from a driving assistance device control unit (230), the capability message including a limit operating point of the driving assistance device and a preferred operating point of the driving assistance device; The driving assistance device coordination module (330), configured to coordinate the plurality of driving assistance devices based on the received at least one capability message, a vehicle unit computer (130, 140).

14. A vehicle (100) including a vehicle unit computer (130, 140) according to claim 13.

15. 1. A computer-implemented method executed in a driving assistance device control unit (230) for controlling at least one motion assistance device (220, 250, 280) on a large vehicle (100), comprising: Determining a limit operating point of the driving assistance device (220, 250, 280) related to a performance limit of the driving assistance device (S1); determining (S2) a preferred operating point of the driving assistance device (220, 250, 280) that indicates an operating point of the driving assistance device associated with an improvement in a quadratic objective function value compared to the limit operating point; Sending a capability message to a vehicle dynamics management function (260) including the limit operating point of the driving assistance device and the preferred operating point of the driving assistance device (S3); The method comprising:

16. A computer program comprising program code means for performing the steps according to claim 15 when the program is executed on a processing circuit (1010) of a computer or a control unit (130, 140, 1000).

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