Control system and method for controlling an active suspension system of a vehicle, active suspension system and vehicle

Abstract

The invention relates to a control system (300) and method for controlling an active suspension system (104) of a vehicle (100), the control system comprising one or more controllers (301), wherein the control system is configured to: obtain (908) information indicative of relative levels of tractive force between different wheels (FL, FR, RL, RR) of the vehicle; and control (912) the active suspension system to increase a normal force through a wheel (FR) of the vehicle having a relatively high tractive force compared to one or more other wheels (FL, RL, RR) of the vehicle and to decrease a normal force through a wheel (FL) of the vehicle having a relatively low tractive force compared to one or more other wheels (FR, RL, RR) of the vehicle in dependence on the information. The invention also relates to an active suspension system and a vehicle comprising the control system.

Description

Technical Field

[0001] This disclosure relates to varying the wheel-to-ground normal force according to traction. In particular, but not exclusively, this disclosure relates to varying the wheel-to-ground normal force according to traction via an active suspension system of a vehicle. Background Technology

[0002] If the vehicle's wheels are positioned on surfaces offering different coefficients of friction μ, the options for maximizing traction are limited. A limited-slip differential, or locking differential, is a mechanism that prevents or limits differential slippage between the wheels to mitigate traction loss through the contact patch with the wheel having the lowest μ.

[0003] The traction control system can detect wheel slippage and reduce the speed of the slipping wheel by applying braking or reducing torque. Due to the mechanical action within the differential, braking the slipping wheel will cause torque to be transferred to the wheel with greater traction. Summary of the Invention

[0004] The purpose of this invention is to address one or more of the disadvantages associated with the prior art.

[0005] According to one aspect of the invention, a control system for controlling an active suspension system of a vehicle is provided, the control system comprising one or more controllers, wherein the control system is configured to: obtain information indicating the relative traction levels between different wheels of the vehicle; and, based on the information, control the active suspension system to increase the normal force of a wheel passing through the vehicle that has relatively higher traction compared to one or more other wheels of the vehicle, and to decrease the normal force of a wheel passing through the vehicle that has relatively lower traction compared to one or more other wheels of the vehicle, for example, compared to a wheel with relatively higher traction.

[0006] In some examples, the control system is configured to receive an indication of vehicle traction loss and, in response to the indication of traction loss, obtain information indicating the relative traction level.

[0007] In some examples, obtaining information indicating relative traction levels includes: controlling the active suspension system to change the normal force through one or more wheels in a first subgroup; determining traction-related variables at each wheel in the first subgroup of wheels to which a known torque is applied; controlling the active suspension system to change the normal force through one or more wheels in a second subgroup; and determining traction-related variables at each wheel in the second subgroup of wheels to which a known torque is applied, wherein the traction-related variables indicate relative traction levels.

[0008] In some examples, traction-related variables include wheel speed.

[0009] In some examples, the wheels of the first subgroup include a first pair of wheels at the opposite corner on the first diagonal of the vehicle, and the wheels of the second subgroup include a second pair of wheels at the opposite corner on the second diagonal of the vehicle.

[0010] In some examples, the first subgroup is the first wheel at the first corner of the vehicle, and the second subgroup is the second wheel at the second adjacent corner of the vehicle.

[0011] In some examples, the first corner is located at the first lateral side of the vehicle and at the first longitudinal end of the vehicle, and the second corner is located at the second lateral side of the vehicle and at the first longitudinal end of the vehicle.

[0012] In some examples, obtaining information indicating the relative traction level includes:

[0013] The active suspension system is controlled to change the normal force through a third wheel, which is located at a second lateral side and a second longitudinal end of the vehicle; traction-related variables are determined at the third wheel where a known torque is applied; the active suspension system is controlled to change the normal force through a fourth wheel, which is located at a first lateral side and a second longitudinal end; and traction-related variables are determined at the fourth wheel where a known torque is applied, wherein the traction-related variables at the third wheel and the traction-related variables at the fourth wheel indicate relative traction levels.

[0014] In some examples, altering the normal force to obtain information indicating the relative traction level includes: repeatedly pulsating the normal force through the wheels of the first subgroup in a first phase, and repeatedly pulsating the normal force through the wheels of the second subgroup in a second phase.

[0015] In some examples, altering the normal force to obtain information indicating the relative traction level involves repeatedly pulsating the normal force at a rate between approximately 0.25 Hz and approximately 15 Hz.

[0016] In some examples, controlling the active suspension system based on information indicating the relative traction level includes: increasing the normal force of the wheels passing through the opposite corner on the first diagonal of the vehicle, including the wheels with relatively high traction; and decreasing the normal force of the wheels passing through the opposite corner on the second diagonal of the vehicle, including the wheels with relatively low traction.

[0017] In some examples, an increase in normal force includes a steady-state increase in normal force.

[0018] In some examples, the control system is configured to cause the normal force passing through one or more wheels to pulsate repeatedly at a frequency having a first value in the range of about 8 Hz to about 15 Hz and / or a second value in the range of about 0.25 Hz to about 3 Hz.

[0019] In some examples, the active suspension system continues to be controlled based on information indicating the relative traction level until no further indication of vehicle traction loss is received or the indication is below a threshold.

[0020] In some examples, the control system is configured to control the torque source and / or brakes to rotate the vehicle's wheels at different speeds and / or rates of change based on information indicating the relative traction level.

[0021] In some examples, the control system is configured to change the steering angle at one or more steerable wheels based on information indicating the relative traction level.

[0022] In some examples, the control system is configured to receive ground information and, based on that ground information, enable information indicating a relative traction level; enable control of the active suspension system based on the information indicating a relative traction level; and / or determine one or more pulsation characteristics for controlling the active suspension system.

[0023] In some examples, ground information depends on one or more of the following: the vehicle's selected terrain pattern; and information obtained from one or more sensors.

[0024] According to another aspect of the present invention, an active suspension system is provided, the active suspension system including the control system.

[0025] According to another aspect of the invention, a vehicle is provided that includes the control system or the active suspension system.

[0026] According to another aspect of the invention, a method for controlling an active suspension system of a vehicle is provided, the method comprising: obtaining information indicating the relative traction levels between different wheels of the vehicle; and, based on the information, controlling the active suspension system to increase the normal force of a wheel passing through the vehicle that has relatively high traction compared to one or more other wheels of the vehicle, and to decrease the normal force of a wheel passing through the vehicle that has relatively low traction compared to one or more other wheels of the vehicle.

[0027] According to another aspect of the invention, computer software is provided, which is arranged to perform the methods when executed. According to another aspect of the invention, a non-transitory computer-readable medium is provided, comprising computer-readable instructions that, when executed by a processor, cause any one or more of the methods described herein to be performed.

[0028] The one or more controllers may collectively include: at least one electronic processor having an electrical input for receiving information; and at least one electronic memory device electrically connected to the at least one electronic processor and having instructions stored therein; and wherein the at least one electronic processor is configured to access the at least one memory device and execute the instructions thereon to cause the control system to perform the method.

[0029] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples, and alternatives set forth in the foregoing paragraphs, claims, and / or the following description and drawings, and in particular the various features of said aspects, embodiments, examples, and alternatives, may be adopted individually or in any combination falling within the scope of the appended claims. That is, the features of all embodiments and / or any embodiments may be combined in any manner and / or combination falling within the scope of the appended claims, unless such features are incompatible. The applicant reserves the right to amend any originally filed claim or accordingly file any new claim, including the right to modify any originally filed claim to any feature subordinate to and / or incorporated into any other claim, although not initially claimed in this manner. Attached Figure Description

[0030] One or more embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

[0031] Figure 1 The illustration shows an example vehicle and coordinate system;

[0032] Figure 2A , Figure 2B The diagram illustrates the forces acting on the wheels and the road.

[0033] Figure 3 The illustration shows an example control system;

[0034] Figure 4 An example of a non-transitory computer-readable storage medium is illustrated;

[0035] Figure 5 An example of a vehicle's active suspension system is illustrated.

[0036] Figure 6A , Figure 6B , Figure 6C The illustration shows an example of diagonally out-of-phase normal force variation used to estimate relative traction force levels;

[0037] Figure 7A , Figure 7B , Figure 7C , Figure 7D , Figure 7E The illustration shows an example of 90-degree out-of-phase normal force variation used to estimate relative traction force levels;

[0038] Figure 8A , Figure 8B , Figure 8C , Figure 8D The illustration shows an example of increasing the normal force passing through a wheel with relatively high traction; and

[0039] Figure 9 The example method is illustrated. Detailed Implementation

[0040] Figure 1 An example of a vehicle 100 that can implement embodiments of the present invention is illustrated. In some, but not all, examples, vehicle 100 is a passenger vehicle, also referred to as a bus or automobile. In other examples, embodiments of the present invention can be implemented for other applications, such as industrial vehicles or commercial vehicles. Vehicle 100 has a vehicle body 102 (sprung mass) supported by suspension.

[0041] Figure 1 The diagram also illustrates a coordinate system. The x-axis is the longitudinal axis. The rotation of the vehicle body around the x-axis, "R", represents roll. The y-axis is the lateral axis. The rotation of the vehicle body around the y-axis, "P", represents pitch. The z-axis is the vertical axis. The rotation of the vehicle body around the z-axis, "Y", represents yaw.

[0042] Figure 2A The diagram schematically illustrates the wheel and the road surface, as well as the forces acting on the wheel and the road. F T The traction force depends on the torque Tq applied by a torque source such as an internal combustion engine or electric motor, and also on the available traction force. F F is the frictional force. W For the weight of vehicle 100 supported by wheels, if vehicle 100 has one wheel at each corner, then F W This is known as corner weight. F N To be related to weight F W Equal and opposite normal forces. In this paper, the normal force is also referred to as the contact force between the wheel and the ground.

[0043] Figure 2B The y-axis represents the traction force F.T And the x-axis is a curve of the applied torque Tq. Figure 2B The solid line diagram illustrates that, for a given normal force F... N1 traction force F T The torque Tq is increased proportionally until the available traction limit is reached. Above this limit, further increases in torque Tq will provide less additional traction F as the wheels begin to slip. T As torque increases, and consequently wheel slippage rate increases, traction force F... T It will begin to decrease because the dynamic friction force is smaller than the static friction force.

[0044] However, if the normal force increases to F N2 (Dashed line) indicates that the traction limit can be increased. Therefore, if the normal force F during driving... N The available traction can be increased by increasing the proportion of the vehicle weight applied to the wheel, and the resulting increase in available traction can help the vehicle 100 maintain traction or disengage from a jam.

[0045] In at least some embodiments of the present invention, the suspension of the vehicle 100 is an active suspension system that is capable of temporarily reducing the normal force F passing through a specific wheel of the vehicle 100. N Increase the size to increase traction at these wheels. The active suspension system 104 is such a system that can be configured in the control system 300, for example... Figure 3 The control system shown provides energy to the system to change the normal force at the wheels of the vehicle. By increasing the energy to increase the actuator force (the force used to increase the distance between the wheel and the body) at one corner of the vehicle 100 relative to other corners, the weight of the vehicle 100 is balanced and transferred, so that more of the weight of the vehicle 100 is supported by some wheels other than the other wheels. If more weight can be applied to the driven wheels with the highest traction, these wheels will experience a greater normal force F due to the resulting normal force F. N The increase will result in greater available traction.

[0046] Therefore, the weight of vehicle 100 can be considered a kind of "currency" that can be used to manage the normal force applied to each tire at the contact surfaces, where increasing the proportion of the vehicle weight supported by a given wheel will yield the greatest return in terms of traction for the entire vehicle. If the control system 300 can measure the traction μ at each contact surface, the ideal weight change for each wheel can be calculated. For example, information about which contact surface has the highest traction μ can be used to provide an additional normal force to that contact surface, thereby generating greater traction. Similarly, information about which contact surface has the lowest μ can be used to reduce the weight of that contact surface by reducing the normal force through that contact surface, which frees up additional "mass currency" for the contact surface with the highest traction μ.

[0047] The above concept is referred to herein as a "traction detector" and can be used to keep vehicle 100 moving or to help a stuck vehicle 100 get out of a stuck situation without the need for external assistance.

[0048] The active suspension system 104 and the control system 300 will be described first.

[0049] Figure 3 The control system 300 includes a controller 301. In other examples, the control system 300 may include multiple controllers located on and / or outside the vehicle 100. In some examples, the control system 300 or controller 301 may be provided as part of the active suspension system 104.

[0050] Figure 3 The controller 301 includes: at least one processor 304; and at least one memory device 306 electrically connected to the electronic processor 304 and having instructions 308 (e.g., a computer program) stored therein, the at least one memory device 306 and the instructions 308 configured to perform any one or more of the methods described herein via the at least one processor 304. The processor 304 may have an interface 302, such as electrical input / output (I / O) or an electrical input for receiving information and interacting with external components, such as the active suspension system 104.

[0051] Figure 4 The illustration shows a non-transitory computer-readable storage medium 400 including instruction 308 (computer software).

[0052] Figure 5An example implementation of the active suspension system 104 is illustrated. The active suspension system 104 includes a left front active suspension 106 for the left front wheel FL, a right front active suspension 116 for the right front wheel FR, a left rear active suspension 108 for the left rear wheel RL, and a right rear active suspension 118 for the right rear wheel RR. The active suspension for each wheel of the vehicle 100 (e.g., sidewall wheels / corner wheels) can be individually controllable.

[0053] Figure 5 The diagram also illustrates a torque source 103, such as an internal combustion engine or an electric motor, used to drive at least some of the vehicle wheels.

[0054] The active suspension for each corner of vehicle 100 includes an actuator 502. The actuator 502 may be a hydraulic actuator, such as a chamber filled with hydraulic fluid housing a piston. One end of the actuator 502 is coupled to a vehicle wheel, and the other end is coupled to the vehicle body 102. A spring 504 (e.g., a coil spring or a pneumatic spring) may be in a balanced state and may act in parallel with the actuator 502.

[0055] When the vehicle suspension is undisturbed, the piston of the hydraulic actuator 502 is located in a specific neutral position within the chamber. The piston can move in either direction within the chamber, for example, due to road disturbances that compress the actuator 502. The piston can cause fluid to be removed from the chamber and enter a hydraulic circuit (not shown). The fluid exerts a restoring force against the piston's movement. Energy can be added to and / or extracted from the actuator 502 by pumping fluid and / or controlling valves to regulate the fluid pressure on either side of the piston.

[0056] Therefore, the control system 300 can dynamically control the restoring force resisting the displacement piston. This force is equivalent to the spring force of a coil spring resisting displacement. Dynamic control allows the force-displacement relationship to be changed to adapt to the driving scenario. Energy can be added or removed rapidly, for example, within tens of milliseconds. To control the spring force, the control system 300 can output a force request that depends on the sensed wheel travel (displacement / articulation of the wheel to the vehicle body).

[0057] The dynamic damping characteristics of actuator 502 can be modified by controlling the fluid valve at the contraction point, which regulates the rate at which fluid is transferred into and removed from actuator 502 by the movement of the piston.

[0058] Furthermore, energy can be added to or removed from actuator 502 to alter the normal force applied to the tire contact surface associated with actuator 505. This change in force may cause actuator 502 to extend or retract. Figure 5 This allows the distance from the wheels to the vehicle body to vary independently at different ends and / or different corners of the vehicle 100.

[0059] The above example relates to a hydraulic actuator 502, and in other embodiments, the actuator may be an electromagnetic actuator or a pneumatic actuator, etc.

[0060] exist Figure 5 In, but not necessarily in all, examples, spring 504 includes an active spring, such as a pneumatic spring, capable of controlling ride height. Control system 300 can be configured to pump gas (e.g., air) into or out of pneumatic spring 504 to control ride height. The air conditioning function of control system 300 attempts to maintain a set ride height regardless of vehicle load, and achieves this by changing the air volume and thus changing the air pressure.

[0061] Energy can be added to or removed from the pneumatic spring 504 to increase or decrease its volume. Increasing the volume can lift the vehicle body 102 along the z-axis. Figure 5 This allows the distance from the wheel to the vehicle body to be changed independently at different ends and / or different corners of the vehicle 100. Alternatively or alternatively, the spring 504 may include a passive spring (e.g., a coil spring) or may be omitted entirely.

[0062] Control of the active suspension system 104 relies on one or more sensors. For example, wheel travel can be sensed by a wheel-to-body displacement sensor 514 (a sensor based on suspension displacement). The wheel-to-body displacement sensor 514 is positioned somewhere on the active suspension and can sense the position of the wheel along an arc defined by the suspension geometry. An example of the wheel-to-body displacement sensor 514 is a rotary potentiometer attached to a lever, wherein one end of the lever is connected to the vehicle body 102 and the other end is connected to a suspension link.

[0063] In some examples, the control system 300 determines wheel travel and / or its associated derivatives more accurately by fusing information from wheel-to-body displacement sensors 514 with information from wheel hub accelerometers.

[0064] The pressure in the pneumatic spring 504 can be sensed to indicate the weight on the wheel.

[0065] In at least some examples, the control system 300 is configured to control the active suspension system 104 by sending force requests to the active suspension or its lower-level controller. The force request can be an arbitrated force request based on requests from various requesters and information from various sensors.

[0066] Figure 5 The illustration shows additional optional features that can interact with the control system 300 to request influence calculations. These additional optional features include one or more of the following:

[0067] - Wheel speed sensor 512 for each wheel. In the example implementation, wheel speed sensor 512 is part of the anti-lock braking system (ABS).

[0068] - An accelerometer 516 mounted on the hub for each wheel, which is connected to the unsprung mass of the vehicle 100.

[0069] Human-Machine Interface (HMI) 520. The HMI 520 refers to any of the various input devices and input / output devices available to the driver, such as touch screens, displays, hardware switches / sliders / selectors, etc.

[0070] - At least one vehicle body accelerometer 522, said at least one vehicle body accelerometer 522 being coupled to the vehicle body 102 (sprung mass). Specific examples include a 3DOF inertial measurement unit (IMU) or a 6DOF inertial measurement unit (IMU). The unit may include an accelerometer or a set of multi-axis accelerometers.

[0071] - Tire pressure monitoring system (TPMS) 524, which includes a tire pressure monitor for each wheel.

[0072] Figures 6A to 9 The diagram illustrates an example implementation of a traction detector:

[0073] - Figures 6A to 7E The illustration shows an example of an estimation function that determines relative traction levels—for example, which wheel (corner / contact surface) has the greatest grip (traction). The estimation function controls the active suspension system to change the normal force (e.g., pulsation / oscillation) and measures the effect of that change on traction indicators, such as wheel speed (spinning).

[0074] - Figures 8A to 8D The illustration shows an example of an implementation function that increases the normal force of one or more wheels having the highest traction force determined by the estimation function. For reasons explained later, the implementation function may include steady-state suspension deflection and / or may include pulsation / oscillation components.

[0075] - Figure 9 The example control method is illustrated.

[0076] First, the estimation function is described with reference to various implementation methods.

[0077] The first technique for estimating relative traction levels is based on wheel slippage detected by wheel speed sensor 512. If the first wheel rotates at a higher speed than the other wheels, for example, faster than the average wheel speed, then the first wheel may have lower traction after taking into account other variables. These other variables include, for example, the known torque distribution between the wheels and the known different powertrain losses of the different wheels.

[0078] Traction estimation based on slippage can detect which wheels(s) have lower traction, enabling the methods disclosed herein. However, a traction detector would be more effective if one or more wheels with the highest traction were identifiable. Figures 6A to 7E An implementation is provided that, by altering the weight balance of vehicle 100 to obtain information indicating relative traction levels, allows one or more wheels with the highest traction to be identified. This implementation includes:

[0079] - Control the active suspension system 104 to change the normal force through one or more wheels of the first subgroup (e.g., to cause the extension and retraction of the actuators to oscillate).

[0080] - While changing the normal force, determine the traction-related variables (e.g., wheel speed) at each wheel in the first subgroup of wheels where a known torque (e.g., a measured constant torque request or a variable torque request) is applied.

[0081] - Control the active suspension system 104 to alter the normal force passing through one or more wheels of the second subgroup (e.g., to cause oscillations during the extension and retraction of the actuators); and

[0082] - While changing the normal force, determine the traction-related variables (e.g., wheel speed) at each wheel in the second subgroup of wheels where a known torque (e.g., a measured constant torque request or a variable torque request) is applied.

[0083] The control system 300 can then assess the effect of a known change in normal force (a known actuator force request) on wheel speed. If the change in normal force causes the wheel to slip at a different speed or transition between slippage and no slippage (disruption of traction or regain of traction), the wheel speed will change relative to the speeds of other wheels in a manner that indicates the available traction of that wheel.

[0084] It is not necessary to know the exact traction force if the relative traction force levels of different wheels are determinable. For example, the control system 300 can rank the wheel traction force levels between best and worst based on the degree to which wheel speeds are affected. Methods include, but are not limited to, comparing the average wheel speed or the maximum wheel speed of each wheel.

[0085] There are multiple ways to modify the normal force to estimate the relative traction force. These modifications can include:

[0086] - The steady state is reduced by lifting the wheels toward the vehicle body 102;

[0087] - Increase stability by pushing the wheels away from the vehicle body 102; or

[0088] - Oscillates (pulses) between decreasing and increasing, such as Figures 6A to 7E As shown in the figure, it will now be described.

[0089] Figures 6A to 6C The illustration shows a first example of actuator-based traction force estimation. Figure 6A , Figure 6B These are schematic diagrams of the vehicle wheels FL, FR, RL, RR and the vehicle body 102 at different times.

[0090] In this example, actuator 502 is controlled to cause the wheels of the first subgroup (first pair) at opposite corners on the first diagonal of vehicle 100 to pulsate vertically in a first phase, and to cause the wheels of the second subgroup (second pair) at opposite corners on the second diagonal of vehicle 100 to pulsate vertically in a second phase, in which case the second phase is approximately 180 degrees out of phase. Thus, one wheel is lifted / pulled (weight reduction / unloading), while the other wheel is pushed (weight increase / loading).

[0091] Figure 6A The diagram illustrates the state of the wheels at the first moment t1, where the right front wheel FR and the left rear wheel RL are pulled upward as a diagonal pair, while the left front wheel FL and the right rear wheel RR are pushed downward as a diagonal pair.

[0092] Figure 6B The diagram illustrates the state of the wheels at time t2, where the right front wheel FR and the left rear wheel RL are pushed downwards as a diagonal pair, while the left front wheel FL and the right rear wheel RR are pulled upwards as a diagonal pair.

[0093] In some, but not necessarily all, examples, the smoothness of the pattern approximates a sine wave, such as... Figure 6C The amplitude (A) versus time (t) curve is shown in the figure. In other examples, the waveforms are different or are discontinuous pulsation sequences.

[0094] In some examples, the pattern has a predetermined frequency. Figure 6C The diagram shows that one diagonal pair of wheels FR, RL pulses at a first frequency f(FR, RL), and the other diagonal pair of wheels pulses at approximately the same frequency f(FL, RR). However, it should be understood that these frequencies do not necessarily need to match.

[0095] Figure 6C It is also shown that the waveforms are 180 degrees out of phase, so one pair of wheels is under maximum load / load while the other pair is under maximum unload / reduction. It should be understood that although the force is altered by actuator 502, it is still desirable to maintain tire contact with the ground at all corners in many situations. Therefore, the displacement change from wheel to vehicle body can be relatively small, which is advantageous because it tends not to cause uncomfortable disturbances during vehicle movement or damage to the ground surface on which the vehicle travels.

[0096] In the example, the frequency during the estimation period (the first frequency) is at least about 0.25 Hz. This frequency may not exceed about 15 Hz.

[0097] Appropriate oscillation amplitude is another parameter that can be controlled. At least if the vehicle 100 is moving, the frequency and amplitude can be controlled to be outside the range that would cause wheel bounce. Therefore, the wheels maintain continuous contact with the ground.

[0098] The selection of diagonal pairs, together with a 180-degree phase offset, helps to keep the vehicle body stable during estimation, thereby minimizing the roll or pitch of the vehicle body.

[0099] The estimation may include measuring wheel slippage (relative wheel speed) to determine which diagonal pair has the greatest overall traction. The estimation may also include measuring the relative wheel speed within each diagonal pair to identify the wheel with optimal traction. The estimation may identify the wheel or subgroup of wheels with optimal traction.

[0100] This estimation can be repeated for each oscillation / pulse cycle. More than one pulsation increases the confidence level, for example, increasing the confidence level of average wheel slip / average peak wheel slip. The pulsation ends after the desired number of pulsation cycles.

[0101] Figures 6A to 6C An alternative implementation is to push the wheels of the first diagonal pair downwards without pulling the other pair upwards, and then push the other pair of wheels downwards without pushing the first pair upwards. In other words, the estimation is performed sequentially, not simultaneously.

[0102] In another embodiment, the lateral wheels FL and FR at opposite lateral sides of vehicle 100 pulsate sequentially or simultaneously in a 180-degree out-of-phase manner, while the wheels RL and RR at the other longitudinal end of vehicle 100 do not pulsate. In another embodiment, for example, if vehicle 100 is configured for rear-wheel drive, the rear wheels RL and RR pulsate, while the front wheels FL and FR do not pulsate. In another embodiment, vehicle 100 rolls left or right or pitches up or down by changing the normal force at the wheels simultaneously or in an out-of-phase oscillation / pulsation mode. The illustrated diagonal pattern is most advantageous for vehicle body stability.

[0103] Figures 7A to 7E The illustration shows another estimated implementation in which the individual wheels pulsate around the vehicle clockwise or counterclockwise in a universal joint pattern or sequentially.

[0104] exist Figure 7A At time t1, the first wheel FR pulses in the first phase, wherein the first wheel is located at the first lateral side (right side) of the vehicle 100 and at the first longitudinal end (front) of the vehicle 100.

[0105] exist Figure 7B At time t2, the second wheel FL pulses in a second phase that lags behind the first phase, wherein the second wheel is located at the second lateral side (left side) of the vehicle 100 and at the first longitudinal end (front).

[0106] exist Figure 7C At time t3, the third wheel RL pulses in a third phase that lags behind the second phase, wherein the third wheel is located on the second lateral side (left side) and the second longitudinal end (rear) of the vehicle 100.

[0107] exist Figure 7D At time t4, the fourth wheel RR pulses in a fourth phase that lags behind the third phase, wherein the fourth wheel is located at the first lateral side (right side) and at the second longitudinal end (rear).

[0108] like Figure 7E As shown, the first to fourth phases can be approximately 90 degrees behind each other to provide a uniformly rotating variation of the contact surface force around the vehicle. The frequencies f(FR), f(FL), f(RL), and f(RR) can be one or more frequencies that are approximately the same as each other.

[0109] Universal joint motion helps maintain the stability of the vehicle body, ensuring that the vehicle body movement is neither purely roll nor purely pitch.

[0110] In an alternative implementation, the wheels pulse / displace sequentially, rather than simultaneously in out-of-phase manner. That is, the next wheel can pulse / displace after the previous wheel has returned to its normal target position or target normal force.

[0111] The universal joint mode enables wheel slip estimation for each pulsating wheel and obtains the relative traction level.

[0112] Once the estimation is complete, the implementation phase begins, in which the active suspension system 104 alters the weight balance of the vehicle 100 to transfer a larger proportion of the vehicle weight to one or more wheels with the highest traction. (Refer to...) Figures 8A to 8D Examples of this implementation phase are provided. In some, but not necessarily all, examples, the estimation process progresses to... Figures 8A to 8D It will be stopped during the implementation phase.

[0113] First, in an example scenario where no embodiment of the present invention is applied (not shown), wheel 1 (left front wheel FL) and wheel 4 (right rear wheel RR) are on a low μ ground with μ=0.2, while wheel 2 (right front wheel FR) and wheel 3 (left rear wheel RL) are on a high μ ground with μ=1.

[0114] The forces are assumed to be approximately 1000 kg for the vehicle and with the differential fully locked. The total normal force is F. N = 10 kN. Assuming the weight is equal at each corner, the normal force F at each corner is... N For F N = 2.5 kN. Due to the low μ ground surface, the maximum available traction force of wheels FL and RR is F. T最大 = μF N = 0.5 kN. Due to the high μ ground, the maximum available traction force of wheels FR and RL is F. T最大 = μF N = 2.5 kN. Therefore, assuming the differential is fully locked, the total maximum available traction force of all wheels is F. T最大 = 6 kN.

[0115] In this situation, a fully locked differential or limited-slip differential will cause excessive wheel spin at low μ wheel FL and RR. An open differential will result in equal torque through the differential to each wheel, without fully utilizing the maximum available traction. However, as Figure 8A As shown, the control method of this disclosure enables better utilization of the traction force of wheels FR and RL.

[0116] Figure 8AAs shown, the weight distribution of vehicle 100 has been shifted by controlling the active suspension system 104 to increase the normal force passing through the wheels determined to have relatively high traction, while decreasing the normal force passing through the wheels determined to have relatively low traction.

[0117] For example, this can be achieved by actuator 502 pushing one or more wheels with high traction FR, RL away from the vehicle body 102 and pulling one or more wheels with low traction FL, RR toward the vehicle body 102.

[0118] Now, Figure 8A The forces are shown below. The normal forces at the low-μ wheel FL and RR have decreased to F. N = 0.5 kN. Therefore, the maximum available traction force of wheels FR and RR is reduced to F. T最大 = μF N = 0.1 kN. The normal force at points FR and RL of the high-μ wheel increases to F. N = 4.5 kN. Therefore, the maximum available traction force of wheels FR and RL increases to F. T最大 = μF N = 4.5 kN. Therefore, the total maximum available traction force of all wheels is F. T最大 = 9 kN, which is greater than the previous 6 kN.

[0119] If one or more wheels with the highest traction are replaced by the left front wheel FL and the right rear wheel RR, then wheels FL and RR will be pushed downwards and wheels FR and RL will be pulled upwards.

[0120] The wheels in each pair can be pushed / pulled by the same amount or by different amounts proportional to their respective traction levels.

[0121] In this situation, because the wheels are pulled and pushed in diagonal pairs, the vehicle body maintains stability without excessive pitching or rolling.

[0122] In another embodiment, the high-μ wheel is pushed downwards without pulling the low-μ wheel upwards. In another embodiment, the low-μ wheel is pulled upwards without pushing the high-μ wheel downwards. However, the illustrated embodiment, in which the high-μ wheel is pushed downwards while the low-μ wheel is pulled upwards, provides more control.

[0123] Force requests for pushing / pulling may include steady-state deflection and may optionally include additionally causing the force request to oscillate. On some ground surfaces, oscillations resisting the inertia of the vehicle body can provide a normal force F. NA temporary increase to further assist traction. An example of oscillation will be described later.

[0124] In an alternative implementation, only the normal force of one wheel is added, such as the normal force of the right front wheel FR or the left rear wheel RL as illustrated.

[0125] Figure 8B The diagram illustrates a scenario where only the left front wheel (FL) encounters a low-μ surface, while the other wheels (FR, RL, RR) are on a high-μ surface. Figure 8B In the middle, the left front wheel FL is pulled upward. Any or more of the high μ driven wheels can be pushed downward, in which case the right front wheel FR can be pushed downward.

[0126] Figure 8C The illustration depicts a scenario where vehicle 100 experiences μ separation on a road surface with left-right asymmetry, where the left front wheel FL and left rear wheel RL encounter the low μ surface, while the right front wheel FR and right rear wheel RR are on the high μ surface. If using... Figure 8A The method of applying normal force to the right front wheel FR may reduce the contact force on the right rear wheel RR, thus mitigating the resulting improvement in thrust. Therefore, shifting the center of gravity by "tilting" the vehicle 100 to the right would be an improved method to still obtain usable traction.

[0127] therefore, Figure 8C The diagram shows the right wheels FR and RR being pushed and the left wheels FL and RL being pulled. If the low-μ ground is instead located on the right side, the left wheels FL and RL will be pushed and the right wheels FR and RR will be pulled.

[0128] Figure 8B and Figure 8C Vehicle yaw can be caused by differences in traction force on the lateral wheels. In some examples, control system 300 can monitor yaw signals from vehicle accelerometer 522 to determine if the yaw limit has been exceeded. Control system 300 can then adjust force requests based on the reached yaw limit to reduce the difference in normal force (and therefore traction) between the left and right wheels.

[0129] Figure 8D The illustration depicts a different μ-separation scenario where vehicle 100 is located on a road surface with asymmetrical μ, in which the left front wheel FL and right front wheel FR encounter the low μ surface, while the left rear wheel RL and right rear wheel RR are on the high μ surface.

[0130] therefore, Figure 8DAs shown, the rear wheels RL and RR are pushed downwards while the front wheels FL and FR are pulled upwards. The resulting pitch change transfers more weight to the high-μ rear wheels RL and RR.

[0131] Figure 9 This is a flowchart illustrating an example control method 900 for a traction detector implemented by a control system 30.

[0132] Method 900 begins at operation 902, in which method 900 is enabled. Enabling method 900 may optionally require disabling one or more suppression conditions based on one or more of the following:

[0133] - Vehicle braking. For example, method 900 may not be enabled when the brake pedal is depressed and / or when braking exceeds a threshold.

[0134] - Vehicle speed. For example, when vehicle 100 is traveling at a speed faster than a threshold speed, which has a value between approximately 5 m / s and approximately 20 m / s, method 900 may not be enabled.

[0135] - Vehicle stability system intervention and suppression conditions.

[0136] - Enable / disable settings that can be manually configured via HMI 520.

[0137] - Fault signals or suppression signals from the controller of the active suspension system 104, such as those indicating fault conditions or excessive temperature.

[0138] - The following is the ground information.

[0139] The hybrid function associated with the speed-based suppression condition allows the magnitude of the force request to increase as vehicle speed decreases and decrease as vehicle speed increases, thus avoiding obvious bimorphic behavior. The hybrid function can have a threshold speed as an upper limit and a lower limit speed below which method 900 is fully enabled. In the example, the lower limit is 1 to 10 meters per second slower than the upper limit.

[0140] The ground information data block is checked 904 based on an example suppression condition based on ground information. Ground information may include a selected terrain mode and / or information from one or more sensors in data block 910. Terrain modes are defined at the end of the specification. In the example, method 900 may determine whether vehicle 100 is in a first terrain mode or a second terrain mode. If vehicle 100 is in the first terrain mode, method 900 does not proceed. If vehicle 100 is in the second terrain mode, method 900 continues. In one implementation, the first terrain mode is a road mode, and the second terrain mode is an off-road mode.

[0141] At operation 906, a trigger condition is met to begin the estimation phase. In this example, the trigger condition is based on receiving an indication of traction loss from vehicle 100, such as wheel slippage exceeding a threshold or vehicle speed deviating from a speed setpoint. The traction loss may be global or limited to one or more individual wheels.

[0142] Alternatively or concurrently, the triggering condition may require determining the deviation of the vehicle's forward movement from the expected forward movement. Determining the deviation from the expected forward movement may include receiving feedback indicating the expected forward movement. If the vehicle is being manually driven, this feedback may indicate the magnitude and / or rate of change of the driver-requested braking relative to a threshold, and / or the magnitude and / or rate of change of the driver-requested torque relative to a threshold. This is because excessive use of the brakes / accelerator by the driver can indicate dissatisfaction with the current rate of forward movement. If the vehicle is being driven autonomously, this feedback may indicate the deviation of the vehicle speed from the speed setpoint.

[0143] The above example is reactive. In some examples, a pre-emptive check can be performed in addition to or instead of a reactive trigger. Example pre-emptive checks involve evaluating ground information from one or more sensors configured to detect deformable / granular ground, such as radar sensors, lidar sensors, ultrasonic sensors, or visible light cameras.

[0144] In some examples, the triggering of the estimation phase depends on the driver's intention. Triggering conditions may also require indications of anticipated vehicle motion (e.g., a torque request exceeding a threshold and / or an appropriate speed setpoint).

[0145] At operation 908, the estimation phase is performed. In the example implementation, the control system 300 begins with a first approximation based on wheel slippage estimation, and then proceeds as per... Figures 6A to 7E The wheel is pulsed as described to provide additional confidence.

[0146] At operation 908, characteristics (amplitude / frequency) of the pulsation pattern used for the estimation stage are determined. This optional operation is useful if one or more pulsation characteristics are calculated based on contextual information such as sensor information from data block 910.

[0147] In the example, global and local characteristics of the pulsation pattern are determined. The global characteristics govern the common amplitude and frequency targets for all wheels. The local characteristics modify the force request for individual corners to compensate for differences in suspension characteristics.

[0148] When calculating the local features used for each corner, various differences between these corners can be taken into account. The suspension at each corner has a natural frequency, which depends on the stiffness of deformable elements such as actuator 502, springs, and tires, and also on the sprung mass on the wheels, which varies between these corners. While the differences from left to right may be small, there may be differences from front to rear. The rear suspension can have a higher frequency than the front suspension to improve vehicle stability at speeds.

[0149] Therefore, the force request for each corner may need to be a force request frequency that does not necessarily match the inherent frequency of each corner, in order to ensure that the pulsation frequency generated from the perspective of the wheel is the same at different corners of the vehicle 100.

[0150] Therefore, one or more variables can be taken into account when determining the force request for each corner (each actuator 502).

[0151] First, the sprung mass at a given corner can be measured. One method for measuring sprung mass is to measure the steady-state pneumatic / hydraulic pressure in actuator 502 or spring 504, which is a function of weight.

[0152] Secondly, since wheel speed can be affected by ride height, ride height-related parameters can be taken into account. In this example, ride height-related parameters include the requested ride height or the measured ride height (e.g., measured by the wheel-to-vehicle displacement sensor 514).

[0153] Third, tire pressure monitoring data from the TMPS 524 can be used to account for any deflation of the tires and the resulting reduction in their inherent frequency. This is useful when the driver has already released some air from their tires to aid driving. Tire pressure indications for each tire can be received by the control system 300. The tire pressure acquisition function can compensate for differences in tire pressure between different tires to ensure that the resulting waveform is as... Figure 6C or Figure 7E As shown in the image.

[0154] Once the estimation phase is complete, the implementation phase is executed at operation 912. Figures 8A to 8D The description provides examples of how the implementation phase can be performed. Estimation and implementation may not occur simultaneously.

[0155] Optionally, for one or more scenarios, the implementation phase may be omitted. For example, Figures 8C to 8D Scenarios where one or both of the μ components are separated can be excluded because the required displacement results in a perceptible roll or pitch of the vehicle body. Scenarios where only diagonal push / pull can be enabled can be activated. Therefore, the control system 300 can determine whether to execute the implementation phase based on the pattern of relative traction levels.

[0156] If the pushing / pulsing of the wheel includes a pulsating / oscillating component, the required frequency of the force request can be calculated using a technique similar to that described for operation 908.

[0157] In the implementation, steady-state displacement is defined for a ground type or the distribution of μ on different wheels ( Figures 8A to 8D For a vehicle, this may be advantageous, and the oscillation may be better on a harder surface. Different surfaces will act differently when responding to the vehicle's weight forces (e.g., Newtonian surfaces versus non-Newtonian surfaces, or granular surfaces versus solid homogeneous surfaces).

[0158] In some examples, different oscillation frequencies may be suitable for different types of ground or the distribution of μ on different wheels. Different terrain patterns may benefit from different frequencies. For example, a sandy terrain pattern may benefit from multiple superimposed frequencies (0.25 Hz to 3 Hz and 8 Hz to 15 Hz) to help compact loose sand, while another terrain pattern associated with hard ground may only benefit from lower frequencies (0.25 Hz to 3 Hz).

[0159] Therefore, the decision of whether to use steady-state shift, oscillation, or a mixture of both can be made with reference to ground information as described in this article.

[0160] The frequency can be static or can be swept within a certain range. In some examples, a combination of steady-state shift and oscillation is used, wherein the oscillation is configured to further increase the available traction as described, or as jitter / noise to reduce the perception of steady-state shift.

[0161] In some examples employing steady-state displacement, if the wheel is already highly articulated (close to the vehicle body 102 or nearly fully drooping), oscillations (e.g., 8 Hz to 12 Hz) can be used at least on that wheel instead. This ensures that some wheel travel is preserved and the required force demand is not consistently excessive.

[0162] In some examples, oscillations of different frequencies may be appropriate whether vehicle 100 is stuck or not. A stuck vehicle 100 may benefit from higher wheel hopping frequencies (8 Hz to 15 Hz), while lower frequencies (0.25 Hz to 3 Hz) or both are suitable for a moving vehicle. Even with a torque demand (e.g., a torque demand above a threshold), vehicle 100 can also be determined to be stuck when the vehicle speed and / or wheel speed drops below a threshold. Detecting a loss of traction (wheel spin) can provide additional confidence that vehicle 100 is stuck.

[0163] Hybrid functionality can be implemented to provide non-dual-state transitions (e.g., smooth / stepped transitions) between vehicle-locking and non-locking strategies, or between ground-related strategies. Therefore, vehicle occupants are less likely to perceive the policy change. Alternatively, policy changes can be implemented in a delayed manner.

[0164] During the implementation phase, if the vehicle is moving and not stuck, the control system 300 may optionally determine where the front / guide wheels are slipping, and thus preemptively prepare the rear / following wheels for the low-μ ground before the rear wheels reach it. This preparation can transfer more weight to one or more rear wheels. The timing of the preemptive transfer can be based on known vehicle speed and track width. In some examples, the weight transfer includes at least temporarily modifying the frequency of the oscillation pattern. In some examples, the weight transfer includes at least temporarily modifying the steady-state force request for each wheel.

[0165] During the implementation and / or estimation phases, the control system 300 can use information from the vehicle body accelerometer 522 (e.g., an IMU) to ensure that the maximum roll angle threshold and / or maximum pitch angle threshold are not exceeded, and if the threshold is exceeded, terminate or reduce the push / pull displacement. This is helpful when located on a slope.

[0166] Alternatively, the traction detector may not only use the active suspension system 104, but also control one or more other vehicle subsystems to help find traction.

[0167] For example, in operation 914, method 900 controls torque source 103 to rotate the wheels of vehicle 100 at different speeds and / or rates of change based on the results of the estimation phase. An example implementation is to pulsate the wheel rotation and / or slow down the wheel rotation. Slowing down the rotation compacts loose material under the wheel, rather than dispersing it in front of or behind the wheel. Pulsating the wheel between rest and motion helps to find traction because friction is higher at lower slip rates. The wheel speed can be maintained within a target recovery speed range, for example, corresponding to vehicle speeds ≤ 1 km / h or ≤ 5 km / h.

[0168] Operation 914 can be performed on a specific ground surface, such as sand (e.g., sandy terrain pattern) rather than other ground surfaces—for example, depending on the ground information.

[0169] For example, in operation 916, method 900 changes the steering angle at one or more steerable wheels based on information indicating a relative traction level. This applies when vehicle 100 is moving forward. Changing the steering angle may include sawing the steering angle from left to right to help the wheels find traction. The electronic power steering system (EPAS) has associated actuators to perform this operation.

[0170] In some examples, the EPAS can help assess the relative traction levels between steerable wheels (such as FL, FR). The control system can measure the torque of the EPAS's power steering motor when one of the steerable wheels is unloaded, and then measure that torque again when the other steerable wheel is unloaded.

[0171] Operation 916 can be performed on specific terrain surfaces, such as non-grass surfaces—for example, this depends on the terrain information. For example, operation 916 can be disabled in terrain modes optimized for grass (such as Grass-Gravel-Snow mode, GGS), where such sawing of the steering wheels may cause excessive disturbance to the main ground surface, resulting in unwanted path erosion and ultimately reducing grip for subsequent vehicle traffic.

[0172] The implementation phase (operation 912 and optionally 914 and / or 916) may continue until the exit condition is met. An example exit condition is based on the same sensed information as the trigger condition: no longer receiving an indication of traction loss from vehicle 100 or the indication falling below a threshold. As long as vehicle 100 continues forward in the predetermined direction, another estimation phase is not required.

[0173] In some examples, the exit condition may include determining that vehicle 100 has stopped or is being braked. When the exit condition is met, method 900 may loop back to the point before operation 906.

[0174] For the purposes of this disclosure, it should be understood that the one or more controllers described herein may each include a control unit or computing device having one or more electronic processors. A vehicle and / or its systems may include a single control unit or electronic controller, or alternatively, different functions of one or more controllers may be implemented in or hosted in different control units or controllers. A set of instructions may be provided that, when executed, cause the one or more controllers or one or more control units to implement the control techniques (including the described methods) described herein. This set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions may be provided as software to be executed by one or more electronic processors. For example, a first controller may be implemented as software running on one or more electronic processors, and one or more other controllers may also be implemented as software running on one or more electronic processors, optionally the same one or more processors as the first controller. However, it will be understood that other arrangements are also useful, and therefore, this disclosure is not intended to be limited to any particular arrangement. In any case, the aforementioned set of instructions can be embedded in a computer-readable storage medium (e.g., a non-transitory computer-readable storage medium), which may include any mechanism for storing information in a form readable by a machine or electronic processor / computing device. Such mechanisms include, but are not limited to: magnetic storage media (e.g., floppy disks); optical storage media (e.g., CD-ROMs); magneto-optical storage media; read-only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROMs and EEPROMs); flash memory; or electrical media or other types of media for storing such information / instructions.

[0175] Terrain modes are defined. Different terrain modes control one or more vehicle subsystems based on different configuration sets. A terrain mode typically refers to a vehicle mode optimized for driving on a specific driving surface. An example of a terrain mode is an off-road terrain mode configured to optimize vehicle 100 for driving on off-road terrain, such as areas traversing grass, gravel, sand, mud, or even climbing rocks. Another example of a terrain mode is a ground vehicle optimization mode configured to optimize vehicle 100 for driving on low-friction surfaces, such as snow or ice-covered surfaces—whether on or off roads. Vehicle 100 may include a basic road mode and / or a basic ground vehicle optimization mode for regular surfaces, and may include multiple terrain modes for various surfaces and / or terrains.

[0176] Terrain modes and / or detection of specific terrain types can configure one or more ground traction-related settings, such as differential locking settings and / or traction control settings. Additionally or alternatively, other settings can be adjusted, such as: suspension settings; ride height settings; suspension damper settings; throttle response settings; shift point settings; locking / lockable differential settings; vehicle braking settings or traction control settings; torque distribution settings; torque shaping settings; or steering weight settings. These configurations can be preset or reconfigurable.

[0177] Manual user selection may include using a human-machine interface input device 520. In some examples, the terrain mode may be automatically changeable.

[0178] An example HMI 520 is a terrain pattern selector. In some implementations, the terrain pattern selector can be configured to allow a user to provide ground information by selecting one terrain pattern from a plurality of terrain patterns, said plurality of terrain patterns including at least some of the following: sand pattern; climbing pattern; grass-gravel-snow pattern; mud and ruts pattern; general pattern (basic pattern).

[0179] In some implementations, the terrain mode selector may be configured to allow a user to select an "automatic" mode or an "automatic" mode, in which the vehicle 100, for example at the control system 300, determines the most suitable terrain mode at a given time. This is achieved by obtaining ground information from one or more sensors, which includes at least some of the following: rolling resistance; terrain roughness; inclination; wheel slippage; wheel articulation; vehicle yaw. Suitable sensors include IMU / accelerometers 522, 516, wheel speed sensors 512, etc.

[0180] It will be understood that various changes and modifications can be made to the invention without departing from the scope of this application.

[0181] Figure 9 The boxes in the illustrations may represent steps in the method and / or code segments in computer program 308. The illustration of a specific order of boxes does not necessarily imply a required or preferred order for the boxes, and the order and arrangement of the boxes may be changed. Furthermore, some steps may be omitted.

[0182] Although embodiments of the invention have been described with reference to various examples in the preceding paragraphs, it should be understood that modifications may be made to the given examples without departing from the scope of the claimed invention.

[0183] The features described above may be used in combinations other than those explicitly described.

[0184] Although the functions have been described with reference to certain features, those functions can be performed by other features regardless of whether they are described or not.

[0185] Although the features have been described with reference to certain embodiments, those features may exist in other embodiments, whether or not they are described.

[0186] Although efforts have been made in the foregoing description to draw attention to those features of the invention that are considered particularly important, it should be understood that the applicant reserves the right to claim protection for any patentable features or combinations of features referenced herein and / or illustrated in the accompanying drawings, whether or not they have been specifically emphasized.

Claims

1. A control system for controlling an active suspension system (104) of a vehicle (100), the control system comprising one or more controllers, wherein, The control system is configured to: The relative traction level is estimated by obtaining information indicating the relative traction level between different wheels of the vehicle (908), wherein obtaining the information indicating the relative traction level includes: The active suspension system (104) is controlled to change the normal force passing through one or more wheels of the first subgroup; Determine the variables related to traction force at each wheel in the first subgroup of wheels to which a known torque is applied; The active suspension system (104) is controlled to change the normal force passing through one or more wheels of the second subgroup; and Determine the variables related to the traction force at each wheel of the second subgroup of wheels to which a known torque is applied. Wherein, the traction-related variables indicate the relative traction level; and During the implementation phase (912) after estimating the relative traction level, the active suspension system (104) is controlled, based on the information, to increase the normal force of the wheel passing through the vehicle (100) that has relatively high traction compared to one or more other wheels of the vehicle (100), and to decrease the normal force of the wheel passing through the vehicle that has relatively low traction compared to one or more other wheels of the vehicle (100).

2. The control system according to claim 1, configured as follows: Receive an indication of traction loss of the vehicle (100); and In response to the indication of traction loss, information indicating the relative traction level is obtained.

3. The control system according to claim 1 or 2, wherein, The variables related to traction include wheel speed.

4. The control system according to any of the preceding claims, wherein, The wheels of the first subgroup include a first pair of wheels at opposite corners on the first diagonal of the vehicle (100), and the wheels of the second subgroup include a second pair of wheels at opposite corners on the second diagonal of the vehicle (100).

5. The control system according to any one of claims 1 to 3, wherein, The first subgroup is the first wheel at the first corner of the vehicle (100), and the second subgroup is the second wheel at the adjacent second corner of the vehicle (100).

6. The control system according to claim 5, wherein, The first corner is located at the first lateral side of the vehicle and at the first longitudinal end of the vehicle (100), and the second corner is located at the second lateral side of the vehicle (100) and at the first longitudinal end.

7. The control system according to claim 6, wherein, Obtaining the information indicating the relative traction level includes: The active suspension system is controlled to change the normal force through a third wheel located on the second lateral side of the vehicle (100) and at the second longitudinal end. Determine the variables related to the traction force at the third wheel to which a known torque is applied; The active suspension system is controlled to alter the normal force passing through the fourth wheel, wherein the fourth wheel is located at the first lateral side and at the second longitudinal end; and Determine the variables related to the traction force at the fourth wheel where a known torque is applied. The variables related to traction at the third wheel and the variables related to traction at the fourth wheel indicate the relative traction level.

8. The control system according to any one of claims 3 to 7, wherein, Changing the normal force to obtain the information indicating the relative traction level includes: repeatedly pulsating the normal force through the wheels of the first subgroup in a first phase, and repeatedly pulsating the normal force through the wheels of the second subgroup in a second phase.

9. The control system according to any one of claims 3 to 8, wherein, Changing the normal force to obtain the information indicating the relative traction level includes repeatedly pulsating the normal force at a rate between 0.25 Hz and 15 Hz.

10. The control system according to any of the preceding claims, wherein, Controlling the active suspension system based on the information indicating the relative traction level includes increasing the normal force of the wheels passing through the opposite corner on the first diagonal of the vehicle (100), including the wheels with relatively high traction, and decreasing the normal force of the wheels passing through the opposite corner on the second diagonal of the vehicle (100), including the wheels with relatively low traction.

11. The control system according to any of the preceding claims, wherein, An increase in normal force includes a steady-state increase in normal force.

12. An active suspension system, the active suspension system comprising a control system according to any of the preceding claims.

13. A vehicle comprising a control system according to any one of claims 1 to 11 or an active suspension system according to claim 12.

14. A method for controlling an active suspension system of a vehicle (100), the method comprising: The relative traction level (908) is estimated by obtaining information indicating the relative traction level between different wheels of the vehicle (100), wherein obtaining the information indicating the relative traction level (908) includes: The active suspension system (104) is controlled to change the normal force passing through one or more wheels of the first subgroup; Determine the variables related to traction force at each wheel in the first subgroup of wheels to which a known torque is applied; The active suspension system (104) is controlled to change the normal force passing through one or more wheels of the second subgroup; and Determine the variables related to the traction force at each wheel of the second subgroup of wheels to which a known torque is applied. Wherein, the traction-related variables indicate the relative traction level; and During the implementation phase following the estimation of relative traction levels, the active suspension system (104) is controlled, based on the information, to increase the normal force of the wheels of the vehicle (100) that have a relatively high traction level compared to one or more other wheels of the vehicle (100), and to decrease the normal force of the wheels of the vehicle (100) that have a relatively low traction level compared to one or more other wheels of the vehicle (100).

15. A computer program product, which, when executed, is configured to perform the method according to claim 14.

Images