System and method for controlling wheel slip of a vehicle

Abstract

A system and method for controlling wheel slip of a vehicle, in particular, the invention relates to a system for controlling wheel slip of a vehicle and a method executed in a vehicle control unit VCU, wherein the vehicle comprises at least two wheels driven by at least a main actuator through an open differential. The main actuator is controlled to rotate at a speed of a slip λ em of the main actuator. A signed wheel slip limit λ em is determined by adding a configurable value to the slip λ lim of the main actuator, such that λ lim > λ em . The at least two wheels are controlled to rotate at wheel speeds that result in respective wheel slips λ lim , λ l , λ r that are less than the signed wheel slip limit λ l , wherein each of λ r , λ em is a signed value.

Description

Technical Field

[0001] This disclosure relates to a system for controlling wheel slippage of a vehicle. It also relates to a method for controlling wheel slippage of a vehicle, executed in a vehicle control unit. Furthermore, this disclosure relates to a computer program, a computer-readable medium, and a vehicle control unit. Additionally, this disclosure relates to a vehicle including such a system or such a vehicle control unit.

[0002] This invention can be applied to heavy vehicles, such as trucks, buses, and construction equipment. Although the invention will be described in relation to freight transport vehicles such as semi-trailers and trucks, it is not limited to such specific vehicles but can also be used in other vehicles such as passenger cars. Background Technology

[0003] The braking system of heavy vehicles is crucial for their safe operation. It not only limits vehicle speed when necessary but also plays a vital role in maintaining vehicle stability. For example, if the left wheel of a vehicle is traveling on an icy section of the road, resulting in reduced friction and grip, while the corresponding right wheel is traveling on a smooth section, the braking system can be activated to compensate for and counteract the resulting slippage.

[0004] A common method for requesting specific tire forces is to use torque control at the actuator level. However, this method has significant performance limitations. In the event of a safety emergency or excessive slippage, relevant safety functions (traction control, anti-lock braking, etc.) intervene and request torque override to restore control of the slippage. One problem with this is that the communication delay between slip control and the primary actuator control, which are distributed among two different controllers, significantly limits slip control performance.

[0005] A solution to the above approach could be to use a tire model to translate torque requests into wheel slip requests. Therefore, instead of striving to control specific tire forces at the actuator level, a faster control response can be achieved by controlling wheel slip (i.e., the rotational speed of the wheels). However, when the left and right wheels are driven by an electric motor through an open differential, coordinating the slip limits or objectives between actuators is challenging during split-mu scenarios (sometimes also called dual-friction coefficient scenarios). A lack of appropriate selection of actuator slip limits can lead to traction loss and / or actuators "conflicting" with each other. Therefore, improved wheel slip control is desired for vehicles including those with both left and right wheels driven by an electric motor through an open differential. Summary of the Invention

[0006] The object of this invention is to provide a system that mitigates the disadvantages of the prior art. This object is achieved by a system according to a first aspect of this disclosure, and other objects will become apparent hereinafter.

[0007] The present invention is based on the understanding that by setting a signed wheelslip limit and activating an actuator (e.g., a service brake) when the wheel on one side of the vehicle slips beyond the signed wheelslip limit, torque can be effectively transmitted to the wheel on the other side of the vehicle. In this way, the risk of actuators colliding with each other can be effectively reduced. Different aspects and exemplary embodiments will be discussed below.

[0008] According to a first aspect of this disclosure, a system for controlling wheel slippage of a vehicle is provided, wherein the vehicle includes at least two wheels driven by at least one primary actuator (e.g., an electric motor) via an open differential, and separate secondary actuators (e.g., service brakes) for providing additional forces (e.g., frictional forces) to the individual wheels respectively. The system includes a vehicle control unit (VCU) and a motion support device (MSD), wherein the VCU is configured to:

[0009] - Request the main actuator to produce the slip λ of the main actuator. em Rotating at speed,

[0010] - By adjusting the configurable value with the slip λ of the main actuator em The summation determines the signed wheel slip limit λ. lim , such that λ lim >λ em ,and

[0011] - Send control signals to the motion support device MSD to control the at least two wheels of the vehicle to produce a corresponding wheel slip λ. l , λ r The wheel rotates at a certain speed, and the wheel slips λ. l , λ r Less than the marked wheel slip limit λ lim , where λ l , λ r and λ em Each one in the array is a signed numerical value.

[0012] The MSD is configured as follows:

[0013] - Receive the control signal from the VCU

[0014] - Calculate the current corresponding wheel slip λ for each of the at least two wheels. l , λr Or it can be converted into the corresponding wheel slip λ. l , λ r The current corresponding rotational speed, and

[0015] -Based on the received control signal, the current corresponding wheel slip λ l , λ r One of them exceeds the marked wheel slip limit λ lim When this occurs, the MSD is configured to activate the corresponding auxiliary actuator of the wheel with excessive wheel slip in order to transmit torque to another (or more) wheels.

[0016] The at least two wheels may be, for example, a left and a right wheel driven by a main actuator via an open differential. Therefore, for simplicity, the wheel slip discussed in this disclosure has been represented as λ. l and λ r The subscripts "l" and "r" were chosen because their references to "left" and "right" are easily understood. However, it should be understood that the invention is not specifically limited to left and right wheels. The general inventive concept can also be implemented in embodiments where multiple axles or all wheels are driven via an open differential. For example, this general inventive concept can be suitably used in all-wheel drive vehicles where all wheels are driven via an open differential. Therefore, the marked wheel slip limit λ lim This relates to all wheels, not just two. Another example embodiment is multi-axle drive, where the inter-wheel differentials of the first and second drive axles are locked (on each axle, the left and right wheels have the same speed), but the inter-axle differentials are not locked (the average speeds of the first and second drive axles do not necessarily have to be the same). The overall inventive concept can also be implemented for such example embodiments, where the marked wheel slip limit λ lim All wheels are sent to both drive axles.

[0017] Therefore, it should be understood that, although for clarity the discussion in this disclosure focuses on the two wheels, and the text of this disclosure only symbolically includes two λ. l and λ r However, the overall inventive concept applies to two or more wheels, wherein the MSD can be configured to control wheel slippage of each such wheel.

[0018] It should also be understood that, although the main actuator can suitably be an electric motor, such as an electric motor in an electric vehicle (therefore the subscript "em" is already used for the slip λ of the main actuator), em However, other primary actuators are also conceivable. For example, the primary actuator could be an internal combustion engine (e.g., a diesel engine) or a retarder.

[0019] The auxiliary actuator may be a service brake, each brake associated with a corresponding wheel among the at least two wheels, for providing friction to the wheel. However, the auxiliary actuator may be any other suitable actuator that can be activated to transfer torque from a wheel with excessive wheel slippage to one or more other wheels.

[0020] From the above discussion, it should now be clear that various exemplary embodiments are conceivable, one of which may be as follows. According to at least one exemplary embodiment, a system for controlling wheel slippage of a vehicle is provided, wherein the vehicle includes a left wheel and a right wheel driven by at least one motor via an open differential, and a left service brake and a right service brake for providing friction to the left wheel and the right wheel, respectively. The system includes a vehicle control unit (VCU) and a motion support device (MSD).

[0021] The VCU is configured as follows:

[0022] - Request the motor to generate motor slip λ em The motor rotates at a certain speed.

[0023] - By adjusting the configurable value with the motor's slip λ em The summation determines the signed wheel slip limit λ. lim , such that λ lim >λ em ,and

[0024] - Send control signals to the motion support device MSD to control the left and right wheels of the vehicle, causing them to produce corresponding wheel slip λ. l , λ r The wheel rotates at a certain speed, and the wheel slips λ. l , λ r Less than the marked wheel slip limit λ lim , where λ l , λ r and λ em Each one in the array is a signed numerical value.

[0025] The MSD is configured as follows:

[0026] - Receive the control signal from the VCU

[0027] - Calculate the current wheel slip λ of the left wheel. l And the current wheel slip λ of the right wheel r Or it can be converted into wheel slip λ l , λ r The current corresponding rotational speed, and

[0028] -Based on the received control signal, when the current wheel slip λ of the left wheel l And the current wheel slip λ of the right wheel r One of them exceeds the marked wheel slip limit λ lim When this occurs, the MSD is configured to activate the corresponding service brake of the wheel with excessive wheel slip in order to transfer torque to the other wheel.

[0029] For convenience, the discussion below will focus primarily on the scenario where the main actuator is a motor, the auxiliary actuator is a service brake, and the at least two wheels are a left wheel and a right wheel. However, given the above description, it should be understood that the embodiments and features discussed can be readily implemented for other arrangements of the main actuator, auxiliary actuator, and at least two wheels driven by the main actuator.

[0030] For a vehicle with n wheels driven by a main actuator (e.g., an electric motor) via an open differential, wheel slip will result in their average slip being equal to the slip λ of the main actuator. em .

[0031]

[0032] Therefore, for a vehicle with a left and right wheel driven by a main actuator (e.g., an electric motor) through an open differential, wheel slip λ l and λ r This will make their average value equal to the motor's slip λ. em :

[0033]

[0034] Therefore, each individual wheel slips λ l and λ r It can be equal to the slip λ of the motor. em Or one of the wheel slippage (e.g., λ) l It can be higher than λ. em And another (e.g., λ) r It can be lower than λ em As long as the wheel slips λ l and λ r Only within the permissible range of motor slip λ em MSD does not require any corrective intervention. However, when the deviation exceeds the permissible range, i.e., when one of the wheel slips exceeds the marked wheel slip limit λ... limWhen this happens, the MSD will take corrective action to transfer torque to the other wheel. Therefore, the wheel on the low-friction side will be subjected to the service brake to transfer torque to the wheel on the high-friction side. This achieves effective slip control for wheels driven by an open differential and reduces the risk of loss of traction and / or actuators (e.g., brake actuators) "colliding" with each other.

[0035] According to at least one exemplary embodiment, the configurable value is selected as 0 < λ. thr <λ em threshold λ thr This lower limit ensures that wheel slip is greater than λ before slip control is initiated using the relevant service brakes. em This ensures that the associated service brakes do not interfere when the motor performs slip control independently. This upper limit ensures that wheel slippage is below 2λ. em This is the worst-case scenario when one of the wheels (i.e., the wheel on the low-friction side) has no available traction.

[0036] From the above, it can be understood that the marked wheel slip limit λ is defined. lim A simple way is λ lim =λ em +λ thr , where λ thr It is chosen as 0 < λ thr <λ em The threshold for definition. Other methods will be further discussed in this disclosure.

[0037] According to at least one exemplary embodiment, the threshold λ thr It is a fixed value. This provides a way to set the marked wheel slip limit λ. lim A simple method. For example, the fixed value can be determined empirically through testing on a specific vehicle and tire. For example, the fixed value can be set somewhere in the range of 0.02-0.08, such as in the range of 0.03-0.07, or for example, 0.04-0.06. According to at least one exemplary embodiment, the threshold λ thr It can be 0.05.

[0038] According to at least one exemplary embodiment, the VCU is configured to dynamically configure the configurable value appropriately based on the current state of one or more vehicle driving parameters (e.g., the vehicle's current speed). This is advantageous because slip control may become more critical at higher vehicle speeds. For example, at higher vehicle speeds, the configurable value can be set to a lower value (i.e., with respect to the slip λ of the motor). em In comparison, wheel slip λ l , λ rThe configurable value can be set to a smaller allowable deviation at lower vehicle speeds (i.e., a larger allowable deviation). In other words, since the configurable value can be configured dynamically, the signed wheel slip limit λ can also be configured dynamically. lim (by adjusting the configurable value with the motor's slip λ) em (To obtain by addition).

[0039] According to at least one exemplary embodiment, based on the slip λ of the main actuator em The configurable value is obtained from a function. Therefore, when the main actuator is a motor, the configurable value is obtained from the motor's slip λ. em The value is obtained from the function. This is advantageous because it provides a variety of different configuration alternatives. For example, the configurable value can be set to k+xλ. em y Where k, x, and y can be configured according to how people want the slip λ relative to the motor. em The configurable value provides different numbers. In some exemplary embodiments, the marked wheel slip limit λ lim It could be the slip λ of the motor em It is a monotonically increasing function.

[0040] According to at least one exemplary embodiment, the configurable value is the slip λ using the main actuator. em It is obtained from the lookup table as an index. Therefore, according to at least one exemplary embodiment, the slip λ of the motor is used. em The configurable value is obtained from a lookup table. This also provides a simple method for setting the configurable value, as well as many different configuration options. For example, in some exemplary embodiments, the configurable value can result in a signed wheel slip limit λ. lim It is a function that changes gradually.

[0041] As can be understood from the preceding discussion, according to at least one exemplary embodiment, when the vehicle is accelerating or decelerating, the VCU is configured to control the at least two wheels (e.g., the left and right wheels) to produce a result equal to or greater than zero but less than 2λ. em The corresponding wheel slip λ l , λ r The wheel rotates at a certain speed. Specifically, according to at least one exemplary embodiment, when the vehicle accelerates, the maximum positive wheel slip can be selected to be greater than λ. em But less than 2λ em Choosing a fixed slip limit that satisfies this condition will automatically result in good propulsion performance for the system in a split-mu scenario.

[0042] Calculate a suitable threshold λ thr Another input could be the vehicle's steering angle and / or lateral acceleration and / or yaw rate. When the vehicle is turning, it can be expected that one wheel on the axle will turn faster than the other. A threshold λ can be used. thr Set the speed difference appropriately higher than this practically possible "nominal" speed difference. When turning, λ can be reduced. thr This ensures that the tires do not saturate due to excessive longitudinal slippage, and thus maintain sufficient lateral capacity for cornering.

[0043] According to at least one exemplary embodiment, the VCU is configured to request the motor (main actuator) to generate a motor slip λ based on the following equation. em Rotary motor speed ω em Rotate,

[0044]

[0045] Where i g It's the gear ratio, i fd It is the final drive ratio, R is the wheel radius, and v x It is the vehicle speed (in the wheel coordinate system).

[0046] Therefore, λ em Defined between -1 and 1, it quantifies the degree of slippage of the motor relative to the road surface. In other words, if the wheel slips λ... l , λ r If the tires are evenly distributed (e.g., if both the left and right wheels are traveling on a dry surface, and the tires are loaded substantially uniformly and under substantially uniform conditions), then λ em The degree of slippage of each wheel relative to the road surface was quantified. Therefore, in λ l =λ r In the case of λ em The degree of slippage of each wheel relative to the road surface is quantified. Therefore, when the VCU requests the motor to generate the slippage λ of the motor... em motor speed ω em During rotation, it can be viewed as an indirect request for the desired wheel slip. However, according to this disclosure, the actual wheel slip may deviate to some extent from the desired wheel slip, but the permissible deviation is limited, i.e., constrained by the marked wheel slip limit λ. lim Therefore, by combining the demand for motor speed with setting the maximum permissible deviation of wheel slip, good wheel slip control can also be achieved for wheels driven by a motor through an open differential. The VCU can appropriately maintain information about v. x The latest information, and speed sensors, etc., can be used to determine ω. em .

[0047] It is important to note the wheel slip limit λ lim It refers to the signed wheel slip limit, not the absolute limit. Therefore, when applying the signed wheel slip limit λ during propulsion... lim At that time, the wheel slip limit λ with sign lim A maximum permissible positive slip is set. However, during braking, the marked wheel slip limit λ lim A minimum permissible negative slip is set. It should be understood that the slip limits (positive and negative slip) for propulsion and braking can be sent separately to the MSD; that is, the same slip limit signal does not need to be used for both propulsion and braking. However, in other exemplary embodiments, the same slip limit signal can be used for both propulsion and braking.

[0048] Although this disclosure relates to a system for controlling wheel slip, and the system's VCU sends control signals to a motion support device MSD for controlling the at least two wheels of the vehicle to produce a wheel slip limit λ less than the indicated value. lim The corresponding wheel slip λ l , λ r The wheel rotates at a certain speed, but the actual control signal does not necessarily need to include slip limit values ​​(one or more). For example, the VCU can be configured to control the slip limit λ. lim Recalculated as the velocity limit ω lim Therefore, the control signal can alternatively include one or more speed values. The MSD can calculate the rotational speed of the corresponding wheel using a slip equation such as the slip equation, which can be converted into wheel slip:

[0049]

[0050] Where λ is the longitudinal wheel slip, Rω is the wheel rotational speed, R is the wheel radius (in meters), ω is the wheel angular velocity, and v x This refers to the longitudinal velocity of the wheel (in the wheel's coordinate system). Therefore, the final result will be the same regardless of whether the control signal from the VCU includes slip value(s) or velocity value(s), and thus regardless of whether the MSD calculates the current wheel slip or the current rotational speed separately, the control signal controls the wheel to produce a slip limit λ less than the signed wheel slip limit. lim The corresponding wheel slip λ l , λ r The wheels rotate at a certain speed.

[0051] In other exemplary embodiments, the control signal may include a speed offset (where speed offset = actuator speed - v). xThis velocity offset can actually be a function of any number of parameters, such as λ. thr Steering angle, yaw rate, lateral acceleration, vehicle speed, etc.

[0052] According to a second aspect of this disclosure, a method for controlling wheel slippage of a vehicle, executed in a vehicle control unit (VCU), is provided, wherein the vehicle includes at least two wheels (e.g., a left wheel and a right wheel) driven by at least one main actuator (e.g., an electric motor) via an open differential, the method comprising:

[0053] - Request the main actuator to generate the slip λ of the main actuator. em Rotating at speed,

[0054] - By adjusting the configurable value with the slip λ of the main actuator em The summation determines the signed wheel slip limit λ. lim , such that λ lim >λ em ,as well as

[0055] - Control the at least two wheels of the vehicle to produce a wheel slip limit λ less than the marked wheel slip limit. lim The corresponding wheel slip λ l , λ r The wheel rotates at a speed where λ l , λ r and λ em Each one in the table is a signed numerical value.

[0056] The advantages of the various embodiments of the second aspect are largely similar to those of the corresponding embodiments of the first aspect previously discussed. Exemplary embodiments of the method of the second aspect include the following.

[0057] According to at least one exemplary embodiment, the configurable value is selected as 0 < λ. thr <λ em threshold λ thr .

[0058] According to at least one exemplary embodiment, the threshold λ thr It is a fixed value.

[0059] According to at least one exemplary embodiment, the method includes dynamically configuring the configurable value appropriately based on the current state of one or more vehicle driving parameters (e.g., the current speed of the vehicle).

[0060] According to at least one exemplary embodiment, the configurable value is based on the slip λ of the main actuator. em It is obtained from the function.

[0061] According to at least one exemplary embodiment, the configurable value is the slip λ using the main actuator. em It is obtained from the lookup table as an index.

[0062] According to at least one exemplary embodiment, the marked wheel slip limit λ lim =λ em +λ thr , where λ thr It is chosen as 0 < λ thr <λ em The defined threshold.

[0063] According to at least one exemplary embodiment, the method further includes: controlling the at least two wheels to produce an output equal to or greater than zero but less than 2λ when the vehicle accelerates or decelerates. em The corresponding wheel slip λ l , λ r The wheel rotates at a speed of λ. According to at least one exemplary embodiment, when the vehicle accelerates, the maximum positive wheel slip of the wheel can be selected to be greater than λ. em But less than 2λ em .

[0064] According to at least one exemplary embodiment, the method further includes controlling the main actuator based on the following equation to generate a slip λ of the main actuator. em rotational speed ω em Rotation:

[0065]

[0066] Where i g It is the transmission ratio, i fd It is the final drive ratio, R is the wheel radius, and v x It refers to the vehicle's speed.

[0067] According to a third aspect of this disclosure, a computer program is provided that includes program code components for executing the method according to the second aspect (including any embodiments thereof) when the program is run on a computer or on the processing circuitry of a vehicle control unit (VCU). The advantages of the computer program of the third aspect largely correspond to the advantages of the other aspects (including any embodiments thereof).

[0068] According to a fourth aspect of this disclosure, a computer-readable medium carrying a computer program including program code components for executing the method according to the second aspect (including any embodiments thereof) when the program product is run on a computer or on the processing circuitry of a vehicle control unit (VCU). The advantages of the computer-readable medium of the fourth aspect largely correspond to the advantages of the other aspects (including any embodiments thereof).

[0069] According to a fifth aspect of this disclosure, a vehicle control unit (VCU) is provided for controlling wheel slippage of a vehicle, the control unit being configured to perform the method according to the second aspect (including any embodiments thereof). The advantages of the VCU of the fifth aspect largely correspond to the advantages of the other aspects (including any embodiments thereof).

[0070] The VCU may include a microprocessor, microcontroller, programmable digital signal processor, or other programmable device. The VCU may also include, or alternatively include, an application-specific integrated circuit (ASIC), a programmable gate array (FPGA) or programmable array logic (PAI), a programmable logic device, or a digital signal processor. Where the VCU includes a programmable device such as a microprocessor, microcontroller, or programmable digital signal processor as described above, the processor may further include computer-executable code that controls the operation of the programmable device.

[0071] According to a sixth aspect of this disclosure, a vehicle is provided that includes a system according to the first aspect (including any embodiments thereof) or a vehicle control unit (VCU) according to the fifth aspect (including any embodiments thereof). The advantages of the vehicle of the sixth aspect largely correspond to the advantages of the other aspects (including any embodiments thereof).

[0072] Generally, all terms used in the claims should be interpreted according to their ordinary meaning in the technical field, unless otherwise expressly defined herein. Unless otherwise expressly stated, all references to “an element, device, component, apparatus, step, etc.” should be interpreted openly as referring to at least one instance of that element, device, component, apparatus, step, etc. Unless expressly stated otherwise, the steps of any method disclosed herein need not be performed in the exact order disclosed. Further features and advantages of the invention will become apparent when examining the appended claims and the following description. Those skilled in the art will recognize that different features of the invention can be combined to produce embodiments other than those described below without departing from the scope of the invention. Attached Figure Description

[0073] Referring to the accompanying drawings, the following is a more detailed description of embodiments of the present invention cited by way of example.

[0074] In these diagrams:

[0075] Figure 1 A vehicle according to at least one exemplary embodiment of the present invention is shown.

[0076] Figure 2 A system for controlling wheel slippage of a vehicle according to at least one exemplary embodiment of the present invention is shown.

[0077] Figure 3a and Figure 3b It is a graph that schematically illustrates the difference in slip when slip control is not performed versus when slip control is performed according to this disclosure for a propulsion scenario.

[0078] Figure 4a and Figure 4b It is a graph that schematically illustrates the difference in slip when slip control is not performed versus when slip control is performed according to this disclosure for braking scenarios.

[0079] Figure 5 A method according to an exemplary embodiment of the present invention is illustrated schematically.

[0080] Figure 6 A control unit according to at least one exemplary embodiment of the present invention is illustrated schematically.

[0081] Figure 7 A computer program product according to at least one exemplary embodiment of the present invention is illustrated schematically. Detailed Implementation

[0082] The invention will now be described more fully below with reference to the accompanying drawings, in which certain aspects of the invention are illustrated. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Therefore, it should be understood that the invention is not limited to the embodiments described herein and illustrated in the drawings; as above, those skilled in the art will recognize that many modifications and variations can be made within the scope of the appended claims. Throughout the specification, the same reference numerals refer to the same elements.

[0083] Figure 1 A vehicle 100 according to at least one exemplary embodiment of the present invention is shown. Figure 1 The exemplary illustration shows a tractor unit for towing a trailer unit (not shown), which together constitute a semi-trailer vehicle. However, the invention is also applicable to other types of vehicles. For example, the vehicle may be a different type of vehicle used for cargo transportation, such as a truck, or a truck having a dolly unit arranged for towing trailer units, etc. Furthermore, it should be understood that the inventive concept is not limited to heavy vehicles, but can also be implemented in other vehicles, such as passenger cars.

[0084] The vehicle 100 shown is supported on wheels 102, some of which are drive wheels. Although Figure 1The vehicle 100 in the example has only four wheels 102, but the inventive concept is applicable to vehicles with more wheels, such as the different types of vehicles described above.

[0085] Each wheel 102, or at least most of the wheels, is associated with a corresponding wheel brake, service brake. This wheel brake may be, for example, a pneumatic disc brake or a drum brake, but much of this disclosure also applies to regenerative brakes that generate electricity during vehicle deceleration, and to motors capable of slowing wheel rotation upon request. The wheel brakes are controlled by a motion support device (MSD), which can be controlled in various ways, such as... Figure 1 The braking force is applied to at least one wheel 102 of a vehicle such as vehicle 100. Each MSD is communicatively connected to a control unit ( Figure 1 (Not shown in the diagram) to allow the control unit to communicate with the MSD, thereby controlling the vehicle's braking. This control unit may potentially comprise multiple sub-units distributed across the vehicle 100, or it may be a single physical unit. The control unit can, for example, distribute braking force between the wheels to maintain vehicle stability.

[0086] Each drive wheel 102 can be driven by a suitable motor (e.g., electric motor, combined motor / generator, etc.). The motor can drive more than one wheel, for example, operating across an open differential. According to this disclosure, at least one pair of wheels (e.g., left and right wheels) are driven by at least one main actuator via an open differential, and separate auxiliary actuators are configured to provide additional force to said wheels. In the following discussion, as a purely illustrative example, the main actuator is in the form of an electric motor, and the auxiliary actuator is in the form of a service brake configured to provide frictional force to the respective wheel. However, it should be noted that different main actuators (e.g., a diesel engine or a retarder) can be used as electric motors in a corresponding manner, while other auxiliary actuators (e.g., other partial braking devices) can be used in place of service brakes. Furthermore, the invention can be implemented on more than two wheels illustrated below.

[0087] In some exemplary embodiments, the other drive wheels of the vehicle 100 may be propelled by separately associated motors. In either case, the aforementioned control unit may be appropriately communicatively coupled to such motors for distributing propulsion between the wheels. This will now be combined with... Figure 2 The diagram above provides a more detailed discussion of the control unit.

[0088] Figure 2A system 104 for controlling wheel slippage of a vehicle according to at least one exemplary embodiment of the invention is shown. As shown, the vehicle includes a left wheel 102a and a right wheel 102b driven by at least one motor 106 via an open differential 108. A left service brake 112a and a right service brake 112b are mounted to provide friction to the left wheel 102a and the right wheel 102b, respectively. The service brakes 112a and 112b are shown herein as disc brakes; however, as previously mentioned, other types are also conceivable. For example, the braking system may also include one or more additional motors and / or combinations of different brake actuators.

[0089] The system includes a motion support device (MSD) 120 arranged to control wheel braking by activating one or both of service brakes 112a, 112b. The same or different MSDs can be configured to control the operation of motor 106. System 104 also includes a vehicle control unit (VCU) 110, such as a vehicle motion management system. MSD 120 is communicatively coupled to VCU 110. Although MSD 120 and VCU 110 have been illustrated as two functionally separate entities, it should be understood that they can be provided structurally as a single common entity. Therefore, in some exemplary embodiments, MSD 120 and VCU 110 are provided as a single unit. In other exemplary embodiments, MSD 120 and VCU 110 can be structurally separate. In some exemplary embodiments, each actuator may have its own separate MSD (i.e., one MSD for motor 106, another MSD for left service brake 112a, and another MSD for right service brake 112b; or, one MSD for motor 106, while left service brake 112a and right service brake 112b share one MSD). It should also be understood that VCU 110 may be distributed across several structural entities, some of which may be remote from the vehicle, for example, outside the vehicle. For example, some functions (e.g., calculations performed by VCU 110) may be cloud-based, where a portion of VCU 110 may be provided at one or more remote servers, etc.

[0090] VCU 110 is configured to request motor 106 to generate slip λ of motor 106. em The motor rotates at a specific speed. This request can be appropriately sent from VCU 110 to MSD 120. This request to rotate motor 106 at a specific motor speed can be considered an indirect request for a specific rotational speed of wheels 102a, 102b. In other words, the desired slip λ of motor 106 generated by said specific motor speed... emThis can be viewed as an indirect request for a specific desired wheel slip. However, the left wheel 102a and right wheel 102b, driven by motor 106 via open differential 108, may not necessarily achieve the desired wheel slip. Under perfect conditions, each of the left wheel 102a and right wheel 102b may indeed achieve a wheel slip λ, respectively. l and λ r , that λ l and λ r Equal to the slip λ of motor 106 em However, in practice, the conditions typically cause wheel slippage λ. l and λ r One of them will have a slip λ greater than that of motor 106 em One wheel will have a higher value, while the other will have a lower value. This can happen, for example, when one wheel's tire travels on an area of ​​the road with different characteristics (e.g., wetter, slipperier, etc.) compared to the area on which another wheel's tire travels. Therefore, the friction between the wheel and the road may differ, resulting in a higher wheel slip λ. l and λ r They may also differ from each other, and therefore also differ from the slip λ of motor 106. em The values ​​are different. By following the teachings of this disclosure, excessive deviations from the stated values ​​can be prevented or at least offset.

[0091] More specifically, VCU 110 is configured to adjust the configurable value relative to the slip λ of motor 106. em The summation determines the signed wheel slip limit λ. lim , such that λ lim >λ em It should indeed be pointed out that the wheel slip limit λ lim It is a signed value. Therefore, for positive slip (propulsion scenario), i.e., slip value is higher than zero, it corresponds to the slip λ of motor 106. em In comparison, the wheel slip limit λ lim It will have a higher positive value (i.e., further away from zero). However, for negative slip (braking scenario), i.e., slip value below zero, the slip λ of motor 106 will be higher. em In comparison, the wheel slip limit λ lim It will have a smaller negative value (i.e., closer to zero).

[0092] VCU 110 is configured to send control signals to MSD 120 to control the left wheel 102a and right wheel 102b of the vehicle to generate corresponding wheel slip λ. l , λ r The wheel rotates at a certain speed, and the wheel slips λ. l , λ r Less than the marked wheel slip limit λlim . λ l , λ r and λ em are each a signed numerical value. Therefore, the signed wheel slip limit λ lim sets the maximum allowable wheel slip for either of the left wheel 102a and the right wheel 102b.

[0093] In the present disclosure, when wheel slip is discussed, it is intended to refer to longitudinal wheel slip. In this regard, it should be noted that longitudinal direction refers to the radial direction of the wheel in question, in particular the radial direction that is parallel to the road surface and along which the wheel travels under normal conditions. The (longitudinal) wheel slip λ of the wheel (i.e., λ of the left wheel 102a l or λ of the right wheel 102b r ) is dimensionless and can be expressed as:

[0094]

[0095] where R is the wheel radius in meters, ω is the angular velocity of the wheel, v x is the longitudinal velocity of the wheel (in the coordinate system of the wheel). Thus, λ ranges between -1 and 1 and quantifies the extent to which the wheel slips relative to the road surface. During braking, v x > Rω, so the wheel slip is negative. During acceleration, v x < Rω, so the wheel slip is positive. The VCU 110 may maintain / obtain information about v x (in the reference frame of the wheel), while a wheel speed sensor may be used to determine ω. Figure 2 schematically shows that the system 104 may include or be operatively connected to such a wheel speed sensor 122. The wheel speed sensor 122 may be, for example, a Hall effect sensor or other type of wheel speed sensor. The measured rotational speed may be transmitted from the wheel speed sensor 122 to the MSD 120 via a wired or wireless communication link. The speed of the vehicle may be measured by another sensor (not shown) (e.g., a radar sensor, a LiDAR sensor, or a Global Positioning System (GPS) receiver), and the measured speed may be obtained by the VCU 110 and / or the MSD 120. It is also possible to calculate the speed of the vehicle based on the wheel speeds from other un-driven axles on the vehicle. Although the above equation is generally used to determine wheel slip, other definitions may also be used. For example, as previously mentioned in the present disclosure, a speed offset may be an alternative.

[0096] Thus, when the MSD 120 has received a control signal from the VCU 110, it will calculate the current wheel slip λ of the left wheel 102a, for example via the above equation and via the input from the wheel speed sensor 122l And the current wheel slip λ of right wheel 102b r Based on the received control signal, when the current wheel slip λ of the left wheel 102a... l And the current wheel slip λ of right wheel 102b r One of them exceeds the marked wheel slip limit λ lim When this occurs, MSD 120 is configured to activate the corresponding service brakes 112a, 112b of the wheel with excessive wheel slip in order to transfer torque to the other wheel. In this way, wheel slip will be kept substantially within permissible limits; that is, if the limit is exceeded, the wheel slip will be controlled back to the permissible value.

[0097] As described above, VCU 110 is configured to adjust the configurable value relative to the slip λ of motor 106. em The addition determines the marked wheel slip limit λ. lim , such that λ lim >λ em This configurable value can be selected as 0 < λ. thr <λ em threshold λ thr In some exemplary embodiments, the threshold λ thr It can be a fixed value. In other exemplary embodiments, the VCU 110 is configured to dynamically configure this configurable value based appropriately on the current state of one or more vehicle driving parameters (e.g., the current speed of the vehicle). In some exemplary embodiments, the configurable value is the slip λ of the motor 106. em The configurable value is obtained from the function. In some exemplary embodiments, this configurable value is obtained using the slip λ of motor 106. em The value is obtained from the lookup table as an index. In some exemplary embodiments, the signed wheel slip limit λ is used. lim =λ em +λ thr , where λ thr It is chosen as 0 < λ thr <λ em The defined threshold. In some exemplary embodiments, when the vehicle accelerates, the VCU 110 is configured to control the left wheel 102a and the right wheel 102b to produce a corresponding wheel slip λ. l , λ r The wheel rotates at a certain speed, and the wheel slips λ. l , λ r Equal to or greater than zero, but less than 2λ em .

[0098] VCU 110 can be configured to request motor 106 to produce slip λ of motor 106 based on the following equation.em Rotary motor speed ω em Rotation:

[0099]

[0100] Where i g It is the gear ratio, i fd It is the final drive ratio, R is the wheel radius, and v x It refers to the vehicle's speed.

[0101] As mentioned earlier, if the wheel slips λ l , λ r If the tires are evenly distributed (e.g., if both left wheel 102a and right wheel 102b are traveling on a dry surface, and the tires are loaded substantially uniformly and are under substantially uniform conditions), then λ em The degree of slippage of each wheel 102a, 102b relative to the road surface was quantified. Therefore, in λ l =λ r In the case of λ em The degree of slippage of each wheel 102a, 102b relative to the road surface was quantified. Therefore, when VCU 110 requests motor 106 to generate slip λ of motor 106... em motor speed ω em During rotation, it can be viewed as an indirect request for the desired wheel slip. However, as already explained, the actual wheel slip may deviate to some extent from the desired wheel slip. This is achieved by setting the request for motor speed against a maximum permissible deviation of wheel slip (i.e., setting λ). lim Combining these methods can achieve good wheel slip control, which will now be referenced. Figure 3a , Figure 3b , Figure 4a and Figure 4b The illustrative charts in the text will be discussed.

[0102] Figure 3a and Figure 3b It is a graph that schematically illustrates: for a propulsion scenario, when slip control is not performed ( Figure 3a When slip control is performed in accordance with this disclosure ( Figure 3b The slip difference is compared to that of the previous graph. VCU 110 has already requested a slip of 0.1 (λ) in both graphs. em Therefore, MSD 112 will control the speed of motor 106 to achieve a slip target of 0.1 (λ). em ).

[0103] exist Figure 3a The text presents a rather extreme scenario; however, it is useful to consider it for illustrative and explanatory purposes. Figure 3aIn the middle, the left wheel rotates at a constant speed without any slippage, while the right wheel spins on its own. Therefore, in Figure 3a In the middle, the left wheel slips λ l The value is zero, while the right wheel's wheel slippage λ r It is the motor slip λ em It is twice the size of , therefore satisfying the following equation:

[0104]

[0105] However, Figure 3b The corresponding scenario is illustrated, where split-μ compensation provides the slip limit λ according to this disclosure. lim .exist Figure 3b In the diagram, the slip limit λ lim According to equation λ lim =λ em +λ thr Set, where the threshold λ thr It has already been selected as 0.05. However, as explained above, the threshold λ thr This can be chosen differently, even dynamically, and the slip limit λ lim It can be calculated using other methods and different equations, as discussed above.

[0106] and Figure 3a Similarly, in Figure 3b In the middle, the right wheel slips by λ. r It is increasing. However, at a certain point in time, exactly 2 seconds before the curve appears, the wheel slippage λ... r The value exceeds the set slip limit λ. lim Having received a control signal from VCU 110, MSD 120 will now activate the service brake 112b associated with the right wheel 102b, resulting in torque being transferred from the right wheel 102b to the left wheel 102a. This will cause the left wheel to slip λ in the slip control region of the graph, starting just before the two second marks. l It will begin to rise. The equation above remains accurate, that is, the left wheel slips λ. l and right wheel slip λ r The sum equals the slip λ of motor 106 em Twice. In this way, VCU 110 can perform effective slip control by providing slip request to motor 106 and instructing MSD 120 to monitor and act on wheel slip input, so that wheel slip does not deviate excessively from the slip request to motor 106 (as mentioned above, this can be regarded as an indirect request for the desired wheel slip).

[0107] Figure 4a and Figure 4b It is a graph that schematically illustrates: for braking scenarios, when slip control is not performed ( Figure 4a When slip control is performed in accordance with this disclosure ( Figure 4b The slip difference compared to the previous value. VCU 110 has requested a slip target of -0.1 for motor 106 (λ). em MSD 120 reduces the speed of motor 106 to achieve a slip of -0.1 (λ). em ).

[0108] Again, this is an extreme case shown for illustrative purposes. (As from...) Figure 4a As can be seen, the left wheel did not decelerate at all, and the left wheel slipped by λ. l The deceleration of the right wheel is zero, while the deceleration of the right wheel is twice that of the axle; therefore, the wheel slip λ of the right wheel is zero. r It is the slip λ of the motor em Both are twice the value of , and both have negative values.

[0109] like Figure 4b As shown, when the slip limit λ provided according to this disclosure is applied... lim When the dual friction μ is compensated, the left wheel with constant zero slip will exceed the slip limit λ. lim This causes the left wheel to slip, thus transferring torque to the right wheel.

[0110] It should be noted that, in Figure 3b and Figure 4b The signed maximum slip limit λ is applied in both cases. lim This might seem counterintuitive for braking scenarios and could be mistakenly interpreted as the maximum absolute slip limit. That's not the case. The maximum slip limit during braking refers to the minimum braking slip or minimum negative slip, such as... Figure 4b As shown. As previously described, in at least some exemplary embodiments, separate signals can be sent from VCU 110, one for braking and one for propulsion.

[0111] It should also be noted that although VCU 110 requests motor 106 to produce a specific slip λ of the motor... em The motor rotates at a certain speed, but there may be a delay in fulfilling the request, such as... Figure 3a , Figure 3b , Figure 4a and Figure 4b As shown in the figure. The actual current slip λ of the motor. em Changes occur until the desired slip (target slip) is reached. Slip limit λ lim Of course, this is relative to the actual current slip λ of the motor. em As set, and as Figure 3a , Figure 3b , Figure 4a and Figure 4b As shown, therefore λ lim With λ em It changes over time.

[0112] Figure 5 A method 200 according to an exemplary embodiment of the present invention is illustrated schematically. More specifically, method 200 is performed in a vehicle control unit (VCU) for controlling wheel slip of a vehicle, wherein the vehicle includes at least two wheels (e.g., a left wheel and a right wheel) driven by at least one main actuator (e.g., an electric motor) via an open differential, the method comprising:

[0113] - In step S1, the main actuator is requested to generate the slip λ of the main actuator. em The motor rotates at a certain speed.

[0114] - In step S2, by adjusting the configurable value with the slip λ of the main actuator em The summation determines the signed wheel slip limit λ. lim , such that λ lim >λ em ,as well as

[0115] - In step S3, the at least two wheels of the vehicle are controlled to produce a corresponding wheel slip λ. l , λ r The wheel rotates at a certain speed, and the wheel slips λ. l , λ r Less than the marked wheel slip limit λ lim , where λ l , λ r and λ em Each one in the table is a signed numerical value.

[0116] It should be understood that the above steps can be performed in a different order than described above. For example, the marked wheel slip limit λ can be predetermined before the request step (step S1). lim (Step S2). For example, this can be achieved by setting the marked wheel slip limit λ. lim Set as the actual slip λ of the motor em The function or the actual slip λ of the motor em It should be done in a related way. For example, such as Figure 3a , Figure 3b , Figure 4a and Figure 4b As shown, the signed slip limit λ lim It can be set to λ lim =λ em +λ thr, where the threshold λ thr It is predetermined (in the exemplary curve diagram in the attached figure, λ) thr =0.5). Furthermore, it should be understood that it is even conceivable to perform steps S1 and S2 simultaneously.

[0117] Figure 6 A control unit 110 according to at least one exemplary embodiment of the present invention is schematically shown. In particular, Figure 6 Components of a control unit 110 according to the exemplary embodiments discussed herein are shown in terms of multiple functional units. The control unit 110 may be included in a vehicle 100, for example, in the form of a VCU. The processing circuitry 610 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product (e.g., in the form of storage medium 630). The processing circuitry 610 may also be provided as at least one application-specific integrated circuit (ASIC) or field-programmable gate array (FPGA).

[0118] Specifically, the processing circuit 610 is configured to cause the control unit 110 to perform a set of operations or steps, such as combining Figure 5 The methods discussed herein. For example, storage medium 630 may store the set of operations, and processing circuitry 610 may be configured to retrieve the set of operations from storage medium 630 to enable control unit 110 to execute the set of operations. The set of operations may be provided as a set of executable instructions. Thus, processing circuitry 610 is thereby arranged to perform the exemplary methods disclosed herein.

[0119] Storage medium 630 may also include permanent memory, which may be any or a combination of magnetic memory, optical memory, solid-state memory, or even remotely mounted memory.

[0120] The control unit 110 may also include an interface 620 for communicating with at least one external device (e.g., a sensor providing vehicle speed input), for GPS communication, etc. Therefore, the interface 620 may include one or more transmitters and receivers, which include analog and digital components and an appropriate number of ports for wired or wireless communication.

[0121] Processing circuitry 610 controls the general operation of control unit 110, for example, by sending data and control signals to interface 620 and storage medium 630, by receiving and reporting data from interface 620, and by retrieving data and instructions from storage medium 630. Other components and related functions of control unit 110 are omitted to avoid obscuring the concept presented herein.

[0122] Figure 7A computer program product 700 according to at least one exemplary embodiment of the present invention is illustrated schematically. More specifically, Figure 7 A computer-readable medium 710 is shown carrying a computer program including a program code component 720 for execution when the program product is run on a computer. Figure 5 The method is illustrated in the figure. The computer-readable medium 710 and the program code component 720 can together form a computer program product 700.

Claims

1. A system (104) for controlling wheel slippage of a vehicle (100), wherein, The vehicle includes: at least two wheels driven by at least one primary actuator via an open differential (108); and separate secondary actuators for providing additional force to individual wheels, respectively. The system includes a vehicle control unit (VCU) (110) and a motion support device (MSD) (120). The vehicle control unit (VCU) (110) is configured as follows: - Request the main actuator to produce the slip λ of the main actuator. em Rotating at speed, - By adjusting the configurable value with the slip λ of the main actuator em The summation determines the signed wheel slip limit λ. lim , such that λ lim > λ em ,and - Send a control signal to the motion support device MSD (120) to control the at least two wheels of the vehicle to produce a wheel slip limit λ below the marked limit. lim The corresponding wheel slip λ l , λ r The wheel rotates at a speed where λ l , λ r and λ em Each one in the array is a signed numerical value. The motion support device MSD (120) is configured as follows: - Receive the control signal from the vehicle control unit (VCU) (110). - Calculate the current corresponding wheel slip λ for each of the at least two wheels. l , λ r Or it can be converted into the corresponding wheel slip λ l , λ r The current corresponding rotational speed, and - Based on the received control signal, when the current corresponding wheel slip λ l , λ r One of them exceeds the marked wheel slip limit λ lim When the motion support device MSD (120) is configured to activate the corresponding auxiliary actuator of the wheel with excessive wheel slip in order to transmit torque to another or more wheels.

2. The system (104) according to claim 1, wherein, The configurable value is selected as 0 < λ. thr <λ em Threshold λ thr .

3. The system (104) according to claim 2, wherein, The threshold λ thr It is a fixed value.

4. The system (104) according to any one of claims 1-2, wherein, The vehicle control unit (VCU) (110) is configured to dynamically configure the configurable value appropriately based on the current state of one or more vehicle driving parameters.

5. The system (104) according to claim 4, wherein, The vehicle driving parameter is the current speed of the vehicle (100).

6. The system (104) according to any one of claims 1-3, wherein, The configurable value is the slip λ of the main actuator. em It is obtained from the function.

7. The system (104) according to any one of claims 1-3, wherein, The configurable value is the slip λ using the main actuator. em It is obtained from the lookup table as an index.

8. The system (104) according to any one of claims 1-3, wherein, The marked wheel slip limit λ lim = λ em + λ thr , where λ thr It is chosen as 0 < λ thr <λ em The defined threshold.

9. The system (104) according to any one of claims 1-3, wherein, When the vehicle (100) accelerates or decelerates, the vehicle control unit (VCU) (110) is configured to control the at least two wheels to produce an output equal to or greater than zero but less than 2λ. em The corresponding wheel slip λ l , λ r The wheels rotate at a certain speed.

10. The system (104) according to any one of claims 1-3, wherein, The vehicle control unit (VCU) (110) is configured to request the main actuator to generate a slip λ of the main actuator based on the following equation. em rotational speed ω em Rotation: Among them, i g It is the gear ratio, i fd It is the final drive ratio, R is the wheel radius, and v x It refers to the vehicle's speed.

11. The system (104) according to any one of claims 1-3, wherein, The main actuator is an electric motor (106), and / or the auxiliary actuator is a service brake for providing friction to the respective wheels.

12. A method (200) for controlling wheel slip of a vehicle, executed in a vehicle control unit (VCU), wherein, The vehicle includes at least two wheels driven by at least one main actuator via an open differential, and the method includes: - Request (S1) the main actuator to generate the slip λ of the main actuator. em Rotating at speed, - By adjusting the configurable value with the slip λ of the main actuator em The summation determines the signed wheel slip limit λ of (S2). lim , such that λ lim > λ em ,as well as - Control (S3) the at least two wheels of the vehicle to produce a wheel slip limit λ below the marked value. lim The corresponding wheel slip λ l , λ r The wheel rotates at a speed where λ l , λ r and λ em Each of these is a signed numerical value, wherein the control (S3) performed by the vehicle control unit (VCU) (110) includes sending a control signal to the motion support device (MSD) (120).

13. The method according to claim 12, wherein, The configurable value is selected as 0 < λ. thr <λ em threshold λ thr .

14. The method according to claim 13, wherein, The threshold λ thr It is a fixed value.

15. The method according to any one of claims 12-14, further comprising dynamically configuring the configurable value appropriately based on the current state of one or more vehicle driving parameters.

16. The method according to claim 15, wherein, The vehicle driving parameter is the vehicle's current speed.

17. The method according to any one of claims 12-14, wherein, The configurable value is based on the slip λ of the main actuator. em It is obtained from the function.

18. The method according to any one of claims 12-14, wherein, The configurable value is the slip λ using the main actuator. em It is obtained from the lookup table as an index.

19. The method according to any one of claims 12-14, wherein, The marked wheel slip limit λ lim = λ em + λ thr , where λ thr It is chosen as 0 < λ thr <λ em The defined threshold.

20. The method according to any one of claims 12-14, further comprising: - When the vehicle accelerates or decelerates, control the at least two wheels to produce a result equal to or greater than zero but less than 2λ. em The corresponding wheel slip λ l , λ r The wheels rotate at a certain speed.

21. The method according to any one of claims 12-14, further comprising: - The main actuator is controlled based on the following equation to generate the slip λ of the main actuator. em rotational speed ω em Rotation: Where i g It is the gear ratio, i fd It is the final drive ratio, R is the wheel radius, and v x It refers to the vehicle's speed.

22. The method according to any one of claims 12-14, wherein, The main actuator is a motor (106).

23. A computer-readable medium (710) carrying a computer program including a program code component (720) for performing the method of any one of claims 12-22 when the computer program is run on a computer or on the processing circuitry of a vehicle control unit (VCU) (110).

24. A vehicle control unit (VCU) (110) for controlling wheel slip of a vehicle (100), the vehicle control unit being configured to perform the method according to any one of claims 12-22.

25. A vehicle (100) comprising a system (104) according to any one of claims 1-11 or a vehicle control unit (VCU) (110) according to claim 24.

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