Control unit and method for controlling wheels on a vehicle

Abstract

The invention relates to a control unit and method for controlling a wheel on a vehicle. A control unit for controlling a torque applied to a vehicle wheel provided with a tire is disclosed, wherein the control unit comprises or is operatively connected to a data storage device having a stored tire model for the tire, wherein in the tire model a longitudinal tire force is represented at least as a function of a longitudinal wheel slip, which depends on a rotational speed of the wheel and a velocity of the vehicle. The control unit is configured to correct said function based on tire parameter inputs, and to convert a wheel torque request into a wheel rotational speed request based on the corrected function, and to send the wheel rotational speed request to an actuator to provide a rotational speed of the wheel corresponding to said wheel rotational speed request. The invention also relates to a method and a kit.

Description

Technical Field

[0001] This disclosure relates to a control unit for controlling the torque applied to one or more wheels of a vehicle. This disclosure also relates to a vehicle including such a control unit. Furthermore, this disclosure relates to a method for controlling the torque applied to one or more wheels of a vehicle. Additionally, this disclosure relates to a computer program, a computer-readable medium, and a kit.

[0002] This invention can be applied to heavy vehicles, such as trucks, buses, and construction equipment. Although the invention will be described with respect to freight transport vehicles such as semi-trailers and trucks, the invention is not limited to such specific vehicles, but can also be applied to other vehicles such as 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 non-slip 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 overrun to restore control of the slippage. The problem with this is that, since the primary control of the actuator and slip control are typically assigned to two different controllers, the communication delays between them significantly limit slip control performance. Therefore, there is room for improvement in controlling the torque applied to the vehicle wheels. Summary of the Invention

[0005] The objective of this invention is to provide a control unit and method that mitigate the disadvantages of the prior art. This objective is achieved through the control unit and method defined below.

[0006] The concept of this invention is based on the understanding that delay problems can be avoided by providing torque control at the same vehicle subsystem as slip control. Such a subsystem has a relatively short response time compared to vehicle control units that conventionally send torque requests. More specifically, the inventors have recognized that by using a tire model in which the longitudinal tire force is a function of at least the longitudinal wheel slip, the slip control subsystem can be used to provide slip requests corresponding to the desired longitudinal slip force. In particular, the inventors have recognized that, in addition to the advantage of providing a fast response time, in order to make such control accurate, the tire model should be able to be corrected based on one or more parameters affecting tire slip stiffness. Thus, in general, accurate and rapid control of the wheels can be achieved by adapting the force / slip-based tire model to the current state of the tire or the current driving conditions. Different aspects and illustrative embodiments will be discussed below.

[0007] According to a first aspect of this disclosure, a control unit is provided for controlling the wheels of a vehicle equipped with tires, wherein the control unit includes or is operatively connected to a data storage device having a stored tire model for the tires, wherein in the tire model, longitudinal tire force is at least expressed as a function of longitudinal wheel slip, which depends on the rotational speed of the wheels and the speed of the vehicle.

[0008] The control unit is configured to:

[0009] - Receive at least one tire parameter input, the tire parameter input including measured values ​​of at least one parameter affecting the longitudinal slip stiffness of the tire.

[0010] - The function in the stored tire model is corrected based on the received tire parameter input.

[0011] - Obtain or generate a wheel torque request.

[0012] - Based on the corrected function, the obtained or generated wheel torque request is converted into a wheel speed request, and

[0013] - The wheel speed request is sent to the actuator to provide the wheel speed corresponding to the wheel speed request.

[0014] Therefore, by updating the tire model based on parameters affecting the longitudinal slip stiffness of the tire and controlling the wheel speed based on the updated tire model, fast and accurate slip control can be achieved.

[0015] The control unit can be appropriately located in autonomous vehicles or driver-operated vehicles.

[0016] The data storage device can be an in-vehicle data storage device available within the vehicle or an external data storage device, such as a cloud-based data storage device. In some illustrative embodiments, the contents of the data storage device can be downloaded to an in-vehicle processor (e.g., part of a control unit), where the tire model can be stored and updated on-vehicle.

[0017] It should be understood that while a tire model in its most basic form may simply be a longitudinal tire force expressed as a function of longitudinal wheel slip, in at least some illustrative embodiments, the tire model may also include other variables. For example, the tire model may also include other inputs such as lateral wheel slip, vertical forces on the tire, etc.

[0018] Longitudinal wheel slip can be either positive or negative. For example, during acceleration, positive propulsive slip is always obtained, meaning the product of the wheel speed and its radius is greater than the vehicle's speed in the wheel direction. During braking, negative slip is obtained, meaning the product of the wheel speed and its radius is less than the vehicle's speed in the wheel direction.

[0019] According to at least one illustrative embodiment, when converting the wheel torque request into the wheel speed request, the control unit is configured to calculate the slip request based on a corrected function and convert the slip request into the wheel speed request using the following slip formula:

[0020]

[0021] 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 Let be the longitudinal velocity of the wheel (in the wheel's coordinate system). Therefore, the requested wheel speed can be conveniently obtained from the formula and the function of the tire model.

[0022] Therefore, λ lies between -1 and 1, quantifying the degree of wheel slippage relative to the road surface. The control unit can appropriately maintain a certain level of λ. x The latest information (in the wheel's reference frame) and wheel speed sensors, etc., can be used to determine ω.

[0023] The longitudinal slip stiffness of a tire can be expressed as the gradient of a graph of the longitudinal tire force as a function of longitudinal wheel slip at any given point, specifically the gradient starting from zero force. Therefore, a larger longitudinal slip stiffness produces a steeper gradient starting from zero force. Some parameters, such as tire age and tire wear, increase longitudinal slip stiffness, while others decrease it.

[0024] Tire parameter inputs can be received by the control unit in various ways. For example, one or more sensors can be provided to measure and transmit values ​​of certain parameters (such as temperature, inflation pressure, normal load, etc.). Inputs related to parameters such as tire age and tire wear can be provided through counters, which accumulate values ​​(such as via clocks / timers, driving recorders, etc.). Some parameter values ​​can also be manually entered by operators such as vehicle drivers or mechanics.

[0025] As can be seen from the above, according to at least one illustrative embodiment, the at least one parameter can be selected from the group consisting of the following parameters:

[0026] The age of the tires,

[0027] Ambient temperature,

[0028] Tire inflation pressure,

[0029] Normal load on the tire, and

[0030] Tire wear, which is appropriately approximated as the distance the tire has traveled.

[0031] It should be understood that any combination of one or more of the above parameters is possible and is considered to be explicitly disclosed herein.

[0032] Therefore, it should be understood that one or more parameters can be used to correct the functions in the stored tire model. For example, the tire model can be corrected on demand, such as when a wheel torque request has been obtained or generated. However, in other illustrative embodiments, the tire model can be updated continuously or at specific intervals. For example, the tire model can be corrected at different intervals depending on which one or more parameters are being used for the correction. For example, correction based on tire age can be performed less frequently than, for example, correction based on ambient temperature, because ambient temperature can change rapidly throughout the day and also depends on driving conditions.

[0033] According to at least one illustrative embodiment, the control unit is configured to correct the function in a stored tire model by applying a slip stiffness correction factor to the function, the slip stiffness correction factor varying with respect to the parameters. Some slip stiffness correction factors may increase with increasing values ​​of the corresponding associated parameters (such as tire age and tire wear / mileage). Other slip stiffness correction factors may decrease with increasing values ​​of the corresponding associated parameters (such as ambient temperature, inflation pressure, normal load). Correction factor relationships can be appropriately established offline by identifying the properties of the tire under different conditions. Therefore, correction factors can be experimentally determined for any given brand and / or model of tire. For example, parameters can be precisely controlled using an indoor flat-ground tire testing device. Parameter investigations typically include at least three values ​​covering an assumed operating range for a particular parameter. If a linear effect is expected, two measurement points may be sufficient.

[0034] In at least some illustrative embodiments, changes in the correction factors may be represented in a lookup table or by using a general function in practical implementations. Therefore, it should be understood that the functions of the tire model can be updated online based on one or more correction factors during vehicle operation.

[0035] According to at least one illustrative embodiment, the control unit is configured to receive a plurality of different tire parameter inputs, each tire parameter input including a measured value of a corresponding parameter among a plurality of parameters affecting the longitudinal slip stiffness of the tire. The control unit is configured to correct the function in a stored tire model by applying a combined correction factor to the function, the combined correction factor being a function of a plurality of slip stiffness correction factors, wherein each slip stiffness correction factor varies relative to a corresponding parameter among the plurality of parameters. By considering several parameters, a more accurate correction of the function in the tire model can be obtained, thus achieving even more accurate slip control.

[0036] In some illustrative embodiments, once all correction factors have been determined, these correction factors can be combined to estimate the actual slip stiffness C of the tire. act ,For example:

[0037] C act =C nom *c x1 *c x2 *c x3 ...*c xk

[0038] Among them, C nom It is the nominal value, c x1 c x2 c x3 ...c xkThese are k correction factors for different corresponding parameters / variables. Correction factor c x1 c x2 c x3 ...c xk It can be appropriately normalized, where a value of 1 will represent the nominal case.

[0039] Linear or nonlinear functions can be appropriately used to approximate changes in tire properties as functions with different parameters.

[0040] For example, the function that can be used in a tire model for the normal load on a tire is:

[0041] c Fz =1+c1(F z -F z0 c1 < 0

[0042] Among them, c Fz This is the slip stiffness correction for the normal load, where c1 is the nonlinear factor of stiffness with respect to the normal load, and F z and F z0 These are the actual and rated normal loads, respectively.

[0043] In some illustrative embodiments, a general nonlinear function that saturates at both ends far from the nominal reference point can be used, such as:

[0044] c x =1-tanh k x (x act -x0), 0 < k x <1

[0045] Among them, c x It is the slip stiffness correction for variable x, k x It is the sensitivity factor of stiffness to the variable x, x act x0 and x0 are the actual value and nominal value of variable x, respectively.

[0046] In some illustrative embodiments, an exponentially saturating function can be used, which produces rapid changes in properties close to the nominal value and saturates as the variable increases:

[0047]

[0048] Among them, c x It is the stiffness correction factor for variable x, c f It is the final stiffness correction factor at saturation, k x It is the rate of change of stiffness with respect to x around the nominal value, x and x max These are the actual and maximum values ​​of variable x.

[0049] It should be understood that the illustrative parameters described above do not constitute a complete list of conceivable parameters for the tire parameter input. Other parameters besides those mentioned above can also be used to scale tire stiffness. Similarly, other functions can be used to combine different scaling factors instead of simply multiplying them. Furthermore, other tire parameters (such as rolling radius, nominal peak friction, etc.) can alternatively be scaled using the procedures described above. This is reflected in the following illustrative embodiments.

[0050] Therefore, according to at least one illustrative embodiment, the at least one tire parameter input is a primary tire parameter input and the at least one parameter is a primary parameter, wherein the control unit is further configured to correct the function in the stored tire model based on at least one secondary tire parameter input, the secondary tire parameter input including measured values ​​of at least one secondary parameter, the at least one secondary parameter being selected from the group consisting of:

[0051] Rolling radius,

[0052] Nominal peak friction, and

[0053] Rolling resistance coefficient.

[0054] Including one or more secondary tire parameter inputs can further improve the accuracy of the control unit.

[0055] The control unit may include a microprocessor, microcontroller, programmable digital signal processor, or other programmable device. The control unit may also, or alternatively, include an application-specific integrated circuit (ASIC), a programmable gate array (FPGA) or programmable array logic, a programmable logic device, or a digital signal processor. Where the control unit includes a programmable device (such as a microprocessor, microcontroller, or programmable digital signal processor as described above), the processor may also include computer-executable code that controls the operation of the programmable device.

[0056] According to a second aspect of this disclosure, a vehicle is provided that includes a control unit according to the first aspect, including any embodiment thereof. The advantages of the vehicle of the second aspect are largely similar to the advantages of the control unit of the first aspect, including any embodiment thereof.

[0057] According to a third aspect of this disclosure, a method for controlling torque applied to a wheel of a vehicle equipped with tires is provided, comprising:

[0058] The system receives at least one tire parameter input, said tire parameter input including measured values ​​of at least one parameter affecting the longitudinal slip stiffness of the tire.

[0059] The tire model is corrected based on the received tire parameter inputs, wherein in the tire model, the longitudinal tire force is expressed as a function of the longitudinal wheel slip, which depends on the wheel rotation speed and the vehicle speed, and the step of correcting the tire model includes correcting the function.

[0060] Obtain or generate a wheel torque request.

[0061] The obtained or generated wheel torque request is converted into a wheel speed request based on the corrected function, and

[0062] The wheel speed request is sent to the actuator to provide the wheel speed corresponding to the wheel speed request.

[0063] The advantages of the method according to the third aspect largely correspond to those advantages of the control unit according to the first aspect and the vehicle according to the second aspect. Some illustrative embodiments of the method are listed below.

[0064] According to at least one illustrative embodiment, the at least one parameter is selected from the group consisting of the following parameters:

[0065] The age of the tires,

[0066] Ambient temperature,

[0067] Tire inflation pressure,

[0068] Normal load on the tire, and

[0069] Tire wear, which is appropriately approximated as the distance the tire has traveled.

[0070] According to at least one illustrative embodiment, the correction action includes applying a slip stiffness correction factor to the function, the slip stiffness correction factor varying with respect to the parameters.

[0071] According to at least one illustrative embodiment, the method includes:

[0072] The system receives multiple different tire parameter inputs, each tire parameter input including a measured value of a corresponding one of a plurality of parameters affecting the longitudinal slip stiffness of the tire, wherein the correction step includes applying a combined correction factor to the function, the combined correction factor being a function of a plurality of slip stiffness correction factors, wherein each slip stiffness correction factor varies relative to a corresponding one of the plurality of parameters.

[0073] According to at least one illustrative embodiment, the at least one tire parameter input is a primary tire parameter input and the at least one parameter is a primary parameter, wherein the correction step includes correcting the function in the stored tire model based on at least one secondary tire parameter input, the secondary tire parameter input including measured values ​​of at least one secondary parameter, the at least one secondary parameter being selected from the group consisting of:

[0074] Rolling radius,

[0075] Nominal peak friction, and

[0076] Rolling resistance coefficient.

[0077] According to at least one illustrative embodiment, the conversion process includes calculating a slip request based on a corrected function and converting the slip request into the wheel speed request using the following slip formula:

[0078]

[0079] Where λ is the longitudinal wheel slippage, Rω is the wheel rotational speed, R is the wheel radius in meters, ω is the wheel angular velocity, and v x Let be the longitudinal speed of the wheel.

[0080] According to a fourth aspect of this disclosure, a computer program is provided that includes program code means, which, when run on a computer, performs the method according to the third aspect, including any embodiments thereof. The advantages of the computer program of the fourth aspect largely correspond to the advantages of the other aspects, including any embodiments thereof.

[0081] According to a fifth aspect of this disclosure, a computer-readable medium is provided carrying a computer program including program code means, wherein when the program product is run on a computer, the program code means are configured to perform the method according to a third aspect, including any embodiment thereof. The advantages of the computer-readable medium of the fifth aspect largely correspond to the advantages of the other aspects, including any embodiment thereof.

[0082] According to a sixth aspect of this disclosure, a kit is provided comprising a tire and a tire model signal, wherein, when the tire is mounted on a vehicle, the tire model signal is adapted to generate a value of a longitudinal tire force based on the longitudinal wheel slip of the tire. By providing such a kit, other aspects of this disclosure can be advantageously used. Thus, the kit according to this disclosure can be suitably delivered to vehicle manufacturers. The tire can be mounted on the vehicle and the tire model signal can be provided, for example, on a computer-readable medium, or accessible via some form of computer network (such as a cloud-based service). Similar to the discussion above, the tire model signal can suitably include a tire model expressed as a function of at least the longitudinal wheel slip. The tire model signal can be suitably downloaded to the control unit of the vehicle discussed above, or to any other suitable onboard data storage device accessible by the control unit. Based on the above explanation, the control unit can correct the function based on received parameter inputs.

[0083] It should also be understood that the kits according to this disclosure can be provided by repair shops, retailers, or any participant. For example, when a vehicle's tires need to be replaced, the replacement tire can be provided along with an associated tire model signal. The kit is then properly installed on the vehicle by mounting the replacement tire and downloading the tire model signal to a data storage device on the vehicle. Since different brands of tires have different relationships between longitudinal tire force and longitudinal wheel slip, many different kits are conceivable, in which, in each kit, the tire model signal is specifically associated with the tire of the kit.

[0084] The tire model signal of the kit appropriately includes the nominal tire model, that is, the nominal tire model in the sense of a tire that is essentially unused under predefined temperatures, inflation pressures, etc.

[0085] Generally, all terms used in the claims should be interpreted according to their ordinary meaning in the technical field, unless otherwise expressly defined herein. All references to “a / an / element, device, component, measure, step, etc.” are disclosed to refer to at least one instance of an element, device, component, measure, step, etc., unless otherwise expressly stated. 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

[0086] Referring to the accompanying drawings, a more detailed description of embodiments of the present invention, cited by way of example, follows.

[0087] In the attached diagram:

[0088] Figure 1 A vehicle according to at least one illustrative embodiment of the present invention is shown.

[0089] Figure 2 The diagram illustrates a control system that includes a control unit according to at least one illustrative embodiment of the invention.

[0090] Figure 3 An example of a tire model is shown in which tire force is expressed as a function of longitudinal tire slip.

[0091] Figures 4a to 4d Different slip stiffness correction factors with variations in the corresponding parameters are shown.

[0092] Figure 5 A method according to an illustrative embodiment of the present invention is shown schematically.

[0093] Figure 6 A kit according to an illustrative embodiment of the invention is shown schematically.

[0094] Figure 7 A control unit according to at least one exemplary embodiment of the present invention is schematically shown.

[0095] Figure 8 A computer program product according to at least one illustrative embodiment of the present invention is shown schematically. Detailed Implementation

[0096] 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 shown in the drawings; rather, those skilled in the art will recognize that many changes and modifications can be made within the scope of the appended claims. Throughout the description, the same reference numerals refer to the same elements.

[0097] Figure 1 A vehicle 100 according to at least one illustrative embodiment of the present invention is shown. Figure 1The illustrative illustration shows a tractor unit for towing a trailer unit (not shown), which together with the trailer unit constitutes a semi-trailer. However, the invention is also applicable to other types of vehicles. For example, the vehicle can be a different type of vehicle used for transporting goods, such as a truck, or a truck having a trolley unit arranged to tow a trailer unit, etc. Furthermore, it should be understood that the concept of the invention is not limited to heavy vehicles, but can also be applied to other vehicles, such as cars.

[0098] The vehicle 100 shown is supported on wheels 102, some of which are driven wheels. Although Figure 1 The vehicle 100 in this invention has only four wheels 102, but the concept of the invention is applicable to vehicles with more wheels, such as those in the different types of vehicles described above.

[0099] Each wheel 102, or at least most of the wheels, is associated with a corresponding wheel brake. This wheel brake can be, for example, a pneumatically actuated disc brake or a drum brake, but much of this disclosure also applies to regenerative brakes that generate electrical power during vehicle deceleration, and to motors capable of slowing wheel speeds upon request. The wheel brakes are controlled by a wheel-end module (WEM), which can be controlled in ways such as... Figure 1 The braking force applied to at least one wheel 102 of a vehicle such as vehicle 100. Each WEM is communicatively coupled to a control unit ( Figure 1 (Not shown in the diagram), allowing the control unit to communicate with the WEM, 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 may, for example, distribute braking force between the wheels to maintain vehicle stability.

[0100] Each driven wheel 102 can be driven by a suitable motor (such as an electric motor, a combined motor / generator, etc.). The motor can drive more than one wheel, for example, operating across an open differential. In other illustrative embodiments, each driven wheel can be driven by a separately associated motor. In either case, the aforementioned control unit can appropriately communicatively couple such motors to distribute propulsion between the wheels. This will now be combined with... Figure 2 The control unit discussed above will be discussed in more detail.

[0101] Figure 2A control system 104 is shown, which includes a control unit 110 according to at least one exemplary embodiment of the invention. More specifically, a control system 104 for a wheel 102 is shown, exemplified here by the left wheel of the front axle of a vehicle. A wheel-end module (WEM) 112 is arranged to control wheel braking via a brake actuator 114 (i.e., part of a brake system, exemplified here by a disc brake). The brake system may also include one or more motors (EMs) 116, and / or combinations of different brake actuators. The illustrated EM 116 can also be controlled to provide propulsion to the wheel 102.

[0102] WEM 112 is communicatively coupled to control unit 110, such as a vehicle motion management (VMM) system. Although WEM 112 and VMM 110 have been shown as two functionally separate entities, it should be understood that they can be structurally configured as a single common entity. Thus, in some illustrative embodiments, WEM 112 and VMM 110 are configured as a single unit. In other illustrative embodiments, WEM 112 and VMM 110 can be structurally separate. It should also be understood that VMM 110 can be distributed across several structural entities, some of which may be remote from the vehicle, e.g., outside the vehicle. For example, some functions, such as calculations performed by VMM 110, can be cloud-based, where a portion of VMM 110 can be provided at one or more remote servers, etc.

[0103] As previously explained, the control unit 110 of the present invention (embodied herein as VMM 110) may include or be operatively connected to the data storage device 118. The data storage device 118 may therefore be located in or outside the vehicle. Figure 2 A schematic diagram illustrates a stored tire model 120 depicting a data storage device 118 with a tire for a wheel 102. (As will be combined...) Figure 3 In more detail, in tire model 120, the longitudinal tire force is expressed as at least a function of the longitudinal wheel slip. The longitudinal wheel slip depends on the wheel rotational speed and the vehicle speed. The wheel rotational speed can be determined by speed sensor 122 (see…). Figure 2 The speed of the vehicle 100 can be measured by a sensor such as a Hall effect sensor or other type of wheel speed sensor. The measured speed can be transmitted from sensor 122 to WEM 112 via a wired or wireless communication link. The speed of the vehicle 100 can be measured by another sensor (not shown, such as a radar sensor, lidar sensor, or GPS receiver), and the measured speed can be obtained by VMM 110 and / or WEM 112.

[0104] As previously explained, in order to provide precise control of wheel 102 based on tire model 120, tire model 120 should be updated to the current conditions. In this document, control of wheel 102 should be interpreted broadly to include control actions such as torque control, which controls the applied torque to follow a target torque; speed control, which controls the wheel rotation rate to follow a target speed; or wheel slip control, which controls the wheel speed or torque to follow a target wheel slip as closely as possible.

[0105] Tires can be affected by a variety of factors, such as ambient temperature, inflation pressure, normal load, aging, and wear. These and other factors can be appropriately quantified into measurable parameters and provided as tire parameter inputs. Figure 2 The diagram schematically illustrates a VMM 110 configured to receive multiple tire parameter inputs 124; however, it should be understood that in other illustrative embodiments, the VMM 110 may be configured to receive only one tire parameter input 124. Therefore, in general, according to this disclosure, a control unit 110 (such as a VMM 110) should be configured to receive at least one tire parameter input 124. Each tire parameter input includes a measured value of at least one parameter affecting the longitudinal slip stiffness of the tire, which will be combined with… Figure 3 To be discussed in more detail. Based on the received tire parameter input 124, VMM 110 is configured to correct the functions in the stored tire model 120. Therefore, the tire model 120 is updated by VMM 110 based on the current conditions, thus enabling more accurate control based on the corrected tire model 120.

[0106] Therefore, when VMM 110 receives a wheel torque request or otherwise determines the desired tire force to be generated at wheel 102, VMM can convert the received wheel torque request or desired tire force into a wheel speed request or wheel slip request based on a corrected function of tire model 120. VMM sends the wheel speed request to an actuator, such as brake actuator 114 or EM 116 (via WEM 112), to provide the wheel speed corresponding to the wheel speed request.

[0107] Figure 3 An example of tire model 120 is shown, where tire force is expressed as a function of longitudinal wheel slip. The longitudinal tire force Fx is represented by a continuous curve, while the maximum achievable lateral tire force Fy is represented by a dashed curve. It should be noted that, in this respect, longitudinal refers to the radial direction of wheel 102, specifically the radial direction parallel to the road surface and along which wheel 102 travels under normal conditions. The term lateral refers to the direction parallel to the wheel's axis of rotation. The longitudinal slip ratio, or simply longitudinal wheel slip λ, is dimensionless and can be expressed as:

[0108]

[0109] where R is the wheel radius in meters, ω is the angular velocity of the wheel, and 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 degree of slip of the wheel 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 VMM 110 may maintain / obtain information regarding v x (in the reference frame of the wheel), while the wheel speed sensor 122 may be used to determine ω.

[0110] The longitudinal tire force Fx initially rises sharply from zero to the maximum value of the curve. Although the rise is not completely constant, it can be approximated by a gradient. This gradient is also referred to as the longitudinal slip stiffness of the tire. The longitudinal slip stiffness may be affected by various parameters, as already mentioned above. For example, the longitudinal slip stiffness increases as the tire ages and wears, but decreases with inflation pressure and temperature. This is shown in Figures 4a to 4d .

[0111] Figures 4a to 4d shows different slip stiffness correction factors that vary with the corresponding parameters. Figures 4a to 4d the x-axis in represents the parameter value, and the y-axis represents the corresponding slip stiffness correction factor. Figures 4a to 4d no values are shown in . However, as discussed above, it should be understood that for any given brand and / or model of tire, the actual correction factor values or functions can be determined experimentally. For example, an indoor flat-surface tire test apparatus may be used to precisely control the parameters. Figure 4a shows the first slip stiffness correction factor c as a function of the actual inflation pressure P of the tire act , which is p a graph. Figure 4b shows the second slip stiffness correction factor c as a function of the actual ambient temperature T act , which is T a graph. Figure 4c shows the third slip stiffness correction factor c as a function of the tire age t act , which is a a graph. Figure 4d shows the fourth slip stiffness correction factor c as a function of tire wear (approximated as the travel distance d from the tachograph act ), which is w a graph. Other slip stiffness correction factors, such as a function of normal load, are also conceivable.

[0112] In Figures 4a to 4dIn this configuration, different slip stiffness correction factors are normalized, with a value of 1 representing the nominal case. Once all slip stiffness correction factors have been determined, VMM 110 can combine them to estimate the actual longitudinal slip stiffness C of the tire. act :

[0113] C act =C nom *c x1 *c x2 *c x3 ...*c xk

[0114] Among them, C nom Let c be the nominal value of the longitudinal slip stiffness of the current specific tire model 120, and where c x A simple representation could include other parameters, such as the normal load on the tire.

[0115] Based on the above discussion, it should be understood that longitudinal slip stiffness can be defined as the slope of the longitudinal tire force Fx with respect to the longitudinal wheel slip (from...). Figure 3 The gradient is shown by the dashed line in the figure. The unit of this longitudinal slip stiffness is N (Newtons) / slip (where slip is dimensionless, therefore, the actual unit of the longitudinal slip stiffness is N). The longitudinal slip stiffness can be normalized by dividing it by the normal load on the tire to give a dimensionless variable (because the longitudinal slip stiffness increases almost linearly with the normal load (within a certain load range)). Therefore, in the above equation, the actual longitudinal slip stiffness C act It can be normalized and has no units.

[0116] Therefore, it should be understood that the VMM 110 can receive tire parameter inputs 124 from one or more sensing or measuring devices, etc. (see [link to VMM 110]). Figure 2 Based on those tire parameter inputs 124, VMM 110 can calculate the corresponding slip stiffness correction factor (Figure 4) to correct the slip stiffness stored in tire model 120. Figure 3 The function in ).

[0117] Therefore, in general, VMM 110 is configured to correct the function in the stored tire model 120 by applying one or more slip stiffness correction factors to the stored function. Specifically, VMM 110 can receive multiple different tire parameter inputs 124, each tire parameter input including a measured value of a corresponding parameter among a plurality of parameters affecting the longitudinal slip stiffness of the tire, wherein VMM 110 is configured to correct the function in the stored tire model 120 by applying a combined correction factor to the function, the combined correction factor being a function of multiple slip stiffness correction factors, wherein each slip stiffness correction factor has a variation relative to a corresponding parameter among the plurality of parameters.

[0118] When VMM 110 receives a wheel torque request, or otherwise determines the desired tire force (i.e., a specific longitudinal tire force Fx) to be generated at wheel 102, VMM can access a corrected function of tire model 120 and convert it into a longitudinal slip ratio, then convert the wheel torque request into a wheel speed request based on the slip equation described above. VMM 110 then sends the wheel speed request to actuators (e.g., brake actuators 114 and EM 116) to provide a wheel speed ω corresponding to the wheel speed request. Alternatively, VMM 110 may send a slip request, and the actuators may have sensor readings to perform slip control.

[0119] Figure 5 A method 200 according to an illustrative embodiment of the present invention is shown schematically. More specifically, Figure 5 An illustrative embodiment of a method 200 for controlling the torque applied to a tire-equipped vehicle wheel 102 is shown. It should be understood that... Figure 5 The steps in the diagram do not need to be performed in the order shown. Other sequences are also conceivable. Furthermore, some steps can be performed simultaneously. Therefore, this is purely illustrative. Figure 5 The methods include:

[0120] In step S1, at least one tire parameter input is received, which includes measured values ​​of at least one parameter affecting the longitudinal slip stiffness of the tire.

[0121] In step S2, a tire model is corrected based on the received tire parameter inputs. In this tire model, the longitudinal tire force is represented as a function of longitudinal wheel slip, which depends on the wheel rotation speed and the vehicle speed. The step of correcting the tire model includes correcting this function.

[0122] In step S3, a wheel torque request is obtained or generated.

[0123] In step S4, based on the corrected function, the obtained wheel torque request is converted into a wheel speed request, and

[0124] In step S5, a wheel speed request is sent to the actuator to provide a wheel speed corresponding to the wheel speed request.

[0125] As explained above, the order of the steps may differ from the order listed above. For example, step S3 may be performed before or simultaneously with steps S1 and / or S2.

[0126] According to at least one illustrative embodiment, step S2 may include applying a slip stiffness correction factor to the function, the slip stiffness correction factor varying with respect to parameters, as discussed in more detail above. According to at least one illustrative embodiment, step S1 may include receiving multiple different tire parameter inputs, wherein step S2 includes applying a combined correction factor to the function, as discussed in more detail above. According to at least one illustrative embodiment, step S4 includes calculating a slip request based on the corrected function and converting the slip request into a wheel speed request, as described in more detail above.

[0127] Figure 6 A kit 300 according to an exemplary embodiment of the invention is illustrated schematically. Kit 300 includes a tire 302 and a tire model signal 304, the latter shown as a flash drive (such as a USB flash drive). However, the tire model signal 304 can be stored on various conceivable media and is not necessarily physically delivered with the tire 30, but can be accessed by downloading the tire model signal 304 from a remote server, etc. When the tire is mounted on the vehicle, the tire model signal 304 is adapted to generate a value of the longitudinal tire force as a function of the longitudinal wheel slip of the tire. Thus, when ordering the tire 302, for example, from a factory, or as a spare part, the tire can be combined with the associated tire model signal 304 and provided as kit 300. The tire 302 will be mounted on vehicle 100 and the associated tire model signal 304 can be downloaded to or accessed by VMM 110. Then, in subsequent operation of the vehicle, VMM 110 can update and correct the function generated by tire model signal 304. That is, VMM 110 can update the function of tire model 120 based on tire input parameter 124 and provide precise torque control, similar to the previous explanation.

[0128] Therefore, it should be understood from the above explanation that the kit 300 can be used by the vehicle 100 and / or the control unit 110. Generally, according to at least one illustrative embodiment of the kit according to the invention, the kit (in particular, the tire model signal) is configured to be used by a control unit (including any embodiment thereof) according to the first aspect of the invention, wherein the tire model signal of the kit provides the tire model used by the control unit. Similarly, generally, according to at least one illustrative embodiment of the kit according to the invention, the kit is configured for use in a method according to the third aspect of the invention, including any embodiment thereof, wherein the tire model signal of the kit provides the tire model used in the method.

[0129] Figure 7 A control unit 110 according to at least one illustrative embodiment of the present invention is shown schematically. Specifically, Figure 7The components of a control unit 110 according to an illustrative embodiment 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 VMM unit. The processing circuitry 710 may be 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 730). The processing circuitry 710 may further be provided as at least one application-specific integrated circuit (ASIC) or field-programmable gate array (FPGA).

[0130] Specifically, the processing circuit 710 is configured to cause the control unit 110 to execute a set of operations or a set of steps, such as combining... Figure 5 The method discussed herein. For example, storage medium 730 may store the set of operations, and processing circuitry 710 may be configured to retrieve the set of operations from storage medium 730 so that control unit 110 executes the set of operations. The set of operations may be provided as a set of executable instructions. Thus, processing circuitry 710 is thereby arranged to perform the illustrative methods disclosed herein.

[0131] The storage medium 730 may also include a permanent storage device, which may be any one or a combination thereof, such as a magnetic storage device, an optical storage device, a solid-state storage device, or even a remotely mounted storage device.

[0132] The control unit 110 further includes an interface 720 for communicating with at least one external device, such as a sensor that provides tire parameter input. Therefore, the interface 720 may include one or more transmitters and receivers, including analog and digital components, and an appropriate number of ports for wired or wireless communication.

[0133] The processing circuit 710 controls the general operation of the control unit 110, for example, by sending data and control signals to the interface 720 and the storage medium 730, by receiving data and reports from the interface 720, and by retrieving data and instructions from the storage medium 730. Other components and related functions of the control unit 110 are omitted to avoid confusion with the concepts presented herein.

[0134] Therefore, referring also to the previously discussed figures, Figure 7An illustrative control unit 110 is shown, configured to control the torque applied to a vehicle wheel 102 equipped with tire 302. The control unit 110 includes, or is operatively connected to, a data storage device 118 having a stored tire model 120 for the tire 302, wherein, in the tire model 120, the longitudinal tire force Fx is expressed as a function of at least longitudinal wheel slip, which depends on the rotational speed of the wheel 102 and the speed of the vehicle 100. The control unit 110 is configured to:

[0135] Receive at least one tire parameter input 124, the tire parameter input 124 including measured values ​​of at least one parameter affecting the longitudinal slip stiffness of the tire.

[0136] The function in the stored tire model 120 is corrected based on the received tire parameter input 124.

[0137] Obtain wheel torque request,

[0138] The obtained wheel torque request is converted into a wheel speed request based on the corrected function, and

[0139] A wheel speed request is sent to actuators 114 and 116 to provide the wheel speed of 102 corresponding to the wheel speed request.

[0140] Figure 8 A computer program product 800 according to at least one illustrative embodiment of the present invention is shown schematically. More specifically, Figure 8 A computer-readable medium 810 is shown carrying a computer program including a program code means 820, which, when the program product is run on a computer, is used to execute... Figure 5 The method illustrated in the example. The computer-readable medium 810 and the program code device 820 can together form a computer program product 800.

Claims

1. A control unit (110) for controlling a vehicle wheel (102) equipped with tires (302), wherein, The control unit includes a data storage device (118) or is operatively connected to the data storage device (118), the data storage device having a tire model (120) for storing the tire, wherein, in the tire model, the longitudinal tire force (Fx) is at least expressed as a function of the longitudinal wheel slip (λ), the longitudinal wheel slip depending on the rotational speed of the wheel and the speed of the vehicle. The control unit is configured to: - Receive at least one tire parameter input (124), the tire parameter input including measured values ​​of at least one parameter affecting the longitudinal slip stiffness of the tire. - Correct the function in the stored tire model based on the received tire parameter input. - Obtain or generate a wheel torque request. - Based on a corrected function, the obtained or generated wheel torque request is converted into a wheel speed request, and - The wheel speed request is sent to the actuators (114, 116) to provide the wheel speed corresponding to the wheel speed request. The control unit is configured to receive multiple different tire parameter inputs (124), each tire parameter input including a measured value of a corresponding parameter among a plurality of parameters affecting the longitudinal slip stiffness of the tire, wherein the control unit is configured to correct the function in the stored tire model (120) by applying a combined correction factor to the function in the stored tire model (120), the combined correction factor being a function of a plurality of slip stiffness correction factors, wherein each slip stiffness correction factor varies relative to a corresponding one of the plurality of parameters.

2. The control unit (110) according to claim 1, wherein, The at least one parameter is selected from the group consisting of the following parameters: - The age of the tire ( t act ), - Ambient temperature ( T act ), - The inflation pressure of the tire ( P act ), - The normal load on the tire, and - The wear of the tire, which is appropriately determined as the distance traveled by the tire ( d act ).

3. The control unit (110) according to any one of claims 1 to 2, wherein, The control unit is configured to apply a slip stiffness correction factor to the function. c p , c T , c a , c w The function in the stored tire model (120) is corrected by the slip stiffness correction factor, which varies with respect to the parameter.

4. The control unit (110) according to any one of claims 1 to 2, wherein, The at least one tire parameter input (124) is a primary tire parameter input and the at least one parameter is a primary parameter, wherein the control unit is further configured to correct the function in the stored tire model (120) based on at least one secondary tire parameter input, the secondary tire parameter input including the measured value of at least one secondary parameter, the at least one secondary parameter being selected from the group consisting of the following parameters: - Rolling radius, - Nominal peak friction, and - Rolling resistance coefficient.

5. The control unit (110) according to any one of claims 1 to 2, wherein, When converting the wheel torque request into the wheel speed request, the control unit is configured to calculate the slip request based on a corrected function and convert the slip request into the wheel speed request using the following slip formula: in λ For longitudinal wheel slippage, where Rω Let be the rotational speed of the wheel, where The radius of the wheel is expressed in meters. ω Let be the angular velocity of the wheel, and where v x Let be the longitudinal speed of the wheel.

6. A vehicle (100) comprising a control unit (110) according to any one of claims 1 to 5.

7. A method (200) for controlling torque applied to a wheel of a vehicle equipped with tires, comprising: - Receive (S1) at least one tire parameter input, the tire parameter input including measured values ​​of at least one parameter affecting the longitudinal slip stiffness of the tire. - Correcting (S2) the tire model based on the received tire parameter input, wherein in the tire model, the longitudinal tire force is expressed as a function of the longitudinal wheel slip, which depends on the wheel rotation speed and the vehicle speed, wherein the step of correcting the tire model includes correcting the function. - Obtain or generate (S3) wheel torque request, - Based on the corrected function, the obtained or generated wheel torque request is converted (S4) into a wheel speed request, and - Send the wheel speed request (S5) to the actuator to provide the wheel speed corresponding to the wheel speed request. The method (200) further includes: - Receive multiple different tire parameter inputs, each tire parameter input including a measured value of a corresponding parameter among a plurality of parameters affecting the longitudinal slip stiffness of the tire, wherein the correction step includes applying a combined correction factor to the function, the combined correction factor being a function of a plurality of slip stiffness correction factors, wherein each slip stiffness correction factor varies relative to a corresponding one of the plurality of parameters.

8. The method (200) according to claim 7, wherein, The at least one parameter is selected from the group consisting of the following parameters: - The age of the tire, - Ambient temperature, - The inflation pressure of the tire. - The normal load on the tire, and - The wear of the tire, which is appropriately determined as the distance traveled by the tire.

9. The method (200) according to any one of claims 7 to 8, wherein, The correction (S2) action includes applying a slip stiffness correction factor to the function, the slip stiffness correction factor varying with respect to the parameter.

10. The method (200) according to any one of claims 7 to 8, wherein, The at least one tire parameter input is a primary tire parameter input and the at least one parameter is a primary parameter, wherein the correction (S2) action includes correcting the function in the stored tire model based on at least one secondary tire parameter input, the secondary tire parameter input including the measured value of at least one secondary parameter, the at least one secondary parameter being selected from the group consisting of the following parameters: - Rolling radius, - Nominal peak friction, and - Rolling resistance coefficient.

11. The method (200) according to any one of claims 7 to 8, wherein, The conversion (S4) involves calculating a slip request based on a corrected function and converting the slip request into the wheel speed request using the following slip formula: in λ For the longitudinal wheel slip, wherein Rω Let be the rotational speed of the wheel, where The radius of the wheel is expressed in meters. ω Let be the angular velocity of the wheel, and where v x Let be the longitudinal speed of the wheel.

12. A computer program including program code means (820), wherein when the program is run on a computer, the program code means (820) is used to perform the steps of the method (200) according to any one of claims 7 to 11.

13. A computer-readable medium (810) carrying a computer program including a program code means (820), wherein when the program is run on a computer, the program code means (820) is configured to perform the steps of the method (200) according to any one of claims 7 to 11.

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