Method for estimating road adhesion coefficient and method and device for torque control

Abstract

Embodiments of the present invention disclose a method for estimating a road adhesion coefficient and a method and apparatus for torque control. The method for estimating the road adhesion coefficient includes: obtaining a wheel angular velocity, and determining a rate of change of the wheel angular velocity acceleration based on the wheel angular velocity; determining the wheel's road adhesion state based on the rate of change of the wheel angular velocity acceleration and a threshold; determining the road adhesion state as a first adhesion state when the rate of change of the wheel angular velocity acceleration is greater than a first threshold; and determining the road adhesion state as a third adhesion state when the rate of change of the wheel angular velocity acceleration is between the first and second thresholds and lasts for more than a preset duration; calculating a corresponding first adhesion rate based on vehicle parameters in the first or third adhesion state to obtain a first target value; and determining the road adhesion coefficient based on the first target value. Through the embodiments of the present invention, the tendency of a vehicle to slip can be predicted in advance based on the rate of change of the wheel angular velocity acceleration.

Description

Technical Field

[0001] The present invention relates to the field of automobile technology, and in particular to a method and device for estimating a road adhesion coefficient, and a method and device for torque control. Background Art

[0002] In the safety control scenario of automobiles, the road adhesion coefficient plays a particularly important role. The road adhesion coefficient allows the vehicle to perceive the road adhesion conditions under different road conditions, and then make different control strategies to ensure the safe and stable driving of the vehicle.

[0003] In the prior art, the calculation of the road adhesion coefficient has a certain lag. For example, in the event of a vehicle skidding, the road adhesion coefficient is usually calculated based on the feedback vehicle parameters only after the vehicle has skidded relative to the road. That is, the road adhesion coefficient is calculated based on the vehicle parameters at a later time, and then corresponding control is performed. This lag can affect the safe and stable driving of the vehicle. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: how to reduce the hysteresis of the calculation of the road adhesion coefficient.

[0005] To solve the above technical problems, an embodiment of the present invention provides a method for estimating a road adhesion coefficient, the method comprising:

[0006] Obtaining the wheel angular velocity, and obtaining the rate of change of the acceleration of the wheel angular velocity according to the wheel angular velocity;

[0007] The road adhesion state of the wheel is determined based on a rate of change of the wheel angular velocity acceleration and a threshold value; wherein, when the rate of change of the wheel angular velocity acceleration is greater than a first threshold value, the road adhesion state is a first adhesion state; when the rate of change of the wheel angular velocity acceleration is between the first threshold value and a second threshold value and the duration exceeds a preset duration, the road adhesion state is a third adhesion state, and the first threshold value is greater than the second threshold value;

[0008] calculating a corresponding first adhesion rate according to vehicle parameters in the first adhesion state or the third adhesion state to obtain a first target value;

[0009] A road adhesion coefficient is determined according to the first target value.

[0010] Optionally, calculating a corresponding first adhesion rate according to vehicle parameters in the first adhesion state or the third adhesion state to obtain a first target value includes:

[0011] When the road surface adhesion state is the first adhesion state or the third adhesion state, recording it as a marking moment;

[0012] Calculating a plurality of first adhesion rates according to vehicle parameters at a plurality of marking moments;

[0013] A first target value is determined according to the plurality of the first attachment rates.

[0014] Optionally, determining a first target value according to a plurality of first attachment rates includes:

[0015] When the interval between two adjacent marking moments is greater than a preset time interval, the first attachment rate at the previous marking moment is used as the first target value;

[0016] When the interval between two adjacent marking moments is less than or equal to the preset time interval, the first attachment rate at the later marking moment is used as the first target value.

[0017] Optionally, determining the road adhesion coefficient according to the first target value includes: using the first target value as the road adhesion coefficient.

[0018] Optionally, determining the road adhesion coefficient according to the first target value includes:

[0019] calculating a corresponding second adhesion rate based on the vehicle parameters in the second adhesion state; wherein when the rate of change of the acceleration of the wheel angular velocity is less than the second threshold value, the road surface adhesion state is the second adhesion state;

[0020] determining a second target value according to at least one of the second adhesion rates;

[0021] A road adhesion coefficient is determined according to the first target value and the second target value.

[0022] Optionally, determining the road adhesion coefficient according to the first target value and the second target value includes:

[0023] determining a difference in adhesion rate between the first target value and the second target value;

[0024] When the absolute value of the adhesion rate difference is greater than a preset adhesion rate difference, determining the first target value as a road adhesion coefficient;

[0025] When the absolute value of the adhesion rate difference is less than or equal to a preset adhesion rate difference, the second target value is determined to be a road adhesion coefficient.

[0026] Optionally, determining the second target value according to at least one of the second adhesion rates includes:

[0027] A plurality of corresponding second adhesion rates are determined according to a plurality of vehicle parameters in the second adhesion state, and a maximum value of the plurality of second adhesion rates is selected as a second target value.

[0028] Optionally, the second threshold is half of the first threshold.

[0029] An embodiment of the present invention further provides a method for torque control, the method comprising:

[0030] Obtaining the wheel angular velocity, and obtaining the rate of change of the acceleration of the wheel angular velocity according to the wheel angular velocity;

[0031] determining the road adhesion state of the wheel based on a rate of change of the acceleration of the wheel angular velocity and a threshold; wherein when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold, the road adhesion state is a first adhesion state; and when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold, the road adhesion state is a second adhesion state, and the first threshold is greater than the second threshold;

[0032] In the first adhesion state, controlling the motor torque corresponding to the wheel to decrease until the road adhesion state exits the first adhesion state;

[0033] In the second adhesion state, the motor torque corresponding to the wheel is controlled to increase until the road adhesion state enters the first adhesion state.

[0034] Optionally, when the rate of change of the acceleration of the wheel angular velocity is between the first threshold and the second threshold and the duration exceeds a preset duration, the road adhesion state is a third adhesion state, and the method further includes:

[0035] In the third adhesion state, the motor torque corresponding to the wheel is controlled to increase until the road adhesion state enters the first adhesion state.

[0036] Optionally, the method further includes:

[0037] Obtain road adhesion coefficient;

[0038] The road adhesion capacity equivalent torque is determined according to the road adhesion coefficient.

[0039] Optionally, in the second adhesion state, controlling the motor torque corresponding to the wheel to increase until the road adhesion state enters the first adhesion state includes:

[0040] In the second adhesion state, if the current torque is less than the adhesion equivalent torque and the absolute value of the torque difference between the current torque and the adhesion equivalent torque is greater than a first preset torque difference, the first preset torque difference is used as a first step to increase the current torque toward the adhesion equivalent torque until the absolute value of the torque difference between the current torque and the adhesion equivalent torque is less than or equal to the first preset torque difference;

[0041] If the current torque is less than the adhesion equivalent torque and the torque difference between the current torque and the adhesion equivalent torque is less than or equal to a first preset torque difference, the adhesion equivalent torque is used as the motor output torque;

[0042] After the adhesion equivalent torque is used as the motor output torque, if the road adhesion state is still in the second adhesion state, increasing the adhesion equivalent torque toward the first adhesion state in a second step length until the road adhesion state enters the first adhesion state; wherein the second step length is smaller than the first step length;

[0043] In the third adhesion state, controlling the motor torque corresponding to the wheel to increase until the road adhesion state enters the first adhesion state includes:

[0044] In the third adhesion state, if the current torque is less than the adhesion capability equivalent torque and the torque difference between the current torque and the adhesion capability equivalent torque is less than or equal to a first preset torque difference, the adhesion capability equivalent torque is increased in a third step size toward the adhesion capability equivalent torque until the road adhesion state enters the first adhesion state; wherein the third step size is smaller than the second step size.

[0045] Optionally, determining the road adhesion equivalent torque according to the road adhesion coefficient includes:

[0046] Get the axle load and wheel rolling radius;

[0047] The road adhesion equivalent torque is determined according to the axle load, the wheel rolling radius, and the road adhesion coefficient.

[0048] Optionally, obtaining the road adhesion coefficient includes referring to the road adhesion coefficient estimation method as described above.

[0049] An embodiment of the present invention further provides a device for estimating a road adhesion coefficient, the device comprising:

[0050] a first acceleration change rate determination module, configured to obtain the wheel angular velocity and obtain the acceleration change rate of the wheel angular velocity according to the wheel angular velocity;

[0051] a first road adhesion state determination module, configured to determine the road adhesion state of the wheel based on a rate of change of the acceleration of the wheel angular velocity and a threshold; wherein, when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold, the road adhesion state is a first adhesion state; and when the rate of change of the acceleration of the wheel angular velocity is between the first threshold and a second threshold and lasts for more than a preset duration, the road adhesion state is a third adhesion state, and the first threshold is greater than the second threshold;

[0052] a first target value obtaining module, configured to calculate a corresponding first adhesion rate according to vehicle parameters in the first adhesion state or the third adhesion state, so as to obtain a first target value;

[0053] The road adhesion coefficient determination module is used to determine the road adhesion coefficient according to the first target value.

[0054] An embodiment of the present invention further provides a torque control device, comprising:

[0055] a second acceleration change rate determination module, for obtaining the wheel angular velocity and obtaining the acceleration change rate of the wheel angular velocity according to the wheel angular velocity;

[0056] a second road adhesion state determination module for determining the road adhesion state of the wheel based on a rate of change of the acceleration of the wheel angular velocity and a threshold; wherein when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold, the road adhesion state is a first adhesion state; and when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold, the road adhesion state is a second adhesion state, and the first threshold is greater than the second threshold;

[0057] a torque control module in a first adhesion state, configured to control the motor torque corresponding to the wheel to decrease in the first adhesion state until the road adhesion state exits the first adhesion state;

[0058] The torque control module in the second adhesion state is used to control the motor torque corresponding to the wheel to increase in the second adhesion state until the road adhesion state enters the first adhesion state.

[0059] In an embodiment of the present invention, the wheel angular velocity is acquired, the rate of change of the wheel angular velocity acceleration is determined based on the wheel angular velocity, and the road adhesion state of the wheel is determined based on the rate of change of the wheel angular velocity acceleration and a threshold. When the rate of change of the wheel angular velocity acceleration is greater than a first threshold, the road adhesion state is a first adhesion state. When the rate of change of the wheel angular velocity acceleration is between the first and second thresholds and lasts for more than a preset duration, the road adhesion state is a third adhesion state, where the first threshold is greater than the second threshold. A first adhesion ratio is then calculated based on vehicle parameters in the first or third adhesion state to obtain a first target value, and a road adhesion coefficient is determined based on the first target value. This enables early prediction of the vehicle's slippage tendency based on the rate of change of the wheel angular velocity acceleration. The road adhesion coefficient is then calculated using vehicle parameters at an earlier time point, reducing the hysteresis of the road adhesion coefficient calculation and ensuring the accuracy of the road adhesion coefficient. This provides a relatively accurate basis for corresponding control, thereby ensuring safe and stable driving of the vehicle.

[0060] The torque control method of the present invention performs torque control according to the adhesion state of the wheel on the road surface, so that the adhesion state of the wheel on the road surface switches between a second adhesion state close to the first adhesion state and a first adhesion state close to the second adhesion state, thereby causing the torque to fluctuate within a small range and improving the driving stability of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the description of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0062] Figure 1 This is an overall architecture diagram provided by an embodiment of the present invention;

[0063] Figure 2 This is a flowchart of a method for estimating a road adhesion coefficient provided by one embodiment of the present invention;

[0064] Figure 3a 1 is a schematic diagram of the relationship between torque and slip ratio provided by an embodiment of the present invention;

[0065] Figure 3b is a schematic diagram of an example of estimating a road adhesion coefficient provided by an embodiment of the present invention;

[0066] Figure 4 This is a flowchart of a torque control method provided by one embodiment of the present invention;

[0067] Figure 5 is a schematic diagram of an example of torque control provided by an embodiment of the present invention;

[0068] Figure 6a is a schematic diagram of a torque control effect provided by an embodiment of the present invention;

[0069] Figure 6b is a schematic diagram of another torque control effect provided by an embodiment of the present invention;

[0070] Figure 7 This is a structural block diagram of a device for estimating a road adhesion coefficient provided by one embodiment of the present invention;

[0071] Figure 8 This is a structural block diagram of a torque control device provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0072] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0073] In the embodiment of the present invention, Figure 1 On the one hand, the road adhesion state is judged by the wheel speed, that is, whether the torque exceeds the road adhesion capacity. On the other hand, the adhesion rate of the front and rear axles is calculated through vehicle parameters such as the longitudinal acceleration of the vehicle, slope, front and rear motor torque, wheelbase, front and rear wheelbase, and center of mass height.

[0074] After obtaining the adhesion rate and adhesion state, the maximum adhesion rate of the front and rear axles, that is, the adhesion coefficient of the road surface, can be calculated based on the adhesion rate and adhesion state. Then, the adhesion equivalent torque of the road surface can be calculated based on the front and rear axle loads and the wheel rolling radius. Torque control can then be performed based on the adhesion equivalent torque.

[0075] In torque control, the adhesion equivalent torque can be used to adjust the total shaft torque demand obtained to achieve the shaft torque demand that matches the road adhesion capacity.

[0076] Reference Figure 2 , which shows a flowchart of a method for estimating a road adhesion coefficient provided by an embodiment of the present invention, which may specifically include the following steps:

[0077] Step 201 : Acquire the wheel angular velocity, and obtain the rate of change of the acceleration of the wheel angular velocity according to the wheel angular velocity.

[0078] In a specific implementation, the wheel angular velocity can be read by the vehicle's wheel speed sensor. The wheel angular velocity may include the wheel angular velocity of the vehicle's front axle wheels and the wheel angular velocity of the vehicle's rear axle wheels. Then, the acceleration of the wheel angular velocity can be calculated based on the read wheel angular velocity. The acceleration of the wheel angular velocity is the derivative of the wheel angular velocity. Then, the rate of change of the acceleration of the wheel angular velocity can be calculated based on the acceleration of the wheel angular velocity. The rate of change of the acceleration of the wheel angular velocity is the derivative of the acceleration of the wheel angular velocity. That is to say, the rate of change of the acceleration of the wheel angular velocity is the second derivative of the wheel angular velocity.

[0079] Step 202: Determine the road adhesion state of the wheel based on the rate of change of the wheel angular velocity acceleration and a threshold. When the rate of change of the wheel angular velocity acceleration is greater than a first threshold, the road adhesion state is a first adhesion state. When the rate of change of the wheel angular velocity acceleration is between the first and second thresholds and lasts for longer than a preset duration, the road adhesion state is a third adhesion state, and the first threshold is greater than the second threshold.

[0080] The value between the first threshold and the second threshold includes the first threshold and the second threshold, and a value between the first threshold and the second threshold.

[0081] The road adhesion state of the wheel can reflect whether the longitudinal driving force provided by the current torque of the vehicle to the wheel exceeds the adhesion capacity of the road. The specific analysis is as follows:

[0082] The dynamic equations of the contact points between the front and rear axle wheels of the vehicle and the road are as follows:

[0083]

[0084]

[0085] Among them, J w is the equivalent total moment of inertia of the front axle wheel or the rear axle wheel, ω f 、ω r are the angular velocities of the front and rear axle wheels, specifically the average angular velocities of the two wheels on each axle. are the derivatives of the angular velocity of the front axle wheels and the rear axle wheels, that is, the acceleration of the angular velocity, T f 、T r are the motor output torque of the front axle wheel or the rear axle wheel, i f 、i r are the main reducer speed ratios of the front and rear axles, F X1 、F X2 are the longitudinal driving forces of the road surface on the front and rear axle wheels, specifically the sum of the longitudinal driving forces of the road surface on the two wheels on each axle, r t The rolling radius of the front or rear axle wheels.

[0086] Respectively represent the longitudinal driving force of the front axle wheels and the rear axle wheels actually used for acceleration, T f i f 、T r i r Respectively represents the longitudinal driving force provided by the current torque of the motor to the front axle wheels and the rear axle wheels, F X1 r t 、F X2 r t The longitudinal driving force provided to the front and rear axle wheels by the road surface.

[0087] Combine Figure 3a It can be seen that as the current torque of the motor increases, the longitudinal driving force provided by the current torque of the motor to the wheel (such as Figure 3a Middle T f i fThe corresponding curve) gradually increases, and the longitudinal driving force provided by the road surface to the wheel (such as Figure 3a Medium F X1 r t The corresponding curve) also increases accordingly.

[0088] When the longitudinal driving force provided by the current torque of the motor to the wheel is greater than the maximum longitudinal driving force provided by the road surface to the wheel (such as Figure 3a Medium F X1 r t The highest point of the corresponding curve), that is, the longitudinal driving force provided by the current torque to the wheel exceeds the adhesion capacity of the road, and then the following situations will occur:

[0089] 1. The acceleration of the wheel angular velocity will increase rapidly.

[0090] 2. As the acceleration of the wheel angular velocity increases, the acceleration of the wheel angular velocity will be greater than the acceleration of the vehicle speed, which will lead to an increase in the slip rate and intensify the skidding phenomenon.

[0091] The slip rate can represent the severity of the vehicle's slippage when it moves forward, and can be expressed using the following formula:

[0092]

[0093] Where s is the slip rate, v is the vehicle speed, and ω is the wheel angular velocity.

[0094] 3. The longitudinal driving force that the road surface can provide to the wheels (such as Figure 3a Medium F X1 r t The corresponding curve) will further decrease, thereby exacerbating Case 1 and Case 2.

[0095] Based on this, the road adhesion state of the wheel can be judged by combining the rate of change of the acceleration of the wheel angular velocity with a threshold. The threshold may include a first threshold and a second threshold. The value range of the first threshold may be 10 rad / s 3 Up to 100 rad / s 3 , the second threshold can be half of the first threshold.

[0096] When the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold, it can be determined that the road adhesion state is the first adhesion state, that is, the longitudinal driving force provided to the wheel by the current torque of the motor exceeds the road adhesion capacity. When the rate of change of the acceleration of the wheel angular velocity is between the first and second thresholds and the duration exceeds a preset duration, such as the preset duration ranges from 10ms to 50ms, the road adhesion state is determined to be the third adhesion state, that is, the longitudinal driving force provided to the wheel by the current torque of the motor approaches the road adhesion capacity.

[0097] Step 203 : Calculate a corresponding first adhesion rate according to vehicle parameters in the first adhesion state or the third adhesion state to obtain a first target value.

[0098] When the wheel is in the first adhesion state or the third adhesion state, the vehicle parameters can be obtained, and then the first adhesion rate can be determined based on the vehicle parameters. The first target value, that is, the first target adhesion rate, can be determined based on the first adhesion rate.

[0099] For the front axle adhesion rate and the rear axle adhesion rate, the equivalent slope of the vehicle can be determined based on the vehicle acceleration and road slope in the vehicle parameters, and then the adhesion rate can be determined based on the torque distribution ratio and the equivalent slope in the vehicle parameters.

[0100] Specifically, for the equivalent slope, the vehicle acceleration can be measured by the vehicle acceleration sensor, and the road slope can be read from the output signal of the slope estimation module. Then, the equivalent slope of the vehicle can be calculated based on the vehicle acceleration and the road slope, as shown in the following formula:

[0101]

[0102] Among them, q is the longitudinal acceleration sensor signal, A x is the vehicle acceleration, θ is the road slope, and g is the acceleration due to gravity.

[0103] Regarding the torque distribution ratio, the torque distribution ratio may be the torque distribution ratio of either the front axle or the rear axle. The torque distribution ratio of the other axle may be calculated by subtracting the total ratio. Specifically, the current torque may be read from the output signal of the motor controller, which may include the torque of the front axle and the torque of the rear axle. The torque distribution ratio may then be calculated based on the torque of the front axle and the torque of the rear axle, as shown in the following formula:

[0104]

[0105] Where, Ψ is the torque distribution ratio of the rear axle, T r is the torque on the rear axle, T f is the torque on the front axle.

[0106] After obtaining the equivalent slope and torque distribution ratio, the adhesion rates of the front and rear axle tires can be calculated separately based on the vehicle wheelbase, front wheelbase, rear wheelbase, and vehicle center of mass height, as shown in the following formula:

[0107]

[0108]

[0109] in, are the adhesion rates of the front and rear axle tires, L is the vehicle wheelbase, a is the front wheelbase, b is the rear wheelbase, h g is the height of the vehicle's center of mass.

[0110] In one embodiment of the present invention, step 203 may include:

[0111] Sub-step 11: When the road surface adhesion state is the first adhesion state or the third adhesion state, record it as a marking moment.

[0112] Each time the first attachment state or the third attachment state is entered, the time at that time can be remembered as a marked time.

[0113] Sub-step 12: calculating a plurality of first adhesion rates according to the vehicle parameters at the plurality of marking moments.

[0114] At each marking moment, a first adhesion rate may be calculated according to vehicle parameters to obtain a plurality of first adhesion rates.

[0115] Sub-step 13: determining a first target value according to the plurality of first attachment rates.

[0116] After obtaining the plurality of first attachment rates, a first target value may be determined based on the plurality of first attachment rates.

[0117] In one embodiment of the present invention, sub-step 13 may include:

[0118] Sub-step 131 : when the interval between two adjacent marking moments is greater than a preset time interval, the first attachment rate at the previous marking moment is used as the first target value.

[0119] In a specific implementation, since the marking moments are recorded in advance, the time interval between two adjacent marking moments can be determined, which may be the time interval between the two most recent marking moments.

[0120] When the time interval is greater than the preset time interval, for example, the preset time interval may range from 10 ms to 100 ms, the first attachment rate at the previous marking moment may be used as the first target value.

[0121] Sub-step 132 : when the interval between two adjacent marking moments is less than or equal to a preset time interval, the first attachment rate at the later marking moment is used as the first target value.

[0122] When the time interval is less than or equal to the preset time interval, the first attachment rate at the subsequent marking moment may be used as the first target value.

[0123] In one embodiment of the present invention, a first attachment rate in a first attachment state may be used as the first target value, or a first attachment rate in a third attachment state may be used as the first target value.

[0124] Step 204: Determine the road adhesion coefficient according to the first target value.

[0125] After obtaining the first target value, a road surface adhesion coefficient may be determined according to the first target value. The road surface adhesion coefficient may be used to characterize the adhesion capability of the road surface.

[0126] In one embodiment of the present invention, step 204 may include:

[0127] The first target value is used as the road adhesion coefficient.

[0128] In a specific implementation, the first target value can be directly used as the road adhesion coefficient.

[0129] In one embodiment of the present invention, step 204 may include:

[0130] Sub-step 21, calculating a corresponding second adhesion rate based on the vehicle parameters in the second adhesion state; wherein, when the rate of change of the acceleration of the wheel angular velocity is less than the second threshold value, the road adhesion state is the second adhesion state.

[0131] When the rate of change of the acceleration of the wheel angular velocity is less than a second threshold, it can be determined that the road adhesion state is the second adhesion state, that is, the longitudinal driving force provided to the wheel by the current torque of the motor does not exceed and does not approach the road adhesion capacity. When entering the second adhesion state, the second adhesion rate can be calculated based on the obtained vehicle parameters.

[0132] Sub-step 22: determining a second target value according to at least one of the second adhesion rates.

[0133] After the second attachment rates are obtained, a second target value may be determined according to at least one second attachment rate.

[0134] In one embodiment of the present invention, sub-step 22 may include:

[0135] A plurality of corresponding second adhesion rates are determined according to a plurality of vehicle parameters in the second adhesion state, and a maximum value of the plurality of second adhesion rates is selected as a second target value.

[0136] For multiple marking moments in the second attachment state, multiple second attachment rates can be obtained, and then the largest second attachment rate can be selected and used as the second target value.

[0137] Specifically, the second attachment rate at the later marking time may be compared with the second attachment rate at the earlier marking time, and the larger second attachment rate may be used as the second target value.

[0138] In one embodiment, the second adhesion rate at a single moment may also be used as the second target value.

[0139] Sub-step 23: determining a road adhesion coefficient according to the first target value and the second target value.

[0140] After the first target value and the second target value are obtained, the road adhesion coefficient may be determined according to the first target value and the second target value.

[0141] In one embodiment of the present invention, sub-step 23 may include:

[0142] Sub-step 231: determining the difference in adhesion rate between the first target value and the second target value.

[0143] After specific implementation, the difference between the first target value and the second target value can be calculated to obtain the attachment rate difference.

[0144] Sub-step 232 , when the absolute value of the adhesion rate difference is greater than a preset adhesion rate difference, determining the first target value as a road adhesion coefficient.

[0145] When the absolute value of the adhesion rate difference is greater than the preset adhesion rate difference, for example, the preset adhesion rate difference may range from 0.1 to 0.5, the first target value may be determined as the road adhesion coefficient.

[0146] Sub-step 233 , when the absolute value of the adhesion rate difference is less than or equal to a preset adhesion rate difference, determining the second target value as a road adhesion coefficient.

[0147] When the absolute value of the adhesion rate difference is less than or equal to the preset adhesion rate difference, the second target value may be determined as the road adhesion coefficient.

[0148] The following combination Figure 3b The present invention is exemplified as follows:

[0149] 1. Input the road adhesion status, adhesion rate C, and corresponding time point t of the front or rear axle tire.

[0150] 2. Calculate the first target value a as follows:

[0151] 2.1. Determine whether the road adhesion state is the first adhesion state max- or the third adhesion state max0.

[0152] 2.2. When the road surface adhesion state is the first adhesion state max- or the third adhesion state max0, record the marking time t k , and determine the tth k The first adhesion rate at the moment n=C(k).

[0153] 2.3. When the road adhesion state returns to the first adhesion state max- or the third adhesion state max0, record the marking time t k+1 .

[0154] 2.4. Calculate the time interval t between two marked moments k+1 -t k , and determine the time interval t k+1 -t k Is it greater than the preset time interval T1? k+1 -t k If the time interval is greater than the preset time interval T1, t k The first adhesion rate n at time t is given as the first target value to a. k+1 -t k If the time interval is less than or equal to the preset time interval T1, t k+1 The first adhesion rate C(k+1) at the time is used as the first target value a.

[0155] 3. Calculate the second target value e as follows:

[0156] 3.1. When the road surface adhesion state is the second adhesion state max+, determine whether the second adhesion ratio C(i) at the subsequent time i is greater than the second adhesion ratio C(i-1) at the subsequent time i-1, and then use the larger second adhesion ratio as the second target value e.

[0157] 4. Calculate the adhesion rate difference ea between the first target value a and the second target value e, and determine whether the absolute value of the adhesion rate difference ea is greater than the preset adhesion rate difference K.

[0158] 5. When the absolute value of the adhesion difference ea is greater than the preset adhesion difference K, the first target value a is used as the road adhesion coefficient When the absolute value of the adhesion difference ea is less than or equal to the preset adhesion difference K, the second target value e is used as the road adhesion coefficient.

[0159] In an embodiment of the present invention, the wheel angular velocity is acquired, the rate of change of the wheel angular velocity acceleration is determined based on the wheel angular velocity, and the road adhesion state of the wheel is determined based on the rate of change of the wheel angular velocity acceleration and a threshold. When the rate of change of the wheel angular velocity acceleration is greater than a first threshold, the road adhesion state is a first adhesion state. When the rate of change of the wheel angular velocity acceleration is between the first and second thresholds and lasts for more than a preset duration, the road adhesion state is a third adhesion state, where the first threshold is greater than the second threshold. A first adhesion ratio is then calculated based on vehicle parameters in the first or third adhesion state to obtain a first target value, and a road adhesion coefficient is determined based on the first target value. This enables early prediction of the vehicle's slippage tendency based on the rate of change of the wheel angular velocity acceleration. The road adhesion coefficient is then calculated using vehicle parameters at an earlier time point, reducing the hysteresis of the road adhesion coefficient calculation and ensuring the accuracy of the road adhesion coefficient. This provides a relatively accurate basis for corresponding control, thereby ensuring safe and stable driving of the vehicle.

[0160] Reference Figure 4 , shows a flowchart of a torque control method provided by an embodiment of the present invention, which may specifically include the following steps:

[0161] Step 401: Acquire the wheel angular velocity, and obtain the rate of change of the acceleration of the wheel angular velocity according to the wheel angular velocity.

[0162] For the description of step 401 , reference may be made to the above description of step 201 .

[0163] Step 402: Determine the road adhesion state of the wheel based on the rate of change of the acceleration of the wheel angular velocity and a threshold value; wherein, when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, the road adhesion state is a first adhesion state; when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold value, the road adhesion state is a second adhesion state, and the first threshold value is greater than the second threshold value.

[0164] For the description of step 402 , reference may be made to the description of step 202 and sub-step 21 above.

[0165] In one embodiment of the present invention, the method may further include:

[0166] Obtaining a road surface adhesion coefficient; and determining the road surface adhesion equivalent torque based on the road surface adhesion coefficient.

[0167] In a specific implementation, the road adhesion coefficient may be obtained by referring to the description of step 103 above, and then the road adhesion capacity equivalent torque may be determined based on the road adhesion coefficient.

[0168] In one embodiment of the present invention, determining the road adhesion capacity equivalent torque based on the road adhesion coefficient includes: obtaining the axle load and the wheel rolling radius; and determining the road adhesion capacity equivalent torque based on the axle load, the wheel rolling radius, and the road adhesion coefficient.

[0169] In a specific implementation, the wheel rolling radius can be obtained first, and the axle loads of the front and rear axles can be calculated. Then, the axle load and the wheel rolling radius can be used to convert the road adhesion coefficient into an equivalent torque of the road adhesion capacity. The following formula can be used:

[0170]

[0171]

[0172] Among them, T fmax 、T rmax are the adhesion equivalent torques of the front and rear axles, are the road adhesion coefficients of the front and rear axles, F z1 、F z2 are the axle loads of the front and rear axles, r t is the wheel rolling radius.

[0173] The axle load can be calculated based on the vehicle mass, gravitational acceleration, road slope, front wheelbase, rear wheelbase, vehicle wheelbase, vehicle center of mass height, and vehicle acceleration, as shown in the following formula:

[0174]

[0175]

[0176] Among them, F z1 、F z2 They are the axle loads of the front and rear axles, M is the mass of the vehicle, g is the acceleration of gravity, a is the front wheelbase, b is the rear wheelbase, L is the wheelbase of the vehicle, h g is the height of the vehicle's center of mass.

[0177] Step 403: In the first adhesion state, control the motor torque corresponding to the wheel to decrease until the road adhesion state exits the first adhesion state.

[0178] In the first adhesion state, that is, the longitudinal driving force provided to the wheel by the current torque of the motor exceeds the road adhesion capacity, the motor torque corresponding to the wheel can be controlled to decrease until the road adhesion state exits the first adhesion state and enters the second adhesion state. For example, the motor torque can be reduced in steps ranging from -200Nm to -10Nm.

[0179] Step 404: In the second adhesion state, control the motor torque corresponding to the wheel to increase until the road adhesion state enters the first adhesion state.

[0180] In the second adhesion state, that is, the longitudinal driving force provided to the wheel by the current torque of the motor does not exceed the road adhesion capacity, the motor torque corresponding to the wheel can be controlled to increase until the road adhesion state enters the first adhesion state.

[0181] In one embodiment of the present invention, step 404 may include:

[0182] Sub-step 31: In the second adhesion state, if the current torque is less than the adhesion capability equivalent torque and the absolute value of the torque difference between the current torque and the adhesion capability equivalent torque is greater than a first preset torque difference, the first preset torque difference is used as a first step to increase the current torque toward the adhesion capability equivalent torque until the absolute value of the torque difference between the current torque and the adhesion capability equivalent torque is less than or equal to the first preset torque difference.

[0183] When the current torque is less than the adhesion equivalent torque, the absolute value of the torque difference between the current torque and the adhesion equivalent torque can be calculated. When the absolute value of the torque difference is greater than the first preset torque difference, such as the first preset torque difference can range from 10Nm to 100Nm, that is, the difference between the current torque and the adhesion equivalent torque is large, the first preset torque difference can be used as the first step to increase the adhesion equivalent torque, gradually approaching the adhesion equivalent torque.

[0184] In sub-step 32 , if the current torque is less than the adhesion equivalent torque and the torque difference between the current torque and the adhesion equivalent torque is less than or equal to a first preset torque difference, the adhesion equivalent torque is used as the motor output torque.

[0185] When the absolute value of the torque difference is less than or equal to the first preset torque difference, that is, the difference between the current torque and the adhesion equivalent torque is small, the adhesion equivalent torque can be directly used as the motor output torque to control the torque increase.

[0186] In sub-step 33, after the adhesion equivalent torque is used as the motor output torque, if the road adhesion state is still in the second adhesion state, the adhesion equivalent torque is increased in a second step size until the road adhesion state enters the first adhesion state; wherein the second step size is smaller than the first step size.

[0187] After the adhesion equivalent torque is used as the motor output torque, it is possible to detect again whether the road adhesion state has entered the first adhesion state from the second adhesion state. If so, the torque is controlled in the same manner as in the first adhesion state. If not, the torque can be continued to be controlled to increase with a smaller second step size.

[0188] In one embodiment of the present invention, when the rate of change of the acceleration of the wheel angular velocity is between the first threshold and the second threshold and the duration exceeds a preset duration, the road adhesion state may be the third adhesion state. The method may further include:

[0189] In the third adhesion state, the motor torque corresponding to the wheel is controlled to increase until the road adhesion state enters the first adhesion state.

[0190] In the third adhesion state, that is, the longitudinal driving force provided to the wheel by the current torque of the motor approaches the road adhesion capability, the motor torque corresponding to the wheel can be controlled to increase until the road adhesion state enters the first adhesion state.

[0191] In one embodiment of the present invention, controlling the motor torque corresponding to the wheel to increase in the third adhesion state until the road adhesion state enters the first adhesion state may include:

[0192] In the third adhesion state, if the current torque is less than the adhesion capability equivalent torque and the torque difference between the current torque and the adhesion capability equivalent torque is less than or equal to a first preset torque difference, the adhesion capability equivalent torque is increased in a third step size toward the adhesion capability equivalent torque until the road adhesion state enters the first adhesion state; wherein the third step size is smaller than the second step size.

[0193] When the current torque is less than the adhesion equivalent torque, if the absolute value of the torque difference is less than or equal to the first preset torque difference, that is, the difference between the current torque and the adhesion equivalent torque is small, the torque increase can be continued with a smaller third step size.

[0194] The following combination Figure 5 The present invention is exemplified as follows:

[0195] 1. The current shaft torque demand T_req increases in steps of Step0. The value range of Step0 can be 10Nm to 100Nm. At time K, the actual torque of the motor (i.e., the current torque) is T_actl, and the adhesion equivalent torque is T_max.

[0196] 2. Determine whether the road surface adhesion state is the first adhesion state max-.

[0197] 3. When the road adhesion state is the first adhesion state max-, the torque is reduced with Step 3 as the step size. The value range of Step 3 can be -200 Nm to -10 Nm, that is, T_req(k+1)=T_req(k)+step2.

[0198] 4. When the road adhesion state is the first adhesion state max-, calculate the absolute value T_actl-T_max of the torque difference between the current torque T_actl and the adhesion equivalent torque T_max, and determine whether the absolute value T_actl-T_max of the torque difference is less than the first preset torque difference Step0.

[0199] 5. When the absolute value of the torque difference T_actl-T_max is greater than or equal to the first preset torque difference Step0, continue to increase the torque with Step0 as the step size.

[0200] 6. When the absolute value of the torque difference T_act1-T_max is less than the first preset torque difference Step0, further determine whether the road adhesion state is the second adhesion state max+.

[0201] 7. When the road adhesion state is the second adhesion state max+, the adhesion capacity equivalent torque can be directly used as the motor output torque, that is, T_req(k+1)=T_max.

[0202] 8. After the adhesion-equivalent torque is used as the motor output torque, it is possible to again determine whether the road adhesion state is in the second adhesion state (max+). If so, the torque increase can be continued with a smaller second step size, Step 1. The value range of Step 1 can be 10 Nm to 100 Nm. If the road adhesion state is not in the second adhesion state (max+), torque control can be performed using the strategy for the corresponding adhesion state.

[0203] 9. When the road adhesion state is not the second adhesion state max+, that is, the road adhesion state is the third adhesion state max0, the torque increase can be continued with a smaller third step length Step2.

[0204] In an embodiment of the present invention, the wheel angular velocity is acquired, and the rate of change of the acceleration of the wheel angular velocity is obtained based on the wheel angular velocity. The road adhesion state of the wheel is determined based on the rate of change of the acceleration of the wheel angular velocity and a threshold value. When the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, the road adhesion state is a first adhesion state. When the rate of change of the acceleration of the wheel angular velocity is less than a second threshold value, the road adhesion state is a second adhesion state. The first threshold value is greater than the second threshold value. Then, in the first adhesion state, the torque of the motor corresponding to the wheel is controlled to decrease until the road adhesion state exits the first adhesion state. In the second adhesion state, the torque of the motor corresponding to the wheel is controlled to increase until the road adhesion state enters the first adhesion state. This implements torque control based on the wheel adhesion state to the road surface, so that the torque approaches the adhesion capacity of the road surface, improves the accuracy of torque control, and thereby ensures safe and stable driving of the vehicle.

[0205] The following combination Figure 6a and Figure 6b The beneficial effects of the present invention are described as follows:

[0206] like Figure 6a In order to control the shaft torque demand T by using the road adhesion equivalent torque as the torque reference value, as shown in Figure 6b This is the case where the road surface adhesion equivalent torque is not used as the torque reference value to control the shaft torque demand T. It can be seen that when the road surface adhesion equivalent torque is used as the torque reference value to control the shaft torque demand T, the following beneficial effects are achieved:

[0207] 1. During the torque increase phase, the equivalent axle torque of the road's adhesion capacity is used as the reference value for the torque increase of the front and rear axles. The torque increase rate can be adjusted after the maximum torque increase rate reaches this reference value. Compared with the general method of limiting the torque increase step size, this can effectively reduce the response time.

[0208] 2. After the torque reduction control is completed until the vehicle is in a stable state, the torque recovery phase begins. The equivalent axle torque of the road adhesion is calculated as a reference value for the torque increase of the front and rear axle motors to avoid unlimited torque increase that may cause the wheels to slip again and trigger the torque reduction control.

[0209] In the prior art, whether slippage has occurred is determined based on the difference between the actual slip rate and the preset slip rate, and the slippage determination result can only be obtained after the wheel speed increases to the point where slippage occurs. The present invention determines the slippage trend (mechanical critical point) based on the mechanical equation of the wheel-ground contact point. The determination result is obtained when slippage has not occurred but the motor torque has actually exceeded the torque that the road surface can withstand. Therefore, the adhesion coefficient calculation method of the present invention is more accurate. In addition, the torque is controlled according to the slip rate. Due to the hysteresis of the judgment, the torque range required to adjust from the slipping state to the normal state is larger and the time required is longer (see Figure 6b ).

[0210] The torque control method of the present invention controls the torque according to the slip tendency, that is, the first adhesion state and the second adhesion state. In the first adhesion state, that is, when there is a slip tendency, the torque is timely reduced to avoid the risk of slipping. After the torque is reduced until the first adhesion state is entered into the second adhesion state, the torque is increased again until the first adhesion state is entered again. In other words, the torque control makes the wheel's adhesion to the road surface increase the torque in time after entering the second adhesion state from the first adhesion state to make it enter the first adhesion state again, and reduces the torque in time after entering the first adhesion state from the second adhesion state to make it enter the second adhesion state again. In this way, the wheel's road adhesion state stays in the first adhesion state and the second adhesion state for a shorter time, so that the torque control range is also within a smaller range, which is specifically manifested as fluctuation within a smaller range of the equivalent axial torque of the road adhesion capacity (see Figure 6a ), improving the driving stability of the vehicle. In addition, since the wheels have a tendency to slip in the first adhesion state, but no slip occurs, the driving safety of the vehicle is also guaranteed.

[0211] It should be noted that for the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should be aware that the embodiments of the present invention are not limited by the order of the actions described, because according to the embodiments of the present invention, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in this specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present invention.

[0212] Reference Figure 7 , shows a structural block diagram of a road adhesion coefficient estimation device provided by an embodiment of the present invention, which may specifically include the following modules:

[0213] The first acceleration change rate determination module 701 is configured to obtain the wheel angular velocity and obtain the acceleration change rate of the wheel angular velocity according to the wheel angular velocity.

[0214] The first road adhesion state determination module 702 is configured to determine the road adhesion state of the wheel based on the rate of change of the wheel angular velocity acceleration and a threshold. When the rate of change of the wheel angular velocity acceleration is greater than the first threshold, the road adhesion state is considered the first adhesion state. When the rate of change of the wheel angular velocity acceleration is between the first and second thresholds and lasts for longer than a predetermined duration, the road adhesion state is considered the third adhesion state, and the first threshold is greater than the second threshold.

[0215] The first target value obtaining module 703 is configured to calculate the corresponding first adhesion rate according to the vehicle parameters in the first adhesion state or the third adhesion state to obtain a first target value.

[0216] The road adhesion coefficient determination module 704 is configured to determine the road adhesion coefficient according to the first target value.

[0217] In one embodiment of the present invention, the first target value obtaining module 703 may include:

[0218] a marking moment recording submodule, configured to record, when the road surface adhesion state is the first adhesion state or the third adhesion state, as a marking moment;

[0219] a plurality of first adhesion rate calculation submodules, configured to calculate a plurality of first adhesion rates according to vehicle parameters at a plurality of marking moments;

[0220] The multiple first attachment rates determine a first target value submodule is configured to determine a first target value according to the multiple first attachment rates.

[0221] In one embodiment of the present invention, the plurality of first attachment rate determination first target value submodules may include:

[0222] a previous marking moment determining unit, configured to use the first attachment rate at the previous marking moment as a first target value when the interval between two adjacent marking moments is greater than a preset time interval;

[0223] The subsequent marking time determining unit is configured to use the first attachment rate at the subsequent marking time as the first target value when the interval between two adjacent marking times is less than or equal to a preset time interval.

[0224] In one embodiment of the present invention, the road adhesion coefficient determination module 704 may include:

[0225] The first target value is used as a coefficient submodule, which is used to use the first target value as a road adhesion coefficient.

[0226] In one embodiment of the present invention, the road adhesion coefficient determination module 704 may include:

[0227] a second adhesion rate calculation submodule, configured to calculate a corresponding second adhesion rate based on vehicle parameters in a second adhesion state; wherein when the rate of change of the acceleration of the wheel angular velocity is less than the second threshold value, the road adhesion state is the second adhesion state;

[0228] a second target value determination submodule, configured to determine a second target value according to at least one of the second attachment rates;

[0229] Combined with the second target value determination coefficient submodule, it is used to determine the road adhesion coefficient according to the first target value and the second target value.

[0230] In one embodiment of the present invention, the second target value determination coefficient submodule may include:

[0231] an attachment rate difference determination unit, configured to determine an attachment rate difference between the first target value and the second target value;

[0232] a determining unit for a first target value as a road adhesion coefficient, configured to determine the first target value as a road adhesion coefficient when the absolute value of the adhesion rate difference is greater than a preset adhesion rate difference;

[0233] The second target value is determined as a road adhesion coefficient unit, and is used to determine the second target value as a road adhesion coefficient when the absolute value of the adhesion rate difference is less than or equal to a preset adhesion rate difference.

[0234] In one embodiment of the present invention, the second target value determination submodule may include:

[0235] The maximum value selecting unit is used to determine a plurality of corresponding second adhesion rates according to a plurality of vehicle parameters in the second adhesion state, and select a maximum value of the plurality of second adhesion rates as a second target value.

[0236] In one embodiment of the present invention, the second threshold is half of the first threshold.

[0237] Reference Figure 8 , shows a structural block diagram of a torque control device provided by an embodiment of the present invention, which may specifically include the following modules:

[0238] The second acceleration change rate determination module 801 obtains the wheel angular velocity and obtains the acceleration change rate of the wheel angular velocity according to the wheel angular velocity.

[0239] The second road adhesion state judgment module 802 judges the road adhesion state of the wheel based on the rate of change of the acceleration of the wheel angular velocity and a threshold value. When the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, the road adhesion state is the first adhesion state; when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold value, the road adhesion state is the second adhesion state, and the first threshold value is greater than the second threshold value.

[0240] The torque control module 803 in the first adhesion state is used to control the motor torque corresponding to the wheel to reduce in the first adhesion state until the road adhesion state exits the first adhesion state.

[0241] The torque control module 804 in the second adhesion state is used to control the motor torque corresponding to the wheel to increase in the second adhesion state until the road adhesion state enters the first adhesion state.

[0242] In one embodiment of the present invention, when the rate of change of the acceleration of the wheel angular velocity is between the first threshold and the second threshold and the duration exceeds a preset duration, the road adhesion state is the third adhesion state, and the device may further include:

[0243] The torque control module in the third adhesion state is used to control the motor torque corresponding to the wheel to increase in the third adhesion state until the road adhesion state enters the first adhesion state.

[0244] In one embodiment of the present invention, the device further comprises:

[0245] A road adhesion coefficient acquisition module is used to obtain the road adhesion coefficient;

[0246] The adhesion capacity equivalent torque determination module is used to determine the adhesion capacity equivalent torque of the road surface according to the road surface adhesion coefficient.

[0247] In one embodiment of the present invention, the torque control module 804 in the second adhesion state may include:

[0248] a first-step increase submodule configured to, in the second adhesion state, if the current torque is less than the adhesion capability equivalent torque and the absolute value of the torque difference between the current torque and the adhesion capability equivalent torque is greater than a first preset torque difference, increase the current torque toward the adhesion capability equivalent torque using the first preset torque difference as a first step until the absolute value of the torque difference between the current torque and the adhesion capability equivalent torque is less than or equal to the first preset torque difference;

[0249] an adhesion capacity equivalent torque output submodule, configured to use the adhesion capacity equivalent torque as the motor output torque if the current torque is less than the adhesion capacity equivalent torque and the torque difference between the current torque and the adhesion capacity equivalent torque is less than or equal to a first preset torque difference;

[0250] a submodule for increasing with a second step length, configured to, after the adhesion capacity equivalent torque is used as the motor output torque, if the road adhesion state is still in the second adhesion state, increase the adhesion capacity equivalent torque with a second step length toward the first adhesion state until the road adhesion state enters the first adhesion state; wherein the second step length is smaller than the first step length;

[0251] In one embodiment of the present invention, the torque control module in the third adhesion state may include:

[0252] A submodule for increasing with a third step size is configured to, in the third adhesion state, if the current torque is less than the adhesion capability equivalent torque and the torque difference between the current torque and the adhesion capability equivalent torque is less than or equal to a first preset torque difference, increase the adhesion capability equivalent torque with a third step size toward the adhesion capability equivalent torque until the road adhesion state enters the first adhesion state; wherein the third step size is smaller than the second step size.

[0253] In one embodiment of the present invention, the adhesion equivalent torque determination module may include:

[0254] Axle load and radius acquisition submodule, used to obtain axle load and wheel rolling radius;

[0255] The axle load and radius determination submodule is combined to determine the road adhesion equivalent torque according to the axle load, the wheel rolling radius, and the road adhesion coefficient.

[0256] In one embodiment of the present invention, obtaining the road adhesion coefficient includes referring to the road adhesion coefficient estimation device as described above.

[0257] An embodiment of the present invention further provides an electronic device, which may include a processor, a memory, and a computer program stored in the memory and capable of running on the processor. When the computer program is executed by the processor, the above-mentioned road adhesion coefficient estimation method or torque control method is implemented.

[0258] An embodiment of the present invention further provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the method for estimating the road adhesion coefficient or the method for controlling torque is implemented.

[0259] As for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0260] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for estimating a road adhesion coefficient, characterized in that: The method comprises: Obtaining the wheel angular velocity, and obtaining the rate of change of the acceleration of the wheel angular velocity according to the wheel angular velocity; The road adhesion state of the wheel is determined based on a rate of change of the wheel angular velocity acceleration and a threshold value; wherein, when the rate of change of the wheel angular velocity acceleration is greater than a first threshold value, the road adhesion state is a first adhesion state; when the rate of change of the wheel angular velocity acceleration is between the first threshold value and a second threshold value and the duration exceeds a preset duration, the road adhesion state is a third adhesion state, and the first threshold value is greater than the second threshold value; calculating a corresponding first adhesion rate according to vehicle parameters in the first adhesion state or the third adhesion state to obtain a first target value; A road adhesion coefficient is determined according to the first target value.

2. The method according to claim 1, characterized in that The calculating a corresponding first adhesion rate according to the vehicle parameters in the first adhesion state or the third adhesion state to obtain a first target value includes: When the road surface adhesion state is the first adhesion state or the third adhesion state, recording it as a marking moment; Calculating a plurality of first adhesion rates according to vehicle parameters at a plurality of marking moments; A first target value is determined according to the plurality of the first attachment rates.

3. The method according to claim 2, characterized in that The determining a first target value according to the plurality of first attachment rates includes: When the interval between two adjacent marking moments is greater than a preset time interval, the first attachment rate at the previous marking moment is used as the first target value; When the interval between two adjacent marking moments is less than or equal to the preset time interval, the first attachment rate at the later marking moment is used as the first target value.

4. The method according to any one of claims 1 to 3, characterized in that Determining the road adhesion coefficient according to the first target value includes: using the first target value as the road adhesion coefficient.

5. The method according to any one of claims 1 to 3, characterized in that Determining the road adhesion coefficient according to the first target value includes: calculating a corresponding second adhesion rate based on the vehicle parameters in the second adhesion state; wherein when the rate of change of the acceleration of the wheel angular velocity is less than the second threshold value, the road surface adhesion state is the second adhesion state; determining a second target value according to at least one of the second adhesion rates; A road adhesion coefficient is determined according to the first target value and the second target value.

6. The method according to claim 5, characterized in that Determining the road adhesion coefficient according to the first target value and the second target value includes: determining a difference in adhesion rate between the first target value and the second target value; When the absolute value of the adhesion rate difference is greater than a preset adhesion rate difference, determining the first target value as a road adhesion coefficient; When the absolute value of the adhesion rate difference is less than or equal to a preset adhesion rate difference, the second target value is determined to be a road adhesion coefficient.

7. The method according to claim 6, characterized in that The determining a second target value according to at least one of the second attachment rates includes: A plurality of corresponding second adhesion rates are determined according to a plurality of vehicle parameters in the second adhesion state, and a maximum value of the plurality of second adhesion rates is selected as a second target value.

8. The method according to claim 1, characterized in that The second threshold is half of the first threshold.

9. A method for torque control, characterized in that: The method comprises: Obtaining the wheel angular velocity, and obtaining the rate of change of the acceleration of the wheel angular velocity according to the wheel angular velocity; determining the road adhesion state of the wheel based on a rate of change of the acceleration of the wheel angular velocity and a threshold; wherein when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold, the road adhesion state is a first adhesion state; and when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold, the road adhesion state is a second adhesion state, and the first threshold is greater than the second threshold; In the first adhesion state, controlling the motor torque corresponding to the wheel to decrease until the road adhesion state exits the first adhesion state; In the second adhesion state, the motor torque corresponding to the wheel is controlled to increase until the road adhesion state enters the first adhesion state.

10. The method according to claim 9, characterized in that When the rate of change of the acceleration of the wheel angular velocity is between the first threshold and the second threshold and the duration exceeds a preset duration, the road adhesion state is a third adhesion state, and the method further includes: In the third adhesion state, the motor torque corresponding to the wheel is controlled to increase until the road adhesion state enters the first adhesion state.

11. The method according to claim 10, characterized in that The method further comprises: Obtain road adhesion coefficient; The road adhesion capacity equivalent torque is determined according to the road adhesion coefficient.

12. The method according to claim 11, characterized in that In the second adhesion state, controlling the motor torque corresponding to the wheel to increase until the road adhesion state enters the first adhesion state includes: In the second adhesion state, if the current torque is less than the adhesion capability equivalent torque and the absolute value of the torque difference with the adhesion capability equivalent torque is greater than a first preset torque difference, the first preset torque difference is used as a first step to increase the torque toward the adhesion capability equivalent torque until the absolute value of the torque difference with the adhesion capability equivalent torque is less than or equal to the first preset torque difference; If the current torque is less than the adhesion equivalent torque and the torque difference between the current torque and the adhesion equivalent torque is less than or equal to a first preset torque difference, the adhesion equivalent torque is used as the motor output torque; After the adhesion equivalent torque is used as the motor output torque, if the road adhesion state is still in the second adhesion state, increasing the adhesion equivalent torque toward the first adhesion state in a second step length until the road adhesion state enters the first adhesion state; wherein the second step length is smaller than the first step length; In the third adhesion state, controlling the motor torque corresponding to the wheel to increase until the road adhesion state enters the first adhesion state includes: In the third adhesion state, if the current torque is less than the adhesion capability equivalent torque and the torque difference between the current torque and the adhesion capability equivalent torque is less than or equal to a first preset torque difference, the adhesion capability equivalent torque is increased in a third step size toward the adhesion capability equivalent torque until the road adhesion state enters the first adhesion state; wherein the third step size is smaller than the second step size.

13. The method according to any one of claims 11-12, characterized in that Determining the road adhesion capacity equivalent torque according to the road adhesion coefficient includes: Get the axle load and wheel rolling radius; The road adhesion equivalent torque is determined according to the axle load, the wheel rolling radius, and the road adhesion coefficient.

14. The method according to claim 11, characterized in that Obtaining the road adhesion coefficient includes referring to the method according to any one of claims 1-8.

15. A device for estimating a road adhesion coefficient, characterized in that: The device comprises: a first acceleration change rate determination module, configured to obtain the wheel angular velocity and obtain the acceleration change rate of the wheel angular velocity according to the wheel angular velocity; a first road adhesion state determination module, configured to determine the road adhesion state of the wheel based on a rate of change of the acceleration of the wheel angular velocity and a threshold; wherein, when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold, the road adhesion state is a first adhesion state; and when the rate of change of the acceleration of the wheel angular velocity is between the first threshold and a second threshold and lasts for more than a preset duration, the road adhesion state is a third adhesion state, and the first threshold is greater than the second threshold; a first target value obtaining module, configured to calculate a corresponding first adhesion rate according to vehicle parameters in the first adhesion state or the third adhesion state, so as to obtain a first target value; A road adhesion coefficient determination module is used to determine the road adhesion coefficient according to the first target value.

16. A torque control device, characterized in that: The device comprises: a second acceleration change rate determination module, configured to obtain the wheel angular velocity and obtain the acceleration change rate of the wheel angular velocity according to the wheel angular velocity; a second road surface adhesion state determination module, configured to determine the road surface adhesion state of the wheel based on a rate of change of the acceleration of the wheel angular velocity and a threshold; wherein when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold, the road surface adhesion state is a first adhesion state; and when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold, the road surface adhesion state is a second adhesion state, and the first threshold is greater than the second threshold; a torque control module in a first adhesion state, configured to control the motor torque corresponding to the wheel to decrease in the first adhesion state until the road adhesion state exits the first adhesion state; The torque control module in the second adhesion state is used to control the motor torque corresponding to the wheel to increase in the second adhesion state until the road adhesion state enters the first adhesion state.

Images