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

Abstract

The embodiment of the present application provides a road adhesion coefficient estimation method and a torque control method and device, the road adhesion coefficient estimation method comprises the following steps: obtaining a wheel angular velocity, obtaining a change rate of the wheel angular velocity acceleration according to the wheel angular velocity; judging a road adhesion state of the wheel according to the change rate of the wheel angular velocity acceleration and a threshold value; wherein when the change rate of the wheel angular velocity acceleration is greater than the threshold value, the road adhesion state is a first adhesion state; determining a first target adhesion rate according to vehicle parameters in the first adhesion state, and determining a road adhesion coefficient according to the first target adhesion rate. Through the embodiment of the present application, the trend of vehicle skidding is predicted in advance according to the change rate of the wheel angular velocity acceleration, and then the road adhesion coefficient is calculated by using the vehicle parameters at an earlier time, so that the hysteresis of the road adhesion coefficient calculation is reduced, and the accuracy of the road adhesion coefficient is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automotive technology, in particular to a road adhesion coefficient estimation method and device, and a torque control method and device. BACKGROUND

[0002] In the safety control scenario of an automobile, the road adhesion coefficient plays a particularly important role. Through the road adhesion coefficient, the vehicle can perceive the road adhesion condition 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 hysteresis. For example, for the vehicle slip event, the road adhesion coefficient is usually calculated according to the feedback vehicle parameters after the vehicle has already experienced the slip event relative to the road surface, that is, the road adhesion coefficient is calculated according to the vehicle parameters at a later time, and then the corresponding control is performed. This hysteresis will affect the safe and stable driving of the vehicle. SUMMARY

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

[0005] To solve the above technical problem, the present application provides a road adhesion coefficient estimation method, which comprises:

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

[0007] Determining the road adhesion state of the wheel according to 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 the threshold value, the road adhesion state is a first adhesion state;

[0008] Determining a first target adhesion rate according to the vehicle parameters in the first adhesion state, and determining the road adhesion coefficient according to the first target adhesion rate.

[0009] Optionally, the determination of the first target adhesion rate according to the vehicle parameters in the first adhesion state comprises:

[0010] Determining a plurality of first adhesion rates according to a plurality of vehicle parameters in the first adhesion state;

[0011] Determining the first target adhesion rate according to a plurality of first adhesion rates.

[0012] Optionally, the determination of the first target adhesion rate according to a plurality of first adhesion rates comprises:

[0013] acquire a first time and a second time in the first adhesion state of the two adjacent wheels, and determine a time interval according to the first time and the second time, the first time being earlier than the second time;

[0014] when the time interval is greater than a preset time interval, taking a first adhesion rate in the first adhesion state corresponding to the first time as the first target adhesion rate;

[0015] when the time interval is less than or equal to the preset time interval, taking a first adhesion rate in the first adhesion state corresponding to the second time as the first target adhesion rate.

[0016] Optionally, the determining the road adhesion coefficient according to the first target adhesion rate comprises: determining the first target adhesion rate as the road adhesion coefficient.

[0017] Optionally, the determining the road adhesion coefficient according to the first target adhesion rate comprises:

[0018] determining a second adhesion rate according to a vehicle parameter in a second adhesion state; wherein, when a change rate of the acceleration of the wheel angular velocity is less than or equal to a threshold value, the road adhesion state is the second adhesion state;

[0019] determining a second target adhesion rate according to at least one second adhesion rate;

[0020] determining a road adhesion coefficient according to the first target adhesion rate and the second target adhesion rate.

[0021] Optionally, the determining the road adhesion coefficient according to the first target adhesion rate and the second target adhesion rate comprises:

[0022] determining an adhesion rate difference between the first target adhesion rate and the second target adhesion rate;

[0023] in a case where an absolute value of the adhesion rate difference is greater than a preset adhesion rate difference, determining the first target adhesion rate as the road adhesion coefficient;

[0024] in a case where the absolute value of the adhesion rate difference is less than or equal to the preset adhesion rate difference, determining the second target adhesion rate as the road adhesion coefficient.

[0025] Optionally, the determining the second target adhesion rate according to at least one second adhesion rate comprises:

[0026] determining a plurality of corresponding second adhesion rates according to a plurality of vehicle parameters in a plurality of second adhesion states, and selecting a maximum value of the plurality of second adhesion rates as the second target adhesion rate.

[0027] The embodiment of the present application also provides a torque control method, which comprises the following steps:

[0028] obtaining a wheel angular velocity, and obtaining a change rate of acceleration of the wheel angular velocity according to the wheel angular velocity;

[0029] judging a road surface adhesion state of the wheel according to the change rate of acceleration of the wheel angular velocity and a threshold value; when the change rate of acceleration of the wheel angular velocity is greater than the threshold value, the road surface adhesion state is a first adhesion state;

[0030] when the change rate of acceleration of the wheel angular velocity is less than or equal to the threshold value, the road surface adhesion state is a second adhesion state;

[0031] in the first adhesion state, the torque of the motor corresponding to the wheel is controlled to be reduced until the road surface adhesion state enters the second adhesion state;

[0032] in the second adhesion state, the torque of the motor corresponding to the wheel is controlled to be increased until the road surface adhesion state enters the first adhesion state.

[0033] Optionally, the method further comprises the following steps:

[0034] obtaining a road surface adhesion coefficient;

[0035] determining an adhesion capacity equivalent torque of the road surface according to the road surface adhesion coefficient.

[0036] Optionally, the step of controlling the torque of the motor corresponding to the wheel to be increased in the second adhesion state until the road surface adhesion state enters the first adhesion state comprises the following steps:

[0037] in the second adhesion state, if a current torque is less than the adhesion capacity equivalent torque and an absolute value of a torque difference between the current torque and the adhesion capacity equivalent torque is greater than a first preset torque difference, the adhesion capacity equivalent torque is increased by the first preset torque difference as a first step length until the absolute value of the torque difference between the adhesion capacity equivalent torque and the current torque is less than or equal to the first preset torque difference;

[0038] 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 the first preset torque difference, the adhesion capacity equivalent torque is taken as a motor output torque;

[0039] after the adhesion capacity equivalent torque is taken as the motor output torque, if the road surface adhesion state is still the second adhesion state, the motor output torque is gradually increased by a second step length until the road surface adhesion state enters the first adhesion state;

[0040] the second step length is less than the first step length.

[0041] Optionally, the determining the equivalent torque of the adhesion capacity of the road surface according to the road surface adhesion coefficient comprises:

[0042] obtaining the axle load and the wheel rolling radius;

[0043] determining the equivalent torque of the adhesion capacity of the road surface according to the axle load, the wheel rolling radius, and the road surface adhesion coefficient.

[0044] Optionally, the obtaining the road surface adhesion coefficient comprises referring to the estimation method of the road surface adhesion coefficient as described above.

[0045] The embodiment of the present application further provides an estimation device of a road surface adhesion coefficient, the device comprising:

[0046] a first change rate determining module configured to obtain the wheel angular velocity and obtain the change rate of the acceleration of the wheel angular velocity according to the wheel angular velocity;

[0047] a first road surface adhesion state judging module configured to judge the road surface adhesion state of the wheel according to the change rate of the acceleration of the wheel angular velocity and a threshold value; wherein when the change rate of the acceleration of the wheel angular velocity is greater than the threshold value, the road surface adhesion state is a first adhesion state;

[0048] a road surface adhesion coefficient determining module configured to determine a first target adhesion rate according to the vehicle parameters in the first adhesion state, and determine the road surface adhesion coefficient according to the first target adhesion rate.

[0049] The embodiment of the present application further provides a torque control device, the device comprising:

[0050] a second change rate determining module configured to obtain the wheel angular velocity and obtain the change rate of the acceleration of the wheel angular velocity according to the wheel angular velocity;

[0051] a second road surface adhesion state judging module configured to judge the road surface adhesion state of the wheel according to the change rate of the acceleration of the wheel angular velocity and a threshold value; wherein when the change rate of the acceleration of the wheel angular velocity is greater than the threshold value, the road surface adhesion state is a first adhesion state; and when the change rate of the acceleration of the wheel angular velocity is less than or equal to the threshold value, the road surface adhesion state is a second adhesion state;

[0052] a first adhesion state torque control module configured to control the motor torque corresponding to the wheel to decrease in the first adhesion state until the road surface adhesion state enters the second adhesion state;

[0053] a second adhesion state torque control module configured to control the motor torque corresponding to the wheel to increase in the second adhesion state until the road surface adhesion state enters the first adhesion state.

[0054] In the embodiment of the present application, by acquiring the wheel angular velocity, the rate of change of the acceleration of the wheel angular velocity is obtained according to the wheel angular velocity, and the road surface adhesion state of the wheel is judged according to the rate of change of the acceleration of the wheel angular velocity and the threshold value, when the rate of change of the acceleration of the wheel angular velocity is greater than the threshold value, the road surface adhesion state is the first adhesion state, then the first target adhesion rate is determined according to the vehicle parameter in the first adhesion state, and the road surface adhesion coefficient is determined according to the first target adhesion rate, which realizes the early prediction of the trend of vehicle slip according to the rate of change of the acceleration of the wheel angular velocity, and then the road surface adhesion coefficient is calculated with the vehicle parameter at an earlier time, which reduces the hysteresis of the road surface adhesion coefficient calculation, ensures the accuracy of the road surface adhesion coefficient, and then provides a relatively accurate basis for the corresponding control, and ensures the safe and stable driving of the vehicle.

[0055] The torque control method of the present application controls the torque 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 the second adhesion state close to the first adhesion state and the first adhesion state close to the second adhesion state, so that the torque fluctuates in a small range, improving the driving stability of the vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed to be used in the description of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0057] Figure 1 is a kind of overall architecture provided by an embodiment of the present application;

[0058] Figure 2 is a kind of step flow chart of the estimation method of road surface adhesion coefficient provided by an embodiment of the present application;

[0059] Figure 3a is a kind of relationship diagram of torque and slip rate provided by an embodiment of the present application;

[0060] Figure 3b is a kind of estimation example of road surface adhesion coefficient provided by an embodiment of the present application;

[0061] Figure 4 is a kind of step flow chart of the torque control method provided by an embodiment of the present application;

[0062] Figure 5 is a kind of example of torque control provided by an embodiment of the present application;

[0063] Figure 6ais a schematic diagram of torque control effect provided by an embodiment of the present application;

[0064] Figure 6b is a schematic diagram of another torque control effect provided by an embodiment of the present application;

[0065] Figure 7 is a structural block diagram of an estimation device of road adhesion coefficient provided by an embodiment of the present application;

[0066] Figure 8 is a structural block diagram of a torque control device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0067] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0068] In the embodiments of the present application, as Figure 1 , on the one hand, the adhesion state of the road is judged by the rotation speed of the wheel, that is, whether the torque exceeds the adhesion capacity of the road, and on the other hand, the adhesion rate of the front and rear axles is calculated by the vehicle parameters such as the longitudinal acceleration of the whole vehicle, the slope, the front and rear motor torques, the wheelbase, the front and rear wheelbases, the height of the center of mass, etc.

[0069] After obtaining the adhesion rate and the adhesion state, the maximum adhesion rate of the front and rear axles, that is, the adhesion capacity coefficient of the road, can be calculated according to the adhesion rate and the adhesion state, and then the adhesion capacity equivalent torque of the road is calculated in combination with the front and rear axle loads and the wheel rolling radii, and further the torque control can be performed according to the adhesion capacity equivalent torque.

[0070] In the torque control, the adhesion capacity equivalent torque can be used to adjust the obtained total axle torque demand to achieve the axle torque demand that matches the adhesion capacity of the road.

[0071] The embodiments of the present application will be specifically described below:

[0072] Referring to Figure 2 , a step flowchart of a road adhesion coefficient estimation method provided by an embodiment of the present application is shown, which can specifically include the following steps:

[0073] In step 201, the wheel angular speed is obtained, and the change rate of the wheel angular speed acceleration is obtained according to the wheel angular speed.

[0074] In a specific implementation, the wheel angular velocity can be read by a wheel speed sensor of the vehicle, the wheel angular velocity can include wheel angular velocities of front axle wheels of the vehicle and wheel angular velocities of rear axle wheels of the vehicle, then the acceleration of the wheel angular velocity can be calculated according to the read wheel angular velocity, the acceleration of the wheel angular velocity is a derivative of the wheel angular velocity, and then the rate of change of the acceleration of the wheel angular velocity can be calculated according to the acceleration of the wheel angular velocity, the rate of change of the acceleration of the wheel angular velocity is a derivative of the acceleration of the wheel angular velocity, that is, the rate of change of the acceleration of the wheel angular velocity is a second derivative of the wheel angular velocity.

[0075] In step 202, the road adhesion state of the wheel is determined according to 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 the threshold value, the road adhesion state is a first adhesion state.

[0076] For the road adhesion state of the wheel, whether the current torque provided by the vehicle to the wheel exceeds the adhesion capacity of the road can be reflected, and a specific analysis is as follows:

[0077] The dynamic equation of the contact point of the front axle wheel and the rear axle wheel with the road is as follows:

[0078]

[0079] wherein, 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 axle wheel and the rear axle wheel, specifically, the average of the angular velocities of the two wheels on each axle, are derivatives of the angular velocities of the front axle wheel and the rear axle wheel, that is, the acceleration of the angular velocity, T f , T r are the motor output torques of the front axle wheel or the rear axle wheel, i f , i r are the main reducer speed ratios of the front axle and the rear axle, F X1 , F X2 are the road longitudinal driving forces borne by the front axle wheel and the rear axle wheel, specifically, the sum of the road longitudinal driving forces borne by the two wheels on each axle, r t is the wheel rolling radius of the front axle wheel or the rear axle wheel. respectively represent the longitudinal driving forces actually used for acceleration of the front axle wheel and the rear axle wheel, T f i f , T r i r respectively represent the longitudinal driving forces provided by the current torque of the motor to the front axle wheel and the rear axle wheel, F X1 r t , FX2 r t respectively.

[0080] Combining 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 T f i f corresponding curve) gradually increases, and the longitudinal driving force provided by the road to the wheel (such as Figure 3a F X1 r t corresponding curve) also increases.

[0081] When the longitudinal driving force provided by the current torque of the motor to the wheel is greater than the maximum value of the longitudinal driving force provided by the road to the wheel (such as Figure 3a F X1 r t corresponding curve), that is, the longitudinal driving force provided by the current torque to the wheel exceeds the adhesion capacity of the road, the following situations will occur thereafter:

[0082] 1. The acceleration of the wheel angular velocity will accelerate.

[0083] 2. As the acceleration of the wheel angular velocity accelerates, the acceleration of the wheel angular velocity will be greater than the acceleration of the vehicle speed, thereby causing the slip ratio to rise and the phenomenon of slipping to intensify.

[0084] The slip ratio can represent the severity of the slipping phenomenon when the vehicle is advancing, which can be represented by the following formula:

[0085]

[0086] Where s is the slip ratio, v is the vehicle speed, and ω is the wheel angular velocity.

[0087] 3. The longitudinal driving force provided by the road to the wheel (such as Figure 3a F X1 r t corresponding curve) will further decrease, thereby intensifying situation 1 and situation 2.

[0088] Based on this, the road adhesion state of the wheel can be determined by the rate of change of the acceleration of the wheel angular velocity in combination with a threshold value, and the threshold value can be in the range of 10 rad / s 3 to 100 rad / s 3 When the rate of change of the acceleration of the wheel angular velocity is greater than the preset threshold value, it can be determined that the road adhesion state is the first adhesion state, that is, the longitudinal driving force provided by the current torque of the motor to the wheel exceeds the adhesion capacity of the road.

[0089] In step 203, a first target adhesion rate is determined according to the vehicle parameters in the first adhesion state, and a road adhesion coefficient is determined according to the first target adhesion rate.

[0090] In the case that the wheels are in the first adhesion state, the vehicle parameters can be obtained, and then the first target adhesion rate can be determined according to the vehicle parameters, and then the road adhesion coefficient can be determined according to the first target adhesion rate, which can be used to represent the adhesion ability of the road.

[0091] For the front axle adhesion rate and the rear axle adhesion rate, the equivalent slope of the whole vehicle can be determined according to the vehicle acceleration and the road slope in the vehicle parameters, and then the adhesion rate can be determined according to the torque distribution ratio and the equivalent slope in the vehicle parameters.

[0092] Specifically, for the equivalent slope, the vehicle acceleration measured by the vehicle acceleration sensor can be obtained, and the road slope can be read from the slope estimation related module output signal, and then the equivalent slope of the whole vehicle can be calculated according to the vehicle acceleration and the road slope, as shown in the following formula:

[0093]

[0094] Wherein, q is the longitudinal acceleration sensor signal, A x is the vehicle acceleration, θ is the road slope, and g is the acceleration of gravity.

[0095] For the torque distribution ratio, the torque distribution ratio of any one of the front axle or the rear axle can be used, and the torque distribution ratio of the other axle can be obtained by subtracting the calculated torque distribution ratio from the total ratio. Specifically, the current torque can be read from the motor controller output signal, which can include the torque of the front axle and the torque of the rear axle, and then the torque distribution ratio can be calculated according to the torque of the front axle and the torque of the rear axle, as shown in the following formula:

[0096]

[0097] Wherein, Ψ is the torque distribution ratio of the rear axle, T r is the torque of the rear axle, T f is the torque of the front axle.

[0098] After obtaining the equivalent slope and the torque distribution ratio, the adhesion rates of the front axle tire and the rear axle tire can be calculated respectively by combining the wheelbase of the whole vehicle, the front wheelbase, the rear wheelbase, and the height of the center of gravity of the whole vehicle, as shown in the following formula:

[0099]

[0100] Wherein, C φ1 , C φ2is the adhesion rate of the front axle tire and the rear axle tire, respectively, L is the wheelbase of the vehicle, a is the front wheelbase, b is the rear wheelbase, h g is the height of the vehicle mass center.

[0101] In an embodiment of the present application, the determining the first target adhesion rate according to the vehicle parameters in the first adhesion state can include:

[0102] Sub-step 11: determining a plurality of first adhesion rates according to a plurality of vehicle parameters in the first adhesion state.

[0103] In each time when entering the first adhesion state, the first adhesion rate can be calculated according to the obtained vehicle parameters, that is, a plurality of first adhesion rates can be obtained.

[0104] Sub-step 12: determining the first target adhesion rate according to a plurality of first adhesion rates.

[0105] After obtaining the first adhesion rates in a plurality of first adhesion states, the first target adhesion rate can be determined based on the first adhesion rates in the plurality of first adhesion states.

[0106] In an embodiment of the present application, sub-step 12 can include:

[0107] Sub-step 121: obtaining a first time and a second time in adjacent two first adhesion states, and determining a time interval according to the first time and the second time, the first time being earlier than the second time.

[0108] In a specific implementation, the corresponding first adhesion rate can be calculated at each time in the first adhesion state, and for the adjacent two times in the first adhesion state, the two times can be the most recent two times, and the time interval of the two times can be calculated.

[0109] Sub-step 122: when the time interval is greater than a preset time interval, taking the first adhesion rate in the first adhesion state corresponding to the first time as the first target adhesion rate.

[0110] When the time interval is greater than the preset time interval, the value range of the preset time interval can be 10 ms to 100 ms, and the first adhesion rate in the first adhesion state corresponding to the first time can be taken as the first target adhesion rate, that is, the first adhesion rate at the previous time is taken as the first target adhesion rate.

[0111] Sub-step 123: when the time interval is less than or equal to the preset time interval, taking the first adhesion rate in the first adhesion state corresponding to the second time as the first target adhesion rate.

[0112] When the time interval is greater than the preset time interval, the first adhesion rate in the first adhesion state corresponding to the second time can be taken as the first target adhesion rate, i.e., the first adhesion rate at the later time is taken as the first target adhesion rate.

[0113] In an embodiment of the present application, the first adhesion rate in a first adhesion state can also be taken as the first target adhesion rate.

[0114] In an embodiment of the present application, determining the road adhesion coefficient according to the first target adhesion rate can include determining the first target adhesion rate as the road adhesion coefficient.

[0115] In a specific implementation, the first target adhesion rate can be directly taken as the road adhesion coefficient.

[0116] In an embodiment of the present application, determining the road adhesion coefficient according to the first target adhesion rate can include:

[0117] Sub-step 21: determining a second adhesion rate according to vehicle parameters in a second adhesion state; wherein when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value, the road adhesion state is the second adhesion state.

[0118] When the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value, it can be determined that the road adhesion state is the second adhesion state, i.e., the longitudinal driving force provided by the current torque of the motor to the wheel does not exceed the road adhesion capacity, and in the second adhesion state, the second adhesion rate can be calculated according to the obtained vehicle parameters.

[0119] Sub-step 22: determining a second target adhesion rate according to at least one second adhesion rate.

[0120] After obtaining the second adhesion rate, the second target adhesion rate can be determined according to at least one second adhesion rate.

[0121] In an embodiment of the present application, sub-step 22 can include determining a plurality of corresponding second adhesion rates according to vehicle parameters in a plurality of second adhesion states, and selecting the maximum value of the plurality of second adhesion rates as the second target adhesion rate.

[0122] For a plurality of times in the second adhesion state, a plurality of second adhesion rates can be obtained, and then the maximum second adhesion rate can be selected therefrom as the second target adhesion rate.

[0123] Specifically, the second adhesion rate at the later time can be compared with the second adhesion rate at the earlier time, and the greater second adhesion rate is taken as the second target adhesion rate.

[0124] In an embodiment, the second target adhesion rate at a single time point can also be used as the second target adhesion rate.

[0125] In sub-step 23, the road adhesion coefficient is determined according to the first target adhesion rate and the second target adhesion rate.

[0126] After the first target adhesion rate and the second target adhesion rate are obtained, the road adhesion coefficient can be determined according to the first target adhesion rate and the second target adhesion rate.

[0127] In an embodiment of the present application, sub-step 23 can include:

[0128] In sub-step 231, the adhesion rate difference between the first target adhesion rate and the second target adhesion rate is determined.

[0129] After the specific implementation, the difference between the first target adhesion rate and the second target adhesion rate can be calculated to obtain the adhesion rate difference.

[0130] In sub-step 232, in the case where the absolute value of the adhesion rate difference is greater than a preset adhesion rate difference, the first target adhesion rate is determined as the road adhesion coefficient.

[0131] In the case where the absolute value of the adhesion rate difference is greater than the preset adhesion rate difference, the first target adhesion rate can be determined as the road adhesion coefficient, and the preset adhesion rate difference can be in the range of 0.1 to 0.5.

[0132] In sub-step 233, in the case where the absolute value of the adhesion rate difference is less than or equal to the preset adhesion rate difference, the second target adhesion rate is determined as the road adhesion coefficient.

[0133] In the case where the absolute value of the adhesion rate difference is less than or equal to the preset adhesion rate difference, the second target adhesion rate can be determined as the road adhesion coefficient.

[0134] The present application is described below by way of example: Figure 3b The present application is described below by way of example:

[0135] 1. The adhesion state and adhesion rate C of the front axle tire or the rear axle tire, and the corresponding time point t are input.

[0136] 2. The first target adhesion rate a is calculated, and the details are as follows:

[0137] 2.1. It is determined whether the axle torque exceeds the road adhesion capacity. In the first adhesion state, the axle torque exceeds the road adhesion capacity, and in the second adhesion state, the axle torque does not exceed the road adhesion capacity.

[0138] 2.2. In the case where the axle torque exceeds the road adhesion capacity, the first time point t k is recorded, and the t kThe first adhesion rate n at the time t

[0139] 2.3, when the axle torque again exceeds the road adhesion capacity, i.e. when the first adhesion state is entered again, the second time t k+1 .

[0140] 2.4, the time interval t k+1 -t k between the two times is calculated, and it is determined whether the time interval t k+1 -t k is greater than the preset time interval T1, in the case that the time interval t k+1 -t k is greater than the preset time interval T1, the first adhesion rate n at the time t k is taken as the first target adhesion rate a, and in the case that the time interval t k+1 -t k is less than or equal to the preset time interval T1, the first adhesion rate C(k+1) at the time t k+1 is taken as the first target adhesion rate a.

[0141] 3, the second target adhesion rate e is calculated, specifically as follows:

[0142] 3.1, in the case that the axle torque does not exceed the road adhesion capacity, it is determined whether the second adhesion rate C(i) at the later time i is greater than the second adhesion rate C(i-1) at the later time i-1, and then the greater second adhesion rate is taken as the second target adhesion rate e.

[0143] 4, the adhesion rate difference e-a of the first target adhesion rate a and the second target adhesion rate e is calculated, and it is determined whether the absolute value of the adhesion rate difference e-a is greater than the preset adhesion rate difference K.

[0144] 5, in the case that the absolute value of the adhesion rate difference e-a is greater than the preset adhesion rate difference K, the first target adhesion rate a is taken as the road adhesion coefficient C φmax , and in the case that the absolute value of the adhesion rate difference e-a is less than or equal to the preset adhesion rate difference K, the second target adhesion rate e is taken as the road adhesion coefficient C φmax .

[0145] In the embodiment of the present application, by acquiring the wheel angular velocity, the rate of change of the acceleration of the wheel angular velocity is obtained according to the wheel angular velocity, and the road surface adhesion state of the wheel is judged according to the rate of change of the acceleration of the wheel angular velocity and the threshold value; when the rate of change of the acceleration of the wheel angular velocity is greater than the threshold value, the road surface adhesion state is the first adhesion state; then the first target adhesion rate is determined according to the vehicle parameter in the first adhesion state, and the road surface adhesion coefficient is determined according to the first target adhesion rate, which realizes the early prediction of the tendency of vehicle slip according to the rate of change of the acceleration of the wheel angular velocity, and further calculates the road surface adhesion coefficient by using the vehicle parameter at an earlier time, thereby reducing the hysteresis of the road surface adhesion coefficient calculation, ensuring the accuracy of the road surface adhesion coefficient, and further providing a relatively accurate basis for the corresponding control, thereby ensuring the safe and stable driving of the vehicle.

[0146] With reference to Figure 4 , a step flow chart of a torque control method provided by an embodiment of the present application is shown, which can specifically include the following steps:

[0147] Step 401: acquiring the wheel angular velocity, and obtaining the rate of change of the acceleration of the wheel angular velocity according to the wheel angular velocity.

[0148] For the description of step 401, reference can be made to the description of step 201 above.

[0149] Step 402: judging the road surface adhesion state of the wheel according to the rate of change of the acceleration of the wheel angular velocity and the threshold value; when the rate of change of the acceleration of the wheel angular velocity is greater than the threshold value, the road surface adhesion state is the first adhesion state; when the rate of change of the acceleration of the wheel angular velocity is less than or equal to the threshold value, the road surface adhesion state is the second adhesion state.

[0150] For the description of step 402, reference can be made to the description of step 202 and sub-step 21 above.

[0151] In an embodiment of the present application, the method can further include: acquiring the road surface adhesion coefficient; and determining the adhesion ability equivalent torque of the road surface according to the road surface adhesion coefficient.

[0152] In the specific implementation, reference can be made to the acquisition of the road surface adhesion coefficient in the description of step 103 above, and then the adhesion ability equivalent torque of the road surface can be determined according to the road surface adhesion coefficient.

[0153] In an embodiment of the present application, the determination of the adhesion ability equivalent torque of the road surface according to the road surface adhesion coefficient can include: acquiring the axle load and the wheel rolling radius; and determining the adhesion ability equivalent torque of the road surface according to the axle load, the wheel rolling radius, and the road surface adhesion coefficient.

[0154] In a specific implementation, the wheel rolling radius can be acquired first, and the front axle load and the rear axle load can be calculated, and then the road adhesion coefficient can be converted into the road adhesion capacity equivalent torque by using the wheel rolling radius and the axle load. The following formula can be used:

[0155] T fmax =C φmax1 F z1 r t

[0156] T rmax =C φ2max2 F z2 r t

[0157] wherein T fmax , T rmax are the front axle and the rear axle adhesion capacity equivalent torques respectively, C φ1 , C φ2 are the front axle and the rear axle road adhesion coefficients respectively, F z1 , F z2 are the front axle and the rear axle loads respectively, and r t is the wheel rolling radius.

[0158] For the axle load, the following formula can be used:

[0159]

[0160] wherein F z1 , F z2 are the front axle and the rear axle loads respectively, M is the vehicle mass, g is the gravity acceleration, a is the front axle distance, b is the rear axle distance, L is the vehicle wheelbase, and h g is the vehicle mass center height.

[0161] Step 403, in the first adhesion state, the motor torque corresponding to the wheel is controlled to be reduced until the road adhesion state enters the second adhesion state.

[0162] In the first adhesion state, that is, the current motor torque provided to the wheel exceeds the road adhesion capacity, the motor torque corresponding to the wheel can be controlled to be reduced until the road adhesion state enters the second adhesion state. For example, the motor torque can be reduced in steps with a value range of -200 Nm to -10 Nm.

[0163] Step 404, in the second adhesion state, the motor torque corresponding to the wheel is controlled to be increased until the road adhesion state enters the first adhesion state.

[0164] In the second adhesion state, if 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.

[0165] In an embodiment of the present application, step 404 can include:

[0166] In the second adhesion state, if the current torque is less than the adhesion capacity equivalent torque and the absolute value of the torque difference between the current torque and the adhesion capacity equivalent torque is greater than a first preset torque difference, the adhesion capacity equivalent torque is increased by the first preset torque difference as a first step until the absolute value of the torque difference between the adhesion capacity equivalent torque and the current torque is less than or equal to the first preset torque difference.

[0167] In the case where the current torque is less than the adhesion capacity equivalent torque, the absolute value of the torque difference between the current torque and the adhesion capacity equivalent torque can be calculated. When the absolute value of the torque difference is greater than the first preset torque difference, i.e., the difference between the current torque and the adhesion capacity equivalent torque is large, the adhesion capacity equivalent torque is increased by the first preset torque difference as a first step, gradually approaching the adhesion capacity equivalent torque.

[0168] In the case where the absolute value of the torque difference is less than or equal to the first preset torque difference, i.e., the difference between the current torque and the adhesion capacity equivalent torque is small, the adhesion capacity equivalent torque can be directly used as the motor output torque to control the torque to increase.

[0169] In the case where the absolute value of the torque difference is less than or equal to the first preset torque difference, i.e., the difference between the current torque and the adhesion capacity equivalent torque is small, the adhesion capacity equivalent torque can be directly used as the motor output torque to control the torque to increase.

[0170] In the case where the absolute value of the torque difference is less than or equal to the first preset torque difference, i.e., the difference between the current torque and the adhesion capacity equivalent torque is small, the adhesion capacity equivalent torque can be directly used as the motor output torque to control the torque to increase.

[0171] The second step length can be less than the first step length.

[0172] After the adhesion capacity equivalent torque is used as the motor output torque, the road adhesion state can be detected again to determine whether it enters the first adhesion state from the second adhesion state. If yes, the torque is controlled in the manner of the first adhesion state. If no, the torque can be controlled to continue to increase at a smaller second step length.

[0173] The present application is described below in conjunction with Figure 5 The present application is described below in conjunction with

[0174] 1. The current shaft torque requirement T_req increases in step 0, where Step 0 can range from 10Nm to 100Nm. At time K, the actual torque of the motor (i.e., the current torque) is T_actl, and the adhesion capacity equivalent torque is T_max.

[0175] 2. Determine whether the axle torque exceeds the road surface adhesion capacity. If the axle torque exceeds the road surface adhesion capacity, it is in the first adhesion state. If the axle torque does not exceed the road surface adhesion capacity, it is in the second adhesion state.

[0176] 3. When the axle torque exceeds the road surface adhesion capacity, i.e. in the first adhesion state, the torque is reduced with Step2 as the step size. Step2 can be in the range of -200Nm to -10Nm, i.e. T_req(k+1)=T_req(k)+step2.

[0177] 4. When the axle torque does not exceed the road surface adhesion capacity, i.e. in the second adhesion state, calculate the absolute value of the torque difference T_actl-T_max between the current torque T_actl and the adhesion capacity equivalent torque T_max, and determine whether the absolute value of the torque difference T_actl-T_max is less than the first preset torque difference value Step0.

[0178] 5. If the absolute value of the torque difference T_actl-T_max is greater than the first preset torque difference Step0, continue to increase the torque with Step0 as the step size.

[0179] 6. If the absolute value of the torque difference T_actl-T_max is less than or equal to the first preset torque difference Step0, the adhesion capacity equivalent torque can be directly used as the motor output torque, i.e., T_req(k+1)=T_max.

[0180] 7. After using the equivalent torque of the adhesion capacity as the motor output torque, it can be determined again whether the shaft torque exceeds the road adhesion capacity. If the shaft torque exceeds the road adhesion capacity, it enters the first adhesion state, and torque control can be performed according to the first adhesion state. If the shaft torque does not exceed the road adhesion capacity, it does not enter the first adhesion state, and torque can be increased by a smaller second step size Step1. The value range of Step1 can be from 10Nm to 100Nm.

[0181] In the embodiment of the present application, by acquiring the wheel angular velocity, the rate of change of the acceleration of the wheel angular velocity is obtained according to the wheel angular velocity, and the road surface adhesion state of the wheel is judged according to the rate of change of the acceleration of the wheel angular velocity and the threshold value, when the rate of change of the acceleration of the wheel angular velocity is greater than the threshold value, the road surface adhesion state is the first adhesion state, and when the rate of change of the acceleration of the wheel angular velocity is less than or equal to the threshold value, the road surface adhesion state is the second adhesion state, then the motor torque corresponding to the wheel can be controlled to decrease in the first adhesion state until the road surface adhesion state enters the second adhesion state, and the motor torque corresponding to the wheel is controlled to increase in the second adhesion state until the road surface adhesion state enters the first adhesion state, so that the torque control is realized according to the adhesion state of the wheel on the road surface, the torque tends to approach the adhesion capacity of the road surface, the accuracy of the torque control is improved, and the safe and stable driving of the vehicle is ensured.

[0182] The beneficial effects of the present application are described below Figure 6a and Figure 6b The beneficial effects of the present application are described below

[0183] As Figure 6a In the case of controlling the axle torque demand T with the equivalent torque of the adhesion capacity of the road surface as the torque reference value, as Figure 6b In the case of not controlling the axle torque demand T with the equivalent torque of the adhesion capacity of the road surface as the torque reference value, it can be seen that in the case of controlling the axle torque demand T with the equivalent torque of the adhesion capacity of the road surface as the torque reference value, the following beneficial effects are achieved:

[0184] 1. In the torque increasing stage, the equivalent axle torque of the adhesion capacity of the road surface is taken as the increasing torque reference value of the front axle torque and the rear axle torque, and after the maximum torque increasing rate reaches the reference value, the torque increasing rate is adjusted, which can effectively reduce the response time compared with the general way of limiting the torque increasing step.

[0185] 2. After the torque control is reduced to the stable state of the vehicle, the torque recovery stage is entered, and the equivalent axle torque of the adhesion capacity of the road surface calculated is taken as the increasing torque reference value of the front axle motor and the rear axle motor, which avoids the torque uncontrolled increase causing the wheel to slip again and triggering the torque reduction control.

[0186] In the prior art, whether the wheel slips is judged according to the difference between the actual slip rate and the preset slip rate, and the judgment result of the wheel slip can be obtained only after the wheel speed rises to the occurrence of the wheel slip. The present application judges the wheel slip trend (mechanical critical point) according to the mechanical equation of the wheel contact point with the ground, and the judgment result is obtained when the wheel does not slip but the motor torque actually exceeds the torque that can be borne by the road surface. Therefore, the calculation method of the adhesion coefficient in the present application is more accurate. In addition, the torque is controlled according to the slip rate, and due to the hysteresis of the judgment, the torque range to be adjusted from the slip state to the normal state is larger, and the time required is longer (seeFigure 6b ).

[0187] The torque control method of this invention controls torque based on slippage trends, namely, a first adhesion state and a second adhesion state. In the first adhesion state, i.e., when slippage is likely, the torque is promptly reduced to avoid slippage risk. After reducing the torque to transition from the first adhesion state to the second adhesion state, the torque is increased again until the wheel re-enters the first adhesion state. In other words, torque control ensures that the wheel's adhesion state on the road surface is adjusted accordingly: after transitioning from the first to the second adhesion state, the torque is promptly increased to return to the first adhesion state; and after transitioning from the second to the first adhesion state, the torque is promptly reduced to return to the second adhesion state. This results in a shorter dwell time for the wheel's road surface adhesion state between the first and second adhesion states, thus limiting the torque control range. Specifically, this means the torque fluctuates within a small range of the equivalent axle torque of the road surface adhesion capability (see [link to relevant documentation]). Figure 6a This improves the vehicle's driving stability. Furthermore, because the wheels have a tendency to slip in the initial adhesion state, but slippage does not occur, the vehicle's driving safety is also guaranteed.

[0188] It should be noted that, for the sake of simplicity, the method embodiments are all described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.

[0189] Reference Figure 7 The diagram shows a structural block diagram of a road surface adhesion coefficient estimation device according to an embodiment of the present invention, which may specifically include the following modules:

[0190] The first rate of change determination module 701 is used to obtain the wheel angular velocity and obtain the rate of change of the wheel angular velocity acceleration based on the wheel angular velocity.

[0191] The first road surface adhesion state determination module 702 is used to determine the road surface adhesion state of the wheel based on the rate of change of the wheel angular velocity acceleration and a threshold; wherein, when the rate of change of the wheel angular velocity acceleration is greater than the threshold, the road surface adhesion state is the first adhesion state.

[0192] The road surface adhesion coefficient determination module 703 is used to determine a first target adhesion rate based on the vehicle parameters under the first adhesion state, and to determine the road surface adhesion coefficient based on the first target adhesion rate.

[0193] In one embodiment of the present invention, the road surface adhesion coefficient determination module 703 may include:

[0194] Multiple first adhesion rate determination submodules are used to determine multiple first adhesion rates based on vehicle parameters under multiple first adhesion states;

[0195] Multiple first adhesion rate determination target adhesion rate submodules are used to determine a first target adhesion rate based on multiple first adhesion rates.

[0196] In one embodiment of the present invention, a plurality of first adhesion rate determination target adhesion rate submodules may include:

[0197] The time interval determination unit is used to acquire the first moment and the second moment of two adjacent first attachment states, and determine the time interval based on the first moment and the second moment, wherein the first moment is earlier than the second moment;

[0198] The attachment rate at the first moment is used as the target unit, and when the time interval is greater than the preset time interval, the first attachment rate of the first attachment state corresponding to the first moment is used as the first target attachment rate.

[0199] The attachment rate at the second moment is used as the target unit, and when the time interval is less than or equal to the preset time interval, the first attachment rate of the first attachment state corresponding to the second moment is used as the first target attachment rate.

[0200] In one embodiment of the present invention, the road surface adhesion coefficient determination module 703 includes:

[0201] The first target adhesion rate is determined as the road surface adhesion coefficient unit, which is used to determine the first target adhesion rate as the road surface adhesion coefficient.

[0202] In one embodiment of the present invention, the road surface adhesion coefficient determination module 703 includes:

[0203] The second adhesion rate determination unit is used to determine the second adhesion rate based on vehicle parameters under the second adhesion state; wherein, when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold, the road surface adhesion state is the second adhesion state.

[0204] The second target adhesion rate determination unit is used to determine the second target adhesion rate based on at least one second adhesion rate.

[0205] Combined with the second target adhesion rate determination unit, it is used to determine the road surface adhesion coefficient based on the first target adhesion rate and the second target adhesion rate.

[0206] In one embodiment of the present invention, the second target adhesion rate determination unit may include:

[0207] The difference value determination sub-unit is configured to determine a difference value of the first target adhesion rate and the second target adhesion rate.

[0208] The first target adhesion rate determination sub-unit is configured to determine the first target adhesion rate as a road adhesion coefficient when the absolute value of the difference value is greater than a preset adhesion rate difference value.

[0209] The second target adhesion rate determination sub-unit is configured to determine the second target adhesion rate as a road adhesion coefficient when the absolute value of the difference value is less than or equal to the preset adhesion rate difference value.

[0210] In an embodiment of the present application, the second target adhesion rate determination unit is specifically configured to:

[0211] determine a plurality of 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 the second target adhesion rate.

[0212] Referring to Figure 8 , a structural block diagram of a device for torque control is shown, which can specifically include the following modules:

[0213] The second change rate determination module 801 is configured to obtain a wheel angular velocity, and obtain a change rate of acceleration of the wheel angular velocity according to the wheel angular velocity.

[0214] The second road adhesion state judgment module 802 is configured to judge a road adhesion state of a wheel according to the change rate of acceleration of the wheel angular velocity and a threshold value; when the change rate of acceleration of the wheel angular velocity is greater than the threshold value, the road adhesion state is a first adhesion state; when the change rate of acceleration of the wheel angular velocity is less than or equal to the threshold value, the road adhesion state is a second adhesion state.

[0215] The first adhesion state torque control module 803 is configured to control a motor torque corresponding to the wheel to decrease in the first adhesion state until the road adhesion state enters the second adhesion state.

[0216] The second adhesion state torque control module 804 is configured 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.

[0217] In an embodiment of the present application, the device can further include:

[0218] The road adhesion coefficient acquisition module is configured to acquire a road adhesion coefficient.

[0219] The attachment capacity equivalent torque determination module is configured to determine the attachment capacity equivalent torque of the road surface according to the road surface attachment coefficient.

[0220] In an embodiment of the present application, the torque control module 804 in the second attachment state can include:

[0221] The first-step-size increasing submodule is configured to, in the second attachment state, if the current torque is less than the attachment capacity equivalent torque and the absolute value of the torque difference between the current torque and the attachment capacity equivalent torque is greater than a first preset torque difference value, increase the attachment capacity equivalent torque by the first preset torque difference value as a first step size until the absolute value of the torque difference between the attachment capacity equivalent torque and the current torque is less than or equal to the first preset torque difference value.

[0222] The attachment capacity equivalent torque output submodule is configured to, if the current torque is less than the attachment capacity equivalent torque and the torque difference between the current torque and the attachment capacity equivalent torque is less than or equal to the first preset torque difference value, take the attachment capacity equivalent torque as the motor output torque.

[0223] The second-step-size increasing submodule is configured to, after taking the attachment capacity equivalent torque as the motor output torque, if the road surface attachment state is still the second attachment state, gradually increase the motor output torque by a second step size until the road surface attachment state enters the first attachment state.

[0224] The second step size is less than the first step size.

[0225] In an embodiment of the present application, the attachment capacity equivalent torque determination module can include:

[0226] The axle load and radius acquisition submodule is configured to acquire the axle load and the wheel rolling radius.

[0227] The axle load and radius combination and determination submodule is configured to determine the attachment capacity equivalent torque of the road surface according to the axle load, the wheel rolling radius, and the road surface attachment coefficient.

[0228] In an embodiment of the present application, acquiring the road surface attachment coefficient includes referring to the estimation device of the road surface attachment coefficient as described above.

[0229] An embodiment of the present application further provides an electronic device, which can include a processor, a memory, and a computer program stored on the memory and capable of running on the processor, and the computer program is executed by the processor to implement the estimation method of the road surface attachment coefficient or the torque control method as described above.

[0230] An embodiment of the present application also provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the road adhesion coefficient estimation method or the torque control method.

[0231] For the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant part can be referred to the part of the method embodiment.

[0232] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of estimating a road adhesion coefficient, characterized by, The method comprises: obtaining wheel angular velocity, and obtaining a rate of change of acceleration of the wheel angular velocity according to the wheel angular velocity; judging a road surface adhesion state of the wheel according to the rate of change of acceleration of the wheel angular velocity and a threshold value; when the rate of change of acceleration of the wheel angular velocity is greater than the threshold value, the road surface adhesion state is a first adhesion state; determining a first target adhesion rate according to vehicle parameters in the first adhesion state, and determining a road surface adhesion coefficient according to the first target adhesion rate, comprising: determining a second adhesion rate according to vehicle parameters in a second adhesion state; when the rate of change of acceleration of the wheel angular velocity is less than or equal to the threshold value, the road surface adhesion state is the second adhesion state; determining a second target adhesion rate according to at least one second adhesion rate; and determining the road surface adhesion coefficient according to the first target adhesion rate and the second target adhesion rate.

2. The method of claim 1, wherein, The determination of the first target adhesion rate according to the vehicle parameters in the first adhesion state comprises: determining a plurality of first adhesion rates according to a plurality of vehicle parameters in the first adhesion state; determining the first target adhesion rate according to a plurality of the first adhesion rates.

3. The method of claim 2, wherein, The determination of the first target adhesion rate according to a plurality of the first adhesion rates comprises: obtaining a first time and a second time in adjacent first adhesion states, and determining a time interval according to the first time and the second time, the first time being earlier than the second time; when the time interval is greater than a preset time interval, taking a first adhesion rate in the first adhesion state corresponding to the first time as the first target adhesion rate; when the time interval is less than or equal to the preset time interval, taking a first adhesion rate in the first adhesion state corresponding to the second time as the first target adhesion rate.

4. The method according to any one of claims 1 to 3, characterized in that, The determination of the road surface adhesion coefficient according to the first target adhesion rate comprises: taking the first target adhesion rate as the road surface adhesion coefficient.

5. The method of claim 1, wherein, The determination of the road surface adhesion coefficient according to the first target adhesion rate and the second target adhesion rate comprises: determining an adhesion rate difference between the first target adhesion rate and the second target adhesion rate; when an absolute value of the adhesion rate difference is greater than a preset adhesion rate difference, taking the first target adhesion rate as the road surface adhesion coefficient; when the absolute value of the adhesion rate difference is less than or equal to the preset adhesion rate difference, taking the second target adhesion rate as the road surface adhesion coefficient.

6. The method of claim 5, wherein, The determination of the second target adhesion rate according to at least one second adhesion rate comprises: determining a plurality of corresponding second adhesion rates according to a plurality of vehicle parameters in the second adhesion state, and selecting a maximum value of the plurality of second adhesion rates as the second target adhesion rate.

7. A method of torque control, characterized by, The method comprises: obtaining wheel angular velocity, and obtaining a rate of change of acceleration of the wheel angular velocity according to the wheel angular velocity; judging a road surface adhesion state of the wheel according to the rate of change of acceleration of the wheel angular velocity and a threshold value; when the rate of change of acceleration of the wheel angular velocity is greater than the threshold value, the road surface adhesion state is a first adhesion state; when the rate of change of acceleration of the wheel angular velocity is less than or equal to the threshold value, the road surface adhesion state is a second adhesion state; In the first adhesion state, the motor torque corresponding to the wheel is controlled to decrease until the road adhesion state enters the second 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.

8. The method of claim 7, wherein, The method further comprises: obtaining a road adhesion coefficient; determining an adhesion capacity equivalent torque of the road according to the road adhesion coefficient.

9. The method of claim 8, wherein, The control of the motor torque corresponding to the wheel in the second adhesion state to increase until the road adhesion state enters the first adhesion state comprises: In the second adhesion state, if the current torque is less than the adhesion capacity equivalent torque and the absolute value of the torque difference between the current torque and the adhesion capacity equivalent torque is greater than a first preset torque difference, the adhesion capacity equivalent torque is increased by the first preset torque difference as a first step until the absolute value of the torque difference between the adhesion capacity equivalent torque and the current torque is less than or equal to the first preset torque difference; 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 the first preset torque difference, the adhesion capacity equivalent torque is taken as the motor output torque; After the adhesion capacity equivalent torque is taken as the motor output torque, if the road adhesion state is still the second adhesion state, the motor output torque is gradually increased by a second step until the road adhesion state enters the first adhesion state; The second step is less than the first step.

10. The method according to claim 8 or 9, characterized in that, The determination of the adhesion capacity equivalent torque of the road according to the road adhesion coefficient comprises: obtaining an axle load and a wheel rolling radius; determining the adhesion capacity equivalent torque of the road according to the axle load, the wheel rolling radius, and the road adhesion coefficient.

11. The method of claim 8, wherein, The method for obtaining the road adhesion coefficient comprises the method according to any one of claims 1-6.

12. An apparatus for estimating a road adhesion coefficient, characterized by The device comprises: a first change rate determination module configured to obtain a wheel angular velocity and determine a change rate of the acceleration 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 according to the change rate of the acceleration of the wheel angular velocity and a threshold value; when the change rate of the acceleration of the wheel angular velocity is greater than the threshold value, the road adhesion state is the first adhesion state; a road adhesion coefficient determination module configured to determine a first target adhesion rate according to the vehicle parameters in the first adhesion state and determine the road adhesion coefficient according to the first target adhesion rate, comprising: a second adhesion rate determination unit configured to determine a second adhesion rate according to the vehicle parameters in the second adhesion state; when the change rate of the acceleration of the wheel angular velocity is less than or equal to the threshold value, the road adhesion state is the second adhesion state; a second target adhesion rate determination unit configured to determine a second target adhesion rate according to at least one second adhesion rate; and a combination unit configured to determine the road adhesion coefficient according to the first target adhesion rate and the second target adhesion rate.

13. A device for torque control, characterized in that The device comprises: a second change rate determination module configured to obtain a wheel angular velocity and determine a change rate of the acceleration of the wheel angular velocity according to the wheel angular velocity; A second road adhesion state judging module is configured to judge the road adhesion state of the wheel according to 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 the 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 or equal to the threshold value, the road adhesion state is a second adhesion state; A first adhesion state torque control module is configured to control the motor torque corresponding to the wheel to decrease in the first adhesion state until the road adhesion state enters the second adhesion state; A second adhesion state torque control module is configured 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.

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