A method for calibrating electric vehicle braking

Abstract

The application relates to the technical field of automobile control, and provides a brake calibration method for an electric automobile, which comprises the following steps: S1, sampling speed values according to a set step length in a speed range, and calculating maximum reverse drag torques T1 corresponding to all speed values; S2, selecting a speed value, determining expected reverse drag torques T2 under different brake pedal opening degrees at the current speed value, and outputting the smaller value in the maximum reverse drag torque T1 and the expected reverse drag torque T2; S3, based on the output reverse drag torque T f calculating a current wheel end resistance F m of the vehicle based on the resistance received by the whole vehicle, calculating a deceleration a of the vehicle, adjusting the expected reverse drag torque T2 corresponding to each brake pedal opening degree at the current speed based on the deceleration a until the deceleration a of the vehicle reaches an expected deceleration a 期 , and executing the step S2. When the vehicle is controlled based on the expected reverse drag torque, the driving and riding stability of the vehicle during braking is improved, that is, the driving and riding comfort of the driver and passengers is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of brake control and provides an electric vehicle brake calibration method. BACKGROUND

[0002] With the diversification of the development of automobile technology, while the traditional fuel vehicles are widely popularized, the problems of energy shortage and air pollution are increasingly highlighted. Under the premise of the above two problems, countries around the world are developing new energy vehicles to solve the two problems of energy shortage and environmental pollution. At present, the pure electric vehicles developed rapidly in China have been recognized by relevant persons and the first pure electric vehicle has been purchased. Whether traditional fuel vehicles or pure electric vehicles, energy saving and improvement of the driving comfort of vehicles are common goals of technology development.

[0003] The current brake of the electric vehicle is realized by the reverse drag of the motor. While braking, the function of energy recovery can be realized, but it will also affect the driving comfort of the driver and the passenger. SUMMARY

[0004] The application provides an electric vehicle brake control method, which aims to improve the driving comfort of the driver and the passenger.

[0005] The application is realized by an electric vehicle brake calibration method, which specifically comprises the following steps:

[0006] S1, sampling speed values in a speed interval according to a set step length, and calculating maximum reverse drag torques T1 corresponding to all speed values;

[0007] S2, selecting a speed value, determining expected reverse drag torques T2 under different brake pedal opening degrees at the current speed value, and outputting the smaller value in the maximum reverse drag torque T1 and the expected reverse drag torque T2;

[0008] S3, adjusting the reverse drag torque T f calculating the current wheel end resistance F m of the vehicle, and calculating the deceleration a of the vehicle based on the resistance received by the whole vehicle;

[0009] S4, adjusting the expected reverse drag torque T2 corresponding to each brake pedal opening degree at the current speed based on the deceleration a until the deceleration a of the vehicle reaches the expected deceleration a 期 , completing the calibration of the expected reverse drag torque of the current speed value, and performing step S2 until the calibration of the expected reverse drag torque of all speed values is completed.

[0010] Further, the determination method of the maximum reverse drag torque T1 is specifically as follows:

[0011] S11, calculating the motor speed n based on the vehicle speed v;

[0012] S12, determine the corresponding reverse drag torque of the rotation speed based on the motor external characteristic curve, that is, the maximum reverse drag torque T1.

[0013] Further, the determination method of the expected reverse drag torque T2 is as follows:

[0014] Sampling the brake pedal opening value according to the set step in the opening interval of the brake pedal;

[0015] Calibrating the expected reverse drag torque T2 under each brake pedal opening value at the current vehicle speed value.

[0016] Further, the resistance F of the whole vehicle is the sum of the current wheel end resistance F m , the coasting resistance F h and the braking force F Z .

[0017] Further, the coasting resistance F h is obtained as follows:

[0018] S41, obtaining the coasting resistance F h of the vehicle at different speeds based on the bench test or software simulation;

[0019] S42, fitting the coasting resistance F h at different speeds to obtain a speed-coasting resistance curve;

[0020] S43, reading the coasting resistance value corresponding to the current speed from the speed-coasting resistance curve.

[0021] Further, the adjustment method of the expected reverse drag torque T2 corresponding to each brake pedal opening at the current speed is as follows:

[0022] If the deceleration a is greater than the expected deceleration a 期 , the expected reverse drag torque T2 corresponding to the vehicle speed and the brake pedal opening is reduced, and if the current deceleration a is less than the expected deceleration a 期 , the expected reverse drag torque T2 corresponding to the vehicle speed and the brake pedal opening is increased.

[0023] Further, the calculation formula of the wheel end resistance F m is as follows:

[0024] F m = T f *I g *η / r;

[0025] Wherein, r is the rolling radius of the tire, I g is the speed ratio, η is the transmission system efficiency, and T f is the current output motor reverse drag torque.

[0026] Further, the output reverse drag torque T f The determination method is specifically as follows:

[0027] If the expected reverse drag torque T2 is less than the maximum reverse drag torque T1, the current output reverse drag torque T f is equal to the expected reverse drag torque T2, and if the expected reverse drag torque T2 is greater than the maximum reverse drag torque T1, the current output reverse drag torque T f is the maximum reverse drag torque T1.

[0028] Further, after step S4, the method further comprises:

[0029] After the expected reverse drag torque at all speed values is calibrated, the expected reverse drag torque is stored in the electric vehicle in the form of a table.

[0030] The current expected reverse drag torque is determined based on the current speed value and the brake pedal opening degree of the vehicle, and the output torque of the motor is controlled based on the expected reverse drag torque.

[0031] When the vehicle is controlled based on the expected reverse drag torque, the driving stability of the vehicle during braking is improved, that is, the driving comfort of the driver and the passenger is improved. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A flowchart of a calibration method of an electric vehicle brake is provided for the embodiment of the present application. DETAILED DESCRIPTION

[0033] The specific embodiments of the present application will be further described in detail below with reference to the drawings.

[0034] Figure 1 A flowchart of a calibration method of an electric vehicle brake is provided for the embodiment of the present application. The method specifically comprises the following steps:

[0035] S1, sampling speed values according to a set step in a speed interval, and calculating the maximum reverse drag torque T1 corresponding to all speed values.

[0036] In the embodiment of the present application, the determination method of the maximum reverse drag torque T1 is specifically as follows:

[0037] S11, calculating the motor speed n based on the current speed v, and the calculation formula is specifically as follows: v = 0.377 * n * r / I g , r is the rolling radius of the tire, and I g is the speed ratio;

[0038] S12, determining the reverse drag torque corresponding to the current speed based on the motor external characteristic curve, which is the maximum reverse drag torque T1.

[0039] S2, select a speed value, determine the expected reverse drag torque T2 under different brake pedal opening degree under the current vehicle speed value, output the smaller value of the maximum reverse drag torque T1 and the expected reverse drag torque T2;

[0040] If the expected reverse drag torque T2 is less than the maximum reverse drag torque T1, the current output reverse drag torque T f is equal to the expected reverse drag torque T2, and if the expected reverse drag torque T2 is greater than the maximum reverse drag torque T1, the current output reverse drag torque T f is the maximum reverse drag torque T1.

[0041] In the embodiment of the present application, the determination method of the expected reverse drag torque T2 is as follows:

[0042] The brake pedal opening degree value is sampled according to the set step in the opening interval of the brake pedal; the expected reverse drag torque T2 under each brake pedal opening degree value is calibrated at the current vehicle speed value.

[0043] S3, based on the output reverse drag torque T f , the current wheel end resistance F m of the vehicle is calculated;

[0044] In the embodiment of the present application, the calculation formula of the wheel end resistance F m is as follows:

[0045] F m = T f *I g *η / r;

[0046] Wherein, r is the rolling radius of the tire, I g is the speed ratio, η is the transmission system efficiency, T f is the current output motor reverse drag torque.

[0047] In the embodiment of the present application, the resistance F of the whole vehicle is the sum of the current wheel end resistance F m , the sliding resistance F h and the braking force F Z , the resistance F of the whole vehicle is F m +F h +F Z , the current vehicle deceleration a=F / M, M is the whole vehicle weight, wherein the braking force F Z is calculated based on the brake pedal opening degree, the sliding resistance F h is related to the speed, wherein the sliding resistance F h is obtained as follows:

[0048] S31, based on the bench test or software simulation, the sliding resistance Fh ;

[0049] S32, reading the coasting resistance value corresponding to the current speed from the speed-coasting resistance curve. h h 2

[0050] S33, reading the coasting resistance value corresponding to the current speed from the speed-coasting resistance curve.

[0051] S4, adjusting the expected negative and reverse drag torque T2 corresponding to each brake pedal opening at the current speed based on the deceleration a until the deceleration a of the vehicle reaches the expected deceleration a 期 , completing the calibration of the expected reverse drag torque at the current speed value, performing step S2 to start the calibration of the expected reverse drag torque at the next speed value until the calibration of the expected reverse drag torque at all speed values is completed, and storing the table in the electric vehicle after the calibration of the expected reverse drag torque at all speed values is completed, determining the expected reverse drag torque at the current speed and the current brake pedal opening based on the above table, and outputting the torque by the electric vehicle based on the expected reverse drag torque, thereby improving the driving stability of the vehicle during braking and improving the driving comfort of the driver and the passengers.

[0052] In the embodiment of the present application, the adjustment method of the expected negative and reverse drag torque T2 corresponding to each brake pedal opening at the current speed is as follows: if the deceleration a is greater than the expected deceleration a 期 , the expected negative and reverse drag torque T2 corresponding to the speed value and the brake pedal opening is reduced, and if the current deceleration a is less than the expected deceleration a 期 , the expected negative and reverse drag torque T2 corresponding to the speed value and the brake pedal opening is increased.

[0053] Obviously, the specific implementation of the present application is not limited by the above method, and various non-essential improvements made by adopting the method concept and technical scheme of the present application are within the protection scope of the present application.​​​

Claims

1. A method of electric vehicle brake calibration, the method comprising: The method specifically comprises the following steps: S1, sampling speed values according to a set step length in a speed interval, and calculating maximum reverse drag torque T1 corresponding to all speed values; S2, selecting a speed value, determining expected reverse drag torque T2 under different brake pedal opening degrees at the current speed value, and outputting the smaller value of the maximum reverse drag torque T1 and the expected reverse drag torque T2; S3, output-based counter-torque T f calculating the current wheel-end resistance F of the vehicle m calculating the deceleration a of the vehicle based on the resistance experienced by the vehicle S4, adjusting the expected drag torque T2 corresponding to each brake pedal opening at the current speed based on the deceleration a until the deceleration a of the vehicle reaches the expected deceleration a 期 , completing the calibration of the expected drag torque at the current speed value, performing step S2 until the calibration of the expected drag torque at all speed values is completed; The determination method of the expected reverse drag torque T2 is specifically as follows: Sampling brake pedal opening degree values according to a set step length in an opening degree interval of the brake pedal; Calibrating expected reverse drag torque T2 under each brake pedal opening degree value at the current speed value.

2. The electric vehicle brake calibration method of claim 1, wherein, The determination method of the maximum reverse drag torque T1 is specifically as follows: S11, calculating motor speed n based on vehicle speed v; S12, determining reverse drag torque corresponding to the speed based on the motor external characteristic curve, that is, the maximum reverse drag torque T1.

3. The electric vehicle brake calibration method of claim 1, wherein, The resistance F received by the whole vehicle is the sum of the current wheel end resistance F m , the coasting resistance F h , and the braking force F Z .

4. The method of claim 3, wherein the calibration of the electric vehicle brake is performed by a calibration tool. Sliding resistance F h The acquisition method is specifically as follows: S41, obtain the rolling resistance F of the vehicle at different speeds based on the bench test or software simulation h ; S42, the sliding resistance F at different speeds h Fitting is performed to obtain the speed-sliding resistance curve; S43, reading the current speed corresponding sliding resistance value from the speed-sliding resistance curve.

5. The electric vehicle brake calibration method of claim 1, wherein, The adjustment method of the expected reverse drag torque T2 corresponding to each brake pedal opening degree at the current speed is specifically as follows: If the deceleration a is greater than the desired deceleration a 期 then the desired braking torque T2 at the corresponding vehicle speed and brake pedal opening is reduced, and if the current deceleration a is less than the desired deceleration a 期 then the desired braking torque T2 at the corresponding vehicle speed and brake pedal opening is increased.

6. The electric vehicle brake calibration method of claim 1, wherein, Wheel end resistance F m The calculation formula is as follows: F m = T f I g η / r; where r is the tire rolling radius, I g is the gear ratio, and η is the transmission system efficiency, T f is the current output motor counter drag torque.

7. The electric vehicle brake calibration method of claim 1, wherein, The output counter-torque T f The determination method of the output counter-torque T is specifically as follows: If the desired back-torque T2 is less than the maximum back-torque T1, the current output back-torque T f is equal to the desired back-torque T2, and if the desired back-torque T2 is greater than the maximum back-torque T1, the current output back-torque T f is the maximum back-torque T1.

8. The electric vehicle brake calibration method of claim 1, wherein, After step S4, the following steps are further included: After calibrating the expected reverse drag torque of all speed values, storing in the electric vehicle in the form of a table; Determining the current expected reverse drag torque based on the current speed value and the brake pedal opening degree of the vehicle, and controlling the output torque of the motor based on the expected reverse drag torque.

Images