阅读说明：本技术 一种基于电动汽车电驱系统的扭振控制方法 (Torsional vibration control method based on electric driving system of electric vehicle ) 是由 林雨婷 陈健 刘立 李华 王志斌 蒋飞 陈曦 向阳 于 2021-05-31 设计创作，主要内容包括：本发明公开了一种基于电动汽车电驱系统的扭振控制方法,其利用电机模型转速与电机实际转速的差值乘以抗扭振补偿系数来得到抗扭振补偿扭矩,进而修正电机目标扭矩。电机模型转速为无扭振影响的电机理论转速,将电机实际转速与电机模型转速对比,进而作为修正依据,使电机实际转速尽可能的接近电机模型转速,该修正依据准确,扭矩修正及时,能提高整车的驾驶平顺性。(The invention discloses a torsional vibration control method based on an electric automobile electric driving system, which obtains torsional vibration compensation torque by multiplying the difference value between the model rotating speed and the actual rotating speed of a motor by a torsional vibration compensation coefficient, and further corrects the target torque of the motor. The motor model rotating speed is the theoretical rotating speed of the motor without torsional vibration influence, the actual rotating speed of the motor is compared with the rotating speed of the motor model, and then the actual rotating speed of the motor is used as a correction basis to be close to the rotating speed of the motor model as far as possible, the correction basis is accurate, the torque correction is timely, and the driving smoothness of the whole vehicle can be improved.)

1. A torsional vibration control method based on an electric drive system of an electric vehicle is characterized by comprising the following steps:

read motor model rotational speed MotSpdMod of moment t_(t)Actual rotation speed MotSpd of motor_(t)Actual torque M of motor_(t)Pressure P of brake master cylinder_(t)And the slope of the road on which the vehicle is located_(t)；

According to said slope_(t)And the actual rotational speed MotSpd of the motor_(t)Determining the running resistance at t moment and converting the running resistance into the running resistance moment WR at the motor end_(t)；

According to the pressure P of the brake master cylinder_(t)And the actual rotational speed MotSpd of the motor_(t)Determining the brake master cylinder pressure at the time t and converting the pressure into the brake torque WB at the motor end_(t)；

Using the integral formula of the rotation speed: MotSpdMod_(t+dt)＝MotSpdMod_(t)+(M_(t)-WR_(t)-WB_(t)) XKf x dt, calculating the motor model rotating speed MotSpdMod at the moment of t + dt_(t+dt)And storing; kf is a preset power assembly characteristic correction coefficient, the vehicle is static at the initial moment, the initial value of the rotating speed of the motor model is equal to zero, the initial value of the actual rotating speed of the motor is equal to zero, the initial value of the actual torque of the motor is equal to zero, and the sum of the initial value of the driving resistance torque converted to the motor end by the driving resistance and the initial value of the braking torque converted to the motor end by the pressure of the brake master cylinder is equal to zero;

obtaining the actual rotating speed MotSpd of the motor at the moment of t + dt_(t+dt)Actual torque M of motor_(t+dt)Pressure P of brake master cylinder_(t+dt)And slope of road on which vehicle is located_(t+dt)And storing;

according to the actual rotating speed MotSpd of the motor_(t+dt)Actual torque M of motor_(t+dt)Inquiring a rotating speed-torque-torsional vibration resistance compensation coefficient table to obtain a corresponding torsional vibration resistance compensation coefficient k_(t+dt)(ii) a The rotating speed-torque-torsional vibration compensation coefficient table is a pre-stored corresponding relation table of the actual rotating speed of the motor, the actual torque of the motor and the torsional vibration compensation coefficient;

using the formula for torsional vibration compensation torque: TC (tungsten carbide)_(t+dt)＝k_(t+dt)×(MDtSpdMod_(t+dt)-MotSpd_(t+dt)) And calculating to obtain the torsional vibration compensation torque TC at the moment of t + dt_(t+dt)；

Compensating torque TC for torsional vibration at the moment of t + dt_(t+dt)And superposing the target torque with the original target torque of the motor to obtain the corrected target torque of the motor at the moment of t + dt.

2. Method for torsional vibration control based on an electric vehicle electric drive system according to claim 1, characterized in that the gradient slope is dependent on_(t)And the actual rotational speed MotSpd of the motor_(t)Determining the running resistance at t moment and converting the running resistance into the running resistance moment WR at the motor end_(t)The specific mode is as follows:

according to said slope_(t)Inquiring a gradient-fitting parameter table to obtain a specific numerical value of the corresponding fitting parameter A, B, C; wherein, the gradient-fitting parameter table is a pre-stored corresponding relation table of the gradient of the road where the vehicle is located and the fitting parameter A, B, C;

the corresponding specific value of the fitting parameter A, B, C and the actual rotating speed MotSpd of the motor_(t)And carrying in a running resistance moment calculation formula: WR (pulse Width modulation)_(t)＝A×MotSpd_(t) ²+B×MotSpd_(t)+ C, calculating the running resistance at t moment and converting the running resistance into the running resistance moment WR at the motor end_(t)。

3. Method for controlling torsional vibrations based on an electric drive system of an electric vehicle according to claim 1 or 2, characterized in that it is based on the brake master cylinder pressure P_(t)And the actual rotational speed MotSpd of the motor_(t)Determining the brake master cylinder pressure at the time t and converting the pressure into the brake torque WB at the motor end_(t)The specific mode is as follows:

if the actual speed MotSpd of the motor_(t)Is less than or equal to the preset rotation speed threshold Mthre, the vehicle is stationary, and WB is enabled_(t)＝-WR_(t)；

If the actual speed MotSpd of the motor_(t)If the absolute value of (b) is greater than the preset rotation speed threshold value Mthre, it indicates that the vehicle is moving, and WB is made_(t)＝sign×K_b×P_(t)；

Wherein, when MotSpd_(t)When > 0, sign is 1, when MotSpd_(t)When < 0, sign is-1, K_bThe method is a preset conversion coefficient for converting the pressure of the brake master cylinder to the braking torque of the motor end.

4. The method of claim 2 or 3, wherein the slope-fit parameter table is obtained by testing:

firstly, enabling the vehicle to run at a constant speed at different speeds on the same slope, and recording the actual motor torque M at t moment corresponding to different speeds on the slope after the actual motor torque and the actual motor rotating speed are stable_(t)And the actual rotating speed MotSpd of the motor_(t)(ii) a Wherein, under the condition of constant-speed running of the vehicle, the running resistance at the time t is converted into the running resistance moment WR of the motor end_(t)Actual torque M of motor equal to t moment_(t)；

Secondly, the actual rotating speed MotSpd of the motor at the t moment corresponding to different vehicle speeds under the slope_(t)Converted to a driving resistance torque WR at the motor end from the driving resistance_(t)And fitting a quadratic function to obtain a running resisting moment calculation formula: WR (pulse Width modulation)_(t)＝A×MotSpd_(t) ²+B×MotSpd_(t)+ C; then extracting fitting parameters A, B, C to obtain a group of fitting parameters A, B, C;

step three, changing the gradient for n-1 times, and then repeatedly executing the step one and the step two until n groups of fitting parameters A, B, C are obtained;

and fourthly, corresponding n groups of fitting parameters A, B, C to n gradients one by one to form the gradient-fitting parameter table.

5. The method of claim 4, wherein the predetermined powertrain characteristic correction factor Kf is obtained by testing:

the vehicle is enabled to run on a flat road at uniform acceleration, and the actual torque of the motor at m moments in the process of running at uniform acceleration is recordedActual rotating speed of motor at m moments Wherein, under the condition of uniform acceleration running of the vehicle, the motor model rotating speed at m moments Respectively equal to the actual rotational speed of the motor at the corresponding moment The pressure of the brake master cylinder at m moments is converted into the braking torque of the motor endAre all equal to zero;

fitting parameters A, B, C corresponding to the flat road and the actual rotating speed of the motor at m moments Respectively carrying into a driving resistance moment calculation formula: WR (pulse Width modulation)_(t)＝A×MotSpd_(t) ²+B×MotSpd_(t)+ C, calculating the running resistance at m times and converting the running resistance into the running resistance torque at the motor end

Respectively and correspondingly substituting the actual torque of the motor at m moments, the rotating speed of the motor model at m moments, the pressure of the brake master cylinder at m moments into the braking torque at the motor end and the driving resistance at m moments into the driving resistance torque at the motor end into formulas: MotSpdMod_(t+dt)＝MotSpdMod_(t)+(M_(t)-WR_(t)-WB_(t))×Kf₁X dt, m Kf are calculated₁；

For m Kf₁Averaging, m Kf₁Is used as the preset powertrain characteristic correction coefficient Kf.

6. The method of claim 5, wherein the table of speed-torque-torsional compensation coefficients is obtained by testing:

firstly, presetting a torsional vibration compensation coefficient as an empirical value or zero;

secondly, enabling the vehicle to run at the actual rotating speed and the actual torque of a certain motor; if the vehicle meets the driving smoothness evaluation standard, recording the actual rotating speed of the motor, the actual torque of the motor and the anti-torsional vibration compensation coefficient at the moment, if the vehicle does not meet the driving smoothness evaluation standard, changing the anti-torsional vibration compensation coefficient, enabling the vehicle to continuously run at the actual rotating speed of the motor and the actual torque of the motor until the vehicle meets the driving smoothness evaluation standard, and recording the actual rotating speed of the motor, the actual torque of the motor and the anti-torsional vibration compensation coefficient when the vehicle meets the driving smoothness evaluation standard;

thirdly, changing the actual rotating speed and/or the actual torque of the motor, enabling the vehicle to run at the changed actual rotating speed and/or the changed actual torque of the motor, recording the actual rotating speed, the actual torque and the torsional vibration resistance compensation coefficient of the motor at the moment if the vehicle meets the driving smoothness evaluation standard, changing the torsional vibration resistance compensation coefficient if the vehicle does not meet the driving smoothness evaluation standard, enabling the vehicle to continue running at the actual rotating speed and the actual torque of the motor until the vehicle meets the driving smoothness evaluation standard, and recording the actual rotating speed, the actual torque and the torsional vibration resistance compensation coefficient of the motor when the vehicle meets the driving smoothness evaluation standard;

and fourthly, combining all the actual rotating speeds of the motor, the actual torque of the motor and the torsional vibration resistance compensation coefficient which meet the driving smoothness evaluation standard to form the rotating speed-torque-torsional vibration resistance compensation coefficient table.

Technical Field

The invention belongs to the field of electric vehicle control, and particularly relates to a torsional vibration control method based on an electric drive system of an electric vehicle.

Background

The electric driving system of the electric automobile can be simplified into a single-mass spring system when the automobile runs dynamically. When the running condition of the vehicle is changed violently, the rotating speed oscillation impact can be caused, the vehicle shakes forwards and backwards, and torsional vibration is generated. Torsional vibration control is the reduction or attenuation of such oscillations by torque intervention to the point where they are imperceptible to, or within acceptable limits for, the driver.

CN106740272A discloses a pure electric vehicle and a method and a device for controlling low-speed shaking of the pure electric vehicle, wherein whether the pure electric vehicle shakes at a low speed is judged according to the rotating speed of a motor output shaft; when the pure electric vehicle shakes at a low speed, the rotating speed of the output shaft of the motor is controlled to be maintained within a preset range, and therefore the low-speed shaking of the pure electric vehicle is better inhibited; the method specifically comprises the following steps: and determining the output torque change amount corresponding to the absolute value of the difference between the currently acquired rotating speed of the motor output shaft and the upper limit value or the lower limit value of the preset range according to the prestored corresponding relation between the rotating speed change amount of the motor output shaft and the output torque change amount of the motor, and reducing or increasing the output torque of the motor by the output torque change amount so as to effectively adjust the rotating speed of the motor output shaft within the preset range. The method is characterized in that torque correction is carried out when the pure electric vehicle shakes at a low speed, so that the rotating speed of the output shaft of the motor is maintained in a preset range, delay exists in torque correction, the rotating speed of the output shaft of the motor is maintained in the preset range, and a driver still can feel irregularity.

Disclosure of Invention

The invention aims to provide a torsional vibration control method based on an electric driving system of an electric vehicle, so that torsional vibration is effectively controlled, and the driving smoothness of the whole vehicle is improved.

The invention discloses a torsional vibration control method based on an electric vehicle electric driving system, which comprises the following steps:

read motor model rotational speed MotSpdMod of moment t_(t)Actual rotation speed MotSpd of motor_(t)Actual torque M of motor_(t)Pressure P of brake master cylinder_(t)And the slope of the road on which the vehicle is located_(t)；

According to said slope_(t)And the actual rotational speed MotSpd of the motor_(t)Determining the running resistance at t moment and converting the running resistance into the running resistance moment WR at the motor end_(t)；

According to the pressure P of the brake master cylinder_(t)And the actual rotational speed MotSpd of the motor_(t)Determining the brake master cylinder pressure at the time t and converting the pressure into the brake torque WB at the motor end_(t)；

Using the integral formula of the rotation speed: MotSpdMod_(t+dt)＝MotSpdMod_(t)+(M_(t)-WR_(t)-WB_(t)) XKf x dt, calculating the motor model rotating speed MotSpdMod at the moment of t + dt_(t+dt)And storing; kf is a preset power assembly characteristic correction coefficient, the vehicle is static at the initial moment, the initial value of the rotating speed of the motor model is equal to zero, the initial value of the actual rotating speed of the motor is equal to zero, the initial value of the actual torque of the motor is equal to zero, and the sum of the initial value of the driving resistance torque converted to the motor end by the driving resistance and the initial value of the braking torque converted to the motor end by the pressure of the brake master cylinder is equal to zero;

obtaining the actual rotating speed MotSpd of the motor at the moment of t + dt_(t+dt)Actual torque M of motor_(t+dt)Pressure P of brake master cylinder_(t+dt)And the slope of the road on which the vehicle is located_(t+dt)And storing;

according to the actual rotating speed MotSpd of the motor_(t+dt)Actual torque M of motor_(t+dt)Inquiring a rotating speed-torque-torsional vibration resistance compensation coefficient table to obtain a corresponding torsional vibration resistance compensation coefficient k_(t+dt)(ii) a The rotating speed-torque-torsional vibration compensation coefficient table is a pre-stored corresponding relation table of the actual rotating speed of the motor, the actual torque of the motor and the torsional vibration compensation coefficient;

using the formula for torsional vibration compensation torque: TC (tungsten carbide)_(t+dt)＝k_(t+dt)×(MotSpdMod_(t+dt)-MotSpd_(t+dt)) And calculating to obtain the torsional vibration compensation torque TC at the moment of t + dt_(t+dt)；

Compensating torque TC for torsional vibration at the moment of t + dt_(t+dt)And superposing the target torque with the original target torque of the motor to obtain the corrected target torque of the motor at the moment of t + dt.

Preferably, according to said slope_(t)And the actual rotational speed MotSpd of the motor_(t)Determining the driving resistance at time t and converting into the driving resistance moment WR at the motor end_(t)The specific mode is as follows:

according to said slope_(t)Inquiring a gradient-fitting parameter table to obtain a specific numerical value of the corresponding fitting parameter A, B, C; wherein, the gradient-fitting parameter table is a pre-stored corresponding relation table of the gradient of the road where the vehicle is located and the fitting parameter A, B, C;

the corresponding specific value of the fitting parameter A, B, C and the actual rotating speed MotSpd of the motor_(t)And carrying in a running resistance moment calculation formula: WR (pulse Width modulation)_(t)＝A×MotSpd_(t) ²+B×MotSpd_(t)+ C, calculating the running resistance at t moment and converting the running resistance into the running resistance moment WR at the motor end_(t)。

Preferably, the master cylinder pressure P is based on_(t)And the actual rotational speed MotSpd of the motor_(t)Determining the brake master cylinder pressure at the time t and converting the pressure into the brake torque WB at the motor end_(t)The specific mode is as follows:

if the actual rotating speed of the motor MoySpd_(t)Is less than or equal to the preset rotation speed threshold Mthre, the vehicle is stationary, and WB is enabled_(t)＝-WR_(t)；

If the actual speed MotSpd of the motor_(t)If the absolute value of (b) is greater than the preset rotation speed threshold value Mthre, it indicates that the vehicle is moving, and WB is made_(t)＝sign×K_b×P_(t)；

Wherein, when MotSpd_(t)When > 0, sign is 1, when MotSpd_(t)When < 0, sign is-1, K_bThe method is a preset conversion coefficient for converting the pressure of the brake master cylinder to the braking torque of the motor end.

Preferably, the slope-fitting parameter table is obtained by the following test:

firstly, enabling the vehicle to run at a constant speed at different speeds on the same slope, and recording the actual motor torque M at t moment corresponding to different speeds on the slope after the actual motor torque and the actual motor rotating speed are stable_(t)And the actual rotating speed MotSpd of the motor_(t)(ii) a Wherein, under the condition of constant-speed running of the vehicle, the running resistance at the time t is converted into the running resistance moment WR of the motor end_(t)Actual torque M of motor equal to t moment_(t)；

Secondly, the actual rotating speed MotSpd of the motor at the t moment corresponding to different vehicle speeds under the slope_(t)Converted to a driving resistance torque WR at the motor end from the driving resistance_(t)And fitting a quadratic function to obtain a running resisting moment calculation formula: WR (pulse Width modulation)_(t)＝A×MoySpd_(t) ²+B×MotSpd_(t)+ C; then extracting fitting parameters A, B, C to obtain a group of fitting parameters A, B, C;

step three, changing the gradient for n-1 times, and then repeatedly executing the step one and the step two until n groups of fitting parameters A, B, C are obtained;

and fourthly, corresponding n groups of fitting parameters A, B, C to n gradients one by one to form the gradient-fitting parameter table.

Preferably, the preset powertrain characteristic correction coefficient Kf is obtained by the following test:

the vehicle is enabled to run on a flat road at uniform acceleration, and the actual torque of the motor at m moments in the process of running at uniform acceleration is recordedActual rotating speed of motor at m moments Wherein, under the condition of uniform acceleration running of the vehicle, the motor model rotating speed at m moments Respectively equal to the actual rotational speed of the motor at the corresponding moment The pressure of the brake master cylinder at m moments is converted into the braking torque of the motor endAre all equal to zero;

fitting parameters A, B, C corresponding to the flat road and the actual rotating speed of the motor at m moments Respectively carrying into a driving resistance moment calculation formula: WR (pulse Width modulation)_(t)＝A×MotSpd_(t) ²+B×MotSpd_(t)+ C, calculating the running resistance at m times and converting the running resistance into the running resistance torque at the motor end

Respectively and correspondingly substituting the actual torque of the motor at m moments, the rotating speed of the motor model at m moments, the pressure of the brake master cylinder at m moments into the braking torque at the motor end and the driving resistance at m moments into the driving resistance torque at the motor end into formulas: MotSpdMod_(t+dt)＝MotSpdMod_(t)+(M_(t)-WR_(t)-WB_(t))×Kf₁X dt, m Kf are calculated₁；

For m Kf₁Averaging, m Kf₁Is used as the preset power assembly characteristic correction coefficientKf。

Preferably, the table of the rotational speed-torque-torsional vibration compensation coefficients is obtained by the following test:

firstly, presetting a torsional vibration compensation coefficient as an empirical value or zero;

secondly, enabling the vehicle to run at the actual rotating speed and the actual torque of a certain motor; if the vehicle meets the driving smoothness evaluation standard (for example, no torsional vibration occurs or the torsional vibration is within an acceptable range), recording the actual rotating speed of the motor, the actual torque of the motor and the torsional vibration resistance compensation coefficient at the moment, if the vehicle does not meet the driving smoothness evaluation standard, changing the torsional vibration resistance compensation coefficient, enabling the vehicle to continuously run at the actual rotating speed of the motor and the actual torque of the motor until the vehicle meets the driving smoothness evaluation standard, and recording the actual rotating speed of the motor, the actual torque of the motor and the torsional vibration resistance compensation coefficient when the vehicle meets the driving smoothness evaluation standard;

thirdly, changing the actual rotating speed and/or the actual torque of the motor, enabling the vehicle to run at the changed actual rotating speed and/or the changed actual torque of the motor, recording the actual rotating speed, the actual torque and the torsional vibration resistance compensation coefficient of the motor at the moment if the vehicle meets the driving smoothness evaluation standard, changing the torsional vibration resistance compensation coefficient if the vehicle does not meet the driving smoothness evaluation standard, enabling the vehicle to continue running at the actual rotating speed and the actual torque of the motor until the vehicle meets the driving smoothness evaluation standard, and recording the actual rotating speed, the actual torque and the torsional vibration resistance compensation coefficient of the motor when the vehicle meets the driving smoothness evaluation standard;

and fourthly, combining all the actual rotating speeds of the motor, the actual torque of the motor and the torsional vibration resistance compensation coefficient which meet the driving smoothness evaluation standard to form the rotating speed-torque-torsional vibration resistance compensation coefficient table.

According to the invention, the torsional vibration compensation torque is obtained by multiplying the difference value between the model rotating speed and the actual rotating speed of the motor by the torsional vibration compensation coefficient, and the target torque of the motor is corrected. The motor model rotating speed is the theoretical rotating speed of the motor without torsional vibration influence, the actual rotating speed of the motor is compared with the rotating speed of the motor model, and then the actual rotating speed of the motor is used as a correction basis to be close to the rotating speed of the motor model as far as possible, the correction basis is accurate, and the torque correction is timely, so that the torsional vibration is more effectively controlled, and the driving smoothness of the whole vehicle is improved.

Drawings

Fig. 1 is a schematic diagram of torsional vibration control based on an electric drive system of an electric vehicle according to the present embodiment.

Fig. 2 is a flowchart of a torsional vibration control method based on an electric drive system of an electric vehicle according to the present embodiment.

Detailed Description

As shown in fig. 1 and fig. 2, the torsional vibration control method based on the electric drive system of the electric vehicle in the present embodiment includes:

step one, reading the stored motor model rotating speed MotSpdMod at the moment t_(t)Actual rotation speed MotSpd of motor_(t)Actual torque M of motor_(t)Pressure P of brake master cylinder_(t)And the slope of the road on which the vehicle is located_(t)。

Step two, slope according to t moment_(t)And the actual motor speed MotSpd at time t_(t)Determining the running resistance at t moment and converting the running resistance into the running resistance moment WR at the motor end_(t)。

First, the slope according to time t_(t)And inquiring the gradient-fitting parameter table to obtain the specific numerical value of the corresponding fitting parameter A, B, C. Wherein, the gradient-fitting parameter table is a pre-stored corresponding relation table of the gradient of the road where the vehicle is located and the fitting parameter A, B, C;

then, the corresponding specific value of the fitting parameter A, B, C and the actual motor rotation speed MotSpd at the time t are compared_(t)And carrying in a running resistance moment calculation formula: WR (pulse Width modulation)_(t)＝A×MotSpd_(t) ²+B×MotSpd_(t)+ C, calculating the running resistance at t moment and converting the running resistance into the running resistance moment WR at the motor end_(t)。

As an example, the slope-fitting parameter table described above can be obtained by the following tests:

firstly, enabling the vehicle to run at a constant speed at different speeds under the same gradient, and waiting for the actual torque of the motorAfter the actual rotating speed of the motor is stable, recording the actual torque M of the motor at the t moment corresponding to different vehicle speeds under the slope_(t)And the actual rotating speed MotSpd of the motor_(t). Wherein, under the condition of constant-speed running of the vehicle, the running resistance at the time t is converted into the running resistance moment WR of the motor end_(t)Actual torque M of motor equal to t moment_(t)。

Secondly, the actual rotating speed MotSpd of the motor at the t moment corresponding to different vehicle speeds under the slope_(t)Converted to a driving resistance torque WR at the motor end from the driving resistance_(t)And fitting a quadratic function to obtain a running resisting moment calculation formula: WR (pulse Width modulation)_(t)＝A×MotSpd_(t) ²+B×MotSpd_(t)+ C; the fitting parameters A, B, C are then extracted to obtain a set of fitting parameters A, B, C. The vehicle running resistance includes rolling resistance, air resistance, and gradient resistance. The difference in driving force and running resistance causes the vehicle to accelerate. On the premise that the calculation period dt is small enough, the output torque of the motor is approximately considered to be unchanged, and the theoretical rotating speed (namely the rotating speed of the motor model) of the next sampling period of the motor can be estimated if the running resistance is known. The air resistance of the vehicle is proportional to the square of the vehicle speed, and the running resistance is converted into the resistance moment of the motor end by fitting a quadratic function of the actual rotating speed of the motor.

And thirdly, changing the gradient n-1 times, and then repeatedly executing the first step and the second step until n groups of fitting parameters A, B, C are obtained.

And fourthly, corresponding n groups of fitting parameters A, B, C to n gradients one by one to form the gradient-fitting parameter table.

Step three, according to the pressure P of the brake master cylinder at the time t_(t)And the actual motor speed MotSpd at time t_(t)Determining the brake master cylinder pressure at the time t and converting the pressure into the brake torque WB at the motor end_(t)。

Judging whether the actual rotating speed MotSpd of the motor exists or not_(t)The absolute value of (a) is less than or equal to a preset rotation speed threshold value Mthre;

if yes, the vehicle is shown to be stationary, and WB is driven_(t)＝-WR_(t)。

Otherwise (i.e. actual speed of the motor)MotSpd_(t)Is greater than a preset rotational speed threshold value Mthre), indicating that the vehicle is moving, and making WB_(t)＝sign×K_b×P_(t)。

Wherein Mthre is more than or equal to 0; when MotSpd_(t)When > 0, sign is 1, when MotSpd_(t)When < 0, sign is-1, K_bFor a predetermined conversion factor, K, for converting the pressure of the brake master cylinder to the braking torque at the motor end_bRelated to braking system, tire radius, speed ratio of the retarder, etc.

Step four, utilizing a rotating speed integral formula: MotSpdMod_(t+dt)＝MotSpdMod_(t)+(M_(t)-WR_(t)-WB_(t)) XKf x dt, calculating the motor model rotating speed MotSpdMod at the moment of t + dt_(t+dt)And stored. Kf is a preset power assembly characteristic correction coefficient; the vehicle is static at the initial moment, and the initial value of the rotating speed of the motor model (namely the rotating speed MotSpdMod of the motor model at the initial moment)₍₀₎) Equal to zero, the initial value of the actual rotation speed of the motor (i.e. the actual rotation speed MotSpd of the motor at the initial moment)₍₀₎) Equal to zero, the initial value of the actual torque of the motor (i.e. the actual torque M of the motor at the initial moment)₍₀₎) Is equal to zero; initial value of master cylinder pressure (i.e. master cylinder pressure P at initial time)₍₀₎) Satisfies the following conditions: the running resistance is converted to an initial value of the running resistance torque of the motor end (i.e., the running resistance at the initial time is converted to the running resistance torque WR of the motor end₍₀₎) The initial value of the braking torque converted to the motor end from the pressure of the brake master cylinder (namely the braking torque WB converted to the motor end from the pressure of the brake master cylinder at the initial moment)₍₀₎) The sum is equal to zero; i.e. WR if the vehicle is stationary on a flat road with a gradient of 0 at the initial moment₍₀₎＝0，WB₍₀₎0; WR if the vehicle is stationary on a grade other than 0 at the initial time₍₀₎≠0，WB₍₀₎＝-WR₍₀₎The braking torque maintains the vehicle on the grade.

The vehicle dynamics model simplified equation is:wherein M is_(t)At time tActual torque (i.e. motor-side output torque), WR, of the motor_(t)Converting the driving resistance at time t into the driving resistance torque at the motor end, WB_(t)The pressure of the brake master cylinder at the time t is converted into the brake torque at the end of the motor, J is the rotational inertia of the whole driving and transmission chain,is the angular acceleration of the motor model.

According to the following steps:(i.e. theIs proportional to) Andand (4) obtaining a rotation speed integral formula by sorting: MotSpdMod_(t+dt)＝MotSpdMod_(t)+(M_(t)-WR_(t)-WB_(t))×Kf×dt。

Wherein the content of the first and second substances,representing the motor model rotational acceleration, MotSpdMod_(t+dt)Motor model speed, MotSpdMod, representing time t + dt_(t)Expressing the rotating speed of the motor model at the moment t, Kf is a preset power assembly characteristic correction coefficient,(i.e., Kf is proportional to). Kf depends on the characteristics of the power assembly, such as the gear of a speed reducer, the vehicle servicing mass and the rotational inertia of a shafting of a motor system.

By way of example, Kf may be obtained by the following test:

firstly, making the vehicle carry out uniform acceleration running on a flat road (the gradient is 0), and recording the actual torque of the motor at m moments in the uniform acceleration running processActual rotating speed of motor at m momentsWherein, under the condition of uniform acceleration running of the vehicle, the motor model rotating speed at m moments Respectively equal to the actual rotational speed of the motor at the corresponding moment The pressure of the brake master cylinder at m moments is converted into the braking torque of the motor endAre all equal to zero (since the brake pedal is not stepped on when the vehicle is in uniform acceleration running on a flat road, the brake master cylinder pressure at each moment is equal to zero, and therefore the brake master cylinder pressure at each moment is converted into the brake torque at the motor end and is also equal to zero).

Secondly, fitting parameters A, B, C corresponding to the flat road and the actual rotating speed of the motor at m moments Respectively carrying into a driving resistance moment calculation formula: WR (pulse Width modulation)_(t)＝A×MotSpd_(t) ²+B×MotSpd_(t)+ C, calculating the running resistance at m timesForce conversion to motor-end driving moment

Thirdly, the actual torque of the motor at m momentsmotor model rotation speed at m moments The pressure of the brake master cylinder at m times is converted into the braking torque (all equal to zero) of the motor end, and the running resistance at m times is converted into the running resistance torque of the motor end Respectively correspondingly substituting into the formulas: MotSpdMod_(t+dt)＝MotSpdMod_(t)+(M_(t)-WR_(t)-WB_(t))×Kf₁X dt, m Kf are calculated₁。

For m Kf₁Averaging, m Kf₁The average value of (d) is used as a preset powertrain characteristic correction coefficient Kf.

Step five, acquiring the actual rotating speed MotSpd of the motor at the moment of t + dt_(t+dt)Actual torque M of the motor at time t + dt_(t+dt)Brake master cylinder pressure P at time t + dt_(t+dt)And the slope of the road on which the vehicle is located at time t + dt_(t+dt)And stored.

Step six, according to the actual rotating speed MotSpd of the motor at the moment of t + dt_(t+dt)Actual torque M of motor_(t+dt)Inquiring a rotating speed-torque-torsional vibration resistance compensation coefficient table to obtain a corresponding torsional vibration resistance compensation coefficient k_(t+dt). Wherein, the rotating speed-torque-anti-torsional vibration compensation coefficient table is a prestored motor actual rotation tableAnd the corresponding relation table of the speed, the actual torque of the motor and the torsional vibration compensation coefficient.

As an example, the table of the rotational speed-torque-torsional vibration compensation coefficients can be obtained by the following tests:

in the first step, the torsional vibration compensation coefficient is preset to an empirical value or zero.

Secondly, enabling the vehicle to run at the actual rotating speed and the actual torque of a certain motor; if the vehicle meets the driving smoothness evaluation standard (for example, no torsional vibration occurs or the torsional vibration is within an acceptable range), recording the actual rotating speed of the motor, the actual torque of the motor and the torsional vibration compensation coefficient at the moment, if the vehicle does not meet the driving smoothness evaluation standard, changing the torsional vibration compensation coefficient, enabling the vehicle to continuously run at the actual rotating speed of the motor and the actual torque of the motor until the vehicle meets the driving smoothness evaluation standard, and recording the actual rotating speed of the motor, the actual torque of the motor and the torsional vibration compensation coefficient when the vehicle meets the driving smoothness evaluation standard.

And thirdly, changing the actual rotating speed and/or the actual torque of the motor, enabling the vehicle to run at the changed actual rotating speed and/or the changed actual torque of the motor, recording the actual rotating speed, the actual torque and the torsional vibration resistance compensation coefficient of the motor at the moment if the vehicle meets the driving smoothness evaluation standard, changing the torsional vibration resistance compensation coefficient if the vehicle does not meet the driving smoothness evaluation standard, enabling the vehicle to continue running at the actual rotating speed and the actual torque of the motor until the vehicle meets the driving smoothness evaluation standard, and recording the actual rotating speed, the actual torque and the torsional vibration resistance compensation coefficient of the motor when the vehicle meets the driving smoothness evaluation standard.

And fourthly, combining all the actual rotating speeds of the motor, the actual torque of the motor and the torsional vibration resistance compensation coefficient which meet the driving smoothness evaluation standard to form a rotating speed-torque-torsional vibration resistance compensation coefficient table.

Step seven, utilizing a torsional vibration compensation torque formula: TC (tungsten carbide)_(t+dt)＝k_(t+dt)×(MotSpdMod_(t+dt)-MoySpd_(t+dt)) And calculating to obtain the torsional vibration compensation torque TC at the moment of t + dt_(t+dt)。

Step eight, compensating the torsional vibration resistance torque TC at the time of t + dt_(t+dt)And superposing the target torque with the original target torque of the motor to obtain the corrected target torque of the motor at the moment of t + dt.

And outputting the corrected motor target torque to a downstream control module for torque control, so that the driving smoothness of the whole vehicle is improved.