A four-wheel hub motor straight-line driving control method considering motor dynamic response differences

Abstract

The present invention discloses a method for controlling straight-line driving of four in-wheel hub motors that takes into account differences in the dynamic response of the motors. This method relates to the field of new energy vehicle technology and includes the following steps: obtaining the total required torque of the vehicle based on the vehicle speed and pedal opening of the four in-wheel hub motors; establishing an objective function and constraints based on the total required torque of the vehicle to optimize torque distribution; and, based on the optimization results, performing coordinated straight-line driving control of the four in-wheel hub motors to achieve straight-line driving control of the four in-wheel hub motors that takes into account differences in the dynamic response of the motors. This method solves the problem that existing technologies fail to account for the differences in the dynamic responses of the four motors, making it difficult to ensure the stability of the vehicle's straight-line driving.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and in particular to a four-wheel hub motor straight-line driving control method taking into account motor dynamic response differences. Background Art

[0002] Four-wheel hub motor drive technology has long attracted attention due to its improved controllability and energy efficiency compared to traditional central drive and traditional four-wheel drive. In a four-wheel hub motor drive system, the motor on each wheel hub can be individually controlled. However, due to factors such as manufacturing, operating conditions, and usage, the dynamic response of the four hub motors often varies. This means that each hub motor exhibits different characteristics and dynamic response speeds when responding to input commands and torque requirements. This variability can negatively impact the vehicle's handling performance. For example, in straight-line driving, inconsistent responses between the left and right hub motors can cause drag, causing the vehicle to veer off course and fail to meet national standards. In cornering and other operating conditions, inconsistent responses can lead to vehicle instability. Therefore, reducing the variability in motor dynamic response and achieving coordinated control of the four-wheel hub motors has important research significance and engineering application value.

[0003] However, the traditional coordinated control of four-wheel hub motors for straight-line driving does not take into account the dynamic response differences of the four motors, making it difficult to ensure the stability of the vehicle's straight-line driving. Summary of the Invention

[0004] In response to the above-mentioned deficiencies in the prior art, the present invention provides a four-wheel hub motor straight-line driving control method that takes into account the dynamic response differences of the motors, which solves the problem that the prior art does not take into account the dynamic response differences of the four motors and is difficult to ensure the stability of the vehicle's straight-line driving.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is: a four-wheel hub motor straight-line driving control method considering the dynamic response differences of the motors, comprising the following steps:

[0006] S1: Obtain the total required torque of the vehicle based on the vehicle speed and pedal opening of the four-wheel hub motor;

[0007] S2: Based on the total required torque of the vehicle, establish the objective function and constraints to optimize the torque distribution;

[0008] S3: Based on the optimization results, the straight-line driving coordination control of the four-wheel hub motors is carried out to complete the straight-line driving control of the four-wheel hub motors taking into account the dynamic response differences of the motors.

[0009] The beneficial effect of the above scheme is: the present invention proposes a coordinated control method for straight-line driving of four-wheel hub motors taking into account the differences in dynamic response of the motors. By taking into account the differences in dynamic response of the motors, the torque distribution is optimized, and the motors are coordinated and controlled for straight-line driving, which solves the problem that the existing technology does not take into account the dynamic response differences of the four motors and is difficult to ensure the stability of the vehicle's straight-line driving.

[0010] Furthermore, S1 includes the following sub-steps:

[0011] S1-1: The vehicle speed is driven by the four-wheel hub motors Calculate vehicle speed , the formula is:

[0012]

[0013] in, is the wheel radius;

[0014] S1-2: According to vehicle speed Interpolation calculation of the maximum torque of the left front wheel motor , Maximum torque of the right front wheel motor , Maximum torque of the left rear wheel motor and the maximum torque of the right rear wheel motor , the formula is:

[0015]

[0016]

[0017]

[0018]

[0019] in, is the motor external characteristic of the left front wheel motor, is the external characteristic of the right front wheel motor, is the motor external characteristic of the left rear wheel motor, is the motor external characteristic of the right rear wheel motor;

[0020] S1-3: Add the maximum torque of the motor to obtain the maximum driving torque of the vehicle , the formula is:

[0021] .

[0022] S1-4: According to the pedal opening and the vehicle's maximum driving torque Calculate the total required torque , the formula is:

[0023]

[0024]

[0025] in, is the first parameter.

[0026] The beneficial effect of the above further solution is: through the above technical solution, the total required torque is calculated based on the motor speed, the maximum torque of the four motors, and the pedal opening.

[0027] Furthermore, the objective function in S2 for:

[0028]

[0029] in, Indicates taking the minimum value, is the left front wheel motor torque, is the right front wheel motor torque, is the left rear wheel motor torque, is the right rear wheel motor torque, is the efficiency of the left front wheel motor, is the right front wheel motor efficiency, is the efficiency of the left rear wheel motor, is the right rear wheel motor efficiency.

[0030] The beneficial effect of the above further solution is that, through the above technical solution, the objective function is determined according to the motor torque, motor efficiency and vehicle speed.

[0031] Furthermore, the constraints in S2 include:

[0032] Total demand torque constraint:

[0033]

[0034] Straight-line driving allocation constraints:

[0035]

[0036] Motor drive limit constraints:

[0037]

[0038] Battery output power constraints:

[0039]

[0040] in, is the battery open circuit voltage, is the current;

[0041] Ground attachment constraint:

[0042]

[0043] in, is the road adhesion coefficient, is the vertical load of the left front wheel motor, is the vertical load of the right front wheel motor, is the vertical load of the left rear wheel motor, is the vertical load of the right rear wheel motor;

[0044] Motor efficiency constraints:

[0045]

[0046] in, is the efficiency map characteristic of the left front wheel motor, is the efficiency map characteristic of the right front wheel motor, is the efficiency map characteristic of the left rear wheel motor, This is the efficiency map characteristic of the right rear wheel motor.

[0047] The beneficial effect of the above further solution is: through the above technical solution, the total required torque constraint, straight-line driving distribution constraint, motor drive polar constraint, battery output power constraint, ground adhesion constraint and motor efficiency constraint are established.

[0048] Furthermore, in S3, the four-wheel hub motors are coordinated to control the straight-line driving, including the following sub-steps:

[0049] S3-1: Control the yaw motion of the motor to obtain the motor torque distribution result;

[0050] S3-2: Perform dynamic compensation control on the motor according to the motor torque distribution result;

[0051] S3-3: Based on dynamic compensation control, single motor compensation control is performed on the motor to complete the coordinated control of the motor's straight-line driving.

[0052] The beneficial effect of the above further solution is that the motor's straight-line driving coordinated control is achieved by performing yaw motion control, dynamic compensation control and single-motor compensation control on the motor.

[0053] Furthermore, the dynamic compensation control formula in S3-2 is:

[0054]

[0055] in, is the dynamic response time constant of the left front wheel motor, is the dynamic response time constant of the right front wheel motor, is the dynamic response time constant of the left rear wheel motor, is the dynamic response time constant of the right rear wheel motor, It is the left front wheel dynamic compensation switch. It is the right front wheel dynamic compensation switch. It is the left rear wheel dynamic compensation switch. It is the right rear wheel dynamic compensation switch.

[0056] The beneficial effect of the above further solution is that a dynamic compensation control strategy is provided to ensure that the vehicle travels as straight as possible and that the torque response speeds of the left and right motors are as consistent as possible.

[0057] Furthermore, in the S3-3 single motor compensation control, feedforward compensation is performed on the steady-state deviation. The steady-state deviation is determined by table lookup based on the motor speed and target torque combined with experimental data; the dynamic deviation is dynamically compensated using the PID method.

[0058] The beneficial effect of the above further solution is that: there are steady-state deviations and dynamic deviations in the motor response, and the steady-state deviations and dynamic deviations are compensated respectively, so that the response speeds of the left and right motors are consistent.

[0059] Furthermore, the steady-state deviation formula is:

[0060]

[0061] in, is the steady-state deviation of the left front wheel motor, is the steady-state deviation of the right front wheel motor, is the steady-state deviation of the left rear wheel motor, is the steady-state deviation of the right rear wheel motor, is the motor steady-state deviation interpolation function.

[0062] The beneficial effect of the above further solution is that: through the above technical solution, a steady-state deviation is obtained to achieve feedforward compensation.

[0063] Furthermore, in the dynamic deviation, the PID formula is written as a transfer function formula:

[0064]

[0065] in, is the target torque of the left front wheel after considering dynamic compensation, is the left front motor torque response error, is the complex variable in the Laplace transform, 、 and They are the three control parameters of PID.

[0066] The beneficial effect of the above further solution is: through the above technical solution, the PID algorithm is used to realize dynamic compensation of dynamic deviation, so that the left front wheel and the right front wheel respond synchronously, and the left rear wheel and the right rear wheel respond synchronously. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 Flowchart of the straight-line driving control method for four-wheel hub motors taking into account the dynamic response differences of the motors.

[0068] Figure 2 A schematic diagram of driving modes.

[0069] Figure 3 This is the coordinated control block diagram for straight-line driving.

[0070] Figure 4 This is the single motor compensation control block diagram.

[0071] Figure 5 A schematic diagram illustrating dynamic compensation.

[0072] Figure 6 This is a comparison chart of simulation results without and with coordinated control of four-wheel hub motors for straight-line driving. DETAILED DESCRIPTION

[0073] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0074] like Figure 1 As shown, a four-wheel hub motor straight-line driving control method considering the dynamic response difference of the motor includes the following steps:

[0075] S1: Obtain the total required torque of the vehicle based on the vehicle speed and pedal opening of the four-wheel hub motor;

[0076] S2: Based on the total required torque of the vehicle, establish the objective function and constraints to optimize the torque distribution;

[0077] S3: Based on the optimization results, the straight-line driving coordination control of the four-wheel hub motors is carried out to complete the straight-line driving control of the four-wheel hub motors taking into account the dynamic response differences of the motors.

[0078] S1 includes the following steps:

[0079] S1-1: The vehicle speed is driven by the four-wheel hub motors Calculate vehicle speed , the formula is:

[0080]

[0081] in, is the wheel radius;

[0082] S1-2: According to vehicle speed Interpolation calculation of the maximum torque of the left front wheel motor , Maximum torque of the right front wheel motor , Maximum torque of the left rear wheel motor and the maximum torque of the right rear wheel motor , the formula is:

[0083]

[0084]

[0085]

[0086]

[0087] in, is the motor external characteristic of the left front wheel motor, is the external characteristic of the right front wheel motor, is the motor external characteristic of the left rear wheel motor, is the motor external characteristic of the right rear wheel motor;

[0088] S1-3: Add the maximum torque of the motor to obtain the maximum driving torque of the vehicle , the formula is:

[0089] .

[0090] S1-4: According to the pedal opening and the vehicle's maximum driving torque Calculate the total required torque , the formula is:

[0091]

[0092]

[0093] in, is the first parameter.

[0094] like Figure 2 As shown, it is a schematic diagram of the driving mode in this embodiment.

[0095] Objective function in S2 for:

[0096]

[0097] in, Indicates taking the minimum value, is the left front wheel motor torque, is the right front wheel motor torque, is the left rear wheel motor torque, is the right rear wheel motor torque, is the efficiency of the left front wheel motor, is the right front wheel motor efficiency, is the efficiency of the left rear wheel motor, is the right rear wheel motor efficiency.

[0098] The constraints in S2 include:

[0099] Total demand torque constraint:

[0100]

[0101] Straight-line driving allocation constraints:

[0102]

[0103] Motor drive limit constraints:

[0104]

[0105] Battery output power constraints:

[0106]

[0107] in, is the battery open circuit voltage, is the current;

[0108] Ground attachment constraint:

[0109]

[0110] in, is the road adhesion coefficient, is the vertical load of the left front wheel motor, is the vertical load of the right front wheel motor, is the vertical load of the left rear wheel motor, is the vertical load of the right rear wheel motor;

[0111] Motor efficiency constraints:

[0112]

[0113] in, is the efficiency map characteristic of the left front wheel motor, is the efficiency map characteristic of the right front wheel motor, is the efficiency map characteristic of the left rear wheel motor, This is the efficiency map characteristic of the right rear wheel motor.

[0114] In S3, the four-wheel hub motors are coordinated to control the straight-line driving, such as Figure 3 As shown, it includes the following steps:

[0115] S3-1: Control the yaw motion of the motor to obtain the motor torque distribution result;

[0116] S3-2: Perform dynamic compensation control on the motor according to the motor torque distribution result;

[0117] S3-3: Based on dynamic compensation control, single motor compensation control is performed on the motor to complete the coordinated control of the motor's straight-line driving.

[0118] The dynamic compensation control formula in S3-2 is:

[0119]

[0120] in, is the dynamic response time constant of the left front wheel motor, is the dynamic response time constant of the right front wheel motor, is the dynamic response time constant of the left rear wheel motor, is the dynamic response time constant of the right rear wheel motor, It is the left front wheel dynamic compensation switch. , it means that the left front wheel does not need to be dynamically supplemented. , it means that the left front wheel needs to be dynamically supplemented. It is the right front wheel dynamic compensation switch. It is the left rear wheel dynamic compensation switch. It is the right rear wheel dynamic compensation switch.

[0121] In one embodiment of the present invention, it is assumed that the four motor dynamic response transfer functions obtained by measurement are: , , , , These are the steady-state response gains of the left front wheel, right front wheel, left rear wheel, and right rear wheel motors, respectively. To ensure that the vehicle travels as straight as possible and the torque response speeds of the left and right motors are as consistent as possible, the dynamic compensation control decision principle is shown above.

[0122] In the S3-3 single motor compensation control, feedforward compensation is performed on the steady-state deviation. The steady-state deviation is determined by looking up the table based on the motor speed and target torque in combination with experimental data. Since the torque response of the motor has a torque response deviation under different motor speeds and target torques, the steady-state deviation value can be obtained based on multiple test measurements. The table can be measured in advance and written into the controller to obtain the value by looking up the table based on the motor speed and target torque; the dynamic deviation is dynamically compensated using the PID method, such as Figure 4 shown.

[0123] The steady-state deviation formula is:

[0124]

[0125] in, is the steady-state deviation of the left front wheel motor, is the steady-state deviation of the right front wheel motor, is the steady-state deviation of the left rear wheel motor, is the steady-state deviation of the right rear wheel motor, is the motor steady-state deviation interpolation function.

[0126] In dynamic deviation, the PID formula is written as a transfer function formula:

[0127]

[0128] in, is the target torque of the left front wheel after considering dynamic compensation, is the left front motor torque response error, is the complex variable in the Laplace transform, 、 and They are the three control parameters of PID.

[0129] In one embodiment of the present invention, the motor response has steady-state deviation and dynamic deviation. The steady-state error only needs to be compensated for by feedforward. The steady-state deviation can be determined by looking up the table according to the motor speed and target torque, and is expressed as:

[0130]

[0131] like Figure 5 As shown, taking the left front wheel as an example, when If switch 1 and switch 2 are placed at the top, no dynamic compensation is performed; , then switch 1 and switch 2 are placed at the bottom for dynamic compensation.

[0132] Dynamic compensation mainly uses the PID principle for compensation. PID formula as follows:

[0133]

[0134] in, , All ≥0.

[0135] Written in transfer function form as follows:

[0136]

[0137] The closed-loop transfer function of the left front motor dynamic compensation control is as follows:

[0138]

[0139] The purpose of dynamic compensation is to make the response speed of the left and right motors consistent. , it means the right front wheel responds quickly, The right front wheel does not need dynamic compensation, by setting The transfer function of the entire closed-loop transfer function is consistent with the open-loop characteristics of the right front wheel, that is:

[0140]

[0141] This ensures that the responses of the left and right front wheels are synchronized. Similarly, the dynamic compensation principles of the left and right rear wheels are similar.

[0142] In one embodiment of the present invention, the basic parameters of a four-wheel hub motor driven vehicle are as follows: , , , , , , , , , , , , , , , , , it can be seen that , then the left front motor needs dynamic compensation. After debugging, the dynamic compensation control PID parameter values ​​are obtained: , , , the right front motor does not need dynamic compensation; similarly, The left rear motor requires dynamic compensation. After debugging, the dynamic compensation control PID parameter values ​​are obtained: , , , the right rear motor does not require dynamic compensation.

[0143] In this embodiment, according to the above steps, the vehicle speed is selected to be 20m / s, and the simulation results are as follows: Figure 6 As shown in the figure, it can be seen that the lateral displacement of the vehicle with coordinated control is only 0.3m, while the lateral displacement of the vehicle without coordinated control can reach 2.5m, which shows the effectiveness of the present invention.

[0144] The present invention proposes a coordinated control method for straight-line driving of four-wheel hub motors that takes into account the differences in the dynamic responses of the motors. By taking into account the differences in the dynamic responses of the motors, steady-state compensation and dynamic compensation control are performed to solve the problem of vehicle deviation caused by inconsistent dynamic responses of the four-wheel hub motors, and improve the consistency of the vehicle's driving performance and straight-line driving stability.

[0145] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the invention.

Claims

1. A four-wheel hub motor straight-line driving control method considering motor dynamic response differences, characterized in that: The following steps are involved: S1: Obtain the total required torque of the vehicle based on the vehicle speed and pedal opening of the four-wheel hub motor; S2: Based on the total required torque of the vehicle, establish the objective function and constraints to optimize the torque distribution; S3: Based on the optimization results, the four-wheel hub motors are coordinated to control the straight-line driving, completing the four-wheel hub motor straight-line driving control that takes into account the differences in the motor dynamic responses. The coordinated control of the four-wheel hub motors for straight-line driving in S3 includes the following steps: S3-1: Control the yaw motion of the motor to obtain the motor torque distribution result; S3-2: Perform dynamic compensation control on the motor according to the motor torque distribution result; The dynamic compensation control formula in S3-2 is: in, is the dynamic response time constant of the left front wheel motor, is the dynamic response time constant of the right front wheel motor, is the dynamic response time constant of the left rear wheel motor, is the dynamic response time constant of the right rear wheel motor, It is the left front wheel dynamic compensation switch. It is the right front wheel dynamic compensation switch. It is the left rear wheel dynamic compensation switch. It is the right rear wheel dynamic compensation switch; S3-3: Based on dynamic compensation control, single motor compensation control is performed on the motor to complete the coordinated control of the motor in straight line driving; In the S3-3 single motor compensation control, feedforward compensation is performed on the steady-state deviation, and the steady-state deviation is determined by looking up the table based on the motor speed and target torque in combination with experimental data; the dynamic deviation is dynamically compensated using the PID method; The steady-state deviation formula is: in, is the steady-state deviation of the left front wheel motor, is the steady-state deviation of the right front wheel motor, is the steady-state deviation of the left rear wheel motor, is the steady-state deviation of the right rear wheel motor, is the motor steady-state deviation interpolation function, is the torque distribution result of the left front wheel motor, is the torque distribution result of the right front wheel motor, The torque distribution result of the left rear wheel motor is: Torque distribution result for the right rear wheel motor; Vehicle speed The formula is: in, is the wheel radius, For vehicle speed.

2. The four-wheel hub motor straight-line driving control method considering motor dynamic response differences according to claim 1 is characterized in that: The S1 includes the following steps: S1-1: The vehicle speed is driven by the four-wheel hub motors Calculate vehicle speed ; S1-2: According to vehicle speed Interpolation calculation of the maximum torque of the left front wheel motor , Maximum torque of the right front wheel motor , Maximum torque of the left rear wheel motor and the maximum torque of the right rear wheel motor , the formula is: in, is the motor external characteristic of the left front wheel motor, is the external characteristic of the right front wheel motor, is the motor external characteristic of the left rear wheel motor, is the motor external characteristic of the right rear wheel motor; S1-3: Add the maximum torque of the motor to obtain the maximum driving torque of the vehicle , the formula is: S1-4: According to the pedal opening and the vehicle's maximum driving torque Calculate the total required torque , the formula is: in, is the first parameter.

3. The four-wheel hub motor straight-line driving control method considering motor dynamic response differences according to claim 2 is characterized in that: The objective function in S2 for: in, Indicates taking the minimum value, is the left front wheel motor torque, is the right front wheel motor torque, is the left rear wheel motor torque, is the right rear wheel motor torque, is the efficiency of the left front wheel motor, is the right front wheel motor efficiency, is the efficiency of the left rear wheel motor, is the right rear wheel motor efficiency.

4. The four-wheel hub motor straight-line driving control method considering motor dynamic response differences according to claim 3 is characterized in that: The constraints in S2 include: Total demand torque constraint: Straight-line driving allocation constraints: Motor drive limit constraints: Battery output power constraints: in, is the battery open circuit voltage, is the current; Ground attachment constraint: in, is the road adhesion coefficient, is the vertical load of the left front wheel motor, is the vertical load of the right front wheel motor, is the vertical load of the left rear wheel motor, is the vertical load of the right rear wheel motor; Motor efficiency constraints: in, is the efficiency map characteristic of the left front wheel motor, is the efficiency map characteristic of the right front wheel motor, is the efficiency map characteristic of the left rear wheel motor, This is the efficiency map characteristic of the right rear wheel motor.

5. The four-wheel hub motor straight-line driving control method considering motor dynamic response differences according to claim 4, wherein in the dynamic deviation, the PID formula is written as a transfer function formula: in, is the target torque of the left front wheel after considering dynamic compensation, is the left front motor torque response error, is the complex variable in the Laplace transform, 、 and They are the three control parameters of PID.

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