Steering system torque calculation method based on double-ring PID algorithm

Abstract

The invention relates to the technical field of steering systems, in particular to a steering system torque calculation method based on a double-ring PID algorithm. A steering system torque calculation method based on a double-ring PID algorithm comprises the double-ring PID algorithm, and the double-ring PID algorithm comprises a front ring part and a rear ring part. In the front ring part, an angle difference is obtained by subtracting a request angle from an actual angle, and an angle control system calculates a target angular velocity according to the angle difference; according to the rear ring part, the difference between the target angular speed and the actual angular speed is obtained, the angular speed difference is subjected to a PID algorithm to obtain target motor torque, the target motor torque is converted into actually-executed motor torque through gradient output, a steering wheel is controlled to rotate, and a steering system torque calculation method comprises a driver takeover optimization strategy and an ADAS takeover optimization strategy. Compared with the prior art, the motor torque is calculated by adopting a double-ring PID algorithm, and the steering wheel is controlled to move to reach a target angle.

Description

Technical Field

[0001] The invention relates to the technical field of steering systems, and in particular to a steering system torque calculation method based on a double-loop PID algorithm. Background Art

[0002] At present, autonomous driving technology has been widely used in the automotive field. The lateral control of autonomous driving is mainly steering. The steering end often designs an angle control system based on the electronic power steering system as a platform, and completes the steering by responding to the angle request of the autonomous driving end. From the perspective of stability, the autonomous driving end does not want the angle control function to be easily interrupted by the outside world and exit. The vehicle end often requires that the angle control function exits when the hand torque value and duration reach the set threshold at the same time, and requires the EPS end not to respond to the driver's input when the hand torque value is small so that the path planning of the vehicle end cannot be easily affected when the hand intervenes. Since the state of the driver when taking over cannot be estimated (there are situations where the steering wheel is taken over by violently hitting the steering wheel or gently pulling the steering wheel), when the hand torque value and duration reach the set threshold at the same time, the basic power torque and angle control torque cannot be "tacitly" coordinated, resulting in the problem of abrupt hand feel. When ADAS takes over the steering wheel, since the performance parameters such as response time are given priority when calibrating the performance parameters, the steering wheel speed will rise rapidly in the early stage of ADAS taking over. When the hand is still lightly touching the steering wheel, the driver will complain that the steering wheel rotation trend is inconsistent with expectations. Summary of the invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a steering system torque calculation method based on a dual-loop PID algorithm, which adopts the dual-loop PID algorithm to calculate the motor torque and control the steering wheel movement to achieve a target angle.

[0004] To achieve the above purpose, a steering system torque calculation method based on a dual-loop PID algorithm is designed, including a dual-loop PID algorithm, wherein the dual-loop PID algorithm includes a front loop part and a rear loop part; the front loop part: the angle difference is obtained by subtracting the requested angle from the actual angle, and the angle control system calculates the target angular velocity according to the angle difference; the rear loop part: the target angular velocity is obtained by subtracting the actual angular velocity from the target angular velocity, and the angular velocity difference is obtained by the PID algorithm to obtain the target motor torque, and the target motor torque is converted into the actual motor torque through the gradient output to control the steering wheel rotation, characterized in that: the steering system torque calculation method includes a driver takeover optimization strategy and an ADAS takeover optimization strategy,

[0005] The driver takeover optimization strategy is as follows:

[0006] S11, setting the vehicle speed range to 0-5 kph to calculate different attenuation coefficients for stationary steering and dynamic steering;

[0007] S12, setting the hand torque threshold, hand torque time threshold and hand torque integral threshold. Each threshold value can be calibrated according to the vehicle speed;

[0008] S13, calculate the P phase attenuation coefficient σ based on the integral value p , I phase Delta term attenuation coefficient σ iΔ , the integral value is the accumulated value of the excess portion over time after the current hand torque exceeds the hand torque threshold;

[0009] S14, according to the locked and stored hand force value TBT when exceeding the hand force torque threshold and the hand force torque time threshold a , calculate the attenuation coefficient σ of the Delay term of I id , the hand force value TBT a The stored hand torque value that exceeds the hand force threshold and the hand torque time threshold at the same time;

[0010] S15, according to the locked and stored hand force value TBT exceeding the hand torque integral threshold b , calculate the hand torque compensation coefficient σ t , the hand force value TBT b is the hand torque when the integral value in step S13 exceeds the integral threshold;

[0011] S16, calculating the angle control torque and the compensation hand torque and outputting them to the motor end;

[0012] The ADAS takeover optimization strategy is as follows:

[0013] S21, detecting the current exit of the driver takeover mode;

[0014] S22, looking up the table to calculate the angular acceleration Δa according to the target speed;

[0015] S23, look up the gain coefficient φ1 according to the vehicle speed;

[0016] S24, calculating the processed target turning angle.

[0017] The target motor torque is calculated as follows:

[0018] Among them, TarMotTorq is the target motor torque, TarAngSpd is the target angular velocity of the steering wheel, CurAngSpd is the actual angular velocity of the steering wheel, Kp is the proportional coefficient, Ki is the integral coefficient, and Kd is the differential coefficient.

[0019] In step S3, the P phase attenuation coefficient σ p The calculation formula is σp (k)-σ p (k-1)≤f PL [v(k)], where I d (k) indicates whether the current driver has taken over. 1 indicates taking over, i.e. the driver's hand torque satisfies the hand torque threshold, hand torque time threshold and integral threshold at the same time; 0 indicates not taking over. d (k) is the current hand force integral value; f Pf is the integral value of hand force and σ p The corresponding relationship is fitted through testing; f PL is the vehicle speed and σ p The corresponding relationship of the gradient is fitted through testing.

[0020] In step S3, the I-phase Delta term attenuation coefficient σ iΔ The calculation formula is σ iΔ (k)-σ iΔ (k-1)≤f ΔIL [v(k)], where f ΔIf is the integral value of hand force and σ iΔ The corresponding relationship is fitted through testing; f ΔIL is the vehicle speed and σ iΔ The corresponding relationship of the gradient is fitted through testing.

[0021] 1. The method for calculating the torque of a steering system based on a dual-loop PID algorithm according to claim 1, characterized in that: in the step S4, the attenuation coefficient σ of the Delay term I is id The calculation formula is σ id (k)-σ id (k-1)≤f DIL [v(k),TBT a ,I Dir (k)], where I Dir is the current takeover state, which is divided into 0 for original same direction, 1 for original reverse direction, 2 for dynamic middle position, and 3 for dynamic end, and is fitted through testing; f DIL is vehicle speed, TBT a ,I Dir With σ iΔ The corresponding relationship of the gradient is fitted through testing.

[0022] In step S5, the hand torque compensation coefficient σ t The calculation formula is in, For TBTb ,I Dir With σ t The corresponding relationship of the gradient is fitted through testing.

[0023] In step S6, the calculation formula of the angle control torque is:

[0024] Where, TarMotTorq is the target motor torque, σ p is the P-phase attenuation coefficient, Kp is the proportional coefficient, TarAngSpd is the target angular velocity of the steering wheel, CurAngSpd is the actual angular velocity of the steering wheel, σ iΔ is the I-phase Delta term attenuation coefficient, Ki is the integral coefficient, σ id is the attenuation coefficient of the Delay term in the I term.

[0025] In step S6, the calculation formula for compensating hand torque is: Among them, TarTBT is the compensation hand torque, TBT is the current hand torque, σ t is the hand torque compensation coefficient.

[0026] The driver takeover situation is as follows:

[0027] (1) When the driver takes over the direction of the tire for the first time and the ADAS takes over again and returns it to 0°, the tire has a certain negative angle due to ground friction. The direction of the angle-controlled torque is to overcome this negative angle deformation and move in the positive direction. This torque is the output of the I-term Delay term.

[0028] (2) When the driver takes over the steering wheel in a negative direction for the second time, when the angle starts to change, the torque calculated by the P phase is in a positive direction, the torque calculated by the I phase Delta term is in a positive direction, and the basic assist direction generated by the hand force is in a negative direction. The system behaves as an angle control torque that prevents the steering wheel angle from changing.

[0029] (3) When the driver takes over the steering wheel in a positive direction for the second time, when the angle starts to change, the torque calculated by the P phase is in a negative direction, the torque calculated by the I phase Delta term is in a negative direction, and the basic assist direction generated by the hand force is in a positive direction. The system behaves as an angle control torque that prevents the steering wheel angle from changing.

[0030] Since tire deformation will drive the steering wheel to rotate in the negative direction, and after the human hand takes over completely, the angle control torque needs to be completely set to 0Nm. Therefore, when the direction of the second takeover is the same as the first takeover and is in the same negative direction, at the beginning of the takeover, the Delta items of P phase and I phase need to be set to 0 so that the torque generated by the basic power assistance can drive the steering wheel to rotate, while avoiding the sudden change in hand feel caused by the increase in the angle control torque and setting it to 0 after complete takeover; when the direction of the second takeover is opposite to that of the first takeover, at the beginning of the takeover, the Delta items of P phase and I phase are needed to help reduce the angle control torque. After complete takeover, the Delta items of P phase and I phase are set to 0, and the Delay item of I phase decays to 0Nm according to a certain attenuation coefficient.

[0031] In step S24, the target angle is calculated as: Among them, TarStrAng is the target angle, StrAng is the current steering wheel angle, is the gain coefficient, TarStrAngSpd is the target steering wheel speed, Δa is the angular acceleration, and Δt is the sampling time.

[0032] Compared with the prior art, the present invention provides a steering system torque calculation method based on a dual-loop PID algorithm, which uses the dual-loop PID algorithm to calculate the motor torque and control the steering wheel movement to achieve a target angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flowchart of the present invention.

[0034] Figure 2 It is a schematic diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] The angle control system involved in the present invention adopts a dual-loop PID algorithm to calculate the motor torque. The front loop part is to obtain the angle difference by subtracting the requested angle from the actual angle, and the angle control system calculates the target angular velocity according to the angle difference; the rear loop part is to obtain the angular velocity difference by subtracting the target angular velocity from the actual angular velocity, and the target motor torque is obtained by the angular velocity difference through the PID algorithm.

[0037] Taking the takeover by gently pulling the steering wheel as an example, the entire takeover process is divided into the following four stages:

[0038] Stage 1: When the driver applies hand force on the steering wheel with a low torque gradient, before the hand force exceeds the preset torque threshold and time threshold, as the hand force increases, the angle control torque also increases to offset the change in steering wheel angle caused by the increase in hand force. At this time, the steering wheel angle does not change;

[0039] Stage 2: When the hand force exceeds the preset torque threshold and time threshold, the angle control torque decays to before 0Nm. When the hand force exceeds the threshold, the angle control torque begins to decay, the basic assist torque will increase according to the current hand force, and the steering wheel will begin to turn. At this time, the changes in the basic assist torque and angle control torque will directly affect the current feel;

[0040] Stage 3: The angle control torque decays to 0, and the hand torque reaches the torque threshold and time threshold for ADAS to take over. At this time, it is completely in the basic power assist state;

[0041] Stage 4: The hand torque exceeds the torque threshold and time threshold for ADAS to take over. At this time, the steering wheel will quickly respond to the target steering wheel speed output by ADAS and respond to the target steering wheel angle output by ADAS.

[0042] The above four stages are similar to the situation of suddenly turning the steering wheel to take over. Stages 1, 2, and 4 will cause changes in the feel, affecting the driving experience. Based on this, this paper proposes a control strategy with adjustable feel for the driver or ADAS takeover angle control to solve the above problems.

[0043] The present invention adopts a dual-loop PID algorithm to calculate the motor torque and control the steering wheel movement to achieve the target angle.

[0044] The specific implementation method is as follows: the front loop part subtracts the requested angle from the actual angle to obtain the angle difference, and the angle control system calculates the target angular velocity based on the angle difference; the rear loop part subtracts the target angular velocity from the actual angular velocity to obtain the angular velocity difference, and the angular velocity difference is used to obtain the target motor torque through the PID algorithm. The target motor torque is converted into the actual motor torque through the gradient output to control the steering wheel rotation.

[0045] The parameters involved in the PID algorithm are calculated based on the vehicle speed, and the P, I, and D items are all equipped with motor torque limits at different vehicle speeds to prevent the risk of vehicle instability caused by rapid steering wheel rotation due to over-saturation of motor torque at high speeds.

[0046] The target motor torque is calculated as:

[0047] Among them, TarMotTorq is the target motor torque, TarAngSpd is the target angular velocity of the steering wheel, CurAngSpd is the actual angular velocity of the steering wheel, Kp is the proportional coefficient, Ki is the integral coefficient, and Kd is the differential coefficient.

[0048] The existing electronic power steering system calculates the power-assisting torque based on vehicle speed, hand torque value, etc., which is called the basic power-assisting mode. The basic power-assisting mode achieves steering requirements by controlling the motor.

[0049] The angle control function involved in the present invention can realize the decoupling of the basic power-assist mode and the angle control mode. When the angle control function is activated, if the hand torque size and duration do not meet the requirements, the steering is not changed in response to the hand torque value.

[0050] The control strategy with adjustable feel involved in the present invention is divided into two parts: driver takeover optimization strategy and ADAS takeover optimization strategy. The driver takeover optimization strategy aims to attenuate the angle control torque in advance and calculate different angle control torque attenuation coefficients and hand torque compensation coefficients according to the hand torque.

[0051] The specific process of the driver takeover optimization strategy is as follows:

[0052] (1) Set the vehicle speed range to 0-5 kph to calculate the different attenuation coefficients for stationary steering and dynamic steering;

[0053] (2) Set the hand torque threshold, hand torque time threshold and hand torque integral threshold. Each threshold value can be calibrated according to the vehicle speed;

[0054] (3) Calculate the P-phase attenuation coefficient σ based on the integral value p , I phase Delta term attenuation coefficient σ iΔ , the integral value is the accumulated value of the excess portion over time after the current hand torque exceeds the hand torque threshold;

[0055] (4) Based on the locked and stored hand force value TBT when it exceeds the hand torque threshold and the hand torque time threshold a , calculate the attenuation coefficient σ of the Delay term of I id , the hand force value TBT a The stored hand torque value that exceeds the hand force threshold and the hand torque time threshold at the same time;

[0056] (5) Based on the locked and stored hand force value TBT exceeding the hand torque integral threshold b , calculate the hand torque compensation coefficient σ t , the hand force value TBT b is the hand torque when the integral value in step S13 exceeds the integral threshold;

[0057] (6) Calculate the angle control torque and compensation torque and output them to the motor end.

[0058] P-phase attenuation coefficient σ p The calculation formula is σ p (k)-σp (k-1)≤f PL [v(k)], where I d (k) indicates whether the current driver has taken over. 1 indicates taking over, i.e. the driver's hand torque satisfies the hand torque threshold, hand torque time threshold and integral threshold at the same time; 0 indicates not taking over. d (k) is the current hand force integral value; f Pf is the integral value of hand force and σ p The corresponding relationship is fitted through testing; f PL is the vehicle speed and σ p The corresponding relationship of the gradient is fitted through testing.

[0059] I phase Delta term attenuation coefficient σ iΔ The calculation formula is σ iΔ (k)-σ iΔ (k-1)≤f ΔIL [v(k)], where f ΔIf is the integral value of hand force and σ iΔ The corresponding relationship is fitted through testing; f ΔIL is the vehicle speed and σ iΔ The corresponding relationship of the gradient is fitted through testing.

[0060] I term Delay term attenuation coefficient σ id The calculation formula is σ id (k)-σ id (k-1)≤f DIL [v(k),TBT a ,I Dir (k)], where I Dir is the current takeover state, which is divided into 0 for original same direction, 1 for original reverse direction, 2 for dynamic middle position, and 3 for dynamic end, and is fitted through testing; f DIL is vehicle speed, TBT a ,I Dir With σ iΔ The corresponding relationship of the gradient is fitted through testing.

[0061] Hand torque compensation coefficient σ t The calculation formula is in, For TBT b ,I Dir With σ t The corresponding relationship of the gradient is fitted through testing.

[0062] The calculation formula for angle control torque is:

[0063] Where, TarMotTorq is the target motor torque, σ p is the P-phase attenuation coefficient, Kp is the proportional coefficient, TarAngSpd is the target angular velocity of the steering wheel, CurAngSpd is the actual angular velocity of the steering wheel, σ iΔ is the I-phase Delta term attenuation coefficient, Ki is the integral coefficient, σ id is the attenuation coefficient of the Delay term in the I term.

[0064] The calculation formula for compensating hand torque is: Among them, TarTBT is the compensation hand torque, TBT is the current hand torque, σ t is the hand torque compensation coefficient.

[0065] It is further explained that in the in-situ working condition, whether the direction of the driver's two takeovers is consistent has a great impact on the feel of the car. For example, when the ADAS request angle is 0°, when the driver takes over the direction in the first time and the ADAS takes over again and returns to 0°, the tire has a certain negative angle due to ground friction. The direction of the torque controlled by the angle is to overcome this negative angle deformation to the positive direction. This torque is the output of the I item Delay item.

[0066] If the direction the driver takes over for the second time is negative, then when the angle starts to change, the torque direction calculated by the P phase is positive, the torque direction calculated by the I phase Delta item is positive, and the basic assist direction generated by the hand force is negative. The system behaves as an angle control torque that prevents the steering wheel angle from changing.

[0067] If the driver takes over the steering in a positive direction for the second time, when the angle starts to change, the torque direction calculated by the P phase is negative, the torque direction calculated by the I phase Delta item is negative, and the basic assist direction generated by the hand force is positive. The system behaves as an angle control torque that prevents the steering wheel angle from changing.

[0068] Since tire deformation will drive the steering wheel to rotate in the negative direction, and after the human hand completely takes over, the angle control torque needs to be completely set to 0Nm. Therefore, when the direction of the second takeover is the same as the first takeover direction and is in the same negative direction, at the beginning of the takeover, the Delta items of P phase and I phase need to be set to 0 so that the torque generated by the basic power assistance can drive the steering wheel to rotate, while avoiding the sudden change in the feel caused by the increase in the angle control torque and setting it to 0 after the complete takeover. When the direction of the second takeover is opposite to that of the first takeover, at the beginning of the takeover, the Delta items of P phase and I phase are needed to help reduce the angle control torque. After the complete takeover, the Delta items of P phase and I phase are set to 0, and the Delay item of I phase decays to 0Nm according to a certain attenuation coefficient.

[0069] Under driving conditions, similar to the original working conditions, the tire deformation becomes the vehicle's self-aligning torque, so the pipe connected to the middle position is consistent with the pipe connected in the same direction as the original position, and the pipe connected to the end position is consistent with the pipe connected in the opposite direction as the original position.

[0070] So the P phase attenuation coefficient σ is calculated according to the integral value p , I phase Delta term attenuation coefficient σ iΔ The same-direction connection needs to be set to 0 in the original working condition, the middle-position connection needs to be set in the dynamic working condition, and the hand force exceeds the torque threshold and time threshold.

[0071] It should be further explained that in order to avoid sudden steering wheel angle changes caused by tire deformation and dynamic self-centering, the attenuation coefficient of the Delay term in the I term σ id The hand force value TBT when exceeding the hand force threshold and time threshold is required a Perform correlation calculations to handle different driver takeover states.

[0072] The ADAS takeover optimization strategy aims to process the target angle curve and improve the abrupt feel caused by the rapid increase in the steering wheel starting angular velocity when responding to a high speed target angle request. Since the target angle rises rapidly within a period of time in response to a high speed angle request, the second-order derivative of the target angle is processed at the beginning of the request.

[0073] The specific process of ADAS takeover optimization is as follows:

[0074] (1) Detect the current exit from the driver takeover mode;

[0075] (2) Calculate the angular acceleration Δa by looking up the table according to the target speed;

[0076] (3) Gain coefficient φ1 according to vehicle speed;

[0077] (4) Calculate the target turning angle after processing.

[0078] The formula for calculating the target turning angle is: Among them, TarStrAng is the target angle, StrAng is the current steering wheel angle, is the gain coefficient, TarStrAngSpd is the target steering wheel speed, Δa is the angular acceleration, and Δt is the sampling time.

[0079] like Figure 2As shown, during the actual test, at 55s, TBT increases, indicating that the driver is applying hand torque to take over. When tbt meets the takeover requirements, the takeover state is set from 0 to 1, and the actual steering wheel angle StrAng deviates from the target angle TarStrAng in response to the driver's intervention; when 59s recognizes that tbt is weakened and meets the ADAS takeover requirements, the takeover state is set from 1 to 0, StrAng is executed to TarStrAng, and ADAS takeover is realized.

Claims

1. A steering system torque calculation method based on a dual-loop PID algorithm, comprising a dual-loop PID algorithm, wherein the dual-loop PID algorithm comprises a front loop part and a rear loop part; the front loop part: the angle difference is obtained by subtracting the requested angle from the actual angle, and the angle control system calculates the target angular velocity according to the angle difference; the rear loop part: the target angular velocity is obtained by subtracting the actual angular velocity from the target angular velocity, and the angular velocity difference is obtained by the PID algorithm to obtain the target motor torque, and the target motor torque is converted into the actual motor torque through the gradient output to control the steering wheel rotation, characterized in that: The steering system torque calculation method includes a driver takeover optimization strategy and an ADAS takeover optimization strategy. The driver takeover optimization strategy is as follows: S11, setting the vehicle speed range to 0-5 kph to calculate different attenuation coefficients for stationary steering and dynamic steering; S12, setting the hand torque threshold, hand torque time threshold and hand torque integral threshold. Each threshold value can be calibrated according to the vehicle speed; S13, calculate the P phase attenuation coefficient σ based on the integral value p , I phase Delta term attenuation coefficient σ iΔ , the integral value is the accumulated value of the excess portion over time after the current hand torque exceeds the hand torque threshold; S14, according to the locked and stored hand force value TBT when exceeding the hand force torque threshold and the hand force torque time threshold a , calculate the attenuation coefficient σ of the Delay term of I id , the hand force value TBT a The stored hand torque value that exceeds the hand force threshold and the hand torque time threshold at the same time; S15, according to the locked and stored hand force value TBT exceeding the hand torque integral threshold b , calculate the hand torque compensation coefficient σ t , the hand force value TBT b is the hand torque when the integral value in step S13 exceeds the integral threshold; S16, calculating the angle control torque and the compensation hand torque and outputting them to the motor end; The ADAS takeover optimization strategy is as follows: S21, detecting the current exit of the driver takeover mode; S22, looking up the table to calculate the angular acceleration Δa according to the target speed; S23, look up the gain coefficient φ1 according to the vehicle speed; S24, calculating the processed target turning angle.

2. The method for calculating steering system torque based on a dual-loop PID algorithm according to claim 1, characterized in that: The target motor torque is calculated as follows: Among them, TarMotTorq is the target motor torque, TarAngSpd is the target angular velocity of the steering wheel, CurAngSpd is the actual angular velocity of the steering wheel, Kp is the proportional coefficient, Ki is the integral coefficient, and Kd is the differential coefficient.

3. The method for calculating steering system torque based on a dual-loop PID algorithm according to claim 1, characterized in that: In step S13, the P phase attenuation coefficient σ p The calculation formula is σ p (k)-σ p (k-1)≤f PL [v(k)], where I d (k) indicates whether the current driver has taken over. 1 indicates taking over, i.e. the driver's hand torque satisfies the hand torque threshold, hand torque time threshold and integral threshold at the same time; 0 indicates not taking over. d (k is the current hand strength integral value; f Pf is the integral value of hand force and σ p The corresponding relationship is fitted through testing; f PL is the vehicle speed and σ p The corresponding relationship of the gradient is fitted through testing.

4. The method for calculating steering system torque based on a dual-loop PID algorithm according to claim 1, characterized in that: In step S13, the I-phase Delta term attenuation coefficient σ iΔ The calculation formula is σ iΔ (k)-σ iΔ (k-1)≤f ΔIL [v(k)], where f ΔIf is the integral value of hand force and σ iΔ The corresponding relationship is fitted through testing; f ΔIL is the vehicle speed and σ iΔ The corresponding relationship of the gradient is fitted through testing.

5. The method for calculating steering system torque based on a dual-loop PID algorithm according to claim 1, characterized in that: In step S14, the attenuation coefficient σ of the I-term Delay term is id The calculation formula is σ id (k)-σ id (k-1)≤f DIL [v(k),TBT a ,I Dir (k)], where I Dir is the current takeover state, which is divided into 0 for original same direction, 1 for original reverse direction, 2 for dynamic middle position, and 3 for dynamic end, and is fitted through testing; f DIL is vehicle speed, TBT a ,I Dir With σ iΔ The corresponding relationship of the gradient is fitted through testing.

6. The method for calculating steering system torque based on a dual-loop PID algorithm according to claim 1, characterized in that: In step S15, the hand torque compensation coefficient σ t The calculation formula is in, For TBT b ,I Dir With σ t The corresponding relationship of the gradient is fitted through testing.

7. The method for calculating steering system torque based on a dual-loop PID algorithm according to claim 1, characterized in that: In step S16, the calculation formula of the angle control torque is: Where, TarMotTorq is the target motor torque, σ p is the P-phase attenuation coefficient, Kp is the proportional coefficient, TarAngSpd is the target angular velocity of the steering wheel, CurAngSpd is the actual angular velocity of the steering wheel, σ iΔ is the I-phase Delta term attenuation coefficient, Ki is the integral coefficient, σ id is the attenuation coefficient of the Delay term in the I term.

8. The method for calculating steering system torque based on a dual-loop PID algorithm according to claim 1, characterized in that: In step S16, the calculation formula for compensating hand torque is: Among them, TarTBT is the compensation hand torque, TBT is the current hand torque, σ t is the hand torque compensation coefficient.

9. The method for calculating steering system torque based on a dual-loop PID algorithm according to claim 3, characterized in that: The driver takeover situation is as follows: (1) When the driver takes over the direction of the tire for the first time and the ADAS takes over again and returns it to 0°, the tire has a certain negative angle due to ground friction. The direction of the angle-controlled torque is to overcome this negative angle deformation and move in the positive direction. This torque is the output of the I-term Delay term. (2) When the driver takes over the steering wheel in a negative direction for the second time, when the angle starts to change, the torque calculated by the P phase is in a positive direction, the torque calculated by the I phase Delta term is in a positive direction, and the basic assist direction generated by the hand force is in a negative direction. The system behaves as an angle control torque that prevents the steering wheel angle from changing. (3) When the driver takes over the steering wheel in a positive direction for the second time, when the angle starts to change, the torque calculated by the P phase is in a negative direction, the torque calculated by the I phase Delta term is in a negative direction, and the basic assist direction generated by the hand force is in a positive direction. The system behaves as an angle control torque that prevents the steering wheel angle from changing. Since tire deformation will drive the steering wheel to rotate in the negative direction, and after the human hand completely takes over, the angle control torque needs to be completely set to 0Nm. Therefore, when the direction of the second takeover is the same as the first takeover direction, which is the negative direction, the Delta items of the P phase and the I phase need to be set to 0 at the beginning of the takeover so that the torque generated by the basic power assistance can drive the steering wheel to rotate, while avoiding the sudden change in the feel caused by the increase of the angle control torque and setting it to 0 after the complete takeover. When the direction of the second takeover is opposite to that of the first takeover, in the initial stage of takeover, the Delta items of the P phase and the I phase are needed to help reduce the angle control torque. After complete takeover, the Delta items of the P phase and the I phase are set to 0, and the Delay item of the I phase is attenuated to 0Nm according to a certain attenuation coefficient.

10. The method for calculating steering system torque based on a dual-loop PID algorithm according to claim 1, characterized in that: In step S24, the target angle is calculated as: Among them, TarStrAng is the target angle, StrAng is the current steering wheel angle, is the gain coefficient, TarStrAngSpd is the target steering wheel speed, Δa is the angular acceleration, and Δt is the sampling time.

Images