Torque control method of electronic power steering system

Abstract

The invention relates to the technical field of steering systems, in particular to a torque control method of an electronic power steering system. The invention discloses a torque control method of an electronic power steering system. The torque control method specifically comprises the following steps that (1) an EPS controller receives a working condition signal of the steering system in real time; (2) the basic assistance calculation module and various advanced function assistance calculation modules calculate the torque value of each independent function module; (3) the torque coupling processing module calculates a nominal torque request value according to a preset logic; and (4) the torque function safety processing module calculates an effective torque value to the motor. Compared with the prior art, firstly, each functional module can calculate a respective torque request value according to an input signal; then the coupling processing module carries out processing according to corresponding logic and outputs a total nominal torque request value; and then the function safety processing module carries out processing based on the mechanical characteristics and the adjustment and calibration requirements of the item to which the function safety processing module belongs, and outputs a final torque value.

Description

Technical Field

[0001] The present invention relates to the technical field of steering systems, in particular to a torque control method for an electronic power steering system. Background Art

[0002] With the advancement of intelligent driving technology, vehicles are increasingly equipped with more intelligent driving features. These include Lane Keeping Warning (LKA), Automatic Parking Control (APC), Lane Departure Warning (LDW), PDC (Progressive Direction Correction), and Rapid Acceleration Steering Torque Compensation (DTSC). Due to the rapid development of new intelligent driving technologies, the frequency of software version iterations has increased significantly. Functional failures and even loss of control are common. The urgent challenge is to ensure that, after the integration of these multiple functions, the failure or loss of control of some functions does not pose a threat to vehicle safety.

[0003] As the core mechanism for lateral control of the vehicle, the steering system plays an important role in most intelligent driving functions. Here, this method mainly focuses on the steering system to solve the corresponding problems. That is, as the corresponding functions of intelligent driving increase, there are situations where multiple functions are in effect at the same time under certain specific working conditions. Since the software architecture and development are based on modular thinking, different functions are relatively independent. Although each function has its own boundary value processing module, the superposition of various functions may result in output values ​​exceeding the boundary value at the system level, or leading to poor driving experience or even exceeding the limit of human operation. How to ensure that the superposition of multi-functional output torque does not affect the driving experience or even prevent steering out of control has become an urgent problem that needs to be solved. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a torque control method for an electronic power steering system, which not only solves the problem of multi-function superimposed torque value exceeding the limit, but also handles the problem of abnormal hand-beating.

[0005] To achieve the above objectives, a torque control method for an electronic power steering system is designed, comprising an EPS controller and a motor. The EPS controller includes a communication module, a basic power assist calculation module, various advanced power assist calculation modules, a torque coupling processing module, and a torque function safety processing module. The method is characterized by:

[0006] Step 1: The EPS controller receives the steering system's operating condition signals in real time, including steering wheel force, vehicle speed, EPS motor speed, and EPS motor terminal torque;

[0007] Step 2: The basic power assist calculation module and various advanced power assist calculation modules will calculate the torque value of each independent functional module according to the current working conditions, and then output it to the torque coupling processing module;

[0008] Step 3: The torque coupling processing module calculates the nominal torque request value based on the preset logic and outputs it to the torque function safety processing module;

[0009] Step 4: The torque function safety processing module calculates the effective torque value and sends it to the motor.

[0010] The formula for the logical calculation is Among them, HO is used to determine whether the driver's hands are controlling the steering wheel; a and b are calibration quantities, indicating the proportion of output torque values ​​of different functions when human control and some advanced functions are working, a + b = 1.

[0011] The workflow of the torque function safety processing module is as follows:

[0012] S41, start;

[0013] S42, monitors the nominal torque value;

[0014] S43, determining whether the nominal torque value triggers a stuck state, and if so, limiting the nominal torque value to a stuck state safety boundary value; otherwise, continuing to determine whether the nominal torque value triggers a loss of control;

[0015] S44, determining whether the nominal torque value triggers a loss of control; if so, limiting the nominal torque value to a loss of control safety boundary value; otherwise, setting the output value to the nominal torque value and ending;

[0016] S45, monitoring whether the stuck safety boundary value or the runaway safety boundary value of step S43 and step S44 is valid, if so, setting the output value to the nominal torque value and ending; otherwise, setting the output value to 0 and ending;

[0017] S46, end.

[0018] The safety boundary values ​​include the boundary value of the first quadrant, the boundary value of the second quadrant, the boundary value of the third quadrant, and the boundary value of the fourth quadrant.

[0019] The calculation formula for the boundary value of the first quadrant is ValidMotorTorque=AssistCurve+OffsetUAF; wherein ValidMotorTorque is the boundary value, AssistCurve is the power assist curve of the steering system, and OffsetUAF is the unexpected offset based on the vehicle speed, which is a calibration amount.

[0020] The calculation formula of the boundary value of the second quadrant is ValidMotorTorque= Among them, ValidMotorTorque is the boundary value, SteeringTorque is the hand force value, and OffsetUAF is the unexpected offset based on vehicle speed, which is the calibration amount.

[0021] The calculation formula for the boundary value of the third quadrant is ValidMotorTorque=AssistCurve-OffsetUAF; wherein ValidMotorTorque is the boundary value, AssistCurve is the power assist curve of the steering system, and OffsetUAF is the unexpected offset based on the vehicle speed, which is a calibration amount.

[0022] The calculation formula of the boundary value of the fourth quadrant is ValidMotorTorque= Among them, ValidMotorTorque is the boundary value, SteeringTorque is the hand force value, and OffsetUAF is the unexpected offset based on vehicle speed, which is the calibration amount.

[0023] If a vehicle is swerved to avoid a collision by a human or the intelligent driving system during driving, the conditions for entering an emergency state are:

[0024] (1) RotorSpeed ​​and NominalMotorTorque are in opposite directions;

[0025] (2) Steering Torque is less than 7 Nm;

[0026] (3) WeightedFailureIntegral weighted failure integral is 0;

[0027] Among them, RotorSpeed ​​is the EPS motor rotor speed; NominalMotorTorque is the nominal motor torque.

[0028] If the emergency condition is met, execute max as the boundary value, otherwise execute the original finite value curve.

[0029] The integration method of WeightedFailureIntegral is as follows: after NomianlMotorTorque exceeds a certain value of AssistCurve, WeightedFailureIntegral will integrate the time according to a fixed calibratable value, and the integral value will no longer increase after it reaches 1; when NomianlMotorTorque is less than the integral trigger limit, it will reverse the integration until it drops to 0.

[0030] Compared to the prior art, the present invention provides a torque control method for an electronic power steering system. First, each functional module calculates its own torque request value based on the input signal. Then, the coupling processing module processes it according to the corresponding logic and outputs the total nominal torque request value. Next, the functional safety processing module processes it based on the mechanical characteristics and adjustment requirements of the project to which it belongs and outputs the final torque value. Because some advanced functions will also output corresponding compensation torque based on the specific working conditions even when the driver does not apply manual force, and the compensation torque may even be in the opposite direction of the manual force, this method not only solves the problem of multi-function superimposed torque value exceeding the limit, but also handles the problem of abnormal hand-beating. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a software structure diagram of the present invention.

[0032] Figure 2 This is the overall workflow diagram of the torque function safety processing module of the present invention.

[0033] Figure 3 It is the effective torque value boundary diagram of the present invention.

[0034] Figure 4 This is the effective torque value expansion boundary diagram of the present invention.

[0035] Figure 5 This is the WeightedFailureIntegral integration principle diagram of the present invention.

[0036] Figure 6 This is the hand force data applied during the first quadrant experiment in Example 1 of the present invention.

[0037] Figure 7 This is the unprocessed expected motor torque experimental data in the first quadrant of Example 1 of the present invention.

[0038] Figure 8 It is the expected value finally output to the EPS motor after the corresponding logical operation of the present invention is performed in the first quadrant of embodiment 1 of the present invention.

[0039] Figure 9 This is the hand force data applied during the second quadrant experiment in Example 1 of the present invention.

[0040] Figure 10 This is the unprocessed expected motor torque experimental data in the second quadrant of Example 1 of the present invention.

[0041] Figure 11 It is the expected value finally output to the EPS motor after the corresponding logical operation of the present invention is performed in the second quadrant of embodiment 1 of the present invention.

[0042] Figure 12This is the hand force data applied during the first quadrant experiment in Example 2 of the present invention.

[0043] Figure 13 This is the unprocessed expected motor torque experimental data in the first quadrant of Example 2 of the present invention.

[0044] Figure 14 This is the weighted failure integral data of the first quadrant in Example 2 of the present invention.

[0045] Figure 15 It is the expected value finally output to the EPS motor after the corresponding logical operation of the present invention is performed in the first quadrant of embodiment 2 of the present invention.

[0046] Figure 16 This is the hand force data applied during the second quadrant experiment in Example 2 of the present invention.

[0047] Figure 17 This is the unprocessed expected motor torque experimental data in the second quadrant of Example 2 of the present invention.

[0048] Figure 18 This is the weighted failure integral data of the second quadrant in Example 2 of the present invention.

[0049] Figure 19 It is the expected value finally output to the EPS motor after the corresponding logical operation of the present invention is performed in the second quadrant of embodiment 2 of the present invention. DETAILED DESCRIPTION

[0050] The present invention will be further described below with reference to the accompanying drawings.

[0051] like Figure 1 As shown, a torque control method for an electronic power steering system includes an EPS controller and a motor. The EPS controller includes a communication module, a basic power assist calculation module, various advanced power assist calculation modules, a torque coupling processing module, and a torque function safety processing module. The specific method is as follows:

[0052] Step 1: The EPS controller receives the steering system's operating condition signals in real time, including steering wheel force, vehicle speed, EPS motor speed, and EPS motor terminal torque;

[0053] Step 2: The basic power assist calculation module and various advanced power assist calculation modules will calculate the torque value of each independent functional module according to the current working conditions, and then output it to the torque coupling processing module;

[0054] Step 3: The torque coupling processing module calculates the nominal torque request value based on the preset logic and outputs it to the torque function safety processing module;

[0055] Step 4: The torque function safety processing module calculates the effective torque value and sends it to the motor.

[0056] The formula for logical calculation is Among them, HO is used to determine whether the driver's hands are controlling the steering wheel; a and b are calibration quantities, indicating the proportion of output torque values ​​of different functions when human control and some advanced functions are working, a + b = 1.

[0057] like Figure 2 As shown in the figure, the workflow of the torque function safety processing module is as follows:

[0058] S41, start;

[0059] S42, monitors the nominal torque value;

[0060] S43, determining whether the nominal torque value triggers a stuck state, and if so, limiting the nominal torque value to a stuck state safety boundary value; otherwise, continuing to determine whether the nominal torque value triggers a loss of control;

[0061] S44, determining whether the nominal torque value triggers a loss of control; if so, limiting the nominal torque value to a loss of control safety boundary value; otherwise, setting the output value to the nominal torque value and ending;

[0062] S45, monitor whether the stuck safety boundary value or the runaway safety boundary value of step S43 and step S44 is valid. If it is valid, set the output value to the nominal torque value and end; otherwise, set the output value to 0 and end; see the valid value for details. Figure 3 As shown;

[0063] S46, end.

[0064] During normal operation, the torque function safety processing module may experience stuck or loss of control. Therefore, the effective torque value must be calculated based on the first, second, third, and fourth quadrant boundaries.

[0065] The calculation formula for the boundary value of the first quadrant is ValidMotorTorque = AssistCurve + OffsetUAF; where ValidMotorTorque is the boundary value, AssistCurve is the power assist curve of the steering system, and OffsetUAF is the unexpected offset based on the vehicle speed, which is a calibration amount.

[0066] OffsetUAF is a sign of loss of control or exceeding the driver's expectations. For example, it is calibrated to [0.0000 / 0.500000, 10.0000 / 0.500000, 30.0000 / 0.500000, 50.0000 / 0.500000, 80.0000 / 0.500000, 120.0000 / 0.500000, 180.0000 / 0.500000] kph / Nm.

[0067] The calculation formula for the boundary value of the second quadrant is Among them, ValidMotorTorque is the boundary value, SteeringTorque is the hand force value, and OffsetUAF is the unexpected offset based on vehicle speed, which is the calibration amount.

[0068] OffsetUAF is an unexpected offset based on vehicle speed. It is a calibrated value and serves as a marker for loss of control or exceeding driver expectations. For example, the calibration is [0.0000 / 0.500000, 10.0000 / 0.500000, 30.0000 / 0.500000, 50.0000 / 0.500000, 80.0000 / 0.500000, 120.0000 / 0.500000, 180.0000 / 0.500000] kph / Nm.

[0069] The calculation formula for the boundary value of the third quadrant is ValidMotorTorque = AssistCurve - OffsetUAF; where ValidMotorTorque is the boundary value, AssistCurve is the power assist curve of the steering system, and OffsetUAF is the unexpected offset based on the vehicle speed, which is a calibration amount.

[0070] OffsetUAF is an unexpected offset based on vehicle speed. It is a calibrated value and serves as a marker for loss of control or exceeding driver expectations. For example, the calibration is [0.0000 / 0.500000, 10.0000 / 0.500000, 30.0000 / 0.500000, 50.0000 / 0.500000, 80.0000 / 0.500000, 120.0000 / 0.500000, 180.0000 / 0.500000] kph / Nm.

[0071] The calculation formula for the boundary value of the fourth quadrant is ValidMotorTorque= Among them, ValidMotorTorque is the boundary value, SteeringTorque is the hand force value, and OffsetUAF is the unexpected offset based on vehicle speed, which is the calibration amount.

[0072] OffsetUAF is an unexpected offset based on vehicle speed. It is a calibrated value and serves as a marker for loss of control or exceeding driver expectations. For example, the calibration is [0.0000 / 0.500000, 10.0000 / 0.500000, 30.0000 / 0.500000, 50.0000 / 0.500000, 80.0000 / 0.500000, 120.0000 / 0.500000, 180.0000 / 0.500000] kph / Nm.

[0073] However, during the driving process, there are situations where the vehicle needs to swerve sharply to avoid a collision, either manually or by the intelligent driving system. For example, when turning right, an emergency situation may occur and the vehicle needs to swerve sharply to the left. In order to support such emergency situations, a point protection strategy is introduced. Figure 4 As shown in Figure 1, if the emergency condition is met, max(LimitCurve, LimtiExpansion) will be executed as the boundary value, otherwise the original finite value curve will be executed.

[0074] The conditions for entering an emergency are:

[0075] (1) RotorSpeed ​​and NominalMotorTorque are in opposite directions;

[0076] (2) Steering Torque is less than 7 Nm;

[0077] (3) WeightedFailureIntegral weighted failure integral is 0;

[0078] Where RotorSpeed ​​is the EPS motor rotor speed, and NominalMotorTorque is the nominal motor torque. LimitiExpansion is calibrated based on the EPS motor speed, for example, to [80 / 0.0, 150 / 1.5, 500 / 2.0] Nm / rpm.

[0079] The integration method of WeightedFailureIntegral is that when NomianlMotorTorque exceeds a certain value of AssistCurve, WeightedFailureIntegral will integrate the time according to a fixed calibrable value. After the integration reaches 1, the integral value will no longer increase. When NomianlMotorTorque is less than the integral trigger limit, the reverse integration will be performed until it drops to 0. See the integration principle. Figure 5 .

[0080] Case 1:

[0081] Case 1 is the normal mode, which is a basic limit curve mode with deviation. The limit curve consists of two parts: unexpected torque limit and sticking torque limit.

[0082] Unexpected torque limit: It comes from the fact that during normal driving, the torque value cannot exceed the limit too much along the power assist curve.

[0083] Stuck torque limit: This stuck comes from the stuck at the software level, that is, the calculated motor torque value is opposite to the direction of the hand force. The opposite is not completely prohibited, but only a certain deviation is allowed.

[0084] The limit curve can be obtained by superimposing the unexpected torque limit curve and the stuck torque limit curve.

[0085] Because the steering system is symmetrical for left and right steering, Figures 6 to 11 Only the performance of the EPS motor in the first and second quadrants in the HIL test is shown.

[0086] Quadrant 1: Test data when the vehicle speed is 50km / h and the hand force is 8Nm.

[0087] like Figure 6 As shown in Figure 2, the hand force data applied during the experiment (the data volume will be relatively large due to the sampling period of 1ms).

[0088] like Figure 7 Shown are the unprocessed expected motor torque experimental data.

[0089] like Figure 8 As shown, it is the expected value finally output to the EPS motor after applying the corresponding logical operation of the present invention.

[0090] Second quadrant: Test data when the vehicle speed is 50km / h and the hand force is gradually applied to -8Nm.

[0091] like Figure 9 The following table shows the hand force data applied during the experiment (the data volume is relatively large due to the 1ms sampling period).

[0092] like Figure 10 As shown, the unprocessed expected motor torque experimental data

[0093] like Figure 11 As shown, it is the expected value finally output to the EPS motor after applying the corresponding logical operation of the present invention.

[0094] Case 2:

[0095] Case 2 is the emergency mode. In this mode, the rotor speed is opposite to the direction of the manual force, which is equivalent to the manual force overcoming the motor resistance to do work.

[0096] When entering this mode, if the limit is exceeded, the torque will be limited to the maximum limit of the limit parallel to the X axis and the limit of the basic limit curve mode with deviation.

[0097] Because the steering system is symmetrical for left and right steering, the following only shows the performance of the EPS motors in the first and second quadrants during the HIL test.

[0098] Quadrant 1: Test data when the vehicle speed is 0 km / h and the hand force is 0.06 Nm.

[0099] like Figure 12 Shown are the hand force data applied during the experiment.

[0100] like Figure 13 Shown are the unprocessed expected motor torque experimental data.

[0101] like Figure 14 The data shown are weighted failure score data.

[0102] like Figure 15 As shown, it is the expected value finally output to the EPS motor after applying the corresponding logical operation of the present invention.

[0103] Second quadrant: test data when the vehicle speed is 0km / h and the hand force is -0.08Nm.

[0104] like Figure 16 Shown are the hand force data applied during the experiment.

[0105] like Figure 17 Shown are the unprocessed expected motor torque experimental data.

[0106] like Figure 18 The data shown are weighted failure score data.

[0107] like Figure 19 As shown, it is the expected value finally output to the EPS motor after applying the corresponding logical operation of the present invention.

Claims

1. A torque control method for an electronic power steering system, comprising an EPS controller and a motor, wherein the EPS controller includes a communication module, a basic power assist calculation module, various advanced power assist calculation modules, a torque coupling processing module, and a torque function safety processing module, characterized in that: The specific method is as follows: Step 1: The EPS controller receives the steering system's operating condition signals in real time, including steering wheel force, vehicle speed, EPS motor speed, and EPS motor terminal torque; Step 2: The basic power assist calculation module and various advanced power assist calculation modules will calculate the torque value of each independent functional module according to the current working conditions, and then output it to the torque coupling processing module; Step 3: The torque coupling processing module calculates the nominal torque request value based on the preset logic and outputs it to the torque function safety processing module; Step 4: The torque function safety processing module calculates the effective torque value and sends it to the motor.

2. The torque control method of an electronic power steering system according to claim 1, characterized in that: The formula for the logical calculation is Among them, HO is used to determine whether the driver's hands are controlling the steering wheel; a and b are calibration quantities, indicating the proportion of output torque values ​​of different functions when human control and some advanced functions are working, a + b = 1.

3. The torque control method of an electronic power steering system according to claim 1, characterized in that: The workflow of the torque function safety processing module is as follows: S41, start; S42, monitors the nominal torque value; S43, determining whether the nominal torque value triggers a jam, and if so, limiting the nominal torque value to a jam safety boundary value; Otherwise, continue to determine whether the nominal torque value triggers loss of control; S44, determining whether the nominal torque value triggers a loss of control; if so, limiting the nominal torque value to a loss of control safety boundary value; otherwise, setting the output value to the nominal torque value and ending; S45, monitoring whether the stuck safety boundary value or the runaway safety boundary value of step S43 and step S44 is valid, if so, setting the output value to the nominal torque value and ending; otherwise, setting the output value to 0 and ending; S46, end.

4. The torque control method of an electronic power steering system according to claim 3, characterized in that: The safety boundary values ​​include the boundary value of the first quadrant, the boundary value of the second quadrant, the boundary value of the third quadrant, and the boundary value of the fourth quadrant.

5. The torque control method of an electronic power steering system according to claim 4, characterized in that: The calculation formula for the boundary value of the first quadrant is ValidMotorTorque=AssistCurve+OffsetUAF; wherein ValidMotorTorque is the boundary value, AssistCurve is the power assist curve of the steering system, and OffsetUAF is the unexpected offset based on the vehicle speed, which is a calibration amount.

6. The torque control method of an electronic power steering system according to claim 4, characterized in that: The calculation formula for the boundary value of the second quadrant is: Among them, ValidMotorTorque is the boundary value, SteeringTorque is the hand force value, and OffsetUAF is the unexpected offset based on vehicle speed, which is the calibration amount.

7. The torque control method of an electronic power steering system according to claim 4, characterized in that: The calculation formula for the boundary value of the third quadrant is ValidMotorTorque=AssistCurve-OffsetUAF; wherein ValidMotorTorque is the boundary value, AssistCurve is the power assist curve of the steering system, and OffsetUAF is the unexpected offset based on the vehicle speed, which is a calibration amount.

8. The torque control method of an electronic power steering system according to claim 4, characterized in that: The calculation formula for the boundary value of the fourth quadrant is: Among them, ValidMotorTorque is the boundary value, SteeringTorque is the hand force value, and OffsetUAF is the unexpected offset based on vehicle speed, which is the calibration amount.

9. The torque control method of an electronic power steering system according to claim 1, characterized in that: If a vehicle is swerved to avoid a collision by a human or the intelligent driving system during driving, the conditions for entering an emergency state are: (1) RotorSpeed ​​and NominalMotorTorque are in opposite directions; (2) Steering Torque is less than 7 Nm; (3) Weighted Failure Integral The weighted failure integral is 0; Among them, RotorSpeed ​​is the EPS motor rotor speed; NominalMotorTorque is the nominal motor torque.

10. The torque control method of an electronic power steering system according to claim 9, characterized in that: If the emergency condition is met, execute max as the boundary value, otherwise execute the original finite value curve.

11. The torque control method of an electronic power steering system according to claim 9, characterized in that: The integration method of the Weighted Failure Integral is as follows: after NomianlMotorTorque exceeds a certain value of AssistCurve, the Weighted Failure Integral will integrate the time according to a fixed calibratable value. After the integration reaches 1, the integral value will no longer increase; when NomianlMotorTorque is less than the integral trigger limit, it will reverse the integration until it drops to 0.

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