A dynamic torque assist method based on EPS

Abstract

The present application relates to the technical field of steering system, in particular to a dynamic torque assistance method based on EPS.A dynamic torque assistance method based on EPS, the specific process is as follows: S1, function initialization;S2, judge whether a fault occurs;S3, judge whether the fault is eliminated;S4, activate dynamic torque assistance function;S5, judge whether the activation condition is met;S6, when the activation condition is met, the dynamic torque assistance function is activated, the expected dynamic torque response torque is output, and the response state is activated;S7, the EPS response is carried out transverse control through the torque within the safety limit;S8, check whether the response torque is within the safety limit.Compared with the prior art, a dynamic torque assistance method based on EPS is provided, which judges the conditions such as the driver's hand force, vehicle speed, and requested torque of the vehicle body stability system, so that the EPS provides appropriate torque to assist the driver in steering.

Description

Technical Field

[0001] This invention relates to the field of steering system technology, specifically to a dynamic torque assist method based on EPS. Background Technology

[0002] During vehicle operation, the electronic stability system identifies road surface information through sensors. When the left and right adhesion coefficients of the road surface are inconsistent, the driver's braking or acceleration will cause the vehicle body to sway significantly. The electronic stability system will send a command request to control the parking system through the anti-lock braking system (ABS) to control the longitudinal stability of the vehicle and maintain vehicle stability.

[0003] With the development of electronic stability systems, current electronic stability systems can send requested torque to the electronic power steering (EPS) system and interact with the dynamic torque assist function of the EPS system. The EPS system applies dynamic torque to assist the driver in steering. When the left and right adhesion coefficients of the road surface are inconsistent, the driver's braking or acceleration will cause the vehicle to become unstable, thus improving the vehicle's lateral stability. When understeer or oversteer occurs during cornering, lateral torque adjustment is performed to assist in cornering and improve the driving experience. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a dynamic torque assist method based on EPS, which judges conditions such as driver's hand force, vehicle speed, and the requested torque of the vehicle stability system, so that EPS provides appropriate torque to assist the driver in steering.

[0005] To achieve the above objectives, a dynamic torque assist method based on EPS is designed, characterized by the following specific process:

[0006] S1, Function initialization, output response dynamic torque auxiliary torque is 0, response state is initial state;

[0007] S2, determine if a fault has occurred; if yes, eliminate the fault; otherwise, continue to step S4.

[0008] S3, determine whether the fault has been eliminated. If yes, continue to step S4; otherwise, continue to monitor whether the fault has been eliminated. After a fault occurs, the output dynamic torque response torque is 0, the response status is fault, and the process ends.

[0009] S4, activate dynamic torque assist function;

[0010] S5. Determine whether the activation condition is met. If yes, continue to step S6; otherwise, continue to step S4.

[0011] S6, when the activation condition is met, the dynamic torque assist function is activated, and the expected dynamic torque response torque is output, and the output response state is activated.

[0012] S7, In order to make the response torque meet the functional safety requirements in ISO26262, the response torque is limited to ensure that the response torque is within the safety limit; the EPS response is laterally controlled by the torque that has been safely limited.

[0013] S8, check if the response torque is within the safety limit. If yes, end the process; otherwise, the dynamic torque assist function is abnormal, no longer execute the requested torque, the response torque limit is 0, the response status is fault, and the process ends.

[0014] In step S2, a recoverable fault is determined if any of the following conditions occur: dynamic torque assist function is not enabled, vehicle speed signal is invalid, request status is invalid, requested torque is invalid, vehicle speed is not within the range of 0-150 km / h, or request status is active and requested torque is greater than the upper limit value m. ReqTrq1 3Nm and duration t ReqTrq 100ms, request status is active and the requested torque change rate is greater than the upper limit value m ReqTrqGrad1 30 Nm / s and duration t ReqTrqGrad 100ms, steering wheel torque is opposite in direction to the requested torque and the steering wheel torque is greater than the upper limit value m trq1 3Nm and duration t trq1 500ms.

[0015] In step S2, the strategy for eliminating the fault is as follows:

[0016] (1) During the current ignition cycle, the requested torque exceeds the upper limit value m N times. ReqTrq1 3Nm and duration t ReqTrq At 100ms, a torque request fault message is issued via DTC diagnostic fault code, and the requested torque value and vehicle speed signal at the time of the fault are frozen; if the requested torque is less than the lower limit value m within 100s... ReqTrq2 When the value reaches 2.5 Nm, the cumulative count is reset to zero.

[0017] During the current ignition cycle, there have been N instances where the requested torque change rate exceeded the upper limit value m. ReqTrqGrad1 30 Nm / s and duration t ReqTrqGrad At 100ms, a request for torque change rate fault information is issued via DTC diagnostic fault code, and the requested torque change rate value and vehicle speed signal at the time of the fault are frozen; if the requested torque change rate is less than the lower limit value m within 100s... ReqTrqGrad2 When the speed reaches 30 Nm / s, the cumulative count is reset to zero;

[0018] (2) When the requested torque is greater than the upper limit value mReqTrq1 3Nm and duration t ReqTrq At 100ms, a torque request fault message is issued via DTC diagnostic fault code, and the requested torque value and vehicle speed signal at the time of the fault are frozen; when the requested torque is less than the lower limit value m ReqTrq2 At 2.5 Nm, clear the DTC diagnostic fault information;

[0019] When the requested torque change rate is greater than the upper limit value m ReqTrqGrad1 30 Nm / s and duration t ReqTrqGrad At 100ms, a request torque fault information is issued via DTC diagnostic fault code, and the requested torque change rate value and vehicle speed signal at the time of the fault are frozen; when the requested torque change rate is less than the lower limit value m ReqTrqGrad2 At 30 Nm / s, clear the DTC diagnostic fault information.

[0020] When the requested status or requested torque is invalid, the KL15 engine ignition signal is introduced. When KL15 = ON, that is, after the engine is ignited, the timing starts and continues for 3 seconds. Then, the host computer ESP system is determined to have a serious fault. At this time, the ESP system signal is unreliable, the response torque is limited to 0, and it enters a permanent fault state. The current ignition cycle will no longer be activated.

[0021] When the steering wheel torque is deemed to be exceeding the limit, the directions of both the steering wheel torque and the requested torque are considered. If the steering wheel torque and the requested torque are in the same direction (i.e., both the steering wheel torque and the requested torque are positive), or if both the steering wheel torque and the requested torque are negative, the dynamic torque assist function is considered to be assisting the driver's steering, and the steering wheel torque is not judged to be greater than the upper limit value m. trq1 3Nm and duration t trq1 500ms indicates a fault.

[0022] In step S6, the handshake is considered successful if the following conditions are met simultaneously: function enabled, request status is "request activation", no recoverable or permanent faults occur, vehicle speed signal is within the range of 0-150 km / h, and requested torque is less than the lower limit value m. ReqTrq2 2.5 Nm, requested torque change rate less than the lower limit m ReqTrqGrad2 30 Nm / s, steering wheel torque less than the lower limit m trq2 2.5 Nm and duration t trq2 200ms, EPS system is normal.

[0023] The specific process of step S8 is as follows:

[0024] S81 limits the amplitude of the response torque, such as when the current response torque is greater than or equal to the maximum response torque m. MaxTrq When the maximum response torque is reached, the output torque is the current response torque m.MaxTrq If the current response torque is less than the maximum response torque m MaxTrq When the current response torque is exceeded, the current response torque is output; simultaneously, the rate of change of the response torque after the amplitude limit is monitored. If the rate of change of the current response torque is greater than or equal to the maximum rate of change of the response torque m, the output torque is determined. MaxTrqGrad When the current output response torque is equal to the response torque of the previous cycle plus the maximum response torque change rate m, then the current output response torque is equal to the response torque of the previous cycle plus the maximum response torque change rate m. MaxTrqGrad If the current rate of change of response torque is less than the maximum rate of change of response torque m MaxTrqGrad When the current response torque is reached, the output torque is then given.

[0025] S82, if no excessive steering wheel torque fault occurs, then the maximum response torque change rate m MaxTrqGrad The maximum response torque is 30 Nm / s; if an excessive steering wheel torque fault occurs, the maximum response torque change rate is m. MaxTrqGrad It is 10 Nm / s;

[0026] S83 monitors the response torque after the amplitude and rate of change limits. If the current response torque exceeds the maximum response torque m... MaxTrq Or the current rate of change of response torque is greater than the maximum rate of change of response torque m. MaxTrqGrad If the response torque is reduced to 0 Nm, it is determined that the safety limit has failed. In this case, the dynamic torque assist function is considered to have a serious malfunction, and the response torque will be directly reduced to 0 Nm, instead of being calculated based on the maximum response torque change rate m. MaxTrqGrad The current ignition cycle cannot reactivate the dynamic torque assist function.

[0027] The maximum response torque m MaxTrq and the maximum response torque change rate m MaxTrqGrad As safety boundary values, the magnitude of the boundary values ​​at different vehicle speeds is related to the overall vehicle performance. Different vehicle models require vehicle failure injection tests to determine the boundary values.

[0028] The fault of excessive steering wheel torque is defined as the steering wheel torque being opposite in direction to the requested torque and the steering wheel torque being greater than the upper limit value mtrq13Nm for a duration of ttrq1500ms.

[0029] Compared with the prior art, the present invention provides a dynamic torque assistance method based on EPS, which judges the conditions such as driver's hand force, vehicle speed, and the requested torque of the vehicle stability system, so that EPS provides appropriate torque to assist the driver in steering. Attached Figure Description

[0030] Figure 1 This is a system architecture diagram for dynamic torque assist function.

[0031] Figure 2 This is a flowchart of the present invention. Detailed Implementation

[0032] The present invention will now be further described with reference to the accompanying drawings.

[0033] like Figure 1 As shown, the Dynamic Steering Torque Control (DTC) function of EPS receives the request status and requested torque signal from the ESP system, the vehicle speed signal from the ABS system, the steering wheel torque signal calculated by the steering wheel torque calculation module, and the EPS status signal output by the EPSECU system module. The Dynamic Torque Control handshake module then calculates the response status of the Dynamic Torque Control. When the response status is active, the Dynamic Torque Control handshake module outputs torque.

[0034] The dynamic torque assist safety limit module limits the output torque of the handshake module to meet the functional safety requirements of ISO26262 and prevents unintended steering.

[0035] The response torque obtained by the dynamic torque-assisted safety limiting module and the response status output by the dynamic torque-assisted handshake module are sent to the output signal processing module.

[0036] like Figure 2 As shown, a dynamic torque assist method based on EPS is described below, with the specific process as follows:

[0037] S1, Function initialization, output response dynamic torque auxiliary torque is 0, response state is initial state;

[0038] S2, determine if a fault has occurred; if yes, eliminate the fault; otherwise, continue to step S4.

[0039] S3, determine whether the fault has been eliminated. If yes, continue to step S4; otherwise, continue to monitor whether the fault has been eliminated. After a fault occurs, the output dynamic torque response torque is 0, the response status is fault, and the process ends.

[0040] S4, activate dynamic torque assist function;

[0041] S5. Determine whether the activation condition is met. If yes, continue to step S6; otherwise, continue to step S4.

[0042] S6, when the activation condition is met, the dynamic torque assist function is activated, and the expected dynamic torque response torque is output, and the output response state is activated.

[0043] S7, In order to make the response torque meet the functional safety requirements in ISO26262, the response torque is limited to ensure that the response torque is within the safety limit; the EPS response is laterally controlled by the torque that has been safely limited.

[0044] S8, check if the response torque is within the safety limit. If yes, end the process; otherwise, the dynamic torque assist function is abnormal, no longer execute the requested torque, the response torque limit is 0, the response status is fault, and the process ends.

[0045] In step S2, a recoverable fault is determined if any of the following conditions occur: dynamic torque assist function is not enabled, vehicle speed signal is invalid, request status is invalid, requested torque is invalid, vehicle speed is not within the range of 0-150 km / h, or request status is active and requested torque is greater than the upper limit value m. ReqTrq1 3Nm and duration t ReqTrq 100ms, request status is active and the requested torque change rate is greater than the upper limit value m ReqTrqGrad1 30 Nm / s and duration t ReqTrqGrad 100ms, steering wheel torque is opposite in direction to the requested torque and the steering wheel torque is greater than the upper limit value m trq1 3Nm and duration t trq1 500ms.

[0046] In step S2, the strategy for eliminating the fault is as follows:

[0047] (3) The current ignition cycle has accumulated N instances where the requested torque is greater than the upper limit value m. ReqTrq1 3Nm and duration t ReqTrq At 100ms, a torque request fault message is issued via DTC diagnostic fault code, and the requested torque value and vehicle speed signal at the time of the fault are frozen; if the requested torque is less than the lower limit value m within 100s... ReqTrq2 When the value reaches 2.5 Nm, the cumulative count is reset to zero.

[0048] During the current ignition cycle, there have been N instances where the requested torque change rate exceeded the upper limit value m. ReqTrqGrad1 30 Nm / s and duration t ReqTrqGrad At 100ms, a request for torque change rate fault information is issued via DTC diagnostic fault code, and the requested torque change rate value and vehicle speed signal at the time of the fault are frozen; if the requested torque change rate is less than the lower limit value m within 100s... ReqTrqGrad2 When the speed reaches 30 Nm / s, the cumulative count is reset to zero;

[0049] (4) When the requested torque is greater than the upper limit value m ReqTrq1 3Nm and duration t ReqTrq At 100ms, a torque request fault message is issued via DTC diagnostic fault code, and the requested torque value and vehicle speed signal at the time of the fault are frozen; when the requested torque is less than the lower limit value m ReqTrq2 At 2.5 Nm, clear the DTC diagnostic fault information;

[0050] When the requested torque change rate is greater than the upper limit value m ReqTrqGrad130 Nm / s and duration t ReqTrqGrad At 100ms, a request torque fault information is issued via DTC diagnostic fault code, and the requested torque change rate value and vehicle speed signal at the time of the fault are frozen; when the requested torque change rate is less than the lower limit value m ReqTrqGrad2 At 30 Nm / s, clear the DTC diagnostic fault information.

[0051] The two strategies mentioned above can be selected according to different test calibration environments. The purpose of making the upper limit of torque mReqTrq1 greater than the lower limit of torque mReqTrq2 is to avoid frequent fluctuations of the requested torque near the 3Nm boundary value, which would lead to frequent fault reports.

[0052] The above upper limit, lower limit, and duration are calibration reference values. They can be calibrated based on actual vehicle testing, or they can all be replaced by formulas.

[0053] Determining the range of requested torque and rate of change requires confirming that the request status is active in order to prevent frequent malfunctions in the dynamic torque assist function response status when the vehicle stability system is not requested to be activated.

[0054] Both of the above strategies can identify the cause of the fault by diagnosing the fault code, and can also identify the faulty value by diagnosing the frozen fault request torque, request torque change rate, and vehicle speed signal.

[0055] When the requested status or requested torque is invalid, the KL15 engine ignition signal is introduced. When KL15 = ON, that is, after the engine is ignited, the timing starts and continues for 3 seconds. Then, the host computer ESP system is determined to have a serious fault. At this time, the ESP system signal is unreliable, the response torque is limited to 0, and it enters a permanent fault state. The current ignition cycle will no longer be activated.

[0056] The reason for checking the KL15 signal is as follows: When KL15 frequently wakes up from sleep mode, the EPS is not completely asleep, while other nodes are asleep, causing the signal to stop. At this time, the EPS will still receive an invalid signal. If timing starts at this point, the ESP node will appear to be working correctly, but the dynamic torque assist function will still be in a permanent fault state, preventing the function from being activated in the current ignition cycle. Therefore, this logic is checked only after KL15 is ON and the engine is ignited.

[0057] When the steering wheel torque is deemed to be exceeding the limit, the directions of both the steering wheel torque and the requested torque are considered. If the steering wheel torque and the requested torque are in the same direction (i.e., both the steering wheel torque and the requested torque are positive), or if both the steering wheel torque and the requested torque are negative, the dynamic torque assist function is considered to be assisting the driver's steering, and the steering wheel torque is not judged to be greater than the upper limit value m. trq1 3Nm and duration t trq1 500ms indicates a fault.

[0058] In step S6, the handshake is considered successful if the following conditions are met simultaneously: function enabled, request status is "request activation", no recoverable or permanent faults have occurred, vehicle speed signal is within the range of 0-150 km / h, and requested torque is less than the lower limit value (m). ReqTrq2 2.5 Nm, requested torque change rate less than the lower limit m ReqTrqGrad2 30 Nm / s, steering wheel torque less than the lower limit m trq2 2.5 Nm and duration t trq2 200ms, EPS system is normal.

[0059] The specific process of step S8 is as follows:

[0060] S81 limits the amplitude of the response torque, such as when the current response torque is greater than or equal to the maximum response torque m. MaxTrq When the maximum response torque is reached, the output torque is the current response torque m. MaxTrq If the current response torque is less than the maximum response torque m MaxTrq When the current response torque is exceeded, the current response torque is output; simultaneously, the rate of change of the response torque after the amplitude limit is monitored. If the rate of change of the current response torque is greater than or equal to the maximum rate of change of the response torque m, the output torque is determined. MaxTrqGrad When the current output response torque is equal to the response torque of the previous cycle plus the maximum response torque change rate m, then the current output response torque is equal to the response torque of the previous cycle plus the maximum response torque change rate m. MaxTrqGrad If the current rate of change of response torque is less than the maximum rate of change of response torque m MaxTrqGrad When the current response torque is reached, the output torque is then given.

[0061] S82, if no excessive steering wheel torque fault occurs, then the maximum response torque change rate m MaxTrqGrad The maximum response torque is 30 Nm / s; if an excessive steering wheel torque fault occurs, the maximum response torque change rate is m. MaxTrqGrad It is 10 Nm / s;

[0062] S83 monitors the response torque after the amplitude and rate of change limits. If the current response torque exceeds the maximum response torque m... MaxTrq Or the current rate of change of response torque is greater than the maximum rate of change of response torque m. MaxTrqGrad If the response torque is reduced to 0 Nm, it is determined that the safety limit has failed. In this case, the dynamic torque assist function is considered to have a serious malfunction, and the response torque will be directly reduced to 0 Nm, instead of being calculated based on the maximum response torque change rate m. MaxTrqGrad The current ignition cycle cannot reactivate the dynamic torque assist function.

[0063] Maximum response torque m MaxTrq and the maximum response torque change rate m MaxTrqGradAs safety boundary values, the magnitude of the boundary values ​​at different vehicle speeds is related to the overall vehicle performance. Different vehicle models require vehicle failure injection tests to determine the boundary values.

[0064] The excessive steering wheel torque fault is defined as the steering wheel torque being in the opposite direction to the requested torque and exceeding the upper limit value mtrq13Nm for a duration ttrq1500ms.

[0065] The upper limit value of torque m mentioned in the above steps ReqTrq1 Torque lower limit m ReqTrq2 Upper limit of torque change rate m ReqTrqGrad1 Lower limit of torque change rate m ReqTrqGrad2 Maximum response torque m MaxTrq and the maximum response torque change rate m MaxTrqGrad Strongly correlated with vehicle speed, at lower speeds, larger torque, torque change rate, steering wheel torque, response torque, and response torque change rate are permissible. At higher speeds, these parameters must be correspondingly reduced to ensure safe torque is provided at various speeds, guaranteeing vehicle controllability. For example, when the vehicle speed is between 0 and 30 km / h, the maximum response torque (m)... MaxTrq The maximum torque is 3 Nm; when the vehicle speed is greater than 100 km / h, the maximum response torque is [m]. MaxTrq The maximum response torque is 2 Nm; when the vehicle speed is in the range of 30 km / h to 100 km / h, the maximum response torque is [m]. MaxTrq Linear interpolation is performed in the range of 3Nm to 2Nm.

[0066] The advantages of this invention are: ① The judgment condition for steering wheel torque incorporates direction, which can better determine the driver's intention and avoid the dynamic torque assist function disengaging due to excessive steering wheel torque when the EPS torque assist direction is the same as the driver's intention. When the dynamic torque assist function disengages due to excessive steering wheel torque, the response torque change rate is limited to 10 Nm / s to ensure driving comfort; otherwise, the response change rate is limited to 30 Nm / s.

[0067] ②Vehicle speed conditions are introduced for the boundary values ​​of requested torque, requested torque change rate, steering wheel torque, response torque, and response torque change rate. When the vehicle speed is low, the limit is increased; when the vehicle speed is high, the limit is smaller.

[0068] ③ Optional diagnostic fault strategies and signal invalidation to permanent fault strategies can be selected flexibly according to the debugging situation in order to adapt to more customer needs.

[0069] ④ Two fault diagnosis strategies are provided. When the requested torque exceeds the limit or the requested torque change rate exceeds the limit, the fault request signal and vehicle speed can be frozen to investigate the cause of the error.

[0070] ⑤ When determining that the signal is invalid and entering a fault, the KL15 engine ignition signal must also be checked. When the engine is ignited and the request signal is invalid, the timer starts to avoid permanent failure of the dynamic torque assist function caused by the EPS not being in sleep mode while other nodes are in sleep mode due to frequent wake-up of sleep mode.

[0071] ⑥ A control strategy for response torque is provided. When no safety failure occurs that exceeds the safety limit, the amplitude and rate of change are limited. When a safety failure occurs that exceeds the safety limit, such as the amplitude or slope limit failing, the response torque should be reduced to 0 directly.

Claims

1. A dynamic torque assist method based on EPS, characterized in that: The specific process is as follows: S1, Function initialization, output response dynamic torque auxiliary torque is 0, response state is initial state; S2, determine if a fault has occurred; if yes, eliminate the fault; otherwise, continue to step S4. S3, determine whether the fault has been eliminated. If yes, continue to step S4; otherwise, continue to monitor whether the fault has been eliminated. After a fault occurs, the output dynamic torque response torque is 0, the response status is fault, and the process ends. S4, activate dynamic torque assist function; S5. Determine whether the activation condition is met. If yes, continue to step S6; otherwise, continue to step S4. S6, When the activation condition is met, the dynamic torque assist function is activated, and the expected dynamic torque response torque is output. The output response state is activated. S7. In order to make the response torque meet the functional safety requirements in ISO 26262, the response torque is limited to ensure that the response torque is within the safety limit. EPS response uses lateral control based on torque limits for safety purposes; S8, check if the response torque is within the safety limit. If yes, the process ends; otherwise, the dynamic torque assist function is abnormal, the requested torque is no longer executed, the response torque limit is 0, the response status is fault, and the process ends. In step S2, the strategy for eliminating the fault is as follows: (1) During the current ignition cycle, the requested torque exceeds the upper limit value m N times. ReqTrq1 3Nm and duration t ReqTrq At 100ms, a torque request fault message is issued via DTC diagnostic fault code, and the requested torque value and vehicle speed signal at the time of the fault are frozen; if the requested torque is less than the lower limit value m within 100s... ReqTrq2 When the value reaches 2.5 Nm, the cumulative count is reset to zero. During the current ignition cycle, there have been N instances where the requested torque change rate exceeded the upper limit value m. ReqTrqGrad1 30 Nm / s and duration t ReqTrqGrad At 100ms, a request for torque change rate fault information is issued via DTC diagnostic fault code, and the requested torque change rate value and vehicle speed signal at the time of the fault are frozen; if the requested torque change rate is less than the lower limit value m within 100s... ReqTrqGrad2 When the speed reaches 30 Nm / s, the cumulative count is reset to zero; (2) When the requested torque is greater than the upper limit value m ReqTrq1 3Nm and duration t ReqTrq At 100ms, a torque request fault message is issued via DTC diagnostic fault code, and the requested torque value and vehicle speed signal at the time of the fault are frozen; when the requested torque is less than the lower limit value m ReqTrq2 At 2.5 Nm, clear the DTC diagnostic fault information; (3) When the requested torque change rate is greater than the upper limit value m ReqTrqGrad1 30 Nm / s and duration t ReqTrqGrad At 100ms, a request for torque change rate fault information is issued via DTC diagnostic fault code, and the requested torque change rate value and vehicle speed signal at the time of the fault are frozen; when the requested torque change rate is less than the lower limit value m ReqTrqGrad2 At 30 Nm / s, clear the DTC diagnostic fault information.

2. The dynamic torque assist method based on EPS according to claim 1, characterized in that: In step S2, a recoverable fault is determined if any of the following conditions occur: dynamic torque assist function is not enabled, vehicle speed signal is invalid, request status is invalid, requested torque is invalid, vehicle speed is not within the range of 0-150 km / h, or request status is active and requested torque is greater than the upper limit value m. ReqTrq1 3Nm and duration t ReqTrq 100ms, request status is active and the requested torque change rate is greater than the upper limit value m ReqTrqGrad1 30 Nm / s and duration t ReqTrqGrad 100ms, steering wheel torque is opposite in direction to the requested torque and the steering wheel torque is greater than the upper limit value m trq1 3Nm and duration t trq1 500ms.

3. The dynamic torque assist method based on EPS according to claim 2, characterized in that: When the requested status or requested torque is invalid, the KL15 engine ignition signal is introduced. When KL15 = ON, that is, after the engine is ignited, the timing starts and continues for 3 seconds. Then, the host computer ESP system is determined to have a serious fault. At this time, the ESP system signal is unreliable, the response torque is limited to 0, and it enters a permanent fault state. The current ignition cycle will no longer be activated.

4. The dynamic torque assist method based on EPS according to claim 2, characterized in that: When the steering wheel torque is deemed to be exceeding the limit, the directions of both the steering wheel torque and the requested torque are considered. If the steering wheel torque and the requested torque are in the same direction (i.e., both the steering wheel torque and the requested torque are positive), or if both the steering wheel torque and the requested torque are negative, the dynamic torque assist function is considered to be assisting the driver's steering, and the steering wheel torque is not judged to be greater than the upper limit value m. trq1 3Nm and duration t trq1 500ms indicates a fault.

5. The dynamic torque assist method based on EPS according to claim 1, characterized in that: In step S6, the handshake is considered successful if the following conditions are met simultaneously: function enabled, request status is "request activation", no recoverable or permanent faults occur, vehicle speed signal is within the range of 0-150 km / h, and requested torque is less than the lower limit value m. ReqTrq2 2.5 Nm, requested torque change rate less than the lower limit m ReqTrqGrad2 30 Nm / s, steering wheel torque less than the lower limit m trq2 2.5 Nm and duration t trq2 200ms, EPS system is normal.

6. The dynamic torque assist method based on EPS according to claim 1, characterized in that: The specific process of step S8 is as follows: S81 limits the amplitude of the response torque, such as when the current response torque is greater than or equal to the maximum response torque m. MaxTrq When the maximum response torque is reached, the output torque is the current response torque m. MaxTrq If the current response torque is less than the maximum response torque m MaxTrq When the current response torque is exceeded, the current response torque is output; simultaneously, the rate of change of the response torque after the amplitude limit is monitored. If the rate of change of the current response torque is greater than or equal to the maximum rate of change of the response torque m, the output torque is determined. MaxTrqGrad When the current output response torque is equal to the response torque of the previous cycle plus the maximum response torque change rate m, then the current output response torque is equal to the response torque of the previous cycle plus the maximum response torque change rate m. MaxTrqGrad If the current rate of change of response torque is less than the maximum rate of change of response torque m MaxTrqGrad When the current response torque is reached, it will be output. S82, if no excessive steering wheel torque fault occurs, then the maximum response torque change rate m MaxTrqGrad It is 30 Nm / s; If a steering wheel torque malfunction occurs, the maximum response torque change rate m MaxTrqGrad It is 10 Nm / s; S83 monitors the response torque after the amplitude and rate of change limits. If the current response torque exceeds the maximum response torque m... MaxTrq Or the current rate of change of response torque is greater than the maximum rate of change of response torque m. MaxTrqGrad If the current response torque is reduced to 0 Nm, it is determined that the safety limit has failed. In this case, the dynamic torque assist function is considered to have a serious malfunction, and the current response torque is directly reduced to 0 Nm, instead of being adjusted according to the maximum response torque change rate m. MaxTrqGrad The current ignition cycle cannot reactivate the dynamic torque assist function.

7. The dynamic torque assist method based on EPS according to claim 6, characterized in that: The maximum response torque m MaxTrq and the maximum response torque change rate m MaxTrqGrad As safety boundary values, the magnitude of the boundary values ​​at different vehicle speeds is related to the overall vehicle performance. Different vehicle models require vehicle failure injection tests to determine the boundary values.

8. The dynamic torque assist method based on EPS according to claim 6, characterized in that: The fault of excessive steering wheel torque is defined as the steering wheel torque being opposite in direction to the requested torque and the steering wheel torque being greater than the upper limit value mtrq13Nm for a duration of ttrq1500ms.

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