EPS system active return to normal state identification and correction method

Abstract

The application discloses an EPS system active return-to-center abnormal state recognition and correction method and relates to the technical field of automobile steering gears.The EPS system active return-to-center abnormal state recognition and correction method comprises the following abnormal state recognitions and corrections: 1, active return-to-center residual angle overlarge recognition and correction;2, active return-to-center oversteering recognition and correction;3, active return-to-center oscillation recognition and correction.In the application, in the driving process, the abnormal state of the active return-to-center function is recognized by the method designed in the application in the steady state and the transient state and is reasonably processed.The abnormal state detection method and the correction method proposed in the application can effectively recognize the steady state and the transient abnormal state in the active return-to-center control process.

Description

Technical Field

[0001] This invention relates to the field of automotive steering technology, and in particular to a method for identifying and correcting abnormal states in EPS (Electric Power Steering) systems that actively return to center. Background Technology

[0002] With social development and continuous technological progress, drivers and passengers have increasingly higher demands for driving comfort and safety. The electric power steering system (EPS) is a crucial component of the vehicle chassis actuator. To improve driver comfort, EPS systems need to have an active return-to-center function. The active return-to-center function involves the EPS system ECU determining the timing of return-to-center based on vehicle speed, steering wheel deviation angle, and driver's operating state. It calculates the active return-to-center assist torque in real time and outputs this torque through the power steering motor to improve the vehicle's steering return-to-center effect. As drivers and passengers' demands for overall vehicle comfort and safety continue to rise, EPS and ECUs place high reliability requirements on the status recognition and control performance of the active return-to-center function. Existing active return-to-center functions have several shortcomings, mainly reflected in:

[0003] 1. After the EPS system actively corrects itself, there is no assessment of its control performance under steady-state conditions. There is no effective means to identify and correct overshoot angles exceeding expectations.

[0004] 2. During real-time operation of the EPS system, the MCU monitors the status of sensor input signals to determine the active return-to-center status. This method can only detect whether there are abnormalities in relevant sensors during EPS system operation and then determine whether the active return-to-center function is available. It lacks the ability to identify transient states and judge abnormal control performance of the EPS system's active return-to-center function. There is no effective method to handle in real-time issues such as unconventional roads like gravel roads or other disturbances that affect the return-to-center performance.

[0005] In summary, conventional testing methods only detect sensor signals and leave the active homing function as either enabled or disabled, which is insufficient to meet the requirements for functional and performance stability testing.

[0006] Therefore, it is necessary to invent a method for identifying and correcting abnormal states in an EPS system to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a method for identifying and correcting abnormal states of the active return-to-center function in an EPS system, so as to solve the problem of monitoring and correcting abnormal states of the active return-to-center function and performance of the electric power steering system during operation, thereby improving the comfort of drivers and passengers and the safety under special working conditions.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for identifying and correcting abnormal states in an EPS system's active recovery mode, including the identification and correction of the following abnormal states:

[0009] I. Identification and Correction of Excessive Residual Angle in Active Return to Center: The excessive residual angle in active return to center is judged based on the steady-state mode of active return to center. When the return to center reaches a steady state, different residual angles should be met at different vehicle speeds. In road conditions such as high-speed lane changes and low-speed turns, excessive residual angles may pose safety hazards. Through data statistical analysis, a table of vehicle speeds and residual angle points is designed.

[0010] II. Active Return-to-center Over-identification and Correction: Active return-to-center over-identification is based on the transient mode of active return-to-center. When the electric power steering system actively returns to center and passes the zero point of the steering wheel angle, the system combines theoretical basis to judge the data analyzed by the ECU. When the return-to-center is in transient mode, the EPS system MCU sampling unit collects the vehicle speed v, main torque T1, steering wheel angle θ, and motor speed in real time.

[0011] III. Active Return-to-center Jitter Identification and Correction: Active return-to-center jitter is judged in the active return-to-center dynamic mode. The presence of return-to-center jitter in the EPS active return-to-center function is judged based on the return-to-center target current commutation frequency. Under different conditions and road conditions, different current commutation frequencies and frequencies under different road conditions are collected using experimental design. A frequency threshold is designed as the threshold f′ for judging return-to-center jitter. When active return-to-center jitter occurs, the return-to-center output is temporarily suppressed to 0. After active return-to-center jitter occurs more than 5 times, the return-to-center function output is suppressed until the commutation frequency returns to the normal range.

[0012] Preferably, in step S1, abnormal state identification is achieved by querying the vehicle speed and residual corner point table.

[0013] Preferably, when the active return-to-center operating mode is in a steady state at vehicle speed v, it is determined whether the active return-to-center residual angle meets the point table design. If the current steering wheel angle is greater than the fault detection threshold of the return-to-center residual angle, it is determined that the steady-state active return-to-center residual angle is too large.

[0014] Preferably, when the residual angle is too large, the return-to-center performance is corrected. The performance correction method is named the small-angle return-to-center compensation strategy. The steady-state closed-loop adjustment of small-angle return-to-center is carried out in combination with the design value of the maximum residual angle of different vehicle speed segments in the residual angle point table, i.e. the target residual angle, to reduce the return-to-center residual angle.

[0015] Preferably, in S2, the main moment T1 < T 死区Within the range, when the steering wheel angle approaches 0, if the motor speed is greater than the speed threshold, the number of judgments is accumulated. If a certain number of judgments are met, it is judged as active return to center overshoot. When return to center overshoots, the output is reduced proportionally, and the return target current is multiplied by 0.8, thereby reducing the return force to prevent overshoot.

[0016] The technical effects and advantages of this invention are as follows:

[0017] During driving, the abnormal state of the active self-centering function is identified and handled appropriately under both steady-state and transient conditions using the method designed in this invention.

[0018] The abnormal state detection and correction method proposed in this invention can effectively identify steady-state and transient abnormal states in the active homing control process;

[0019] The detection method for excessive residual angle during active self-centering in this invention can effectively identify abnormal states. Through small-angle closed-loop processing, the residual angle at different vehicle speeds can be controlled within a safe range. For excessive active self-centering, safety is provided by downgrading the active self-centering function. For active self-centering vibration, the abnormal states caused by interference and other factors during driving are filtered out by briefly suppressing the output of the active self-centering function, thereby reducing the impact of road disturbances on driving feel and comfort.

[0020] The above methods are particularly suitable for use on various road vehicles such as commercial vehicles and passenger cars, improving driving comfort while reducing the risks associated with road conditions such as turns. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the abnormal state identification and correction method of the present invention.

[0022] Figure 2 This is a schematic diagram of the small-angle closed-loop compensation of the present invention.

[0023] Figure 3 The motor output torque T of the present invention e Schematic diagram.

[0024] Figure 4 This is a block diagram of the pattern recognition of the present invention.

[0025] Figure 5 This is a schematic diagram illustrating the small-angle closed-loop control process performed when the residual angle of the present invention is too large.

[0026] Figure 6 This is a schematic diagram illustrating how the present invention reduces excessive synchro.

[0027] Figure 7 This is a schematic diagram of the jitter correction process of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides, for example Figure 1-7 The method shown is for identifying and correcting abnormal states in the EPS system's active recovery mode.

[0030] This invention is mainly applied to electric power steering systems with active return-to-center function. It detects anomalies in the return-to-center function based on the control results of the active return-to-center function and the current operating status of the EPS system.

[0031] This invention refers to any state that does not meet the ideal target during the active homing process as an abnormal state. These abnormal states, combined with the steady-state and transient processes of active homing, are categorized into three main types: excessive residual angle during active homing, over-homing, and active homing jitter. After detecting abnormal states, three abnormality correction methods are designed: small-angle homing closed-loop adjustment, homing function degradation, and short-term suppression of the homing function.

[0032] 1. Mathematical model of active return-to-center function of electric power steering system

[0033] The EPS system uses a permanent magnet synchronous motor, employing vector control to divide the stator current into excitation and torque components through motor field orientation, which are then controlled separately, thus achieving good decoupling characteristics. The EPS system's return-to-center function is mainly reflected in the control of the permanent magnet synchronous motor, and the active return-to-center function mainly involves the steering wheel angle, motor speed, and motor output torque.

[0034] The equivalent equation for steering wheel angle and motor torque is as follows:

[0035]

[0036] J q - Equivalent moment of inertia; B q - Equivalent damping system; T fq - Equivalent frictional torque; T e - Motor electromagnetic torque

[0037] θ - Current angle; ω - Current rotational speed; G - Reduction ratio of the reduction mechanism; r - Gear radius; F - Gear and rack friction force

[0038] Differentiating equation ② and substituting it into equation ① transforms it into a first-order system:

[0039]

[0040] 2. Active Correction Abnormal State Identification and Correction Algorithm

[0041] ① Active correction of excessive residual angle

[0042] This abnormal state assessment targets the active self-centering steady-state mode. When self-centering reaches a steady state, different residual angles should be satisfied at different vehicle speeds. In road conditions such as high-speed lane changes and low-speed turns, excessive residual angles can pose safety hazards. A table of vehicle speed ranges and residual angle points is designed using data statistical analysis.

[0043] Abnormal state identification strategy: Implemented by querying the vehicle speed and residual corner point table. When the active return-to-center operation mode is in a steady state at vehicle speed v, it is determined whether the active return-to-center residual angle meets the point table design. If the current steering wheel angle is greater than the residual return-to-center angle fault detection threshold, it is determined that the steady-state active return-to-center residual angle is too large.

[0044]

[0045] Table 1 Residual Corner Points Table

[0046] When the residual angle is too large, the self-alignment performance is corrected. This performance correction method is named the small-angle self-alignment compensation strategy. Based on the design value (i.e., the target residual angle) of the maximum residual angle for different vehicle speed ranges in the residual angle point table, steady-state closed-loop adjustment with a small angle self-alignment is performed to reduce the self-alignment residual angle. The specific implementation strategy is as follows: Figure 2 As shown.

[0047] ② Proactive over-identification and correction

[0048] This abnormal state is determined for the active return-to-center transient mode. The determination is made based on the data analyzed by the ECU during the active return-to-center process of the electric power steering system, when the steering wheel angle reaches its zero point. During the return-to-center transient mode, the EPS system MCU sampling unit collects vehicle speed v, main torque T1, steering wheel angle θ, and motor speed in real time.

[0049] Abnormal state identification strategy: When the main moment T1 < T 死区 Within the specified range, when the steering wheel angle approaches 0, if the motor speed exceeds the speed threshold, the number of judgments is accumulated. If a certain number of judgments are met, it is judged as excessive active return to center. When excessive return to center occurs, the output is reduced proportionally, and the return target current is multiplied by 0.8, thereby reducing the return force to prevent excessive return to center.

[0050]

[0051] Table 2. Motor Speed ​​Points at Zero Crossing Point

[0052] ③ Active jitter recognition and correction

[0053] This abnormal status is determined for the active homing dynamic mode.

[0054] Abnormal State Identification Strategy: The presence of back-alignment jitter in the EPS active back-alignment function is determined based on the commutation frequency of the EPS system's target back-alignment current. Under different conditions and road conditions, experimental designs are used to collect different current commutation frequencies and frequencies under different road conditions, and a frequency threshold f′ is designed as the threshold for determining back-alignment jitter. When all active back-alignment jitter occurs, a short-term suppression of the back-alignment output to 0 is performed. After more than 5 instances of active back-alignment jitter, the back-alignment function output is suppressed until the commutation frequency returns to the normal range.

[0055]

[0056] Table 3 Current Commutation Frequency Point Table

[0057] In practice:

[0058] 1. The MCU collects current EPS system operating information: vehicle speed v, steering wheel angle θ, motor speed w, and q-axis current i. q The MCU calculates the status information based on the currently collected information: motor output torque T e ,like Figure 3 As shown.

[0059] 2. Identify active alignment mode

[0060] like Figure 4 As shown, determine the vehicle speed v > 0, the motor speed ω, and the motor output torque T. e If the threshold condition is met, the mode is determined to be a steady state mode if the condition for returning to positive is met within a certain time period; otherwise, it is determined to be a transient mode.

[0061] Specific implementation methods for pattern recognition:

[0062] Calculate f(T) based on the electromagnetic torque of the motor e The formula is as follows:

[0063]

[0064] The formula for calculating f(ω) based on the motor speed is as follows:

[0065]

[0066] Substituting formulas ① and ② into the following formula, we obtain the cumulative change f(T) of the motor output torque and motor speed within a certain time interval ΔT = t - t1. e ,ω):

[0067]

[0068] Then combine the vehicle speed and f(T) e Substituting ω into the following formula, we can obtain the state of active homing:

[0069]

[0070] Where k is the threshold for the positive state.

[0071] 3. Active correction of abnormal states

[0072] 3.1 Excessive residual angle

[0073] When the steering wheel is in steady-state mode, the system queries a data table based on the vehicle speed and current steering wheel angle collected by the MCU. If the fault detection threshold is met, it determines that the current steering wheel angle value within a certain speed range is greater than the residual angle fault detection threshold, indicating that the steering wheel residual angle is too large. In this case, small-angle closed-loop control is executed. The implementation process is as follows: Figure 5 .

[0074] 3.2 Overcorrection

[0075] When the system is in transient mode during the centering phase, the EPS system's MCU sampling unit collects vehicle speed v, torque T1, and steering wheel angle θ in real time, and uses the steering wheel angle θ to calculate the steering wheel speed. When the main torque T1 is less than the dead zone and the steering wheel angle approaches 0, it is determined whether the steering wheel speed is too high, and the judgment result is obtained through fault-tolerant design.

[0076] If the correction is deemed excessive, the active correction function will be downgraded to reduce the excessive correction. Specific implementation details are as follows: Figure 6 .

[0077] 3.2 Backward jitter

[0078] First, determine that the positive return mode is in a steady state.

[0079] Secondly, when the vehicle speed and engine speed are both greater than 0, the number of commutations of the return-to-center current is statistically analyzed. The commutation frequency is calculated every 2ms. After calculation, a point query is performed; if the point table design is met, it is determined to be a return-to-center jitter. Upon determining that it is a return-to-center jitter, a short-term active return-to-center suppression process is immediately implemented. The specific implementation is as follows: Figure 7 .

Claims

1. A method for identifying and correcting abnormal states in an EPS system's active recovery mode, characterized in that, This includes the identification and correction of the following abnormal states: I. Identification and Correction of Excessive Residual Angle in Active Return to Center: The excessive residual angle in active return to center is judged based on the steady-state mode of active return to center. When the return to center reaches a steady state, different residual angles should be met at different vehicle speeds. In road conditions such as high-speed lane changes and low-speed turns, excessive residual angles may pose safety hazards. Through data statistical analysis, a table of vehicle speeds and residual angle points is designed. II. Active Return-to-center Over-identification and Correction: Active return-to-center over-identification is based on the transient mode of active return-to-center. When the electric power steering system actively returns to center and passes the zero point of the steering wheel angle, the system combines theoretical basis to judge the data analyzed by the ECU. When the return-to-center is in transient mode, the EPS system MCU sampling unit collects the vehicle speed v, main torque T1, steering wheel angle θ, and motor speed in real time.

3. Active return jitter identification and correction: Active return jitter is judged in the active return dynamic mode. The return target current commutation frequency of the EPS system is used to determine whether there is return jitter in the EPS active return function. Under different conditions and road conditions, different current commutation frequencies and frequencies under different road conditions are collected using experimental design. A frequency threshold is designed as the threshold f′ for judging return jitter. When active return jitter occurs, the return output is suppressed to 0 for a short time. After active return jitter occurs more than 5 times, the return function is suppressed until the commutation frequency returns to the normal range. The abnormal state identification is achieved by querying the vehicle speed and residual corner point table in the active correction residual angle excessive identification and correction process. When the active return-to-center operating mode is in a steady state at vehicle speed v, it is determined whether the active return-to-center residual angle meets the point table design. If the current steering wheel angle is greater than the return-to-center residual angle fault detection threshold, it is determined that the steady-state active return-to-center residual angle is too large. When the residual angle is too large, the return-to-center performance is corrected. The performance correction method is named the small-angle return-to-center compensation strategy. The steady-state closed-loop adjustment of small-angle return-to-center is carried out in combination with the design value of the maximum residual angle of different vehicle speed segments in the residual angle point table, i.e. the target residual angle, to reduce the return-to-center residual angle. The active over-identification and correction process is performed when the main moment T1 < T 死区 Within the range, when the steering wheel angle approaches 0, if the motor speed is greater than the speed threshold, the number of judgments is accumulated. If a certain number of judgments are met, it is judged as active return to center overshoot. When return to center overshoots, the output is reduced proportionally, and the return target current is multiplied by 0.8, thereby reducing the return force to prevent overshoot.

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