Low-temperature friction compensation method for steering engine

Abstract

The invention relates to the technical field of electric steering systems, in particular to a steering engine low-temperature friction compensation method which comprises the following steps: step 1, an effective torque value calculation module calculates and outputs effective torque; 2, a torque lag calculation module calculates and outputs an effective torque lag value; 3, a friction torque confirmation module judges and outputs the friction torque of the current period; 4, a torque compensation calculation module calculates compensation torque and outputs the compensation torque; and step 5, limiting the friction torque which is actually compensated by a limiting torque compensation module. Compared with the prior art, mechanical energy loss caused by friction of the system is obtained within a certain angle range by identifying lag of the effective torque during steering and reversing, the effective torque lag value of the system is calculated, and the compensation torque needed by the system is further obtained. The limit value of the compensation torque is increased in the low-temperature environment, and it is guaranteed that the whole steering system can provide normal compensation torque in various environments.

Description

Technical Field

[0001] The invention relates to the technical field of electric steering systems, in particular to a steering gear low-temperature friction compensation method. Background Art

[0002] With the development of automobile electrification, the requirements of OEMs or end users for vehicle use are constantly increasing. As a system with multiple mechanical devices coupled, the steering gear will generate friction in each friction pair during operation. This friction will be reflected in the form of a hysteresis effect on the system side, that is, when the driver makes a steering action, due to the existence of friction, the hand torque must first overcome the friction torque, and then the steering wheel angle will change. The steering wheel angle always lags behind the hand torque. At the same time, after the steering is reversed, this hysteresis effect will cause different steering feels in different steering directions at the same steering wheel angle position, and at low temperatures, the impact of this friction will be more significant, affecting the driving experience and even creating safety risks.

[0003] At present, the system will calculate the actual friction torque based on the hysteresis of the effective torque, and provide the corresponding torque within a limited range according to the value of the friction torque to compensate for the friction effect, thereby improving the control performance of the system. However, the limit value of the torque compensation will not be adjusted with the temperature, that is, the limit value of the compensated torque is the same under normal temperature and low temperature environments. This will result in the torque compensation being limited to a smaller torque when the system may need a larger torque compensation in a low temperature environment. At this time, the torque compensation provided by the system cannot offset the feel caused by the friction force, affecting the driver's driving experience and even creating safety risks.

[0004] Therefore, it is necessary to design a steering gear low-temperature friction compensation method that can use torque compensation curves with different limit values ​​in normal temperature and low temperature environments, so as to provide appropriate torque compensation in different temperature environments, provide the driver with a comfortable steering feel, and reduce safety risks. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a steering gear low-temperature friction compensation method, which can adopt torque compensation curves with different limit values ​​in normal temperature environment and low temperature environment, so as to provide appropriate torque compensation in different temperature environments, provide the driver with a comfortable steering feel, and reduce safety risks.

[0006] In order to achieve the above-mentioned purpose, the present invention is a steering gear low-temperature friction compensation method, comprising the following steps: step 1, an effective torque value calculation module calculates and outputs the effective torque according to the input motor torque, input shaft torque and gear direction signal; step 2, a torque lag calculation module calculates and outputs the effective torque lag value according to the input vehicle speed, motor speed, steering angle and effective torque; step 3, a friction torque confirmation module judges and outputs the friction torque of this cycle according to the input effective torque lag value; step 4, a torque compensation calculation module calculates and outputs the compensation torque according to the input friction torque of this cycle, the friction torque stored in the previous cycle, the friction compensation mode switching flag, and the effective torque; step 5, a limiting torque compensation module limits the actual compensated friction torque according to the input compensation torque, ECU temperature, and the friction torque of this cycle.

[0007] The effective torque=(input shaft torque×η×gear direction signal)+motor torque, where η is a constant between 0 and 1.

[0008] When the torque lag calculation module satisfies the following conditions at the same time, the system starts the self-learning process for the effective torque lag value. During the self-learning process, if the torque lag calculation module does not meet any of the following conditions, the self-learning process stops: Condition 1, the absolute vehicle speed is within the range of 60kph to 100kph, Condition 2, the vehicle speed valid flag in the system is True, Condition 3, the absolute value of the steering angle is less than 30°, Condition 4, the steering angle state valid flag in the system is True, Condition 5, the absolute value of the rotor speed is within the range of 5° / s to 10° / s, Condition 6, the rotor speed direction flag in the system changes.

[0009] The self-learning process includes the following steps: Step 2a, learning the relationship between effective torque and steering angle: when the steering angle increases in the positive direction, the effective torque increases at the same time, when the steering direction is reversed, the effective torque first drops, and then, as the steering angle returns to the positive direction, the effective torque decreases; Step 2b, calculating the effective torque hysteresis value: within a cycle, the steering angle From the initial angle value The final angle And return to the original position, the effective torque when turning is M out , the effective torque after reversing is M back , in this cycle, the effective torque hysteresis value

[0010] If the friction torque confirmation module satisfies the following conditions at the same time, it is judged that the friction torque of this cycle is approximately the effective torque hysteresis value. If any of the following conditions is not met, it is judged that the friction torque of this cycle is the friction torque value of the previous cycle. If this cycle is the first cycle, the friction torque of this cycle is the initial value stored in the system: Condition 1, the steering speed is within the range of 100° / s-200° / s; Condition 2, the vehicle speed is within the range of 60kph~100kph and the absolute value of the steering angle is less than the critical angle.

[0011] The torque compensation calculation module calculates the compensation torque as follows: when the friction compensation mode switching flag is 0, the static friction compensation method is adopted, and the compensation torque is a fixed value determined by the test; when the friction compensation mode switching flag is 1, the dynamic friction compensation method is adopted, and the compensation torque M comp =(1-k)M f , k is a constant between 0 and 1, and k is inversely correlated with the effective torque. If the self-learning is successful in this cycle, M f is the friction torque of this cycle. If the self-learning fails or no self-learning is performed in this cycle, M f Friction torque stored for the last cycle.

[0012] The limiting torque compensation module limits the actual compensated friction torque as follows: when the friction torque does not reach the set friction torque critical value, the friction torque is the set friction torque critical value, and the limit value of the compensation torque is the set friction torque critical value; after the friction torque exceeds the set friction torque critical value, as the friction torque increases, the compensation torque and the compensation torque limit are gradually increased, and the compensation torque M comp ≤M limit =M f , M limit is the compensation torque limit; as the friction torque continues to increase, when it reaches the friction torque critical value set at room temperature, the compensation torque limit no longer increases. At this time, the compensation torque M comp ≤M limit <M f When the ECU temperature is lower than the set temperature critical value, the set friction torque critical value is increased to the increased friction torque critical value, and the compensation torque limit is increased accordingly until the friction torque reaches the increased friction torque critical value.

[0013] The set friction torque critical value is 0.1Nm, the increased friction torque critical value is 0.7Nm, the set friction torque critical value at room temperature is 0.5Nm, and the set temperature critical value is 0°C.

[0014] It also includes step 6, detecting the high friction module and determining whether to output a friction compensation diagnostic signal based on the actual compensated friction torque: if the friction torque calculated in this cycle exceeds the limit value of the system, the friction torque is judged to be abnormal, the friction compensation diagnostic signal is output, and the diagnostic mode alarm is entered; if the friction torque calculated in this cycle does not exceed the limit value of the system, the friction torque is judged to be normal.

[0015] The limit value of the system described is 1 Nm.

[0016] Compared with the prior art, the present invention obtains the mechanical energy loss caused by friction of the system within a certain angle range by identifying the lag of effective torque during steering reversing, and calculates the effective torque lag value of the system, and further obtains the compensation torque required by the system. The limit value of the compensation torque is increased in a low temperature environment, ensuring that the entire steering system can provide normal compensation torque in various environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a functional architecture diagram of the present invention.

[0018] Figure 2 Graph showing the relationship between effective torque and steering angle of the present invention.

[0019] Figure 3 FIG. 4 is a relationship diagram between the friction torque and the friction compensation torque request limit value of the present invention. DETAILED DESCRIPTION

[0020] The present invention will now be further described with reference to the accompanying drawings.

[0021] See also Figure 1 The present invention is a steering gear low temperature friction compensation method, comprising the following steps: Step 1, an effective torque value calculation module calculates and outputs the effective torque according to the input motor torque, input shaft torque and gear direction signal.

[0022] Effective torque = (input shaft torque × η × gear direction signal) + motor torque, η is a constant between 0 and 1. The effective torque is the sum of the torque on the steering input shaft, which is composed of the driver input torque and the motor torque after a certain conversion. The simplified relationship between the effective torque and the steering angle signal is as follows Figure 3 shown.

[0023] Step 2: The torque hysteresis calculation module calculates and outputs the effective torque hysteresis value according to the input vehicle speed, motor speed, steering angle and effective torque.

[0024] When the torque lag calculation module meets the following conditions at the same time, the system starts the self-learning process for the effective torque lag value. During the self-learning process, if the torque lag calculation module does not meet any of the following conditions, the self-learning process stops: Condition 1, the absolute vehicle speed is within the range of 60kph to 100kph, Condition 2, the vehicle speed valid flag in the system is True, Condition 3, the absolute value of the steering angle is less than 30°, Condition 4, the steering angle state valid flag in the system is True, Condition 5, the absolute value of the rotor speed is within the range of 5° / s to 10° / s, Condition 6, the rotor speed direction flag in the system changes.

[0025] The self-learning process includes the following steps: Step 2a, learning the relationship between effective torque and steering angle: when the steering angle increases in the positive direction, the effective torque increases at the same time. When the steering direction is reversed, the effective torque first drops, and then, as the steering angle returns to the positive direction, the effective torque decreases; Step 2b, calculating the effective torque hysteresis value: within one cycle, the steering angle From the initial angle value The final angle And return to the original position, the effective torque when turning is M out , the effective torque after reversing is M back , in this cycle, the effective torque hysteresis value

[0026] Step 3: The friction torque confirmation module determines and outputs the friction torque of this cycle according to the input effective torque hysteresis value.

[0027] Under any driving condition, the torque lag of the system is affected by many factors. In order to minimize the influence of system damping and other system friction forces, the friction torque confirmation module determines that the friction torque of this cycle is approximately the effective torque lag value if the following conditions are met at the same time. If any of the following conditions are not met, the friction torque of this cycle is determined to be the friction torque value of the previous cycle. If this cycle is the first cycle, the friction torque of this cycle is the initial value stored in the system: Condition 1, the steering speed is within the range of 100° / s-200° / s; Condition 2, the vehicle speed is within the range of 60kph~100kph and the absolute value of the steering angle is less than the critical angle.

[0028] The friction torque of this cycle is stored in the system. The friction torque after successful self-learning will be stored in the system until the next successful self-learning, so as to facilitate the subsequent call of the torque compensation calculation module.

[0029] Step 4: The torque compensation calculation module calculates and outputs the compensation torque based on the input friction torque of the current cycle, the friction torque stored in the previous cycle, the friction compensation mode switching flag, and the effective torque.

[0030] The torque compensation calculation module calculates the compensation torque as follows: when the friction compensation mode switching flag is 0, the static friction compensation method is used, and the compensation torque is a fixed value determined by the test. At this time, no other modules are required to participate, and a fixed torque compensation value is directly output; when the friction compensation mode switching flag is 1, the dynamic friction compensation method is used, and the compensation torque M comp =(1-k)M f , k is a constant between 0 and 1, and k is inversely correlated with the effective torque. If the self-learning is successful in this cycle, M f is the friction torque of this cycle. If the self-learning fails or no self-learning is performed in this cycle, M f Friction torque stored for the last cycle.

[0031] Step 5: The torque compensation module limits the actual compensated friction torque according to the input compensation torque, ECU temperature, and friction torque of this cycle.

[0032] The torque compensation module limits the actual compensation friction torque as follows: Figure 3 As shown in the figure, when the friction torque does not reach the set friction torque critical value, the friction torque is the set friction torque critical value, and the limit value of the compensation torque is the set friction torque critical value; after the friction torque exceeds the set friction torque critical value, as the friction torque increases, the compensation torque and the compensation torque limit value are gradually increased, and the compensation torque M comp ≤M limit =M f , M limit is the compensation torque limit; as the friction torque continues to increase, when it reaches the friction torque critical value set at room temperature, the compensation torque limit no longer increases. At this time, the compensation torque M comp ≤M limit <M f When the ECU temperature is lower than the set temperature critical value, the set friction torque critical value is increased to the increased friction torque critical value, and the compensation torque limit is increased accordingly until the friction torque reaches the increased friction torque critical value, thereby maintaining the driver's normal driving feel in a low temperature environment.

[0033] Preferably, the friction torque critical value is set to 0.1 Nm, the increased friction torque critical value is 0.7 Nm, the friction torque critical value is set to 0.5 Nm at room temperature, and the temperature critical value is set to 0°C.

[0034] Step 6, the high friction detection module determines whether to output a friction compensation diagnostic signal based on the actual compensated friction torque: if the friction torque calculated in this cycle exceeds the system limit value, the friction torque is judged to be abnormal, the friction compensation diagnostic signal is output, and the diagnostic mode alarm is entered; if the friction torque calculated in this cycle does not exceed the system limit value, the friction torque is judged to be normal.

[0035] Preferably, the limit value of the system is 1 Nm.

[0036] Taking into account the differences in the designs of different steering systems, the corresponding relationship between the friction compensation torque and the friction torque can also be adjusted. After adopting the present invention, the relationship between the limit value of the friction compensation torque and the friction torque is as follows: Figure 3 shown.

[0037] The present invention obtains the mechanical energy loss of the system due to friction within a certain angle range by identifying the lag of effective torque during steering reversing, and calculates the effective torque lag value of the system, and further obtains the compensation torque required by the system. The limit value of the compensation torque is increased in a low temperature environment to ensure that the entire steering system can provide normal compensation torque in various environments.

Claims

1. A steering gear low temperature friction compensation method, characterized in that: The method comprises the following steps: step 1, the effective torque value calculation module calculates and outputs the effective torque according to the input motor torque, input shaft torque and gear direction signal; step 2, the torque hysteresis calculation module calculates and outputs the effective torque hysteresis value according to the input vehicle speed, motor speed, steering angle and effective torque; step 3, the friction torque confirmation module judges and outputs the friction torque of this cycle according to the input effective torque hysteresis value; step 4, the torque compensation calculation module calculates and outputs the compensation torque according to the input friction torque of this cycle, the friction torque stored in the previous cycle, the friction compensation mode switching flag and the effective torque; step 5, the torque limiting compensation module limits the actually compensated friction torque according to the input compensation torque, ECU temperature and the friction torque of this cycle.

2. A steering gear low temperature friction compensation method according to claim 1, characterized in that: The effective torque = (input shaft torque × η × gear direction signal) + motor torque, η is a constant between 0 and 1.

3. A steering gear low temperature friction compensation method according to claim 1, characterized in that: When the torque lag calculation module satisfies the following conditions at the same time, the system starts the self-learning process for the effective torque lag value. During the self-learning process, if the torque lag calculation module does not meet any of the following conditions, the self-learning process stops: Condition 1, the absolute vehicle speed is within the range of 60kph~100kph, Condition 2, the vehicle speed valid flag in the system is True, Condition 3, the absolute value of the steering angle is less than 30°, Condition 4, the steering angle state valid flag in the system is True, Condition 5, the absolute value of the rotor speed is within the range of 5° / s~10° / s, Condition 6, the rotor speed direction flag in the system changes.

4. A steering gear low temperature friction compensation method according to claim 3, characterized in that: The self-learning process includes the following steps: Step 2a, learning the relationship between effective torque and steering angle: when the steering angle increases in the positive direction, the effective torque increases at the same time, when the steering direction is reversed, the effective torque first drops, and then, as the steering angle returns to the positive direction, the effective torque decreases; Step 2b, calculating the effective torque hysteresis value: within a cycle, the steering angle From the initial angle value The final angle And return to the original position, the effective torque during steering is , the effective torque after reversing is , in this cycle, the effective torque hysteresis value .

5. The steering gear low temperature friction compensation method according to claim 1, characterized in that: If the friction torque confirmation module satisfies the following conditions at the same time, it is judged that the friction torque of this cycle is approximately the effective torque hysteresis value. If any of the following conditions is not met, it is judged that the friction torque of this cycle is the friction torque value of the previous cycle. If this cycle is the first cycle, the friction torque of this cycle is the initial value stored in the system: Condition 1, the steering speed is within the range of 100° / s-200° / s; Condition 2, the vehicle speed is within the range of 60kph~100kph and the absolute value of the steering angle is less than the critical angle.

6. A steering gear low temperature friction compensation method according to claim 1, characterized in that: The torque compensation calculation module calculates the compensation torque as follows: when the friction compensation mode switching flag is 0, the static friction compensation method is used, and the compensation torque is a fixed value determined by the test; when the friction compensation mode switching flag is 1, the dynamic friction compensation method is used, and the compensation torque is , k is a constant between 0 and 1, and k is inversely correlated with the effective torque. If the self-learning is successful in this cycle, then is the friction torque of this cycle. If the self-learning fails or no self-learning is performed in this cycle, Friction torque stored for the last cycle.

7. The steering gear low temperature friction compensation method according to claim 1, characterized in that: The torque limiting compensation module limits the actual compensated friction torque as follows: when the friction torque does not reach the set friction torque critical value, the friction torque is the set friction torque critical value, and the limit value of the compensation torque is the set friction torque critical value; after the friction torque exceeds the set friction torque critical value, as the friction torque increases, the compensation torque and the compensation torque limit are gradually increased, and the compensation torque , is the compensation torque limit; as the friction torque continues to increase, when it reaches the friction torque critical value set at room temperature, the compensation torque limit will no longer increase. At this time, the compensation torque When the ECU temperature is lower than the set temperature critical value, the set friction torque critical value is increased to the increased friction torque critical value, and the compensation torque limit is increased accordingly until the friction torque reaches the increased friction torque critical value.

8. A steering gear low temperature friction compensation method according to claim 7, characterized in that: The set friction torque critical value is 0.1Nm, the increased friction torque critical value is 0.7Nm, the set friction torque critical value at room temperature is 0.5Nm, and the set temperature critical value is 0°C.

9. A steering gear low temperature friction compensation method according to claim 1, characterized in that: It also includes step 6, detecting the high friction module and determining whether to output a friction compensation diagnostic signal based on the actual compensated friction torque: if the friction torque calculated in this cycle exceeds the limit value of the system, the friction torque is judged to be abnormal, the friction compensation diagnostic signal is output, and the diagnostic mode alarm is entered; if the friction torque calculated in this cycle does not exceed the limit value of the system, the friction torque is judged to be normal.

10. A steering gear low temperature friction compensation method according to claim 9, characterized in that: The limit value of the system described is 1 Nm.

Images