Steering wheel angle calculation method based on tas angle sensor

Abstract

This invention discloses a method for calculating steering wheel angle based on a TAS angle sensor, comprising the following steps: Step 1, the signal processing state machine module inside the angle calculation module verifies the validity of each input signal and simultaneously calculates whether the rack is in a stationary state; Step 2: learn the rack end angle; Step 3: calibrate the steering wheel center angle; Step 4: initialize the power steering motor rotor angle and calculate the real-time steering wheel angle and rack position; Step 5: correct the steering wheel angle to obtain the corrected steering wheel angle value. This invention can improve the accuracy of the steering wheel return position, enhance the speed and accuracy of advanced function completion, and improve the driver's driving experience.

Description

Technical Field

[0001] This invention relates to the field of automotive technology, and in particular to a method for calculating steering wheel angle based on a TAS angle sensor. Background Technology

[0002] In automotive steering, the steering wheel angle directly reflects the position of the entire steering gear and is a crucial input signal for basic steering functions such as active return to center and damping. It is also a vital signal for advanced functions like automatic parking and lane keeping. Furthermore, the steering wheel angle is extremely important for the overall performance of the vehicle; for example, the vehicle's longitudinal control module needs to work seamlessly with the steering function to achieve its intended purpose. Therefore, ensuring the accuracy of the steering wheel center angle calculation is essential.

[0003] Currently, the main angle sensors used in steering gears are TOS, TIS, and TAS sensors. TOS, an external sensor, directly measures the steering wheel angle and sends the data to the steering gear via bus to calculate the rack position for steering. It is a simple and inexpensive angle sensor, but its functional safety level is relatively low. TIS sensors are angle sensors that provide periodic high and low level signals from the steering wheel torsion bar. However, when the vehicle's KL30 power is severely depleted, it loses angle-related information and needs to be re-initialized and relearned to obtain the steering wheel angle after power is restored. TAS sensors are built-in angle sensors that provide absolute angles. Their biggest advantage is that even when the KL30 is powered down, the absolute angle is not lost, thus ensuring the accuracy of the steering wheel angle. Therefore, compared to TIS and TOS sensors, TAS sensors have higher functional safety, more stable and reliable angle calculation, and do not lose angles. However, mechanical wear during vehicle operation can cause temporary or permanent changes in the vehicle's zero position, affecting the steering wheel's return-to-center position. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a method for calculating steering wheel angle based on a TAS angle sensor, comprising the following steps:

[0005] Step 1: The internal signal processing state machine module of the angle calculation module verifies the validity of each input signal.

[0006] Simultaneously calculate whether the rack is stationary;

[0007] Step 2: Learn the rack end angle;

[0008] Step 3: Calibrate the steering wheel center angle;

[0009] Step 4: Initialize the rotor angle of the power steering motor, and calculate the real-time steering wheel angle and rack position;

[0010] Step 5: Correct the steering wheel angle to obtain the corrected steering wheel angle value.

[0011] Preferably, the manual learning method for the rack end angle in step 2 is as follows: Step 21, turn the steering wheel to the left to its limit position, and after satisfying that the hand torque is greater than a preset value, the motor torque is greater than a preset value, and the power assist motor speed is less than a preset value and maintained for a preset time, the learning of the left rack end angle is completed; Step 22, turn the steering wheel to the right to its limit position, and after satisfying that the hand torque is greater than a preset value, the motor torque is greater than a preset value, and the power assist motor speed is less than a preset value and maintained for a preset time, the learning of the right rack end angle is completed; Step 23, the internal signal processing state machine module determines whether the total rack travel after learning the left and right rack end angles meets the threshold of minimum travel learning. When the total rack travel is not less than a preset value, the learning is completed and recorded. When the total rack travel is less than a preset value, steps 21 and 22 are re-executed.

[0012] Preferably, the preset values ​​and holding time of the hand torque, motor torque, and assist motor speed are obtained from the vehicle debugging results.

[0013] Preferably, in step 3, the method for calibrating the steering wheel center angle is as follows: calculate the rack travel position and EPS assembly state based on the angle values ​​of the left and right rack ends, and calculate the rack center angle value accordingly. When the steering wheel is centered and the rack is in a stationary state, compare the steering wheel center angle with the rack center angle. When the absolute value of the angle difference is less than or equal to a preset value, determine that the steering wheel center angle calibration is successful and output a calibration completion signal.

[0014] Preferably, the method for determining the assembly state of EPS is to first compare the left and right stroke positions of the pinion, thereby calculating the pinion stroke, and then compare the mechanical center of the pinion stroke with the actual center value, thereby determining which mode the EPS assembly state is in.

[0015] Preferably, the calculation method for the rack travel position is as follows: based on the EPS assembly state mode and actual center position, first calculate the leftward rotation stroke of the pinion, then subtract it from the pinion travel to obtain the rightward rotation stroke of the pinion; after obtaining the left and right rotation strokes of the pinion, convert them into the rack travel position according to the mechanical parameters.

[0016] Preferably, in step 4, the initialization of the rotor angle of the assist motor is to convert the absolute value of the pinion rotation into the rotor angle of the assist motor based on the mechanical structure parameters.

[0017] Preferably, the real-time steering wheel angle and rack position in step 4 are calculated by converting the rotor angle of the power assist motor.

[0018] Preferably, step 4 includes verifying whether the change in the rotor angle of the boost motor is consistent with the change in the TAS angle.

[0019] Preferably, in step 5, when the car is driving straight, the correction function is activated to correct the steering wheel angle. The short-term correction value and the long-term correction value of the steering wheel angle are calculated respectively. The correction value is subtracted from the steering wheel angle value output in step 4 to obtain the corrected steering wheel angle value.

[0020] Preferably, the method for determining whether the vehicle is traveling straight is that the steering wheel speed and torsion bar torque are less than preset values, and the vehicle speed is greater than preset values.

[0021] Compared with existing technologies, this invention can improve the accuracy of steering wheel return position, enhance the speed and accuracy of advanced function completion, and improve the driver's driving experience. Attached Figure Description

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0023] Figure 1 This is a schematic diagram illustrating the steps of the steering wheel angle calculation method based on the TAS angle sensor of the present invention;

[0024] Figure 2 This is a schematic diagram showing the four modes of EPS assembly status. Detailed Implementation

[0025] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can fully understand other advantages and technical effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments, and the details in this specification can also be applied based on different viewpoints, with various modifications or changes made without departing from the overall design concept of the invention. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. The following exemplary embodiments of the present invention can be implemented in many different forms and should not be construed as being limited to the specific embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the technical solutions of these exemplary embodiments to those skilled in the art.

[0026] This specific embodiment provides a method for calculating steering wheel angle based on a TAS angle sensor. The TAS sensor outputs a high-precision absolute angle signal with built-in redundancy verification, ranging from 0-2016°, and automatically overflows and re-accumulates. Therefore, a steering wheel angle calculation module was developed based on this characteristic, establishing a conversion relationship between the power steering motor rotor angle and the TAS absolute angle to calculate the steering wheel angle and rack position.

[0027] like Figure 1 As shown, the specific steps include:

[0028] Step 1: The internal signal processing state machine module of the angle calculation module checks the validity of each input signal and calculates whether the rack is in a stationary state (i.e., Low Dynamic state).

[0029] Step 2: Learn the rack end angle;

[0030] In step 2, when the EPS sample is in an uncalibrated state, a manual learning process for the rack end angle is required: turn the steering wheel to the left to the end position and apply hand force and motor torque. When the learning conditions are met, the rack end angle calculation module will record the TAS angle value of the left end and store it in the NVM block; the learning process for the right end is similar.

[0031] Step 3: Calibrate the steering wheel center angle;

[0032] In step 3, the rack center angle calculation module calculates the rack travel position and EPS assembly status based on the angle values ​​of the left and right rack ends, and then calculates the rack center angle value. At this time, the steering wheel is centered and the Low Dynamic condition is met. When the steering wheel center angle is basically consistent with the rack center angle (the deviation is less than the allowable calibration threshold), the diagnostic median calibration service can be performed. The internal signal processing state machine module records the calibrated steering wheel center angle and stores it in the NVM block. At the same time, the internal state machine also externally represents that the sample is in the calibration state.

[0033] Step 4: Initialize the rotor angle of the power steering motor, and calculate the real-time steering wheel angle and rack position;

[0034] In step 4, when the system is calibrated, the steering wheel angle calculation module establishes the relationship between the external sensor TAS angle and the power steering motor rotor RPS angle. This allows for real-time calculation of the rack position and pinion angle based on changes in the RPS angle, thereby calculating the corresponding RPS angular velocity and rack speed. Simultaneously, the steering wheel angle safety verification module checks whether the changes in the power steering motor rotor angle and the TAS angle are consistent, improving the software's calculation reliability.

[0035] Step 5: Correct the steering wheel angle to obtain the corrected steering wheel angle value.

[0036] In step 5, the steering wheel angle correction module first determines whether the straight-line driving and correction functions are activated based on the EPS vehicle speed, hand torque signal, and steering wheel speed signal. Once the correction learning conditions are met, it calculates the short-term and long-term correction values ​​for the steering wheel angle. The correction values ​​are then subtracted from the steering wheel angle value output by the angle calculation module in step 4 to obtain the corrected steering wheel angle value. The long-term corrected angle value is then stored in the NVM block.

[0037] Furthermore, the manual learning method for the rack end angle in step 2 is as follows:

[0038] Step 21: Turn the steering wheel to the left to its limit position. After the hand torque is greater than the preset value, the motor torque is greater than the preset value, and the power assist motor speed is less than the preset value and is maintained for a preset time, the learning of the left rack end angle is completed.

[0039] Step 22: Turn the steering wheel to the right to its limit position. After the hand torque is greater than the preset value, the motor torque is greater than the preset value, and the power assist motor speed is less than the preset value and is maintained for a preset time, the learning of the right rack end angle is completed.

[0040] Step 23: The internal signal processing state machine module determines whether the total rack travel after learning the end angles of the left and right racks meets the threshold of minimum travel learning. If the total rack travel is not less than the preset value, the learning is completed and recorded. If the total rack travel is less than the preset value, steps 21 and 22 are re-executed.

[0041] The preset values ​​and holding times for hand torque, motor torque, and assist motor speed are derived from the vehicle debugging results. The algorithm provides an interface for modification, allowing debugging engineers to adjust the values ​​based on the vehicle's performance to achieve the best vehicle debugging results.

[0042] Furthermore, the method for calibrating the steering wheel center angle in step 3 is as follows:

[0043] The steering wheel angle calculation module compares the steering wheel center angle with the rack center angle. When the absolute value of the angle difference is less than or equal to a preset value, the steering wheel angle calculation module determines that the steering wheel center angle calibration is successful and outputs a calibration completion signal. At this time, a calibration completion command signal is input. After receiving this signal, the state machine module records the TAS sensor value at this moment, i.e., the actual median value, and outputs it. The above preset value is a modifiable value that can be modified during vehicle debugging to achieve optimal results.

[0044] Further, in step 3, the method for judging the EPS assembly state is to first compare the left and right stroke positions of the pinion gear, calculate the stroke of the pinion gear therefrom, and then compare the mechanical center of the pinion gear stroke with the actual median value, thereby judging which mode the EPS assembly state is in. According to the characteristics of the TAS sensor and the difference in the pinion gear stroke length, 4 working modes are given, specifically as Figure 2 shown, in Figure 2 : A is the left limit position of the pinion gear stroke; B is the right limit position of the pinion gear stroke; C is the mechanical center of the pinion gear stroke; L is the pinion gear stroke;

[0045] According to different working modes, different algorithms can be selected to calculate the mechanical center position of the pinion gear. The specific algorithms are as follows:

[0046] In mode 1, the left and right limit positions are divided by the same range angle of the TAS sensor, that is, A > B, and we can get

[0047] L = A - B;

[0048] In mode 2, the left and right limit positions are not within the same range angle of the TAS sensor, and the mechanical center of the pinion gear is at the critical value, that is, A < B, and we can get C = 0°, L = A + 2016 - B;

[0049] In mode 3, the left and right limit positions are not within the same range angle of the TAS sensor, and the mechanical center of the pinion gear is within the previous range, that is, C < A < B, and we can get L = A + 2016 - B,

[0050] In mode 4, the left and right limit positions are not within the same range angle of the TAS sensor, and the mechanical center of the pinion gear is within the latter range, that is, A < B < C, and we can get L = A + 2016 - B,

[0051] Further, in step 3, the method for calculating the rack stroke position is to first calculate the left rotation stroke of the pinion gear according to the mode of the EPS assembly state and the actual center position, and then subtract it from the pinion gear stroke to obtain the right rotation stroke of the pinion gear. After obtaining the left and right rotation strokes of the pinion gear, it is converted into the rack stroke position according to the mechanical parameters. The conversion method is as follows:

[0052] L RP = W TAS * K scaling * K M2Rratio / (K R2Sratio * 360)

[0053] where

[0054] L RP is the rack stroke position;

[0055] W TAS The output value of the TAS sensor;

[0056] K M2Rratio This refers to the transmission ratio from the rotor of the power assist motor to the rack;

[0057] K scaling For conversion factors of TAS sensor signal values;

[0058] K R2Sratio This refers to the transmission ratio from the rotor of the power assist motor to the torsion bar;

[0059] Furthermore, in step 4, the initialization of the assist motor rotor angle involves converting the absolute value of the pinion rotation into the assist motor rotor angle based on the mechanical structure parameters. The calculation method is as follows:

[0060] W RA =(W TAS -W AC )*K scaling *K GearSign / K R2Sratio

[0061] in:

[0062] W RA To assist in adjusting the rotor angle of the motor;

[0063] W TAS The output value of the TAS sensor;

[0064] W AC This refers to the actual center angle of the steering wheel.

[0065] K scaling For conversion factors of TAS sensor signal values;

[0066] K GearSign This is the coefficient relating the steering wheel rotation direction to the rack movement direction;

[0067] K R2Sratio This refers to the transmission ratio from the rotor of the power assist motor to the torsion bar;

[0068] The calculation method for the steering angle of the power steering motor after initialization is as follows:

[0069] W RA =W LastRA +ΔW RA

[0070] in:

[0071] W RA To assist in adjusting the rotor angle of the motor;

[0072] W LastRAThe rotor angle of the boost motor at the time of the previous call;

[0073] ΔW RA The value representing the change in rotor angle derived from the rotor's rotational speed;

[0074] Furthermore, the real-time steering wheel angle and rack position in step 4 are calculated by converting the rotor angle of the power steering motor, and the conversion formulas are as follows:

[0075] W SA =W RA *K R2Sratio *K GearSign / K scaling

[0076] L RP =W RA *K GearSign *K M2Rratio / 360

[0077] in

[0078] W SA Steering wheel angle;

[0079] L RP This indicates the rack position;

[0080] W RA To assist in adjusting the rotor angle of the motor;

[0081] K M2Rratio This refers to the transmission ratio from the rotor of the power assist motor to the rack;

[0082] K scaling For conversion factors of TAS sensor signal values;

[0083] K R2Sratio This refers to the transmission ratio from the rotor of the power assist motor to the torsion bar;

[0084] K GearSign This is the coefficient relating the steering wheel rotation direction to the rack movement direction;

[0085] Furthermore, the steering wheel angle correction module can be selectively activated when the vehicle is driving straight. The method for determining whether the vehicle is driving straight in step 5 is that the steering wheel speed and torsion bar torque are less than preset values, and the vehicle speed is greater than preset values.

[0086] The above preset values ​​are modifiable and can be modified during vehicle debugging to achieve the best results.

[0087] Furthermore, in step 5, once the EPS status signal, steering wheel speed signal, vehicle speed and torque signal, and whether the correction mode signal meet the conditions, the mode selection signal determines whether to use a long-term or short-term correction algorithm.

[0088] The beneficial effects achieved by this invention are as follows:

[0089] This invention designs a steering wheel angle calculation module based on the characteristics of TAS sensors, including the calculation of parameters such as the rotor angle of the power steering motor, and the position and stroke of the rack. The calculation is completed based on the pinion angle and mechanical parameter characteristics.

[0090] Based on the characteristics of TAS sensors and EPS mechanical characteristics, this invention designs four working modes, covering all working conditions that may be encountered in a real vehicle. The corresponding algorithm can be automatically selected according to the working mode to improve efficiency and accuracy. A calibration process is designed, and corresponding control algorithms are designed according to the failure situations that may be encountered during calibration.

[0091] Considering the mechanical wear and tear caused during vehicle operation, which can lead to temporary or permanent changes in the vehicle's zero position, a steering wheel angle correction module was designed. During straight-line driving, the algorithm analyzes the steering wheel angle correction value over a period of time to obtain the new steering angle zero position, thereby improving the accuracy of the steering wheel return position, enhancing the speed and accuracy of advanced functions, and improving the driver's driving experience.

[0092] The present invention has been described in detail above through specific embodiments and examples, but these are not intended to limit the invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A method for calculating steering wheel angle based on a TAS angle sensor, characterized in that, Includes the following steps: Step 1: The internal signal processing state machine module of the angle calculation module checks the validity of each input signal and calculates whether the rack is in a stationary state. Step 2: Learn the rack end angle; Step 3: Calibrate the steering wheel center angle; Step 4: Initialize the rotor angle of the power steering motor, and calculate the real-time steering wheel angle and rack position; Step 5: Adjust the steering wheel angle to obtain the adjusted steering wheel angle value; The manual learning method for the rack end angle in step 2 is as follows: Step 21: Turn the steering wheel to the left to its limit position. After the hand torque is greater than the preset value, the motor torque is greater than the preset value, and the power assist motor speed is less than the preset value and is maintained for a preset time, the learning of the left rack end angle is completed. Step 22: Turn the steering wheel to the right to its limit position. After the hand torque is greater than the preset value, the motor torque is greater than the preset value, and the power assist motor speed is less than the preset value and is maintained for a preset time, the learning of the right rack end angle is completed. Step 23: The internal signal processing state machine module determines whether the total rack travel after learning the end angles of the left and right racks meets the threshold of minimum travel learning. If the total rack travel is not less than the preset value, the learning is completed and recorded. If the total rack travel is less than the preset value, steps 21 and 22 are re-executed.

2. The method for calculating steering wheel angle based on a TAS angle sensor according to claim 1, characterized in that, The preset values ​​and holding time of the hand torque, motor torque, and booster motor speed are derived from the vehicle debugging results.

3. The method for calculating steering wheel angle based on a TAS angle sensor according to claim 1, characterized in that, In step 3, the method for calibrating the steering wheel center angle is as follows: calculate the rack travel position based on the angle values ​​of the left and right rack ends, the EPS assembly state, and calculate the rack center angle value accordingly. When the steering wheel is centered and the rack is stationary, compare the steering wheel center angle with the rack center angle. When the absolute value of the angle difference is less than or equal to the preset value, it is determined that the steering wheel center angle calibration is successful, and a calibration completion signal is output.

4. The method for calculating steering wheel angle based on a TAS angle sensor according to claim 3, characterized in that, The method for determining the assembly status of EPS is to first compare the left and right travel positions of the pinion, thereby calculating the pinion travel, and then compare the mechanical center of the pinion travel with the actual center value, thereby determining which mode the EPS assembly status is in.

5. The method for calculating steering wheel angle based on a TAS angle sensor according to claim 4, characterized in that, The calculation method for rack travel position is as follows: based on the EPS assembly mode and actual center position, first calculate the leftward rotation stroke of the pinion, then subtract it from the pinion travel stroke to obtain the rightward rotation stroke of the pinion; after obtaining the left and right rotation strokes of the pinion, convert them into rack travel position according to mechanical parameters.

6. The method for calculating steering wheel angle based on a TAS angle sensor according to claim 1, characterized in that, In step 4, the initialization of the rotor angle of the booster motor involves converting the absolute value of the pinion rotation into the rotor angle of the booster motor based on the mechanical structure parameters.

7. The method for calculating steering wheel angle based on a TAS angle sensor according to claim 1, characterized in that, In step 4, the real-time steering wheel angle and rack position are calculated by converting the rotor angle of the power assist motor.

8. The method for calculating steering wheel angle based on a TAS angle sensor according to claim 1, characterized in that, Step 4 includes verifying whether the change in the rotor angle of the boost motor is consistent with the change in the TAS angle.

9. The method for calculating steering wheel angle based on a TAS angle sensor according to claim 1, characterized in that, In step 5, when the car is driving straight, the correction function is activated to correct the steering wheel angle. The short-term correction value and the long-term correction value of the steering wheel angle are calculated respectively. The correction value is subtracted from the steering wheel angle value output in step 4 to obtain the corrected steering wheel angle value.

10. The method for calculating steering wheel angle based on a TAS angle sensor according to claim 9, characterized in that, The method to determine whether a car is traveling straight is to check if the steering wheel speed and torsion bar torque are less than preset values, and the vehicle speed is greater than preset values.

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