阅读说明：本技术 一种电动助力转向系统的方向盘角度计算方法 (Method for calculating steering wheel angle of electric power steering system ) 是由 吴光耀 朱庆帅 孙瑞 于 2019-09-03 设计创作，主要内容包括：本发明涉及汽车电动助力转向系统的角度失效计算技术领域,具体的讲是一种电动助力转向系统的方向盘角度计算方法,本发明通过方向盘绝对角度传感器和电机转子位置传感器角度计算得到两个方向盘角度,根据具体的失效模式可以在两者之间进行选择作为最终输出的方向盘角度,当其中某个传感器失效时系统依然能提供正确的方向盘角度信号保证系统正常工作。(The invention relates to the technical field of angle failure calculation of an automobile electric power steering system, in particular to a method for calculating the steering wheel angle of an electric power steering system.)

1. A method for selecting a steering wheel angle of an electric power steering system is characterized in that: the method comprises the following steps:

step 1: judging whether the electric power steering system is powered on for the first time, if so, entering the step 2, otherwise, entering the step 3;

step 2: judging whether the steering wheel absolute angle sensor fails, if so, directly determining that the power-on initialization fails, and directly entering the step 4; otherwise, calculating a steering wheel corner A by using a steering wheel absolute angle sensor, marking the steering wheel corner A as SteeringAngeleA, then entering power-on initialization, and entering step 3;

and step 3: calculating a steering wheel angle B, denoted SteeringAngleB, using a motor rotor position sensor;

and 4, step 4: failure mode determination and steering wheel angle selection are performed.

2. The method of selecting a steering wheel angle of an electric power steering system according to claim 1, characterized in that: the power-on initialization in the step 2 is to initialize the angle of the electronic rotor position sensor, and the specific method is as follows: assigning the value of SteeringAngeleA to SteeringAngeleB to initialize SteeringAngeleB, and recording as SteeringAngeleB, wherein the specific formula is as follows: steeingangleb = steeinganglea.

3. The method of selecting a steering wheel angle of an electric power steering system according to claim 1, characterized in that: the specific calculation of the steering wheel angle a in step 2 is as follows: steeling angle a = angle value measured by the steering wheel absolute angle sensor at the current position-angle value measured by the steering wheel absolute angle sensor when the vehicle is traveling straight.

4. The method of selecting a steering wheel angle of an electric power steering system according to claim 1, characterized in that: the specific calculation method for calculating the steering wheel angle B by using the motor rotor position sensor in the step 3 is as follows: firstly, determining a numerical value of a transmission Ratio between a motor rotor and a steering wheel according to the structure of an electric power-assisted sensor, recording the numerical value as Ratio, then converting the change of the position of the motor rotor into the change of a steering wheel angle according to the determined transmission Ratio, recording the steering wheel angle updated in real time, recording the steering wheel angle as SteeringAngleB', and then calculating the steering wheel angle in real time based on the SteeringAngleB and the change of the steering wheel angle, wherein the numerical value is specifically as follows: steeling angleb = steeling angleb' + Ratio × DeltaRPS × GearSign; where Ratio is the transmission Ratio from the motor rotor to the steering wheel, DeltaRPS is the detected change in motor rotor position, GearSign is the motor mounting position, steeingangleb 'is the steering wheel angle updated in real time, steeingangleb' = steeingangleb 'when the first cycle is performed, and steeingangleb' is the steering wheel angle of the previous cycle when the second and subsequent cycles are performed.

5. The method of selecting a steering wheel angle of an electric power steering system according to claim 1, characterized in that: the specific method for failure mode judgment and steering wheel angle selection in step 4 is as follows:

(1) selecting according to a power-on initialization result, setting the angle of the steering wheel to an invalid value when the power-on initialization result is failed, and entering the next step when the power-on initialization result is successful;

(2) judging whether the motor rotor position sensor fails or not, if not, selecting SteeringAngleB as the output angle of the steering wheel, and if so, entering the next step;

(3) judging whether the steering wheel absolute angle sensor fails, if so, setting the steering wheel angle as an invalid value; otherwise, SteeringAngeleA is selected as the steering wheel output angle.

Technical Field

The invention relates to the technical field of angle failure calculation of an automobile electric power steering system, in particular to a method for calculating the steering wheel angle of the electric power steering system.

Background

In the working process of electric power steering, a steering wheel angle signal is usually used for control such as active return, automatic parking and the like, accuracy, robustness and safety need to be considered, cost factors need to be considered, and most of products only use a steering wheel absolute angle sensor to calculate the angle of a steering wheel at present. When the sensor fails, the angle of the steering wheel is lost, and the normal function of the electric power steering system is seriously influenced. The resulting steering wheel angle accuracy also needs to be improved to achieve more accurate angle control and vehicle trajectory tracking.

Therefore, it is necessary to design a method for calculating the steering wheel angle, which can improve the accuracy of the steering wheel angle signal and the system robustness without increasing the cost.

Disclosure of Invention

The invention breaks through the difficult problems in the prior art and designs the method for calculating the steering wheel angle, which improves the accuracy of the steering wheel angle signal and the system robustness on the basis of not increasing the cost.

In order to achieve the above object, the present invention provides a method for calculating a steering wheel angle of an electric power steering system, comprising: the method comprises the following steps:

step 1: judging whether the electric power steering system is powered on for the first time, if so, entering the step 2, otherwise, entering the step 3;

step 2: judging whether the absolute angle sensor of the steering wheel fails, if so, directly judging that the power-on initialization fails, and directly entering the step 4; otherwise, calculating a steering wheel corner A by using a steering wheel absolute angle sensor, marking the steering wheel corner A as SteeringAngeleA, then entering power-on initialization, and entering step 3;

and step 3: calculating a steering wheel angle B, denoted SteeringAngleB, using a motor rotor position sensor;

and 4, step 4: failure mode determination and steering wheel angle selection are performed.

The power-on initialization in the step 2 is to initialize the angle of the electronic rotor position sensor, and the specific method is as follows: assigning the value of SteeringAngeleA to SteeringAngeleB to initialize SteeringAngeleB, and recording as SteeringAngeleB, wherein the specific formula is as follows: steeingangleb = steeinganglea.

The specific calculation of the steering wheel angle a in step 2 is as follows: steeling angle a = angle value measured by the steering wheel absolute angle sensor at the current position-angle value measured by the steering wheel absolute angle sensor when the vehicle is traveling straight.

The specific calculation method for calculating the steering wheel angle B by using the motor rotor position sensor in the step 3 is as follows: firstly, determining a numerical value of a transmission Ratio between a motor rotor and a steering wheel according to the structure of an electric power-assisted sensor, recording the numerical value as Ratio, then converting the change of the position of the motor rotor into the change of a steering wheel angle according to the determined transmission Ratio, recording the steering wheel angle updated in real time, recording the steering wheel angle as SteeringAngleB', and then calculating the steering wheel angle in real time based on the SteeringAngleB and the change of the steering wheel angle, wherein the numerical value is specifically as follows: steeling angleb = steeling angleb' + Ratio × DeltaRPS × GearSign; where Ratio is the transmission Ratio from the motor rotor to the steering wheel, DeltaRPS is the detected change in motor rotor position, GearSign is the motor mounting position, steeingangleb 'is the steering wheel angle updated in real time, steeingangleb' = steeingangleb 'when the first cycle is performed, and steeingangleb' is the steering wheel angle of the previous cycle when the second and subsequent cycles are performed.

The specific method for failure mode judgment and steering wheel angle selection in step 4 is as follows:

(1) selecting according to a power-on initialization result, setting the angle of the steering wheel to an invalid value when the power-on initialization result is failed, and entering the next step when the power-on initialization result is successful;

(2) judging whether the motor rotor position sensor fails or not, if not, selecting SteeringAngleB as the output angle of the steering wheel, and if so, entering the next step;

(3) judging whether the steering wheel absolute angle sensor fails, if so, setting the steering wheel angle as an invalid value; otherwise, SteeringAngeleA is selected as the steering wheel output angle.

Failure in the present invention means: the numerical value of the sensor in normal work does not display, displays the failure state of Error and the like.

Compared with the prior art, the two steering wheel angles are obtained through the angle calculation of the steering wheel absolute angle sensor and the motor rotor position sensor, the steering wheel angle can be selected as the final output steering wheel angle according to the specific failure mode, and when one sensor fails, the system can still provide correct steering wheel angle signals to ensure the normal work of the system.

Drawings

Fig. 1 is a schematic view of the working process of the present invention.

Detailed Description

The invention is further described with reference to the accompanying drawings.

Referring to fig. 1, the present invention relates to a method for calculating a steering wheel angle of an electric power steering system, which is characterized in that: the method comprises the following steps:

step 1: judging whether the electric power steering system is powered on for the first time, if so, entering the step 2, otherwise, entering the step 3;

step 2: judging whether the steering wheel absolute angle sensor fails, if so, setting a flag bit to represent that power-on initialization fails, and directly entering step 4; otherwise, calculating a steering wheel corner A by using a steering wheel absolute angle sensor, marking the steering wheel corner A as SteeringAngeleA, then entering power-on initialization, and entering step 3;

and step 3: calculating a steering wheel angle B, denoted SteeringAngleB, using a motor rotor position sensor;

and 4, step 4: failure mode determination and steering wheel angle selection are performed.

The power-on initialization in the step 2 is to initialize the angle of the electronic rotor position sensor, and the specific method is as follows: assigning the value of SteeringAngeleA to SteeringAngeleB to initialize SteeringAngeleB, and recording as SteeringAngeleB, wherein the specific formula is as follows: steeingangleb = steeinganglea.

The specific calculation of the steering wheel angle a in step 2 is as follows: steeling angle a = angle value measured by the steering wheel absolute angle sensor at the current position-angle value measured by the steering wheel absolute angle sensor when the vehicle is traveling straight.

The specific calculation method for calculating the steering wheel angle B by using the motor rotor position sensor in the step 3 is as follows: firstly, determining a numerical value of a transmission Ratio between a motor rotor and a steering wheel according to the structure of an electric power-assisted sensor, recording the numerical value as Ratio, then converting the change of the position of the motor rotor into the change of a steering wheel angle according to the determined transmission Ratio, recording the steering wheel angle updated in real time, recording the steering wheel angle as SteeringAngleB', and then calculating the steering wheel angle in real time based on the SteeringAngleB and the change of the steering wheel angle, wherein the numerical value is specifically as follows: steeling angleb = steeling angleb' + Ratio × DeltaRPS × GearSign; where Ratio is the transmission Ratio from the motor rotor to the steering wheel, DeltaRPS is the detected change in motor rotor position, GearSign is the motor mounting position, steeingangleb 'is the steering wheel angle updated in real time, steeingangleb' = steeingangleb 'when the first cycle is performed, and steeingangleb' is the steering wheel angle of the previous cycle when the second and subsequent cycles are performed.

The specific method for failure mode judgment and steering wheel angle selection in step 4 is as follows:

(1) selecting according to a power-on initialization result, setting the angle of the steering wheel to an invalid value when the power-on initialization result is failed, and entering the next step when the power-on initialization result is successful;

(2) judging whether the motor rotor position sensor fails or not, if not, selecting SteeringAngleB as the output angle of the steering wheel, and if so, entering the next step;

(3) judging whether the steering wheel absolute angle sensor fails, if so, setting the steering wheel angle as an invalid value; otherwise, SteeringAngeleA is selected as the steering wheel output angle.

Example 1:

when the electric power steering system is powered on for the first time, firstly, a steering wheel corner A is calculated by using a steering wheel absolute angle sensor, and the specific calculation method comprises the following steps: the angle of the steering wheel absolute angle sensor when the vehicle is traveling straight is subtracted from the angle indicated by the steering wheel absolute angle sensor at the current position, and the result is recorded as SteeringAngeleA.

Then, carrying out power-on initialization, namely, initializing a motor rotor position sensor, wherein the specific method comprises the following steps: and assigning the SteeringAngeleA value to the motor rotor position sensor, and recording the angle of the assigned motor rotor position sensor as SteeringAngeleB.

After the initialization is successful, the motor rotor position sensor is used for calculating the steering wheel angle B:

a first period: using SteeringAngleB directly as the angle B of the motor rotor position sensor;

starting from the second period, the angle B of the motor rotor position sensor needs to be updated and calculated in real time, and firstly:

(1) confirming the transmission Ratio from the motor rotor to a steering wheel, and recording the transmission Ratio as Ratio;

(2) determining the installation position of the motor, and recording the installation position as Gearsign which is +/-1 under the general condition;

(3) and recording the detected position change of the motor rotor in real time, recording the position change as DeltaRPS, and performing table recording on the position change to prevent errors and omissions.

The calculation is then performed using the formula SteeringAngleB = SteeringAngleB '+ Ratio x DeltaRPS x GearSign, where SteeringAngleB' is the SteeringAngleB calculated in the previous cycle.

Examples are: in calculating SteeringAngleB for the second cycle, SteeringAngleB '= SteeringAngleB for the first cycle, and SteeringAngleB' = SteeringAngleB for the second cycle when SteeringAngleB for the third cycle is calculated.

Two angle values, namely SteeringAngleA calculated by a steering wheel absolute angle sensor and SteeringAngleB calculated by a motor rotor position sensor in real time can be obtained according to the calculation.

And then, entering a failure mode for judgment:

(1) when the angle signal value transmitted by the motor rotor position sensor is an invalid value, judging that the motor rotor position sensor fails, then judging that the steering wheel absolute angle sensor also fails, and when the angle signal value transmitted by the steering wheel absolute angle sensor is also an invalid value, judging that the steering wheel absolute angle sensor also fails, and setting the steering wheel angle as an invalid value;

(2) when the angle signal value transmitted by the motor rotor position sensor is an invalid value, judging that the motor rotor position sensor is invalid, then judging that the steering wheel absolute angle sensor is valid, and setting the angle of the steering wheel to SteeringAngleA calculated by the steering wheel absolute angle sensor when the angle signal value transmitted by the steering wheel absolute angle sensor is a normal value;

(3) when the angle signal value transmitted by the motor rotor position sensor is a normal value, the motor rotor position sensor is judged to be effective, the state of the steering wheel absolute angle sensor is not judged at the moment, and the steering wheel angle is directly set to SteeringAngleB obtained through real-time updating calculation of the motor rotor position sensor.

Example 2:

when the electric power steering system is not powered on for the first time, the angle B of the motor rotor position sensor is directly updated and calculated in real time, the specific calculation method is the same as that in embodiment 1, and then failure mode judgment and steering wheel angle selection are carried out.

In the failure mode judgment and the steering wheel angle selection, when judging whether the angle initialization of the motor rotor position sensor is successful or not, the angle initialization result of the motor rotor position sensor performed during the first power-on is used as a judgment standard, the successful initialization during the first power-on is the successful angle initialization of the motor rotor position sensor, and the failed initialization during the first power-on is the unsuccessful angle initialization of the motor rotor position sensor.

The failure mode judgment and the steering wheel angle selection performed thereafter are the same as those in embodiment 1.

Under normal conditions and when a steering wheel position sensor fails, the steering wheel angle B is used for both the active centering and the automatic parking functions in the electric power steering. When the motor rotor position sensor fails, the steering wheel angle a is used as an alternative.