TW201722766A - System for detecting fault of a steering wheel angle sensor and the method thereof - Google Patents

Abstract

A system for detecting fault of a steering wheel angle sensor and the method thereof, the system includes a steering wheel angle sensor, a rotary position angle regulator for motor and a central control unit, the central control unit reads the initial value of the signal from the steering wheel rotation angle of the steering wheel angle sensor, the rotary position angle regulator for motor figures out a steering wheel angle estimated value, so as to compare the error between the actual value of the signal from the steering wheel rotation angle and the steering wheel angle estimated value to determine whether the error value is less than the allowable error value, if the error value is bigger than the allowable error value, the steering wheel angle estimated value will replace the failed signal from the steering wheel rotation angle for subsequently controlling by the central control unit.

Description

System and method for detecting steering wheel angle sensor failure

The invention relates to a vehicle electric power steering system, in particular to detecting whether a steering wheel rotation angle signal is faulty, and providing an alternative signal to reduce the influence of the steering wheel operation feel.

At present, automobile manufacturers often install a steering angle sensor (SAS) on the steering wheel of a car to measure the angle and angular velocity of the steering wheel of the driver. The steering wheel angle sensor is used to obtain information on the steering angle of the driver. Further provide information to the central control unit as a reference for vehicle steering and steering.

The steering angle sensor of the automobile is generally mounted on the steering shaft of the steering column tube. When the driver turns the steering wheel to drive the steering shaft to rotate, the steering wheel angle sensor senses the direction of rotation of the steering shaft and the angle of rotation as electric power. One of the input signals of the Central Control Unit (ECU) in the Electric Power Steering (EPS). The ECU obtains the magnitude and direction of the required assist by reasonable calculation based on the input torque and the vehicle speed signal. The motor sends a control signal, and the motor outputs a corresponding torque according to the control signal, and transmits the torque to the steering tie rod via the speed reduction mechanism and the rack gear to complete the power steering.

After obtaining the information, the central control unit (ECU) of the EPS determines the torque gap between the normal safe driving of the vehicle and the driver's steering intention by the driver. Then, the ECU issues a command to adjust the auxiliary force of the motor, thereby correcting The driver of the car turns to the degree of force required to improve the driving safety of the car.

The EPS must be provided with a steering wheel angle sensor. The steering wheel angle sensor is used to convert the steering wheel angle into a signal that can represent the driver's desired direction of travel. The EPS identifies the driver's operational intent by calculating the steering wheel angle and the rate of change of the corner, but When the steering wheel angle sensor suddenly breaks down, the ESP's central control unit will not be able to determine the steering direction of the driver's operating car and affect the driver's ability to operate the steering wheel.

Please refer to US Patent No. 8849498B2, US20080039996A1, CN100519301C. The main technology is to compare whether the direction of rotation of the motor and the steering angle of the steering wheel are the same. If they are consistent, the steering angle signal is normal. If they are inconsistent, compare the direction of rotation of the motor and the direction of torque of the steering wheel. Whether they are consistent, if they are consistent, go back to the top layer and then re-step the process. If they are inconsistent, determine that the steering wheel steering angle signal is invalid, and share the failure information to other control modules.

The previously disclosed patents can detect whether the steering wheel steering angle signal is normal or invalid, but the detection method is whether the motor rotation direction and the steering wheel steering angle direction are consistent, or whether the motor rotation direction and the steering wheel torque direction are consistent. The direction is used as the judgment direction. However, only the direction is used as the criterion for judgment. Because the number of variables is too large and the accurate judgment cannot be achieved, it is easy to cause the judgment error, and the prior art only discloses how to determine the steering angle angle signal failure. It can replace the steering wheel steering angle signal technology, so when the steering wheel rotation angle signal suddenly fails, the control system can not use the angle signal to lose other functions, and affect the driver's operation of the steering wheel.

And Japanese patent JP2014054890, which mainly uses the three directions of steering wheel steering angle, vehicle yaw rate and lateral acceleration to judge whether the angle sensor is abnormal. If the sensor displays abnormality, at different speeds, the steering wheel torque and angle Whether the signal corresponds to the set reasonable range value, and counts the number of errors. When the number of errors reaches the preset count setting value, it determines that the steering wheel angle signal is invalid.

The previously disclosed patent also discloses whether the detection steering wheel steering angle signal is normal or invalid, but the disadvantage is that it is necessary to increase the sensor (vehicle yaw rate, lateral acceleration), in addition to increasing the cost, and in the general vehicle electric power steering In the system, the information of the sensors such as the yaw and lateral acceleration of the vehicle is usually obtained by external signals. These two signals are actually not available during the running of the vehicle, which makes it impossible to achieve the detection purpose. Explain how to determine the steering wheel steering angle signal failure, there is no technical means to replace the steering wheel steering angle signal, so when the steering wheel rotation angle signal suddenly fails, the control system can not use the angle signal to lose other functions, and affect the driver's steering wheel Operation feel.

Therefore, how to improve the operation of the steering wheel when the steering wheel rotation angle signal fails, the control system cannot use the steering wheel rotation angle signal, and the operation feeling of the driver's steering wheel is the primary research and development object of the present invention.

The invention provides a system for detecting a failure of a steering wheel angle sensor and a method thereof, the main purpose of which is to send a steering wheel angle estimation value as a substitute signal to the central control unit when the steering wheel rotation angle signal fails, thereby avoiding sudden loss. The steering wheel rotates the angle signal to affect the operating feel of the steering wheel.

The present invention provides a system and method for detecting a failure of a steering wheel angle sensor. The second object is to read an initial value of a steering wheel rotation angle signal of a steering wheel angle sensor and calculate a steering wheel angle estimation value by using a motor rotation position resolver.

To achieve the foregoing, the present invention provides a system and method for detecting a failure of a steering wheel angle sensor, which mainly includes: a steering wheel angle sensor, a motor rotation position resolver, and a central control unit, wherein the central control unit reads the The steering wheel angle sensor rotates the initial value of the angle signal, and uses the motor rotation position resolver to calculate a steering wheel angle estimation value, and compares the error value between the actual value of the steering wheel rotation angle signal and the steering wheel angle estimation value. Whether it is less than an allowable error value, if it is greater than the allowable error value, the steering wheel angle estimation value is used instead of the failed steering wheel rotation angle signal as the central control unit for subsequent control use to maintain the driver's operating feel.

In order to enable your review committee to have a better understanding and understanding of the purpose, features and effects of the present invention, please refer to the following for a brief description of the following:

As shown in FIG. 1, the present invention is a system for detecting a failure of a steering wheel angle sensor, the system comprising:

a steering wheel angle sensor 10, coupled to the steering wheel 1 of the vehicle for obtaining a steering wheel rotation angle signal and transmitting to a central control unit 20;

a torque sensor 30, coupled to the steering wheel angle sensor 10, for detecting the relative displacement signal between the input shaft and the shaft output shaft of the steering wheel and transmitted to the central control unit 20;

a vehicle speed sensor 40 for receiving the vehicle speed signal and transmitting to the central control unit 20;

a motor 50 is connected to the tire 2 through the speed reduction mechanism 3 and the vehicle tie rod 4, receives the control current output by the central control unit 20, and provides a smooth steering auxiliary power to the tie rod 4 to drive the tire 2 to turn;

a motor rotational position resolver 60 that outputs a motor rotational position signal to the central control unit 20 for controlling the motor 50;

The central control unit 20 reads an initial value of the steering wheel rotation angle signal, and calculates a steering wheel angle estimation value by using the motor rotation position signal.

In the embodiment of the present invention, the central control unit 20 detects whether the steering wheel rotation angle signal of the steering wheel angle sensor 10 is abnormal. If the steering wheel rotation angle signal is detected as normal, the central control unit 20 reads the steering wheel rotation angle signal. The initial value, and the motor rotation position signal of the motor rotation position resolver 60, calculate the steering wheel angle estimation value;

Therefore, when the steering wheel rotation angle signal is invalid, the steering wheel angle estimation value can be sent to the central control unit 20 as a substitute signal, so that the central control unit 20 can be used as the auxiliary compensation logic calculation to avoid sudden loss of the steering wheel. Rotating the angle signal affects the steering feel of the steering wheel.

Among them, the steering wheel angle estimation value is known by the following calculation formula:

The definition of each parameter of the above calculation formula: Ɵ : signal of motor rotation position resolver, Ɵ _delay : motor rotation position resolver delay signal of one sampling time, Ɵ _init : initial value of motor rotation position resolver, Ɵ _add : motor rotation The amount of change in the position resolver, P : the value of the position resolver in one revolution (360 degrees) (ex:count=3*4095), Sr: line angle ratio, L: screw lead, Gr: pulley deceleration Ratio, r: total reduction ratio, angle_init: initial value of steering wheel angle sensor, angle_est: estimated steering wheel angle;

In the first embodiment of the present invention, as shown in Table 1:

According to Table 1, the motor rotation position signal Ɵ_init is changed to Ɵ (incremental case, indicating that the steering wheel is forward). After two overflows i=2, the calculation formula corresponding to i>0 is substituted to calculate the motor rotation position resolver. The amount of change Ɵ _add.

In addition, in the second embodiment of the present invention, as shown in Table 2:

According to Table 2, the motor rotation position signal Ɵ_init is changed to Ɵ (the decrement case indicates that the steering wheel is reversed). After two overflows i=-2, the calculation formula corresponding to i<0 is substituted, and the motor rotation position solution can be calculated. The amount of change in the corners is Ɵadd.

And, as shown in Table 3, the relationship between the estimated value of the steering wheel angle and the actual value of the steering wheel rotation angle signal is obtained by the above calculation formula;

According to Table 3, the estimated steering wheel angle is 3112, and the actual value of the steering wheel rotation angle signal is 2997. If it is converted into the difference between the angle values of the two, it is only about 5 degrees (3112-2997=115,115* 180/4095=5.054..), it can be seen that the difference between the steering wheel angle estimation value and the actual value of the steering wheel rotation angle signal is very small, so when the steering wheel rotation angle signal fails, it can be estimated by the steering wheel angle. The measured value is sent to the central control unit 20 as a substitute signal, and the central control unit 20 is used as a calculation of the auxiliary compensation logic to avoid affecting the operational feel of the steering wheel due to sudden loss of the steering wheel rotation angle signal.

As shown in FIG. 2 and FIG. 3, the present invention is a method for detecting a failure of a steering wheel angle sensor, and the steps are as follows:

S1: detecting whether the steering angle of the steering wheel is abnormal, if the detection result is abnormal, directly enters the step S7, and if the detection result is normal, the process proceeds to step S2;

S2, reading an initial value of the steering wheel rotation angle signal, and calculating a steering wheel angle estimation value by using a motor rotation position signal;

S3. Comparing whether the error value between the actual value of the steering wheel rotation angle signal and the steering wheel angle estimation value is less than a tolerance value (in the embodiment of the present invention, the tolerance value is preset to be within ±10 degrees. If the value is less than the allowable error value, the process proceeds to step S6. If the value is greater than the allowable error value, the process proceeds to step S4.

S5, using the steering wheel angle estimation value as an alternative signal of the steering wheel rotation angle signal, to avoid affecting the operation feeling of the steering wheel during the driving process because the steering wheel rotation angle signal loses the signal;

S6. The general mode is that determining that the error value between the actual value of the steering wheel rotation angle signal and the steering wheel angle estimation value is less than the tolerance value, and continuing to use the actual value of the steering wheel rotation angle signal;

S7, the steering wheel rotation angle signal is abnormal, indicating that the steering wheel rotation angle signal is abnormal at the initial detection, so when entering this step, the vehicle cannot be started, and the driving process is prevented from being affected by the abnormality of the steering wheel rotation angle signal. Safety.

S5, using the steering wheel angle estimation value as an alternative signal of the steering wheel rotation angle signal, to avoid affecting the operation feeling of the steering wheel during the driving process because the steering wheel rotation angle signal loses the signal;

In other words, the most important technical means of the present invention is to calculate the initial value of the steering wheel angle by using a motor rotation position signal through the initial value of the steering wheel rotation angle signal, and compare the actual value of the steering wheel rotation angle signal with the steering wheel angle estimation. Whether the error value between the two values is less than the preset allowable error value (within ±10 degrees). If it is less than, the steering wheel rotation angle signal is normal. If it is greater than ±10 degrees, otherwise the steering wheel rotation angle is invalid. In one step, the steering wheel angle estimation value is substituted for the failed steering wheel rotation angle signal. In the previously disclosed embodiment, the steering wheel angle estimation value angle_est is calculated in increment (steering wheel forward rotation) or decrement (steering wheel reversal), and is calculated according to Table 3. The difference between the steering wheel angle estimation value and the actual value of the steering wheel rotation angle signal is very small, so the substitute signal using the steering wheel angle estimation value for the steering wheel rotation angle signal is given to the central control unit 20 as an auxiliary compensation. Logical calculations to avoid sudden loss of the steering wheel rotation angle signal Affect the steering feel of the steering wheel.

Thereby, the present invention has the following advantages over the prior art:

1. The original motor rotary position resolver used to monitor the steering wheel angle is a sensor that must be used to control the motor in a general vehicle electric power steering system without additional sensor cost. problem.

2. The difference between the calculated steering wheel angle estimation value and the actual value of the steering wheel rotation angle signal is very small, indicating that the steering wheel angle estimation value of the present invention does have a certain accuracy, so when the steering wheel rotation angle signal is invalid It can be used to replace the steering wheel rotation angle to avoid the possibility of partial loss of function and to maintain the driver's hand as much as possible.

In the above, the above embodiments and drawings are only the preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, that is, the equivalent changes and modifications made by the scope of the present invention. It should be within the scope of the patent of the present invention.

1‧‧‧Steering wheel
2‧‧‧ tires
10‧‧‧Steering wheel angle sensor
20‧‧‧Central Control Unit
30‧‧‧ Torque sensor
40‧‧‧Car speed sensor
50‧‧‧Motor
60‧‧‧Motor rotary position resolver

1 is a schematic structural view of a vehicle electric power steering system of the present invention. 2 is a block diagram of a system for detecting a failure of a steering wheel angle sensor according to the present invention. 3 is a flow chart of a method for detecting a failure of a steering wheel angle sensor according to the present invention.

1‧‧‧Steering wheel

2‧‧‧ tires

10‧‧‧Steering wheel angle sensor

20‧‧‧Central Control Unit

30‧‧‧ Torque sensor

40‧‧‧Car speed sensor

50‧‧‧Motor

60‧‧‧Motor rotary position resolver

Claims (10)

A system for detecting a failure of a steering wheel angle sensor for use in a vehicle electric power steering system, the system for detecting a failure of a steering wheel angle sensor includes: a steering wheel angle sensor for obtaining a steering wheel rotation angle signal and transmitting to a central control unit; a motor for receiving a control current output by the central control unit and providing a smooth steering assisting force to give the tie rod to drive the vehicle to turn; and a motor rotating position resolver for outputting a motor rotational position signal to the central control unit And controlling the motor; wherein the central control unit reads an initial value of the steering wheel rotation angle signal, and uses the motor rotation position signal to calculate a steering wheel angle estimation value, and compares the actual value of the steering wheel rotation angle signal with Whether the error value between the steering wheel angle estimation value is less than a tolerance error value, if greater than, indicating that the steering wheel rotation angle signal is invalid, and the steering wheel angle estimation value is sent to the central control unit as a substitute signal. . The system for detecting a failure of a steering wheel angle sensor according to claim 1, wherein the steering wheel angle estimation value is an initial value of the steering wheel angle sensor plus a variation amount of the motor rotation position resolver. The system for detecting a failure of a steering wheel angle sensor according to claim 2, wherein when the motor rotation position signal is incremented, the amount of change of the motor rotation position resolver is obtained by the following calculation formula: Ɵ_add = [(4095- Ɵ_init)+(i-1)*4095+Ɵ]/r/p Ɵ_add: Motor rotation position resolver change amount Ɵ: motor rotation position resolver signal Ɵ_init : Motor rotation position resolver initial value r : Total reduction ratio P : The value of one rotation (360 degrees) of the motor rotation position resolver. The system for detecting a failure of a steering wheel angle sensor according to claim 2, wherein when the motor rotation position signal is decremented, the amount of change of the motor rotation position resolver is obtained by the following calculation formula: Ɵ_add = [(0- Ɵ_init)+(i+1)*4095+(Ɵ-4095)]/r/p Ɵ_add: The amount of change in the motor rotation position resolver Ɵ: motor rotation position resolver signal Ɵ_init : motor rotation position resolver Initial value r : Total reduction ratio P : The value of one rotation (360 degrees) of the motor rotation position resolver. The system for detecting a failure of a steering wheel angle sensor according to claim 1, wherein the tolerance value is within an optimum value of ±10 degrees. The system for detecting a failure of a steering wheel angle sensor according to claim 1, further comprising a torque sensor and a vehicle speed sensor, wherein the torque sensor is configured to detect a relative displacement signal between the input shaft and the shaft output shaft of the steering wheel and transmit to the a central control unit; the vehicle speed sensor is configured to receive a vehicle speed signal and transmit to the central control unit. A method for detecting a failure of a steering wheel angle sensor, the steps of which are: S1: detecting whether a steering wheel rotation angle signal is abnormal, and if the detection result is normal, proceeding to step S2; S2, reading an initial value of the steering wheel rotation angle signal, and using a motor The rotational position signal calculates a steering wheel angle estimation value; S3, comparing whether the error value between the actual value of the steering wheel rotation angle signal and the steering wheel angle estimation value is less than an allowable error value, if greater than the allowable error value, Then entering the step S4; S4, the angle failure mode, entering the angle failure mode means that the steering wheel rotation angle signal of the steering wheel angle sensor is invalid, and the process proceeds to step S5; and S5, using the steering wheel angle estimation value as the steering wheel rotation angle signal Alternative signal. In the method of detecting the failure of the steering wheel angle sensor according to claim 7, in the step S3, if it is determined that the error value between the actual value of the steering wheel rotation angle signal and the steering wheel angle estimation value is less than the tolerance value, Go to step S6: the general mode, enter the general mode to determine that the error value between the actual value of the steering wheel rotation angle signal and the steering wheel angle estimation value is less than the tolerance value, and continue to use the actual value of the steering wheel rotation angle signal. . The method for detecting the failure of the steering wheel angle sensor according to claim 7, in the step S1, if the steering wheel rotation angle signal is abnormal, the process proceeds to step S7: the steering wheel rotation angle signal is abnormal, indicating that the steering wheel rotation angle signal is An abnormality occurs at the beginning of detection. Therefore, when entering this step, the vehicle is displayed to remind the driver of the abnormality, so as to avoid driving safety due to the abnormal rotation of the steering wheel during the driving process. The method for detecting a failure of a steering wheel angle sensor according to claim 7, wherein the tolerance value is within an optimum value of ±10 degrees.