KR20140086069A - Method for controlling limp mode of torque sensor and electric power steer apparatus using the same - Google Patents

Abstract

The present invention relates to a method for controlling a limp mode during a failure of a torque sensor and an electric steering system using the same, which can assist safe driving of a vehicle by maintaining the control at a predetermined ratio of output to a normal output using remaining torque sensors and lateral acceleration (later G) information during a failure of a torque sensor. The electric steering system includes a steering torque sensor which detects relative rotational displacement of an input shaft and an output shaft according to the rotation of a steering wheel of a vehicle, and includes first and second torque sensors; a lateral acceleration sensor which detects the lateral acceleration of the vehicle; and an electronic control unit which recognizes a failure of the first torque sensor and controls a limp mode of the steering system of the vehicle based on a signal from the second torque sensor and a signal from the lateral acceleration sensor.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a control method of a limp mode when a torque sensor fails, and an electric steering system using the same.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a control method for a limp mode when a torque sensor fails and an electric steering system using the same. More particularly, The present invention relates to a method of controlling a limp mode when a torque sensor fails and a motor-driven steering device using the same.

The existing hydraulic steering system generates hydraulic pressure from a hydraulic pump driven by a belt in the engine to assist the steering wheel operation force while the electric steering system reduces the force by which the driver operates the steering wheel by using an electric motor. It is possible to control the steering wheel operating force felt by the driver optimally.

Electric power steering (EPS) is a system in which the EPS controller receives signals from the steering torque sensor, the vehicle speed sensor, and the steering angle sensor for the engine speed, the vehicle speed and the steering angular speed, Thereby improving the steering performance by changing the steering force per speed according to the running speed of the vehicle. An example of a conventional motor-driven steering system is disclosed in Korean Patent Laid-Open Publication No. 10-2012-0060644.

The steering torque sensor is used as a core part in various parts of the electric steering system together with the steering angle sensor and the steering motor. It measures the torque applied to the steering shaft and transmits it to the EPS controller. Such a steering torque sensor includes a contact type resistive sensor, a contact resistance type sensor, a SAW (surface acoustic wave) sensor, and a non-contact type magnetoresistive sensor, a Hall IC sensor, a capacitive sensor, and an optical encoder sensor.

On the other hand, in the electric steering system, when a failure occurs in the steering torque sensor, the steering assist is immediately stopped. In the case where the vehicle is running, sudden change of the steering force causes a situation where the driver's life may be threatened There is a possibility.

Korean Patent Publication No. 10-2012-0060644 (2012.06.12)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of controlling a limp mode when a torque sensor fails to effectively control a limp mode in an emergency program state when a steering torque sensor fails .

Another object of the present invention is to provide a method of controlling a limp mode when a torque sensor fails and a motor-driven steering device using the same, which can maintain a steering force according to a running of the vehicle for a predetermined time through effective limp mode control when the steering torque sensor fails .

According to an aspect of the present invention, there is provided an electric steering system comprising: a steering wheel having a first torque sensor and a second torque sensor, Torque sensor; A lateral acceleration sensor for sensing a lateral acceleration of the vehicle; And an electronic control unit for recognizing the failure of the first torque sensor and for controlling the limp mode of the steering apparatus of the vehicle based on the signal from the second torque sensor and the signal from the lateral acceleration sensor.

In one embodiment, the electronic control unit determines whether the first steering direction calculated based on the signal from the second torque sensor and the second steering direction calculated based on the signal from the lateral acceleration sensor are the same direction or the opposite direction, 2 state of the torque sensor is determined to be normal or abnormal.

In one embodiment, the electronic control unit is characterized by providing a steering force according to a signal from the second torque sensor when the first steering direction and the second steering direction are the same. Here, the steering force is based on reflecting the vehicle speed.

In one embodiment, the electronic control unit is characterized by providing steering force to the steering wheel by controlling the amount of current of the steering motor coupled to the steering wheel to a current amount smaller than the steady state current amount. Here, the small current amount is preferably 30% to 70% of the steady-state amount of current.

In one embodiment, the electronic control unit is characterized by supplying a steering force to the steering wheel by supplying a current amount of the steering motor coupled to the steering wheel for a predetermined time. Here, the predetermined time is preferably from 2 minutes to 3 minutes.

In one embodiment, the electric steering system includes a steering angle sensor that measures the steering angle of the steering wheel and provides a steering angle signal corresponding to the measured steering angle to the electronic control unit; And a vehicle speed sensor that senses the speed of the vehicle and provides a vehicle speed signal corresponding to the sensed vehicle speed to the electronic control unit.

A method of controlling a limp mode at the time of a torque sensor failure according to an aspect of the present invention includes detecting a relative rotational displacement of an input shaft and an output shaft as the steering wheel of the vehicle rotates, A method of controlling a limp mode in a torque sensor failure in an electric steering system including a sensor, a lateral acceleration sensor for detecting a lateral acceleration of the vehicle, and an electronic control unit connected to a steering torque sensor and a lateral acceleration sensor, Recognizing a failure of the device; Entering a preset limp mode according to a failure of the first torque sensor; Recognizing a first steering direction based on a signal of a second torque sensor in accordance with a preset process of the lymph mode; A lateral acceleration signal from a vehicle body posture control device or a driving safety assisting device of a vehicle to which a lateral acceleration sensor or a lateral acceleration sensor for measuring a lateral acceleration of the vehicle is connected and detects a second steering direction based on the received lateral acceleration signal ; Comparing the first steering direction and the second steering direction; Providing a steering force to the steering wheel according to a signal from the second torque sensor if the first steering direction and the second steering direction are the same direction; And stopping the steering assist if the first steering direction and the second steering direction are opposite directions.

In one embodiment, the step of providing the steering force to the steering wheel includes controlling the steering motor coupled to the steering wheel to a current amount smaller than the steady state current amount, for example, about 30% to about 70% of the steady state current amount .

In one embodiment, providing steering force to the steering wheel is characterized by providing steering force to the steering wheel by driving the steering motor coupled to the steering wheel for a period of time, such as about 2 minutes to about 3 minutes, do.

According to the present invention, it is possible to provide a method of controlling a limp mode when a torque sensor fails to effectively operate a limp mode in an emergency program state when a steering torque sensor fails.

In addition, according to the present invention, a torque sensor capable of assisting the driver in a safe manner by maintaining the steering force according to the running of the vehicle at a predetermined level for a predetermined time by controlling the effective limp mode when the steering torque sensor fails, It is possible to provide a limp mode control method and an electric steering system using the same.

1 is a block diagram of an electric steering system according to the present invention;
2 is a functional block diagram of the electronic control unit of Fig.
3 is a flowchart of a method of controlling a limp mode of a torque sensor according to the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor should appropriately define the concept of the term in order to describe its invention in the best way The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It is to be understood that equivalents and modifications are possible.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

Example

1 is a block diagram of an electric steering system according to the present invention.

Referring to FIG. 1, an electric steering apparatus 10 according to the present embodiment includes a sensor 11, an electronic control unit (ECU) 12, and a steering motor 13.

The sensor 11 includes a steering torque sensor 111, a vehicle speed sensor 112, a steering angle sensor 113 and a lateral acceleration sensor 114. In the present invention, it is described that the sensor 11 includes the steering torque sensor 111, the vehicle speed sensor 112, the steering angle sensor 113 and the lateral acceleration sensor 114, The components included in the sensor 11 can be variously modified and modified within the technical spirit of the present invention.

A steering torque sensor (hereinafter briefly referred to as torque sensor) 111 senses the relative rotational displacement of the input shaft and the output shaft as the steering wheel rotates, generates an electrical signal, and transmits the generated electrical signal to the electronic controller 12 . The torque sensor 111 is normally used as a pair to detect a failure of the torque sensor itself.

In the present embodiment, it is assumed that the electrical signals generated by the steering torque sensor 11 are a torque main signal and a torque sub signal for ease of explanation. Here, the torque main signal and the torque sub signal are classified in terms of safety in terms of securing an electrical signal for sensing the relative rotational displacement of the input shaft and the output shaft as the steering wheel rotates.

The vehicle speed sensor 112 senses the speed of the vehicle and transmits an electrical signal proportional to the sensed vehicle speed to the electronic control unit 12. [ An electrical signal proportional to the vehicle speed can be expressed as a vehicle speed signal.

The steering angle sensor 113 measures the rotation angle of the steering wheel rotated by the driver's operation and transmits an electrical signal corresponding to the measured rotation angle to the electronic control unit 12. [ An electrical signal corresponding to the steering angle of the steering wheel can be expressed as a steering angle signal.

The lateral acceleration sensor 114 senses the lateral acceleration (Lateral G) of the vehicle and transmits an electrical signal proportional to the sensed lateral acceleration of the vehicle to the electronic control unit 12. [ An electrical signal proportional to the lateral acceleration of the vehicle can be represented by a lateral acceleration signal.

The electronic control unit 12 receives various signals from the sensor 11 and grasps the traveling state of the vehicle based on the received signals and then controls the driving of the steering motor 13 by controlling the amount of current flowing through the steering motor 13 do.

When one of the torque sensors (for example, the first torque sensor) fails in the steering torque sensor, the electronic control unit 12 determines whether the electric steering apparatus can perform the normal operation with the other torque sensor, Operates to immediately stop the steering assist when the operation can not be performed, and to maintain the steering assist for at least a predetermined time when the normal operation can be performed.

More specifically, when the electronic control unit 12 recognizes the failure of one of the two torque sensors (the first torque sensor), the remaining torque sensor Sensor) and the second steering direction based on the lateral acceleration information (Lateral G) of the electronic stability control (ESC). That is, when the first steering direction and the second steering direction are the same, the electronic control unit 12 performs the steering assist with a predetermined current amount smaller than the steady state current for a predetermined time based on the signal from the second torque sensor .

Here, the predetermined time is preferably about 2 minutes to about 3 minutes, and the predetermined time takes into consideration the alarm for the lymphatic mode and the time required for the driver to cope. It is preferable that the predetermined amount of current is about 30% to about 70% of the amount of the steady-state current. The amount of the predetermined amount of current is intended to prevent the malfunction of the electric power steering apparatus due to the failure of the torque sensor.

The motor 13 generates auxiliary power for smooth steering. The motor 13 generates a predetermined driving force in a predetermined direction according to a control signal or an amount of current supplied from the electronic control unit 12. [

2 is a functional block diagram of the electronic control unit of Fig.

2, the electronic control unit 12 according to the present embodiment includes a torque sensor failure detecting unit 121, a first steering direction calculating unit 122, a second steering direction calculating unit 123, a comparing unit 124, a storage unit 125, and a motor drive signal output unit 126.

The torque sensor failure detection unit 121 recognizes a failure of one of the two torque sensors of the steering torque sensor (first torque sensor). The failure detection of the torque sensor can be performed by comparing the output signals of the first and second torque sensors or by detecting whether the amount of change in the output signal of each torque sensor exceeds a predetermined threshold value. When a failure of the first torque sensor is recognized, the electronic control unit enters a preset limp mode.

The first steering direction calculation section 122 recognizes the first steering direction based on the signal of the second torque sensor in accordance with the preset process of the lymph mode.

The second steering direction calculation section 123 recognizes the second steering direction based on the lateral acceleration signal. The electronic control unit receives a lateral acceleration signal from a lateral acceleration sensor for measuring lateral acceleration of the vehicle through a predetermined input terminal or a vehicle body posture control device or a driving safety assisting device for a vehicle to which the lateral acceleration sensor is connected and outputs the received lateral acceleration signal To the second steering direction calculating section 123.

The comparing unit 124 compares the first steering direction and the second steering direction. The comparator 124 compares the first steering direction and the second steering direction, and then outputs a comparison result signal indicating whether the first steering direction and the second steering direction are the same direction or opposite directions.

The storage unit 125 stores time information for maintaining the steering effort and intensity information of the steering force in the lymph mode. For example, the storage unit 125 may comprise means for operating to maintain the steady-state force for a time of about 2 minutes to about 3 minutes, or a component (such as a timer) that performs a function corresponding to this means. Further, the storage unit 125 may include means for supplying a current amount of about 30% to about 70% of the amount of steady-state current to the steering motor, or a component (such as a battery) Connected switches, etc.).

The motor drive signal output unit 126 outputs a motor drive signal for controlling the steering motor in accordance with the holding time from the storage unit 125 and the coercive force intensity according to the comparison result of the comparison unit 124. For example, if the first steering direction and the second steering direction are in the same direction, the motor drive signal output section 126 outputs the motor torque signal for about 2 minutes 20 seconds and under the condition of about 40% And to provide a steering force according to the signal from the sensor to the steering wheel. Further, if the first steering direction and the second steering direction are opposite to each other, the motor drive signal output section 126 can immediately stop the steering assist, thereby preventing malfunction of the electric steering apparatus due to the torque sensor failure.

3 is a flowchart of a method of controlling a limp mode of a torque sensor according to the present invention.

Referring to FIG. 3, in the method of controlling the torque sensor of the torque sensor according to the present embodiment, first, the control unit of the electric steering system recognizes the failure of one of the at least two torque sensors (the first torque sensor) ).

The failure of the first torque sensor can be determined based on the torque main signal and the torque sub signal. For example, the failure of the first torque sensor is determined by considering that a failure has occurred in the torque main signal when the torque main signal received from the first torque sensor exceeds a predetermined upper limit value or is smaller than a predetermined lower limit value .

Next, when the failure of the first torque sensor is recognized, the mode enters the limp mode (S32).

The entry of the lymph mode may be achieved by, for example, generating a torque average value that is an average of the absolute values of the sum of the torque main signal and the torque sub signal received from the first torque sensor, May be performed when the reference value is exceeded or is smaller than the second reference value.

Next, the control unit recognizes the first steering direction based on the first signal received from the remaining torque sensor (second torque sensor) (S33).

Next, the control unit recognizes the second steering direction using the lateral acceleration information of the electronic stability control (ESC) (S34).

Here, the lateral acceleration can be detected by the lateral acceleration sensor of the vehicle and transmitted to the ESC from the lateral acceleration sensor. ESC is a type of vehicle body posture control device or a driving safety assisting device. When there is a difference between the ABS (Anti-lock Brake System), which is a device for preventing the brake from being locked when the vehicle suddenly brakes, Refers to a device that controls a vehicle by integrating a Traction Control System (TCS), which is a device that prevents idling of a tire and prevents vehicle slippage.

In this step S34, the control unit can recognize the steering direction of the vehicle based on the amount of change in direction and intensity in the lateral acceleration.

Next, the control unit compares the first steering direction and the second steering direction to determine whether the same direction or the opposite direction (S35).

As a result of the determination in step S35, if the steering direction is the same direction, the control unit controls the steering motor at a constant rate of output for a predetermined time based on the information from the second torque sensor (S36).

In this step S36, it is confirmed that the second torque sensor is operating normally based on the lateral acceleration information. Therefore, the control unit can control the motor based on the information from the second torque sensor.

The above-mentioned predetermined time is preferably about 2 minutes to 3 minutes (e.g., 2 minutes and 20 seconds). Approximately two to three minutes is the time for the vehicle operator to take action in response to a failure of the electric steering system (such as moving a moving vehicle to a safe zone).

Further, it is preferable that the above-mentioned output of a certain ratio is about 30% to about 70% of the normal output, and more preferably about 40%. The reason why the steering motor is controlled with a certain ratio of output is that the malfunction due to the failure of the torque sensor can be minimized when supplying the reduction assist current reduced by the predetermined amount of current in the steady state assist current to the steering motor.

On the other hand, if it is determined in step S35 that the direction is the opposite direction, the controller determines that the reliability of the second torque sensor is low and immediately stops the electric steering assistance (S37).

In this step S37, it is determined that the failure of the second torque sensor is not recognized after the failure of the first torque sensor, but it is determined that the information of the second torque sensor is in an unstable state and the malfunction of the electric- To stop the steering assist immediately.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limited to the embodiments set forth herein. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (13)

A steering torque sensor having a first torque sensor and a second torque sensor for detecting a relative rotational displacement of an input shaft and an output shaft as the steering wheel of the vehicle rotates;
A lateral acceleration sensor for sensing a lateral acceleration of the vehicle; And
And an electronic control unit for recognizing a failure of the first torque sensor and controlling a limp mode of the steering apparatus of the vehicle based on a signal from the second torque sensor and a signal from the lateral acceleration sensor, . The method according to claim 1,
The electronic control unit determines whether the first steering direction calculated based on the signal from the second torque sensor and the second steering direction calculated based on the signal from the lateral acceleration sensor are the same direction or the opposite direction, And determines the state of the torque sensor to be normal or abnormal. 3. The method of claim 2,
Wherein the electronic control unit provides the steering wheel with a steering force according to a signal from the second torque sensor when the first steering direction and the second steering direction are the same. The method of claim 3,
Wherein the electronic control unit provides the steering force to the steering wheel by controlling the amount of current of the steering motor coupled to the steering wheel to a current amount smaller than a steady state current amount. 5. The method of claim 4,
And the small current amount is 30% to 70% of the steady-state current amount. The method according to claim 3 or 4,
Wherein the electronic control unit supplies the steering force to the steering wheel by supplying a current amount of the steering motor coupled to the steering wheel for a predetermined time. The method according to claim 6,
And the predetermined time is 2 minutes to 3 minutes. The method according to claim 1,
A steering angle sensor for measuring a rotational angle of the steering wheel and providing a steering angle signal corresponding to the measured rotational angle to the electronic control unit; And
Further comprising a vehicle speed sensor for detecting the speed of the vehicle and for providing a vehicle speed signal corresponding to the sensed vehicle speed to the electronic control unit. A steering torque sensor having a first torque sensor and a second torque sensor for detecting a relative rotational displacement of an input shaft and an output shaft as the steering wheel of the vehicle rotates, a lateral acceleration sensor for sensing a lateral acceleration of the vehicle, A method of controlling a limp mode when a torque sensor fails in an electric steering apparatus including a sensor and an electronic control unit connected to the lateral acceleration sensor,
Recognizing a failure of the first torque sensor;
Entering a preset limp mode according to the failure of the first torque sensor;
Recognizing a first steering direction based on a signal of a second torque sensor according to a preset process of the lymphatic mode;
A lateral acceleration sensor for measuring the lateral acceleration of the vehicle or a lateral acceleration signal from the vehicle body posture control device or the driving safety assisting device of the vehicle to which the lateral acceleration sensor is connected and for receiving a lateral acceleration signal based on the received lateral acceleration signal, Recognizing a direction;
Comparing the first steering direction and the second steering direction;
Providing a steering force to the steering wheel according to a signal from the second torque sensor if the first steering direction and the second steering direction are the same direction; And
And stopping the steering assist if the first steering direction and the second steering direction are opposite to each other. 10. The method of claim 9,
Wherein the step of providing the steering force to the steering wheel comprises controlling the steering motor coupled to the steering wheel to a current amount smaller than a steady state current amount. 11. The method of claim 10,
Wherein the small current amount is 30% to 70% of the steady state current amount. 11. The method according to claim 9 or 10,
Wherein the step of providing the steering force to the steering wheel comprises providing the steering force to the steering wheel by driving the steering motor coupled to the steering wheel for a predetermined period of time. . 13. The method of claim 12,
Wherein the predetermined time is from 2 minutes to 3 minutes.

Images