KR20130107683A - Fail-safe strategy method of motor driven power steering - Google Patents

Abstract

PURPOSE: A fail-safe implementation method is provided to supply an accurate fail-safe determination method while being efficient based on one information selected among various information which owned by a sent protocol. CONSTITUTION: A fail-safe implementation method of an electric motion power steering device includes the following steps. Detection information of a torque sensor is transmitted to ECU through a specific integrated circuit chip [ASIC chip] in an SENT protocol type. A fault diagnose is executed based on one information selected among various information of the SENT protocol in ECU. A fault diagnostic step of a torque sensor includes the following steps. Once the speed of an engine for drive exceeds a certain level, the SENT information of the torque sensor determines whether the status of the torque sensor is invalid. Once a status nibble is determined to be error or invalid, a status invalidity counter of the torque sensor is performed. If the status invalidity counter of the torque sensor is less than a critical value, diagnosis is performed again while a number of counter performances is stored. If the value exceeds a maximum critical value, malfunction of the torque sensor is determined. [Reference numerals] (AA) Diagnose is executed only after starting

Description

Fail-safe strategy method of motor driven power steering

The present invention relates to a fail-safe implementation method of an electric power steering apparatus, and more particularly, to a fail-safe implementation method of an electric power steering apparatus capable of implementing a cent-based torque sensor fail-safe. .

The vehicle's power steering device refers to a device for reducing the angular rotation operation force of the steering wheel, and recently, a motor driven power steering (MDPS) is mounted to change the steering force according to the driving speed.

The electric power steering device is a vehicle speed responsive power steering device. The ECU of the electric power steering module functions to provide an optimum steering feeling to the driver while controlling the steering angle and motor movement according to the vehicle speed.

Such an electric steering apparatus is an apparatus for assisting steering power by the rotational force of a motor, as shown in FIG. 1, which includes a power generating motor 14 for steering, an output shaft of the motor 14, and steering. The rack drive type reduction gear box 12 which connects between the shafts 10, the ECU 16 which controls the drive of a motor by receiving information, such as a vehicle speed sensor and a torque sensor, and steering of a steering wheel by a driver And a torque sensor 18 mounted on the steering wheel to sense the direction.

MDPS, the electric power steering device, is basically a system in which the torque sensor value corresponding to the driver's steering will be input, the motor is controlled by the output of the ECU, and the motor position information is fed back. From the point of view of this system, the stability of the torque sensor corresponding to the input (sensor value acquisition and transmission to the ECU) plays an essential role in steering stability and overall performance.

However, there is a demand for stabilization of the torque sensor in accordance with the ongoing problem for the torque sensor signal.

Recently, the field-Claim status of the MDPS shows that the torque sensor problem accounts for 13% of the total, 40% of the type of problem that the handle heaviness occurs, and the direct cause of the intermittent handle heaviness is torque. Although it cannot be said that the sensor is a problem, it is necessary to improve the torque sensor in that the robustness of the torque sensor corresponding to the input of the MDPS system is intended to stabilize the overall MDPS system.

Currently, when a problem occurs in the torque sensor, logic for entering a control stop mode (Manual Assist) is applied.

In other words, most car manufacturers apply logic to enter the control stop mode (manual mode) to stop the control of the MDPS system when a problem occurs in the output of the torque sensor, and some manufacturers apply to sudden steering control stop. Fail-safe logic with a certain level of steering control is applied to minimize the effect.

Here, the conventional torque sensor fail-safe, that is, with reference to Figure 6 attached to the failure diagnosis example as follows.

As the existing method, the diagnosis of the analog torque sensor is limited to disconnection / short circuit, and the main parameters such as threshold level, counter (high, low), and counter increment are repeated. Determined through experimentation or past experience.

Therefore, when the failure diagnosis is started, if the engine speed for driving is 330 rpm or more (S500), the threshold value of the torque sensor is determined (S501).

As a result of determination, if the current sensed value of the torque sensor is smaller than the threshold torque lower limit value, the torque sensor fault counter is considered to be inadequately sensed (S502), and the torque sensor fault counter exceeds the threshold counter lower limit value. If not, the number of times of execution of the counter is stored and the diagnosis is performed again (S503). When the torque sensor failure counter exceeds the threshold counter lower limit value, it is determined that the torque sensor is disconnected / shorted (S504).

However, the fault diagnosis of the analog torque sensor is limited to disconnection / short. Therefore, in order to secure steering stability and stability of the MDPS system, the development of a new torque sensor and the development of a new fail-safe logic are required. It is becoming.

The present invention has been made in view of the above, by adopting a method in which the rotor position information of the torque sensor is transmitted to the ECU using the Cent protocol, torque based on a variety of information that the Cent Protocol (SENT Protocol) has By providing an effective fail-safe for the sensor, a method of fail-safe implementation of an electric power steering device, which is more robust against noise than the analog type, and has a control stability and a steering stability, can be obtained. The purpose is to provide.

The present invention for achieving the above object is the step of transmitting the sensed information of the torque sensor to the ECU in the form of Cent Protocol (SENT Protocol) through the AI chip; Performing a failure diagnosis of the torque sensor based on any one selected from among various pieces of information of the cent protocol in the ECU; It provides a fail-safe implementation method of the electric power steering device, characterized in that consisting of.

The step of diagnosing the failure of the torque sensor according to the first embodiment of the present invention includes: when the engine speed for driving reaches a predetermined level or more, whether the torque sensor status is invaded from the cent sensor information of the torque sensor. Judging; If the status nibble is determined to be in an error or invalid state, executing a torque sensor status invalid counter; If the torque sensor status invalid counter is less than or equal to the threshold value, the number of counter executions is stored and diagnosis is performed again; if more than the threshold maximum value, determining that the torque sensor is out of order; It characterized in that proceeds to.

The step of diagnosing the failure of the torque sensor according to the second embodiment of the present invention includes: determining whether the torque sensor thumb state is correct from the cent information of the torque sensor when the engine speed for driving reaches a predetermined level or more; If it is determined that the thumb nibble is incorrect, performing a torque sensor thumb counter; If the torque sensor thumb counter is less than or equal to the threshold, the number of counter executions is stored and the diagnostic is performed again; It characterized in that proceeds to.

The diagnosing the failure of the torque sensor according to the third embodiment of the present invention may include: when the engine speed for driving reaches a predetermined level or more, checking a predetermined number of falling edges from the cent information of the torque sensor. A decision step; If it is determined that the number of falling edges is not a predetermined number, executing a torque sensor timeout counter; If the torque sensor timeout counter is less than or equal to the threshold value, the number of times of execution of the counter is stored and diagnostic is performed again; It characterized in that proceeds to.

The step of diagnosing the failure of the torque sensor according to the fourth embodiment of the present invention includes: checking contents errors from the cent information of the torque sensor when the engine speed for driving reaches a predetermined level or more; Comparing the torque values calculated by SENT1 and the subsequent SENT2 to each other and performing a torque sensor total fault counter if the difference is greater than the reference difference [offset (Δ)]; ; If the torque sensor total fault count threshold value is less than or equal to the counter number of executions is stored and the diagnosis is performed again; if more than the threshold maximum value, determining the failure of the torque sensor; It characterized in that proceeds to.

Through the above-mentioned means for solving the problems, the present invention provides the following effects.

According to the present invention, in consideration of the fact that the sensing information of the torque sensor is transmitted to the ECU in the SENT Protocol format through the AIZ chip, any one selected from the various information possessed by the SENT Protocol. Based on this, it is possible to provide an efficient and accurate fail-safe determination method.

In particular, the fail-safe implementation method of the present invention is based on a variety of information that the SENT protocol has compared to the conventional analog type, it is excellent in the robustness against noise, and thus easy to control and steering stability of MDPS Can be secured.

1 is a schematic diagram showing the configuration of an electric steering apparatus;
2 is a schematic diagram illustrating a configuration of a torque sensor;
3 is a schematic diagram illustrating a detection and transmission method of a torque sensor;
4 and 5 are schematic diagrams illustrating cent protocol information of a torque sensor;
6 is a flowchart illustrating an example of a conventional torque sensor failure diagnosis.
7 is a flowchart illustrating a fail-safe implementation method of the electric power steering apparatus according to the first embodiment of the present invention;
8 is a flowchart illustrating a fail-safe implementation method of the electric power steering apparatus according to the second embodiment of the present invention;
9 is a flow chart illustrating a fail-safe implementation method of the electric power steering apparatus according to the third embodiment of the present invention;
10 is a flowchart illustrating a fail-safe implementation method of the electric power steering apparatus according to the fourth embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, in order to help the understanding of the present invention, a torque sensor based on a cent (SENT: Single Edge Nibble Transmission) and its signal transmission method will be described below.

In the configuration of the torque sensor, as shown in FIG. 2, an input rotor 21 and an output rotor 22 mounted vertically spaced apart from each other on a steering column shaft 20 are output rotor 22. And a stator 23 disposed therebetween.

In particular, a transmitter coil 30 (transmitter (TX) coil) and a receiver coil 32 (receiver (RX) coil) are formed at one side of the stator corresponding to the rotor, and a pair of azig 34 : ASIC) chip is installed.

Therefore, as shown in FIG. 3, when the rotor rotates according to the driver's steering intention, the induction current is measured using the transmitter coil 30 and the receiver coil 32, and the measured induction current is measured by AI chip. In 34), the value is converted into a value corresponding to the position information of the rotor.

Subsequently, the converted position information of the rotor is transmitted to the ECU in the form of SENT Protocol through the chip, and the ECU calculates the twist value based on the position information of the input rotor and the output rotor, and finally the torque value is obtained. Will be calculated.

The SENT protocol transmission method is a communication protocol used for one-way communication transmitted from the torque sensor to the ECU and is based on SAE J2716 (Jan. 2010).

Each nibble of the SENT (Single Edge Nibble Transmission) has a low level corresponding to the first 5 clock ticks and a [7 clock ticks +] as shown in FIG. Pulse width modulation (PWM) is formed by forming a high level corresponding to n (decimal) x clock tick].

At this time, in order to express the minimum nibble value 0, it has a low level corresponding to 5 clock ticks and a high level corresponding to 7 clock ticks.

In the nibble configuration of the SENT protocol, a calibration / synchronization nibble, a status nibble (Nibble # 1), and data, as shown in FIG. Nibble (Data nibble (Nibble # 2 ... # 7)), and checksum (Checksum (CRC) nibble (Nibble # 8)) and the like, and the configuration and function of each of the ribs are as follows.

/) Calibration / Synchronization Nibbler

It is fixed to 56 clock ticks in total, and consists of a low level of 5 clock ticks and a high level of 51 clock ticks.The ECU for electric power steering uses a clock tick (pulse period calculation). The actual time for the clock tick is calculated, and the compensation for the frequency deviation and delay in the transmission line of the oscillator in the sensor is performed.

Ii) status nibble

It contains status information about faults inside the sensor (MCU, ASIC, Resistive Short) and is used for sensor diagnosis.

Data nibble

It consists of a total of six nibbles, contains substantial data, and the configuration of the data nibbles can take many forms depending on the sensor and control logic.

For example, in the case of a SENT type torque sensor, two pieces of data are divided into nibbles # 2 to # 4 and nibbles # 5 to # 7 and transmitted.

첵) Thumb nibble

The ECU can check the checksum (CRC) to determine whether data has been corrupted during transmission.

Here, the torque sensor fail-safe determination method according to the first embodiment of the present invention based on the SENT protocol will be described with reference to FIG. 7.

Torque sensor fail-safe determination method according to the first embodiment contains the status information about the failure (MCU, ASIC, Resistive Short) inside the sensor, ECU by using the status nibble used for sensor diagnostics Is characterized in that the torque sensor failure detection is performed.

That is, in the case of the existing analog type, the sensor status information is not known, but in the present invention, the ECU can know the status information of the torque sensor through the status snivel, and in particular, the failure of the MCU or ASIC in the sensor and the resistance on the interface. When a short (Resistive short) occurs, it takes advantage of the fact that status information is sent to the ECU via status snippet.

According to the first embodiment, when the diagnosis is started, if the engine speed for driving is 330 rpm or more (S100), a step of determining whether or not to invade the torque sensor status is performed from the cent sensor information of the torque sensor (S101). ).

That is, when the position information of the rotor detected by the torque sensor is transmitted to the ECU in the SENT Protocol format through the AIZ chip, the status nibble (Nibble #) during the nibble configuration of the SENT protocol is performed. 1)] error or not.

As a result of the determination, if the status nibble is determined to be an error or an invalid state, it is assumed that the detection of the torque sensor is not performed properly, and the torque sensor status invalid counter (Sent_Torque_Invalid_Status_counter) is executed (S102).

Accordingly, if the torque sensor status invalid counter is less than or equal to the threshold value, the number of counter executions is stored and diagnosis is performed again (S103).

Here, the torque sensor fail-safe method according to the second embodiment of the present invention based on the SENT protocol will be described with reference to FIG. 8.

The torque sensor fail-safe determination method according to the second embodiment is characterized in that the failure of the torque sensor of the ECU is detected using a checksum nibble.

Since the output of the torque sensor is transmitted to the ECU through hard-wire, there is a possibility that the sensor output value is distorted and transmitted by electronic noise and mechanical vibration.

As the SENT Protocol includes checksum nibble, which allows you to check whether data has been damaged during transmission, the ECU determines whether the sensor value received through checksum calculation is distorted. do.

Therefore, when the failure diagnosis is started according to the second embodiment, if the engine speed for driving is 330 rpm or more (S200), a step of determining whether the torque sensor thumb state is correct from the cent sensor information of the torque sensor is performed (S201).

As a result of this determination, if the shock nibble is determined to be inaccurate, it is assumed that the detection of the torque sensor is not performed properly, and the torque sensor shock counter (Sent_Torque_Sensor_CRC_counter) is performed (S202).

Accordingly, when the torque sensor thumb counter is less than or equal to the threshold value, the number of counter executions is stored and diagnosis is performed again (S203).

Here, the torque sensor fail-safe method according to the third embodiment of the present invention based on the SENT protocol will be described with reference to FIG. 9.

Torque sensor fail-safe determination method according to the third embodiment is characterized in that the detection of the failure of the torque sensor of the ECU by checking the falling edge (Falling Edge).

One cent protocol has a total of nine falling edges, which means that the ECU will count the number of falling edges if there is a physical problem such as disconnection or short-circuit on the hard-wire. There is a feature of the third embodiment in that (9 points) are identified and a fault is detected.

Therefore, when the diagnosis is started according to the third embodiment, if the engine speed for driving is 330 rpm or more (S300), a determination step of checking whether the number of falling edges is 9 from the cent information of the torque sensor is performed. (S301).

At this time, if it is determined that the number of the falling edges is not nine, the torque sensor timeout counter Sent_Torque_Sensor_Timeout_counter is considered as not being properly sensed (S302).

Accordingly, when the torque sensor timeout counter is less than or equal to the threshold value, the number of counter executions is stored and diagnosis is performed again (S303). When the torque sensor timeout counter is less than or equal to the threshold maximum value, it is determined that the torque sensor has failed (S304).

Here, the torque sensor fail-safe method according to the fourth embodiment of the present invention based on the SENT protocol will be described with reference to FIG. 10.

The torque sensor fail-safe determination method according to the fourth embodiment is characterized in that a failure of the torque sensor of the ECU is detected by checking a contents error.

Since the position information of the rotor sensed by the torque sensor is transmitted to the ECU through cent 1 and subsequent cent 2, the calculated torque value is also the same.

In this case, the contents error check is performed by comparing the torque values calculated through SENT1 and the subsequent SENT2 with each other, and when the difference occurs more than the reference difference value [offset (Δ)]. This can be determined by fault detection, which enables the ECU to ensure the reliability of the sensor output, minimizing the possibility of false control due to incorrect sensor output.

Therefore, when the diagnosis is started according to the fourth embodiment, if the engine speed for driving is 330 rpm or more (S400), the contents error is checked from the cent information of the torque sensor (S401).

That is, when the torque value calculated by SENT1 and the subsequent SENT2 is compared with each other and the difference occurs more than the reference difference value [offset (Δ)], the torque sensor is not properly sensed. If not, the torque sensor sum fault counter (Torque_Sensor_Sum_fault_counter) is performed (S402).

Accordingly, if the torque sensor total fault count threshold is less than or equal to the threshold count, the counter execution count is stored and the diagnosis is performed again (S403).

As described above, the fail-safe implementation method of the electric power steering apparatus of the present invention has excellent robustness against noise and an effective fail-safe operation based on various information possessed by the SENT protocol. Since it can provide, the control stability and steering stability of MDPS can be ensured easily.

10: steering shaft
12: Reduction Gear Box
14: motor
16: ECU
18: torque sensor

Claims (5)

Transmitting the sensed information of the torque sensor to the ECU in the SENT Protocol format through the AIZ chip;
Performing a failure diagnosis of the torque sensor based on any one selected from among various pieces of information of the cent protocol in the ECU;
Fail-safe implementation method of the electric power steering device, characterized in that consisting of.
The method according to claim 1,
The step of performing a failure diagnosis of the torque sensor is:
Determining whether the torque sensor status is invaded from the cent sensor information of the torque sensor when the engine speed for driving exceeds a predetermined level;
If the status nibble is determined to be in an error or invalid state, executing a torque sensor status invalid counter;
If the torque sensor status invalid counter is less than or equal to the threshold value, the number of counter executions is stored and diagnosis is performed again; if more than the threshold maximum value, determining that the torque sensor is out of order;
Fail-safe implementation method of the electric power steering device, characterized in that proceeding to.
The method according to claim 1,
The step of performing a failure diagnosis of the torque sensor is:
When the engine speed for driving reaches a predetermined level or more, determining whether the torque sensor thumb state is correct from the cent information of the torque sensor;
If it is determined that the thumb nibble is incorrect, performing a torque sensor thumb counter;
If the torque sensor thumb counter is less than or equal to the threshold, the number of counter executions is stored and the diagnostic is performed again; if more than the threshold maximum, determining that the torque sensor is faulty;
Fail-safe implementation method of the electric power steering device, characterized in that proceeding to.
The method according to claim 1,
The step of performing a failure diagnosis of the torque sensor is:
A determination step of confirming a predetermined number of falling edges from the cent information of the torque sensor when the engine speed for driving reaches a predetermined level or more;
If it is determined that the number of falling edges is not a predetermined number, executing a torque sensor timeout counter;
If the torque sensor timeout counter is less than or equal to the threshold value, the number of counter executions is stored and diagnostic is performed again; if more than the threshold maximum value, determining that the torque sensor is out of order;
Fail-safe implementation method of the electric power steering device, characterized in that proceeding to.
The method according to claim 1,
The step of performing a failure diagnosis of the torque sensor is:
Checking the contents error from the cent information of the torque sensor when the engine speed for driving exceeds a predetermined level;
Comparing the torque values calculated by SENT1 and the subsequent SENT2 to each other and performing a torque sensor total fault counter if the difference is greater than the reference difference [offset (Δ)]; ;
If the torque sensor total fault count threshold value is less than or equal to the counter number of executions is stored and the diagnosis is performed again; if more than the threshold maximum value, determining the failure of the torque sensor;
Fail-safe implementation method of the electric power steering device, characterized in that proceeding to.

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