KR102591717B1 - Apparatus and method for determining relay state of motor driven power steering system - Google Patents

Abstract

An apparatus and method for determining the relay status of an electric power steering system are disclosed. The relay status determination device for the electric power steering system of the present invention includes an inverter that supplies d-axis current to the motor; a driving voltage measuring unit that measures the driving voltage supplied to the inverter from a relay that controls power supplied to the inverter from a battery; And a control unit that applies and blocks the d-axis current to the motor through an inverter and then determines the switching state of the relay using the battery voltage and driving voltage of the battery.

Description

Apparatus and method for determining relay status of electric power steering system {APPARATUS AND METHOD FOR DETERMINING RELAY STATE OF MOTOR DRIVEN POWER STEERING SYSTEM}

The present invention relates to an apparatus and method for determining the relay status of an electric power steering system, and more specifically, to determine the switching status (ON/OFF) of the relay by monitoring the Vlink voltage after applying current to the motor d-axis of the electric power steering system. It relates to an apparatus and method for determining the relay status of an electric power steering system.

Compared to existing hydraulic power steering systems, the Motor Driven Power Steering (MDPS) system has the advantage of being lighter in weight, taking up less space, and not requiring oil changes.

The electric power steering system facilitates steering by providing part of the steering torque that the driver must apply to the steering wheel when steering a vehicle using an auxiliary power source. In other words, the driver's steering intention is detected through a torque sensor directly connected to the steering wheel, and the electric power steering system receives this signal and drives the motor to provide appropriate force in consideration of the current speed of the car, thereby assisting the steering force. The electric power steering system reduces the driver's effort by applying a large amount of force when the car is parked or driving at low speeds, and maintains the stability of the vehicle body by assisting only a small amount of force when driving at high speeds.

The ECU of this electric power steering system senses the driver's steering intention and calculates and assists the current required to drive the motor, which is an actuator. The ECU receives the power needed to drive the motor through the FET relay switch from the voltage coming from the vehicle battery. Accordingly, for fail-safe operation of the electric power steering system, it is essential to determine the switching status of the relevant relay.

Accordingly, conventionally, the switching state (On/OFF) of the relay was determined by discharging the driving voltage (Link voltage) using a FET relay switch controlled through an MCU in hardware.

However, since the conventional method uses a hardware circuit as described above, there is a problem in that material cost, size, and device defect rate increase.

The background technology of the present invention is disclosed in Korean Patent Publication No. 10-0835197 (May 29, 2008) titled ‘Fail Safe Control Method in Electric Power Steering System’.

The present invention was created to improve the above-mentioned problems, and the purpose of one aspect of the present invention is to monitor the motor driving voltage after applying the d-axis current to the motor of the electric power steering device to change the switching state (ON/ON) of the relay. The purpose is to provide a device and method for determining the relay status of an electric power steering system that determines OFF).

A relay status determination device for an electric power steering system according to an aspect of the present invention includes an inverter that supplies d-axis current to a motor; a driving voltage measuring unit that measures the driving voltage supplied to the inverter from a relay that controls power supplied to the inverter from a battery; and a control unit that applies and blocks the d-axis current to the motor through the inverter and then determines the switching state of the relay using the battery voltage of the battery and the driving voltage.

The control unit of the present invention compares the difference value between the battery voltage and the driving voltage with a preset set voltage and determines the switching state of the relay according to the comparison result.

The control unit of the present invention is characterized in that it determines the switching state of the relay as off when the difference between the battery voltage and the driving voltage exceeds the set voltage.

The control unit of the present invention is characterized in that it determines the switch state of the relay as on when the difference between the battery voltage and the driving voltage is less than or equal to the set voltage.

The control unit of the present invention is characterized in that it turns off the relay when the switching state of the relay is determined to be on.

After the control unit of the present invention determines that the switching state of the relay is on and turns off the relay, it re-applies the d-axis current to the motor to block it, and then uses the battery voltage of the battery and the driving voltage. This is characterized in that the switching state of the relay is determined.

A method for determining the relay status of an electric power steering system according to an aspect of the present invention includes the steps of a control unit applying d-axis current to a motor through an inverter and then blocking it; When the d-axis current is cut off, a driving voltage measuring unit measures the driving voltage supplied to the inverter from a relay that regulates power supplied to the inverter from a battery; and the control unit determining the switching state of the relay using the battery voltage of the battery and the driving voltage.

In the step of determining the switching state of the relay of the present invention, the control unit compares the difference between the battery voltage and the driving voltage with a preset set voltage and determines the switching state of the relay according to the comparison result. do.

In the step of determining the switching state of the relay of the present invention, the control unit determines the switching state of the relay as off when the difference between the battery voltage and the driving voltage exceeds the set voltage.

In the step of determining the switching state of the relay of the present invention, the control unit determines the switch state of the relay as on if the difference between the battery voltage and the driving voltage is less than or equal to the set voltage.

The present invention further includes the step of the control unit turning off the relay when the switching state of the relay is determined to be on.

After the switching state of the relay of the present invention is determined to be on and the relay is turned off, the control unit reapplies the d-axis current to the motor to block it, and then uses the battery voltage of the battery and the driving voltage. The method further includes the step of determining the switching state of the relay.

An apparatus and method for determining the relay status of an electric power steering system according to an aspect of the present invention monitors the driving voltage after applying the d-axis current to the motor in the fail-safe mode of the electric power steering system to determine the switching state (ON/ON) of the relay. OFF) can be determined through software, reducing material costs, size, and device defect rate.

1 is a block diagram of a relay status determination device for an electric power steering system according to an embodiment of the present invention.
Figure 2 is a diagram showing the change in driving voltage according to the application of d-axis current when the relay is on and off.
Figure 3 is a flowchart of a method for determining the relay status of an electric power steering system according to an embodiment of the present invention.

Hereinafter, an apparatus and method for determining the relay status of an electric power steering system according to an embodiment of the present invention will be described in detail with reference to the attached drawings. In this process, the thickness of lines or sizes of components shown in the drawings may be exaggerated for clarity and convenience of explanation. In addition, the terms described below are terms defined in consideration of functions in the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, definitions of these terms should be made based on the content throughout this specification.

Figure 1 is a block diagram of a relay status determination device for an electric power steering system according to an embodiment of the present invention, and Figure 2 is a diagram showing the change in driving voltage according to the application of d-axis current when the relay is on and off.

Referring to FIG. 1, the relay status determination device of the electric power steering system according to an embodiment of the present invention includes an inverter 30, a driving voltage measuring unit 50, and a control unit 60.

The inverter 30 switches the power supplied from the battery 10 through the relay 20 according to the PWM control of the control unit 60 and applies a driving current to the motor 40.

Here, the motor 40 is a three-phase motor 40 and consists of a U-phase, a W-phase, and a V-phase, and each phase is controlled by being connected to a switching module of the inverter 30 corresponding to each phase.

The switching module of the inverter 30 controls the motor 40 by adjusting the motor current supplied to the motor 40 according to the switching operation of the switching module according to the operation signal input from the control unit 60. These switching modules include a Field Effective Transister (FET), and the control unit 60 drives the motor 40 by turning on or off each switching module.

The relay 20 regulates the power supplied from the battery 10 to the inverter 30. The relay 20 is turned on or off according to a control signal from the controller 60.

This relay 20 regulates the power supplied from the battery 10 to the inverter 30. This relay 20 forms a high current path supplied from the battery 10 to the inverter 30 to drive a motor that consumes a lot of current when rotating.

In particular, the relay 20 must determine its switching state, that is, whether it is on or off, for fail-safe operation of the motor driven power steering system.

Meanwhile, the driving voltage measuring unit 50 measures the driving voltage (Vlink) supplied from the relay 20 to the inverter 30.

The control unit 60 applies the d-axis current to the motor 40 through the inverter 30 and blocks the d-axis current when a set time has elapsed, and then the battery voltage (Vbatt) and the driving voltage ( Vlink) is used to determine the switching state of the relay 20.

To explain in more detail, first, the control unit 60 controls the inverter 30 to apply d-axis current to the motor 40.

The d-axis current is a current perpendicular to the torque direction of the motor 40, and when the d-axis current is applied, the motor 40 has a torque of 0, that is, does not rotate. In this case, if the relay 20 is turned on, Even when the motor 40 does not rotate, the current supplied by the driving voltage (Vlink) is consumed.

Accordingly, the control unit 60 supplies the d-axis current to the motor 40 through the inverter 30, and when the set time elapses, it controls the inverter 30 to block the d-axis current supply.

Next, the control unit 60 determines the switching state of the relay 20 using the battery voltage (Vbatt) of the battery 10 and the driving voltage (Vlink) measured by the driving voltage measurement unit 50. In this case, the control unit 60 compares the difference between the battery voltage (Vbatt) and the driving voltage (Vlink) with a preset voltage, for example, 0.9V, and determines the switching state of the relay 20 according to the comparison result. .

In this case, the control unit 60 determines the switching state of the relay 20 as off when the difference value between the battery voltage (Vbatt) and the driving voltage (Vlink) exceeds the set voltage, and If the difference value of (Vlink) is less than the set voltage, the switch state of the relay 20 is determined to be in the on state.

This is shown in (a) of FIG. 2 when the relay 20 is turned on and the driving voltage (Vlink) is applied, the battery voltage (Vbatt) and the driving voltage (Vlink) remain the same, and then when the d-axis current is applied, This is because the driving voltage (Vlink) decreases as shown.

On the other hand, when the relay 20 is turned off, the battery voltage (Vbatt) and the driving voltage (Vlink) remain the same, and even if the d-axis current is applied thereafter, the driving voltage ( Vlink) remains constant.

That is, when the relay 20 is turned on, when the d-axis current is applied to the motor 40, the driving voltage (Vlink) decreases and becomes different from the battery voltage (Vbatt), so the control unit 60 controls the battery voltage (Vbatt) The switching state of the relay 20 can be determined based on whether the difference between the and driving voltage (Vlink) exceeds the set voltage.

Meanwhile, when it is determined that the switching state of the relay 20 is on as described above, the control unit 60 turns off the relay 20 and re-applies the d-axis current to the motor 40 to block it. Afterwards, the switching state of the relay 20 is determined again using the battery voltage (Vbatt) and the driving voltage (Vlink) of the battery 10. Through this, the control unit 60 can accurately determine the switching state of the relay 20 in fail-safe mode.

Hereinafter, a method for determining the relay status of an electric power steering system according to an embodiment of the present invention will be described in detail with reference to FIG. 3.

Figure 3 is a flowchart of a method for determining the relay status of an electric power steering system according to an embodiment of the present invention.

Referring to FIG. 3, the control unit 60 controls the inverter 30 to apply d-axis current to the motor 40 (S10).

After applying the d-axis current to the motor 40 through the inverter 30, the control unit 60 determines whether a preset time has elapsed (S20).

As a result of the determination in step S20, when the set time elapses after applying the d-axis current, the control unit 60 blocks the d-axis current supply through the inverter 30 (S30).

In this case, the driving voltage measuring unit 50 measures the driving voltage (Vlink) supplied to the inverter 30 from the relay 20, which regulates the power supplied to the inverter 30 from the battery 10.

Meanwhile, as the d-axis current supply is cut off, the control unit 60 calculates the difference between the battery voltage (Vbatt) of the battery 10 and the driving voltage (Vlink) measured by the driving voltage measuring unit 50.

As the difference value between the battery voltage (Vbatt) and the driving voltage (Vlink) is calculated, the control unit 60 sets the difference value between the battery voltage (Vbatt) and the driving voltage (Vlink) to a preset set voltage, for example, 0.9V. Determine whether it exceeds (S40).

As a result of the determination in step S40, if the difference value between the battery voltage (Vbatt) and the driving voltage (Vlink) is less than or equal to a preset voltage, the control unit 60 determines the switching state of the relay 20 to be in the off state (S70) .

On the other hand, if the difference between the battery voltage (Vbatt) and the driving voltage (Vlink) exceeds the preset voltage as determined in step S40, the control unit 60 determines the relay to be in the on state (S50). , turn off the relay 20 (S60), and then return to step S10.

Accordingly, the control unit 60 applies the d-axis current to the motor 40 through the inverter 30, and after a set time has elapsed, the control unit 60 blocks the d-axis current supplied to the motor 40 through the inverter 30 ( S10 to S30), calculate the difference between the battery voltage (Vbatt) and the driving voltage (Vlink) measured by the driving voltage measuring unit 50, and determine whether this difference exceeds the set voltage (S40), and then make a decision. According to the result, the relay state is determined to be off (S70).

As such, the apparatus and method for determining the relay status of an electric power steering system according to an embodiment of the present invention applies the d-axis current to the motor 40 in the fail-safe mode of the electric power steering system and then changes the driving voltage (Vlink). By monitoring, the switching state (ON/OFF) of the relay 20 can be determined through software, thereby reducing material cost, size, and device defect rate.

The present invention has been described with reference to the embodiments shown in the drawings, but these are merely illustrative, and those skilled in the art will recognize that various modifications and other equivalent embodiments can be made therefrom. You will understand. Therefore, the true technical protection scope of the present invention should be determined by the scope of the patent claims below.

10: battery
20: relay
30: inverter
40: motor
50: Driving voltage measurement unit
60: control unit

Claims (12)

an inverter that supplies d-axis current to the motor;
a driving voltage measuring unit that measures the driving voltage supplied to the inverter from a relay that controls power supplied to the inverter from a battery; and
A control unit that applies the d-axis current to the motor through the inverter and then blocks it, and determines the switching state of the relay using the battery voltage of the battery and the driving voltage,
The control unit compares the difference between the battery voltage and the driving voltage with a preset set voltage and determines the switching state of the relay according to the comparison result.
delete The relay state determination device of claim 1, wherein the control unit determines the switching state of the relay as off when the difference value between the battery voltage and the driving voltage exceeds the set voltage. .
The device of claim 1, wherein the control unit determines the switch state of the relay as on when the difference between the battery voltage and the driving voltage is less than or equal to the set voltage.
The device of claim 1, wherein the control unit turns off the relay when the switching state of the relay is determined to be on.
The method of claim 5, wherein after the control unit determines that the switching state of the relay is on and turns off the relay, the d-axis current is reapplied to the motor and then blocked, and the battery voltage of the battery and the driving A relay status determination device for an electric power steering system, characterized in that the switching status of the relay is determined using voltage.
A step where the control unit applies d-axis current to the motor through an inverter and then blocks it;
When the d-axis current is cut off, a driving voltage measuring unit measures the driving voltage supplied to the inverter from a relay that regulates power supplied to the inverter from a battery; and
The control unit includes a step of determining the switching state of the relay using the battery voltage of the battery and the driving voltage,
In the step of determining the switching state of the relay, the control unit compares the difference between the battery voltage and the driving voltage with a preset set voltage and determines the switching state of the relay according to the comparison result. How to determine the relay status of the steering system.
delete The method of claim 7, wherein in determining the switching state of the relay,
The control unit determines the switching state of the relay as off when the difference between the battery voltage and the driving voltage exceeds the set voltage.
The method of claim 7, wherein in determining the switching state of the relay,
The control unit determines the switch state of the relay as on when the difference between the battery voltage and the driving voltage is less than or equal to the set voltage.
The method of claim 7, further comprising the step of the control unit turning off the relay when the switching state of the relay is determined to be on.
The method of claim 11, wherein after the switching state of the relay is determined to be on and the relay is turned off, the control unit reapplies the d-axis current to the motor and then blocks it, and the battery voltage of the battery and the driving A method for determining the relay state of an electric power steering system, further comprising the step of determining the switching state of the relay using voltage.

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