KR20200059858A - Apparatus and method for determining relay state of motor driven power steering system - Google Patents

Abstract

Disclosed are an apparatus and a method for determining a relay state of an electric power steering system. The apparatus for determining a relay state of an electric power steering system of the present invention includes: an inverter for supplying a d-axis current to a motor; a driving voltage measuring unit for measuring a driving voltage supplied to the inverter from a relay that interrupts power supplied from a battery to the inverter; and a control unit which applies the d-axis current to the motor through the inverter, cuts off the d-axis current, and determines a switching state of the relay using a battery voltage and a driving voltage of the battery.

Description

Apparatus and method for relay state determination 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 a relay state of an electric power steering system, and more specifically, to apply a current to a motor d-axis of an electric power steering system and monitor the Vlink voltage to monitor the relay switching state (ON / OFF). It relates to an apparatus and method for determining the relay state of the electric power steering system for determining.

The MDPS (Motor Driven Power Steering) has the advantages of light weight, less space, and no oil change when compared to the existing hydraulic power steering system.

The electric power steering system facilitates steering by providing a portion of the steering torque that the driver must apply to the steering wheel when steering the vehicle using an auxiliary power source. That is, the driver's steering intention is sensed through a torque sensor directly connected to the steering wheel, and the electric power steering system receives this signal to assist the steering force by driving the motor to provide an appropriate force in consideration of the current speed of the vehicle. The electric power steering system helps to maintain the stability of the vehicle body by assisting the driver in reducing the power of the driver by assisting with a large force when the vehicle is stopped or driving at a low speed, and by using only a small force when driving at a high speed.

The ECU of the electric power steering system senses the driver's steering will and calculates and assists the current required to drive the motor, which is the actuator. The ECU receives the power required to drive the motor through the FET relay switch to 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 state of the corresponding relay.

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

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

The background technology of the present invention is disclosed in 'Fail Safe Control Method in Electric Power Steering System' of Korean Patent Registration No. 10-0835197 (2008.05.29).

The present invention was devised to improve the above-mentioned problems, and an object according to an aspect of the present invention is to apply a d-axis current to a motor of an electric power steering device and monitor the motor driving voltage to monitor the switching state of the relay (ON / It is an object to provide an apparatus and method for determining a relay state of an electric power steering system for determining OFF).

An apparatus for determining a relay state of an electric power steering system according to an aspect of the present invention includes an inverter that supplies a d-axis current to a motor; A driving voltage measuring unit measuring a driving voltage supplied to the inverter from a relay that interrupts power supplied from the battery to the inverter; And after applying the d-axis current to the motor through the inverter to block, it characterized in that it comprises a control unit for determining the switching state of the relay using the battery voltage and the driving voltage of the battery.

The control unit of the present invention is characterized by comparing the difference value between the battery voltage and the driving voltage with a preset voltage to determine the switching state of the relay according to the comparison result.

The controller of the present invention is characterized in that when the difference value between the battery voltage and the driving voltage exceeds the set voltage, the switching state of the relay is determined to be off.

The controller of the present invention is characterized in that when the difference value between the battery voltage and the driving voltage is equal to or less than the set voltage, the switch state of the relay is determined to be on.

The controller of the present invention is characterized in that the relay is turned off when the switching state of the relay is determined to be on.

The controller of the present invention determines that the switching state of the relay is on, and after turning off the relay, the d-axis current is again applied to the motor to cut off, and then the battery voltage and the driving voltage of the battery are used. It is characterized in that to determine the switching state of the relay.

A relay state determining method of an electric power steering system according to an aspect of the present invention includes: controlling, after applying a d-axis current to a motor through an inverter, blocking the relay state; When the d-axis current is cut off, the driving voltage measuring unit measures a driving voltage supplied to the inverter from a relay that interrupts power supplied from the battery to the inverter; And determining, by the controller, the switching state of the relay using the battery voltage and the driving voltage of the battery.

In the step of determining the switching state of the relay of the present invention, the controller compares the difference value between the battery voltage and the driving voltage with a preset voltage to determine 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, when the difference value between the battery voltage and the driving voltage exceeds the set voltage, the controller determines that the switching state of the relay is in an off state.

In the step of determining the switching state of the relay of the present invention, if the difference value between the battery voltage and the driving voltage is equal to or less than the set voltage, the control unit is characterized in that the switching state of the relay is determined to be on.

The present invention is characterized in that it further comprises the step of turning off the relay by the control unit 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 applies the d-axis current to the motor again and blocks it, and then uses the battery voltage and the driving voltage of the battery It characterized in that it further comprises the step of determining the switching state of the relay.

An apparatus and method for determining a relay state of an electric power steering system according to an aspect of the present invention is a relay switching state (ON / OFF) can be determined by software, reducing the material cost, size, and element defect rate.

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

Hereinafter, an apparatus and method for determining a relay state of an electric power steering system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this process, the thickness of the lines or the size of components shown in the drawings may be exaggerated for clarity and convenience. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user or operator's intention or practice. Therefore, the definition of these terms should be made based on the contents throughout the specification.

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

Referring to FIG. 1, an apparatus for determining a relay state of an 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 controller 60 to apply a driving current to the motor 40.

Here, the motor 40 is a three-phase motor 40, and is composed 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. The switching module includes a field effective transistor (FET), and the control unit 60 drives the motor 40 by turning on or off each switching module.

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

The relay 20 interrupts the power supplied from the battery 10 to the inverter 30. The relay 20 forms a large current path supplied from the battery 10 to the inverter 30 for driving a motor that consumes a lot of current during rotation.

In particular, the relay 20 must determine whether its switching state, that 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.

After applying the d-axis current to the motor 40 through the inverter 30 through the inverter 30, the controller 60 cuts off the d-axis current, and thereafter, the battery voltage Vbatt and the driving voltage of the battery 10 ( Vlink) to determine the switching state of the relay 20.

In more detail, first, the controller 60 controls the inverter 30 to apply the d-axis current to the motor 40.

The d-axis current is a current perpendicular to the torque direction of the motor 40. When the d-axis current is applied to the motor 40, the torque is 0, that is, it does not rotate. In this case, when the relay 20 is in the turned-on state, The current supplied by the driving voltage Vlink is consumed without the motor 40 rotating.

Accordingly, the controller 60 supplies the d-axis current to the motor 40 through the inverter 30 and controls the inverter 30 to block the d-axis current supply when the set time has elapsed.

Subsequently, 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 value between the battery voltage Vbatt and the driving voltage Vlink with a preset voltage, for example, 0.9 V to determine the switching state of the relay 20 according to the comparison result. .

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

This is shown in Fig. 2 (a) when the battery voltage (Vbatt) and the driving voltage (Vlink) remain the same when the relay 20 is turned on and the driving voltage (Vlink) is applied. This is because the driving voltage Vlink is reduced as described above.

On the other hand, when the relay 20 is turned off, the battery voltage Vbatt and the driving voltage Vlink are kept the same, and even after the d-axis current is applied, as shown in FIG. 2 (b), the driving voltage ( Vlink) remains constant.

That is, in the state in which the relay 20 is turned on, when the d-axis current is applied to the motor 40, the driving voltage Vlink is reduced to be different from the battery voltage Vbatt, so the controller 60 controls the battery voltage Vbatt. The switching state of the relay 20 may be determined based on whether the difference value between the overdrive voltage Vlink exceeds the set voltage.

On the other hand, if it is determined that the switching state of the relay 20 is on, as described above, the controller 60 turns off the relay 20, and applies the d-axis current to the motor 40 again to block it. Then, the switching state of the relay 20 is again determined 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 the fail-safe mode.

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

3 is a flowchart of a relay state determining method 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 the d-axis current to the motor 40 (S10).

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

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

In this case, the driving voltage measuring unit 50 measures the driving voltage Vlink supplied from the battery 10 to the inverter 30 from the relay 20 that interrupts the power supplied to the inverter 30.

On the other hand, as the d-axis current supply is cut off, the control unit 60 calculates a difference value between the battery voltage Vbatt of the battery 10 and the driving voltage Vlink measured by the driving voltage measurement unit 50.

 As the difference value between the battery voltage Vbatt and the driving voltage Vlink is calculated, the control unit 60 sets a preset voltage, for example, 0.9V, between the battery voltage Vbatt and the driving voltage Vlink. It is determined 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 equal to or less than a preset voltage, the controller 60 determines the switching state of the relay 20 to be off (S70). .

On the other hand, if the difference value between the battery voltage Vbatt and the driving voltage Vlink exceeds the preset voltage as a result of the determination in step S40, the controller 60 determines the relay state to be on (S50). , After turning off the relay 20 (S60), returns to step S10.

Accordingly, the control unit 60 applies the d-axis current to the motor 40 through the inverter 30 and then blocks the d-axis current supplied to the motor 40 through the inverter 30 when the set time has elapsed ( S10 ~ S30), calculates a difference value between the battery voltage Vbatt and the driving voltage Vlink measured by the driving voltage measuring unit 50, determines whether the difference value exceeds the set voltage (S40), and then determines The relay state is determined to be off according to the result (S70).

As described above, the relay state determining device and method of the electric power steering system according to an embodiment of the present invention apply a d-axis current to the motor 40 in the fail-safe mode of the electric power steering system and then drive voltage (Vlink) By monitoring, the switching state (ON / OFF) of the relay 20 can be determined in software, thereby reducing the material cost, size, and element defect rate.

The present invention has been described with reference to the embodiment shown in the drawings, but this is only exemplary, and those skilled in the art to which the technology belongs can recognize that various modifications and other equivalent embodiments are possible therefrom. Will understand. Therefore, the true technical protection scope of the present invention should be defined by the claims below.

10: battery
20: relay
30: inverter
40: motor
50: driving voltage measuring unit
60: control unit

Claims (12)

An inverter that supplies a d-axis current to the motor;
A driving voltage measuring unit measuring a driving voltage supplied to the inverter from a relay that interrupts power supplied from the battery to the inverter; And
After applying the d-axis current to the motor through the inverter to cut off, and using the battery voltage and the drive voltage of the battery to determine the switching state of the relay Relay status determination device of the electric power steering system .
The relay state of claim 1, wherein the controller determines a switching state of the relay according to a comparison result by comparing the difference value between the battery voltage and the driving voltage with a preset voltage. Discrimination device.
The device of claim 2, wherein the controller determines the switching state of the relay to be off when the difference between the battery voltage and the driving voltage exceeds the set voltage. .
The device of claim 2, wherein the controller determines the switch state of the relay to be on when the difference between the battery voltage and the driving voltage is equal to or less than the set voltage.
The apparatus of claim 1, wherein the control unit turns off the relay when the switching state of the relay is determined to be on.
The battery voltage and the driving of the battery according to claim 5, wherein the controller applies the d-axis current to the motor again after turning off the relay after the switching state of the relay is determined to be on and off. Device for determining the relay state of the electric power steering system, characterized in that for determining the switching state of the relay using a voltage.
A step in which the controller applies a d-axis current to the motor through an inverter and then blocks;
When the d-axis current is cut off, the driving voltage measuring unit measures a driving voltage supplied to the inverter from a relay that interrupts power supplied from the battery to the inverter; And
And determining, by the controller, the switching state of the relay using the battery voltage and the driving voltage of the battery.
According to claim 7, In the step of determining the switching state of the relay,
The controller compares the difference value between the battery voltage and the driving voltage with a preset voltage, and determines a relay state of the electric power steering system according to a comparison result.
According to claim 8, In the step of determining the switching state of the relay,
The control unit determines the relay state of the electric power steering system, characterized in that when the difference value between the battery voltage and the driving voltage exceeds the set voltage, the switching state of the relay is determined to be off.
According to claim 8, In the step of determining the switching state of the relay,
The control unit determines the relay state of the electric power steering system, characterized in that when the difference value between the battery voltage and the driving voltage is equal to or less than the set voltage, the switch state of the relay is turned on.
The method of claim 7, further comprising turning off the relay by the control unit when the switching state of the relay is determined to be on.
The battery voltage and the driving of the battery according to claim 11, wherein after the switching state of the relay is determined to be on and the relay is turned off, the controller re-applies and cuts off the d-axis current to the motor. And determining a switching state of the relay by using a voltage.

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