KR101615790B1

KR101615790B1 - Electric power steering apparatus and current controlling method thereof

Info

Publication number: KR101615790B1
Application number: KR1020120087785A
Authority: KR
Inventors: 김태욱
Original assignee: 주식회사 만도
Priority date: 2012-08-10
Filing date: 2012-08-10
Publication date: 2016-04-26
Also published as: KR20140021369A

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for controlling stable motor drive in an electric steering system.
The present invention is characterized by comprising: a voltage comparison step of comparing a supply voltage value supplied from a power supply means and a preset drive voltage value; A bootstrap execution step of generating a control signal so that the bootstrap capacitor is charged when the supply voltage value is equal to or lower than the drive voltage value; And a motor driving step of driving the motor of the electric power steering apparatus when a predetermined capacitor charging time has elapsed.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for controlling stable motor drive in an electric steering system.

Generally, a hydraulic steering apparatus using a hydraulic pressure of a hydraulic pump is used as a steering apparatus of an automobile, but an electric steering system using a motor since 1990 has become popular.

In the hydraulic steering system, the hydraulic pump, which is the power source for supplying the steering assist power, is always driven by the engine to consume energy regardless of whether the steering wheel rotates or not. The motor supplies the steering assist power proportional to the generated steering torque. Therefore, when the electric steering system is used, the energy efficiency can be improved as compared with the case of using the hydraulic steering system.

The electric steering apparatus is configured such that the steering torque generated by the rotation of the steering wheel is transmitted to the rack bar via the rack-and-pinion mechanism portion, and the steering assist force generated by the motor is transmitted to the rack bar according to the generated steering torque. That is, the steering torque generated by the steering wheel and the steering assist power generated by the motor are combined to move the rack bar in the axial direction.

When the electric power is supplied to the electric power steering apparatus, the voltage is gradually increased from the low voltage to be higher than the reference voltage and must be higher than the reference voltage The motor can perform normal driving.

However, when the electric power steering apparatus is operated by lowering the reference voltage value, there is a case where the inverter unit must operate before sufficient power is supplied to the inverter unit for controlling the driving of the motor in the initial driving, And thus the operation of the motor becomes unstable.

SUMMARY OF THE INVENTION In view of the foregoing, an object of the present invention is to provide an electric steering system and a control method thereof that enable stable motor drive control during an initial operation.

In order to achieve the above-mentioned object, in one aspect, the present invention provides a power supply apparatus comprising: a voltage comparing step of comparing a supply voltage value supplied from a power supply means with a predetermined drive voltage value; A bootstrap execution step of generating a control signal so that the bootstrap capacitor is charged when the supply voltage value is equal to or lower than the drive voltage value; And a motor driving step of driving the motor of the electric power steering apparatus when a preset capacitor charging time has elapsed.

According to another aspect of the present invention, there is provided an inverter circuit comprising: an inverter unit for controlling driving of a motor while a plurality of switching elements are turned on and off; A voltage ratio supply unit for comparing a supply voltage value supplied from the power supply unit with a predetermined drive voltage value; And a bootstrap charge controller for generating a control signal for charging the bootstrap capacitor when the supply voltage value is equal to or less than a preset drive voltage value, and transmitting the control signal to the inverter unit.

As described above, according to the present invention, it is possible to stably operate the steering apparatus even at a low supply voltage.

FIG. 1 is a view illustrating the configuration of an electric power steering apparatus according to an embodiment of the present invention.
Fig. 2 is a diagram showing the configuration of the electric power steering apparatus of Fig. 1 in more detail.
3 is a view illustrating a control method of an electric power steering apparatus according to an embodiment of the present invention.
FIG. 4 is a graph illustrating a control method of an electric steering apparatus according to an embodiment of the present invention. Referring to FIG.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. In the drawings, like reference numerals are used to designate identical or similar elements throughout the drawings. Note that, in the following description of the present invention, The detailed description of the constitution or function will be omitted if it is judged that the detailed description of the constitution or the function may obscure the gist of the present invention.

In this specification, 'motor' represents the same components as the 'steering motor' constituting the electric power steering apparatus. Hereinafter, 'steering motor' and 'motor' may be used in combination according to the description.

FIG. 1 is a view illustrating the configuration of an electric power steering apparatus according to an embodiment of the present invention.

Referring to FIG. 1, an electric steering system according to an embodiment of the present invention includes a motor 10, an inverter 20 for controlling the driving of the motor 10, And a drive control unit (40) for controlling the operation.

The apparatus further includes a power supply unit 50 for supplying power and a driver driving unit 30 for applying a control signal to the inverter unit 20 under the control of the drive control unit 40.

The drive control unit 40 includes a voltage ratio generation unit 110 for comparing a supply voltage value supplied from the power supply unit 50 with a preset drive voltage value, And a bootstrap charge control unit 120 for generating a control signal to charge the capacitor to the inverter unit 20 so that the bootstrap capacitor is charged before the supply voltage is lower than the drive voltage, So that stable motor drive control can be performed.

The inverter unit 20 includes a plurality of switching elements and supplies current to the motor 10 while repeating ON / OFF of each switching element according to a control signal transmitted from the driver driving unit 30, The rotational speed or the rotational direction of the motor 10 is determined by the supplied current according to the ON / OFF operation of the switching element.

Fig. 2 is a circuit diagram of the electric power steering apparatus of Fig. 1, in which the inverter unit is shown in more detail.

Referring to FIG. 2, the inverter unit 20 of the electric power steering system according to the embodiment of the present invention includes four switching elements on the high-side, two switching elements AH, BH, and the bootstrap capacitors Ca and Cb are connected to the high side switching devices AH and BH, respectively. The bootstrap capacitors Ca and Cb are connected to the high side switching devices AH and BH, respectively. 2, each of the switching elements AH, BH, AL, and BL is shown as an NMOS FET and four NMOS FETs as an H-bridge circuit. However, each switching element is not limited to an NMOS FET, And can be modified by those skilled in the art.

Each of the switching elements AH, BH, AL and BL performs on / off operation by a gate signal applied from the driver driving unit 30. The bootstrap capacitors Ca and Cb are connected to the driver driving unit 30 and the on / off operation of the high-side switching devices AH and BH among the switching devices are normally controlled.

2, the driver driver 30 is shown in the form of a gate driver IC. However, the present invention is not limited to the illustrated IC, and the gate driver IC is operated by the operation power supplied through the power supply means.

The turn-on gate signal is input to the gate terminal of the high side switching device AH and BH by a power source charged in the driver driver 30 and the boot strap capacitors Ca and Cb, The side switching elements AH and BH are turned on and current is supplied to the motor 10. When the turn-on gate signal is inputted to the gate terminal of the high side switching device AH or BH, the driver driving part 30 turns off the gate terminal of the high side switching device AH or BH, ) Gate signal is applied to control the turn-on switching elements AL and BL to be off so that a normal current is supplied to the motor 10 side.

Therefore, motor driving starts when the high-side switching elements AH and BH are turned on and the high-side switching elements AH and BH and the high-side switching elements AL and BL alternately turn on the motor 10 in the direction of rotation.

The bootstrap capacitors Ca and Cb for controlling on / off of the high side switching elements AH and BH are not sufficiently charged at the time of initial driving, Since the high gate signal of the high voltage (AH, BH) is not normally applied and the gate driver error signal is generated, in the electric type steering apparatus according to the embodiment of the present invention, The devices AL and BL are turned on so that the bootstrap capacitors Ca and Cb are sufficiently charged and then the high side switching devices AH and BH are turned on.

Accordingly, the bootstrap charge controller of the drive controller 40 may control the bootstrap capacitors Ca and Cb to be charged when the supply voltage supplied through the power supply unit is equal to or less than a preset drive voltage, And generates a control signal for controlling the switching elements AH, BH, AL, and BL, and transmits the control signal to the driver driving unit 30.

2, the bootstrap capacitors Ca and Cb are connected at one end to the power supply side of the gate driver IC and at the other end to the source terminal of the high side switching element AH and BH When the device is an NMOS FET). Therefore, in an embodiment of the present invention, when the high side switching elements AH and BH are turned off and the low side switching elements AL and BL are turned on, current flows to the high side switching elements AH and BH Current paths are formed in the supply power source side, the bootstrap capacitors Ca and Cb and the switch elements AL and BL of the gate driver IC so that the bootstrap capacitors Ca and Cb are charged.

Therefore, the bootstrap charge control unit controls the turn-off control signal for controlling the high-side switching elements AH and BH to be turned off so that the bootstrap capacitors Ca and Cb are charged for a predetermined capacitor charge time, On control signals for controlling the turn-on and turn-on of the switch elements AL and BL, respectively, and the generated turn-off control signal and turn-on control signal are transmitted to the driver driver and applied to the corresponding switching elements .

The capacitor charging time may be set to a time required for the bootstrap capacitors Ca and Cb to be fully charged. Specifically, the capacity of the bootstrap capacitors Ca and Cb and the capacitances of the bootstrap capacitors Ca and Cb . In an embodiment of the present invention, when the bootstrap capacitor has a capacity of 470 nF, the capacitor charge time may be set to 1 ms. However, as described above, But is not limited to 1 ms.

When the capacitor charging time has elapsed, the bootstrap charge control unit turns on a turn-on control signal for controlling the high-side switching devices AH and BH to be turned on and the turn-on switching devices AL and BL turn off Off control signal to the driver driver 30, and the transferred control signal is applied to the gate terminal of the corresponding switching device in the form of a gate signal.

3 is a view illustrating a control method of an electric power steering apparatus according to an embodiment of the present invention.

Referring to FIG. 3, a control method of an electric power steering apparatus according to an embodiment of the present invention includes a step of, when power is supplied from a power supply unit, a voltage for comparing a supply voltage value supplied from the power supply unit with a preset drive voltage value A bootstrap execution step (S120) of generating a control signal such that the bootstrap capacitor is charged when the supply voltage value is equal to or lower than the drive voltage value, and a bootstrap execution step (S120) (S130, S140) for driving the motor of the electric power steering apparatus.

In the voltage comparison step (S110), when the supply voltage value is equal to or higher than the drive voltage value, it is determined that the motor can be normally driven, a maximum current value that can be supplied to the motor is set, do.

In addition, the voltage comparison step (S110) may include a step of comparing the supply voltage value with a preset reference voltage value for a predetermined period of time, determining that there is an abnormality in the supply voltage supplied from the power supply means, So that a signal can be generated.

FIG. 4 is a graph illustrating a control method of an electric steering apparatus according to an embodiment of the present invention. FIG. 4A is a signal indicating a charging voltage charged in a bootstrap capacitor, FIG. (C) is a signal indicating the supply voltage, and (d) the signal is an error detection signal of the driver driver.

4, when a high gate signal is applied to the gate terminal of the switch element during the initial driving (T1) in which the supply voltage value is equal to or lower than the driving voltage value in the electric steering system according to the embodiment of the present invention, The switching element is turned on, and the bootstrap capacitor is charged.

After a predetermined time has elapsed (T2), when the supply voltage value becomes equal to or higher than the drive voltage value and a low gate signal is applied to the gate terminal of the switch element, the switch element is turned off, During the time (T2-T1, capacitor charging time), the voltage charged in the bootstrap capacitor is raised to the high gate signal applied to the gate terminal of the high-side switching element, so that the high-side switching element is normally turned on, As the element is turned on, current is supplied to the motor and driving of the motor is started.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as defined by the appended claims. The embodiments of the present invention are not intended to limit the scope of the present invention but to limit the scope of the present invention.

10: motor 20: inverter section
50: power supply means 120: bootstrap charge control unit

Claims

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In an electric steering system,
Bridge circuit composed of two high side switching devices and two low side switching devices and one end connected to the power source side and the other end connected to the two high side switching devices An inverter unit including two bootstrap capacitors Ca and Cb connected to a source terminal, and controlling driving of the motor with a plurality of switching elements turned on / off;
A voltage ratio supply unit for comparing a supply voltage value supplied from the power supply unit with a predetermined drive voltage value; And
Side switching element and the low-side switching element so that the bootstrap capacitor is charged when the supply voltage value is equal to or less than a predetermined drive voltage value, and generates a control signal for driving the high- To the bootstrap charge control section
.

5. The method of claim 4,
The bootstrap charge control unit includes:
A turn-off control signal for controlling the high-side switching element to be turned off during a predetermined capacitor charge time, and a turn-off control signal for turning on the low- On control signals for controlling the switching elements so as to be applied to the respective switching elements.

6. The method of claim 5,
The bootstrap charge control unit includes:
Off control signal for controlling the high-side switching element to be turned on when the capacitor charging time has elapsed, and a turn-off control signal for controlling the turn-on switching element to be turned off so as to be applied to each switching element So that a normal current is supplied to the motor.