KR20070096361A - Method for compensating direct current offset of current sensor and electronic control unit therefor - Google Patents

Abstract

A method for compensating DC(Direct Current) offset in a current sensor and an ECU therefor are provided to minimize torque ripples of a supply current supplied to a motor by compensating a DC offset value. An ECU(Electronic Control Unit)(120) includes an inverter(140), current sensors(150,160), and an MCU(Motor Control Unit)(130). The inverter delivers a supplying current to a motor(170). The current sensors detect the supplying current and deliver the detected supplying current. The MCU receives torque data from a torque sensor(110), calculates a control current based on the torque data, controls the inverter to supply the supplying current, calculates a DC offset value in the current sensors, and compensates for the calculated DC offset value.

Description

Method for Compensating Direct Current Offset of Current Sensor and Electronic Control Unit Therefor}

1 is a block diagram schematically illustrating an ECU for DC offset compensation of a current sensor according to a preferred embodiment of the present invention.

2 is a flowchart illustrating a DC offset compensation method of a current sensor according to a preferred embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

110: torque sensor 120: ECU

130: MCU 140: Inverter

150: a-phase current sensor 160: b-phase current sensor

170: motor

The present invention relates to a DC offset compensation method of a current sensor (hereinafter referred to as "DC offset") and an electronic control unit (ECU) for it. More specifically, the present invention relates to a method of minimizing torque ripple of a motor by measuring and offsetting a DC offset of a current sensor that senses a current flowing in a motor in an ECU of an automobile in real time, and an electronic control apparatus therefor.

Normally, a hydraulic power steering device (Hydraulic Power Steering Apparatus) using the hydraulic pressure of a hydraulic pump is used as a steering device of an automobile, but since the 1990s, an electric power steering device (EPS: Electronic Power Steering Apparatus) has gradually become more common. have. Conventional hydraulic power steering system uses a hydraulic pump, which is the power source to assist the power, is driven by the engine and consumes energy all the time regardless of whether the steering wheel is rotated, whereas the electric steering system generates torque when the steering wheel rotates. A motor driven by electrical energy provides steering assistance power. Therefore, when the electric steering device is used, energy efficiency can be improved compared to the hydraulic power steering device.

In general, the electric steering device uses the generated torque, vehicle speed, steering angle, etc. to grasp the driver's steering intention and the driving condition of the vehicle, and generates steering assistance by comprehensively considering the steering column, rack bar, rack and pinion, etc. This makes it easier for the driver to drive and makes the car run safer.

Electric steering is made up of many mechanical and electronic components, but the most important configuration is the ECU. ECU is the core device of the electric steering device that analyzes the electric signals transmitted from various external sensors to understand the driver's steering intention and the driving situation of the car, and controls the motor using various logics provided. .

In general, the ECU detects the current flowing in the motor to precisely control the motor, and uses the current sensor to determine the current flowing in the motor. That is, if the motor uses a three-phase power source, a current sensor is attached to two phases of three phases (for example, a phase, b phase, and c phase a and b phases) to measure and measure the current of each phase. The current of each phase is used to calculate the current of the other phase.

The ECU calculates ripple, that is, torque ripple, according to the torque generated in the motor and the torque using the current of each phase measured as described above. Torque ripple is caused by an error in the path that delivers the current detected by the current sensor, an error in the applied voltage applied to the current sensor, or a DC offset of the current sensor itself. have.

Here, the DC offset is a small amount of DC current for operating the current sensor. When measuring the current flowing to the motor from the current sensor, a small amount of current required to operate the current sensor flows, and the current output from the current sensor is actually a small amount of current flowing to the motor to be obtained and a required amount to operate the current sensor. Is the sum of the currents. At this time, the value of the current flowing through the actual motor to be measured is distorted due to a small amount of current. Since these DC offsets are absolutely necessary to measure the current through the motor, they cannot be completely removed, so the DC offset must be taken into account when measuring the current through the motor.

Therefore, in order for the ECU to control the motor precisely, torque ripple must be minimized by compensating for the DC offset generated by the current sensor. In addition, since the DC offset generated by the current sensor fluctuates continuously due to the surrounding environment and the aging of the current sensor in the process of controlling the motor, the development of a technology that properly compensates for the DC offset in the process of controlling the motor by the ECU Is required.

In order to solve this problem and meet the needs thereof, the present invention provides a method and method for minimizing torque ripple of a motor by measuring and compensating in real time the DC offset of a current sensor that senses a current flowing in a motor in an automotive ECU. The purpose is to provide an electronic control device.

In order to achieve the above object, the present invention provides an electronic control unit (ECU) for controlling a motor by detecting a generated torque from a torque sensor, comprising: an inverter for transmitting a supply current to the motor; A current sensor for detecting and delivering a supply current; And a motor control unit (MCU) that receives the generated torque from the torque sensor, calculates a control current according to the generated torque, controls the inverter to supply the supply current, and calculates and compensates a DC offset of the current sensor. It provides an electronic control device for the DC offset compensation of the current sensor, characterized in that it comprises a 'MCU'.

In addition, according to another object of the present invention, in a method of compensating for the DC offset of the current sensor in the electronic control unit (ECU) for controlling the motor by detecting the generated torque from the torque sensor, (a) of the motor Checking whether the current control is stopped and measuring a supply current supplied to the motor using a current sensor; (b) calculating and storing the DC offset of the current sensor using the supply current; And (c) checking whether or not the current control of the motor is performed to compensate for the DC offset to perform the current control.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

FIG. 1 is a block diagram schematically illustrating an electronic control unit (ECU) for DC offset compensation of a current sensor according to a preferred embodiment of the present invention.

ECU 120 for the DC offset compensation of the current sensor according to an embodiment of the present invention is connected to various sensors and the motor 170 to determine the driving situation, such as the torque sensor 110, the torque sensor 110 By analyzing the electric signal input from the) and the like to detect the driving situation by the driver, and outputs a supply current for controlling the drive torque of the motor 190 to suit the driving situation.

Here, in FIG. 1, the ECU 120 is illustrated as only connected to the torque sensor 110, but may be actually connected to a plurality of sensors for detecting a driving situation such as a vehicle speed sensor and a steering angle sensor. The motor 170 generates and transmits auxiliary power for smooth steering according to the supply current transmitted from the ECU 120.

In addition, the ECU 120 for the DC offset compensation of the current sensor according to an embodiment of the present invention is a motor control unit (MCU: Motor Control Unit, hereinafter referred to as 'MCU', 130), inverter (Inverter, 140), It includes a phase current sensor 150 and b phase current sensor 160.

The MCU 130 is connected to the torque sensor 110 to receive the electrical signal from the torque sensor 110 to determine the generated torque, calculate the control current according to the generated torque to control the inverter 140 by the inverter 140 To supply the supply current corresponding to the control current to the motor 170.

MCU 130 according to a preferred embodiment of the present invention to compensate in real time the DC offset of the a-phase current sensor 150 and the b-phase current sensor 160 attached to the connection between the inverter 140 and the motor 170 in real time By using an algorithm, the current value of phase a and current of phase b are measured using the current sensors 150 and 160 while the current control of the motor 170 is not performed. After calculating and storing the DC offset, when performing the current control of the motor 170, the supply current supplied to the motor is controlled in consideration of the DC offset stored in each phase. Here, the DC offset of each phase is a voltage obtained by subtracting the reference voltage from a voltage that is a product of the current value of each phase and the equivalent resistance value of the current sensor of each phase.

To this end, the MCU 130 calculates a control current according to the generated torque to control the inverter 140 and performs a calculation for compensating the DC offset, a software of an algorithm for calculating the control current according to the generated torque, and an inverter. Non-volatile memory, such as software of an algorithm for controlling 140, software of an algorithm to compensate for DC offset, and an electrically erased program ROM (EEPROM) for storing the DC offset of each phase calculated, the microprocessor is a non-volatile memory And a volatile memory such as RAM (Random Access Memory) for executing various software stored in and storing temporary data generated by calculation.

The inverter 140 converts a direct current into an alternating current and supplies power to the motor 170. The inverter 140 supplies a supply current to the motor 170 under the control of the MCU 130. That is, the inverter 140 controls the operation of the motor 170 by varying the supply current supplied to the motor 170 by switching the switching element provided according to the control current when the control current is transmitted from the MCU 130. . At this time, since the inverter 140 converts direct current into alternating current and supplies it to the motor 170, the inverter 140 supplies three-phase alternating current power to the motor 170.

The a-phase current sensor 150 and the b-phase current sensor 160 are attached to the a-phase and b-phase connection, respectively, of the three-phase connection between the inverter 140 and the motor 170, and detects the current value of each phase to determine the MCU ( 130 is a current sensor that feeds back.

Torque ripple generated from the supply current supplied to the motor 170 is generated according to the DC offset of the current sensor of each phase. Hereinafter, the relationship between the DC offset and the torque ripple of the current sensor will be described through Equations 1 to 3 below.

 The current in phase a is called ia, the current in phase b is ib, and the current in phase c is ic, and the DC offsets of the phases a and b are Δa and Δb respectively. Ia, ib, and ic are calculated as in Equation 1.

When the generated torque Te is calculated using the current of each phase calculated as in Equation 1, it is calculated as in Equation 2.

Here, when the torque ripple Tr is calculated using the generated torque, it is calculated as in Equation 3.

As shown in Equation 3, it can be seen that the torque ripple varies depending on the DC offset current Δa of the a-phase current sensor 150 and the DC offset current Δb of the b-phase current sensor 160. That is, it can be seen that the torque ripple rises in proportion to the DC offset current. Accordingly, the torque ripple of the supply current supplied to the motor 170 may be minimized by adjusting the a phase current sensor 150 and the b phase current sensor 160 to have a DC offset of '0'. In practice, due to implementation problems, it is impossible to adjust the a-phase current sensor 150 and the b-phase current sensor 160 so that the DC offset is '0', so this DC offset must be compensated when performing current control. do.

Hereinafter, a method of compensating for the DC offset of the current sensor by using the ECU 120 for the DC offset compensation of the current sensor described with reference to FIG. 1 will be described.

2 is a flowchart illustrating a DC offset compensation method of a current sensor according to a preferred embodiment of the present invention.

In order to compensate for the DC offset of the a-phase current sensor 150 and the b-phase current sensor 160, the ECU 120 checks whether the current control of the motor 170 is performed (S210). In order to measure the DC offset of the current sensors 150 and 160 of each phase, the current value of each phase should be measured when no current flows in the motor 170. That is, if the current control of the motor 170 is not performed, the current flowing in the motor 170 should be '0', and at this time, the output value of the current sensor should be '0', which is not '0' in the current sensor. When the current value is output, the voltage corresponding to the current value is the DC offset voltage. Therefore, the torque ripple may be reduced by compensating the DC offset voltage to be '0'. Therefore, when the ECU 120 does not control the current of the motor 170, the current must be measured using the current sensors 150 and 160 of each phase.

In this case, when the ECU 120 does not perform current control of the motor 170, for example, during an Ignition Start Initial Check, a fail-safety occurs, a power latch ( Power Latch) is occurring.

When the ECU 120 is controlling the current of the motor 170 as a result of checking in step S210, the ECU 120 repeatedly performs step S210 to wait until the current of the motor 170 is not controlled, If the current is not controlled, the current value of each phase is measured using the current sensors 150 and 160 of each phase (S220).

The ECU 120 measuring the current value of each phase calculates and stores a DC offset of each phase using the measured current value (S230). In detail, the ECU 120 determines the DC offset of a voltage obtained by subtracting the reference voltage of each phase from a voltage obtained by multiplying the current value of each phase by the internal equivalent resistance values of the current sensors 150 and 160. . That is, when the DC offset does not control the current of the motor 170, the measured current value is multiplied by the equivalent resistance value of the current sensor to calculate the value of the voltage drop generated in the current sensor, and the reference voltage is calculated from the value of the voltage drop. Calculated as the minus voltage.

Thus, for example, the current value of each phase, that is, the current value of the a phase is 10 A, the current value of the b phase is 1 A, and the equivalent resistance value of the current sensors 150 and 160 of each phase, that is, of the a phase current sensor 150. If the equivalent resistance value is 2.6 Ω and the equivalent resistance value of the b-phase current sensor 160 is 2.6 Ω, the DC offset of each phase is 1 AX 2.5 Ω = 0.1 V and the b phase 1 AX 2.5 Ω = 0.1 V for a phase. Is calculated. In addition, the ECU 120 stores in the memory having the DC offset of each phase calculated as described above.

The ECU 120 that calculates and stores the DC offset checks whether to start the current control of the motor 170 to compensate the calculated DC offset (S240). When the ECU 120 determines that the current of the motor 170 is not being controlled as a result of checking in step S240, the ECU 120 waits until current control is performed and starts the current control of the motor 170, that is, the motor 170. The DC offset rkqt stored in the memory is read while compensating for the current, and the read DC offset value is compensated to determine the current flowing through the motor 170 to minimize the torque ripple of the motor current supplied to the motor 170 ( S250).

Thus, when the ECU 120 is manufactured, the DC offset of each preset current sensor is changed due to the surrounding environment or the aging of the current sensor or other components, thereby changing the DC offset when the ECU 120 controls the motor 170. The occurrence of torque ripple in the supply current supplied to the motor 170 may not be reflected by compensating the DC offset in real time through an algorithm for compensating for the DC offset. That is, the ECU 120 may control the motor 170 more precisely by measuring and compensating the DC offset of each current sensor in real time even after the ECU 120 is manufactured.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

As described above, according to the present invention, even after the ECU is manufactured, by calculating and storing the DC offset of the current sensor for detecting the current supplied to the motor in real time, and compensating the DC offset calculated when controlling the current of the motor. In addition, the torque ripple of the supply current supplied to the motor can be minimized, so that the motor can be more precisely controlled.

Claims (4)

In the electronic control unit (ECU: Electronic Control Unit) for detecting the generated torque from the torque sensor to control the motor, An inverter transferring a supply current to the motor; A current sensor which senses and delivers the supply current; And The motor controller (MCU) for receiving the generated torque from the torque sensor, calculating a control current according to the generated torque to control the inverter to supply the supply current, and calculating and compensating a DC offset of the current sensor. : Motor Control Unit, hereinafter referred to as 'MCU') Electronic control device for the DC offset compensation of the current sensor comprising a. The method of claim 1, wherein the MCU, And the DC offset is calculated by measuring the supply current while the motor is not controlled. The method of claim 1, wherein the MCU, And calculating and storing the DC offset, and compensating for the DC offset while controlling the motor. In the method for compensating the DC offset of the current sensor in an electronic control unit (ECU) for controlling the motor by detecting the generated torque from the torque sensor, (a) checking whether the current control of the motor is stopped and measuring a supply current supplied to the motor by using the current sensor; (b) calculating and storing a DC offset of the current sensor using the supply current; And (c) checking whether the current control of the motor is performed to compensate the DC offset to perform the current control; DC offset compensation method of the current sensor comprising a.

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