MOTOR CONTROL DEVICE AND ELECTRIC POWER STEERING SYSTEM

• US 20120118662A1
• Filed: 03/10/2010
• Published: 05/17/2012
• Est. Priority Date: 03/17/2009
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Inventors: Sakai, Atsuo, Matsumoto, Tsutomu, Suzuki, Kazushi
• Granted Patent: US 8,890,459 B2
• Time in Patent Office: Days
• US Class Current: 180/443
• CPC Class Codes: B62D 5/046 Controlling the motor
• CPC Class Codes: B62D 5/0481 monitoring the steering system, e.g. failures
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 7/5395 by pulse-width modulation
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: H02P 6/28 Arrangements for controlling current H02P6/10 takes precedence

Abstract

A motor control device with which both high-accuracy current detection and improvement in voltage utilization factor are achieved is provided. When an ON time of any one of low potential side switching elements corresponding to respective phases in a driving circuit is shorter than a detection time of a current value, a microcomputer estimates a phase current value of a current undetectable phase based on current values of two phases other than the current undetectable phase corresponding to the said FET. Then, at the time of current detection using the blind correction, during current detection for two phases, other than the current undetectable phase, based on which the blind correction is performed, motor control signals for maintaining switching states of a switching arm corresponding to the current undetectable phase are output.

Claims

1. A motor control device, comprising:

control signal output device that outputs motor control signals; and

a driving circuit that outputs three-phase driving electric power based on the motor control signals, wherein

the driving circuit is formed by connecting switching arms, formed by serially connecting pairs of switching elements that are turned on or off based on the motor control signals, in correspondence with respective phases, in parallel with one another,

the switching arms respectively have current sensors for detecting phase current values of the respective phases corresponding to the switching arms at low potential sides thereof,

the control signal output device generates the motor control signals based on phase current values of the respective phases, detected at a timing at which all low potential side switching elements of the respective switching arms are turned ON,

when an ON time of any one of the low potential side switching elements is shorter than a detection time of the current value, the control signal output device estimates a phase current value of a current undetectable phase based on phase current values of two phases other than the current undetectable phase corresponding to the said switching element, and

at the time of current detection of the two phases, the motor control signals for maintaining switching states of the switching arm corresponding to the current undetectable phase are output.

2. The motor control device according to claim 1, wherein

the control signal output device executes current feedback control based on detected phase current values of the respective phases to thereby compute voltage command values of the respective phases,

the control signal output device generates the motor control signals based on a comparison between duty command values corresponding to the respective voltage command values and a triangular wave, and

the motor control signals for maintaining switching states of the switching arm corresponding to the current undetectable phase are output by shifting the duty command values of the respective phases toward a high potential side such that the duty command value of the current undetectable phase becomes a value at which the high potential side switching element corresponding to the current undetectable phase is kept ON.

3. The motor control device according to claim 1, wherein

the control signal output device generates the motor control signals in order to perform pseudo third harmonic superimposed sinusoidal wave conduction.

4. The motor control device according to claim 2, wherein

the control signal output device generates the motor control signals in order to perform pseudo third harmonic superimposed sinusoidal wave conduction.

5. The motor control device according to claim 1, wherein

the control signal output device generates the motor control signals in order to perform sinusoidal wave conduction.

6. The motor control device according to claim 2, wherein

the control signal output device generates the motor control signals in order to perform sinusoidal wave conduction.

7. An electric power steering system comprising the motor control device according to claim 1.

8. An electric power steering system comprising the motor control device according to claim 2.

9. An electric power steering system comprising the motor control device according to claim 3.

10. An electric power steering system comprising the motor control device according to claim 4.

11. An electric power steering system comprising the motor control device according to claim 5.

12. An electric power steering system comprising the motor control device according to claim 6.