Motor drive apparatus, electric actuator and electric power steering apparatus

• US 7,161,323 B2
• Filed: 06/22/2005
• Issued: 01/09/2007
• Est. Priority Date: 06/30/2004
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Kaneko, Satoru, Miyazaki, Hideki, Ajima, Toshiyuki, Takamune, Yuuichirou
• Primary Examiner(s): Donovan; Lincoln
• Assistant Examiner(s): COLON SANTANA, EDUARDO
• Application Number:
  US11/158,247
• Publication Number:
  US 20060001392A1
• Time in Patent Office: 566 Days
• Field of Search: None
• US Class Current: 318/629
• CPC Class Codes: B62D 5/046 Controlling the motor
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: F16D 2121/24 using motors
• CPC Class Codes: F16D 65/18 adapted for drawing members together , e.g. for disc brakes
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02P 2209/07 Trapezoidal waveform
• CPC Class Codes: H02P 6/10 Arrangements for controlling torque ripple, e.g. providing reduced torque ripple

Abstract

The disclosure concerns a a motor drive apparatus, an electric actuator and an electric power steering apparatus capable of continuous torque control up to the high drive speed and high torque area, in order to enable quick acceleration and deceleration. A controller comprises a voltage saturation detecting apparatus for detecting the voltage saturation of the output voltage of an inverter circuit, based on the battery voltage, and a waveform controller that converts the drive waveform of the inverter circuit into the waveform created by superimposing harmonics of high odd-numbered order on a sinusoidal wave as a fundamental wave of the modulated wave modulated by a PWN carrier wave; and continuously changes the ratio of superimposing the high-order harmonics in response to the voltage saturation detected by a voltage saturation detecting means. This arrangement allows the controller to continuously change the drive waveform of the inverter circuit.

Claims

1. A motor drive apparatus comprising:

a 3-phase a.c. driven motor;

an inverter for driving said motor based on a battery voltage;

a first current detector for detecting a direct current flowing to said inverter;

a plurality of second current detectors for detecting the motor current flowing to said motor; and

a controller for controlling the drive of said inverter based on the current value detected by said first and/or second current detectors, and for driving the motor while controlling the torque of said motor;

wherein said controller converts the drive waveform of said inverter into the waveform created by superimposing harmonics of high odd-numbered order on a sinusoidal wave as a fundamental wave of the modulated wave modulated by a PWM carrier wave; and

continuously changes the ratio of superimposing said high-order harmonics, based on said battery voltage.

2. The motor drive apparatus described in claim 1 wherein said controller comprises:

a voltage saturation detecting unit for detecting the saturation of said inverter output voltage based on said battery voltage; and

a waveform control unit for converting the drive waveform of said inverter into the waveform created by superimposing harmonics of high odd-numbered order on a sinusoidal wave as a fundamental wave of the modulated wave modulated by a PWM carrier wave; and

for continuously changing the ratio of superimposing said high-order harmonics, in response to the degree of voltage saturation measured by said voltage saturation detecting unit.

3. The motor drive apparatus described in claim 1, further characterized in that said controller comprises:

a step of obtaining the voltage command value from the deference between a current command value based on a torque command value and the current value detected by said first and/or second current detectors;

a step of calculating a superimpose ratio based on the voltage of said battery as a parameter; and

a step of superimposing the high odd-numbered order harmonics on the fundamental sinusoidal wave in accordance with said superimpose ratio.

4. The motor drive apparatus described in claim 1, further comprising a rotating position detector for detecting the rotating position of said motor, wherein said controller comprises:

a step of controlling the motor current based on the vector control according to the torque current command (q-axis current command) and exciting current command (d-axis current command); and

a step of controlling said motor current based on the rotating position of the rotor detected by said rotating position detector.

5. The motor drive apparatus described in claim 1, further characterized in that said controller comprises a current correcting unit, wherein said controller comprises:

a step of comparing the direct current value detected by said first current detector with the motor current detected by said second current detectors;

a step of detecting the detection error level of said current detector; and

a step of obtaining the motor current value of the faulty phase, using the motor currents of other two phases, if the detection error range for the motor current value of any one phase in the three-phase motor current values is narrower than a predetermined electrical angle.

6. The motor drive apparatus described in claim 5, wherein, if the detection error range for the motor current value of at least one phase in the three-phase motor current values is greater than a predetermined electrical angle, said current correcting unit estimates the motor current value of the faulty phase using the motor currents of other phases and said direct current values.

7. The motor drive apparatus described in claim 5, wherein said waveform control unit converts the drive waveform into a 120-degree rectangular wave if a detection error level has been detected to be within the range involving difficulties in detecting all the motor current values at the same time.

8. The motor drive apparatus described in claim 5, further characterized in that said current correcting unit compares said direct current instantaneous value with said motor current value at intervals of 60-degree period in terms of motor electrical angle, and detects the detection error level, wherein the direct current value whose resolution is equivalent to or higher than the resolution of said motor current value is used as an input;

and the peak value within the PWM period of said direct current value having been detected is held as the direct current instantaneous value.

9. A motor drive apparatus comprising:

a 3-phase a.c. driven motor;

an inverter for driving said motor based on a battery voltage;

a first current detector for detecting a direct current flowing to said inverter;

a plurality of second current detectors for detecting the motor current flowing to said motor; and

a controller for controlling said inverter by PWM based on the current value detected by said first andior second current detectors, and for driving the motor while controlling the torque of said motor;

wherein said controller comprises;

a step of comparing a PWM pulse width of each chase with a predetermined value; and

a step of obtaining the motor current of the chase whose PWM pulse width is wider than the predetermined value based on the motor current of at least one of other phases and the direct current if the PWM pulse width of the phase is wider than the predetermined value.

10. An electric actuator comprising:

a 3-phase a.c. driven motor;

an inverter for driving said motor based on a battery voltage;

a first current detector for detecting a direct current flowing to said inverter;

a plurality of second current detectors for detecting the motor current flowing to said motor;

a controller for controlling the drive of said inverter based on the current value detected by said first and/or second current detectors, and for driving the motor while controlling the torque of said motor; and

a torque transmitter for transmitting the drive torque of said motor to a driven member;

wherein said controller converts the drive waveform of said inverter into the waveform created by superimposing harmonics of high odd-numbered order on a sinusoidal wave as a fundamental wave of the modulated wave modulated by a PWM carrier wave; and

continuously changes the ratio of superimposing said high-order harmonics, based on said battery voltage.

11. An electric power steering apparatus comprising the electric actuator described in claim 10.