SELF-CALIBRATION ALGORITHMS IN A SMALL MOTOR DRIVER IC WITH AN INTEGRATED POSITION SENSOR

• US 20090224716A1
• Filed: 06/16/2008
• Published: 09/10/2009
• Est. Priority Date: 03/06/2008
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Haas, David J., Doogue, Michael C., Milano, Shaun D., David, Paul, Vig, Ravi
• Granted Patent: US 7,936,144 B2
• Time in Patent Office: Days
• US Class Current: 318/550
• CPC Class Codes: G05B 19/19 characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
• CPC Class Codes: G05B 2219/41099 Calibration by going to two extremes, limits, counting pulses, storing values
• CPC Class Codes: G05B 2219/41337 Linear drive motor, voice coil
• CPC Class Codes: G05B 2219/42152 Learn, self, auto tuning, calibrating, environment adaptation, repetition
• CPC Class Codes: G05B 2219/45178 Zoom, focus lens
• CPC Class Codes: H02P 25/034 Voice coil motors voice coil motors driven by DC power H02P7/025

Abstract

A motion control device for controlling a motor is presented. The motion control device is operable to scale or adjust an input relative to an input range that is based on calibration values and to use that scaled input to produce a drive signal to drive the motor. The motion control device performs a self-calibration to produce the calibration values. The self-calibration involves measuring home position and full travel position values for the motor.

Claims

1. A device for controlling a motor, comprising:

a driver and a sensor;

first circuitry, coupled to the driver and sensor, to control the driver and sensor to produce calibration information for the motor;

second circuitry, coupled to the first circuitry, to adjust an input relative to an input range that is based on the calibration information; and

wherein the adjusted input is usable to produce a drive signal to drive the motor.

2. The device of claim 1 wherein the calibration information comprises a first calibration value corresponding to a start-of-travel position value output by the sensor when the driver provides no current to the motor and a second calibration value corresponding to an end-of-travel position value output by the sensor when the driver provides to the motor a current capable of producing a maximum position change.

3. The device of claim 2 wherein the second circuitry comprises an input interface to receive an input request as the input and the first circuitry comprises a calibration control block that provides the first and second calibration values to the input interface.

4. The device of claim 3 wherein the input request comprises a digital value, and wherein the input interface comprises a digital-to-analog converter (DAC) having a first reference terminal to receive the first calibration value as a first reference and a second reference terminal to receive the second calibration value as a second reference, the first and second references defining the input range.

5. The device of claim 3 wherein the input request comprises an analog signal, and wherein the input interface comprises an operational amplifier having gain circuitry adjustable to set a gain value based on the first and second calibration values, and offset circuitry adjustable to set an offset value equal to the first calibration value, wherein the gain and offset values define the input range.

6. The device of claim 3 wherein the input request comprises a pulse width modulated signal and wherein the input interface further comprises an integrator to translate the pulse width modulated signal to an analog signal.

7. The device of claim 2 wherein the second circuitry comprises circuitry to receive an output from the sensor as the input, and the first circuitry comprises a calibration control block that provides the first and second calibration values to the circuitry.

8. The device of claim 7 wherein the circuitry comprises an operational amplifier having gain circuitry adjustable to set a gain value based on the first and second calibration values, and offset circuitry adjustable to set an offset value equal to the first calibration value, wherein the gain and offset values define the input range.

9. The device of claim 7 wherein the circuitry comprises an analog-to-digital converter (ADC) having a first reference terminal to receive the first calibration value as a first reference and a second reference terminal to receive the second calibration value as a second reference, the first and second references defining the input range.

10. The device of claim 1 wherein the driver comprises a voice coil driver and the sensor comprises a magnetic field sensor.

11. The device of claim 1 wherein the calibration information is produced when the first circuitry detects a power on cycle.

12. A system comprising:

a controller; and

a motion control device, coupled to the controller and a voice coil motor (VCM), comprising;

a voice coil driver and a magnetic field sensor;

first circuitry, coupled to the voice coil driver and the magnetic field sensor, to control the voice coil driver and magnetic field sensor to produce calibration information for the VCM;

second circuitry, coupled to the first circuitry, to adjust an input relative to an input range that is based on the calibration information; and

wherein the adjusted input is usable to produce a drive signal to drive the VCM.

13. The system of claim 12 wherein the calibration information comprises a first calibration value corresponding to a start-of-travel position value output by the magnetic field sensor when the voice coil driver provides no current to the VCM and a second calibration value corresponding to an end-of-travel position value output by the magnetic field sensor when the voice coil driver provides to the VCM a current capable of producing a maximum position change.

14. The system of claim 13 wherein the second circuitry comprises an input interface to receive an input request as the input and the first circuitry comprises a calibration control block that provides the first and second calibration values to the input interface.

15. The system of claim 14 wherein the input request comprises a digital value, and wherein the input interface comprises a digital-to-analog converter (DAC) having a first reference terminal to receive the first calibration value as a first reference and a second reference terminal to receive the second calibration value as a second reference, the first and second references defining the input range.

16. The system of claim 14 wherein the input request comprises an analog signal, and wherein the input interface comprises an operational amplifier having gain circuitry adjustable to set a gain value based on the first and second calibration values, and offset circuitry adjustable to set an offset value equal to the first calibration value, wherein the gain and offset values define the input range.

17. The system of claim 12 wherein the controller is configured to use the motion control device to focus the lens of a camera.

18. The system of claim 12 wherein the voice coil driver, the magnetic field sensor, the first circuitry and the second circuitry are integrated as a semiconductor integrated circuit.

19. The system of claim 18 wherein the semiconductor integrated circuit and the controller reside on a camera lens focusing module.

20. A method of controlling a motor, comprising:

controlling a driver and sensor to produce calibration information for the motor;

adjusting an input relative to an input range that is based on the calibration information; and

using the adjusted input to produce a drive signal to drive the motor.

21. The method of claim 20, wherein the calibration information comprises a first calibration value and a second calibration value, and wherein controlling comprises:

controlling the sensor to measure as the first calibration value a start-of-travel position value produced when the driver provides no current to the motor; and

controlling the sensor to measure as the second calibration value an end-of-travel position value produced when the driver provides to the motor a current capable of producing a maximum position change.