Multi-segment linearization of micro-actuator transfer functions

• US 8,457,794 B2
• Filed: 12/22/2009
• Issued: 06/04/2013
• Est. Priority Date: 08/25/2009
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Jimenez, Christian, Calpe-Maravilla, Javier, English, Eoin, Ibaez-Climent, Jos
• Primary Examiner(s): Padmanabhan, Kavita
• Assistant Examiner(s): DUNN, DARRIN D
• Application Number:
  US12/645,047
• Publication Number:
  US 20110054695A1
• Time in Patent Office: 1,260 Days
• Field of Search: 700/275, 702/86, 340/870.05, 340/686.1, 341/118, 341/140, 360/294.4
• US Class Current: 700/275
• CPC Class Codes: G05B 19/042 using digital processors G05B19/05 takes precedence
• CPC Class Codes: G05B 2219/2651 Camera, photo
• CPC Class Codes: G05B 2219/41415 Lookup table for nonlinear function synthesis
• CPC Class Codes: G05B 2219/42007 Nonlinear PD

Abstract

Embodiments of the present invention provide improved accuracy of displacement control by using a multi-segment transformation of an actuator'"'"'s non-linear response. The present invention may set intermediate points to effectively divide the actuator response into multiple segments. Each segment may be assigned a transform function that represents the actuator'"'"'s response in that particular segment. The present invention may operate in two modes, a calibration mode and a normal operations mode. During calibration mode, the intermediate points and the segment transforms may be set. During normal operations mode, a drive signal may be generated according to the calibrated set values.

Claims

1. An open-loop control system, comprising:

a plurality of code registers to store input code values for predetermined points of an actuator response, wherein the predetermined points divide the actuator response into multiple segments;

a transform block to store transform functions with respective coefficients assigned to the multiple segments; and

an accumulator, coupled to the code registers and the transform block, to generate an output control signal in the open-loop control system based on matching an input request to a segment of the actuator response and using the assigned transform function'"'"'s respective coefficient for the matched segment.

2. The control system of claim 1, further comprising a sensor coupled to the code registers and actuator.

3. The control system of claim 2, wherein the sensor is a resistive, capacitive, inductive, or photoelectric measurement system.

4. The control system of claim 2, wherein the sensor is a direct measurement system.

5. The control system of claim 2, wherein the sensor includes a temperature sensor.

6. The control system of claim 2, wherein the sensor includes an orientation sensor.

7. The control system of claim 1, further comprising a comparator block coupled to the code registers.

8. The control system of claim 7, wherein the comparator block includes a plurality of comparators, each comparator having one input coupled to an accumulator input and at least another input coupled to one of the plurality of code registers.

9. The control system of claim 1, further comprising a digital to analog converter coupled to the accumulator.

10. A method, comprising:

setting a code value for a minimum displacement voltage point of an actuator response;

setting a code value for a maximum displacement voltage point of the actuator response;

setting a code value for at least one intermediate point between the minimum displacement voltage point and the maximum displacement voltage point, wherein the at least one intermediate point divide the actuator response into multiple segments;

assigning a transform function with at least one respective coefficient for each segment;

storing code values and transform function assignments; and

operating the actuator in an open-loop control system using the stored code values by matching an input request to a segment of the actuator response and generating an output drive signal using the assigned transform function'"'"'s respective coefficient for the matched segment.

11. The method of claim 10, wherein setting the code values comprises measuring the actuator displacement.

12. The method of claim 11, wherein measuring comprises measuring the capacitance between a moving surface and a set reference.

13. The method of claim 10, wherein the transform function is a linear transform function.

14. The method of claim 10, wherein the transform function is a square root transform function.

15. A method comprising:

receiving an input request to move a mechanical system;

converting the input request into an input code;

comparing the input code to segment endpoints of an actuator response, wherein each segment of the actuator response has an assigned transform function with at least one respective coefficient;

based on the comparison, determining a segment in which the input code fits;

applying the determined segment'"'"'s assigned transform function using the transform'"'"'s respective coefficient to the input code; and

generating an output signal from the applied transform function code.

16. The method of claim 15, wherein the transform function is a linear transform function.

17. The method of claim 15, wherein the transform function is a quadratic function.