High performance controller for shifting resonance in micro-electro-mechanical systems (MEMS) devices

• US 20030123046A1
• Filed: 12/09/2002
• Published: 07/03/2003
• Est. Priority Date: 12/12/2001
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Heaton, Mark W.
• Granted Patent: US 7,047,097 B2
• Time in Patent Office: Days
• US Class Current: 356/27
• CPC Class Codes: G05B 19/404 characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia G05B19/19, G05B19/41 take precedence
• CPC Class Codes: G05B 2219/41133 Compensation non linear transfer function
• CPC Class Codes: G05B 2219/41152 Adaptive filter

Abstract

Devices being controlled electronically via physical manipulation often display a resonance. In many circumstances, the frequency range of operation is not close to the resonance frequency. In these cases, the resonance can be removed through the use of simple compensation techniques such as filters. However, when the resonance frequency is close to the frequency range of operation and when the resonance frequency can change depending on temperature, time, and physical position of the device, simple compensation techniques cannot be used. The present invention presents a non-mechanical technique for providing compensation for devices with a shifting resonance. The non-mechanical technique allows for the compensation to be performed via computation.

Claims

1. A control method for a system with a shifting resonance point comprising:

issuing a command to manipulate a mechanical device;

detecting physical information of the mechanical device;

computing a compensation value based on the detected physical information;

combining the computed compensation with the command; and

manipulating the mechanical device based on the combined command.

2. The method of claim 1, wherein the physical information is position, velocity, or acceleration information of the mechanical device.

3. The method of claim 2, wherein the physical information is detected by a sensor.

4. The method of claim 1, wherein the issued command is issued by a processing unit.

5. The method of claim 4, wherein the issuing step comprises:

converting the issued command into an analog representation; and

converting the analog representation into a voltage value.

6. The method of claim 1, wherein the detecting step comprises:

using a sensor to detect the physical information of the mechanical device; and

converting a voltage value produced by the sensor into a digital equivalent.

7. The method of claim 1, wherein the computing step comprises:

filtering the detected physical information; and

producing the compensation value.

8. The method of claim 7, wherein the filtering is performed by a second order filter.

9. The method of claim 7, wherein the computing step is performed with analog signals.

10. The method of claim 7, wherein the computing step is performed with digital signals.

11. The method of claim 7, wherein the computing step further comprises:

producing an error signal;

filtering the error signal with a second filter;

differentiating the filtered error signal with a second differentiator; and

replacing the command with the differentiated and filtered error signal.

12. The method of claim 11, wherein the filtering is performed by a third order filter.

13. The method of claim 11, wherein the error signal is a difference between the command and the detected position.

14. The method of claim 1, wherein the combining step comprises adding the compensation value generated in the computing step with the command.

15. The method of claim 14, wherein the adding is binary arithmetic.

16. The method of claim 1, wherein the generating step uses the same steps for generating the new command as it did for generating the initial command.

17. The method of claim 1, wherein the mechanical device is a micromirror in a micro-electrical-mechanical system (MEMS).

18. The method of claim 1, wherein the physical information is position information of the mechanical device, and the computing step comprises:

filtering the detected position;

differentiating the filtered position data; and

producing the compensation value.

19. The method of claim 18, wherein the computing step further comprises:

producing an error signal;

filtering the error signal with a second filter;

differentiating the filtered error signal with a second differentiator; and

replacing the command with the differentiated and filtered error signal.

20. A circuit for controlling a system with a shifting resonance comprising:

a processor, the processor containing circuitry to issue commands for controlling the functionality of the system;

an actuator coupled to the processor, the actuator containing circuitry to respond to the commands issued by the processor;

a physical device coupled to the actuator;

a sensor coupled to the physical device and the processor, the sensor containing circuitry to detect physical information regarding the physical device and forwarding the detected physical information to the processor;

a differentiator coupled to the sensor, the differentiator containing circuitry to differentiate and filter signals provided by the sensor; and

a damping-scaling unit coupled to the differentiator, the damping-scaling unit containing circuitry to ensure that signals from the differentiator does not exceed a permitted range of signals and to provide an additional damping factor to the signal to rapidly control the physical device.

21. The circuit of claim 20, wherein the physical device is a micromirror.

22. The circuit of claim 21, wherein the sensor is a positional sensor and senses the position of the micromirror.

23. The circuit of claim 21, wherein the sensor is a velocity sensor and senses the velocity of the micromirror.

24. The circuit of claim 21, wherein the sensor is an acceleration sensor and senses the acceleration of the micromirror.

25. The circuit of claim 20, wherein the differentiator and the damping-scaling unit are analog circuits and operate on analog voltage values generated by the sensor.

26. The circuit of claim 20, wherein the circuit further comprising:

a digital-to-analog converter coupled to the processor and the actuator, the digital-to-analog converter containing circuitry to convert digital commands to an analog equivalent that can be applied to the actuator; and

an analog-to-digital converter coupled to the sensor and the differentiator, the analog-to-digital converter containing circuitry to convert the voltage levels generated by the sensor into a digital equivalent that is usable by the processor.

27. The circuit of claim 26, wherein the differentiator and the damping-scaling unit are functional units in the processor.