ELECTRONIC MOTOR CONTROLLER

• US 20090021205A1
• Filed: 09/03/2008
• Published: 01/22/2009
• Est. Priority Date: 01/14/2003
• Status: Active Grant

• Current Assignee: Christopher P. Cullen
• Original Assignee: Christopher P. Cullen
• Inventors: Cullen, Christopher P.
• Granted Patent: US 7,606,624 B2
• Time in Patent Office: Days
• US Class Current: 318/561
• CPC Class Codes: G05B 17/02 electric
• CPC Class Codes: H02P 2209/07 Trapezoidal waveform
• CPC Class Codes: H02P 23/14 Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage
• CPC Class Codes: H02P 6/16 Circuit arrangements for detecting position

Abstract

A control system for any type of electric motor that automatically learns the characteristics of the motor and computes a motor model for the motor. The control system uses the computed motor model to produce a closed-loop control design that achieves a particular resolution. The control system also uses the motor model to automatically construct efficient motion profiles for a variety of motion commands. The control system may also include an encoder interface device that provides highly accurate motor position information.

Claims

1. A method for determining a plurality of gains associated with a plurality of variables of a closed-loop controller, the method comprising the computer-implemented steps of:

assigning a gain associated with one of the controller variables to a desired resolution value;

calculating a frequency value for the gain set to the desired resolution value;

computing the remaining gains of the controller; and

supplying the computed gains to the closed-loop controller.

2. The method of claim 1, wherein the closed-loop controller comprises a proportional-integral-derivative controller and the assigned gain comprises a proportional gain.

3. The method of claim 2, further comprising:

assigning a plurality of proportional gains of the closed-loop controller to the desired resolution value;

calculating a frequency value for each proportional gain set to the desired resolution value;

selecting the smallest frequency value calculated; and

using the selected frequency value, computing the remaining gains of the controller.

4. The method of claim 2, wherein the closed-loop controller has a predetermined servo sampling rate and computing the remaining gains of the controller comprises:

computing an integral gain;

determining a second resolution value of the controller using the computed integral gain and current servo sampling rate; and

if the second resolution value is greater than the desired resolution value, then adjusting the servo sampling rate to reduce the second resolution value to at or below the desired resolution value.

5. The method of claim 2, wherein computing the remaining gains for the controller comprises:

determining the number of position error readings required as input in a boxcar derivative function in order to achieve a desired resolution.

6. The method of claim 1, wherein the closed-loop controller is a state space controller.

7. A method for designing a closed-loop controller having a state variable and a gain associated the state variable, the method comprising the computer-implemented steps of:

selecting a desired resolution value for the state variable; and

computing a gain associated with the state variable that achieves the desired resolution.

8. The method of claim 7, wherein the closed-loop controller has a plurality of state variables and a gain associated with each state variable, the method further comprising:

selecting a desired resolution value for each state variable; and

computing a gain associated with each state variable that achieves the desired resolution for that state variable.

9. The method of claim 8, wherein computing a gain associated with each state variable that achieves the desired resolution for that state variable comprises:

calculating a frequency value for two or more gains set to the desired resolution value;

selecting the smallest frequency value calculated; and

using the selected frequency value, computing the remaining gains of the controller.

10. A method for calculating a derivative term in a closed-loop controller that receives position error information at each servo processing interval, the method comprising the computer-implemented steps of:

recording three or more position error readings at different servo processing intervals;

computing a derivative estimate by;

summing two or more of the position error readings; and

subtracting an equal number of different position error readings than were used in the summing step; and

then

computing the derivative term based on the derivative estimate.

11. The method of claim 10, wherein the position error readings are recorded at successive servo processing intervals.