Electric motor controller

• US 7,437,201 B2
• Filed: 01/14/2003
• Issued: 10/14/2008
• Est. Priority Date: 01/14/2003
• Status: Expired due to Fees

• Current Assignee: Christopher P. Cullen
• Original Assignee: Christopher P. Cullen
• Inventors: Cullen, Christopher P.
• Primary Examiner(s): DeCady; Albert
• Assistant Examiner(s): Norton; Jennifer L
• Application Number:
  US10/341,953
• Publication Number:
  US 20040135534A1
• Time in Patent Office: 2,100 Days
• Field of Search: 700 29- 31, 718/1, 718100-108, 318/254, 318/439, 318/561, 703/2, 640825-8259, 388/904
• US Class Current: 700/29
• 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 comprising the machine-implemented steps of:

performing a self-commissioning process to compute a motor model that relates a motor control signal applied by a controller to a motor to the motion of the motor, wherein the self-commissioning process is automatically performed in response to receipt of a first user input and the motor model is computed without requiring a second user input;

determining a set of motion profile parameters that specify a motor control signal based on the motor model such that a motion resulting from application of a motor control signal specified by the motion profile parameters does not exceed any constraint values of a constraint value set; and

supplying the motion profile parameters to a controller to generate the motor control signal specified by the motion profile parameters.

2. The method of claim 1 wherein the constraint value set includes one or more constraint values each limiting operation of the motor.

3. The method of claim 2 wherein the constraint value set comprises at least one of the following:

maximum velocity, maximum acceleration, maximum current, maximum root-mean-square (RMS) current, or maximum RMS acceleration.

4. The method of claim 1 further comprising:

minimizing a duration of the motion resulting from the application of the motor control signal.

5. The method of claim 1 further comprising:

modifying the set of motion profile parameters to a predetermined format; and

wherein supplying the motion profile parameters to a controller comprises supplying the modified set of motion profile parameters to a controller to generate the motor control signal specified by the motion profile parameters.

6. The method of claim 1 further comprising:

selecting an acceleration pulse form, and wherein the set of motion profile parameters define an acceleration pulse of the selected acceleration pulse form.

7. The method of claim 1 further comprising:

selecting a motion plan algorithm, and wherein determining a set of motion profile parameters is also based on the selected motion plan algorithm.

8. The method of claim 1, wherein the set of motion profile parameters comprise:

a sequence of acceleration pulses, each pulse specified in terms of duration and peak acceleration.

9. The method of claim 8, wherein the sequence of acceleration pulses is any one of the following types of accelerations pulses:

quadratic, harmonic, trapezoidal, piecewise linear, or cycloidal.

10. The method of claim 1, wherein the set of motion profile parameters comprise a set of peak jerk, peak velocity, and peak acceleration values.

11. The method of claim 1, wherein determining a set of motion profile parameters based on the motor model comprises:

selecting an initial set of motion profile parameters;

computing one or more signals using the initial set of motion profile parameters;

comparing the computed one or more signals to one or more corresponding values of the constraint value set;

if the computed one or more signals are not within a predetermined amount of the one or more corresponding values of the constraint value set, then iteratively selecting other sets of motion profile parameters until a set of motion profile parameters produces one or more signals that are within a predetermined amount of the one or more corresponding values of the constraint value set.

12. The method of claim 1, further comprising receiving a command to move to a specified position.

13. The method of claim 1, further comprising receiving a command to move with a specified velocity.

14. The method of claim 1, further comprising receiving a command to move to a specified position at a specified velocity.

15. The method of claim 7, wherein the motion plan algorithm comprise any one of the following:

a pulse-cruise-pulse algorithm, a balanced pulse-cruise-pulse algorithm, or a balanced pulse-pulse algorithm.

21. The method of claim 1, wherein the self-commissioning process is automatically performed in response to a first receipt of a motion function command.

22. The method of claim 1, wherein the self-commissioning process is performed in response to receipt of a self-commissioning initiation command.

23. The method of claim 1, wherein the self-commissioning process comprises:

applying a control signal that causes the motor to change position over a period of time;

recording the control signal over a period of time;

recording position information of the motor over a period of time resulting from the application of the control signal;

estimating a plurality of derivatives of position based on the recorded position information, wherein the plurality of derivatives includes both a first order derivative and a second order derivative; and

computing a motor model comprising the step of fitting the plurality of derivatives of position into a motor model equation that relates the control signal to a motion of the motor.

24. The method of claim 1, wherein the motor is selected from the group consisting of DC brush, DC brushless, AC brushless, and inductance motors.

25. The method of claim 1, further comprising receiving a command to perform a motor function.

16. A controller for an electric motor having a position-feedback device that provides position feedback information to the controller, the controller comprising:

a motor model computation module configured to compute a motor model equation that relates controller output to motion of the motor; and

a trajectory planning module configured to receive a motion function command and, in response to receiving the motion function command, compute a set of motion profile parameters based on the motor model equation and a predetermined constraint value set, such that the motion resulting from application of a motor control signal specified by the set of motion profile parameters does not exceed any of the constraint values in the constraint value set.

17. The controller of claim 16 wherein the motor control signal comprises a signal that is within 5% of a constraint value of the set.

18. The controller of claim 16 further comprising:

a trajectory generator module configured to receive the motion profile parameters and generate a signal to cause the motor to execute the motion function specified in the motion function command.

19. The controller of claim 18 further comprising:

a closed-loop control device configured to calculate position errors during execution of the motion function command and adjust controller output to compensate for calculated errors.

20. The controller of claim 16 further comprising:

a position-measuring interface device configured to receive the position feedback information and record both a change in position and an indication of time at which the change of position occurred.