Apparatus having a motor, controller for the motor, and method of controlling the motor

• US 7,408,317 B2
• Filed: 05/03/2006
• Issued: 08/05/2008
• Est. Priority Date: 05/04/2005
• Status: Active Grant

• Current Assignee: Wildeck, Inc. (Holden Industries Incorporated)
• Original Assignee: Wildeck, Inc. (Holden Industries Incorporated)
• Inventors: Payne, Stephen M.
• Primary Examiner(s): Donovan; Lincoln
• Assistant Examiner(s): Dinh; Thai
• Application Number:
  US11/381,476
• Publication Number:
  US 20060250102A1
• Time in Patent Office: 825 Days
• Field of Search: 318/638, 318/639
• US Class Current: 318/638
• CPC Class Codes: G05B 19/4062 Monitoring servoloop, e.g. overload of servomotor, loss of feedback or reference
• CPC Class Codes: G05B 2219/42288 Limit, stop drive current if axis obstructed, blocked, force against stop
• CPC Class Codes: G05B 2219/42289 Avoid overload servo motor, actuator limit servo torque

Abstract

A method, and a system of using the method, of controlling a motor having a rated capacity. The method includes determining the motor has been started, determining a plurality of operating parameters of the motor after the motor has started, determining a threshold from a portion of the operating parameters, comparing one of the determined operating parameters with the threshold, and operating the motor at a level corresponding to below the rated capacity when one of the determined operating parameters is greater than the threshold. When an electric motor having a control system according to the present invention lifts a load, drives a machine, or starts other motions, the control system automatically adjusts to a power level that corresponds to the load. In this way, the motor will not be allowed to exert any power or force to the load in excess of what is necessary. If the machine being driven becomes jammed, binds, or draws more power for some unexpected reason, the motor will be shut down to reduce or to limit damage to the load or the machine.

Claims

1. A method of controlling a vertical reciprocating conveyor having a motor, lifting apparatus, and path in which the lifting apparatus moves in response to a mechanical power produced by the motor, the method comprising:

loading material into the lifting apparatus;

determining if the motor has been started to move the vertical reciprocating conveyor and the material;

reading an initial amount of current drawn by the motor required for the vertical reciprocating conveyor to move the material;

determining a statistical value of the initial amount of current drawn by the motor;

deriving a fixed steady state limit of the operating parameter from the statistical value and the initial amount of current drawn by the motor, wherein the fixed steady state limit remains fixed while the motor continues to drive the vertical reciprocating conveyor and the material, and wherein the limit remains independent of how far the vertical reciprocating conveyor has moved;

moving the vertical reciprocating conveyor with the material after the fixed steady state limit has been derived;

reading a subsequent amount of current drawn by the motor after the vertical reciprocating conveyor has started to move the material;

comparing the subsequent amount and the fixed steady state limit; and

stopping the motor when the subsequent amount is above the fixed steady state limit for a period of time.

2. The method of claim 1, wherein reading an initial amount of current drawn comprises sensing the initial amount of current drawn by the motor after the current drawn by the motor has started to decrease after the motor has started.

3. The method of claim 1, wherein reading the initial amount of current drawn comprises sensing the initial amount of current drawn by the motor after the motor has started for a period of time.

4. The method of claim 1, wherein determining the statistical value comprises determining an average, a mean, a variance, and a standard deviation of the initial amount of current drawn by the motor.

5. The method of claim 1, wherein deriving a fixed steady state value comprises summing the initial amount of current and the statistical value.

6. A control system for a machine having a motor, lifting apparatus into which material is loaded, and path in which the lifting apparatus moves in response to a mechanical power produced by the motor, the system comprising:

a sensing module configured to read a steady state operating parameter of the motor after the motor has started to move the machine and the material, and a subsequent value of the operating parameter; and

a controller configured to set a fixed operating parameter from the steady state operating parameter, wherein the fixed operating parameter remains fixed while the motor is driving the machine, and wherein the fixed operating parameter remains independent of how far the machine has moved, to compare the subsequent value of the operating parameter with the fixed operating parameter while the machine is moving, and to stop the motor when the subsequent value of the operating parameter is greater than the fixed operating parameter for a period of time.

7. The system of claim 6, wherein the operating parameter comprises one of an amount of current drawn by the motor, a speed exhibited by the motor, a temperature of the motor, a pressure exhibited by the motor, and a torque generated by the motor.

8. The system of claim 6, wherein the controller is further configured to determine the fixed operating parameter based on a statistical value comprising one of an average, a mean, a variance, and a standard deviation of the operating parameter of the motor.

9. The system of claim 8, wherein the controller is further configured to set the fixed operating parameter above the statistical value.