PI or PID control loop with self-limiting integrator
AssigneeWangDAT, Inc.
InventorGeorge J. Bennett
Life of this patent
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Abstract
A control system having proportional and integral functions for controlling the rotational speed of a motor. The system includes a self-limiting integrator for avoiding or limiting integral wrapup, a problem commonly associated with integral control. The self-limiting integrator includes an integrator, limit comparator, OR gate, delay circuit, and sign reversal circuitry. The integrator reverses direction of integration when an error limit is realized. The error limit, a preestablished and adjustable value, can be used to determine the rise and settle time of the speed of the motor independently of the gain.
Claims37
A control system, comprising:
- an integrator for producing a representation of a sum of an error value over time;
- control loop means responsive to the representation of the sum of the error value over time for producing a control output value to modify the error value;
- limit detection means for determining when one or more error limit values in the control loop is realized;
- and
- means responsive to the limit detection means for reversing the sign of the error value input to the integrator when one or more error limit values is realized.
A method for controlling a parameter to be controlled, comprising the steps of:
- monitoring the parameter to be controlled;
- generating an error signal related to a difference between the parameter and a predetermined value;
- integrating said error signal in a first direction to produce a control signal;
- reversing the sign of the error signal prior to integration when one or more error limit values is realized;
- and
- controlling the parameter in response to the control signal.
A method for limiting integral wrapup in a control system, comprising the steps of:
- integrating an error value to produce an increasing control value for use in the control system;
- comparing a variable in the control system with an adjustable error limit value related thereto;
- and
- integrating the error value to produce a decreasing control value when the variable reaches the error limit value related thereto.
Dependencies are inferred from the claim text.