ADAPTIVE CONTROL SYSTEM AND METHOD

• US 3,622,767 A
• Filed: 01/16/1967
• Issued: 11/23/1971
• Est. Priority Date: 01/16/1967
• Status: Expired due to Term

• Current Assignee: Richard W. Koepcke
• Original Assignee: Richard W. Koepcke
• Inventors: Koepcke, Richard W.
• Primary Examiner(s): Morrison, Malcolm A.
• Assistant Examiner(s): Gruber, Felix D.
• Application Number:
  US04/609,415
• Time in Patent Office: 1,772 Days
• Field of Search: 235/150.1,151.1,151.11,151.12,151.13,151.31,151.35,151.34,184 318/561
• US Class Current: 700/32
• CPC Class Codes: G05B 13/0245 not using a perturbation signal

Abstract

A control system of the adaptive type in which the applicable control law is chosen from a finite set of possibilities, with changes between the control laws being effected dependent upon the relative changes in system performance, without relation to external performance standards. As performance varies, comparisons between successive values for the chosen criteria are continually made and the system shifts between individual control laws within the available set of control laws to tend toward optimum performance for the conditions under which the system is then operating.

Claims

1. The method of operating a control system to improve system performance that includes the steps of:

monitoring variations in a selected criterion of performance of the system and generating a variation during each successive time interval;

establishing for the control system a finite set of operative control conditions covering selected performance range, the differences between individual ones of the finite set being appropriately proportioned over said performance range; and

shifting between adjacent conditions in the finite set of operative control conditions in response to said variation signal in each successive time interval to seek to improve the criterion of performance for the next time interval.

2. The method of operating a control loop to control a device that includes the steps of:

generating criterion of variations in an error signal in the control loop during successive time intervals;

comparing changes in the criterion between each of successive time intervals; and

generating a favorable or unfavorable indication signal as a result of the comparison;

utilizing one of a finite set of gain control values in the operation of the control loop during each time interval; and

shifting to an adjacent gain control value in response to each comparison signal, the direction of shift being in the same direction each time the comparison signal is favorable and being reversed in the other direction whenever the comparison signal is unfavorable.

3. The method of operating a control loop controller having a set point value and tending to maintain a control device at the set point position by generating an error signal including the steps of:

repetitively computing the sum of the error signal squared over a selected interval and generating a sum signal;

comparing the results of successive sum signals to determine the increase or decrease of the sum signals; and

shifting the forward gain of the controller to an adjacent gain value of a finite set of gain values in accordance with the results of each comparison, the direction of shift being in the same direction each time the comparison shows a relative decrease and being reversed whenever the comparison shows a relative increase.

4. The invention as set forth in claim 3 above wherein the comparing step is accomplished by storing the results of one computation and comparing the results with the results of the next succeeding computation, and wherein during the step of sifting, the direction of sift is reversed whenever the end of the finite set is reached.

5. An adaptive control system comprising:

a closed loop controller having a finite set of individually selectable operating modes, the individual modes of said set covering an operating range, the differences in magnitude between adjacent individual modes being appropriately proportioned to the range to be covered;

an error-indicating circuit responsive to operation of the controller for indicating the quality of performance thereof during a selected time interval;

a comparator circuit responsive to successive indications from the error-indicating circuit for indicating the relative nature of successive changes in the quality of performance; and

shift control circuits for shifting the closed loop controller to an adjacent operating mode in response to each indication from the comparator circuit even when the controller is in an optimum operating mode before they shift, the direction of shift being reversed whenever the relative nature of successive changes and the quality of perfoRmance are undesirable.

6. A process control system in which at least one control variable is to be maintained at selected set points under varying conditions, including the combination of:

an equation solver system responsive to variables in the process system and indicating selected set points for the controlled variable;

a closed loop controller having a selectable finite set of operating modes, and including a controlled device controlling the controlled variable and a device coupled to the controlled device for indicating the actual set point of the controlled variable, the controller generating an error signal indicative of the variation between actual and selected set points during operation;

an error signal comparator circuit responsive to the error signal from the controller and providing a signal time sample indicative of variations therein during successive time intervals;

a comparator circuit responsive to the comparator circuit for comparing the successive time sampled variations in the error signal to indicate relative changes and the quality of performance; and

shift control circuits shifting to an adjacent operating mode in response to each comparison of the comparator circuit irrespective of whether the controller was in an optimum mode before the shift.

7. A closed loop controller for a controlled device operating in response to chosen settings and including an actual setting indicator, said controller comprising:

first comparator circuits responsive to the chosen settings and actual settings for generating an error signal;

controlled circuits having a finite set of operating modes, and being responsive to the error signal and operating the controlled device;

a signal generator circuit responsive to the error signal for providing indications of performance during successive time intervals;

a memory circuit responsive to the indications of performance;

a second comparator circuit coupled to the memory circuit and to the signal generator circuit to compare each indication of performance with the succeeding indication of performance and to indicate relative changes in the quality of performance between each successive time interval; and

shift control circuits shifting the operating mode to an adjacent operating mode and the finite set at the end of each successive interval in response to the relative changes indicated by the second comparator circuit.

8. Closed loop controller as set forth in claim 7 above, wherein the finite set of operating modes for the controlled circuits represents a number of gain adjustments, wherein the signal generator circuit provide signals corresponding to the sum of the errors squared, and wherein said shift control circuits reverse direction of shift upon reaching either limit of said finite set and when relative changes indicated by the comparator circuit are unfavorable.