Method and automatic control apparatus for controlling a technological process

• US 4,545,008 A
• Filed: 12/14/1982
• Issued: 10/01/1985
• Est. Priority Date: 04/20/1981
• Status: Expired due to Fees

• Current Assignee: Leningradsky Tekhnologichesky Institute Tselljulozno-Bumazhnoi Promyshlennosti
• Original Assignee: Leningradsky Tekhnologichesky Institute Tselljulozno-Bumazhnoi Promyshlennosti
• Inventors: Sominin, Mikhail A., Fesenko, Evgeny P., Belokopytov, Jury A., Surikov, Valery N.
• Primary Examiner(s): Ruggiero, Joseph
• Assistant Examiner(s): MACDONALD, ALLEN R
• Application Number:
  US06/453,885
• Time in Patent Office: 1,022 Days
• Field of Search: 364/148, 364/152, 364/153, 364/154, 364/155, 364/157, 364/178, 318/636, 318/611
• US Class Current: 700/54
• CPC Class Codes: G05B 13/024 in which a parameter or coefficient is automatically adjusted to optimise the performance

Abstract

The method involves varying a parameter of an automatic controller to achieve optimal control quality and is operated in such manner that if the parameter of the controller changes in a direction of decrease in the stability margin of the control system, while the index of control quality is changing in a direction of increase in control quality, the parameter of the controller will be abruptly changed a number of times from a value corresponding to the stable state of the control system to a value corresponding to an unstable state thereof and back to the stable state until the index of control quality attains an optimal value corresponding to the best control quality. The automatic control apparatus comprises a storage device connected to the output of a device which generates a signal corresponding to the index of control quality, a control device for controlling the parameter of the automatic controller according to a signal generated by a direction signal generating circuit which responds to the direction of variation of the index of control quality. The apparatus includes a comparison circuit which changes the mode of operation of the device for controlling the parameter of the controller if the instant value of the index of control quality significantly deviates from the stored value corresponding to the best control quality.

Claims

1. A method utilizing an automatic control system for controlling a technological process by maintaining an output paramater of said process at a predetermined level with an automatic controller of the system susceptible of parameter variations in opposed directions in one of which the stability margin of the automatic control system is decreased, wherein for optimizing control quality as a function of said variations of said parameter of the controller said method comprises gradually changing the parameter of the automatic controller;

determining the change and direction of change of an index of control quality with said changing parameter;

reversing the direction of change of said parameter of the automatic controller if said index of control quality continues to change in the direction of decrease in control quality for a predetermined time;

determining the value of the index of control quality during variation of the index of control quality from increasing to decreasing control quality;

storing the value of said index of control quality thus determined at one of the instants of change in the direction of variation of said index of control quality from said increasing to decreasing control quality;

storing a new value of said index of control quality at the instant of the first change in the direction of variation of said index of control quality from said increasing to decreasing control quality when the deviation of the determined value of said index of control quality from the last previously stored value exceeds a predetermined value;

the improvement being characterized by increasing the speed of parameter variation of the controller in a direction corresponding to improved control quality, should said parameter be changing in a direction of decrease in the stability margin of the automatic control system while said index of control quality is changing in a direction of increase in control quality;

said improvement comprising

(a) abruptly changing said parameter of the automatic controller is from a predetermined value corresponding to a stable state of the control system, to a value corresponding to an unstable state of the control system during the time between the instant at which the deviation of the determined value of said parameter of the controller, from the latest stored value, exceeds said predetermined value of deviation and the instant of storing the next value of said index of control quality;

(b) abruptly changing, after a time less than that at which said automatic control system may lose stability, said controller parameter to a value corresponding to a greater stability margin of the control system than said predetermined value of the parameter; and

(c) gradually changing said controller parameter in direction of decrease in the stability margin of the automatic control system until said controller parameter again attains said predetermined value or the direction of variation of said index of control quality changes from increasing to decreasing control quality.

2. A method according to claim 1, wherein said index of control quality is the mean square deviation from the average value of the deviation of said output parameter of the technological process from said predetermined level.

3. A method according to claim 1, wherein said parameter of the automatic controller comprises the gain of said controller.

4. An automatic control apparatus for automatically controlling a technological process, comprising:

an automatic controller for maintaining an output parameter of said process at a predetermined level;

a control quality signal generating device for generating a signal representative of an index of control quality;

a control signal generating circuit for generating a control signal depending on variation of said signal representative of the index of control quality;

a parameter adjusting device connected to the output of said control signal generating circuit for adjusting a parameter of said automatic controller;

a controlled storage device having a data input connected to the output of said control quality signal generating device and a control input;

a direction signal generating circuit having an input connected to the output of said control quality signal generating device for generating a signal indicative of the direction of variation of the index of control quality and an output connected to the input of said control signal generating circuit for changing the signal at said output of said control signal generating circuit immediately after the direction of variation of the index of control quality changes from increasing to decreasing control quality;

a comparison circuit having a first input connected to the output of said controlled storage device and a second input connected to the output of said control quality signal generating device; and

a control circuit having inputs respectively connected to the output of said direction signal generating circuit and to the output of said comparison circuit for generating a binary signal having a first value when the magnitude of the difference between the current value of the index of control quality and its value stored in said controlled storage device exceeds a preselected value, and having a second value after the direction of variation of the index of control quality changes from increasing to decreasing control quality if the magnitude of the difference between the current value of the index of control quality and its value stored in said controlled storage device is smaller than said preselected value, said control circuit having an output connected to said control input of said control storage device to enable said controlled storage device to store the value of the index of control quality occurring just before said binary signal assumes said second value, said parameter adjusting device being connected to the output of said control circuit to abruptly change said parameter of the automatic controller, when said parameter attains a first predetermined value and said binary signal has said first value, to a limit value beyond the range of variation of said parameter during the period that said binary signal has said second value;

said automatic control apparatus further comprising

setting means for setting said parameter adjusting device to a second predetermined value a predetermined time after said parameter achieves said first value, said second predetermined value being less than said first predetermined value.

5. An automatic control apparatus according to claim 4, wherein said control circuit comprises:

a D flip-flop having a data input supplied with a logic signal having a constant value, an asynchronous set input connected to the output of said comparison circuit, a clock input and an output constituting the output of said control circuit;

a delay circuit; and

an AND gate having a first input connected by said delay circuit to said output of said D flip-flop, a second input connected to the output of said direction signal generating circuit and an output connected to said clock input of said D flip-flop.

6. An automatic control apparatus according to claim 4, wherein said control signal generating circuit comprises:

a binary flip-flop having a toggle input and an output constituting the output of said control signal generating circuit;

a pulse generator; and

a pulse counter having a counting input connected to the output of said pulse generator, a reset input constituting the input to said control signal generating circuit, said pulse counter having an output connected to said toggle input of said binary flip-flop.

7. An automatic control apparatus according to claim 6, wherein said binary flip-flop is further provided with an inverted output and said parameter adjusting device comprises:

a multibit reversible counter having data bit position inputs supplied with a predetermined combination of logic signals, an up-counting input, a down-counting input, a control input and bit position outputs;

a non-zero condition response circuit having inputs connected to said bit position outputs of said multibit reversible counter for determining the non-zero condition of the contents of said multibit reversible counter;

a NOT gate;

a first AND gate having a plurality of inputs one of which is connected through said NOT gate to the bit position output of said multibit reversible counter corresponding to the most significant bit position, the other inputs of said first AND gate being connected respectively to said output of said binary flip-flop and to said output of said pulse generator, said first AND gate having an output connected to said up-counting input of said multibit reversible counter;

a second AND gate having inputs respectively connected to the output of said non-zero condition responsive circuit, to said inverted output of said binary flip-flop and to said output of said pulse generator, and an output connected to said down-counting input of said multibit reversible counter;

a third AND gate having inputs respectively connected to the bit position output of said multibit reversible counter corresponding to the most significant bit position and to the output of said control circuit; and

a setting unit for setting said parameter of the controller, said setting unit having a plurality of control inputs one of which is connected to the output of said third AND gate, the other control inputs of said setting unit being respectively connected to the bit position outputs of said multibit reversible counter corresponding to the less significant bit positions, said setting means being a delay circuit connected between said output of said third AND gate and said control input of said multibit reversible counter.