Manipulation-variable separated type system control method and apparatus

• US 4,354,224 A
• Filed: 04/21/1980
• Issued: 10/12/1982
• Est. Priority Date: 04/25/1979
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Sato, Takao
• Primary Examiner(s): Malzahn, David H.
• Application Number:
  US06/141,798
• Time in Patent Office: 904 Days
• Field of Search: 364/118, 318/611, 318/632, 318/561
• US Class Current: 700/78
• CPC Class Codes: G05B 5/01 electric
• CPC Class Codes: G05B 9/02 electric
• CPC Class Codes: G05D 9/12 characterised by the use of electric means
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence

Abstract

Manipulation-variable separated type control method and apparatus are used in a control system with a control element and a feedback element for an object being controlled or controlled object. The apparatus comprises a detector for detecting a relative value of a controlled variable, a first adder for applying a difference between a relative value output of the relative value detector and a relative reference value, and a second adder totalizing an output of the control element and an absolute reference value, for generating a signal representative of a manipulation variable for the controlled object. The absolute reference value for the manipulation variable is set to a nominal reference value for the controlled object in normal operation and applied to the controlled object irrespective of disturbances of the system. The relative reference value for the controlled variable is normally variable within an allowable change range of the controlled variable and is set such that the change of the manipulation variable determined by a deviation from the detected relative value is minimized for the absolute reference value.

Claims

1. A manipulation-variable separated type control method for controlling, in a control system with a control element and a feedback element, a manipulation terminal for an object being controlled or a controlled object based on a result of a comparison of a controlled-variable detection signal from the controlled object with a set signal, comprising the steps of:

(a) setting an absolute reference value C₁ for a manipulation variable and a relative reference value for the controlled variable under the condition that a relative change C₂ of the manipulation variable depending upon a deviation from the relative reference value is established to satisfy C₁ >

>

C₂ ;

(b) detecting a relative change of an actual controlled variable of said controlled object with respect to a reference value of the controlled variable;

(c) calculating the relative change C₂ of the manipulation variable by means of the control element from a deviation between the detected change for the controlled variable and said relative value; and

(d) superimposing the relative change C₂ for the manipulation variable on the absolute reference value C₁ independent of detection of disturbance to produce a total manipulation variable and supplying the total to the controlled object.

2. A control method according to claim 1 further comprising variably determining said relative reference value in accordance with an allowable change range of the controlled variable for said controlled object, and fixedly predetermining said absolute reference value in accordance with the reference value for the controlled variable at the time of normal operation of the controlled object, whereby a rapid change of the controlled variable with time is prevented in the event that a maximum disturbance occurs.

3. A control method according to claim 2 wherein said allowable change range σ

is represented by ##EQU2## where L_o is a reference value for the controlled variable, L₁ is an allowable change of the reference value, and Δ

t is a response time of the object.

4. A control method according to claim 1 further comprising setting said relative reference value at zero and setting said absolute reference value in accordance with the setting of a detection reference for said relative reference value, whereby operation of the controlled object is programmable.

5. A control method according to claim 1, 2, 3 or 4 wherein said control element has transfer functions for a proportional operation, an integral operation and a derivative operation either singly or in combination.

6. A manipulation-variable separated type modified feedback control system comprising:

(a) an object being controlled or a controlled object;

(b) control element means having a transfer function for a proportional operation, an integral operation and a derivative operation either singly or in combination;

(c) feedback means for feeding back a physical quantity detected from the controlled object;

(d) relative value detecting means provided at the controlled object for detecting a relative change deviated from a reference value for the controlled variable of the controlled object;

(e) first adder means with one input for receiving a relative value output from the detecting means through the feedback means and another input for receiving a relative reference value for the controlled variable, for generating a deviation between the two inputs;

(f) first setting means for setting the relative reference value;

(g) second adder means with one input for receiving an output from said control element means connected to receive the deviation output of the first adder means and another input for receiving an absolute reference value, for generating an output representative of a totalized manipulation variable obtained from superposition of the two inputs irrespective of detection of disturbance; and

(h) second setting means (C₁) for setting the absolute reference value for the manipulation variable,

whereby the absolute reference value (C₁) for the manipulation variable and the change (C₂) of the manipulation variable determined by the deviation from the relative reference value for the controlled variable are established to satisfy at least the relation which is C₁ >

>

C₂ and the total manipulation variable is the sum of divisions C₁ and C₂.

7. A control system according to claim 6 wherein said second setting means is cooperative with said relative value detecting means to change a reference value for the detection of the controlled variable by the detector in accordance with a change of the absolute reference value for the manipulation variable so as to make the output of the first setting means zero or approximation thereof.

8. A control system according to claim 7 wherein said second setting means is connected to absolute reference value generator means which is program-controlled.

9. A control system according to claim 6 wherein said second setting means is fixed to a value corresponding to a safe reference value for the controlled variable in the presence of a maximum disturbance, and said first setting means is variably set within an allowable range of change per unit time of the controlled variable dependent on the controlled object.