JPH04137009A - Control device output method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Industrial Application Field This invention is used for process control, etc., and is an output of a control device that performs calculations to obtain target values, etc. for control, and outputs the calculation results in analog form. Regarding the method.

(B) Prior Art Conventionally, for example, in a process control device, the deviation between a set value and a process value is determined at regular intervals, PID calculation is performed, and the calculation result is output as a manipulated variable. This operation N(
After the control W) output is output, it is held in a hold circuit including a capacitor until the next calculation result is output.

(c) Problems to be Solved by the Invention In the conventional control device described above, when calculation is performed every T1 period and the calculation result is output as a control amount that approaches the target value, the ideal control output is As shown in FIG. 4, the calculation result is held as it is as an output, and a new target value is output as a control amount for each calculation, and that value is supposed to be held until the next calculation output. however,
When the cycle of outputting calculation results becomes longer, the level (pressure) of a hold circuit including a capacitor decreases. For example, as shown in FIG. 5, the voltage decreases by V at the next update compared to the time of output. Further, if the hold circuit is made complicated for holding, etc., the number of parts used will increase, which is not desirable.

The present invention was made with a focus on the above-mentioned door opening point, and an object of the present invention is to provide an output method for a control device that can prevent a decrease in output even if the calculation cycle is long without complicating the hold circuit. It is an object.

(d) Means and operation for solving the problem The output method of the control device of this invention performs desired calculations for control,
In a control device that outputs the calculation result while holding it in a hold circuit including a capacitor for each first cycle, the first cycle is divided into a plurality of shorter second cycles, and the first cycle is divided into a plurality of shorter second cycles. Each time, the same value of the calculation result is sampled and outputted via the hold circuit.

In the output method of this control device, since the same calculation result is repeatedly output in the second period which is shorter than the first period which is the calculation period, it is possible to prevent a drop in the output voltage due to the short period.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 2 is a block diagram of a system 711 in which the present invention is implemented. This control device converts the digital calculation result calculated by a digital calculation circuit l such as a CPU into an analog signal by a D/A converter 2, and outputs the control signal via a switch 3 and a hold circuit 4 including a capacitor C. It is designed to be output as . The hold circuit 4 is only shown for one channel here, but the switch 3
Channels are selectively output.

The digital calculation circuit 1 calculates a control amount that approaches the target every cycle T2, and outputs the calculated value. However, if the control amount is output every cycle T2, the voltage will drop to V after T2 even if, for example, ◯ in FIG. 1 is the hold value.

Therefore, in order to prevent such a voltage drop, in this embodiment, the same calculation result ■1 is output every period T3, which is 1/4 of the calculation period T2, and is held in the hold circuit 4. , is outputting. Since T2=4T3, the output voltage drop is 1/4.The period T3 is the period T3.
2, the amount may be selected so that the voltage drop (1) can be ignored.

Next, the operation of the above embodiment control device will be explained with reference to the flow diagram shown in FIG.

First, when the operation starts, initialization processing such as resetting the timer T3 and variable n is performed (step 5TI), predetermined control calculations are performed, the calculation result V is obtained, and the calculation result V is held in the hold circuit 4. (Step 5T2).

At the same time, start the timer T3 (step 5T3), and wait for the timer T3 to time up (step 5T3).
4). When the timer T times up, it means that T has elapsed since the first calculation and output, and here,
While outputting the calculation result V as it is (step 5
T5), increment the variable n by 1 and set it to n-1 (
step 576). Next, it is determined whether n=4 (step ST?), and if the determination is NO, the process returns to step ST3, starts timer T3, and then waits for timer T to time up (step ST4). ).When the time is up, the calculation result ① is output as is, as in the previous step.Step 5T5), the i number n is incremented by 1, and n=2.In this way, the timer T3 continues to time up until n=4. Every time I do it, T3
The calculation result ■ is output for each period.

When n=4, this means that the calculation cycle T2 has arrived, and the determination in step ST7 is YES, and if the control is not finished (step 5T8), the variable n is reset (step 5T9) and the process returns to step ST2. Then, perform a new control calculation, ■. Outputs 1. Thereafter, the processing in steps 5Tl-3T9 is repeated in the same manner as above.

(f) Effects of the invention According to this invention, the same calculation result is repeated and held and output in the second cycle, which is the calculation result output cycle, which is shorter than the first cycle, so the calculation result output cycle is lengthened. Even in this case, the drop in performance level can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a control output characteristic diagram for explaining the output operation of a control device according to an embodiment of the present invention, FIG. 2 is a block diagram of a control device in which the present invention is implemented, and FIG. 3 is a control output characteristic diagram of the control device according to an embodiment of the present invention. FIG. 4 is an ideal control output characteristic diagram of the control device, and FIG. 5 is a control output characteristic diagram of a conventional control device. 1: Digital arithmetic circuit, 2: D/A converter, 4: Hold circuit.

Claims (1)

[Claims] (1) In a control device that performs a desired calculation for control and outputs the calculation result while holding it in a hold circuit including a capacitor for each first period, the first period is changed to a shorter period. 2. An output method for a control device, characterized in that the calculation result value is divided into a plurality of periods of 2, and the same value of the calculation result value is sampled and outputted via the hold circuit every second period.