JPS5991503A - Control amplifier - Google Patents

Abstract

PURPOSE:To control the input of a controlled system by adding a quantity obtained by integrating a deviation value between an instructed value and a detected value to a quantity proportional to the deviation value to obtain a proportional integral value and outputting a value obtained by subtracting a compensating value proportional to the detected value from this proportional integral value. CONSTITUTION:A deviation value X1 between an instructed value ni and a feedback value n0 is obtained by subtraction. This deviation value X1 is inputted to a proportinal integral amplifier 12. First, the deviation value X1 and a constant Kp are multiplied to obtain a proportional component X2, and next, the deviation value X1 is divided by a value (for example, 1,000) corresponding to a sampling period to obtain a value X3. This value ismultiplied by a constant KI to obtain an integral quantity X4 per one sampling. The quantity X4 is added to the preceding integrated value to obtain a new integral value X5 as an integral component. The integral component and the proportional component are added to obtain a proportional integral value X6. Meanwhile, the feedback value n0 is inputted to a proportional amplifier 13 and is multiplied by a constant KB to obtain an overshoot preventing compensating value X7, and these values are subtracted in a subtractor 14 to obtain an output eC of a control amplifier 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control amplifier, and more particularly to a control amplifier used for feedback control.

[Technical background of the invention and its problems]

The basic configuration of feedback control is shown in Figure 1. Command value (target value) ei and output value (control value) e of controlled object 2
o is compared and amplified by the control amplifier 1, and its output (operation value) eC controls the 20 inputs to be controlled, and the output value e
o is controlled so that it has a value close to the command value ei.

FIG. 2 shows the case of speed control of an electric motor as an example of feedback control. This speed control will be explained below as an example. The purpose of this speed control system is to control the speed no of the electric motor 4, and the command value is given as a speed command and a value old.

Speed command value ni and speed n detected by speed detector 5
o is compared and amplified by a control amplifier l, and its output ec is input to a power amplifier 3. The power amplifier 3 is powered by the human power e.
Power amplification is performed to cause a current 1 corresponding to c to flow through the motor 4. An electric motor generates a torque proportional to the current, and the speed increases or decreases according to this torque, resulting in speed deviation (ni-no)
is controlled so that it is slightly distorted.

When a load is applied to the motor, the speed n of the motor.

decreases, the speed deviation increases, the output ec of the control amplifier and the motor current limit increase, the torque generated by the motor increases, and eventually the speed is controlled so that it does not change.

Figure 3 shows a simple lifetime proportional amplifier that can be used as a control amplifier. 6 is a subtracter, and 7 is an amplifier, which amplifies the input by Kp times. The deviation between the command value old and the detected output value no is determined by the subtracter 6, and this is simply amplified by a factor of Kp. In order for the output ec of the control amplifier l to have a certain value, there must be a deviation, and if the motor is generating torque, the speed will differ from the command value even in a steady state where the speed command and load torque are constant. It will have a deviation (steady deviation).

Is it used to eliminate steady-state deviation? [tt There is a proportional-integral amplifier shown in FIG. 4 as a control amplifier. 8 is a proportional-integral amplifier, which outputs the sum of the difference multiplied by Kp and the sum of the difference proportional to the integral amount of the deviation. Proportional-integral amplifier input 9-K
, the transfer relation coefficient o, , (-p ni ) of the corresponding output is expressed by the equation (1). is the proportionality constant S is the Laplace operator. When a steady deviation is about to occur, this deviation is integrated,
The output ec of the control amplifier 1 increases and decreases, and as a result, no steady deviation occurs. On the steady state j-line, the speed command value old and the speed no match.

However, when a proportional-integral amplifier is used, as shown in FIG. 5, a so-called overshoot occurs in which the speed exceeds the command value once due to a change in the speed command value. In feedback control, there is always a control delay,
Bonds integrated during this delay (proportional to the area of A shown)
This arises from the fact that t (proportional to the area of B shown in the figure), which is negatively integrated in the overshoot portion, must be equal to t.

In order to prevent this overshoot, the proportional-integral amplifier has an overshoot prevention compensation circuit N as shown in FIG.
I9 is added. This is to add a type of differentiation circuit (-next advance circuit) to the feed balance circuit, and to cancel the amount integrated due to the delay of the 11ilJ control by the change in the detected value. The transfer function G(A) of the output to the input of the overshoot prevention compensation circuit is shown by the equation (2). However, KA is the proportional constant. If 0, then the constant S is the Laplace operator. The response of each part to the speed command value ni when using is shown. The shaded area is the magnitude of the signal Na generated by the overshoot prevention compensation circuit. The speed n is determined by adjusting the constants KA and ω so that the area of the shaded area and the z amount integrated by the control delay (area of A in the figure) are equal.

overshoot can be prevented. This control amplifier has very excellent characteristics with no steady-state deviation and no overshoot.

However, in the proportional-integral amplifier with overshoot prevention compensation, the constants that must be controlled are Kp, KI, and KA.

There are 4 with 0 people, making it difficult to adjust.

In addition, conventionally, these control amplifiers were constructed from analog circuits using operational amplifiers, so even control amplifiers with integral elements that theoretically do not produce a constant latent S difference can produce steady-state deviations due to errors in the operational amplifiers. was.

In contrast, recently, improvements in precision have begun to be achieved by digitally controlling these control layers 1@ using microcomputers and the like. Digital integration can perform error-free integration, and in the case of a proportional-integral amplifier, steady-state deviation can be completely eliminated.

However, when differential calculation is performed with overshoot prevention compensation added, the amount of differentiation becomes infinitely small as the steady state approaches, and digital calculation has no choice but to abort the calculation. For this reason, in the proportional-integral amplification with overshoot prevention compensation, the stationary bias cannot be completely eliminated even if the digital calculation L calculation is performed. There was a desire to develop a control amplifier suitable for digitalization in order to improve control performance and precision.

[Purpose of the invention]

The present invention was made in view of the above-mentioned circumstances, and aims to facilitate the construction of a proportional-integral amplifier with overshoot prevention compensation, and to obtain a control amplifier with submerged characteristics that completely eliminates steady-state deviation when digitalized. do.

[Summary of the invention]

The present invention provides a control amplifier that inputs a command value for the output of a controlled object and a detected value of the output of the controlled object, performs soft amplification, and controls the input of the control ordinal. a first calculation means for obtaining a proportional integral value obtained by adding an integral amount of the deviation value to an amount proportional to the deviation value of , and outputting a value obtained by subtracting a compensation amount proportional to the detected value from the proportional integral value; In this control amplifier, a second calculation means for controlling the input of the controlled object is provided so that adjustment is easy and excellent response characteristics can be obtained.

[Embodiments of the invention]

FIG. 8 shows an embodiment of the present invention. 11. , 14 is a subtracter, 12 is a proportional-integral amplifier, 13 is a proportional amplifier,
These constitute a control amplifier lO.

The command value n1 and the feedback value no are manually input to the subtracter 11 to obtain a deviation (ni-no). This deviation is input to the proportional-integral amplifier 12. -10,000, the feedback value no is also input to the proportional amplifier 13. A subtracter 14 subtracts the output of the proportional amplifier 13 from the output of the proportional-integral amplifier 12 to obtain ec as the output of the control amplifier 1o.

Transfer function Gc of control amplifier output ec to command value ni
i is expressed by equation (3), which is completely the same as the conventional example shown in FIG.

On the other hand, the control amplifier output e for the feedback value no
The transfer function Gco of c is expressed by equation (4).

In the case of the conventional example shown in FIG. 6, the transfer function of the control amplifier output with respect to the feedback value is expressed by equation (5).

However, in the case of the conventional example, generally (Kr /Kp)
It is known from experience that good characteristics can be obtained if ωA and ωA are selected to be approximately equal. Substituting (K/Kp) for ωA, we get (
6) Equation becomes.

KI Gco' = -(KP +-+KPKA)...
(6) Therefore, if Ka is chosen equal to KPKA, the transfer function will be the same as in the conventional example, and a control amplifier with exactly the same characteristics can be obtained, and the constants that need to be adjusted will be the same as in the conventional example. Kp, 'KI, KA, 0 can be reduced from 4 to 3, KA, KI, KB-8 Also, as can be easily seen from Figure 8, the differential that causes arithmetic truncation errors in dental calculations No calculations are required, and when digitized, proportional-integral amplification with overshoot prevention compensation can be performed that completely eliminates steady-state deviations.

FIG. 9 shows a specific configuration of the present invention when an operational amplifier is used. 15 to 22 are resistors, O is a capacitor, Jun~
The station is an operational amplifier. When the resistance values of resistors 15, 17 to 2 are R, the values of resistors 16 and 22 for constant 5 Kp, KI, and Ka are KpL, and the value of the capacitor n is 1/K r R. A similar transfer function can be obtained. Since it is a combination of the basic configuration of commonly used operational amplifiers, a detailed explanation will be omitted, but the part consisting of resistors 19 and 20- and the operational amplifier inverts the polarity of the signal. The part consisting of resistors 15, 16゜21, capacitors, and operational amplifier 5 (
The section consisting of the resistors 17, 18.degree. 22, and the step-up amplifier door performs the addition. If it is noted that the polarity of the signal is inverted between the input and output of the operational amplifier, it can be seen that the transfer function is the same as that of the embodiment shown in FIG.

FIG. 10 shows an example of a flowchart showing the algorithm of the present invention (fitl amplification realized by a microcomputer). When an interrupt occurs at step n, step 28
With command 1 immediately old, feedback value no, constant 111Kp
.

Read Kx and Ks. This interrupt is executed at predetermined intervals (for example, every 1 m5). Next, in step 4, the command value n
The deviation value X between i and the feedback value no is obtained by subtraction. The point of discussion is step power! Calculate the direct input and constant Kp to find the proportional component. In step 31, the deviation value
) to find X3, which is then multiplied by a constant in step 32 to find the integral over one sampling. At the step, a new integral value is obtained as an integral by adding the previously integrated value to the equation. Add the step integral & and the proportional division to find the proportional integral division. Next, in step 35, the feedback value nOK is multiplied by the constant KB to obtain an overshoot prevention compensation amount. X8 is obtained by subtracting the overshoot prevention compensation amount from the step application ratio sequence integral input, and in step 37, this person is outputted as the control amplification output ec. Step 38 ends the series of interrupt programs.

〔Effect of the invention〕

As described above, according to the present invention, there are fewer adjustment points in feedback control, and adjustment becomes easier. Furthermore, when digitalized, steady-state deviations can be completely eliminated, allowing for control with unprecedented precision. Although the speed control of an electric motor has been explained as an example, feedback control is widely used in all fields, and the effects of the present invention are enormous.

[Brief explanation of drawings]

Figures 1 and 2 are block diagrams for explaining feedback thickness control, Figures 3, 4, and 6 are examples of conventional control amplifiers, and Figures 5 and 7 are control responses. A diagram explaining
FIG. 8 is an embodiment of the control amplifier of the present invention, FIG. 9 is a specific circuit configuration diagram of the control amplifier of the present invention, and FIG. 10 is a flowchart showing an algorithm for implementing the present invention in a microcomputer. It is. 1.10... Control amplifier 2... Controlled object 3.
...Power amplifier 4...Electric motor 5...Speed detector 6,11.14...Subtractor 7.13...
・Proportional amplifier 8, 12... Proportional integral amplifier 9...
・Overshoot prevention compensation circuit 15-22...Resistor η...Capacitor 24-26...Operation amplifier (7317) Agent: Patent attorney Noriyuki Noriyuki (and one other person)
Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Back IC! -le θ XX/ /10o. XJ r”

Claims (1)

[Claims] In a control amplifier that inputs a command value for the output of a controlled object and a detected value of the output of the controlled object, compares and amplifies the input, and controls the input of the controlled object, a deviation value between the command value and the detected value is determined. a first calculating means for obtaining a proportional integral value obtained by adding an integral amount of the deviation value to a proportional amount; A control amplifier characterized in that it is provided with a second arithmetic means for controlling the input of the control amplifier.