JPS6023364B2 - Pulse width modulation controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an amplifier that calculates the deviation between an input signal and a set value and the deviation between a feedback signal, and generates an output signal of a constant amplitude according to the magnitude of the output signal of this amplifier. a jump amplifier, an output switching circuit driven by the output of the jump amplifier, and a feedback circuit for forming the feedback signal in response to the output of the jump amplifier, the output of a pulse proportional to the magnitude of the input signal; The present invention relates to a pulse width modulation type controller that generates a signal from the output switching circuit.

When controlling a process, pulse width modulating controllers are often used to operate integral actuators, such as electrically operated valves.

In this case, since the motor of the electrically operated valve cannot be directly driven by the output of the controller, several stages of auxiliary relays are generally provided between the controller and the motor to perform contact amplification. As shown in Fig. 4, these auxiliary relays and motors each have their own startup time, that is, the time from when a drive input (for example, the step input in Fig. 4A) is applied until they rise to a predetermined operating state. It has an operation delay time (time TI of the output characteristic in FIG. 4B), and during the sum total of these times, the electrically operated valve does not respond to drive input even if it is applied. Such operation delay time TI of the operating terminal will be referred to as dead time. Causes of such a dead time include, in addition to the start-up time of the auxiliary relay and electric motor, backlash, backlash, and frictional resistance in the mechanical drive system of the electrically operated valve. In FIG. 4B, the vertical axis represents the rotational speed N of the electric operating machine, and the horizontal axis represents the time t. Operation delay time TI is approximately 0.1 seconds, rated rotation speed No. The time T2 required to reach this point is approximately 0.2 sand. However,
When the operating end of an electrically operated valve, etc. that has such a dead time is driven by a pulse width modulation type controller, as the control deviation applied to the input of the controller decreases, the output pulse width also decreases proportionally. This may be smaller than the dead time of the operating end.

Therefore, even though the controller is generating output pulses to reduce the control deviation to zero, the operating end does not respond to the output pulses, and the control deviation remains, making it difficult to obtain good control results. be. In order to eliminate the inconvenience caused by the dead time of the operating end as described above, the present invention provides a pulse width modulation type controller that compensates for the dead time of the operating end and prevents the occurrence of a dead zone at the operating end. The purpose is to obtain. To achieve such an object, the present invention provides a pulse width modulation type controller of the type mentioned at the beginning, in which the lower limit value of the pulse width of the output signal of the controller is connected to the output side of the controller. In order to prevent the setting time of the output pulse width of this pulse generation circuit from becoming shorter than the dead time of the operating end, a constant pulse width pulse generation circuit driven by the jump amplifier is provided, and the setting time of the output pulse width of this pulse generation circuit is This is achieved by setting the output pulse width to be larger than the time, and driving the output switching circuit with a pulse having a longer pulse width, either the output pulse of the jump amplifier or the output pulse of the pulse generation circuit.

According to an advantageous embodiment of the invention, the constant pulse width pulse generation circuit is constructed, for example, by a monostable sulti-vibrator.

Further, the selection of the longer pulse width of the output pulse of the jump amplifier or the output pulse of the pulse generation circuit is performed by, for example, guiding both output pulses to an OR circuit, and via this OR circuit, the output switching circuit is driven. Hereinafter, illustrated embodiments of the present invention will be described.

FIG. 1 shows an example of a process control system using a general pulse width modulation type controller.

In this figure, 1 is a pulse width modulation type controller. This controller 1 has a set value SV and a controlled variable transmitter 8 for the process 7.
The amount of deviation from the control amount (input signal) PV that is returned through the circuit is determined, and an output pulse having a width corresponding to this amount of deviation is generated. This output pulse drives auxiliary relay 3a or 3b, turning on its contact 4a or 4b. This causes the electric motor 5 that drives the valve 6 to rotate forward or reverse, causing the valve 6 to rotate in the forward or reverse direction.
becomes open or open. The process 7 is controlled according to the opening and closing of the valve 6, and the controlled variable PV is sent to the controller 1 via the transmitter 8.
Similar control is performed until the control amount PV matches the set value SV and the control deviation becomes zero. 2 in FIG. 1 is a power source for driving the auxiliary relays 3a and 3b. An embodiment of a pulse width modulation type controller 1 according to the present invention used in such a control system is shown in FIG.

In this FIG. 2, 11 is an amplifier that calculates the deviation V between the set value SV and the control amount (input signal) PV, 12 is an amplifier that calculates the deviation between the deviation V and the feedback signal V2, and 13a and 13b. is the output signal V of the amplifier 12
A jump amplifier 14a, 14b generates an output signal of a constant amplitude according to the magnitude and polarity of the jump amplifier 13a.
, 13b, and is an output transistor that is turned on by the output voltage of the transistors 14a. At 14b, auxiliary relays 3a and 3b in FIG. 1 are driven. Also 15a, 1
5b is a switching element for driving the feedback circuit 16 that forms the feedback signal V2 in accordance with the output signals of the jump amplifiers 13a and 13b. and,
19a and 19b are monostable multipipulators connected in series to the output sides of the jump amplifiers 13a and 13b, respectively.

The outputs of the jump amplifiers 13a and 13b and the outputs of the monostable multipipulators 19a and 19b are connected to the output transistor 14 via OR circuits 20a and 20b, respectively.
a and 14b. Monostable multivibrators 9a and 19b and OR circuits 20a and 20b constitute pulse width limiting means PL for controlling the lower limit value of the output pulse width provided according to the present invention. A circuit like this except for the pulse width limiting means PL is as follows:
This is a general pulse width modulation type controller circuit. Before explaining the operation of the present invention, the general operation of the pulse width modulation type controller excluding the pulse width limiting means PL will be explained.

Assuming that the output signal V, which corresponds to the deviation between the set value SV of the amplifier 11 and the control amount (input signal) PV, is positive, the feedback signal V2 is initially zero, so the output signal V3 of the amplifier 12 is also positive. becomes. When the signal V3 is positive, the jump amplifier 13a operates and outputs an H level output signal Vo.
generate a. Accordingly, the switching element 15a
is turned on, and a constant positive voltage Ea is applied to the feedback circuit 16.
is added. If the feedback circuit 16 is a first-order lag circuit, the feedback circuit 16 generates a feedback signal V2 that increases with time in accordance with the time constant of the first-order lag circuit. Therefore, the output signal V3 of the amplifier 12 gradually decreases, and V3 becomes zero when V2 becomes equal to V, and as a result, the output signal Voa of the jump amplifier 13a returns to the L level, and the switching element 15a is turned off. Therefore, the jumping amplifier 1
The duration time of the H level output signal V of 3a is proportional to the magnitude of the deviation amount V between the set time charge V and the control amount PV,
An output pulse having a pulse width proportional to the magnitude of the positive deviation amount V is obtained from the jump amplifier 13a. Deviation amount V
When the polarity of , becomes negative, the jump amplifier 13b operates in the same manner, thereby obtaining an output pulse Vob having a pulse width proportional to the magnitude of the negative deviation amount V,. However,
With such a general pulse width modulation type controller, when the deviation amount V is small, the pulse width of the output pulse becomes correspondingly small, and the dead time of the operating end connected to the controller decreases. However, according to the present invention, the pulse width of the output pulse will not become smaller than a certain lower limit due to the action of the pulse width limiting means PL, as will be described below. When an input signal as shown in FIG. 3A is given to the monostable multipipulators 19a and 19b in the pulse width limiting means PL according to the present invention,
As shown in FIG. 3, it operates to generate an output signal with a predetermined time width regardless of the pulse width of the input signal.

Therefore, in the circuit of FIG. 2, the jump amplifier 13a
Or when 13D generates an output pulse, the monostable multipipe plate 19a or 19b generates a pulse with a time width of 7.

And this monostable multipipulator 19a or 19
b and the output pulse of the jump amplifier 13a or 13b are given to the output transistor 4a or 14b via the OR circuit 20a or 20b, so the output transistor 14a or 14b is connected to the jump amplifier 13a.
, 13b or monostable multipipulator 19a, 19
It is driven by the output pulse which has a larger pulse width. Therefore, even if the deviation amount V, becomes small and the jump amplifiers 13a, 13b generate output pulses with a time width smaller than 1, the monostable multipipulators 19a, 19b have a predetermined time width 7. Since a pulse is generated, the output transistors 4a and 14b are provided with a pulse having a minimum time width of 100 Hz. This dead time can be compensated for by setting the set time 7 of the monostable multivibrators 19a, 19b to a value larger than the dead time of the operating end. Therefore, according to the controller of the present invention, even if the operating end has a dead time, the control deviation that remains due to this dead time can be removed and the process can be well controlled. .

As explained above, according to the pulse width modulation type controller of the present invention, it is possible to compensate for the dead time due to the dead time of the operating end, mechanical play, back flash, etc. By using this method, control deviations based on the dead time of the operating end will not remain in the process control system, and the process control system can be controlled stably and well.

Therefore, the present invention has great practical utility value.

[Brief explanation of the drawing]

Fig. 1 is a block configuration diagram showing an example of a process control system using a pulse width modulation type controller, Fig. 2 is a circuit configuration diagram showing an embodiment of the present invention, and Fig. 3 is used to explain the operation of the present invention. The signal waveform diagram and FIG. 4 are input/output characteristic diagrams of the operating end motor. 1: Pulse width modulation type controller, 5: Operation motor, 6: Valve,
7: Process, 8: Control amount transmitter, 11, 12: Amplifier, 13a, 13b: Jump amplifier, 15a, 16b: Switching element, 16: Feedback circuit, 19a, 1
9b: monostable multipipelator, 20a, 20b: OR circuit, PL: pulse width control means. Next Figure 1 Game Z Kano 3 Figure Sai 4 Figure

Claims (1)

[Claims] 1. An amplifier that calculates the deviation between the input signal and the set value and the feedback signal, a jump amplifier that generates an output signal with a constant amplitude according to the magnitude of the output signal of this amplifier, and a and a feedback circuit for forming the feedback signal in response to the output of the jump amplifier, the output switching circuit generating a pulse output signal proportional to the magnitude of the input signal. In a width modulation type controller, in order to prevent the lower limit value of the pulse width of the output signal of this controller from being less than the dead time of the operating end connected to the output side of the controller, the controller is driven by the jump amplifier. a constant pulse width pulse generation circuit is provided, a set time of the output pulse width of the pulse generation circuit is set to be larger than a dead time of the operating end, and the output pulse of the jump amplifier and the output pulse of the pulse generation circuit are A pulse width modulation type controller, characterized in that the pulse width modulation type controller is led to an OR circuit, and the output switching circuit is driven by the output pulse of the OR circuit.