JPH0672672B2 - Fluid control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device that controls a flow rate and a pressure, that is, a control amount by performing PWM modulation (pulse width modulation) on an electromagnetic on / off valve.

(Prior Art) A conventional device shown in FIG. 2 has an oscillating unit 1 that oscillates a constant rectangular wave signal, and a sawtooth wave or a triangular wave (hereinafter referred to as a reference signal wave) by integrating the rectangular wave signal of the oscillating unit 1. The output signal of the integrator 2 is input to the comparator 3, and the target signal Vr output from the target signal generator 4 is also input to the comparator 3. I am trying.

Then, the output signal of the comparison unit 4 is transmitted to the electromagnetic on / off valve 6 via the amplification unit 5, and its operation is as follows.

That is, as shown in FIG. 3, the comparison unit 3 compares the sawtooth wave signal Ve from the integration unit 2 with the target signal Vr from the target signal generation unit 4, and the comparison result is (Vr-Ve). > 0
When, the modulation signal becomes high level, and (Vr-Ve) ≤ 0
At this time, the modulation signal is set to the low level.
Then, the output signal of the comparison unit 3 is amplified by the amplification unit 5 and applied to the solenoid of the electromagnetic on / off valve 6.

Therefore, the modulation rate of the voltage applied to the solenoid (ratio between the modulation cycle and the time when the voltage is applied) is controlled according to the target signal Vr, and the flow rate is adjusted to the desired value according to the modulation rate. Controlled by value.

(Problems to be Solved by the Present Invention) However, the electromagnetic on / off valve 6 has a delay time τ _ON from when a voltage is applied to its solenoid until the electromagnetic on / off valve 6 is opened. Generally, there is a delay time τ _OFF from when the application is cut off until the electromagnetic on / off valve 6 is closed. Since there is a delay in the opening / closing operation of the electromagnetic on / off valve 6 as described above, the modulation rate of the modulation signal and the modulation rate of the on / off valve (ratio between the modulation cycle and the time when the electromagnetic on / off valve is open) are as described above. Does not change proportionally.

Therefore, as shown in FIG. 4, when the modulation rate of the modulation signal is equal to or less than the constant value η _ON , there is no time for the electromagnetic on / off valve to open, so that it does not open. Further, when the modulation rate is higher than the constant value η _OFF , there is no time to close the valve, so that the on / off valve 6 continues to be fully open. Therefore, the flow rate changes according to the modulation rate of the applied voltage because the modulation rate is η _ON
Only it becomes, the eta _ON below and eta _OFF region between eta _OFF
In the above case, the actual control becomes impossible and the control area becomes narrower accordingly.

Also, in order to improve the response of the control system, the modulation frequency must be increased, but when the modulation frequency is increased, the above η _ON becomes large and η _OFF becomes small, so the control area becomes narrower. Become.

Further, the flow rate also changes due to disturbance such as pressure fluctuation of the hydraulic pressure source.

Therefore, the above-mentioned conventional device has a problem that its control area is limited, high-speed response cannot be realized, and it is vulnerable to disturbance.

According to the present invention, the response of the solenoid of the electromagnetic on / off valve is assumed to be delayed, but the response is improved by maintaining the linearity between the input signal and the output signal by improving the control system. The purpose is to secure a control area for the height and to be strong against external disturbances.

(Means for Solving Problems) In order to achieve the above-mentioned object, the present invention has the following configuration.

That is, a control amount detection unit that detects the output control amount and outputs a signal according to the control amount, a target signal generation unit that outputs a signal according to the target control amount, and the target signal generation unit. The adder / subtractor that calculates the deviation between the signal from the control amount detector and the signal from the control amount detector, the integration unit that integrates the deviation output from the adder / subtractor, and the basic clock signal with a cycle sufficiently short with respect to the modulation cycle. A clock signal generator that outputs, a first counter that counts the basic clock of the clock signal generator and outputs a clock signal at each modulation cycle, and an output of the integrator when the clock signal of the first counter is input Depending on the signal, it operates by a pulse number calculation unit that calculates whether to maintain the modulation signal at a high level or a low level, and a timing signal output from this pulse number calculation unit, The second counter that starts counting the basic clock number from the clock signal generating section and outputs a signal when counting the designated pulse number output from the pulse calculating section and the timing signal from the pulse number calculating section Modulation that keeps the modulation signal at a high level or a low level from the input to the count end signal from the second counter, and outputs a low or high level modulation signal after the count end signal is input. A signal output unit and an electromagnetic on / off valve that performs an on / off operation according to the modulation signal of the modulation signal output unit are provided.

(Operation of the present invention) As described above, the flow rate and pressure output from the electromagnetic on / off valve are detected, the deviation between the target value and the detected value is calculated, and the deviation is integrated to output the control signal. Therefore, when the actual control amount does not reach the target control amount, the modulation rate of the modulation signal is controlled until the target control amount is reached.

(Effect of the present invention) Since the modulation rate is controlled by the integrated value of the deviation as described above, whether the actual control amount reaches the target control amount even if there is a response delay in the electromagnetic on / off valve. Since the modulation signal is output based on whether or not it is a reference, the target control amount can always be secured.

That is, the modulation rate corresponding to the target control amount is the constant value η _ON
Even if it is less than or equal to or more than η _OFF , the control is not disabled as in the conventional case. Also, the above constant value η _ON
Since control is possible even below or above η _OFF , high-speed response can be realized by increasing the modulation frequency.

Further, as described above, the actual control amount is fed back to obtain the deviation from the target control amount, so that even if disturbance such as pressure fluctuation of the hydraulic power source occurs, the actual value can be immediately corrected. , It becomes strong against the disturbance.

(Embodiment of the present invention) The apparatus of FIG. 1 shown as an embodiment is provided with a target signal generator 7 for generating an apparent target signal Vr for a required flow rate, and the output of this target signal generator 7 The signal is input to the adder / subtractor 8, which includes a flow rate detector.
Input 10 output signals. Then, this flow rate detection unit 10
Detects the control flow rate to be controlled by the electromagnetic on / off valve 9 and outputs the flow rate signal V ₀ .

In the addition / subtraction unit 8 to which both signals are input as described above, the deviation e = (Vr-V ₀ ) of both signals is calculated, and the deviation signal e is input to the deviation integration unit 11.
Is an integrator that integrates the deviation of each modulation cycle.
11a and an adder 11b for adding the integration result.

The integrated addition value Vs output from the addition unit 11b of the deviation integration unit 11 as described above is input to the high pulse number calculation unit 12, and the high pulse number calculation unit 12 includes, for each cycle of the integration unit 11a. The deviation integrated value ΔVs and the signal from the first counter 13 are also input.

The first counter 13 counts the basic clock of the clock signal generator 14 and outputs the clock signal at each modulation cycle. The basic clock has a cycle sufficiently shorter than the modulation cycle.

In this way, the high pulse number calculation unit 12 to which the output signals of the deviation integration unit 11 and the first counter 13 are input outputs a timing signal to each of the second counter 15 and the modulation signal output unit 16.

Next, the operation of the apparatus having the above configuration will be described.

First, an apparent target signal Vr for the required flow rate is output from the target signal generation unit 7 and input to the addition / subtraction unit 8, and the flow rate signal V ₀ from the flow rate detection unit 10 is input to the addition / subtraction unit 8. In the adder / subtractor 8, the deviation e of both signals e = (Vr-V
₀ ) is calculated, and the deviation signal e is input to the deviation integrator 11.

In the deviation integration unit 11, the integration unit 11a integrates the deviation for each cycle, and the integration signal ΔVs is added to the addition unit.
Input to both 11b and high pulse number calculation unit 12. Then, the adder 11b adds the integrated signal ΔVs and inputs the added signal Vs to the high pulse number calculator 12.

The high pulse number calculation unit 12 to which both signals ΔVs and Vs are input,
It operates when the clock signal of the first counter 13 is input. In other words, how many pulses should be kept at the high level while counting the number of pulses in the basic clock of the clock signal generator 14,
The calculation is performed according to the values of the integrated signals ΔVs and Vs. And
The high pulse number calculation unit 12 calculates the number of pulses as described above, and the designated pulse number as a result is calculated by the second counter 15
To the second counter 15 and the modulation signal output section 16 while transmitting the timing signal.

The second counter 15, which has received the timing signal of the high pulse number calculation unit 12, starts counting the basic clock number when the timing signal is input, and outputs a predetermined signal when the designated pulse number has been counted.

The modulation signal output unit 16 continues to output a high level modulation signal from the timing signal input from the high pulse number calculation unit 12 until the count end signal of the second counter 15 is input. When the count end signal is input, a low level modulation signal is output.

The modulated signal output in this way is fed to the power amplifier 17
It is amplified by and input to the electromagnetic on / off valve 9.

Since the actual flow rate V ₀ is fed back as described above, and the modulation rate of the modulation signal is controlled by integrating the deviation between the flow rate V ₀ and the target signal Vr, for example, the apparent modulation rate is Even if η _ON or less or η _OFF or more,
The modulation rate is automatically changed until the predetermined flow rate is obtained. Therefore, the apparent modulation factor is a constant value η
_Even if the flow rate is set to _ON or less or η _OFF or more,
It becomes possible to control it, and the flow rate signal V ₀ is the target signal.
It has a linear relationship with Vr, and the control area becomes wider accordingly.

Further, since the control area can be widened as described above, it is also possible to realize a high-speed response by increasing the modulation frequency of the modulation signal.

Further, since the actual flow rate output from the electromagnetic on / off valve is fed back to calculate the deviation from the target flow rate and control is performed so as to fill the deviation, for example, even if there is a disturbance such as pressure fluctuation of the hydraulic power source, Its precise control becomes possible.

In the above embodiment, the deviation integrated value ΔVs for each cycle is input to the high pulse number calculating section 12, but the rate of change in deviation for each cycle is input to the high pulse number calculating section 12 in advance. Then, the control characteristics are improved. Therefore, when it is sufficient to input only the signal Vs from the addition unit 11b to the high pulse number calculation unit 12, the integration unit 11a of the deviation integration unit 11 and the addition unit 11b may be integrated.

Further, in the above-described embodiment, the pulse number calculation unit 12 calculates during the counting of high pulses, but it is of course possible to calculate during the counting of low pulses.

Further, in the above-described embodiment, the flow rate actually output is compared with the target flow rate, but the control mode that compares the pressure actually output with the target pressure and fills those deviations In this case, the device can be used as a pressure control device.

[Brief description of drawings]

FIG. 1 is a block diagram of a control circuit showing an embodiment of the present invention, FIGS. 2 to 4 show a conventional device, FIG. 2 is a block diagram, FIG. 3 is a time chart diagram, and FIG. 6 is a graph showing the relationship between the modulation rate of the modulation signal and the flow rate characteristic. 7 ... Target signal generation section, 8 ... Addition / subtraction section, 9 ... Electromagnetic on / off valve, 10 ... Flow rate detection section, 11 ... Deviation integration section, 12 ...
... High pulse number calculation unit, 13 ... first counter, 14 ... clock signal generation unit, 15 ... second counter, 16 ... modulation signal output unit.

Claims (1)

[Claims] 1. A control amount detecting section for detecting an output control amount and outputting a signal according to the control amount, and a target signal generating section for outputting a signal according to the target control amount.
An adder / subtractor that calculates the deviation between the signal from the target signal generator and the signal from the control amount detector, an integrator that integrates the deviation output from the adder / subtractor, and a cycle that is sufficiently shorter than the modulation cycle. And a clock signal generator that outputs the basic clock signal, and a first clock that counts the basic clock of the clock signal generator and outputs the clock signal at each modulation cycle.
A counter and a pulse number calculator for calculating whether the modulation signal is kept at a high level or a low level when the clock signal of the first counter is input, and the pulse number calculator A second counter that operates by the output timing signal to start counting the number of basic clocks from the clock signal generator, and outputs a signal when counting the specified number of pulses output from the pulse calculator; The modulation signal is kept at a high level or a low level until the count end signal from the second counter is input after the timing signal from the pulse number calculation unit is input, and a low level is input after the count end signal is input. Alternatively, the modulation signal output section that outputs a high-level modulation signal and the modulation signal output section Flip and flow control apparatus and an electromagnetic on-off valve for on-off operation.