JPH11119838A - Noise elimination device for pwm-controlled fluid pressure driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the noises generated by a fluid pressure driver with a simple constitution, by adding a noise reduction carrier mixer to a servo amplifier and superposing a noise reduction carrier having a frequency higher than the audible frequency on a command signal. SOLUTION: A command signal 100 is supplied to an input terminal 14a of a servo amplifier 14 and then sent to a PWM amplifier 17 via an adder 15 and subtracter 16. Then, a PWM control signal is supplied to an exciting coil 13 from the amplifier 17. A sine wave oscillation circuit 20 is added to the amplifier 14, and a noise reduction carrier mixer consists of the circuit 20 and the adder 15. The oscillation output of the circuit 20 outputs a sine wave signal having the frequency higher than the audible frequency, and a noise reduction carrier 200 is superposed on the signal 100 via the adder 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved noise reduction apparatus for a PWM-controlled fluid pressure driving apparatus, and more particularly to an improvement for reducing the occurrence of high-frequency noise in a direct-acting valve for controlling various driving apparatuses using hydraulic pressure or air pressure. Related to a noise removing device.

[0002]

2. Description of the Related Art A device for driving various large loads by using fluid pressure such as hydraulic pressure or air pressure has been put into practical use. In recent fluid pressure drive devices, a proportional control valve, a direct-acting type servo, and the like are used as control valves. Valves are used, and these control valves are set to P
By performing WM control, high-speed and highly responsive drive control can be realized.

In this type of fluid pressure driving device, a PW
High-frequency noise is likely to occur in a control valve or the like at the time of M control, which has been a serious problem in various applications requiring quietness. For example, when this type of fluid pressure driving device is used for driving a movable floor, a rotating floor, or a hanging curtain such as a theater or a concert hall, the generation of the noise causes a great obstacle.

Conventionally, as a countermeasure against such noise, the control valve itself, which is a noise generating source, has been sealed with a soundproof shield. However, such a noise shield device increases the overall structure. Also, it was impossible to provide complete noise shielding, and this was not a fundamental solution.

As another conventional noise removing method,
There has been a method of substantially solving the noise problem by setting the PWM control frequency in a high frequency region exceeding the audible frequency.

Normally, a high frequency range of 20 KHz or more exceeds a human audible range.
If z is greater than or equal to z, in most cases, noise is not recognized, and substantial noise countermeasures have been taken.

However, in order to make the PWM frequency in the high frequency region, a high-speed and large-capacity transistor (FET) is required, and there is a problem that the device becomes expensive. In a general PWM drive type control valve, a control position is detected by an LVDT (Linear Variable Differential Transformer) or the like, and this is fed back to a servo amplifier to perform accurate position control. And L at this time
The excitation frequency of VDT is also one of noise sources,
There is a problem that the M frequency and the LVDT frequency generate beats with each other, and this beat frequency and frequency noise that is an integral multiple of the beat frequency are generated.

For this reason, in the conventional device, a notch filter is provided for each frequency of the actual noise source for each individual driving device, and the sound pressure level of the noise frequency is reduced by the notch filter. I was

[0009]

However, such a notch filter is required for each noise source, and it is necessary to adjust the filter frequency to match the frequency of each noise source. There were various drawbacks that it was troublesome.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an improved noise elimination device capable of remarkably reducing noise generated by a fluid pressure driving device with a simple structure. It is in.

[0011]

In order to achieve the above object, the present invention provides a noise reduction carrier mixer provided in a servo amplifier for supplying a PWM control signal to a PWM drive control valve. A noise reduction carrier having an oscillating frequency exceeding the audible frequency is given to the command signal from the device, and the command signal is superimposed to drive the PWM drive type control valve, thereby effectively removing noise in the audible frequency range. And

[0012]

FIG. 1 shows a preferred embodiment of a fluid pressure driving device according to the present invention. In the figure,
Although a rotary floor drive device such as a stage device to be controlled is not shown in itself, a PWM drive type control valve for controlling a fluid pressure supplied to such a drive device is indicated by reference numeral 10. The control valve 10 is a general-purpose direct-acting valve,
The fluid pressure supplied from the fluid source through the flow path 12a is guided to one of the two flow paths 12b and 12c by the plunger valve 11 which moves in the cylinder in the left-right direction, and a predetermined fluid pressure is supplied to the driving device. be able to. The flow path 1
2d forms an open channel of the atmosphere. Plunger valve 1
An exciter coil 13 is provided at the left end of the plunger valve 11 for moving the plunger 1 in the left-right direction.
A WM control signal is provided.

A command signal 100 is supplied to an input terminal 14a of the servo amplifier 14, and the command signal 100 is
5 and to the PWM amplifier 17 via the subtractor 16,
The PWM control signal is output from the WM amplifier 17 to the exciting coil 1.
3. The control valve 10 includes a plunger valve 11.
LVDT 18 is provided to detect the position of
The DT position detection signal is fed back to the LVDT amplifier 19 of the servo amplifier 14, and this position signal is
In this case, the driving position of the driving device can be accurately feedback-controlled by comparison with the command signal 100.

A feature of the present invention is that the command signal 1
The noise reduction carrier is superimposed on the sine wave oscillation circuit 2 in the embodiment.
0 is provided, and the sine wave oscillation circuit 20 and the adder 15 form a noise reduction carrier mixer. The oscillation output of the oscillation circuit 20 outputs a sine wave signal having an oscillation frequency exceeding the audible frequency.
0 is superimposed by the adder 15. It is preferable that the noise reduction carrier 200 has an oscillation frequency higher than the audible frequency, which is usually 20 kHz or higher, but in the embodiment, an effective noise removing effect can be obtained if the frequency is 13 kHz or higher.

FIG. 2 shows a specific circuit configuration of the PWM amplifier 17 described above. In the figure, four transistors TR1, TR2, T
R3 and TR4 are bridge-connected. Therefore,
By supplying the PWM control signal sequentially to the base of each transistor in a combination of TR1, TR4 and TR2, TR3, forward and reverse currents can be applied to the exciting coil 13. When the PWM control signal is driven in a high frequency band, a pulse current having a small width is applied to the excitation coil 13, but in reality, a smooth current is integrated by the inductance of the excitation coil 13 and a smooth current is applied. It becomes the exciting current of the coil. However, a part of the high-frequency component remains, and this causes noise such as a control valve in the drive unit. Theoretically, such noise can be significantly reduced if each transistor is simultaneously turned on and off with the same characteristics. However, in practice, the zero-point dead band of each transistor varies, or there is a difference in the rise at the time of ON operation. In some cases, a noise-like signal is generated, which is perceived as noise of a control valve or the like.

In the present invention, since the noise reduction carrier 200 is superimposed on the command signal 100 as described above, each of the transistors TR1, TR2, TR
3. TR4 is always in an operating state near its zero-point operation, eliminating the non-linear elements due to the above-mentioned characteristic variations, making it difficult to generate a noise-like PWM control signal, and thereby significantly reducing noise in control valves and the like. Becomes

FIGS. 3 and 4 show the noise reduction effect of the fluid pressure driving device according to the present invention. FIG. 3 shows a noise frequency characteristic in a conventional fluid drive device without a noise reduction carrier mixer. The horizontal axis indicates frequency, and the vertical axis indicates noise level.

As apparent from FIG. 3, PWM noise is generated at a frequency around 15 KHz, and 6.5.
At a frequency around KHz, large LVDT noise occurs.

FIG. 4 shows the noise frequency characteristics measured with the noise reduction carrier mixer provided in the above-described embodiment of the present invention. A large noise is generated at 20 KHz which is the frequency of the noise reduction carrier. PWM noise and LVDT appearing in FIG.
It is understood that noise is almost completely eliminated. Also, by comparing FIG. 3 and FIG. 4, it is understood that the overall noise level is reduced by several decibels,
It is understood that the effect of noise reduction in the audible frequency range is remarkable according to the present invention.

In the present invention, the noise reduction carrier is implemented by a sine wave signal in the embodiment, but the carrier waveform may be a triangular wave or a step wave.

[0021]

As described above, according to the present invention,
A noise reduction carrier mixer is provided in the servo amplifier of the fluid pressure drive device under PWM control, and noise in the audio frequency range is easily reduced by superimposing a noise reduction carrier having an oscillation frequency exceeding the audio frequency on the command signal. This makes it possible to provide an extremely effective noise elimination device for applications requiring quietness.

Further, the noise reduction carrier in the present invention can have a constant frequency without depending on the noise frequency of the fluid pressure drive device or the PWM drive type control valve, and requires complicated adjustment and the like. There are no benefits.

According to the present invention, it is possible to provide a noise eliminator having a very simple structure which does not require an additional filter or the like for noise elimination.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a structure of a control valve and a servo amplifier of a PWM-controlled fluid pressure driving device incorporated in a noise elimination device according to the present invention.

FIG. 2 is a circuit diagram showing a specific configuration of a PWM amplifier of a servo amplifier embodying the present invention.

FIG. 3 is a noise frequency characteristic diagram in a conventional fluid pressure driving device.

FIG. 4 is a noise frequency characteristic diagram in the fluid pressure driving device embodying the present invention.

[Explanation of symbols]

10 PWM drive type control valve, 13 Excitation coil, 14
Servo amplifier, 15 adder, 17 PWM amplifier, 18
LVDT, 19 LVDT amplifier, 20 sine wave oscillation circuit, 100 command signal, 200 noise reduction carrier.

Claims (1)

[Claims] 1. A PWM controlled control valve for supplying a desired fluid pressure to a fluid pressure driving device, and a servo amplifier for supplying a PWM control signal to the control valve based on a desired command signal. A fluid pressure drive device, comprising: a noise reduction carrier mixer for superimposing a noise reduction carrier having an oscillation frequency exceeding an audible frequency on a command signal in the servo amplifier. Equipment noise removal device.