JPS5814564B2 - Servo Bennodaiza Seigiyosouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a dither control device for a servo valve, and more particularly to a dither control device for a servo valve that is most suitable for controlling a direct-acting servo valve used in a hydraulic system.

[Prior art]

FIG. 1 is an example of a conventional direct-acting hydraulic servo valve that drives a spool using a force smoke.

In Figure 1, the direct-acting servo valve includes a magnet assembly 1, a coil 2, a subur 3, a sleeve 4, a casing 5, a connector 6, coil springs 7a and 7b, a pump port 8, a cylinder port 9, a tank port 10, and a neutral It is composed of a point adjustment screw 11, a displacement meter core 12, a displacement meter fixture 13, and a displacement meter stem 14 (here, a displacement meter is used, but a speed meter may also be used).

). The force smoke section is composed of a magnet assembly 1 and a coil 2.

Further, the valve body portion includes a spool 3, a sleeve 4, and a casing 5.

If a positive voltage is applied to the coil 2 from the connector 6, the spool 3 overcomes the coil spring 7a and moves to the right in FIG. Flows to port 9.

Conversely, if a negative voltage is applied to the coil 2, the hydraulic oil returns from the cylinder port 9 to the tank port 10. The same is true for

). FIGS. 2a, b, and c show the relationship between the voltage (2) applied to the coil 2 and the state quantity (displacement amount will be dealt with hereinafter) S of the spool 3 in this case.

The displacement of the subur 3 when a low frequency (0.01 to 0.05 Hz) sinusoidal voltage -■o to +■o was applied to the coil 2 was recorded by an X-Y recorder.

FIG. 2a shows the relationship between the ideal applied voltage (2) and the displacement amount S of the spool 3 in the case where there is no frictional resistance between the spool 3 and the sleeve 4, and other factors.

FIG. 2b is a graph without dithering.

In this case, relatively large hysteresis (or deadb
and) exists.

This value may be 10 to 20% of the servo valve rating in some cases.
It can even extend to

Figure 2c is a relationship diagram when an appropriate amount of dither is added, and it is clear that hysteresis (or d
It can be seen that the band (ead band) is decreasing.

Here, the dither frequency is usually a sine wave of 200 to 1000 Hz, and the dither amount is about 5 to 20% of the rated voltage.

Figure 3a is shown to explain the above more specifically.
=d.

Figure 3a shows the sinusoidal voltage applied to the coil 2, Figure 3b shows the spool displacement without dithering, Figure 3c shows the spool displacement with dithering, and Figure 3d shows the spool displacement with dithering. The voltage waveforms applied to the coil 2 are shown in FIG.

The high frequency components in FIGS. 3c and 3d are caused by dithering, and the difference in the ratio is due to a decrease in gain (spool displacement) caused by the responsiveness of the servo valve.

However, the dither applied to the servo valve in the prior art has a large value (for example, the dither frequency is about 1000
z, the amount of dithering is about 20% of the rated voltage of the valve) is fixed and set in advance and applied to the servo valve.

The reason for this is that at the end of the servo valve's life, the spool and sleeve have considerably worn out, so if the applied dither value is too small, the dither will not work on the servo valve.
This is because the phenomenon that the servo valve spool sticks is avoided.

Therefore, even if a servo valve has just been installed, an excessive amount of dither (approximately 10 μ in spool movement) corresponding to the end of its life is always applied to the servo valve, resulting in excessive dithering. This resulted in excessive wear between the spool and the sleeve of the servo valve by an amount equivalent to the amount, which resulted in a disadvantage that the life of the servo valve was further shortened.

[Purpose of the invention]

An object of the present invention is to apply a dither value to a servo valve so that it always becomes an appropriate value over time, thereby suppressing the progress of abnormal wear between the spool and sleeve of the servo valve. An object of the present invention is to provide a dither control device for a servo valve that makes it possible to extend the life of the servo valve.

[Structure of the invention]

The features of the present invention include a servo valve that is controlled by adding dither, a spool state quantity detector that detects at least one spool state quantity of the servo valve, and a spool state quantity detector that detects at least one spool state quantity of the servo valve; A dither state quantity detector extracts only the dither state quantity of the spool, and the dither state quantity of the spool extracted by the dither state quantity detector is compared with a predetermined setting value, and based on the comparison result, the above-mentioned A dither control device for a servo valve includes an arithmetic device that calculates the amount of dither that needs to be added or reduced and inputs the calculated amount to a dither setting device.

According to the above configuration, only the amount of dither actually applied to the spool of the servo valve is extracted by the dither state amount detector from the detection signal detected by the spool state amount detector of the servo valve. The amount of dither is compared with a predetermined value determined in advance by the calculation device, and the amount of dither that needs to be added or reduced is calculated based on the comparison result, and this calculated amount of dither is constantly input into the dither setting device. This makes it possible to automatically apply an appropriate amount of dither to the servo valve over time.

〔Effect of the invention〕

According to the present invention, since the amount of dithering applied to the servo valve is always maintained at an optimal value over time, the progress of abnormal wear between the spool and the sleeve is suppressed, and as a result, the control accuracy of the servo valve is This has the effect of improving.

[Embodiments of the invention]

FIG. 4 is a block diagram illustrating an example of a displacement meter as a state quantity detector used in a dither control device for a servo valve according to an embodiment of the present invention.

In FIG. 4, the position servo valve includes a jack consisting of a ram 15a and a cylinder 15b, a servo valve 16 for controlling the oil amount, a servo power amplifier 17 and a servo preamplifier 18 for driving it, and a positioning jack. It is composed of a ram displacement gauge 19 and a setting device 20 for setting its position.

The objects of the present invention are the spool displacement meter 21, the filter 22, the full-wave rectifier 23, the smoothing circuit 24, the amplifier 25,
This section is composed of a dither setting device 26, a reference power source 27, an operational amplifier 28, a comparator 29, a display 30, and a comparator 31, and controls the amount of dither.

The operation of the embodiment of the present invention with the above configuration will be described below.

In a state in which a normal position servo valve is configured, first of all, if the dither level necessary for the operation of the servo valve 16 is set as an initial value by the setting device 26, then the dither level setting value is used for calculation to apply dither to the servo valve 16. A dither amount corresponding to the dither level set value is inputted to an amplifier 28, and a dither amount corresponding to the dither level setting value is applied from the operational amplifier 28 to the servo power amplifier 17 by the voltage of the reference power supply 27, and the servo valve 16 is driven back and forth to apply dither.

In the dither setting device 26, the dither level is set using the frequency and voltage level, but the frequency is usually 3 to 5 times the response frequency of the servo valve (if the frequency response is 60 Hz, the dither frequency is 180 to 5 times). 300H
z), and the voltage level is set to a value confirmed in advance through tests etc. (Usually, for servo valves, the rated voltage or current of the valve is
~10%).

In this case, the amount of movement of the servo valve's spool due to dithering will be kept to about 2 to 3 microns, and abnormal acceleration of wear will be prevented.

The displacement amount, which is the spool state amount at this time, is taken out as an electric signal by the displacement meter 21.

This electric signal is passed through a filter 22, and further through a full-wave rectifier 23, a smoothing circuit 24, and an amplifier 25 to output the amount of spool displacement caused by the dither, that is, the dither actually applied to the spool. Extract the amount as a DC component.

Then, the value of the DC component, which is the actually measured amount of dither, and the value of the dither setter 26 are compared by the comparator 31, and the deviation between the two is calculated.

Then, a dither signal corresponding to the deviation after this calculation is newly given to the operational amplifier 28 as a dither amount correction signal, or inputted for reduction.

That is, the deviation signal which is the calculation output of the comparator 31 is input to the operational amplifier 28 together with the setting signal from the dither setting device 26.

Therefore, when the deviation signal, which is the calculation result of the comparator 31, is positive, the operational amplifier 28 increases the output because it is added to the dither setting signal from the dither setting device 26, and when it is negative, it is subtracted from the dither setting signal. It is configured so that the output is small.

Therefore, an output signal corresponding to the result of the operation is sent to the operational amplifier 28.
This will be obtained by

This output signal is added to the output signal of the servo amplifier 18 and input to the servo power amplifier 17.

A servo valve drive output corresponding to this input signal is taken out to a servo power amplifier 17 to control the servo valve 16.

Note that the setting value of the dither amount in the dither setting device 26 is reset so that the frequency and voltage thereof are increased sequentially in accordance with the aging of the servo valve.

The above calculations are always performed while the servo valve 16 is in operation, and the required dither amount is automatically controlled.

Alternatively, the comparison calculator 29 may calculate the deviation between the output voltage of the operational amplifier 28 and the reference signal Da, and if the result exceeds a predetermined value, the display 30 may issue an alarm.

FIGS. 5a to 5d show specific examples of the above control.

This will be explained further. FIG. 5a is a graph showing the output voltage of the spool displacement meter 21 when a certain arbitrary amount of dither is added when the spool is operating with a sine wave.

FIG. 5b is a graph showing the result of extracting only the dither frequency component from the output graph of FIG. 5a using the filter 22. FIG.

FIG. 5c shows a waveform after passing through the full-wave rectifier 23.

FIG. 5d shows the result after passing through the smoothing circuit 24.

The present invention constantly detects the average voltage DM representing the amount of dither actually applied in this case, and controls the amount of dither based on comparison with a set value so that an appropriate amount of dither is always applied. It is something.

As described above, the servo valve dither control device automatically controls the dither amount necessary for the normal operation of the servo valve to an optimum value over time, thereby extending the life of the servo valve by reducing wear on the spool and sleeve. This makes it possible to prevent long-term damage and sudden breakdowns due to galling.

In the embodiment of the present invention, a displacement meter is used as a state quantity detector to detect the dither effect, but a speed meter can also be used in addition to the displacement meter.

In this case, it is particularly effective to use a speed meter when a differential transformer is used as the displacement meter and responsiveness and noise are a problem.

Further, in the embodiments of the present invention, a case has been described in which the dither frequency is fixed and its amount (voltage) is controlled, but it is also possible to conversely fix the amount and control the dither frequency.

Of course, although the control process becomes slightly more complicated, it is also possible to perform control by incorporating both quantity and frequency.

In this case, it is possible to determine the dither amount with higher precision even when accurate tracking is not possible using only the amount and frequency.

In order to realize each of these embodiments, it is only necessary to perform frequency processing on the component that processes the quantity, or to add a component to process the relationship between the two.

In the embodiments of the present invention, only direct-acting hydraulic servo valves have been dealt with, but the invention is not limited to this, as long as the spool has a dither effect as a displacement or speed as its state quantity.
It can be applied to any servo valve and control valve (for example, when controlling the main spool of a servo valve such as a nozzle flapper and jet pipe type, or the pilot or main spool dither of a pilot spool type servo valve, etc.) It is.

).

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional direct-acting servo valve, Figure 2a
is a diagram showing the relationship between the coil applied voltage and the spool displacement amount, Figure 2 b is a diagram showing the relationship between the coil applied voltage and the spool displacement amount without dither, and Figure 2 c is a diagram showing the relationship between the coil applied voltage and the spool displacement amount when dither is added. Figure 3a is a waveform diagram showing an example of the applied voltage applied to the coil, and Figure 3b is the spool displacement when there is no dithering. Figure 3c is a diagram showing the spool displacement when dither is applied, Figure 3d is a voltage waveform diagram when dither is added and applied to the coil, and Figure 4 is an example of the present invention. A block diagram showing a dither control device for a certain servo valve, FIGS. 5a to 5d are diagrams showing operating waveforms of each part of the embodiment of FIG. 4. 16... Servo valve, 17... Servo power amplifier, 21... Spool state quantity detector,
22...Filter, 23...Full wave rectifier, 24...Smoothing circuit, 25...Amplifier, 26...Dither setting device, 27...
-Reference power supply, 28... operational amplifier.

Claims (1)

[Claims] 1. A servo valve that is controlled by adding dither, a spool state quantity detector that detects at least one spool state quantity of the servo valve, and only the dither state quantity of the spool caused by the dither from the detection signal of the detector. A dither state quantity detector that extracts the spool's dither state quantity extracted by the dither state quantity detector is compared with a predetermined setting value, and based on the comparison result, the above addition or reduction is necessary. 1. A dither control device for a servo valve, comprising a calculation device that calculates a dither amount and inputs the calculated amount to a dither setting device.