JPH0782361B2 - Electro-hydraulic servo type material testing machine - Google Patents

Description

The present invention relates to a control circuit in a measuring instrument such as an electrohydraulic servo type material testing machine.

B. Conventional technology An electro-hydraulic servo-type material testing machine that controls the servo valve to feed back the load input actuator according to the deviation signal between the target load set value and the load feedback amount is the initial load input actuator. It has a sub-control circuit capable of commanding the position separately from the feedback control system. As this type of sub-control circuit, the one shown in FIG. 2 has been conventionally provided. In the feedback control system shown in FIG.
Is an addition point, 32 is an amplifier that amplifies the load deviation ε,
34 is a servo amplifier, 41 is a servo valve, 42 is an actuator for applying a predetermined load to the sample 35, and 36 is a load amplifier for amplifying the input load to the sample 35 detected by the load cell 43. A main feedback circuit is configured by these respective elements. The conventional sub-control circuit includes a stroke amplifier 37 that amplifies the displacement of the actuator 42 detected by the piston displacement meter 44, a sub-control knob 38 that sets the displacement of the actuator 42, and these stroke amplifier 37 and sub-control knobs. Addition point of 38 output signals 39
And a sub-control switch 40 for adding the deviation at to the summing point 33 in the main feedback circuit.

Then, explaining the operation in the case of three-point bending,
Prior to the main test, the switch 40 is turned on to enter the sub-control mode, and the set load is zero in this state. Now, the actuator 42 is
Since the output signal of the load amplifier 36 is zero when the contact is not made, the deviation ε and the output voltage E _{1 of the} amplifier 33 are also zero. Therefore, the actuator 42 freely moves according to the control amount of the sub control knob 38, and its displacement is feedback-controlled by the loop of the piston displacement meter 44, the stroke amplifier 37 and the sub control switch 40. Then, when the actuator 42 is brought into contact with the sample 35, a load is applied to the sample 35, and the load cell 43 detects this load and sends a load signal to the addition point 31 via the load amplifier 36. As a result, the amplifier 32 amplifies the deviation ε and outputs the voltage E ₁ , and controls so as to reduce the load on the sample 35, that is, to move the actuator 42 away from the sample 35.

On the other hand, in the sub-control circuit, since the displacement of the actuator 42 is limited by the contact with the sample 35, the output signal of the stroke amplifier 37 cannot follow the set value of the sub-control knob 38.
E ₂ is the increasing direction, that is, the actuator 42
It changes in the direction to press it against 35.

In this way, when the actuator 42 comes into contact with the test piece 35, it is in equilibrium that the absolute values of the voltages E ₁ and E ₂ are equal to each other by the respective feedback systems, and the test piece 35 is in a state where a predetermined load is applied in equilibrium. Become.

At this time, a non-linear element for the control amount of the sub-control knob 38 is inserted in the feedback loop of the sub-control circuit so that the test piece 35 is not overloaded.

Then, the switch 40 is turned off to disconnect the sub control circuit from the main feedback control system to obtain the initial state.

C. Problems to be Solved by the Invention However, in a so-called three-point bending test as shown in FIG. 3, the initial state is set while the actuator 42 is slightly applying a compressive load to the sample 35. However, in the conventional sub-control circuit described above, the voltage E ₂ becomes zero when the switch 40 is opened, and the voltage E ₁ becomes zero under the action of the main feedback control circuit, that is, The load becomes zero and the load fluctuates.

Particularly, in the case of a small and lightweight test piece such as a ceramic test piece, the setting position may shift when the initial load becomes zero, and in that case, complicated work such as resetting is necessary.

An object of the present invention is to provide a control circuit for a measuring device that solves such a problem.

D. Means for Solving Problems In order to solve such a problem, the present invention provides a feedback control system for controlling a load actuator with a deviation signal between a target load set value and a load feedback amount, and this feedback control. In an electro-hydraulic servo type material testing machine provided with a sub-control circuit for controlling the initial position of the actuator separately from the system, the sub-control circuit controls the actuator according to the deviation signal between the initial position set value and the position feedback amount. A control system for controlling, command means for commanding the initial position, switching means for disconnecting the command means from a sub-control circuit, and storage means for storing a signal corresponding to the command from the command means, Addition of the output of the storage means and the deviation signal and supply to the control operation unit Which has a stage, directing the initial position of the actuator,
The load control is performed by the feedback control system after the initial load is generated in the test piece.

E. Action When the command means is connected to the feedback control system by the switching means and the input amount is commanded from the command means, a signal corresponding to the command is supplied to the addition point. If the set value is zero and the measured physical quantity is zero, the deviation signal of the feedback control system supplied to the addition point is zero, and the physical quantity is increased or decreased according to the input quantity from the command means.
When the command means and the feedback control system are separated by the switching means, the output signal from the storage means in which the input amount by the command means is stored is added with the deviation signal by the adding means, and the signal is sent to the control operation unit. It is supplied and the control operation unit is controlled.

F. Embodiment An embodiment in which the present invention is applied to a sub-control circuit of an electrohydraulic servo type material testing machine will be described below with reference to the drawings. FIG. 1 is a block diagram of a feedback control system using the present invention. In FIG. 1, 11 is a point of addition of a target load set value and load which is a load feedback amount, and 12 is a deviation ε from the point of addition 11. The amplifier which amplifies is shown.
A servo amplifier 14 and a servo valve 21 are connected to the output side of the amplifier 12 via an addition point 13, and oil whose flow rate is controlled by the servo valve 21 is supplied to a load input actuator 22 to move it. Then, a predetermined load is applied to the sample 15. Actuator
The load applied to 22, that is, the reaction force of the load from the sample 15 is detected by the load cell 23 and applied to the load amplifier 16, and the output terminal of this load amplifier 16 is the addition point 11
And a well-known feedback loop is constructed. Here, this feedback loop is called a main feedback circuit.

Therefore, the sub-control circuit according to the present invention is provided between the output side of the displacement meter 24 and the addition point 13, and the stroke amplifier 1 for amplifying the displacement of the actuator 22 detected by the piston displacement meter 24. comparator
2, a sub-control knob 3, a clock oscillator 4, AND gates 5 to 8, an up-down counter 9 capable of battery backup, a DA converter 10 and a sub-control switch S. That is, the output terminal of the displacement gauge 24 is connected to the comparator 2 via the stroke amplifier 1.
The non-inverting input terminal of the comparator 2 is connected to the sub-control knob 3, and its output terminal is connected to one input terminal of the AND gate 5 and the inverting input terminal of the AND gate 6. Each is connected. The clock pulse from the clock oscillator 4 is input to the other input terminal of each of the AND gates 5 and 6, and these output terminals are connected to the respective input terminals of the AND gates 7 and 8, respectively. The other inverting input terminals of the AND gates 7 and 8 are grounded via the sub control switch S.

Further, the output terminal of the AND gate 7 is connected to the up count terminal of the up / down counter 9, and the output terminal of the AND gate 8 is connected to the down count terminal of the up / down counter 9. The output terminal of the up / down counter 9 is connected to the DA converter 10, and the output terminal thereof is connected to the adding point 13. Where D-A
As the converter 10, a converter that can take both positive and negative values is used, and outputs positive and negative signals according to positive and negative counts with the reference zero point of the up / down counter 9 as a boundary. The up / down counter 9 is reset when the power is turned on.

Here, the knob 3 constitutes the command means, the switch S constitutes the switching means, the up / down counter 9 constitutes the storage means, and the addition point 13 constitutes the addition means. Also, the displacement of the actuator 22 is a physical quantity, the servo valve 21 is the control operation unit,
The input position signal to 21 is the input quantity.

The operation of setting the actuator 22 on the test piece 15 using the sub-control circuit configured as described above will be described by taking a three-point bending test as an example.

First, when the electric control circuit is powered on, the up / down counter 9 is reset. Next, while confirming the output of the comparator 2 with a meter (not shown), the knob 3 is operated until the output of the comparator 2 becomes substantially zero. In that state, the hydraulic circuit is turned on and the switch S is closed. After that, when the actuator 22 is moved toward the sample 15 by the knob 3, the comparator 2 outputs the "L" level signal at first, so the up / down operation is performed. The counter 9 counts down, and the DA converter 10 outputs a negative position signal E ₂ . When this negative position signal E ₂ is supplied to the servo valve 21 via the servo amplifier 14, oil is supplied from the servo valve 21 to the actuator 22 in a direction in which the actuator 22 approaches the sample 15. Then, when the output of the stroke amplifier 1 becomes larger than the output from the knob 3, the comparator 2 outputs an "H" level signal, so the up / down counter 9 counts up, and the negative position signal E ₂ approaches zero, and the actuator moves. When the speed of 22 decreases and the up / down counter 9 further counts up, the position signal E ₂ becomes positive, and the actuator 22 moves in the direction away from the sample 15.

Through the above operation, the actuator 22
When contacted with a predetermined contact load, the up / down counter 9 outputs a negative count value corresponding to the operation position of the knob 3 at that time. Then, when the switch S is opened to disconnect the sub control circuit from the main feedback control system, the count value of the up / down counter 9 is stored as it is, and a predetermined negative position signal E ₂ is transmitted to the DA converter 10.
Is input to the summing point 13. Therefore, even if the main feedback control system operates and the deviation signal E ₁ becomes a positive value, the signal input to the servo valve 21 via the servo amplifier 14 becomes zero and the actuator 22 holds and holds the same position. The contact load on the sample 15 by the actuator 22 does not change.

In the above, the value corresponding to the operation amount of the knob 3 is stored in the up / down counter 9, and the sub control switch S
A predetermined signal E ₂ is applied to the summing point 13 by the count value of the up / down counter 9 when is opened. However, as shown in FIG. 4, for example, as shown in FIG. Knob 3 with means 50 and switch 51
And the switch S in parallel, and in response to the switch S being opened, the switch 51 is closed, whereby a preset output signal is added to the storage means 50 and a signal E ₂ is added to the summing point.
You may give as. Further, the present invention can be applied to a measuring instrument having a feedback control system as described above other than the material testing machine.

G. Effects of the Invention As described in detail above, according to the present invention, even after the command means is disconnected from the feedback control system, the addition means is supplied with the predetermined signal from the storage means, and therefore the deviation signal is generated. There is no fear of fluctuation and complicated work is unnecessary. Especially, if the present invention is applied to an electrohydraulic servo type material testing machine, fluctuation of the initial load applied to the test piece by the command means is prevented, and the test piece is prevented. This eliminates the need for complicated work such as resetting, reduces the burden on the operator, and is extremely effective in automating the test.

[Brief description of drawings]

FIG. 1 is a block diagram of a feedback control system of an electrohydraulic servo type material testing machine using the present invention, and FIG. 2 is a block diagram of a feedback control system of an electrohydraulic servo type material testing machine equipped with a conventional sub-control circuit. 3, FIG. 3 is an explanatory diagram of a three-point bending test, and FIG. 4 is a circuit diagram of a main part showing another example of the sub-control circuit. 1: Stroke amplifier, 2: Comparator 3: Sub-control knob 4: Clock oscillator 5-8: AND gate 9: Up / down counter 10: DA converter S, 51: Sub-control switch 11, 13: Addition point, 12 : Amplifier 14: Servo amplifier and actuator 15: Specimen, 16: Load amplifier 50: Storage means

Claims (1)

[Claims] 1. A feedback control system for controlling a load actuator according to a deviation signal between a target load set value and a load feedback amount, and a sub-control circuit for controlling an initial position of the actuator separately from the feedback control system. In the electro-hydraulic servo type material testing machine, the sub-control circuit is a control system for controlling an actuator according to a deviation signal between an initial position set value and a position feedback amount, and a command means for instructing the initial position. A switching means for disconnecting the command means from the sub-control circuit, a memory means for storing a signal corresponding to the command from the command means, and an output of the memory means and the deviation signal for a control operation section. And an adding means for supplying the same and indicating the initial position of the actuator. The electro-hydraulic servo type material testing machine is characterized in that the load is controlled by the feedback control system after an initial load is generated on the test piece.