JPH0249403B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a positioning control method for an air actuator, and in particular to a method for quickly and accurately positioning an actuator by supplying pressurized air from an on/off control valve to the left and right working chambers of the actuator. This invention relates to an improved method for

[Prior Art] Devices that drive or position various devices using air pressure are well known and are used as pneumatic actuators in various industrial fields. These pneumatic actuators have traditionally been used mainly in industrial machinery, but in recent years they have been used in a wide range of fields, especially for controlling robots.
As a result, there is a demand for actuators that can perform quick and accurate positioning under more severe conditions than ever before.

A typical pneumatic actuator has a structure in which a predetermined pressure air is sent to the left and right working chambers using an on/off control valve, and the desired position is determined by the supply amount of this pressure air. Therefore, we achieved a positioning accuracy of less than 100μm,
Moreover, in order to perform a quick positioning action within a given movement range, it has been impossible to obtain the desired control action using a conventional relatively rough pneumatic actuator.

In the past, several improvements have been made to such pneumatic actuators to enable high-precision stop position control. For example, in Japanese Patent Application Laid-Open No. 174701/1983, a method was developed to predict the response delay of a solenoid valve in advance. However, a device has been proposed that controls the stopping of a hydraulic cylinder in accordance with a predetermined calculation result, and has been proposed in particular as a device that is expected to provide a positioning action without hunting, which is likely to occur with such a pneumatic actuator.

[Problems to be Solved by the Invention] However, even with such conventional devices, it is still not possible to achieve the desired high-precision positioning, and in particular, it is difficult to achieve the desired high-precision positioning. The problem was that it was not possible to achieve this quickly and with high responsiveness.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an improved positioning control method that can achieve both high-precision positioning and rapid drive action that were previously unobtainable with a simple configuration. It is about providing.

[Means for Solving the Problems] In order to achieve the above object, the first invention of the present invention separates the movement of the actuator into a high speed range and a low speed range, and performs area control until it reaches the vicinity of a desired target position. provides a sufficiently large initial driving force to move at high speed, and in a preset low speed range near the target position, the pressure in the left and right working chambers of the actuator is increased to bring the pressure in both working chambers almost to the source pressure. It is characterized by low-speed feeding while being held, thereby achieving highly accurate positioning.

In particular, in the first invention, the initial driving force in the high speed range is obtained by applying source pressure to one of the left and right working chambers while leaving the other working chamber in an open state to obtain the maximum high speed, and in the low speed range near the target position. In this case, the source pressure is continued to be applied to one working chamber while the other working chamber is gradually closed, thereby reducing the moving speed of the actuator in the low speed range and pressing the actuator from both sides with high pressure. It is characterized by being able to stop at any position,
As a result, the actuator is positioned at the desired target position with a large resistance against external disturbances.

Furthermore, in order to achieve the above object, the second invention of the present invention, in addition to the configuration of the first invention described above, sets a braking region before the low speed region, and in this braking region, the other working chamber The relief valve of the actuator is closed to apply a braking action to the actuator.

[Function] Therefore, according to the first aspect of the present invention, the movement of the actuator is performed under separate region control into a high-speed range and a low-speed range, and in the high-speed range, the other working chamber is kept open. By applying source pressure to one side of the working chamber, a sufficiently large initial driving force is applied to achieve high-speed movement, and when the target position is reached, the working chamber side, which had been open until then, gradually opens up. The pressure is increased and the actuator is controlled to move at a slow speed to a predetermined position as described above.

According to the first invention, when a predetermined position is obtained, a high pressure is applied to both working chambers, and when a new displacement is desired in this state, the movement from the current position is quickly performed. is started.

Further, according to the second aspect of the present invention, a braking region is set before the low speed region, and the actuator, which had been moving at a high speed until then, is decelerated in the braking region, and the actuator is moved at a low speed. is passed to the area control.

Therefore, according to the second invention, it is possible to achieve smooth speed control without overshoot.

[Embodiments] Preferred embodiments of the present invention will be described below based on the drawings.

Configuration of Air Actuator FIG. 1 shows an embodiment in which an air actuator according to the present invention is used to control the rotation angle of a butterfly valve, and the air actuator 10 to which the present invention is applied uses air pressure as a driving source. The reciprocating movement of the actuator 10 is achieved by a drive shaft 1 pivotally supported on a base 12.
4 to the butterfly valve 16, and the opening degree θ of the butterfly valve 16 is made to match the target value by reciprocating piston movement inside the actuator 10.

A pneumatic switching circuit including an on/off control valve to be described later is provided inside the air actuator 10, and the on/off control valve is controlled on/off by an electrical command signal from a control circuit block 18. has been done.

Furthermore, the device of this embodiment has the actuator 1
It includes a potentiometer 20 that is linked to the reciprocating motion of 0, and its controlled amount is detected as an electrical signal.

Figure 2 shows the actuator 1 in this embodiment.
0 and its pneumatic switching circuit 22, the pneumatic actuator 10 includes a piston 26 that reciprocates within a cylinder 24, and the reciprocating movement of the piston 26 is coupled to the aforementioned drive shaft via a lever 28. It has been converted into 14 rotations.

The pneumatic switching circuit 22 includes four on/off control valves V ₁ , V ₂ , V ₃ , V ₄ , each valve V having a ball valve that is spring-biased in a closed state relative to its valve seat. Each ball valve can be opened against the spring by applying an electrical excitation signal to the excitation coil.

The on/off control valves V ₁ , V ₂ are in communication with the supply source _PS , and the on/off control valves V ₃ , V ₄ are open to the outside E.

The outlet side C ₁ of the control valves V ₁ and V ₃ communicates with the left working chamber L of the actuator 10, and also controls the
Outlet sides C ₂ of V ₂ and V ₄ communicate with the right working chamber R of the actuator 10 .

Therefore, if each valve V ₁ , V ₂ , V ₃ , _{V 4} shown in the figure is opened from the closed state, the supply source pressure P _S will be increased to the left working chamber L.
is supplied to the right working chamber R of the actuator 10, and the piston 26 moves to the right. On the other hand, when the control valve _V2 is opened, the source pressure P _S is supplied to the right working chamber R of the actuator 10, and the piston 26 moves to the right.
will move to the left. Furthermore, opening the control valve _V3 opens the left working chamber L to the atmosphere, and also opens the control valve V3 to the atmosphere.
Opening _V4 opens the right working chamber R to the atmosphere.

FIG. 3 shows an electrical control circuit for the actuator 10 described above, in which a signal from the control circuit block 18 is supplied to each valve V of the pneumatic switching circuit 22, so that the pneumatic actuator 1
0 piston 26 moves. The amount of movement of the piston 26 is detected as an electrical signal by the potentiometer 20, and the amount of movement of the piston 26 is detected as an electrical signal by the potentiometer 20.
Feedback is given to 8.

The control circuit block 18 includes a CPU 30 that performs various calculations and controls, and the CPU 30 is supplied with various control data, and this control data includes a current position signal θ and a target position signal θ _A from the potentiometer 20. . The target position signal θ _A is converted into a voltage signal by a current-voltage converter 32, and then converted into a digital signal by an A/D converter 34, which is a parallel-to-serial converter (hereinafter referred to as a parallel-to-serial converter) 36.
The signal is supplied from the CPU 30 to the CPU 30.

Similarly, the current position signal θ from the potentiometer 20 is also sent to the A/D converter 34 and the parallel-to-serial converter 36.
is supplied to the CPU 30 via. The CPU 30 is supplied with various calculation setting values from the setting device 38, and calculates these settings, the current position signal θ, and the target position signal based on a predetermined calculation formula _θA ,
This is supplied from the buffer circuit 40 to a drive circuit 42, and an electrical on/off control signal from the drive circuit 42 is supplied to each valve V of the pneumatic switching circuit 22.

Actuator Control Method The pneumatic actuator to which the present invention is applied has the configuration roughly described above.The actuator 26 in FIG. 2 is moved rightward to move the drive shaft 14 of the butterfly valve 16 from the current position θ _i to the target position θ _A
We will explain the control action that moves quickly and accurately.

The target position θ _A is input to the control circuit block 18 as an external setting signal, and as described above, this setting signal is converted into a voltage signal and then read from the A/D converter 34 and parallel-to-serial converter 36 to the CPU 30. will be included.

A characteristic feature of the first aspect of the present invention is that the actuator control is performed in at least two stages, the first stage being a high-speed range to obtain a high-speed initial driving force, and the second stage being a high-speed range to obtain a high-speed initial driving force. is a low speed range in which the actuator is driven at low speed in the vicinity of the target position to control positioning at the correct position.

The low speed range is set in advance near the target position, and in the embodiment is set as a fixed range,
As is clear from the action explanatory diagram of FIG. 4, the low speed range is set at an angle θ ₁ minute on each side of the target position θ _A. As is clear from FIG. 3, this set angle θ ₁ is supplied from the setter 38 to the CPU 30 as a digital angle signal, and is preferably set, for example, between about 1 and 8 degrees.

In the present invention, when the low speed range is set as described above, the air actuator 10 is fed at high speed from its current position until reaching the low speed range,
In the present invention, this high-speed feeding is performed by the actuator 1.
The maximum initial driving force is obtained by applying supply source pressure P _S to one working chamber of 0 and keeping the other working chamber open. When the actuator reaches a low speed range, the supply pressure is applied to one working chamber while the relief valve of the other working chamber is partially closed, gradually bringing the pressure balance between the left and right working chambers closer to the desired target. Accurate positioning to position θ _A can be performed.

Furthermore, in the second aspect of the present invention, a braking area is provided between the high speed area and the low speed area so that the vehicle can be stopped in the shortest possible time.

That is, in the braking region of the embodiment, supply source pressure is supplied to one working chamber and the relief valve of the other working chamber is fully closed to perform braking, or at the same time supply source pressure is supplied to the other working chamber. By applying _PS , rapid braking is possible.

The detailed control action of this embodiment will be explained below using the action explanatory diagrams of FIGS. 4 and 5.

At time 0, when the target position signal θ _A is input to the control circuit block 18, the actuator 10 acts to rotate the drive shaft 14 of the butterfly valve 16 clockwise, as shown in FIG. Therefore, in the high speed range from time 0 to _t1 position, on/off control valves _V1 and _V4 are opened and control valves _V2 and _V3 are closed, as shown in FIG.

Therefore, in this high speed range, the supply source pressure P _S is applied from the control valve V ₁ to the left working chamber L of the actuator 10, and at the same time, the right working chamber R is opened to the atmosphere by opening the control valve V ₄ . Therefore, the maximum driving force in the rightward direction is supplied to the piston 26 of the actuator 10.

In the movement stroke of the actuator 10,
The moving speed of the piston 26 within the actuator 10 is constantly monitored by the CPU 30, and the rotational angular velocity of the drive shaft 14 is constantly calculated by the CPU 30 in the butterfly valve drive state of the embodiment.

That is, the angular velocity _vo of the drive shaft 14 is determined as vo ₌ (θ _o −θ _o-1 )/ΔT. Here, ΔT is the sampling period supplied from the setter 38 to the CPU 30, and is preferably set to about 100 milliseconds, for example. Therefore, in the butterfly valve control in this embodiment, its angular velocity is monitored every 100 milliseconds, and subsequent controls are also synchronously controlled by this sampling period ΔT.

As described above, in the high speed range, the maximum source pressure P _S is applied to one working chamber of the air actuator 10, and the other working chamber R is opened, so extremely high speed movement can be performed. This has become possible, and its angular velocity is gradually increasing, but in order to harmonize such high-speed movement with the characteristic low-speed range of the present invention, in the second invention,
A braking range is provided between the high speed range and the low speed range, and this braking range can be set to a fixed value similarly to the setting of the low speed range described above, but in this embodiment, this braking range θ _p It is characterized by being variable according to the movement speed of the actuator.

In other words, this braking area is provided before or on the near side of the low speed area mentioned above, and this braking area value θ _p
is obtained by θ _p = θ _A −θ ₁ −α・_vo・｜ _vo |. In other words, as is clear from Fig. 4, this braking range value θ _p is further α・
It is understood that only v _o ｜v _o ｜ is determined on the high speed region side. Therefore, as is clear from the above equation, as the speed of the actuator 10 increases, the braking range value θ _p moves from the low speed range to the high speed range, and as the speed difference between the high speed range and the low speed range increases, the braking range value θ p moves closer to the high speed range as the speed of the actuator 10 increases. is set so that it becomes longer.

The constant α is supplied from the setting device 38 to the CPU 30.

In the embodiment of FIG. 4, the movement curve of the actuator 10 coincides with the braking range value at time _t1 ,
The period from time t ₁ to time t ₂ at which the movement curve coincides with the low speed range acts as a braking range.

The braking action in the embodiment is basically to supply source pressure P _S to one working chamber L while closing and sealing the other working chamber R.
At t ₁ the on-off control valve V ₄ is closed,
Opening of the working chamber R to the atmosphere is blocked. Therefore,
It will be understood that the piston 26 is moved to the right by the source pressure P _S from the working chamber L, but its speed gradually decreases because the other working chamber R is sealed.

Furthermore, in the embodiment, in order to effectively perform the braking operation, the on/off control valve _V2 is opened,
As a result, the supply source pressure P _S is directly applied to the other working chamber R that is blocked from being exposed to the atmosphere, thereby applying the supply source pressure P S directly to both the working chambers L and R of the piston 26. Source pressure will be applied to both, and the braking effect will be significantly increased.

However, since the piston 26 has already been given a predetermined initial velocity, the piston 26 does not come to a stop in the braking range, and in the embodiment, the braking range value is constantly changed while detecting the speed of the actuator. Therefore, even if the cylinder 26 is stopped within the braking range, the braking range value will match the low speed range value at this stage, and the air actuator 10 will be forced to return to the high speed range and repeat the predetermined driving action. It becomes possible to continue.

When the movement curve of the actuator 10 matches the low-speed threshold at time _t2 , low-speed feed is achieved from this state until time _t3 , when the target position is reached.

In the present invention, the low speed control action is performed in one of the working chambers,
That is, this is carried out by applying the supply source pressure P _S to the working chamber L while switching the other working chamber R from the open state in the high speed range to the partially closed state.

Further, in this embodiment, the partial closing control is characterized by pulse width control, and the control valve _V4 is intermittently closed at a timing corresponding to the moving speed. This intermittent control is performed according to the sampling period ΔT mentioned above, and the control valve _V4 is opened for a predetermined calculated time Δt in each sampling period ΔT, and is closed for the remaining (ΔT−Δt) time. is maintained.

The control time Δt is calculated based on the following formula: Δt=β ₁ (β ₂ −| _vo |).

That is, as is clear from this equation, when the moving speed of the actuator is fast, the control time Δt becomes short, and the closing time of the other working chamber R becomes long, so a large braking action is obtained, and the speed is reduced. On the other hand, when the moving speed of the actuator 10 becomes smaller, the control time Δt increases, and the opening time of the working chamber R becomes longer, so that control is performed in the direction of increasing the moving speed.

The constants β ₁ and β ₂ are also sent from the setting device 38 to the CPU 30.
It is clear that it is supplied to

In this embodiment, in order to further increase the effect in the low-speed range, the opening and closing of the other working chamber R to the atmosphere is not only controlled by the control time Δt described above but also actively. It is characterized in that the supply source pressure P _S is applied to the other working chamber R with a polarity opposite to that of the opening to the atmosphere.

As is clear from Fig. 5, the above-mentioned working chamber R
On/off control valve that controls the opening and closing of the air to the atmosphere.
The on/off control valve V 2 that controls the application of the supply source pressure P _S to the working chamber R with respect to V ₄ is controlled to open and close with mutually opposite polarity, and as a result, when the control chamber R is opened to the atmosphere, the control valve V ₂ is controlled to open and close with opposite polarity. The supply of the source pressure P _S from the valve V ₂ is cut off, and the source pressure P _S is applied while the working chamber R is isolated from the atmosphere. It is understood that the internal pressure approaches the source pressure P _S.

Actually, the time t ₃ when the movement curve reaches the target position θ _A
In this case, various constants are determined so that both working chambers L and R of the actuator 10 are filled with the source pressure P _S .

Then, at time _t3 , all the control valves _V1 , _V2 , _V3 , and _V4 of the pneumatic switching circuit 22 are closed in the OFF state, and the supply source pressure P _S to both the working chambers L and R is
In this state, the piston 26 of the air actuator 10 is positioned and fixed, and as a result of the high pressure being applied to both working chambers L and R, its stiffness becomes extremely high, and even when disturbed, It becomes possible to obtain a fixed state that does not move easily.

In this embodiment, as is clear from FIG. 4, a hysteresis region of θ _H is provided on both sides of the target position θ _A , and a control dead zone is set for the movement of the piston 26 during this period. .

As is clear from FIG. 4, the movement curve shown as an example shows a state in which the piston 26 moves beyond the hysteresis area at time _t4 after positioning, but there is a special case where such positioning failure occurs. According to this embodiment, even if the target position θ _A
A low-speed region is also provided on the opposite side of , and return control is performed with the opposite polarity to the low-speed region described above, and although it will not be explained in detail, the movement curve is returned to the target position θ _A again as in Fig. 5. , it becomes possible to quickly obtain a stable position.

The set value θ _H of the hysteresis range is also supplied to the CPU 30 from the setter 38 .

As explained above, in the present invention, in the high speed range that requires the maximum initial driving force, movement is performed at the maximum acceleration, and then in the preset low speed range near the target range, both working chambers are moved. It is possible to perform low speed control while increasing the pressure, and it is possible to perform extremely stable stopping action with high stiffness at the target position.

As is well known, only the initial value of the current applied to the excitation coil for operating each on/off control valve V mentioned above is increased, and after the control valve is opened, a small holding current is applied to maintain that state. Consists of the circuit configuration to supply the In the above-mentioned embodiment, the partial closing control of the relief valve in the other working chamber in the low speed range is performed by pulse width control that intermittently controls the opening and closing of the control valve. By controlling a predetermined number of relief valves formed from a valve assembly and selected from the plurality of control valves to close,
It is also possible to perform desired low-speed feed control.

[Effects of the Invention] As explained above, according to the first aspect of the present invention, the movement control of the pneumatic actuator is separated into a high speed range and a low speed range, high speed initial drive is performed, and sealing pressure is applied when stopped. It is possible to provide an improved control method that can perform accurate stop control in a sufficiently elevated state, and by this, it is possible to provide an extremely good control method for various industrial equipment, especially robot arm control, etc. It is.

Therefore, according to the first aspect of the present invention, there is an advantage that it is possible to quickly move to a desired stop position, and that subsequent displacement commands can be followed with high responsiveness in this positioning state.

Further, according to the second aspect of the present invention, a braking region is provided before the low speed region, whereby the actuator that is being driven at high speed is braked without overshooting or the like. It becomes possible to connect to the area smoothly.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing a butterfly valve rotation angle control device to which the pneumatic actuator positioning control method according to the present invention is applied, and FIG. 2 is a schematic explanatory diagram showing the pneumatic actuator and pneumatic switching circuit of FIG. 1. , FIG. 3 is a block diagram showing the control circuit of FIG. 1, FIG. 4 is an operational explanatory diagram showing a preferred embodiment of the present invention, and FIG. 5 is a timing chart of the pneumatic switching circuit used in FIG. 4. It is a diagram. 10... Actuator, 18... Control circuit block, 20... Potentiometer, 22... Pneumatic switching circuit, 30... CPU (central processing unit), 38... Setting device,
V1, V2, V3, V4...control valves.

Claims (1)

[Claims] 1. In an air actuator positioning control method in which pressurized air is supplied from an on/off control valve to the left and right working chambers of an actuator and the actuator is positioned by the pressure balance between the left and right working chambers, one While applying source pressure to one working chamber, the other working chamber is opened to the atmosphere to perform high-speed movement, and near the target position, while applying source pressure to one working chamber, the relief valve of the other working chamber is intermittently closed. It moves at low speed while maintaining both working chambers at a pressure close to the supply source pressure by controlling the pulse width opening and closing.
After the actuator reaches the target position, the on/off control valve is kept sealed in the OFF state with a pressure approximately equal to the supply source pressure applied to both working chambers, thereby accurately positioning the actuator at the target position. Positioning control method for pneumatic actuator. 2. A positioning control method for an air actuator according to claim 1, characterized in that a source pressure is intermittently applied to the relief side of the other working chamber in a low speed range. 3 In an air actuator positioning control method in which pressurized air is supplied from an on/off control valve to the left and right working chambers of the actuator and the actuator is positioned based on the pressure balance between the left and right working chambers, a supply source is supplied to one of the working chambers in order to obtain the initial driving force. While applying pressure, the other working chamber is opened to the atmosphere to perform high-speed movement, and near the target position, while applying source pressure to one working chamber, the relief valve of the other working chamber is intermittently controlled to open and close in pulse width. and moves at low speed while maintaining both working chambers at a pressure close to the source pressure.
After the actuator reaches the target position, the on/off control valve is kept sealed with a pressure approximately equal to the supply source pressure applied to both working chambers, and the actuator is accurately positioned at the target position and the actuator is moved to the front stage of the low speed range. A method for controlling the positioning of an air actuator, characterized in that a braking region is set, and in the braking region, a relief valve in the other working chamber is closed to provide a braking action to the actuator. 4. A positioning control method for a pneumatic actuator according to claim 3, characterized in that in the braking region, a source pressure is applied to the other working chamber. 5. A method for positioning an air actuator according to any one of claims 3 and 4, characterized in that the braking area consists of a fixed area provided before the low speed area. 6. A positioning control method for a pneumatic actuator according to claim 3, wherein the braking range is comprised of a variable range calculated according to the moving speed of the actuator.