JPH04203606A - Positioning control method for pneumatic cylinder - Google Patents

Abstract

PURPOSE:To enhance responsiveness and stability of a driving portion in positioning rodless type pneumatic cylinders by estimating frictional force of pneumatic cylinders, and switching intake and exhaust of a solenoid so as to apply an offset value equivalent to the estimated frictional force to a difference in pressure between the right and left cylinders. CONSTITUTION:During a positioning operation, a controller 16 reads in a detection signal output from a position sensor 7, to displace and convert it into X coordinates where a target value is used as an original, and calculates a speed and an acceleration. A pressure sensor 10 detects a pressure in a space defined by right and left cylinders, and calculates a difference in pressure therebetween, to correct the difference in pressure equivalent to Coulomb's frictional force in a sealing portion once for (n) times. Namely, intake and exhaust of a solenoid 12 is switched under a switching condition of inertia force, speed and displacement consisting of a load mass and acceleration so that the difference in pressure equivalent to the Coulomb's frictional force is corrected as an offset value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a positioning control system for a robot operated by a rodless pneumatic cylinder.

(Prior art) The conventional wave according to the present invention is a pulse drive positioning method of a pneumatic cylinder in which the drive unit used in the robot hunt is operated by an air cylinder, and the Coulomb friction generated in the air cylinder is The air cylinder is controlled by setting the switching conditions of the electromagnetic valve by keeping the differential pressure corresponding to the force FC constant.

(Spring Hydraulic and Pneumatics Conference, 1990, sponsored by Japan Society of Hydraulics and Pneumatics, Proceedings P, 125-128 "Pulse drive positioning of pneumatic cylinders using adaptive control") (Problem to be solved by the invention) However, the above The air cylinder control method is such that the frictional force of the pneumatic cylinder fluctuates greatly due to the friction of the sealing part, etc., and since the differential pressure corresponding to the Coulomb frictional force FC is kept constant, if the fluctuation of the frictional force becomes large, There are problems in that the control method becomes difficult, the positioning accuracy deteriorates, and the positioning time increases.

The technical object of the present invention is to provide a drive positioning control system for a pneumatic cylinder with good responsiveness and stability of the drive section.

[Structure of the invention] (Failure to solve the problem) The technical means to solve the problem are as follows.

Air pipes are provided at both ends of a magnetic type cotless pneumatic cylinder having a slider with a position sensor arranged, a pressure sensor and a solenoid valve are provided in each of the pipes, one pipe is provided with a silencer, the other pipe is provided with an exhaust port, and the pressure In a method for positioning a slider of a pneumatic cylinder device comprising a sensor, a position sensor, and a control device for controlling a solenoid valve, when positioning at an arbitrary position, the frictional force of the pneumatic cylinder is estimated and the position of the solenoid valve is determined. The conditional expression for switching the supply and exhaust of a solenoid valve, which consists of the inertia force made up of the load mass acceleration, speed, and displacement as an offset value corresponding to the frictional force, is calculated based on the differential pressure between the left and right cylinder spaces, which is the driving force. This is a positioning control method for a pneumatic cylinder that operates a slider by adding a value.

(Function) The frictional force of the sliding portion of the pneumatic cylinder changes absolutely due to the friction of the sealing portion.

For this purpose, in order to perform highly accurate positioning, a control system that is always linear is constructed by correcting the differential pressure Pc, which corresponds to the Coulomb friction force between the pneumatic cylinder and the seal, in accordance with the fluctuations in the friction force. This enables stable positioning performance.

(Example) Examples will be described below.

In Figure 1, 1 is a pneumatic cylinder (rodless type)
2 is a cylinder movable part outside the cylinder, and 3 is a slider.

There is a piston 24 inside the cylinder, and magnets are incorporated in each of the cylinder movable parts 2, so that the cylinder movable part 2 moves as the piston 24 moves due to their magnetic coupling.

Both ends of the pneumatic cylinder 1 are directed to side plates 25 fixed to the frame 6. A slider 3 is fixed to the cylinder movable part 2. The slider 3 is supported by a guide hair ring 5 that slides on a guide rail 4 provided on a frame 6.

A position sensor scale 8 is installed between the left and right side plates 25, and a non-contact position sensor 7 is fixed to the slider 3 at a certain distance from the octopus scale 8.

A branch pipe 9 is installed at both ends of the pneumatic cylinder.
is connected to a pressure sensor +l-' 10 and a tube 11, one side of the tube 11 is connected to a solenoid valve 12, a supply pipe 13 is connected to an air supply port of the solenoid valve 12, and an exhaust port 1
4 is connected to a silencer 23.

A pressure sensor signal line 26 , a position sensor signal line 27 , and a solenoid valve drive power line 28 are connected to the control device 16 .

FIG. 2 is a block diagram of the control device 16, in which 17 is a CPU;
18 is an up/down counter, 19 is an A/D converter, 2
0 is a solenoid valve drive circuit, 21 is a memory, 22 is Ilo, 2
6 is a pressure sensor signal line, 2-7 is a position sensor signal line, 2
8 is a solenoid valve driving power line.

In the device, a solenoid valve drive circuit 20 inside the control device
Therefore, when the solenoid valve 12 is energized, the solenoid valve 12 enters the exhaust state, and the pressure in the cylinder chamber connected to the solenoid valve 12 decreases.

When the power is turned off, the solenoid valve 12 enters the air supply state, and the pressure in the connected cylinder chamber increases to reach the supply pressure ↓.

The pressure in the cylinder chamber is measured by the pressure sensor 10, the pressure sensor signal line 26, and the A/D converter 19.

The position of slider 3 is position sensor 7, position sensor signal cotton 2
7. The structure is measured by an up/down counter 18.

FIG. 3 shows the processing procedure of the positioning control method in the pneumatic cylinder positioning device shown in FIG. 1.

Positioning is performed using an X-axis coordinate system with the target value as the origin.

(1) During positioning processing, after reading the current value and performing displacement and conversion to the X coordinate system, the speed statement and acceleration X are calculated.

(2) Next, read the pressure and find the differential pressure Pd.

(3) Correct the Coulomb friction equivalent Pc once every n times.

(4) If positioning is not completed, switch the solenoid valve supply/exhaust according to the solenoid valve switching conditions, and return to the positioning process again.

(5) When positioning is completed, both solenoid valves are brought into the air supply state and stopped.

In addition, e in the figure is the positioning tolerance range, kr, c are constants,
m is the mass of the slider 3 and the cylinder movable part 2, and A is the piston pressure receiving area.

Next, the principle of the positioning method will be explained.

The mass of the slider 3 and the cylinder movable part 2 is mjkg], the pressure receiving area of the piston 24 is A3cm2j, the differential chamber between both cylinder chambers is PdjPa], the Coulomb friction force between the cylinder 1 and the piston 24 is F CCN), the position of the slider 3 ( displacement) as X (m;, velocity X [mXs”], acceleration X Cm/
s"3.

During low-speed operation, viscous friction is small, so if it is ignored, the equation of motion is as follows.

m”X=APd-Fc sgn (x)...11)
Set the Coulomb friction force Fc (IN) to the initial value FeO''.

N] and the variation △F CCI N] F c = F
c o'-.

△Fc and the differential pressures corresponding to the Crohn friction forces Fc, Fco, and △Fc are respectively Pc, Pco, and △Pc [P
a), then Fc=APc, Fco=APco, △F
c=AΔPc, and (1) becomes as follows.

mX=A (Pd-Fc sgn (X)1...
(2) mX=A (Pd − (Pco+△Pc)sgn (f
))... (2) According to the electromagnetic valve switching conditions in Figure 3 (4), the following equation approximately holds true when the delay in the pressure response of the cylinder chamber is small.

Pd=PcuSgn(text)=Kv(text+Cχ) (
2) Substitute into mX=A (P c, o s g n (X) −K
v ('R-i-CX)-(Pco卆△Pc)sgn
(sentence))mX;Akv (X+CX) -A (PC0
-PCCI-△Pc)sgn (text) mX+AKv (X+CX) --A△Pc sgn
(Text) By correcting the current differential pressure Pco, it becomes ΔPc-〇, so equation (2) becomes as follows.

mX+Akv(text+CX)=O−・−(3) Therefore, “X+ (Akv/m)x+ (AKv c/m)X
-〇... (4) Wn=FTπ■Bottom box ζ=, "■niF bottom -1...
- (5) From (4) and (5), it can be seen that it is possible to improve the response by adjusting Kv and C as parameters.

FIG. 4 shows an external view of another embodiment of the device in which the position sensor 7 is built into the thin lid 1 having a rod 29 integrated with the piston 24. The positioning method may be the same procedure as described above. In this case, the size can be reduced because the position sensor 7 and the position sensor scale 8 are not required externally.

(Effects of the Invention) The present invention has the following effects. In other words, it is possible to estimate the frictional force by using modern systems; adaptive control based on wholesale theory and an adaptive observer.

However, these procedures require complicated calculations and require a highly functional control device.

In the present invention, the parameters used for the switching conditions are used to estimate the frictional force from the actually measured values, which facilitates calculation. Furthermore, (1) It is applicable not only to a single pneumatic cylinder but also to a control system that includes a sliding part such as a guide rail.

(2) When setting the value of the switching condition, it is not necessary to set it accurately, and adjustment is easy when manufacturing the device.

(3) When it is known that the frictional force is constant, the external force applied to the slider can be estimated.

[Brief explanation of the drawing]

Fig. 1 is an external view of the positioning device and control device incorporating a pneumatic cylinder, Fig. 2 is a block diagram inside the control device, Fig. 3 is a flowchart of the positioning control method, and Fig. 4
The figure is an explanatory diagram of the external appearance of another embodiment. ■...Pneumatic cylinder, 3...Slider, 7...
Position sensor, 10... Pressure sensor, 12... Solenoid valve, 13... Air supply port, 14... Exhaust port, 16... Control device, 24... Piston.

Claims (1)

[Claims] Air pipes are provided at both ends of a rodless pneumatic cylinder having a slider on which a position sensor is arranged, a pressure sensor and a solenoid valve are provided in each of the pipes, one pipe is provided with a silencer, the other pipe is provided with an exhaust port, the pressure sensor,
In a method for positioning a slider of a pneumatic cylinder device comprising a position sensor and a control device for controlling a solenoid valve, when positioning at an arbitrary position, estimating the frictional force of the pneumatic cylinder and switching the supply and exhaust of the solenoid valve, To the differential pressure between the left and right cylinder spaces, which is the driving force, add the value of the conditional expression that switches the supply and exhaust of the solenoid valve, which consists of the load mass, the inertia force made up of acceleration, and the speed and displacement, as an offset value corresponding to the frictional force. A positioning control system for pneumatic cylinders that actuate sliders.