JPH0346681B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of controlling a pneumatic actuator used in industrial robots and the like, and an apparatus for implementing the method.

[Prior Art] In a hydraulic actuator, a displacement signal, a velocity signal, and an acceleration signal of the actuator are compared with a target displacement signal, a target velocity signal, and a target acceleration signal from a signal generator, respectively, and the results of these signals are determined. The deviation signal controls the servo valve to control the drive of the actuator.

However, pneumatic actuators have poor responsiveness because they are affected by the compressibility of air, and overshoots in the stop position and vibrations in cylinder pressure occur due to changes in operating pressure and load, making it difficult to control them properly. It may be difficult to do.

[Problem to be Solved by the Invention] The problem to be solved by the present invention is to develop a pneumatic actuator that can appropriately control actuator drive regardless of air compressibility, pressure fluctuations, load changes, cylinder dimensions, stop positions, etc. An object of the present invention is to provide a control method and a control device.

[Means for Solving the Problems] In order to solve the above problems, the control method of the present invention uses a digital method in which the operating position of a pneumatic actuator is used as an operating position signal, and a phase plane locus of position and velocity corresponds to position and velocity. Feedback is made to the speed signal generator provided by the memory,
Outputting a target speed signal corresponding to the operating position from the digital memory, and generating an actual speed signal and an actual acceleration signal from the operating position signal;
A speed deviation between the target speed signal and the actual speed signal is determined, and a target acceleration signal is output from the acceleration signal generator based on the speed deviation, and an acceleration deviation between the target acceleration signal and the actual acceleration signal is calculated. The invention is characterized in that the pneumatic actuator is driven and controlled by determining the acceleration deviation and adjusting the opening amount of a control valve that supplies compressed air to the pneumatic actuator.

Further, in order to solve the same problem, the control device of the present invention includes a position detection means that detects the operating position of the pneumatic actuator and outputs an operating position signal;
A speed calculator and an acceleration calculator that calculate the actual speed and actual acceleration from the operating position signal of the pneumatic actuator, and a target speed signal from a digital memory in which the phase plane locus of position and speed is given in advance by the correspondence between them. an acceleration signal generator that outputs a target acceleration signal based on a speed deviation between the target speed signal and the actual speed signal, and an acceleration signal generator that outputs a target acceleration signal based on the acceleration deviation between the target acceleration signal and the actual acceleration signal. a control valve connected to the pneumatic actuator whose opening amount is controlled by
It is characterized by having the following.

[Operation] The speed signal generator to which the operating position signal has been fed back outputs a target speed signal from a digital memory in which the phase plane locus of position and speed is given in advance by their correspondence.

The digital memory in which the positions and speeds correspond is quick to correspond between memories, so there is no response delay due to the compressibility of air, and an appropriate target speed signal can be output promptly.

Also, based on the speed deviation between this target speed signal and the actual speed signal, a target acceleration signal corresponding to the operating position of the actuator is output, and further based on the acceleration deviation between this target acceleration signal and the actual acceleration signal, a control valve is output. Since the opening amount of the control valve is adjusted, the opening amount can be controlled more appropriately than when the control valve is controlled by adding individual signal deviations.

[Effects of the Invention] The control method and control device for a pneumatic actuator according to the present invention outputs a target speed signal corresponding to an operating position from a digital memory that associates a position and speed given in advance to a speed signal generator. , the correspondence between memories is fast, and there is no response delay even if the working fluid is compressible.

In addition, since the opening amount of the control valve is adjusted based on the acceleration deviation between the target acceleration signal and the actual acceleration signal, which are output based on the speed deviation between the target speed signal and the actual speed signal, the responsiveness of the actuator is significantly improved. Not only can it be improved, but it can also be driven in any manner, and the pneumatic actuator can be controlled with high precision regardless of disturbances, air pressure fluctuations and compressibility, load fluctuations, etc.

[Example] Examples of the present invention will be described in detail below based on the drawings.

FIG. 1 is a control calculation block diagram showing the flow of signals in a pneumatic cylinder device to which the present invention is applied, in which the actual cylinder position signal
A target speed signal v corresponding to the signal X is output from the speed signal generator, and the signal v is subtracted from the actual speed signal V obtained by processing the actual position signal By sending the velocity deviation signal v-V as a subtraction result to the acceleration signal generator, a target acceleration signal a corresponding to the signal v-V is generated, and this signal a and the actual position signal By performing subtraction with the actual acceleration signal A obtained by processing with a computing unit and sending the acceleration deviation signal a-A as a result of the subtraction to the control operation computing device, the signal a-A
The control signal ΔA is calculated by performing calculations such as PID control on
The signals S ₁ and S ₂ obtained by processing the signal ΔA in the next-stage effective cross-sectional area setting signal generator are applied to the control valve, thereby controlling the opening amount of the control valve. The cylinders connected to these control valves are then controlled.

FIG. 2 shows a specific configuration of a device that performs the control calculations shown in FIG. This is a digital counter that counts position pulses output from a position detector. By controlling the switching and opening amounts of the control valves 2a and 2b, the rod chamber 5 and head chamber 6 in the cylinder 1 are switched and communicated with the air sources 7 and 8 and the atmosphere, and the driving direction of the cylinder 1 and the opening amount are controlled. The operating position of the cylinder 1 driven by the speed is detected by the position detector 3, which is continuously output as a position pulse, and the position pulse is read by the digital counter 4 to generate the actual position signal of the cylinder. It outputs X.

The position detector 3 can be composed of a rotary pulse encoder, a linear pulse encoder, a potentiometer, etc., and the control valves 2a and 2b are pressure control valves, flow control valves, electropneumatic proportional valves, and on/off valves. Alternatively, it can be configured by a PWM type control valve, or by connecting a plurality of on/off valves or PWM type control valves in series or parallel.

When on-off valves are used as the control valves 2a and 2b, the function of the flow rate control valve can be approximated as follows. In other words, the flow characteristics of the on-off valve are: the flow rate when fully open is G, the supply differential pressure is ΔP,
If the flow coefficient is C, it is expressed as G=C・ΔP.

Now, if the control valve is turned on and off during a sufficiently short time ΔT so that the total time of the control valve to be fully open is Δt′, the average flow rate during that time ΔT will be
G' is as follows: G'=C・ΔP・Δt′/ΔT=(C・Δt′/ΔT)ΔP=C′・ΔP (where C′=C・Δt′/ΔT).

Here, when Δt' is changed, the apparent flow coefficient C' changes accordingly, so G' also changes,
This allows it to perform the same function as a flow rate control valve.

In the signal processing circuit connected to the digital counter 4, 11 is a speed calculator, 12 is an acceleration calculator, 13 is a speed signal generator, 14 is a subtracter, 15 is an acceleration signal generator, 16 is a subtracter,
Reference numeral 17 indicates a control operation calculation device, and reference numeral 18 indicates an effective cross-sectional area setting signal generation device for the control valve.

In such a signal processing circuit, when the actual position signal X is output from the digital counter 4,
An actual velocity signal V and an actual acceleration signal A are generated from the signal
Sent to 16th. In order to generate the actual speed signal V and actual acceleration signal A, a speed meter such as a tachometer may be attached to the actuator, and an appropriate accelerometer may also be attached directly to the actuator.

On the other hand, the actual position signal X is sent as is to the speed signal generator 13. This speed signal generator 1
3 is a position memory 21 in which a large number of cylinder operating positions are stored as digital quantities at arbitrary minute intervals, and a velocity that is associated with each operating position in the position memory 21 by a predetermined functional relationship 23 is stored as a digital quantity. When the actual position signal X is inputted, a speed signal corresponding to the position signal in the position memory 21 is output as a target speed signal. In the speed signal generating device 13, a large number of cylinder operating positions set at minute time intervals can be stored and these can be made to correspond to the speed memory.

The target speed signal is calculated from the actual speed signal V by a subtracter 14 at the next stage, and a speed deviation signal vV based thereon is sent to an acceleration signal generator 15.

The acceleration signal generator 15 has an arbitrary increasing function 24, and in the functional relationship, an acceleration signal corresponding to the deviation signal vV is output as a target acceleration signal. The target acceleration signal is the actual acceleration signal A and the subtracter 16 at the next stage.
The acceleration deviation signal a-A is subtracted by
is further sent to the control operation calculation device 17 at the next stage.

The control operation calculation device 17 performs nonlinear control such as proportional control, PID control, on/off control, or PWM control on the acceleration deviation signal a-A. For example, when performing PID control, in the frequency domain, ΔA=Kp(1+sTd+1/sTi)(a-A) Kp: Proportional gain of PID operation Td: Differential time of PID operation Ti: Integral time of PID operation s: Calculation like Laplace operator is performed.

The deviation signal ΔA obtained in this way is sent to the next-stage effective cross-sectional area setting signal generator 18, where the effective cross-sectional area setting signals Sa and Sb are generated as follows: Saj=Sa _j-1 −K・ΔA Sbj=Sb _j-1 - (1-K) ΔA However, 0≦K≦1 j: Defined as a number of discrete times or distances, and these signals are sent to the control valves 2a and 2b to open the The amount is controlled so that the cylinder 1 is accelerated or decelerated. Further, such acceleration or deceleration is repeated every certain minute displacement of the cylinder 1 or every minute time,
The cylinder 1 will finally stop at the target position. In this case, if the cylinder is provided with a braking device, it is possible to improve the stopping accuracy and increase the possibility of reliably holding the cylinder at the stopping position.

FIG. 3 shows the control process of the cylinder. In the control of the present invention, the target speed is set as a function of the operating position of the cylinder as shown in the curve L, and the actual speed and position are set as shown in the curve L. For example, if the speed V of the cylinder deviates from the target speed vn on the curve L at a certain position X, the cylinder is accelerated or decelerated based on the acceleration signal corresponding to the speed difference. This brings the actual position and speed closer to the curve L, and in particular, the acceleration feedback loop allows the cylinder to quickly approach the final target position and target speed.

The operating position and target speed of the cylinder are set arbitrarily before cylinder operation, but if an extremely large load change occurs, they can be changed mid-operation to prevent load disturbances. Alternatively, the same effect can be expected by changing the increasing function in the target acceleration signal generating device or the control operation in the control operation calculation device during the operation. It goes without saying that the above-mentioned increasing function and control operation can be arbitrarily set before the operation of the cylinder.

It goes without saying that the present invention can be applied to control of a plurality of cylinders and further to control of a rotary actuator.

In addition, as shown in Figure 4, in order to simplify the algorithm of computers, etc., the speed signal generator, acceleration signal generator, and control operation calculation device are each controlled by increasing or decreasing functions that change in stages. It is also possible to use an on-off valve as a control valve connected thereto and to control the on-off valve by a digital signal.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the basic configuration of an embodiment of the present invention, Fig. 2 is a block diagram showing a specific example thereof, Fig. 3 is an explanatory diagram of its control method, and Fig. 4 is a different embodiment of the present invention. FIG. 3 is a block diagram of an example. 2a, 2b...control valve, 13...speed signal generator, 15...acceleration signal generator.

Claims (1)

[Claims] 1. The operating position of the pneumatic actuator is used as an operating position signal to feed back to a speed signal generator in which a phase plane locus of position and speed is given in advance by a digital memory in which the position and speed correspond. , outputting a target speed signal corresponding to the operating position from the digital memory, generating an actual speed signal and an actual acceleration signal from the operating position signal, and determining a speed deviation between the target speed signal and the actual speed signal. , further outputs a target acceleration signal from the acceleration signal generator based on the speed deviation, calculates the acceleration deviation between the target acceleration signal and the actual acceleration signal, and based on the acceleration deviation,
A method for controlling a pneumatic actuator, comprising driving and controlling the pneumatic actuator by adjusting an opening amount of a control valve that supplies compressed air to the pneumatic actuator. 2. Position detection means that detects the operating position of the pneumatic actuator and outputs an operating position signal; A speed calculator and an acceleration calculator that calculate the actual speed and actual acceleration from the operating position signal of the pneumatic actuator; a speed signal generator that outputs a target speed signal from a digital memory whose phase plane locus is given in advance by these correspondences; and a speed signal generator that outputs a target acceleration signal based on the speed deviation between the target speed signal and the actual speed signal. a control valve connected to the pneumatic actuator, the opening amount of which is controlled based on the acceleration deviation between the target acceleration signal and the actual acceleration signal; Control device.