JPS61120213A - Positioning controller - Google Patents

Abstract

PURPOSE:To reduce the steady position deviation and to improve the positioning accuracy by varying the loop gain in response to the time in a position control mode. CONSTITUTION:A control system of a positioning controller is provided with a target position setter 3, a present position counter 4, a motor 8 for a mobile body 10, a selector 17 for the speed dat or the gain data, a memory 18 for speed curve table, a memory 19 for a again setting table, etc. When the shift distance and the target position of the matter 10 are decided, a speed curve of the speed curve table 18 and a gain curve of the gain setting table 19 are selected. Then the target position is set together with the initialization of a counter 21. The gain data of the table 19 is read out for a fixed period of time in accordance with the value of the counter 21. This gain data is stored to a register 16 and the gain of the control system is changed.

Description

Detailed Description of the Invention [Field 1] The present invention relates to a positioning control device for a movable body in a semiconductor manufacturing device such as a step-and-repeat exposure device or an IC bonder, or an industrial robot or an NG machine tool. In particular, it is possible to compensate for the influence of disturbances such as load fluctuations and changes in frictional force on sliding parts, to perform positioning in a short time and without steady position deviation, and to eliminate differences in steady position deviation depending on the positioning direction. The present invention relates to a positioning control device.

[Description of Prior Art] Conventionally, the control circuit of this type of positioning control device is configured as shown in FIG.
It was carried out according to the speed curve shown in the figure. In FIG. 10, the speed control section is from a to e, and at point e near the target position, the control is switched to position control for final positioning. In the figure, a is the acceleration start point, b is the acceleration end point when the maximum speed is reached and shifts to constant speed drive, C is the deceleration start point, d is the deceleration end point when the final speed is reached, and e is the control mode. The switching point f is the positioning completion point.

In FIG. 9, during speed control, the analog switch 6 selects the D/A converter 2 for speed command, and the speed function generator 1 creates speed curves as shown in FIG. Converter 2 obtains a speed command voltage.

A closed loop of amplifier 7, motor 8 and speed detector 9 performs speed control by speed feedback control, and D/A
The movable body 10 moves at a speed according to the speed command voltage from the converter 2.
move. Next, the control is switched to position control at the control switching position e, and the analog switch 6 selects the D/A converter 5 for position error output. A closed loop of the current position counter 4, the D/A converter 5, the amplifier 7°, the motor 8, the movable body 10, and the position detector 11 forms a positioning feedback control system.

In such a configuration, the loop gains of each speed and position control system are constant, and due to factors such as load fluctuations, changes in the frictional force of the sliding parts, or changes in the rigidity of the system,
Or, for reasons such as not being able to increase the loop gain to avoid destabilizing the control system, vibration may occur when switching position control, or "steady position deviation (deviation y between the target position and the actual stop position is large"). However, there was a drawback that the magnitude of the steady position deviation varied depending on the position and direction of movement.

[Object of the Invention] In view of the problems with the conventional type described above, the present invention aims to improve positioning accuracy in a positioning control device by reducing steady position deviation and changes in steady position deviation due to target position and movement direction. , the purpose is to shorten the positioning time.

[Explanation of Examples] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows the configuration of a control system of a positioning control device according to an embodiment of the present invention. In the figure, 3 is a target position iF setter, 4 is a current position counter or deviation counter, 7 is an amplifier that is a servo amplifier, 8 is a motor that drives the movable body 10, 9 is a motor speed detector such as a tacho generator, 1
0 is a movable body such as a slide table or a robot arm,
11 is a position detector such as a rotary encoder, linear scale or laser length measuring device; 12 is a maximum speed setting device; 1
3 is a selector for selecting either velocity data or position width difference data; 14 is a D/A converter for converting digital data into analog output; 15 is a multiplication type D/A converter; 16 is a multiplier type D/A converter;
17 is a selector for selecting either speed data or gain data, and 18 is a speed curve table that stores speed command values according to the speed curve. 19 is a memory which is a gain setting table storing gain setting values corresponding to the gain curve; 20 is a timing clock generating device for making the speed curve and gain setting variable time; 2°; 1 is a counter for selecting and instructing data according to time from the speed curve table and the gain setting table.

Prior to explaining the operation of the apparatus shown in FIG. 1, the principle of this configuration will be explained.

The open loop gain of the positioning control system is KO [1/S1, the motor rated torque is TD [N-ml], the feed speed when motor 8 is at the rated rotation speed is Fr [m/S], the motor fiIII itching load torque is If Td [N-ml and positioning deviation is ε[ml, steady position deviation due to changes in load torque and frictional force of sliding parts is ε> (Fr /Ko
)・(Td/Tll). Further, the open loop gain KO cannot be increased because if it is increased beyond a certain level, it will become oscillated and become unstable due to the system configuration of the servo system. For this reason, with the conventional method, the steady position deviation ε could not be lowered below a certain value.

Here, Fig. 2 shows an example of the oscillation limit in a stage positioning control system using a ball screw.

The relationship between and position deviation ε is shown. A indicates the opposite side of the motor, and b indicates the oscillation limit of the motor. According to this, the relationship between U;I loop gain KO1 and position deviation ε is expressed as Ko=K·ε−2. However, K and P are proportional constants and may change depending on the position.

In the case of the conventional method, when switching from speed control to positioning control, the gain is constant, and the damping waveform in a system with viscous friction is when the gain is low (for example, gain characteristic a in Figure 3).
converges exponentially, as shown by a in Figure 4, and when the gain is high (b in Figure 3), it converges oscillatedly, as shown by b in Figure 4, while the dry friction converges linearly to a constant deviation value. Therefore, if you increase the gain over time as shown in curves C to e in Figure 3 so that the gain is set as large as possible in the stable region according to the positional deviation, oscillation will not occur and the curve in Figure 4 A response characteristic as shown in C can be obtained.

Therefore, in the present invention, by selecting the gain curve according to the type and magnitude of friction and the magnitude of the rigidity of the system,
The difference between the steady position deviation and the steady position deviation depending on the moving direction of the movable body is made extremely small, thereby improving positioning accuracy. In FIG. 3, c-e are examples of gain characteristics selected in the present invention, C is a linear change, d is a logarithmic curve change, and e is an n-dimensional curve change.

Next, the operation of the control system shown in FIG. 1 will be explained.

The operation of this control system is controlled by a control device (not shown) comprising, for example, a microprocessor. Applicable! In the I1m device, when the moving distance of the movable body and the target position, which is the sum of the current position and the moving distance, are determined by calculation processing or input operations by the operator, the maximum speed is set by the maximum speed setting device according to the moving distance. 12, select the speed curve in the speed curve table 18, set the target position in the target position counter 3, and select the gain curve in the gain setting table 19 according to the target position.

As the gain setting table 19, there are two possible options: a one-dimensional table that uses the same value for variable gain data at all positions, and a two-dimensional table that changes depending on the target position, but a one-dimensional array is used. In this case, the selection of the gain curve according to the target position can be omitted.

In the control system shown in FIG. 1, when the target position, maximum speed, etc. are set, and the setting of the oscillation frequency of the oscillator 20 is completed, the counter 21 is initialized, and the selector 13 and the selector 11 are selected to the speed control side. Speed control is performed in the section a to d in FIG. As a result of this speed control, when the movable body 10 reaches the vicinity of the target position, the selector 13.17 is then switched to the position control side, the variable gain time is set in the oscillator 20, and the counter 21 is initialized. Positioning control is performed using the variable gain mode, which is characterized by

In this positioning control, the signal from the oscillator 20 is
Gain data from the gain setting table 19 is read out at regular intervals according to the count value of the counter 21 that counts the timing clock, and is stored in the register 16. The multiplication type D/A converter 15 divides the analog voltage output from the D/A converter 14 according to the gain data stored in the register 16 to change the gain of the control system. Note that the counter 20 does not count up after the final data of the gain table is read, and the register 16 holds the final gain data.

By doing this, it is possible to prevent the occurrence of photographing when switching from speed control to position control, shorten positioning time, reduce steady position deviation, and reduce the difference in steady position deviation depending on the direction of movement. can be achieved.

FIG. 5 shows an embodiment of a control circuit using a computer.

In the figure, 22 is a central processing unit such as a microcomputer or minicomputer, and 23 is a ROM, R
A memory device such as AM, 24 a computer bus, 25 speed command latch data 12' and current position U counter data 4.
' is the switching command flag.

A speed curve table and a gain setting table are provided in the memory 23.

Here, the functions of blocks 17 to 21 in FIG. 1 are executed in a program by using a paralysis machine.

Next, the operation of the control circuit shown in FIG. 5 will be explained with reference to the flowchart shown in FIG.

In this control circuit, when moving distance information is given to CP tJ 22, the maximum speed is determined because the maximum acceleration is determined by the motor torque, load torque, inertia force, etc. The CPU 22 determines a deceleration time, a deceleration section movement distance, and a deceleration correction value corresponding to this maximum speed, and further determines a deceleration start position and a positioning switching position.

Next, these data are set in a predetermined area of the memory 23, and a command is sent to the switching command flag 25 to set the speed command latch 1.
2' is connected to the D/A converter 14. ``Thereby, the speed control mode is entered, and speed control is performed in sections a to d in FIG. 2, which are acceleration, constant speed, and deceleration. As a result of this speed control, when the final speed reaches the constant speed section d-e, the CP LJ 22 detects the positioning switching position based on the current position data of the current position counter 4', and when the positioning switching position is reached, , gives a command to the switching command flag 25 to switch to the position control mode.

After switching to the position control mode, select the gain table (Fig. 7) according to the target position, initialize the pointer for reading the gain table provided in the memory 23, read the first gain data, and store it in the register. Set to 16. Thereby, the loop gain of the control circuit is varied in accordance with the gain data in the multiplication type D/A converter 15, as described for the control system in FIG. Subsequently, the pointer is advanced to point to the next address in the gain table.

Next, the sample time is checked, the CPU waits until the next gain data output timing arrives, and then repeats the variable gain routine following the gain data read process described above. In this way, the gain is changed as shown in the gain curve of FIG. Also, after setting the above gain and before advancing the pointer, a check is performed for the end of the variable gain, and if the pointer points to the highest bale data in the gain table, the variable gain routine is executed and the next positioning is performed. The process moves to an end determination routine, and when the positional deviation becomes less than or equal to a predetermined value, the positioning control K10 operation is ended.

FIG. 8 shows a control circuit according to yet another embodiment of the invention. The circuit shown in FIG. 1 is different from the circuit shown in FIG. 1 in that the digital parts for speed control and position control are separated and switched in the analog part. That is, in the circuit shown in FIG. 1, the maximum speed setter 12, speed curve table 18, oscillator 20, and counter 21 realize the same functions as the speed function generator 1 of the conventional device shown in FIG. However, in the embodiment shown in FIG. 8, compared to the conventional example, the speed control system is configured with a speed function generator 1, etc., and the position control system is configured with a gain table 19 and an oscillator 20.
In addition to adding a counter 21 and a counter 21,
A converter 15 is connected between the D/A converter 5 and the positioning control side contact of the analog switch 6. The output of the A converter 5 is divided into voltages.

[Modifications of Embodiments] The present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications. For example, the selector 13, switching command flag 25, register 16, and multiplication type D/A converter 15 in FIG. 5 are eliminated, and the speed command latch 1
2' is directly connected to the D/A converter 14, and during position control, the computer reads the content of the berthing position counter, that is, the current position, and multiplies the command voltage according to the position IIF deviation by the time-varying gain data. If the command value obtained is outputted to the speed command latch 12', the number of hardware components can be largely omitted.

In addition to the trapezoidal wave mentioned above, the shape of the speed command curve is
It is also possible to use a verse sine wave, a cycloid wave, an n-dimensional curve, etc.

Furthermore, as the shape of the variable gain curve, for example, the shape of the third
In the curve shown in the figure, the gain when switching to positioning 1ill and tll is shifted so that it becomes the gain during speed control, and the gain when switching from speed control to positioning control is continuous, or it is not a simple increase but is in the middle. The shape may have a local maximum value or a local minimum value. Further, it is also possible to increase the final gain within a range that provides a steady position deviation that allows for even the required positioning accuracy.

[Effect of R light] As described above, according to the present invention, by varying the loop gain particularly at the time of 1 m, 1
Since it is possible to set the loop gain of the 1 Ill system to the optimum position within the stable region at each point in time, the steady position deviation and the difference in the steady position deviation due to the moving direction of the movable body are reduced. In other words, positioning accuracy is improved. Also,
Positioning time becomes shorter. Furthermore, reliability is also improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the electric circuit configuration of a positioning control device according to an embodiment of the present invention, FIG. 2 is a graph showing stability limits of position deviation and gain in the positioning control device, and FIG. Fig. 4 is a graph showing the relationship between time and gain in the device shown in Fig. 1, Fig. 4 is a position change (response) waveform diagram after switching to position drawing method control, and Fig. 5 is a graph showing the relationship between time and gain in the device shown in Fig. 1. 6 is a flowchart for explaining the operation of the control circuit in FIG. 5, and FIG. 7 is a gain table set in the memory in FIG. 5. 8 is a block diagram of a control circuit according to yet another embodiment of the present invention, FIG. 9 is a block diagram showing a conventional control circuit, and FIG. 10 is an example of a speed command curve. FIG. 1: Speed function generator, 3: Target position setter, 4: Current position counter, 4': Current position counter data, 6: Analog switch, 7: Amplifier, 8: Motor, 9: Speed detector, 10: Movable Body, 11: Position detector, 12: Maximum speed setter, 12' Two speed command latch data, 13.17
: Selector, 14: D/A converter, 15: Multiplying D/A
converter, 18: speed curve table, 19: double gain setting table, 20: generator, 21: counter, 22: central processing unit, 23: memory device, 25: switching command flag.

Claims (1)

[Claims] 1. When moving the movable body to the target position, the movable body is
In a positioning control device equipped with a servo control system that first moves to the vicinity of the target position in a first control mode emphasizing speed and then switches to a second control mode emphasizing stop position accuracy to position at the target position, gain setting means for setting the loop gain of the servo control system according to time after switching to the control mode; and gain control means for varying the loop gain according to the output of the gain setting means. A positioning control device characterized by: 2. The positioning control device according to claim 1, wherein the gain control means is a multiplier that multiplies the output of the gain setting means by a positional deviation output indicating the distance from the target position to the current position. 3. The positioning control device according to claim 1 or 2, wherein the gain setting means has a plurality of gain curves for changing the loop gain setting amount in the second control mode according to the target position.