JPH0279785A - Apparatus for controlling stop at predetermined position - Google Patents

Abstract

PURPOSE:To prevent transient oscillation and to stop a device steplessly by imparting a stop position command and an idling speed command to a motor, detecting the position of the motor, obtaining a correcting signal based on the deviation from the instructed position, and driving the motor. CONSTITUTION:A stop position signal D is instructed from a stop position command circuit 2. At the same time, an idle speed command A is outputted from a speed command circuit 1. An actual position signal F is outputted from a position detector 7 which is linked with a rotating motor 6. The difference between the signal F and the stop position signal D is inputted into an automatic position adjusting device 3, and a signal B is outputted and inputted into a signal processing circuit 8. The signal processing circuit 8 outputs a speed command signal E based on the signals A and B. The speed of the motor 6 is reduced through a driving device 5. When the difference between the actual position of a load and the instructed stop position becomes within a specified deviation, speed control is changed into position control. In this way, transient oscillation is prevented, and stepless stopping is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixed position stop control device for a load driven and displaced by an electric motor.

[Prior Art] □ As a conventional fixed position stop control device of this type, one illustrated in the block diagram of FIG. 4 is known.

In FIG. 4, reference numeral 1 denotes a speed command circuit which, upon receiving a fixed position stop command, outputs a slow speed command signal A which is considerably lower than the normal operating speed.

2 is a stop position command circuit, which outputs a stop position setting signal for a load driven and displaced by the electric motor 6; 3 is an automatic position adjuster, which connects the position setting signal and the electric motor 6.
Alternatively, the load position detection signal F from a position detector 7 such as a pulse encoder linked to the load is input, and the polarity and appropriate polarity are set such that the position deviation becomes zero from the deviation D-F between the two signals. It calculates and outputs a position correction speed command signal B having time characteristics. 5 is the electric motor 6
The driving device for the inverter is, for example, a transistor inverter, a base driving circuit for the main circuit switching transistor of the inverter, an automatic speed regulator, etc.

Next, 4 is a switching circuit for input signals to the drive device 5, and the speed of the motor 6 is reduced to the value specified by the slow speed command signal A, and the position of the load is changed to the value specified by the stop position setting signal. The command signal A is switched to the position correction speed command signal B on the condition that the specified position has reached a predetermined deviation peak, and is passed through and output as a signal E.

[Problem to be solved by the invention]

The configuration of the control system of the fixed position stop control device as described above consists of a speed control system and a position control system that switch and share the driving device of the motor, and controls the deceleration state of the motor and the approach state of the load to a predetermined position. The speed command signal and position error signal to the drive device at the time of control system switching determined by the above are determined independently from each other and have different values in principle.

Therefore, in the conventional method described above, in which the input signal to the drive device is instantaneously switched from the speed command signal to the position deviation signal, the position control system including the drive device responds to the signal amount deviation at the instant when both signals are switched. As a result, the load approaches its predetermined stop position while repeatedly overshooting and pulling back in accordance with the transient response characteristics unique to the position control system. Stopping was obstructed.

FIG. 5 is an operation waveform diagram showing switching of the input signal to the drive device and a speed fluctuation pattern accompanying the switching.

As shown by the solid line in the figure, the input signal is a steady speed command signal up to time t1, which suddenly changes to a slow speed command signal A with a value considerably lower than the steady speed, and the actual speed shown by the dotted line in the figure is the same as the signal. The time when the load Φ position reaches a predetermined vicinity of the stop setting position while decelerating to the command value of A [2
In this case, the speed command signal B for position correction corresponds to the position deviation. As mentioned above, the designated values of the signals A and B at time t2 are different in principle, and due to the sudden change in this designated input signal, the actual speed shown by the dotted line becomes excessive with respect to the signal B during the period from time t2 until the load stops. It reaches zero while repeating the control state.

In view of the above, it is an object of the present invention to provide a fixed position stop control device having a signal switching circuit that smoothes temporal fluctuations of the input signal to the drive device at the time of switching.

[Means to solve the problem]

In order to achieve the above object, the fixed position stop control device of the present invention relates to fixed position stop control of a load driven and displaced by an electric motor, and provides a speed command that outputs a slow speed command signal to the electric motor together with a fixed position stop command. a stop position command circuit that outputs a stop position setting signal for the load; and a stop position command circuit that outputs a stop position setting signal for the load and a position detection signal for the load output from a position detector interlocked with the electric motor. an automatic position adjuster that calculates and outputs a speed command signal for position correction based on the deviation of the signal; and a speed of the electric motor that takes one of the speed command signals for position correction and slow speed command as a selective input. In the load fixed position stop control device comprising a control drive device, the speed of the electric motor is reduced to the slow speed command value and the position of the load is within a predetermined deviation peak with respect to the set stop position. Under the condition that the speed command signal for the drive device is switched from the slow speed command signal to the position correction speed command signal, and further, the deviation between the two signals at the time of switching is set as an initial value and an appropriate time characteristic is set. A signal processing circuit is provided that adds a compensation signal that changes depending on the speed to the position correction speed command signal to perform stepless switching between the two speed command signals.

[Effect]

Generally, when a control system receives an input signal that changes more rapidly than its own response time constant, the output of the control system repeats over- and under-control with the target value specified by the input signal. Converge. Conversely, the output of the control system follows well the input signal that changes over a sufficiently long time compared to the response time constant. In other words, the input followability of the control system output is determined by the relative relationship between the response time constant specific to the control system and the fluctuation time or period of the input signal.

Incidentally, the most rapid input fluctuation occurs during step-like changes.

In the present invention, when switching the input signal to the drive device of the electric motor from the slow speed command signal A to the position correction speed command signal B which is smaller than the signal A, the present invention provides a deviation A between the two signals at the switching instant. -B as an initial value, and by adding to the signal B a speed command compensation value that attenuates to zero with an appropriate first-order or higher-order delay time characteristic, the signal A
A signal processing circuit is provided for smoothly transitioning from signal B to signal B steplessly and with appropriate time changes, thereby suppressing excessive horn input disturbance to the position control system and achieving smooth stop control.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the invention, FIG. 2 is a circuit diagram of the signal processing circuit in FIG. 1, and FIG. 3 is an input/output operation waveform diagram in FIG. 1.

In FIG. 1, the same reference numerals are given to components having the same functions as in the prior art embodiment shown in FIG. 4.

In FIG. 1, the input signal switching circuit 4 in the block diagram shown in FIG. 4 is replaced with a signal processing circuit 8 shown in FIG.

In FIG. 2, SW1 to SW4 are switches, 9 is a signal voltage comparator, R is a resistor, and C is a capacitor. Further, A and B are the aforementioned speed command signals given in a voltage state, and E is a selection signal for either one of the A and B signals.

Next, the operation of the circuit shown in FIG. 2 will be explained in relation to FIG. 1. Now, when a fixed position stop command is given, switch SW
, and SW, and are closed circuit SW, and SW.

is opened, and the slow speed command signal A from the speed command circuit 1
is immediately outputted as the signal E and inputted to the drive device 5, and the electric motor 6 enters deceleration operation.

Next, on condition that the speed of the electric motor is reduced to the value specified by the command signal A and the load position has reached the vicinity of the position specified by the stop position setting signal from the stop position command circuit 2, the switch SWl is opened. is closed. At this time, the switches SW3 and SW4 remain closed and open, respectively. Therefore, the control system for the load shifts from a speed control system based on the signal to a position control system using the position signal as a target value.

At the time of the above control system transition, the terminal voltage of the capacitor C, which had been charged in accordance with the value of the signal, decreases with a first-order lag time characteristic due to charge discharge via the resistor R and other circuit resistances. Therefore, the signal E, which is equal to the terminal voltage, also decreases.

The position correction speed command signal B and the signal E are compared by a comparator 9, and when the two signals become substantially equal, the switch SW3 is opened and the signal 8w4 is closed, and the signal is passed through the switch SW4. The signal B is then output as a signal E. Therefore, the input signal E to the drive device 5 transitions steplessly from the signal A to the signal B with a first-order delay time characteristic, and output fluctuations caused by input switching of the position control system are suppressed.

FIG. 3 is an operational waveform diagram showing the above relationship.

The solid line in the figure shows the speed command signal E, and the dotted line shows the signal E.
The speed of the electric motor 6 according to Further, tl is the time when the fixed position stop command signal is applied, and t2 is the switching time of the recontrol system.

Therefore, the above time 1. Between and tt, the speed is controlled, and the signal E is equal to the signal A. After time t2, the position is controlled, and the signal E is the sum of the signal B and a first-order delay compensation signal for the signal B. Become.

As shown in the figure, fluctuations in the motor speed immediately after time t2 when the control system switching operation is performed are suppressed due to the command signal having the above characteristics, and smooth stop position control becomes possible.

〔Effect of the invention〕

According to the present invention, regarding fixed position stop control of a load driven by an electric motor, there is provided a fixed position stop control device having a speed control system and a position control system that switch and share the driving device of the electric motor. When transitioning to stop position control to bring the load to a predetermined position after deceleration, the command signal for the drive device is changed from a slow speed command signal for the speed control system to a position correction speed command signal for the position control system of an appropriate order. The transition can be made steplessly and smoothly according to the delay time characteristics, and therefore transient fluctuations in both the speed and position caused by switching the control system are suppressed, and smooth fixed-position stop control of the load becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram of the signal processing circuit in FIG. 1, FIG. 3 is an operation waveform diagram corresponding to FIG. 1, and FIG. A block diagram showing the embodiment, FIG. 5 is an operation waveform diagram corresponding to FIG. 4. 1... Speed command circuit, 2... Stop position command circuit, 3
... Automatic position adjuster, 4... Switching circuit, 5... Drive device, 6... Electric motor, 7... Position detector, 8...
-Signal processing circuit, 9...Comparator, C...Capacitor, R...Resistor, SWI'~SW4...Switch. Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1) Regarding fixed position stop control of a load that is driven and displaced by an electric motor, a speed command circuit that outputs a slow speed command signal for the electric motor together with a fixed position stop command, and a stop position command that outputs a stop position setting signal for the load. an automatic positioning circuit that receives a position detection signal of the load outputted from a position detector linked to the electric motor and the stop position setting signal, and calculates and outputs a speed command signal for position correction based on a deviation between the two signals. A fixed position stop control device for the load, comprising a regulator, and a drive device for controlling the speed of the electric motor, which receives either one of the speed command signals for the position correction and the slow speed command as a selective input. In this step, the speed command signal to the drive device is controlled to slow down to the slow speed command value on condition that the speed of the electric motor is reduced to the slow speed command value and the position of the load is within a predetermined deviation range from the set stop position. Switching from the speed command signal to the speed command signal for position correction, and adding a compensation signal that changes with appropriate time characteristics to the speed command signal for position correction, with the deviation between the two signals at the time of the switching as an initial value. A fixed position stop control device comprising a signal processing circuit that performs stepless switching between the two speed command signals.