JP2939763B2 - Position control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention [Industrial Application Field] The present invention relates to a position control device, and in particular, uses a potentiometer as a position detection element, and collides a load end with a stopper to mechanically perform an operation. And is used as a remote control device such as a medical device.

[Prior Art] FIG. 2 shows an example of the configuration of a position control device conventionally used for remote control of medical equipment and the like, 1 is a power supply for position signals, 2 is a potentiometer, 3 is a control motor, Is a control circuit, and 5 and 6 are limit switches for setting the upper and lower limits of the operation of the load terminal.

The illustrated position control device includes a motor 3 for controlling the position of the load end and a potentiometer 2 for detecting the position of the load end;
The limit switches 5 and 6 are attached to the mechanism at the load end,
The control circuit 4 is connected to the control circuit 4 by an electric wire, and the position command voltage of the control circuit and the output voltage of the potentiometer are compared by a comparison circuit provided in the control circuit, and the motor is driven in a direction in which the output voltage of the comparison circuit becomes zero. By rotating, the load end is controlled to the commanded position.
Is configured to stop the motor regardless of the output voltage of the comparison circuit when the load end reaches the upper or lower limit of rotation, so that the load end is not driven beyond the rotation limit due to malfunction of the comparison circuit etc. The operation point of the limit switch is determined as the origin of the operation.

[Problems to be Solved by the Invention] However, the limit switches 5, 6 in the configuration shown in FIG.
Is mounted on the mechanism, and many wires (eight in the example shown) are required between the mechanism and the control circuit. The operating point of the limit switch is set by the drive shaft at the load end and the limit switch. The relative position of the operating point is mechanically determined, and the setting of the operating point requires adjustment by a skilled technique, and there is a problem that it cannot be easily changed.

Therefore, a position control device has been proposed in which the load end collides with a stopper without providing a limit switch, and the operation is mechanically locked, and the position is set as the operation origin, and the origin position can be freely set. However, since the signal of the origin position is not sent to the control device, there is a problem that control based on the origin cannot be performed.

Therefore, a command for searching for the origin is issued to the control device, and when a drive command is given to the electric motor, a change with time of the output voltage of the potentiometer is detected, and a position at which the change with time has disappeared is determined as the origin. The output voltage of the potentiometer at that time is stored in a memory provided in the control circuit.

However, in the above-described configuration, the output voltage of the potentiometer may not change with time even in the case of a failure of the mechanical unit. Therefore, it is possible to obtain a control device having a configuration capable of diagnosing such a failure. Is the challenge.

(2) Configuration of the Invention [Means for Solving the Problems] In the present invention, when a change over time in the output voltage of the potentiometer is detected, the movement of the load end stops, and the change over time in the output voltage stops. Is defined as the origin, and the output voltage of the potentiometer at that time is stored in a memory provided in the control device, and is set as the origin. To the drive command in the opposite direction,
At this time, if the temporal change of the output voltage of the potentiometer is not less than a certain reference value, the output voltage of the potentiometer immediately before the reverse rotation of the electric motor is determined as the origin position in the direction before the reverse rotation, and stored in the memory provided in the control circuit. In addition, a configuration is provided in which a self-diagnosis function is provided for determining that the control device has failed if the value of the change over time in the output voltage of the potentiometer is less than or equal to the certain reference value when a reverse drive command is given to the motor. .

[Operation] With the above-described configuration, it is possible to perform a self-diagnosis as to whether or not the control device is faulty when the output voltage of the potentiometer has no change over time.

[Embodiment] FIG. 1 is a circuit diagram showing a configuration of a position control device embodying the present invention. The same parts as those of the prior art shown in FIG.

In the figure, 10 is an A / D converter, 12 is a comparator, 11 is a time axis generator, 13 is a microcomputer, 14 is a control circuit of an electric motor, and detects a detection voltage of the potentiometer 2 by the A / D converter 1.
The digital signal is converted into a digital signal by 0, and the reference voltage synchronized with the time-dependent change of the output voltage of the potentiometer sent from the time axis generator 11 is compared by the comparator 12, and the output of the comparator 2 is judged by the microcomputer 13; The operation of the motor 13 is controlled by controlling the control circuit 14 of the motor with the output of the computer 13.

Now, in the state where the load end is not locked, the motor rotates in a certain direction by the command of the microcomputer 13 to drive the load end in the commanded direction, and the moving amount of the load end is detected by the potentiometer 2, and the A / D The signal is converted into a digital signal by the converter 10 and compared with the reference voltage synchronized with the temporal change of the output voltage of the potentiometer sent from the time axis generator 11 by the comparator 12. The microcomputer 13 determines that the operation is normal, compares the position command value with the output voltage of the potentiometer 2 in the microcomputer 13, and outputs the electric motor from the control device 14 until the output voltage of the potentiometer matches the command value.
When the current is passed to 13 and the operation is continued, when the output position of the potentiometer reaches the command value when the command position is reached, the microcomputer 13 sends a signal to the motor to stop the motor.
Sent to 14 to stop the motor.

Next, a description will be given of a case in which a mechanical stopper is provided at a position where the load end is present so that the stopper cannot be rotated any more, and the origin at which the stopper is provided is defined as an operation origin.

The motor rotates in the commanded direction according to the command signal for searching the origin given to the microcomputer 13, and the output of the potentiometer 2 and the output of the time axis generator 11 are compared by the comparator 12, and the output of the comparator 12 is The microcomputer 13 determines that the control device is operating normally and continuously rotates the motor in the same direction. When the load end collides with the stopper, the movement of the load end is mechanically stopped, and the output voltage of the potentiometer 2 is reduced. The change with time stops, the comparator 12 detects a deviation from the output voltage of the time axis generator 11, and the microcomputer 13 determines that the stopper has been stopped by the microcomputer 13, sends a signal to stop the motor 13 to the controller 14, and outputs a potentiometer. 2 is stored in the memory, and the operation is performed so as to determine this position as the origin in the command direction at that time. After the origin is determined in this manner, all commands that rotate the original in the same direction from the origin will be processed as erroneous commands.

Further, when setting the origin in a position in the opposite direction to the previous case, similarly set the stopper at the position to be set as the origin and give a command for searching for the origin, and the motor rotates in that direction until the motor collides with the stopper. Similarly, the origin of the direction is stored in the memory.

In the position control device according to the present invention, as can be seen from FIG. 1, only the electric motor and the electric wire of the potentiometer are connected between the control device and the drive unit, and the limit switch is different from that of the prior art shown in FIG. The number of connection wires is reduced by four because the electric wire is unnecessary, and the origin can be easily set only by setting the position of the mechanical stopper, and electrical adjustment can be omitted, so the origin position can be eliminated. Can be easily changed.

Further, in the present invention, since the origin is detected by detecting a temporal change of the output voltage of the potentiometer, even if the movement of the load end is stopped due to a failure, the origin may be erroneously recognized. When the search command is input to the control device and the change over time of the output voltage of the potentiometer is smaller than a certain reference value (the sum of the conversion error of the A / D converter and its permissible value), a reverse Direction is given, and if the temporal change of the output voltage of the potentiometer is greater than the reference value, it is determined that the position is the origin in the direction immediately before giving the reverse drive command to the electric motor, and the output voltage of the potentiometer is stored in the memory. If the time-dependent change in the output voltage of the potentiometer when the motor is rotated in the reverse direction is smaller than the reference value, it is determined that the control device has failed. With a cross-sectional function, it is possible to avoid a failure at the time of misjudgment.

[Effect of the Invention] Since the position control device according to the present invention has the above-described configuration, the origin can be set and stored in the memory without providing a limit switch in the mechanism, so that the structure is simple and the mechanism is simple. The self-diagnosis function that can judge the failure of the mechanical part in a configuration that reduces the number of wires between the There is an effect that a position control device with a high degree can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a position control device embodying the present invention, and FIG. 2 is a circuit diagram of a position control device according to the prior art. Description of reference numerals 1 ... power supply of position detector 2 ... potentiometer 3
…… Electric motor, 4,14 …… Control device, 5,6 …… Limit switch, 10 …… A / D converter, 11 …… Time axis generator, 12…
... Comparator, 13 ... Microcomputer.

Claims (1)

(57) [Claims] An electric motor, a potentiometer for detecting a position of a load end controlled by the electric motor, and a control circuit for controlling the electric motor by comparing a position command value with an output of the potentiometer. In the control device, in a system in which the load end collides with a stopper and mechanically locks to determine the origin of the operation, when the control device issues a search command for an origin position in a certain direction and gives a drive command to the motor, When the change over time of the output voltage of the potentiometer falls below a certain reference value,
A reverse drive command is given to the motor, and at this time, when the output voltage of the potentiometer changes with time over a certain reference value, the output voltage of the potentiometer immediately before the reverse rotation of the motor is returned to the origin position in the direction before the reverse rotation of the motor. If the value of the change over time in the output voltage of the potentiometer is less than the above-mentioned reference value when a reverse drive command is given to the electric motor, the control device fails. And a self-diagnosis function for judging the position. (However, the reference value is the sum of the conversion error of the A / D conversion device built in the control device and its allowable error.)