JPH0424797Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a servo motor device for a manipulator, and particularly to a drive device for a slave servo motor of an electric master-slave power manipulator.

[Prior art]

This type of electric master-slave manipulator is used to manipulate dangerous materials such as radioactive materials from a distance, so the servo motor for the slave manipulator that directly manipulates dangerous materials must be small and output. It requires a large amount of power, high speed, and a small number of cables.

Conventionally, when selecting this type of motor, the speed and output rated for continuous use were used as criteria. However, most of the operations of power manipulators are intermittent motions, and moreover, they are used to send out speeds and outputs that are about 2 to 4 times the continuous rating for a short period of time without changing the size of the servo motor. This is the reality.

For this purpose, select a servo motor based on its short-time use rating, not on its continuous rating, monitor the winding temperature of the selected servo motor during use, and reduce the input current of the servo motor when the temperature rises. Control is important. However, it is very difficult to directly measure the winding temperature of a small servo motor, and a temperature detection cable must be used for each servo motor. This has the disadvantage that in addition to the required number of cables for the servo motor, the number of cables for temperature detection must be increased.

[Purpose of invention]

This invention was created to solve the above problems, and is a small size, high output, capable of intermittent operation at a speed higher than the above rated speed, and is selected based on short-time use ratings. It is an object of the present invention to provide a servo motor drive device for a manipulator with a small number of cables.

[Summary of the idea]

In order to achieve the above objects of the present invention, a slave servo motor of a manipulator is driven with a pulse width modulated current, the load current to this servo motor is detected and read into a microcomputer, and the microcomputer reads the read load current. Average processing is performed to remove noise, and the temperature rise of the servo motor winding is calculated from the result. When the winding temperature reaches an abnormal value, the limit value of the pulse width modulation is lowered and the winding temperature is increased. The structure is such that a temperature abnormality alarm is activated when the temperature value exceeds the control permissible temperature range.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. In the figure, AC power is applied to a switching circuit 2 via a rectifier circuit 1. The pulse width of the switching circuit 2 is controlled by a pulse width modulation control circuit 5. The current switched by the switching circuit 2 is supplied to the slave servo motor 4 of the power manipulator via the current detection resistor 3. The current flowing through the servo motor 4 is detected by the current detection resistor 3, and this detected current is read into the microcomputer 6 through the pulse width modulation control circuit 5. The microcomputer 6 averages the input current to remove noise, and uses the result to calculate the temperature rise of the motor windings. Note that the microcomputer 6 is provided with the following functions.

(1) A function that determines whether the input load current is below or above the rated current value.

(2) Integral calculation for calculating temperature rise when the load current is below the rated current, and function to calculate the square of the load current when the current is above the rated current.

(3) A function that gives a command 8 to the pulse width modulation control circuit 5 to control the pulse width to lower the current limit value when the winding temperature of the servo motor 4 reaches an abnormal value according to the calculation result.

(4) A function that restores the current limit value when the motor winding temperature drops to a certain temperature.

(5) A function that outputs a temperature abnormality alarm when the motor winding temperature exceeds the permissible limit range.

Next, the operation of this embodiment will be explained.

The output current of the switching circuit 2 drives the slave servo motor 4 of the power manipulator. At this time, the microcomputer 6 reads the load current of the servo motor 4 through the current detection resistor 3, averages the current to remove noise, and uses the result to calculate the winding of the servo motor 4. Calculate temperature rise. That is, (1)
Distinguish the load current into those above and below the rated current value, (2)
When the load current is less than the rated current, the current temperature is calculated by integrating the temperature within a certain period of time using a constant determined from the heat generation and heat dissipation characteristics measured in advance at the rated current. (3) When the calculated temperature reaches an abnormal value, a command signal 8 is given to the pulse width modulation control circuit 5 to lower the current limit value.
(4) When the calculated falling temperature has decreased to a certain value, a command signal 8 is sent to the pulse width modulation control circuit 5 to return the current limit value to its original state, and as described in (2) and (3) above.
Repeat the action. (5) When the load current is higher than the rated current, the rated current value is used as the initial value, and the
The temperature rise is calculated in proportion to the power of (6) When the calculated temperature rise reaches an abnormal value, the microcomputer 6 gives a command signal 8 to the pulse width modulation control circuit 5 to lower the current limit value. (7) When the calculated falling temperature falls to a certain value, a command signal 8 is given to the pulse width modulation control circuit 5 to return the current limit value to the initial value. (8) The processes of (3) to (7) above are repeatedly controlled, and a temperature abnormality alarm is issued when the control permissible temperature range is exceeded.

[Effect of idea]

As explained above, the present invention reads the current of the slave servo motor of the power manipulator read into the computer, calculates the temperature of the motor winding from this read current, and If so, reduce the drive current,
Since an alarm is issued when the control permissible temperature range is exceeded, the following practically important effects are achieved.

(1) The servo motor can be made smaller.

(2) The slave servo motor of the electric master/slave power manipulator is small and lightweight, yet capable of high speed and high output.

(3) The current number of cables used for the manipulator slave is sufficient, and there is no need to increase the number of cables.

(4) Since the load current of the servo motor is constantly monitored and this load current is controlled, there is no need to take measures against abnormalities, and the reliability of the manipulator system is improved.

[Brief explanation of the drawing]

The drawing is a block diagram showing the configuration of an embodiment of the present invention. 1... Rectifier circuit, 2... Switching circuit, 3
...Current detection resistor, 4...Servo motor, 5...
Pulse width modulation control circuit, 6...microcomputer.

Claims (1)

[Claims for Utility Model Registration] A switching circuit 2 to which rectified current of an AC power supply is supplied, a slave servo motor 4 controlled by the output of this switching circuit 2, and between this servo motor 4 and the switching circuit 2. a current detection resistor 3 inserted in the current detection resistor 3; a pulse width modulation control circuit 5 to which the current detected by the current detection resistor 3 is input and pulse width modulates the switching circuit 2; and a pulse width modulation control circuit 5 that modulates the detected current with a pulse width. A servo motor drive device includes a microcomputer 6 which calculates the winding temperature by inputting the winding temperature through the input terminal and outputs a protection operation command to the pulse width modulation control circuit 5 according to the calculation result. The input current is averaged, and if the average current is less than the rated current value, the temperature within a certain period of time is integrated using a constant determined from the heat generation and heat dissipation characteristics measured in advance at the rated current. Then, the winding temperature rise of the servo motor 4 is calculated, and when the average current is greater than the rated current value, the winding temperature rise of the servo motor 4 is calculated in proportion to the square of the average current with the rated current value as the initial value. When the winding temperature of the servo motor 4 reaches an abnormal value based on the results of both calculations, a command signal is given to the pulse width modulation control circuit 5 to lower the current limit value, and the winding calculation temperature reaches a constant temperature. A servo motor drive device for a manipulator, which gives a command signal to restore the current limit value when the current limit value decreases, and sends out a temperature abnormality alarm when the winding calculation temperature of the servo motor 4 exceeds the limit allowable range.