JP2006158031A - Motor controller and control method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller having a diagnosis function for accurately diagnosing a failure. <P>SOLUTION: The motor controller is provided with a position controlling section 4 for controlling a position and outputting a speed instruction based on the motor position and a position instruction from a motor position detector 5, a speed controlling section 3 for controlling a speed and outputting a torque instruction based on the motor speed found from the motor position and the speed instruction, a current controlling section 2 for outputting a current instruction based on the torque instruction, a position/speed instruction converting section 9 for inputting the position instruction and outputting the speed instruction, a subtractor for finding a difference between the speed instruction and the motor speed, a probability density estimating section 13 for calculating and estimating a probability density function from the difference signal 12, and a failure detecting section 14 for generating a warning if the monitored probability density function is abnormal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor control apparatus mainly used for robots, machine tools, and the like, and more particularly to a motor control apparatus having an abnormality diagnosis function and a control method thereof.

As an example of diagnosing the occurrence of an abnormality using a probability density function in a conventional motor control device, for example, a “motor control device having a diagnosis function” disclosed in Patent Document 1 can be cited. FIG. 3 is a block diagram of a motor control device having a conventional diagnostic function. A position / speed control unit 24 inputs a motor position (Pfb) 6 detected by a position detector (encoder) 5 to obtain a target Position control and speed control are performed so that the position and the position 6 coincide with each other, and a torque command 23 is output to the current control unit 2 to drive the motor 1.
The probability density function calculator 25 receives the torque command 23 and calculates the standard deviation of the probability density function of the torque command. The abnormality diagnosis unit 26 issues an alarm when the standard deviation exceeds a certain level (threshold value), enabling diagnosis that is not affected by noise.
However, in this motor control device, since the abnormality diagnosis is performed by the probability density function of the torque command, the compensation torque can be obtained even when abnormal vibration occurs when feedback control is not used or when the gain in feedback control is low. Abnormality detection was difficult because it was not generated.
A circuit that improves this is the “motor control device having a diagnostic function” disclosed in Patent Document 2. FIG. 4 is a block diagram of the motor controller with a diagnostic function. The probability density function calculation unit 35 inputs the motor position Pfb, calculates the standard deviation of the probability density function of the motor position, and the standard deviation σPfb is a threshold value. Since an alarm is issued when the value exceeds the limit, an abnormality diagnosis can be performed even when no compensation torque is generated.

Next, for comparison with the diagnostic apparatus shown in the control block diagrams of FIGS. 3 and 4 above, an example of control for detecting a load failure by detecting the state of the machine (load) with a sensor will be described. . FIG. 5 is a block diagram of a failure detection system that uses a conventional sensor. This is a control example in which the state of a machine (load) connected to a motor and operating is detected by the sensor, and an abnormality diagnosis is performed. 2 shows a vibration detection system of the bearing 38 using When the load 37 is driven by the motor 39, the vibration in the bearing 38 is detected by the vibration sensor 41. The probability density function of the signal is calculated / estimated by the probability density estimation block 42 using the signal from the sensor 41. In this case, a special sensor 41 is further required on the load side.
FIG. 6 is a block diagram of “a machine operation state monitoring device using a motor as a power source and a method for diagnosing a machine abnormality using a motor as a power source” disclosed in Patent Document 3, and FIG. 6 is also a diagram of the load machine of FIG. It is a control system that detects a state using a sensor, and is a monitor device that performs an abnormality diagnosis of a transport device for a press machine as a load machine. This monitor device measures the amount of motion of a power measuring device 61 that measures the power consumption of the motor 51, a rotation angle measuring device 62 that detects the rotation angle of the rotating shaft 53, and an operation part (press transport machine) 55. An operation amount sensor 63 is provided, and the monitor device main body 64 stores a table in which the power consumption, the rotation angle, and the operation amount are associated with each other in the storage device 65, and obtains a probability density function of the power consumption and performs anomaly measurement. It is.
Japanese Patent Laying-Open No. 2003-70287 (FIG. 1) JP 2003-348886 A (FIG. 1) Japanese Patent Laid-Open No. 9-198123 (FIG. 1)

However, the invention described in Patent Document 2 calculates the probability density function based on the motor position Pfb by improving the drawbacks of the invention described in Patent Document 1 using the probability density function of the torque command. Even if the device does not generate compensation torque, it is possible to perform abnormality diagnosis with few false detections due to temporary noise, etc., but if the load condition or the speed conversion value of the position command changes, the probability density function also changes. As a result, there is a problem that it is difficult to accurately detect the failure state.
In the case of the device shown in FIG. 5 or the invention described in Patent Document 3 shown in FIG. 6, since it is a monitor device for the entire operating system of the load machine and requires a special sensor, Patent Documents 1 and 2 are used. There is a problem that the control system is different from this device and the device and control are complicated.
Accordingly, the present invention has been made to solve these problems, and a probability density function using a difference between a position / speed command and a speed instead of a motor position by using a simple configuration that does not require a special sensor or the like. Therefore, even if the control device does not generate a compensation torque for an abnormality without being affected by changes in the load condition or speed profile, the motor control device with an abnormality diagnosis function is less likely to be erroneously detected due to temporary noise or the like. The purpose is to provide.

In order to achieve the above object, an invention according to claim 1 relates to a motor control device, a position control unit for performing position control by a motor position and a position command from a motor position detector and outputting a speed command, and the speed command In a motor control device including a speed control unit that outputs a torque command by performing speed control from a motor speed obtained from a motor position, and a current control unit that outputs a current command from the torque command, the position command is input. A position / speed command conversion unit that outputs a speed command; a subtractor that determines a difference between the speed command and the motor speed; a probability density estimation unit that calculates and estimates a probability density function from the difference signal; and the probability density function And a failure detection unit that issues an alarm if abnormal.
According to a second aspect of the present invention, there is provided a motor control method, wherein position control is performed based on a motor position and position command from a motor position detector, a speed command is output, and a torque command is transmitted by speed control based on the speed command and motor speed. In the motor control method of driving and driving the motor by outputting a current command from the torque command, a position command is input and a speed command is output in a position / speed command conversion unit, and the speed command and the motor are output by a subtractor. Obtaining a difference from the speed, and estimating and calculating a probability density function from the difference and performing failure detection, the failure density is detected by estimating and calculating the probability density function in a section where the speed is constant. It is said.

  With the above configuration, it is possible to accurately detect an abnormality with few false detections due to temporary noise, etc., even when the compensation torque of the control device does not occur for the abnormality without being affected by changes in load conditions or speed profiles. The safety of the system is guaranteed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a motor control device of the present invention.
In FIG. 1, the servo control unit includes a motor 1, a current control unit 2, a speed control unit 3, and a position control unit 4. Feedback 6 (Pfb) from the encoder 5 is transferred to the position control unit 4 and the feedback position / speed conversion unit 7 that transfers it to the speed control unit 3.
The probability density estimation unit 13 calculates / estimates the density distribution of the difference signal 12 of the difference between the feedback speed (Sfb) 11 and the position / speed command 10. The position / speed command 10 is obtained by converting the position command 8 by the position / speed command conversion unit 9. The probability density function is used for failure detection by the failure detection unit 14 together with other statistical information of the difference signal 12.

FIG. 2 is a diagram showing a plot of the speed command and the feedback speed shown in FIG. In FIG. 2, the X-axis 15 represents time in seconds, and the Y-axis 16 represents speed in rotations / second. The difference between these speed commands 17 (equivalent to 10 in FIG. 1) and speed 18 (equivalent to 11) is used to calculate / estimate and generate a probability density function.
For fault detection, the probability density function is calculated along with other parameters such as standard deviation, average, kurtosis, skewness of the difference signal 12. The analysis of the difference signal (or calculation of the probability density function) is performed in the section from A19 to B20 or from A′21 to B′22 shown in FIG. It can be seen from FIG. 2 that this section represents a data range in which the speed conversion value 17 of the position command is constant. The difference signal 12 of this interval is used to calculate the probability density function and other statistical parameters of the sample data for intervals A to B (or A ′ to B ′), allowing stable calculation.
Therefore, if the distribution parameter is monitored in the stable region A19 to B20 (or A′21 to B′22), reliable failure detection is performed by setting a threshold value for the probability density function and other parameters by the failure detection unit 14. It becomes possible.

  Because of the above configuration, it is not affected by changes in load conditions or speed profiles, and accurate abnormality detection with few false detections due to temporary noise even when control device compensation torque does not occur for abnormality. Therefore, the present invention is suitable for use in a motor control device such as a robot or a machine tool as a motor control device with an accurate failure diagnosis function.

It is a block diagram of the data control device concerning the present invention. It is a figure which shows the plot of the speed instruction | command shown in FIG. 1, and a feedback speed. It is a block diagram of the motor control apparatus provided with the conventional diagnostic function. It is a block diagram of the conventional motor control apparatus with a diagnostic function. It is a block diagram of the failure detection system using the conventional sensor. It is a block diagram of the operation state monitoring apparatus of the machine which uses the conventional motor as a power source, and the abnormality diagnosis method of the machine which uses a motor as a power source.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 2 Current control part 3 Speed control part 4 Position control part 5 Encoder 6 Feedback signal 7 Feedback position / speed conversion part 8 Position command 9 To position / speed command conversion part 10 Position / speed command 11, 18 Feedback speed 12 Difference signal 13 Probability density estimation unit 14 Failure detection unit 17 Speed command

Claims (2)

A position control unit that performs position control based on the motor position and position command from the motor position detector and outputs a speed command, and a speed control that performs speed control based on the motor speed obtained from the speed command and the motor position and outputs a torque command And a motor control device including a current control unit that outputs a current command from the torque command,
A position / speed command conversion unit that inputs the position command and outputs a speed command, a subtractor that obtains a difference between the speed command and the motor speed, and a probability density estimation that calculates and estimates a probability density function from the difference signal And a failure detection unit that monitors the probability density function and issues an alarm if abnormal, a motor control device.   Position control is performed based on the motor position and position command from the motor position detector, a speed command is output, torque command is output based on speed control based on the speed command and motor speed, current command is output based on the torque command, and the motor is In the driving motor control method, the position / speed command conversion unit inputs the position command and outputs the speed command, the subtractor obtains the difference between the speed command and the motor speed, and the probability density estimation unit calculates the difference from the difference. A motor control method characterized by estimating and calculating the probability density function and performing failure detection in a section where the speed is constant when performing failure detection by estimating and calculating a probability density function.

Images