JP2003070287A - Motor controller with diagnostic function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, since the threshold of a time series waveform is employed as a criterion for deciding the occurrence of an abnormality, a decision is made that an abnormality has occurred when the waveform is increased temporarily by noise, and when a large threshold is set in order to avoid the problem, the decision may be delayed upon the occurrence of the abnormality, or the occurrence of the abnormality may not be decided. SOLUTION: A motor controller comprises a position/speed control section 11 receiving a motor position and outputting a torque command by performing positional control and speed control such that the motor position matches a target position command, a current control section 12 receiving the torque command and outputting a current command to a motor 13 driven by the current command, and a motor position detector 14. The controller is further provided with a section 15 for receiving the torque command and operating the probability density function thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device mainly used for robots, machine tools and the like, and more particularly to a motor control device having an abnormality diagnosing function.

[0002]

2. Description of the Related Art Conventionally, as an example of diagnosing an abnormality occurrence from a motor torque in a motor control device, Japanese Patent Laid-Open No.
There is an apparatus as described in Japanese Patent No. 257668, which determines an abnormality by providing a threshold value on a time series waveform of torque.

[0003]

However, in the above-mentioned conventional example, since the threshold of the time-series waveform is used as a criterion for determining the occurrence of an abnormality, an abnormality occurs, for example, when the waveform temporarily becomes large due to noise. Even if it is not done, it is determined that an abnormality has occurred. Further, if a large threshold value is set in order to avoid this, there is a problem that the determination may be delayed when an abnormality occurs or it may not be possible to determine that an abnormality has occurred. It is an object of the present invention to provide a motor control device having a diagnosis function that does not cause an erroneous determination due to noise.

[0004]

In order to solve the above-mentioned problems, the invention of claim 1 inputs a motor position and performs position control and speed control so that the motor position coincides with a target position command. A position / speed control unit that outputs a torque command, a current control unit that inputs the torque command and outputs a current command to the motor, a motor that is driven by the current command, and a detector that detects the motor position. And a probability density calculation unit that inputs the torque command and calculates a probability density function of the torque command. In addition, claim 2
In the invention, the probability density calculation unit monitors whether or not the probability density function of the torque command is in a normal state, and issues an alarm if it is not normal. Also,
The invention according to claim 3 is characterized in that the probability density computing unit determines that the probability density function is not normal when the probability density function of the previous torque command is out of a certain distribution range. Further, in the invention of claim 4, the probability density calculation unit determines whether the probability density function of the torque command is in a normal state,
It is characterized in that a threshold is provided for the standard deviation value of the probability density function.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a motor control device to which the present invention is applied. In the figure, 11 is a position / speed control unit, which inputs the position Pfb of the motor detected by the position detector 14, performs position control and speed control so that the target position and the position Pfb match, and outputs a torque command Tref as a current. Output to the control unit. Reference numeral 12 is a current control unit, which is a torque command Tref.
Is input and a current corresponding to this is output to drive the motor 13. A probability density function computing unit 15 inputs the torque command Tref and calculates the standard deviation σ (Tref) of the probability density function of the torque command. Reference numeral 16 is an abnormality diagnosing unit, which issues an alarm when σ (Tref) exceeds a certain level. Next, a procedure for diagnosing an abnormality in the abnormality diagnosing unit 16 will be described with reference to FIG. FIG. 2 is a flowchart showing the internal processing of the abnormality diagnosis unit 16. In FIG. 2, the numerical value following S indicates a step number. In S161, the standard deviation σ (Tref) of the probability density function of the torque command is input. In S162, the σ (Tref) is input and compared with a function σ0 (Tref) that sets a threshold value of the standard deviation, and σ (Tref) ≧ σ0
If it is (Tref), proceed to S163; otherwise, proceed to S16.
Go to 4. In S163, an alarm indicating an abnormality is issued, and S164
Now continue driving. Note that in S163, measures such as an emergency stop may be taken instead of issuing an alarm. As a result, by arbitrarily setting the threshold σ0 (Tref), it is possible to perform abnormality diagnosis without determining that an abnormality has occurred even when no abnormality is constantly occurring, such as temporary noise. .

[0006]

As described above, according to the present invention, in the motor position control device, the threshold is set to the standard deviation of the probability density distribution of the torque command, so that the abnormality is diagnosed. It is possible to perform an abnormality diagnosis without determining that an abnormality has occurred when no abnormality has occurred.

[Brief description of drawings]

FIG. 1 is a block diagram showing an application example of the present invention.

FIG. 2 is a flowchart showing details of an abnormality diagnosis unit 16 in FIG.

[Explanation of symbols]

11 Position / speed controller 12 Current controller 13 motor 14 Position detector 15 Probability density function calculator 16 Abnormality diagnosis section

Claims (4)

[Claims] 1. A position / speed control unit that inputs a motor position, performs position control and speed control so that the motor position matches a target position command, and outputs a torque command,
In a motor control device including a current control unit that inputs the torque command and outputs a current command to the motor, a motor that is driven by the current command, and a detector that detects the motor position, input the torque command. A motor control device comprising: a probability density calculation unit that calculates a probability density function of the torque command. 2. The motor control according to claim 1, wherein the probability density calculation unit monitors whether or not the probability density function of the torque command is normal, and issues an alarm if the probability density function of the torque command is not normal. apparatus. 3. The motor control according to claim 1, wherein the probability density calculator determines that the probability density function of the previous torque command is not normal when the probability density function is out of a certain distribution range. apparatus. 4. The probability density calculation unit determines whether or not the probability density function of the torque command is in a normal state by setting a threshold value for the standard deviation of the probability density function of the torque command. 4. The motor control device according to claim 1, wherein the motor control device is a motor control device.