JP2004180451A - Detecting method for magnetic pole of servo motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the accuracy by eliminating any friction in a mechanism when an initial magnetic pole position is determined by rotating a rotor in forward and backward directions. <P>SOLUTION: The detecting method for the magnetic poles of a servo motor is such that after the rotor is stopped once, a magnetic pole detecting current (A) is applied again in the forward and backward directions to rotate the rotor in the forward and backward directions. The position in which the rotor stops again is taken as the initial magnetic pole position. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic pole detection method of a servomotor, and particularly, when determining an initial magnetic pole position of a rotor, in order to reduce a position error due to friction of a rotating shaft, the rotor is rotated forward and reverse to estimate a magnetic pole, that is, an initial magnetic pole position. Regarding new improvements to decide.
[0002]
[Prior art]
Conventionally, as a magnetic pole detection method of this kind of servomotor used, it is used only for in-house products, and does not disclose patent documents and non-patent documents showing the contents.
In general, in the case of a servo motor, an encoder is attached to a U, V, W three-phase drive type motor, and U, V, W phase switching signals output from the encoder, two-phase incremental signals A, B, and an origin. And the two-phase incremental signals A and B without using the U, V, and W phase switching signals, that is, the magnetic pole position signals, to estimate the magnetic pole (ie, the magnetic pole position). Out) and drive.
The present invention relates to the latter method, and the conventional method is as follows.
That is, at the initial drive of the servomotor, the magnetic pole position of the rotor is unknown, so that at the time of initial magnetic pole extraction, the rotor is stopped at a predetermined magnetic pole position, and a predetermined three-phase current amount or pattern is used. When a current of a current command as a predetermined magnetic pole starting current is applied, the rotor stops after rotating according to the current.
The three-phase drive is performed with the stop position where the rotor stops as the predetermined magnetic pole position and the position as the origin.
[0003]
[Problems to be solved by the invention]
Since the conventional magnetic pole detection method of the servomotor is configured as described above, the following problems exist.
In other words, the rotor that rotates by applying the magnetic pole output current has friction (disturbance) on a mechanism such as a rotating shaft, so that the stop position of the rotor is shifted from the expected magnetic pole position, that is, the initial magnetic pole position. Was.
In the case described above, the control driver side of the servo motor cannot detect the deviation of the stop position because the magnetic pole sensor is not provided in the motor, and an error in the magnetic pole estimation, that is, the magnetic pole position determination occurs. This has an adverse effect on the driving of the motor and the control of the rotating system.
[0004]
The present invention has been made in order to solve the above-described problems.In particular, when determining the initial magnetic pole position of the rotor, in order to reduce a position error due to friction of the rotating shaft, the rotor is rotated forward and reverse. It is an object of the present invention to provide a magnetic pole detection method for a servomotor in which a magnetic pole is estimated, that is, an initial magnetic pole position is determined.
[0005]
[Means for Solving the Problems]
The magnetic pole detection method of the servo motor according to the present invention, when the initial magnetic pole position is determined by controlling the servo motor using a two-phase incremental signal of the encoder without a magnetic pole sensor, a predetermined magnetic pole output current is supplied to the servo motor. The initial magnetic position is determined as a stop position of the rotor of the servo motor as a position corresponding to the magnetic pole output current, and then the initial magnetic pole position is added and subtracted by a counter with the two-phase incremental signal as a count value. In the magnetic pole detection method of the servo motor to be obtained, after the rotor is stopped once, the magnetic pole output current is applied again in the forward and reverse directions to rotate the rotor forward and backward, and the initial position is determined using the position where the rotor is stopped again. This is a method of setting the magnetic pole position.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of a magnetic pole detection method for a servomotor according to the present invention will be described with reference to the drawings.
The U-, V-, and W-phase three-phase brushless motors with encoders used in the present invention are not shown because they are well known.
Although not shown, the brushless motor has no magnetic pole sensor, uses only a two-phase incremental signal from an encoder, counts the two-phase incremental signal with a counter (not shown), and estimates a magnetic pole position based on the count value. It is configured as follows.
[0007]
First, when the rotation of a rotor (not shown) is controlled using a two-phase incremental signal from an encoder for the servomotor, when an initial magnetic pole position is determined, a preset current amount or current pattern is used. Is applied as a current command Icom, and the initial magnetic pole position is determined by setting the stop position of the rotor as a position corresponding to the applied current ratio of the magnetic pole extraction current A. The initial magnetic pole position is added or subtracted by the two-phase incremental signal as a count value of a counter (not shown), and the initial magnetic pole is positioned (the same as the conventional one until the above).
[0008]
In the above-described case, after the rotor is stopped by applying the magnetic pole outgoing current A, a slight current is applied again from the stop position (for example, 300 degrees in FIG. 1) in the left-right direction, that is, in the forward / reverse direction, so that the rotor is stopped. May be reciprocated in the forward and reverse directions (to improve accuracy by performing several times) to reduce the influence of friction on bearings and the like, and finally use the stopped position. The initial magnetic pole position is determined using all the positions where the operation has been performed a plurality of times and stopped (for example, an average value is obtained).
Therefore, it is possible to reduce an error due to the influence of friction or the like, as compared with the conventional case where the current is determined by a single current application.
[0009]
As described above, the state in which the current is applied in the forward and reverse directions in FIG. 1 to rotate the rotor in the forward and reverse directions changes as indicated by the arrow in FIG.
Further, in the above-described series of operations, as shown in FIG. 3, an initial magnetic pole is set in the first step 100 (conventional method). The current is applied to either of them to rotate the rotor), and in a third step 102, the stop of the motor is confirmed.
[0010]
Further, in the fourth step 103, an electric angle is formed in the same manner as described above. In the fifth step 104, the stop of the motor is confirmed, and the stop position of the rotor is determined as the final initial magnetic pole position. Although the electric angulation is performed twice in the above, it is not limited and is optional. Further, the final positioning can be performed by taking an average value using not only the last stop position but also all the stop positions in the middle as described above.
[0011]
【The invention's effect】
The magnetic pole detection method for a servomotor according to the present invention is configured as described above, and therefore, can provide the following effects.
That is, a predetermined magnetic pole current is applied to form an electrical angle for the rotation of the rotor, and after the rotor is stopped, a current is applied again to rotate the rotor forward and reverse. Errors can be eliminated, and the initial magnetic pole position can be determined much more accurately than in the past.
[Brief description of the drawings]
FIG. 1 is a current waveform diagram illustrating a magnetic pole detection method of a servomotor according to the present invention.
FIG. 2 is an explanatory diagram of a state in which the operation of FIG. 1 is viewed as a rotor.
FIG. 3 is a flowchart showing the operation of FIGS. 1 and 2;
[Explanation of symbols]
A Magnetic pole output current

Claims (1)

When a servo motor is controlled using a two-phase incremental signal of an encoder without a magnetic pole sensor and an initial magnetic pole position is determined, a predetermined magnetic pole starting current (A) is applied to the servo motor, and the rotor of the servo motor is rotated. The initial magnetic position is determined by setting the stop position of the magnetic pole as a position corresponding to the magnetic pole output current (A), and then the magnetic pole of the servo motor is obtained as a count value by adding and subtracting the initial magnetic pole position with a counter using the two-phase incremental signal. In the detection method,
After the rotor has stopped once, applying the magnetic pole output current (A) in the forward and reverse directions again to rotate the rotor forward and backward, and using the position where the rotor has stopped again to set the initial magnetic pole position. Characteristic magnetic pole detection method of servo motor.

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