JP2644782B2 - Rotary position detector for three-phase motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a rotational position of a three-phase motor such as an AC three-phase servomotor.

2. Description of the Related Art Some magnetic pole position detecting means using an encoder determine a magnetic pole position of a motor by performing absolute position detection using an absolute signal.

Hereinafter, an AC three-phase servomotor using the above-described absolute encoder will be described with reference to the drawings.

FIG. 3 is a configuration diagram of the entire rotation position detecting device of a general three-phase motor.

In the figure, reference numeral 1 denotes an encoder which is connected to the rotating shaft of the three-phase motor 5 and generates an absolute signal. The encoder 1 is provided to face the light emitting diode 8, the rotating disk 9, the fixed slit plate 10, and each track of the rotating disk 9. And a waveform processing circuit 12 that performs waveform shaping by using an output from each light receiving element as an input.

As shown in FIG. 4, the rotating disk 9 has concentric slits formed by the necessary number of bits (6 bits in this example) toward the center with the outer periphery being the least significant bit. In the following description, a portion corresponding to the most significant bit is referred to as a first track, and the lower bit is represented as a second track, a third track,..., A sixth track.

Reference numeral 2 denotes a read-only memory (hereinafter abbreviated as ROM) from which an address is designated by an absolute signal output from the encoder 1 and three-phase current data (digital value) is read, and 3 denotes a digital value output from the ROM 2. A D / A converter 4 for converting into an analog quantity and a power transistor 4 for controlling a current to each phase of the three-phase motor.

The operation of the conventional three-phase motor rotational position detecting device using the rotating disk configured as described above will be described below.

First, the light emitted from the light emitting element 8 is modulated by the rotating disk 9 and the fixed slit 10 into a bright and dark state. The light thus modulated is converted into an electric signal by the light receiving element 11, subjected to waveform shaping by the waveform processing circuit 12, and input as a 6-bit digital signal to the ROM 2 as its address data. Then, three-phase (U-phase, V-phase, and W-phase) data values are read from the specified address of ROM2, each phase being shifted by 120 ° in electrical angle. The data value read from the ROM 2 is converted into an analog amount by the D / A converter 3, and the analog amount is amplified by an appropriate amount by the power transistor 4 to drive the three-phase motor 5.

Problems to be Solved by the Invention By the way, as shown in Table 1 on the next page, the absolute signal (alternately binary code) output by using the rotating disk 9 having the above-mentioned structure has 2 ⁶ = 64 outputs. I do.

On a rotating disk of N tracks, ^2N signals are output. For this reason, the phase difference of each phase in the three-phase motor, that is, 120 ° cannot be accurately detected.

That is, in the rotating disk 9 having the above configuration, (360 ゜ ÷ 2
^Although the position corresponding to ^N ) can be detected, the circumference cannot be accurately divided every 120 °. This occurs because the resolution of this rotating disk is 2 ^N and cannot be divided by the number “3”. Therefore, it is used for position control of a three-phase motor. When this occurs, it may cause uneven rotation and uneven torque.
In addition, the unevenness becomes larger when the resolution is low.

Means for Solving the Problems In order to solve the above problems, a three-phase motor rotational position detecting device according to the present invention is arranged such that an output signal of each track of a first track group of a rotary disk of an encoder has a rotation angle of 90 degrees. And the phase difference between the output signals of the respective tracks is 60 degrees, the output signal of the second track group is synchronized with the output signal of the first track group, and the output signal of the first track group is further changed. The first track group is formed on the inner peripheral side of the rotating disk with respect to the second track group, as well as subdivided absolute signals.

Operation With the above-described configuration, the phase difference of 120 ° between the phases of the three-phase motor can be accurately determined, and the rotation angle of each phase can be obtained as a subdivided absolute value.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a rotating disk used in this embodiment. In this embodiment, the overall configuration of the apparatus is the same as that shown in FIG. 3 (excluding the rotating disk), so that the overall configuration is not particularly shown.

In the figure, reference numeral 13 denotes a rotating disk used for generating an absolute signal.
2, a first code track group 6 composed of three tracks of the third track and a second code track group 7 composed of three tracks of the fourth, fifth and sixth tracks. .
More specifically, the first, second,
The slits of the third track are all continuous so that the center angle is 90 °, and each track is provided two at a point symmetrical with respect to the center of the rotating disk. Also, the first and second tracks are 60 ° out of phase in the clockwise direction, and the second and third tracks are out of phase by 60 ° in the same direction.

Next, the alternating binary signal generated by the rotating disk 13 shown in FIG. 1 is shown in Table 2 on the next page.

As can be seen from this table, it can be seen that the output of the signal output from the first track group changes once every 30 degrees, that is, every twelfth revolution. Therefore, in this first track group, each phase in the three-phase motor is , Ie, a phase difference of 120 ° (electrical angle) can be accurately maintained.

Further, while maintaining a phase difference of 120 ° (electrical angle) in the first track group, it can be subdivided in the second track group.

FIG. 2 is a timing chart showing the timing of the alternating binary code output from each track of the rotating disk of this embodiment.

Further, in the present embodiment, the first track group is divided into six by the electrical angle. However, the number of slits of each track of the first track group is constituted by one, and the first track group is divided every 60 °. Even if the output from is changed, the original purpose can be sufficiently achieved. In this way, if the frequency division is (3 × M (M is a natural number)), the same operation is performed and the same effect is obtained. Furthermore, a minimum of three bits including the most significant bit, that is, at least three tracks including the innermost track, which is allocated for 3 × M frequency division and subdivided by the second track group, so that even if the resolution is low, the phase difference is 120 °. (Electrical angle) can be reliably maintained.

According to the three-phase motor rotational position detecting device of the present invention, the first track group of the rotary disk of the encoder is formed on the inner peripheral side of the second track group, and each track of the first track group is formed. The output signal changes every 90 ° of rotation and the phase difference between the output signals of each track is 60 °,
The output signal of the second track group is synchronized with the output signal of the first track group, and the resolution of the output signal of the first track group is further subdivided (3 × M (M is a natural number)) for one round. With the configuration that changes every time, the three-phase motor can be driven with the phase difference between each phase maintained at 120 °, so that smooth rotation can be achieved by suppressing uneven rotation and uneven torque. This is very effective in practice.

[Brief description of the drawings]

FIG. 1 is a plan view of a rotary disk used in one embodiment of the present invention, FIG. 2 is a timing chart showing the timing of binary signals output from each track of the rotary disk shown in FIG. FIG. 1 is a configuration diagram of an entire rotation position detecting device for a three-phase motor, and FIG. 4 is a plan view of a conventional rotating disk. 2 read-only memory (ROM) 3 D / A converter 4 power transistor 5 three-phase motor 6 first code track group 7 second code track group 8 light emitting diode 10 fixed slit plate 11 light receiving element (rotation detecting element) 12 waveform processing circuit 13 rotating disk

Claims (1)

(57) [Claims] 1. An encoder having a rotating plate on which a first track group and a second track group that rotate by rotation of a three-phase motor and output an absolute signal are formed, and an encoder corresponding to the absolute signal of the encoder is provided. What is claimed is: 1. A three-phase motor rotational position detecting device comprising: a storage element for storing a current value; and a conversion element for converting a current value stored in the storage element into an analog quantity, wherein the first track of the rotary plate is provided. The group is formed on the inner circumference side of the second track group, and the output signal of each track of the first track group changes every 90 degrees of rotation angle, and the phase difference of the output signal of each track is changed. At 60 degrees, the output signals of the second track group are synchronized with the output signals of the first track group and further subdivide the resolution of the output signals of the first track group (3 .Times.M (M is a natural number)).
Phase motor rotation position detector.