JPS62290380A - Absolute encoder - Google Patents

Abstract

PURPOSE:To obtain a small-sized lightweight position-speed detector, by forming a unit into an absolute encoder in a counter method. CONSTITUTION:To a rotating body 1 fitted to the rotating shaft of a brushless DC motor are provided scale patterns 2 and 4 to generate the pulses in specified number in one rotation of a rotating body 1 and a scale pattern 3 with one pulse output in one rotation of a rotating body 1. Detection circuits 1-3 outputs electric pulses of two-phase pulse, exciting phase and a zero-marker from each scale pattern. An updown counter is reset by a zero marker, processing a two-phase signal in pulse logic and counting ups and downs according to the rotating direction of the rotating body 1. A data conversion circuit makes up motor exciting angle data from exciting phase signals. A data selector selects for output either exciting angle data after data conversion or absolute angle data a counter output.

Description

Detailed Description of the Invention [1] Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to an absolute encoder that is attached to the rotating shaft of a brushless DC motor.

(Prior Art) Brushless DC motors require rotor position detection in order to detect the rotor base pole and switch the excitation phase of the stator. Conventionally, in a brushless DC motor, a method such as using a Hall element for detecting magnetic flux density has been generally adopted in order to detect a rotor position signal using a field image. In addition, for the purpose of improving speed ripple at low speeds, etc., the rotor position is detected by an absolute encoder, and the motor drive voltage is determined by calculation from the absolute angle. Then, from the output signal of the absolute encoder, ′oi,
It has great advantages, such as being able to detect speed. death,
However, absolute type encoders with high precision and high resolution have a large number of pulse pattern tracks and are large in size.In addition, in the case of a combination of an incremental type encoder and a counter, the time from immediately after power is turned on until zero marker detection is There was a drawback that the count value was not determined and a separate rotor position detection means was required to drive the brushless DC motor.

(Problems to be Solved by the Invention) This invention solves the problem because the position of the rotor is unknown immediately after the power is turned on in the above-mentioned counter-type absolute encoder.
The object of the present invention is to provide a small and lightweight position/speed detector that has improved the drawback that the motor cannot be driven.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a rotating body attached to the rotating shaft of a brushless DC motor with n and n in one rotation of the rotating body.

(n, , r12 are positive integers, respectively) scale patterns 1 and 2 are provided, and scale pattern 3 is provided to generate one pulse output per one rotation of the rotating body. Detection circuit 1 to obtain electrical pulse signals of phase pulse, excitation phase, and zero marker
3 and the zero marker, the counter performs pulse logic processing on the two-phase signal and counts up and down depending on the direction of rotation of the rotating body, and the data conversion circuit that creates motor excitation angle data from the excitation phase signal indicates that the power has been turned on. It consists of a power-on reset circuit that detects, and a data selector that selects and outputs the excitation angle data after data conversion and the absolute angle data of the counter output.

(Function) The function of the absolute encoder of this invention will be explained with reference to FIG. Three types of scale patterns are recorded on the rotating body attached to the motor shaft. The scale pattern 1 is a relatively high pulse, and the detection circuit 1 detects the scale pattern 1 and generates two-phase clock pulses having a phase difference of 90 degrees in electrical angle. The rotational direction determining circuit determines the rotational direction of the motor shaft from the two-phase clock pulses generated by the detection circuit 1, and outputs up/down pulses to the counter. On the other hand, scale pattern 3 is 1 of the rotating body.
A signal of one pulse is recorded for each rotation, and the detection circuit 3 detects the scale pattern 3 and outputs a zero marker for each rotation of the motor shaft. The up/down counter counts the output of the rotation direction discrimination circuit and is reset by the zero marker. Therefore, if the number of count bits of the counter is set appropriately, the value of the counter will indicate the absolute angle of the rotating body within one revolution. Also, s)7-
In /L/ pattern 2, signals corresponding to the number of magnetic poles of the motor are recorded, and the detection circuit 2 outputs multiphase pulses corresponding to the number of phases of the motor. The data conversion circuit converts the multiphase pulse data into an absolute angle signal corresponding to the magnetic pole to be excited. The data selector selects and outputs the absolute angle data of the counter output and the excitation angle data of the data conversion circuit output, but when the power is turned on, the excitation angle data side is switched by the output of the power-on reset circuit, and during normal operation, the excitation angle data side is switched by the zero marker. absolute angle data. Power-on Lyceum 1 visit! komasutenyu 4~shi1 shumo ZL surface #lr 憔台door 1 Aki'-ta selector works to select excitation angle data. In this way, immediately after the encoder power is turned on, an excitation switching signal corresponding to the number of poles of the motor is output instead of absolute data, and the brushless DC motor can be excited. Then, the zero marker is detected within one rotation of the motor, and from then on, normal absolute angle data is output.

(Example) Here, a case will be described in which the motor is attached to a brushless DC motor having a three-phase eight-pole winding structure and has one scale pattern and 1024 pulses/rotation.

Since the motor has 8 magnetic poles, the voltage waveform when driving the motor with a sine wave voltage is null as shown in Figure 2 (al).Scale pattern 1 is 1024 pulses in 10D rotation, and detection circuit 1 converts this into electrical angle. It is detected as a 2-phase incremental signal with a 90 degree phase shift, and the rotation direction discrimination circuit discriminates the direction, multiplies this 2-phase signal by 4, and outputs it to the counter circuit.For this reason, the counter is 12b (4096 pulses). When prepared, the counter value will output the absolute angle of the motor rotor as a binary signal in both forward and reverse directions.In steady state operation, the motor driver calculates the sine wave voltage according to the angle from the motor rotor position. It can be applied to each phase of U, V, and W of the winding.

In scale pattern 2, a signal of 4 pulses/rotation corresponding to 8 poles/2 is recorded according to the number of magnetic poles of the motor. The detection circuit 2 detects the signal as a three-phase signal with a phase shift of 120 degrees in electrical angle. The logical waveform is as shown in FIG. 2 (bl). The data conversion circuit converts the three-phase signals into absolute angle data as shown in the table.

Since the margin motor driver performs excitation switching according to this angle, the motor can be driven with a square wave voltage pattern as shown in FIG. 82(C). Since this pressure sending pattern is symmetrical every 90 degrees in mechanical angle, the conversion circuit only needs to output data within 90 degrees.

The zero marker is used to reset the engine in the steady state and to change the speed from the power-on state to the steady state.

FIG. 3 schematically shows the rotating body of this embodiment.

Note that the rotating body used in the present invention may be of any shape, such as a disk or a drum. Further, the detector may be of an optical type or a magnetic type.

The two-phase pulse described in this embodiment only needs to obtain a two-phase waveform of an electric signal, and the pattern shape of the scale pattern 1 and the detection method of the detection circuit 1 are not limited. Therefore, even a method of detecting two-phase scale patterns using detectors of the same phase does not depart from the scope of the present invention.

〔Effect of the invention〕

Because it is a counter type absolute encoder,
The rotating body can be made small and lightweight. Even during a period when the absolute angle is uncertain immediately after the power is turned on, the motor can be excited without the need for any other detector and without making any modifications to the motor driver. Since it automatically returns to the absolute encoder from the initial state, there is no need for an external reset signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the invention in detail. FIG. 2 is a waveform diagram of various parts depending on the rotation angle of the motor shaft, and FIG. 3 is a schematic diagram showing each scale pattern recorded on the rotating body. 1...Rotating body, 2...Scale pattern 1.3...
・Scale pattern 2.4...Scale pattern 3゜Representative Patent attorney Nori Chika Yudo Takehana Masahisa

Claims (1)

[Claims] The absolute encoder is attached to the rotating shaft of a brushless DC motor and counts up and down the incremental pulses and resets with a zero marker to obtain absolute data regarding the rotation angle.The absolute encoder is used to detect the position of the motor rotor and to switch the excitation current to control the motor. In this configuration, in addition to the incremental pulses and the zero marker, a scale pattern is provided to obtain an output signal that matches the number of magnetic poles of the motor, and the absolute data is determined by the zero marker immediately after the encoder power is turned on. An absolute encoder that is capable of outputting the excitation switching signal necessary for motor drive even in transient conditions.