JP2010014410A - Rotational position detecting apparatus of rotator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the rotational position of a rotator as an absolute value and accurately detect rotational positions, over a wide range of speed. <P>SOLUTION: A sine-wave output encoder generates sine-wave signals or pulse signals of A, B phases and C, D phases having a phase difference π/2, according to the rotation of a shaft 1 of the rotator by gear wheels 2 and 3 and tooth sensors 4 and 5. The number of sine waves or the number of pulses generated per rotation of the rotator is different by one, between the A, B phases and the C, D phases. Detectors 8 and 9 detect the intra-pulse phases (AB) of the A, B phases and the intra-pulse phases (CD) of the C, D phases. A subtractor 10 detects their phase difference (BD) as an absolute value of the rotational position (phase) of the rotator during a single rotation. The number of sine waves or the number of pulses generated for one rotation of a motor is different by the number of pole pairs of the motor, when the rotational position of the motor is detected, on the basis of the electrical angle (phase) per pole. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus that detects a rotational position (phase) of a rotating body such as a motor with an incremental encoder, and more particularly to an apparatus that detects the rotational position of the rotating body with an absolute value.

  When a synchronous motor (PM motor) using a permanent magnet is driven at a variable speed by an inverter, the rotational position of the magnetic pole (rotor) is detected with an absolute value in order to accurately control the torque, and with high accuracy in a wide speed range. It needs to be detected. In general, the following are known as detectors for detecting the rotational position (phase) and rotational speed of a rotating body.

(1) Absolute value encoder This is an absolute value encoder used when the rotational position is detected by an absolute value (see, for example, Patent Document 1). The encoder types include (a) incremental encoder, (b) serial absolute encoder, and (c) resolver, which will be described in detail below.

  (A) The incremental encoder is an encoder that outputs a plurality of pulses per rotation, and outputs the following three types of signals as shown in FIG.

  -The speed and direction of rotation can be detected in the A and B phases of multiple pulses / rotation with a phase difference of 90 degrees (π / 2).

  -The absolute position during one rotation can be specified with a Z-phase pulse of 1 pulse / revolution.

  ・ The U, V, and W signals, which are turned ON / OFF by 180 degrees during one rotation and shifted by 120 degrees, can specify the rotation position within an error of 60 degrees when the inverter device is powered on.

  The advantages of this incremental encoder are that the detection device is simple (just check the ON / OFF state of the pulse), and by using a square wave pulse, the filter can be easily inserted and is resistant to noise. On the contrary, since the demerit is generally square wave pulse information, information can be obtained only at the rising edge of the signal, so that a discretization error occurs in detection. Further, since an error of ± 30 degrees is generated at the time of starting the power source, the detected position error is large until the Z phase is detected, and the output torque accuracy is deteriorated.

  (B) The serial absolute encoder detects one rotation with a resolution of 17 bits or 20 bits, and detects an absolute position (rotational position) by communicating the encoder and the inverter device with a serial signal.

  The advantage of this serial absolute encoder is that the rotational position can be detected with high resolution. Similarly, the rotational position can be detected with high resolution when the inverter device is powered on. On the contrary, since the optical system is generally adopted as a disadvantage, it cannot cope with high rotation due to mechanical strength. Moreover, since serial communication is performed, there is a limit in real-time property.

  (C) The resolver applies a high-frequency AC voltage based on substantially the same principle as a transformer, and the output voltage amplitude changes or the output phase changes depending on the rotational position of the rotating body.

  The advantage of this resolver can be detected with a resolution that depends on the analog detection resolution. Similarly, when the inverter apparatus is powered on, detection can be performed with a resolution that depends on the analog detection resolution. In addition, because of its strong structure, it can be used even at high speeds. Conversely, the demerits are complicated in principle and the detection circuit is also complicated. Also, since analog signals are handled, the influence range of malfunction due to noise is wide (unit of one rotation (mechanical angle / electrical angle)). That is, noise countermeasures are required in a wide range.

(2) Sine wave output encoder Incremental encoder that generates a two-phase (A / B phase) sine wave with a phase difference of 90 degrees at a frequency proportional to n times (n is a positive integer) the rotation period of the rotating body. FIG. 8 shows a case where the speed is detected from a signal in which one cycle of the sine wave is one pulse.

  This sine wave output encoder can detect the phase between pulses by obtaining the sine wave information of the pulse by analog detection, and can improve the accuracy of the pulse information. Thus, there is a method in which the phase of the pulse is obtained at an arbitrary time and the phase detection and the speed detection are detected with high accuracy (see, for example, Patent Document 2).

  Since it is a sine wave, the instantaneous pulse phase is known. Therefore, the phase at the start of the phase / velocity calculation is accurately known, and the phase difference between the current time and the previous time is accurately known in units of less than one pulse (θa and θb in FIG. 8).

FIG. 9 shows a schematic configuration of the incremental encoder. A gear GW is pivotally supported on an output shaft AX of a rotating body whose rotational position is to be detected, such as a motor, and a plurality of teeth T are arranged or formed at equal intervals along the circumferential direction of the gear GW. . The tooth sensors S _A and S _B are arranged in the circumferential direction of the gear GW at positions facing the teeth T, and the timing at which the teeth T become the positions of the tooth sensors S _A and S _B by the rotation of the gear GW is defined as edges or vertices. A-phase and B-phase pulse signals (FIG. 7) or sine wave signals (FIG. 8) are generated.

The tooth T of the gear is, for example, made of iron in an electromagnetic encoder and a disk provided with a slit in an optical encoder. The tooth sensors S _A and S _B have a conversion circuit configuration that converts a change in magnetic resistance due to the approach of the tooth T into an electric signal in an electromagnetic encoder, and the optical encoder electrically transmits and blocks light transmitted by the tooth T. A conversion circuit configuration for converting the signal is used.
Japanese Patent No. 3858593 JP 2001-124588 A

  In order to accurately control the torque of a motor (rotating body) such as an inverter that drives a PM motor from a low speed to a high speed, the rotational position can be detected even at low speeds. Resolver that can be used.

  However, since the resolver uses the principle of a transformer, a high frequency power source for excitation is required, and a structure in which primary / secondary windings are accurately arranged is required for detection with high accuracy. Therefore, it becomes a complicated and expensive detector.

  Incremental encoders are cheaper than resolvers and have high rotational position detection accuracy over a wide speed range, but the A / B phase two-phase output cannot detect rotational positions (absolute values). Application for the above uses has been difficult.

  An object of the present invention is to provide a rotational position detection device for a rotating body that can detect the rotational position of the rotating body with an absolute value using an incremental encoder and that can accurately detect the rotating position in a wide speed range. .

  In order to solve the above-described problems, the present invention provides two incremental encoders in which the number of sine waves or pulses generated per rotation of a rotating body that is a rotational position detection target is different from each other by one or the number of pole pairs of the rotating body. / B phase signal and C / D phase signal are obtained, and the absolute value of the rotational position (phase) or electrical angle during one rotation from the phase difference between the A / B phase pulse and the C / D phase pulse And is characterized by the following configuration.

(1) a first incremental encoder that generates an A or B phase sine wave signal or pulse signal having a phase difference of π / 2 according to the rotation of a rotating body that is a rotational position detection target;
A sine wave signal or pulse signal having a phase difference of π / 2 is generated according to the rotation of the rotating body, and the first incremental encoder is the number of sine waves or pulses generated per one rotation of the rotating body. A second incremental encoder having a different number,
The phase difference (BD) between the A and B phase phases (AB) and the C and D phase phases (CD) is detected as the absolute value of the rotational position (phase) of the rotating body during one rotation. And a rotational position detecting circuit.

(2) a first incremental encoder that generates an A or B phase sine wave signal or pulse signal having a phase difference of π / 2 according to the rotation of a motor that is a rotational position detection target;
C and D phase sine wave signals or pulse signals with a phase difference of π / 2 are generated according to the rotation of the motor. The first incremental encoder has a sine wave number or a pulse number generated per motor rotation. A second incremental encoder that differs by the number of pole pairs of the motor;
The phase difference (BD) between the A and B phase phases (AB) and the C and D phase phases (CD) is detected as the absolute value of the electrical angle (phase) per pole of the motor. And a rotational position detection circuit.

(3) The rotational position detection circuit includes:
A position correction amount calculator for obtaining a correction position (E) of the sensor of the incremental encoder with respect to the phase (AB), (CD) in the pulse and the magnetic pole position of the rotating body or the motor;
An adder for adding the attachment position correction amount (E) to the phase difference (BD) and correcting the absolute position of the rotation position detection signal to the reference position of the rotating body or motor;
It is provided with.

  (4) The rotational position detection circuit includes a disconnection detection unit that detects disconnection from at least two phases to a rotation of the rotating body or the motor from a signal change of the A, B, C, and D phases. It is characterized by that.

  As described above, according to the present invention, two incremental encoders differing in the number of sine waves or pulses generated per rotation of a rotating body that is a rotational position detection target from each other or by the number of pole pairs of the rotating body. Phase signal and C / D phase signal are obtained and detected as the rotational position (phase) or absolute value of electrical angle during one rotation from the phase difference between the A / B phase pulse and the C / D phase pulse. As a result, the rotational position of the rotating body can be detected as an absolute value using two inexpensive incremental encoders, and the rotational position can be accurately detected in a wide speed range.

(Embodiment 1)
FIG. 1 is a configuration diagram of a rotational position detection device showing the present embodiment. Two gears 2 and 3 are pivotally supported on the output shaft 1 of a rotating body whose rotational position is to be detected, such as a motor, and electromagnetic or optical tooth sensors are respectively radially provided on the outer peripheral surfaces of these gears 2 and 3. 4 and 5 are arranged, and the combination of the gears 2 and 3 and the tooth sensors 4 and 5 constitutes two sine wave output encoders.

  The rotational position detection circuit includes A / D converters 6 and 7 for sampling A / B phase and C / D phase sine wave signals from the tooth sensors 4 and 5 and converting them into digital signals, and an A / D converter. In-pulse phase detectors 8 and 9 for detecting the A / B phase in-pulse phase (AB) and the C / D phase in-pulse phase (CD) from the converted outputs of 6 and 7, and the in-pulse phase (AB) ( Subtractor 10 for obtaining a rotational position detection signal of an absolute value by obtaining a phase difference (BD) of CD), and a tooth sensor (incremental encoder sensor) for the phase (AB), (CD) and the magnetic pole position of the rotating body in the pulse. The position correction amount calculator 11 that calculates the attachment position correction amount (E) of 4 and 5 and the attachment position correction amount (E) are added to the absolute rotation position detection signal (phase difference BD) to obtain the magnetic pole position of the rotating body. Correct the absolute rotation position detection signal to Constituted by an adder 12.

  Here, the operation will be described with a sine wave output encoder in which the outputs of the A phase, the B phase, the C phase, and the D phase are sine waves. The gear 2 and the tooth sensor 4 generate an A / B phase sine wave signal having a phase difference of 90 degrees according to the rotation of the gear, and the gear 3 and the tooth sensor 5 are a C / D phase having a phase difference of 90 degrees according to the rotation of the gear. Generates a sine wave signal. Further, the number of teeth of the C / D phase gear 3 is different from that of the A / B phase gear 2 by one.

  If the number of teeth in the A / B phase is N and a signal of 360 degrees can be generated with one tooth, the tooth sensor 4 generates a signal of 360 × N degrees with one mechanical rotation of the shaft 1. be able to. On the other hand, if the number of teeth in the C / D phase is N-1, which is one less than that in the A / B phase, a signal of 360 × (N−1) degrees can be generated by one mechanical rotation. The rotational position (phase) during one rotation can be detected as an absolute value using (360 degrees).

For example, the number of teeth of the gear 2 that generates the A / B phase is 12 and 12 pulses are output per rotation, and the number of teeth of the gear 3 that generates the C / D phase is 11 and 11 pulses are output per rotation. In this case, the signal waveform of each part is as shown in FIG. From the sine wave output obtained from the A / B phase, an A / B phase intra-pulse phase (AB) that outputs 360 degrees per tooth is obtained. When tan ⁻¹ (B phase amplitude / A phase amplitude) having a cycle of 180 degrees is obtained from the A / B phase, 90 degrees is added when the A phase is positive, and 270 degrees is added when the A phase is negative. / B phase in pulse (AB) can be obtained. Similarly, the phase (CD) in the C / D phase pulse can be obtained from the C / D phase. Then, the phase difference between the A / B phase pulse phase (AB) and the C / D phase pulse phase (CD) is obtained as shown in the phase difference (BD) of FIG.

  The phase difference (BD) waveform of the intra-pulse phase shown in FIG. 3 is 0 degrees when the horizontal axis is X and the intersection of the intra-pulse phase (AB) and (CD) is X1, X2,. As shown in Figure 1, the expression representing the detection phase (Y-axis) and mechanical rotation position (X-axis) for each period of ˜360 degrees should be expressed as Y = X when (AB)> (CD). When (CD)> (AB), it can be expressed as Y = X-360 degrees. The detection phase and the position of one mechanical rotation need to be set to Y = X. Therefore, when (CD)> (AB), correction (E) to add +360 is performed. The position during one rotation is known, and the rotational position is also known when the inverter device is powered on even in the incremental encoder.

(Embodiment 2)
When detecting the position of the motor, there are a case where it is desired to detect a mechanical angle of 0 to 360 degrees per rotation and a case where it is desired to detect an electrical angle of 0 to 360 degrees per the number of pole pairs of the motor. In this case, as shown in the first embodiment, by reducing the number of teeth by the number of pole pairs, a mechanical angle of (360 degrees × number of pole pairs) can be detected by one rotation, and an electrical angle of 0 to 360 degrees per pole can be detected. It can be detected.

  In the present embodiment, an electrical angle of 0 to 360 degrees per one pole of the motor is detected by reducing the number of teeth of the gear 3 by the number of pole pairs of the motor with respect to the gear 2 in FIG.

  For example, when the motor has 4 poles (= pole pair number 2) and the A / B phase has 12 teeth, each part waveform is as shown in FIG. In this case, since the number of teeth in the A / B phase is 12, the output pulse is 12, whereas the number of teeth in the C / D phase is 10 and the output pulse is 10.

  Further, when the difference between the phase in the A / B phase pulse (AB) and the phase in the C / D phase pulse (CD) is taken, the phase difference (BD) shown in FIG. 5 is obtained.

  Therefore, in this embodiment, the in-pulse phase difference = rotation position can be obtained by the same algorithm as in the first embodiment.

(Embodiment 3)
In the first and second embodiments, the two detection systems of the gears 2 and 3 and the tooth sensors 4 and 5 can be used to simultaneously detect the position and speed of the rotating body.

  In the present embodiment, by using two detection systems, as shown in FIG. 6, the A / B / C / D phase signal changes during motor rotation by the disconnection detection unit 13 added to the rotational position detection circuit. To at least two lines are detected.

  Since all four phases change from moment to moment with respect to the motor rotation, it is possible to detect that the rotation is performed with the other two wires even if the second wire is broken. Detects disconnection of up to 2 lines from / C / D phase data. In this regard, in the case of a conventional apparatus that uses only the A / B phase, it may be impossible to detect whether the motor is stopped or rotating. Regardless, disconnection can be detected.

  In addition, although Embodiment 1-3 demonstrated so far demonstrated by the number of teeth of A / B phase 12, this number of teeth should just be arbitrary positive integers which can be implement | achieved.

  Further, although the case of a sine wave output encoder has been shown, similar effects can be obtained by using an incremental encoder that outputs pulses. In this case, the A / D converters 6 and 7 need only binarize the A / B phase signal and the C / D phase signal with a comparator.

The block diagram of the rotation position detection apparatus which shows embodiment of this invention. The signal waveform example of each part in FIG. The phase difference (BD) waveform example of the phase in a pulse of FIG. An example of a signal waveform for detecting an electrical angle per pole of a motor. The phase difference (BD) waveform example of the phase in a pulse of FIG. Configuration example of disconnection detection. Example of output waveform of incremental encoder. Waveform example of sine wave output encoder. The schematic block diagram of an incremental encoder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating body output shaft 2, 3 Gears 4, 5 Tooth sensor 6, 7 A / D converter 8, 9 In-pulse phase detector 10 Subtractor 11 Attached position correction amount calculator 12 Adder

Claims (4)

A first incremental encoder that generates A or B phase sine wave signals or pulse signals with a phase difference of π / 2 according to the rotation of a rotating body that is a rotational position detection target;
A sine wave signal or pulse signal having a phase difference of π / 2 is generated according to the rotation of the rotating body, and the first incremental encoder is the number of sine waves or pulses generated per one rotation of the rotating body. A second incremental encoder having a different number,
The phase difference (BD) between the A and B phase phases (AB) and the C and D phase phases (CD) is detected as the absolute value of the rotational position (phase) of the rotating body during one rotation. And a rotational position detection circuit for rotating the rotational body. A first incremental encoder that generates an A or B phase sine wave signal or pulse signal with a phase difference of π / 2 according to the rotation of a motor that is a rotational position detection target;
C and D phase sine wave signals or pulse signals having a phase difference of π / 2 are generated in accordance with the rotation of the motor. The first incremental encoder has a sine wave number or pulse number generated per one rotation of the motor. A second incremental encoder that differs by the number of pole pairs of the motor;
The phase difference (BD) between the A and B phase phases (AB) and the C and D phase phases (CD) is detected as the absolute value of the electrical angle (phase) per pole of the motor. A rotating position detecting device for a rotating body, comprising: a rotating position detecting circuit. The rotational position detection circuit
A position correction amount calculator for obtaining a correction position (E) of the sensor of the incremental encoder with respect to the in-pulse phase (AB), (CD) and the magnetic pole position of the rotating body or motor;
An adder for adding the attachment position correction amount (E) to the phase difference (BD) and correcting the absolute position of the rotation position detection signal to the reference position of the rotating body or motor;
The rotational position detecting device for a rotating body according to claim 1 or 2, further comprising:   The rotational position detection circuit includes a disconnection detection unit that detects disconnection from at least two phases to signal rotations of the A, B, C, and D phases with respect to rotation of the rotating body or motor. The rotational position detecting device for a rotating body according to claim 1 or 2, characterized in that:

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