JP4835606B2 - Rotating body phase / speed detector - Google Patents

Description

  The present invention relates to an apparatus for detecting the rotational position (phase) / speed of a rotating body such as a motor by an encoder and a phase / speed detection circuit, and in particular, phase / speed detection by a square wave pulse and phase / speed detection by a sine wave signal. The present invention relates to a detection device for switching between

  In an inverter that controls the speed of a motor, as a phase / speed detection method that enables the speed feedback control and position feedback control, etc., by detecting the motor speed (speed) / phase with an encoder and phase / speed detection circuit, There are the following two methods.

  (1) A system in which an encoder that outputs a square wave pulse is coupled to a rotating body, and the speed is detected from the number of edges (phase) and the time of occurrence of the edge based on each edge information of the square wave pulse.

  In this velocity detection method using a square wave pulse, as shown in FIG. 5, a case where velocity is detected using a square wave pulse signal of two phases (A and B phases) having a phase difference of 90 ° will be described below. In general, the built-in type calculation is performed at a fixed cycle, and the detection process operates at a fixed cycle like the phase / speed calculation in FIG. In order to detect the speed, a phase deviation in a certain period and a time required for the phase deviation are required. In a general square wave pulse detection method, the previously detected phase and time are stored, and speed calculation is performed using the phase and time of the latest pulse of this time.

  In the example of FIG. 5, the pulse information at the time Ta detected last time is stored, and the calculation is performed using the pulse information at the time Tb obtained by the current detection. Since the phase difference between these two pulses is 5, it takes Tb-Ta to generate the phase difference for 5 pulses, so that the speed can be detected with K × 5 / (Tb-Ta) ( K is a detection coefficient obtained from the number of pulses per rotation).

  The merit of this method is that (a) a pulse having only two states of ON / OFF is handled, so that digital handling is easy and the detection circuit becomes simple. (B) If the delay is constant, the filtering process is easy. (C) The accuracy is relatively good. In the case of FIG. 5, since four 4f edges are used in one pulse period, the phase difference of the A / B phase and the accuracy of the duty of each phase are required. However, there is a method using a precise 1f edge. is there.

  Further, (a) phase information is not known unless a pulse edge comes. Therefore, the phase between pulses cannot be detected. (B) It is necessary to measure the time of the pulse edge. (C) Since the pulse does not come in the low speed region, the phase and speed detection accuracy in the low speed region cannot be increased.

  (2) A system in which an encoder that outputs a sine wave signal is coupled to a rotating body, sine wave information obtained by analog detection is pulsed, the phase between the pulses is detected, and the pulse information is highly accurate. In this method, the phase of a pulse can be obtained at an arbitrary time, and phase detection and speed detection can be detected with high accuracy.

  In the speed detection method based on this analog detection, as shown in FIG. 6, the case where the speed is detected using a two-phase (A, B phase) sine wave pulse signal having a 90 ° phase difference is shown below.

  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. 6). Therefore, the speed can be obtained by (θa−θb) / (Ta−Tb) using Ta and Tb at the start time of each calculation cycle (this does not need to be measured and may be an interrupt cycle of calculation).

  The merit of this method is as follows: (a) Since the instantaneous pulse phase is known, the current accurate phase is known. (B) Since the calculation cycle matches the time difference when the speed is calculated, time management becomes unnecessary. (C) Since the instantaneous pulse phase is known even in the low speed range, the phase and speed detection accuracy is good.

  Disadvantages are: (a) Analog / digital conversion of the detection circuit is required. (B) When an analog filter is inserted, a delay occurs at a high frequency, so that the filter cannot be inserted so much. (C) The accuracy may drop due to analog noise or analog / digital conversion errors. (D) In the case of a high frequency, it is necessary to shorten the calculation cycle or reduce the number of pulses per rotation. If the pulse is rotated by 180 ° or more per calculation cycle, it is not known whether the rotation is normal or reverse. Further, when a plurality of pulses come per calculation cycle, there is no means for counting the pulses.

As a method for solving these problems, as shown in FIG. 7 with an encoder and a phase / speed detection circuit, a sine wave pulse (digital data) and a square are obtained from A and B phase sine waves with a phase difference of π / 2 from the sine wave encoder. A system that detects both wave pulses, detects position information of one pulse or more by a square wave pulse, detects position information of less than one pulse by a sine wave pulse, and combines the two to detect the position and the number of rotations. (For example, refer to Patent Document 1 and Patent Document 2).
Japanese Patent Application Laid-Open No. 07-229756 JP 2006-234688 A

  Motors with inverters and encoders that are controlled based on motor phase / speed detection signals are not necessarily installed in close locations, but are installed in remote locations and connected between them with signal cables There are many. In this case, a filter is inserted in the phase / velocity detection circuit to remove noise induced in the signal cable or the like.

  When a filter is inserted at the detection circuit input end portion indicated by F1 in FIG. 7, since the entire input signal is filtered, there is no phase shift between the square wave pulse and the sine wave pulse, but a high rotational speed. In the case of detecting up to 1, the frequency of the pulse becomes several hundred kHz, so a filter having a very large time constant cannot be inserted. Therefore, if a filter with a small time constant is used, noise remains in the analog conversion value for detecting a sine wave pulse, and a detection error occurs.

  When a filter is inserted in the input end portion of the A / D converter indicated by F2 in FIG. 7, only the A / D conversion value is filtered, so that highly accurate detection is possible. However, since a phase difference is generated between the square wave pulse and the sine wave pulse, the consistency between them cannot be obtained. In this case, erroneous detection may occur in units of one pulse, and a phase jump occurs. This phase jump has a great adverse effect on speed detection.

  For the above reasons, the encoder and the detection circuit are relatively close to avoid the inconvenience caused by inserting a filter in the F1 portion (detection circuit input end) or the F2 portion (A / D converter input end). The design required for the arrangement was required or the detection performance was lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a phase / velocity detection device for a rotating body capable of detecting phase / velocity with improved accuracy of phase / velocity detection in a wide speed range and compensating for phase shift generated by signal processing of a detection circuit. There is.

  In order to solve the above-described problems, the present invention performs phase / speed detection using a square wave pulse when the rotating body is in a high-speed rotation region, and performs phase / speed detection using a sine wave signal in a low-speed rotation region. For phase detection, a phase of one or more rotations of the rotating body is set by a square wave pulse, and a phase detection value by a sine wave signal is set to 1 according to the phase advance / delay between the square wave pulse and the sine wave pulse. It is designed to increase or decrease by the amount of pulses, and has the following configuration.

(1) a sine wave encoder coupled to a rotating body to obtain A and B phase sine wave signals having a phase difference of π / 2;
Conversion to square wave pulses having an edge at the zero cross point of the A and B phase sine wave signals, the number of pulses counted by the pulse counter, and the counting of the time counter starting from the pulse edge With the pulse counter and time counter to obtain the pulse phase corresponding to the pulse width,
A phase / velocity detection circuit using a square wave pulse for detecting the phase / velocity of the rotating body from the number of square wave pulses obtained by the pulse counter / time counter;
A phase converter for removing noise components from the A and B phase sine wave signals, converting these sine wave signals into A / D conversion data, and obtaining a phase from the A / D conversion data;
The phase / velocity of the rotating body is detected from the analog phase obtained by the phase converter, and when a phase shift occurs between the pulse phase and the analog phase, the pulse phase is present in the higher-order digits of the analog phase. A phase / velocity detection circuit based on a sine wave signal that corrects the pulse phase to match a pulse phase in which the analog quadrant in which the analog phase exists exists ,
In the high-speed region where the speed of the rotating body exceeds the preset speed, the output of the phase / speed detection circuit by the square wave pulse is used as the phase / speed detection value, and the speed of the rotating body is lower than the set speed. In the region, a changeover switch that uses the output of the phase / speed detection circuit based on the sine wave signal as a phase / speed detection value,
It is provided with.

(2) The phase / velocity detection circuit based on the sine wave signal has the phase advance / delay when there is a phase advance / delay between the pulse phase based on the square wave pulse and the analog phase based on the sine wave signal. In accordance with the above, there is provided means for increasing or decreasing the upper digit of the analog phase by one cycle of the sine wave signal.

  As described above, according to the present invention, when the rotator is in the high-speed rotation region, phase / speed detection is performed using a square wave pulse, and in the low-speed rotation region, phase / speed detection is performed using a sine wave signal. The phase for one rotation or more of the rotating body is set by a square wave pulse, and the phase detection value by the sine wave signal is set for one pulse according to the phase advance / delay between the square wave pulse and the sine wave pulse. Therefore, the accuracy of phase / speed detection can be improved over a wide speed range by switching between phase / speed detection using a square wave pulse and sine wave signal, and the phase shift caused by the signal processing of the detection circuit can be improved. Compensated phase / speed detection is possible.

  FIG. 1 is a configuration diagram of a phase / velocity detection apparatus showing an embodiment of the present invention. Basically, a phase / velocity detection method using a sine wave signal and a square wave pulse is switched.

  The sine wave encoder 1 coupled to a rotating body such as a motor generates two A and B phase sine waves having a frequency and a phase difference of π / 2 according to the rotational speed and position of the rotating body, as in FIG. To do. The converters 2A and 2B have hysteresis characteristics and convert them into square-wave pulses having edges at the zero cross points of the A and B phase sine waves.

The pulse counter / time counter 3 is a pulse phase corresponding to the pulse width by counting the number of square wave pulses output from the comparators 2A and 2B by the pulse counter and counting by the time counter starting from the pulse edge. Ask for. The phase / speed detector 4 detects the phase / speed of the rotating body from the number of pulses obtained by the pulse counter / time counter 3.

  The low-pass filters 5A and 5B perform noise cut on the A and B phase sine waves from the encoder 1. These low-pass filters 5A and 5B may be CR filters or filters using an OP amplifier, and those having a time constant that can sufficiently cut noise are selected (however, the switching speed by speed detection is not affected. No value).

The A / D converter 6 converts the sample values of the A and B phase sine wave signals input via the low-pass filters 5A and 5B alternately into a digital signal. The phase converter 7 obtains the phase θ = tan ⁻¹ (B / A) from the two A and B phase sine wave data having the phase difference π / 2 from the A / D converter 6.

The phase / speed detector 8 detects the phase and speed of the rotating body based on the analog value from the phase θ from the phase converter 7. Since the phase at this time is reset to 0 ° for each rotation of the rotating body, by performing upper digit correction (digit setting in units of 360 °) by the number of pulses counted by the pulse counter / time counter 3, Find the rotational position according to the rotational speed.

  The change-over switch 9 switches to a detection value from the phase / speed detector 4 by pulse when the rotating body rotates at high speed, and switches to a detection value from the phase / speed detector 8 by analog value at low speed rotation. This switching is controlled with a preset speed as a boundary.

  Hereinafter, characteristic items according to the present embodiment will be described.

(1) Compensation of phase shift by low-pass filter In the configuration of FIG. 1, since a low-pass filter 5A, 5B for noise cut and comparators 2A, 2B are inserted in the analog detection portion, a square wave pulse and a sine wave pulse are generated by these filters. In this case, a phase shift occurs, but the influence on the detection accuracy due to this phase shift is avoided by switching by the selector switch 9.

  The filters 5A and 5B cause a delay in the detection phase based on the analog value, but a large delay occurs only during high-speed rotation. During low-speed rotation, highly accurate analog detection values can be used even at low speeds for the following reasons.

  (A) Since the phase shift due to the delay time of the low-pass filter is small at low speed, the influence on the phase detection accuracy is small.

  (B) Because of the low speed, many pulses do not come between control cycles, and there is no need to expand to more than one pulse between control cycles.

  Therefore, speed detection based on analog values is used in the low speed range. In the high rotation range, the above (a) and (b) become problems, so the speed is switched to pulse detection. Since a sufficient number of pulses enter in the high rotation range, speed detection using pulses can be detected more stably.

  As described above, switching between speed detection using pulses and speed detection using analog at a predetermined speed enables accurate detection at both low and high speeds.

  In particular, it is effective in a field where speed control performance in a low speed region is required, such as an elevator or a dynamometer.

(2) Phase shift compensation between analog detection and pulse detection In phase / velocity detection based on analog values, the upper digits of the phase / velocity detector 8 are corrected with the number of pulses counted by the pulse counter / time counter 3 to achieve as much accuracy as possible. A good analog detection value can be stably obtained up to a high rotational speed.

Here, since the comparators 2A and 2B convert a sine wave pulse into a square wave pulse, a hysteresis comparator is usually used to prevent chattering near the zero cross. However, if there is hysteresis, a shift occurs between the detection phase by the square wave pulse and the detection phase by the sine wave signal . 2A shows the relationship between the input sine wave signal and the output pulse signal of the comparator when there is no hysteresis, and FIG. 2B shows positive and negative pulse edge positions so as to show the relationship when there is hysteresis. Causes a phase shift.

This phase shift appears as a shift in the timing of upper digit correction in the phase / speed detector 8 and affects the accuracy of the detected phase. In order to prevent this phase shift, the phase / velocity detector 8 uses the shifted pulse phase to match the shifted pulse phase with the analog phase, thereby correcting the upper digit of the analog phase. This correction algorithm will be described in detail below.

  FIG. 3 shows an example of a detection phase shift due to the occurrence of a phase shift in waveform. The phase relationship between the A and B phase sine waves is represented by quadrants 0 to 3 as shown in FIG. 4. If there is no phase shift by the comparators 2A and 2B with respect to the A and B phase sine waves, a square wave pulse is obtained. Will have edges at 0 °, 90 °, 180 ° 270 °, 360 °. When there is no phase shift, the output of the phase converter 7 outputs the phase A phase and analog quadrant (0-3) information as shown in FIG. The information of the pulse quadrant and pulse phase to be sent to the phase / velocity detector 8 by value is generated.

  Here, when there is hysteresis in the comparators 2A and 2B, as shown in FIG. 3, when a delay or advance phase shift occurs in the output, the digit output of the counter 3 is compared with the analog phase output of the phase converter 7. It is shifted by p (+) and p (−). As a result, the detection phase of the phase / velocity detector 8 decreases or increases by 360 °.

  In the phase shift compensation by hysteresis, the purpose of phase / velocity detection is to apply an analog detection value up to a high rotation speed, so the output of the counter 3 is based on the analog phase output from the phase converter 7 as a reference. The detected phase is corrected by the pulse that becomes. This correction algorithm will be described.

(A) Definition of Phase First, the definition of the analog quadrant is as shown in FIG. 4, and the pulse quadrant is a quadrant as shown in FIG. 3 determined by the pulse edge. In FIG. 3, there is a case where the analog quadrant and the pulse quadrant do not coincide with each other due to the deviation of the pulse phase.

As shown in FIG. 4, the phase 1.0 is defined on the basis of a pulse of 1f ( one cycle of the sine wave signal ), the analog phase 360 ° is defined as the phase 1.0, and the analog phase 0 to 360 ° is set to 1. Expressed with less than 0.0. That is, 360 ° = detection phase 1.0. For example, a detection phase of 450 ° is expressed as 1.25 (360 ° × 1.25 = 450 °). The pulse phase is counted by 4f (four) pulses, and 4f of 4f = analog detection phase 1.0. Further, it is assumed that when the pulse phase is detected, it can be determined whether a pulse edge is generated by forward rotation or a pulse edge is generated by reverse rotation.

(B) Phase detection method The detection phase value is obtained by setting the detection phase counted at 4f as the integer part (0, 1, 2,...) And the analog detection phase as the decimal part. For example, in P of FIG. 3, since the pulse phase is 1 and the analog phase is 0.25, the detection phase is 1.25.

(C) Correction algorithm A phase shift occurs at the boundary between quadrant 0 and quadrant 3. Since the cause is a pulse phase shift, the analog phase is given priority at the boundary between quadrant 0 and quadrant 3. The following correction is performed only under the following conditions, and is not performed when the conditions are not satisfied (for example, when the pulse quadrant and the analog quadrant coincide).

  In the region A in FIG. 3, there is a pulse quadrant and an analog quadrant, and therefore no correction is performed.

In the region B of FIG. 3, when the pulse quadrant is 3 and the analog quadrant is 0, the detection phase of the pulse quadrant is corrected by +1 because of the forward rotation edge. Further, when the pulse quadrant is 3 and the analog quadrant is 0, the detected phase of the pulse quadrant is corrected by +1 if it is a reverse edge.

If the pulse quadrant is 0 and the analog quadrant is 3, and if it is a reverse edge, the detection phase of the pulse quadrant is corrected by -1. Further, in the region C of FIG. 3, when the pulse quadrant is 0 and the analog quadrant is 3, if the edge is a forward rotation edge, the detection phase of the pulse quadrant is corrected by −1.

  Therefore, even when a phase error between analog detection and pulse detection occurs, the error generated at the boundary between quadrant 0 and quadrant 3 can be corrected to perform phase detection using high-precision analog.

The block diagram of the phase and speed detection apparatus which shows embodiment of this invention. An example of a phase shift between a sine wave signal and a pulse signal. The wave form diagram of the detection phase by phase shift generation | occurrence | production. The relationship figure of the sine wave phase of A, B phase and quadrants 0-3. Explanatory drawing of the phase and speed detection by a square wave pulse. Explanatory drawing of the phase and speed detection by a sine wave pulse. The block diagram of the conventional encoder and a phase and speed detection circuit.

Explanation of symbols

1 Sine Wave Encoder 2A, 2B Comparator 3 Pulse Counter / Time Counter 4 Pulse Phase / Speed Detector 5A, 5B Low Pass Filter 6 A / D Converter 7 Phase Converter 8 Analog / Phase Detector / Speed Detector 9 Changeover Switch

Claims (2)

A sine wave encoder coupled to a rotating body to obtain A and B phase sine wave signals with a phase difference of π / 2;
Conversion to square wave pulses having an edge at the zero cross point of the A and B phase sine wave signals, the number of pulses counted by the pulse counter, and the counting of the time counter starting from the pulse edge With the pulse counter and time counter to obtain the pulse phase corresponding to the pulse width,
A phase / velocity detection circuit using a square wave pulse for detecting the phase / velocity of the rotating body from the number of square wave pulses obtained by the pulse counter / time counter;
A phase converter for removing noise components from the A and B phase sine wave signals, converting these sine wave signals into A / D conversion data, and obtaining a phase from the A / D conversion data;
The phase / velocity of the rotating body is detected from the analog phase obtained by the phase converter, and when a phase shift occurs between the pulse phase and the analog phase, the pulse phase is present in the higher-order digits of the analog phase. A phase / velocity detection circuit based on a sine wave signal that corrects the pulse phase to match a pulse phase in which the analog quadrant in which the analog phase exists exists ,
In the high-speed region where the speed of the rotating body exceeds the preset speed, the output of the phase / speed detection circuit by the square wave pulse is used as the phase / speed detection value, and the speed of the rotating body is lower than the set speed. In the region, a changeover switch that uses the output of the phase / velocity detection circuit based on the sine wave signal as the phase / velocity detection value,
A device for detecting a phase / speed of a rotating body. When the phase / velocity detection circuit based on the sine wave signal has a phase advance / delay between the pulse phase based on the square wave pulse and the analog phase based on the sine wave signal, the phase / velocity detection circuit 2. The phase / velocity detection device for a rotating body according to claim 1, further comprising means for increasing or decreasing the upper digit of the analog phase by one period of a sine wave signal.

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