JPH0694756A - Correcting device for detection error of ac signal - Google Patents

Abstract

PURPOSE:To accurately control an AC signal based on a detected result by accurately detecting the signal. CONSTITUTION:Whether it is an increasing zone in which a level of an input signal of an AC signal is increased or a decreasing zone in which the level is decreased is decided. As a result, if it is decided as the decreasing zone, the level of the input signal is increased in response to hysteresis amplitudes of sensors 9, 10. If it is decided as the increasing zone, the level of the input signal is decreased in response to the hysteresis amplitudes of the sensors 9, 10. Thus, the level of the input signal is so corrected that the levels of the output signals of the sensors 9, 10 are responsive to the level of the input signal (as to eliminate hysteresis). When the corrected input signal is applied to the sensors 9, 10 in this manner, the output signal does not have the hysteresis (there is no deviation at levels in between increasing and decreasing directions). When a motor 12 is controlled by using it, it can be accurately controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC signal detection error correction device, and more particularly, to accurately control current by correcting a detection error of an AC current detection sensor used in current control of an AC motor. Related to the device.

[0002]

2. Description of the Related Art When controlling the current of an AC motor,
An AC servo motor driver (AC servo motor amplifier) or an inverter is used, and in current control by these, the current applied to the AC motor is detected as a feedback amount by a predetermined sensor. In this case, a sensor using a shunt resistor is generally used as a current detection sensor.

[0003]

However, the above-mentioned shunt resistor has a problem in terms of cost such as a large number of parts. Therefore, a current detector using a magnetoresistive element (Hall element) (hereinafter referred to as "Hall element sensor") has been recently adopted for reasons such as cost reduction. However, this Hall element sensor has a hysteresis between the current i input to the sensor and the voltage V output from the sensor, and as shown by the hysteresis characteristic C in FIG. Increasing direction A
And the direction B in which the input current i decreases, the direction B in which the input current i decreases
The output voltage V is larger than that in the increasing direction A by the hysteresis width δ. Here, assuming that there is no hysteresis between the input current i and the output voltage V and that there is no dependence on the increasing / decreasing direction, their relationship is represented by the characteristic shown in D. Therefore, in the increasing direction A, the voltage is output by δ / 2 smaller than the characteristic D, and in the decreasing direction B, the voltage is output by δ / 2 larger than the characteristic D. Will be done.

Therefore, when the alternating current is detected by using the Hall element sensor, in the section E where the signal level increases as shown in FIG. 5, only δ / 2 is output as compared with the input current i (true voltage value). In the section F in which the voltage V (detection voltage value) decreases and the signal level decreases, the output voltage V becomes δ / 2 higher than the input current i, and it is not possible to accurately detect the current. For this reason, the Hall element sensor cannot be used for accurate current detection, and thus it is unavoidable to use a sensor using a shunt resistor, ignoring the cost.

The present invention has been made in view of the above circumstances, and makes it possible to detect an AC signal with high accuracy even when a sensor having a hysteresis such as a Hall element sensor is used. It is an object of the present invention to provide a device that can perform control with high accuracy at a cost.

[0006]

Therefore, according to the present invention,
In a device that detects an AC signal by a sensor having hysteresis between an input signal and an output signal and performs predetermined control using the output signal of the sensor, the signal level of the input signal is increasing. An increase / decrease determination means for determining whether it is a section or a decreasing section, and if the increase / decrease determination section determines that it is an increase section, the input signal of the input signal is changed according to the hysteresis width of the sensor. When the signal level is increased and the increase / decrease determination unit determines that the interval is a decrease section, the signal level of the input signal is decreased according to the hysteresis width of the sensor to correct the input signal, and the correction is performed. Correction means for applying an input signal to the sensor.

[0007]

According to this structure, it is determined whether the signal level of the input signal, which is an AC signal, is increasing or decreasing. As a result, when it is determined that it is the increase section, the signal level of the input signal is increased according to the hysteresis width of the sensor. In addition, when it is determined that the interval is the decrease section, the signal level of the input signal is decreased according to the hysteresis width of the sensor. In this way, the level of the input signal is corrected so that the level of the output signal of the sensor corresponds to the level of the input signal (without hysteresis). Then, when the input signal thus corrected is applied to the sensor, the output signal does not have hysteresis (there is no difference in level between the increasing direction and the decreasing direction), and this is used. If the control is performed in this manner, the control is accurately performed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an AC signal detection error correction apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an AC servo motor driver of the embodiment.

The driver shown in the figure controls the current value of the AC servomotor so as to reach a target value. First, the speed command signal indicating the target value is added to the subtraction unit 1. Then, the speed command signal is applied to the current command generation circuit 2 via the subtraction unit 1. AC in the current command generation circuit 2
The current command signals iu ', iv', and iw 'corresponding to the u-phase, v-phase, and w-phase of the servomotor 12 are generated and added to the amplifiers 6, 7, and 8 via the subtracting units 3, 4, and 5, respectively. . The current command signals iu 'and iv' are amplified by the amplifiers 3 and 4,
The currents iu and iv are detected by the current detectors 9 and 10, respectively. The currents iu and iv thus detected are fed back to the subtraction units 3 and 4 as current feedback signals. The currents iu and iv are added to the adder 11, respectively. The adders 11 combine the currents iu and iv, and the combined current signal iw is added to the subtractor 5.

In the subtracting units 3, 4, and 5, the speed command signal iu
′, Iv ′, iw ′ and current feedback signals iu, i
Deviations from v and the combined current signal iw are respectively taken, and these are added to the amplifiers 6, 7 and 8, respectively. Amplifier 6,
The currents output from 7 and 8 are applied to the AC servomotor 12, respectively.

On the other hand, a rotor position detector 13 is attached to the rotor of the motor 12, and the rotor position detector 13 detects the position of the rotor. The signal indicating the rotor position detected by the rotor position detector 13 is applied to the current command generation circuit 2 and the differentiation circuit 14.

In the differentiating circuit 14, the position of the rotor is differentiated with respect to time, and the speed of the rotor is output. The speed of this rotor is fed back to the subtraction unit 1 as a speed feedback signal. The subtraction unit 1 takes a deviation between the input speed command signal and the speed feedback signal, and adds this deviation to the current command generation circuit 2. In the current command generating circuit 2, based on the input position of the rotor, it is an increasing section in which the level of the AC current applied to the motor 12 is increasing or a decrease in the level of the AC current is decreasing as described later. It is determined whether it is a section. Further, the current command generation circuit 2 corrects the current command signal corresponding to the inputted deviation to generate the corrected current command signals iu ', iv', iw '.

Hall element sensors are used as the current detectors 9 and 10. Therefore, these current detectors 9 and 10 are originally designed as shown in FIG.
As shown in (b), the output signal (detected value: shown by a solid line) with respect to the input signal (true value: shown by a broken line) of the detectors 9 and 10 is the same as that described in FIG. The shift amount is δ / 2 depending on the hysteresis width δ. Therefore,
The output signals iu and iv of the current detectors 9 and 10 contain an error. On the other hand, the combined current iw corresponding to the w phase is the u phase, v
Since the currents iu and iv respectively corresponding to the phases are generated by synthesis, similarly, the currents deviate from the true values as shown in FIG. Therefore, in the speed command generating circuit 2, if the current command signal corresponding to the deviation input from the subtraction unit 1 is output as it is, accurate current detection cannot be performed, and a current with such an error is detected. Even if the motor 12 is controlled in addition to the motor 12, a torque ripple is generated because the current is not accurate, and accurate control cannot be achieved at all.

Therefore, in the embodiment, the current command generating circuit 2
In, the current command current is corrected, and the corrected currents iu ', iv', and iw 'are output.

That is, as described above, the current detector 9,
The hysteresis characteristic C possessed by 10 is known in advance as described with reference to FIG. 4, and what level of voltage is applied to the current detectors 9 and 10 at what level of voltage. Whether it is output can be predicted. Therefore, the current command signal corresponding to the deviation added by the subtraction unit 1 is not output as it is, but the output iu of the current detectors 9 and 10 is changed.
, Iv are corrected so that the current command signal does not cause a deviation corresponding to the hysteresis.

FIG. 3 shows a correction current command signal (shown by a solid line) generated by the current command generation circuit 2.

That is, whether the section E in which the level of the alternating current is increasing or the section in which the alternating current level is decreasing is determined based on the rotor position signal applied from the rotor position detector 13. As a result, when it is determined to be in the alternating current increasing section E, the current command signal iu ′ corresponding to the u phase
Regarding the current command signal corresponding to the deviation (this is indicated by the broken line), the amount of decrease in δ / 2 is expected in consideration of the decrease in δ / 2.
The signal level is corrected so as to increase only by. on the other hand,
When it is determined that the AC signal decreasing section F is in the range δ /
In consideration of the increase of 2, the signal level is corrected so as to be smaller than the current command signal corresponding to the deviation by δ / 2 (see FIG. 3A).

Similarly, with respect to the current command signal iv 'corresponding to the v-phase, when it is determined that it is in the AC current increasing section E, a current command signal corresponding to the deviation (this is indicated by a broken line). The signal level is corrected so as to increase by δ / 2. On the other hand, when it is determined that it is the AC signal decrease section F, the signal level is corrected to be smaller than the current command signal corresponding to the deviation by δ / 2 (see FIG. 3B). . Since the current command signal iw 'corresponding to the w-phase is the combined signal iw' of the corrected current command signals iu 'and iv', the current command signal corresponding to the deviation (this is indicated by the broken line). ) Is not corrected.

When the corrected current command signals iu ', iv', iw 'are output from the current command generation circuit 2 as described above,
The detected currents iu and iv of the current detectors 9 and 10 are shown in FIG.
It becomes a true value (shown by a broken line) as shown in (a) and (b). In addition, the current iw related to the w phase also matches the true value. Therefore, an accurate current that does not shift due to hysteresis is applied to the motor 12, and current control can be performed accurately.

The correction of the command current signal in the current command generation circuit 2 is performed by the processing of the CPU.

[0022]

As described above, according to the present invention, an AC signal can be accurately detected even when a sensor having a hysteresis such as a Hall element sensor is used. Therefore, low cost is achieved, and control based on the detection result of the sensor is performed accurately.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of an AC current detection error correction device according to the present invention, and is a block diagram showing a configuration of an AC servo motor driver.

FIG. 2 is a waveform diagram showing waveforms of alternating currents of respective phases detected and synthesized by the current detector shown in FIG.

FIG. 3 is a waveform diagram showing waveforms of current command signals of respective phases corrected and output by the current command generating circuit shown in FIG.

FIG. 4 is a graph showing a hysteresis characteristic of a Hall element sensor.

5 is a waveform chart showing the waveforms of the input signal and the output signal of the sensor shown in FIG. 4 in comparison.

[Explanation of symbols]

 2 Current command generation circuit 12 AC servo motor 13 Rotor position detector

Claims (2)

[Claims] 1. An apparatus for detecting an AC signal by a sensor having hysteresis between an input signal and an output signal and performing a predetermined control using the output signal of the sensor, wherein the signal level of the input signal is An increase / decrease determination unit that determines whether it is an increasing section that is increasing or a decreasing section that is decreasing, and depending on the hysteresis width of the sensor when it is determined that the increasing section is an increasing section And the signal level of the input signal is increased by the increase / decrease determining means, the signal level of the input signal is decreased according to the hysteresis width of the sensor to correct the input signal. Then, a detection error correction device for an AC signal, which comprises a correction means for adding the corrected input signal to the sensor. 2. The AC signal according to claim 1, wherein the output signal of the sensor is applied to an AC motor, and the increase / decrease determination means detects the increase / decrease section based on the position of the rotor of the AC motor. Detection error correction device.