JPH05250003A - Digital controller - Google Patents

Abstract

PURPOSE:To solve the deterioration of controllability from truncating, rounding, etc., numerical value at the input part of a D/A converter, and to attain the digital controller with an excellent control characteristic. CONSTITUTION:This controller is provided with an A/D converter 12 to convert signals form a controlled system 11 from analog to digital, digital compensating means 13 to compensate the output from the A/D converter 12 by digital signal processing, precision limiting means 14 to limit the effective precision of the output signals from the digital compensating means, D/A converter 15 to convert the output signals from the precision limiting means from digital to analog, and quantization error feed back means 16 with transfer function being F to feed back the quantization error generated by the precision limiting means to the input of the precision limiting means. Further, by turning the transfer characteristic of (1+F) into low-pass filter characteristic, the influence of quantization error is reduced at the low frequency which participates largely in the control characteristic, and the sufficient control characteristic can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital controller for controlling various controlled objects such as actuators and motors to a target state.

[0002]

2. Description of the Related Art Recently, in order to control various control objects such as actuators and motors to a target state, a digital control device for compensating by digital signal processing has been used. A conventional digital control device generally has a configuration as shown in FIG. The configuration will be described below with reference to FIG.

In FIG. 3, 31 is an object to be controlled such as an actuator and a motor, 32 is an A / D converter, 33 is a digital compensator, and 34 is a D / A converter. First, the analog signal from the controlled object 31 is converted into a digital signal by the A / D converter 32. Then A / D converter 3
The output signal 2 is compensated by digital signal processing in the digital compensator 33 so that the controlled object 31 is in the target state, converted into an analog signal by the D / A converter 34, and input to the controlled object. By repeating the above operation, the controlled object 31 is controlled to the target state.

[0004]

However, in the conventional digital control device shown in FIG. 3, when the resolution of the D / A converter 34 is lower than the output signal accuracy of the digital compensator 33, the D / A converter 34 is used. Quantization error ε occurs because the effective precision is limited due to the truncation of numerical values, rounding by rounding, etc. at the input part of. This quantization error adversely affects the state of the controlled object, causing problems such as unnecessary vibration of the controlled object 31, an increase in steady-state deviation or residual error, and deterioration of stability, so that sufficient control characteristics can be obtained. There was a problem that was difficult.

[0005]

In order to solve the above-mentioned problems, a digital control apparatus of the present invention comprises an A / D converter for analog-digital converting a signal obtained from a controlled object, and an output of the A / D converter. Compensating means for compensating the signal by digital signal processing, precision limiting means for limiting the effective precision of the output signal of the digital compensating means, and D / A for converting the output signal of the precision limiting means into digital / analog.
The configuration has a converter and a quantization error feedback means for feeding back a quantization error generated by the accuracy limiting means to the input of the accuracy limiting means. Here, when the transfer function of the quantization error feedback means is F, it is optimal to determine the characteristic of the transfer function F so that the transfer characteristic of (1 + F) becomes the low-range reactor wave characteristic that cuts the low-frequency. It is possible to realize various control characteristics.

Alternatively, an A / D converter for analog / digital converting a signal obtained from a controlled object, a digital processing means for performing digital signal processing such as storing or computing the output of the A / D converter, and a digital processing means. Filter that receives the output signal of the digital filter, an accuracy limiting unit that limits the effective accuracy of the output signal of the digital filter, a D / A converter that converts the output signal of the accuracy limiting unit to analog, and an output of the accuracy limiting unit. And a feedback means for returning the signal to the input of the digital filter. Here, when the transfer function of the feedback means is G and the transfer function of the digital filter is H, the transfer function G of the feedback means is set so that the transfer characteristic of (1 / (1-GH)) becomes the low-range reactor wave characteristic. Optimum control characteristics can be realized by determining the characteristics.

[0007]

The digital control device of the present invention is provided with the quantizing error feedback means whose transfer function is F for feeding back the quantizing error generated by the accuracy limiting means to the input of the accuracy limiting means, or the output of the digital compensating means. Since the digital filter having a signal-input transfer function as H and the feedback means as the transfer function G for returning the output signal of the precision limiting means to the input of the digital filter are provided, the precision limiting means cuts off the numerical value. , Or the transfer function of the quantization error caused by rounding to the input of the D / A converter becomes (1 + F) or (1 / (1-GH)), and this is the low-range reactor wave characteristic, so the control characteristic is large. Quantization error in the low range involved is reduced, and problems such as unnecessary vibration of the controlled object, steady-state deviation or increase of residual error, and deterioration of stability are suppressed. Can be can be, obtain sufficient control characteristics.

[0008]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a digital controller which is an embodiment of the present invention. In FIG. 1, 11 is a control target such as a focus actuator for controlling the position of a laser on an optical disk, a tracking actuator, and a motor for rotating the optical disk, and 12 is an electrical detection of an error resulting from the operation of each control target. A / D converter for converting the output of the photodetector or the rotation detector into a digital signal, 13 is a digital compensator, 15 is a D / A converter, and 14 is an output signal of the digital compensator 13. Alternatively, it is a precision limiting means that limits the precision according to the resolution of the D / A converter 15 by truncation or the like. Numeral 16 is a quantization error feedback means in which the transfer function for feeding back the quantization error generated by the accuracy limiting means 14 to the input of the accuracy limiting means 14 is F. Here, the transfer function F is only the storage means,
Although a good result can be obtained with a digital filter combining the storage means and the arithmetic means, the transfer function determines F so that the transfer characteristic of (1 + F) has a low-range reactor wave characteristic that cuts the frequency of the low-frequency component. By doing so, optimum control characteristics are realized.

The operation of the present invention having the above configuration will be described with reference to FIG. First, the analog signal from the controlled object 11 is A
It is converted into a digital signal by the / D converter 12. Then, the output signal of the A / D converter 12 is compensated by the digital signal processing in the digital compensator 13 so that the controlled object 11 becomes the target state.

The output signal of the digital compensator 13 is precision-limited by the precision limiting means 14 to the precision according to the resolution of the D / A converter 15, such as rounding or truncation of the numerical value, and then D
The signal is converted into an analog signal by the / A converter 15 and input to the controlled object.

At this time, the quantization error ε generated by the accuracy limiting means 14 is fed back to the input of the accuracy limiting means 14 by the quantization error feedback means 16. A / D here
The input signal of the converter 12 is X, the output of the D / A converter 14 is Y, the transfer function of the A / D converter 12 is TAD, the transfer function of the digital compensator 13 is TDC, and the transfer of the D / A converter 14 is When the function is TDA, the output Y of the D / A converter 14 is

[0013]

[Equation 1]

[0014] Here, by setting the transfer characteristic of (1 + F) to the low-range reactor wave characteristic having a sufficient attenuation characteristic in the band of the controlled object, the influence of the quantization error ε on the output Y of the D / A converter 15 is This is alleviated in the low frequency range, which greatly affects the control characteristics. When such a feedback loop is not provided, the quantization error ε is directly output, which has a great influence as a factor of increasing the residual error, but the simple configuration of providing a feedback loop as in this example It is possible to obtain highly accurate control performance without increasing the resolution of the D / A converter. This is because the digital processing step in the case of performing digital processing is generally performed extremely faster than the band frequency to be controlled, so that the cycle of generating the quantization error ε is
The focus is on the fact that the residual error period is 10 to 100 times shorter than the residual error period that occurs when the quantization error is integrated, and the quantization error that occurred in a certain processing step is By observing within the band frequency of the controlled object by returning to the loop,
As the input signal to the controlled object, it is possible to obtain a signal having almost no difference from the case where a D / A converter that does not generate a quantization error is used.

Further, as described above, the transfer function F of the quantization error feedback means is determined by determining the transfer function F so that the transfer characteristic of (1 + F) has the low-range reactor wave characteristic. Since it is possible to limit the term having the term out of the control band, it is possible to realize the optimum control characteristics, which causes problems such as unnecessary vibration of the controlled object, steady deviation or increase of residual error, and deterioration of stability. It is possible to suppress the above and obtain sufficient control characteristics. Where the transfer function F
The actual characteristic of the has a low-pass characteristic, and the quantization error ε that affects the band frequency of the controlled object is sufficiently suppressed by feeding back, and the quantization error ε outside the band frequency of the controlled object is It means leaving it alone.

Further, the quantization error ε may be rounded data itself, or may be data that has been subjected to processing such as integration, accumulation and averaging of values during a specific period. In this example, the control loop by feedback has been described. However, in order to reduce the quantization error in the digital processing of audio and video, which is an open-loop processing circuit that only digitally processes the input signal and outputs it. But it is obvious that it is effective.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of a digital controller which is a second embodiment of the present invention. In FIG. 2, reference numeral 21 is a control object such as a focus actuator for controlling the position of the laser on the optical disk, a tracking actuator, or a motor for rotating the optical disk, and 22 is an electrical detection of an error resulting from the operation of each control object. A / which converts the output of the photodetector or rotation detector into a digital signal
A D converter, a digital compensator 23 as a digital processing circuit, a digital filter 24 having a transfer function of H, and a D / A converter 26. Reference numeral 25 is precision limiting means for limiting the precision of the output signal of the digital filter 24 according to the resolution of the D / A converter 26 by rounding or truncating the numerical value. Further, 27 is a quantization error feedback means for returning the output signal of the accuracy limiting means 25 to the input of the digital filter 24, and the quantization error feedback means is (1 / (1
-GH)) has a low frequency wave characteristic.

First, the analog signal from the controlled object 21 is A
It is converted into a digital signal by the / D converter 22. Subsequently, the output signal of the A / D converter 22 is compensated by digital signal processing in the digital compensator 23 so that the controlled object 21 is in the target state, and is input to the digital filter 24 whose transfer function is H. Digital filter 24
The output of is limited by the precision limiting means 25 to a precision according to the resolution of the D / A converter 26, such as rounding or truncation, and then converted into an analog signal by the D / A converter 26 and input to the controlled object. To be done.

In this configuration, the input signal of the D / A converter 26 to which the quantization error ε is added by the accuracy limiting means 25 is fed back to the input of the digital filter 24 by the quantization error feedback stage 27. Here, the input signal of the A / D converter 22 is X, the output of the D / A converter 26 is Y, the transfer function of the A / D converter 22 is TAD, and the transfer function of the digital compensator 23 is TAD.
If the transfer function of the DC / D / A converter 26 is TDA, then D / A
The output Y of the converter 26 is

[0021]

[Equation 2]

It becomes Here, for the same reason as in the case of the first embodiment, the transfer characteristic of (1 / (1-GH)) is the low-range reactor wave characteristic, and therefore the quantization error ε is given to the output Y of the D / A converter 26. The effect is reduced in the low range, which is greatly related to the control characteristics. When such a feedback loop is not provided, the quantization error ε is directly output, which has a great influence as a factor of increasing the residual error. The quantization error ε generated in the control band is fed back at a higher rate than that of the control target band to suppress the cumulative error of the quantization error in the control band, thereby increasing the resolution without increasing the resolution of the D / A converter. Accurate control performance can be obtained, problems such as generation of unnecessary vibration of the controlled object, increase in steady-state deviation or residual error, deterioration of stability, etc. can be suppressed, and sufficient control characteristics can be obtained.

As is apparent from the above embodiments, according to the present invention, D /
Even when the resolution of the A converter is low, there is provided a quantization error feedback means whose transfer function is F for feeding back the quantization error generated by the accuracy limiting means to the input of the accuracy limiting means, or the output of the digital compensating means. Since a digital filter having a transfer function of H as a signal and a feedback means of a transfer function G for returning the output signal of the precision limiting means to the input of the digital filter are provided, the precision limiting means cuts off a numerical value. , Or the transfer function of the quantization error caused by rounding to the input of the D / A converter becomes (1 + F) or (1 / (1-GH)), and this is the low-range reactor wave characteristic, so the control characteristic is large. Quantization error in the low range involved is reduced, and problems such as unnecessary vibration of the controlled object, steady-state deviation or increase of residual error, and deterioration of stability are suppressed. It can be one in which it is possible to obtain sufficient control characteristics.

The digital compensator is generally composed of a storage means and a calculation means, but it may be composed of only the storage means or only the calculation means. Also D
There is no limitation on the configuration method of the / A converter, and for example, a pulse width modulation type D / A converter may be used.

In the embodiment, the actuator and the motor of the optical disk device are used as the control object, but
The present invention is not limited to this device and can be applied to any device having a similar control system, and not only the feedback control system as in the present embodiment, but also voice and image processing,
It is obvious that it is possible to reduce the influence of quantization error in digital signal processing that does not have a feedback system.

[0026]

As described above, according to the present invention, even when the resolution of the D / A converter is low with respect to the accuracy of the output signal of the digital compensator, the quantization error caused by the accuracy limiting means is limited to the accuracy limiting means. It is extremely simple to provide the quantization error feedback means for feeding back to the input of the digital filter, or to provide the digital filter which inputs the output signal of the digital compensating means and the feedback means which feeds back the output signal of the accuracy limiting means to the input of the digital filter. With such a configuration, it becomes possible to realize extremely accurate control even in a digital controller using a D / A converter having a low resolution.

Further, (1 + F) or (1 /
By setting the characteristic of the transfer function expressed by (1-GH)) as the low-range reactor wave characteristic, the optimum control characteristic can be realized, and the quantization error in the low range that largely contributes to the control characteristic can be reduced. Problems such as generation of unnecessary vibration of the controlled object, increase of steady-state deviation or residual error, deterioration of stability, etc. can be suppressed, and highly accurate control characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a conventional digital controller.

[Explanation of symbols]

 11 Control Target 12 A / D Converter 13 Digital Compensator 14 Precision Limiting Means 15 D / A Converter 16 Quantization Error Feedback Means 21 Controlled Target 22 A / D Converter 23 Digital Compensator 24 Digital Filter 25 Precision Limiting Means 26 D / A converter 27 Quantization error feedback means 31 Control object 32 A / D converter 33 Digital compensator 34 D / A converter

Claims (5)

[Claims] 1. An A / D converter for analog / digital converting a signal obtained from a controlled object, a digital compensating means for compensating the output of the A / D converter by digital signal processing, and an output of the digital compensating means. A precision limiting unit that limits the effective precision of a signal, a D / A converter that performs digital-analog conversion on the output of the precision limiting unit, and a quantum that feeds back a quantization error generated by the precision limiting unit to the input of the precision limiting unit. And a digitalized error feedback means. 2. The digital controller according to claim 1, wherein the transfer characteristic when the transfer function of the quantization error feedback means is F (1 + F) is a low-range reactor wave characteristic. 3. An A / D converter for analog / digital converting a signal obtained from a controlled object, a digital processing means for digitally processing the output of the A / D converter, and an output signal of the digital processing means. , A digital filter that inputs, a precision limiting unit that limits the effective precision of the output signal of the digital filter, a D / A converter that digital-analog converts the output signal of the precision limiting unit, and the output of the precision limiting unit. A digital control device comprising a feedback means for returning a signal to the input of the digital filter. 4. When the transfer function of the feedback means is G and the transfer function of the digital filter is H, (1 / (1-
4. The digital control device according to claim 3, wherein the transfer characteristics of GH)) are low-range reactor wave characteristics. 5. A focus control for focusing the laser light in an optical disk device for recording or reproducing at least information by irradiating the recording medium with the laser light,
Alternatively, at least one of a tracking control for causing the laser light to follow a target track on the recording medium or a transfer control for transferring an optical head equipped with the focus control actuator and the tracking control actuator is performed. The digital control device according to any one of claims 1 to 4.