JPH05333934A - Digital controller for feedback servo system and its phase compensating method - Google Patents

Abstract

PURPOSE:To offset the phase delay due to the waste time by using such a phase compensating means that applies the zero-degree holding invariable conversion to the transmission function set so as to obtain the relative order larger than 1 and acquires the transmission function of the discrete time for the phase compensation means. CONSTITUTION:The position error signal produced by a position error detecting means 2 which detects the position error of a transfer means 1 against the target position, is sampled by a sampling means 3 in a prescribed sampling timing cycle. This sampled signal is converted into a digital signal by an A/D converting means and undergoes the phase compensation through a phase compensating means 17. Then, the compensate digital signal is converted again into an analog signal by a D/A converting means 6. This analog signal is inputted to a drive means 7 and moves the means 1 up to its target position. The means 17 compensates the phase of the output of the means 6 with use of the transmission function of the discrete time which is obtained by applying the zero-degree holding invariable conversion to the transmission function of the contunuous time whose degree is set larger than 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedback servo system digital controller used for focus control of an optical disk device and a phase compensation method thereof.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram showing a conventional digital controller for a feedback servo system disclosed in Japanese Patent Laid-Open No. 2-234205. In the figure, 1
Is a transfer means such as an optical head to be controlled, and 2 is a position deviation detection means for detecting a position deviation of the transfer means 1 from a target position and generating a position deviation signal. Reference numeral 3 is a sampling means for sampling the positional deviation signal from the positional deviation detection means 2, and 4 is an analog / digital conversion means (hereinafter A / D) for converting the signal sampled by the sampling means 3 into a digital signal. D conversion means).

Reference numeral 5 is a phase compensating means for compensating the phase delay amount of the servo system. Reference numeral 6 is a digital-analog conversion means (hereinafter referred to as D / A conversion means) for converting the digital signal phase-compensated by the phase compensation means 5 into an analog signal, and 7 is an output of the D / A conversion means 6. It is a drive means for receiving and driving the transfer means 1. Reference numeral 8 is a sampling timing generation means for generating timing signals of the sampling means 3 and the D / A conversion means 6, and 9 is a target position setting means for setting the target position of the transfer means 1 in the phase shift detection means 2. is there.

Numeral 10 is a predicting means for predicting the data at the next time point based on the current and past positional deviation data, and numeral 11 is a limiter for limiting the absolute value of the predicted value output by the predicting means 10. .. Reference numeral 12 is a band synthesizing means for synthesizing the signal generated by the limiter 11 and the signal output from the A / D converting means 4 by dividing them into frequency bands and inputting them to the phase compensating means 5. Reference numeral 13 is a digital signal processing section which is composed of the predicting means 10, the limiter 11, the band synthesizing means 12, and the phase compensating means 5.

FIG. 10 is a functional block diagram of the band synthesizing means 12, in which 14 is a high-pass filter to which the current positional deviation data I _n from the A / D converting means 4 is input, and 15 Is a low-pass filter to which the limiter output I (l) _{n + 1} from the limiter 11 is input.
Reference numeral 16 is an adder for combining the outputs of the high-pass filter 14 and the low-pass filter 15. In addition,
FIG. 11 shows the frequency characteristics (H
6 is an explanatory diagram showing frequency characteristics (LPF (z ⁻¹ )) of PF (z ⁻¹ ) and the low pass filter 15. FIG.

Next, the operation will be described. The positional deviation signal generated by the positional deviation detection means 2 which detects that the position of the transfer means 1 has deviated from the target position is sampled by the sampling means 3 and sent to the A / D conversion means 4. Here, when the signal input from the digital signal processing unit 13 is directly input to the phase compensating means 5 which performs phase compensation by bilinear transformation, as shown in the time chart of FIG.
The signal I _n output from the sampling means 3 at Δt (where n is a natural number and Δt is a sampling timing period) is A / D.
After being converted into a digital signal by the converting means 4, the control amount is calculated by the phase compensating means 5 of the digital signal processing section 13, and further converted into an analog signal by the D / A converting means 6,
At time (n + 1) Δt, it is output to the driving means 7 as a signal O _n .

Therefore, in such a feedback servo system digital controller, a phase delay due to a sample hold at the time of sampling and a phase delay due to a dead time caused by the control signal being delayed by one sampling time are output. In order to realize a servo system having a wide band of several kHz due to both of the above effects, the phase compensating means 5 requires an excessive amount of phase advance. As a result, the gain rises above the gain crossover frequency, the servo system oscillates due to the mechanical resonance of the transfer system, or the gain margin of the servo loop decreases due to the deterioration of the open loop transfer characteristic near the gain crossover frequency. Therefore, it is difficult to realize a wide band servo system.

Therefore, in the feedback servo system digital controller shown in FIG. 9, the data at the next time predicted by the prediction means 10 and limited by the limiter 11 and the output of the A / D conversion means 4 are shown. Are combined by the band combining means 12 and then input to the phase compensating means 5. That is, the prediction unit 10 and the position error data I _n at the current (time n.DELTA.t), past (time (n-1) Δt and time (n-2) Δt) positional deviation of the data I _n-1 and I _n-2
The predicted value I (p) _{n + 1} is calculated based on Here, this predicted value I (p) _{n + 1} is calculated using the following extrapolation formula, assuming that the transfer system moves at constant acceleration for several cycles.

I (p) _{n + 1} = 3I _n -3I _n-1 + I _n-2 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (1)

The limiter 11 compares the predicted value I (p) _{n + 1} predicted by the predicting means 10 with the current positional deviation data I _n from the A / D converting means 4 and calculates the absolute value of the data. The band synthesizing means 12 uses the smaller value as the limiter output I (l) _{n + 1.}
Send to. The band synthesizing means 12 sends the current positional deviation data I _n from the A / D converting means 4 to the high pass filter 14 to attenuate the low frequency component, and also the limiter output I (l) _{n + 1} from the limiter 11. It is sent to the low-pass filter 15 to attenuate the high frequency components, and the adder 16 combines them into a combined output I (c) _{n + 1} shown below.

I (c) _{n + 1} = HPF (z ⁻¹ ) · I _n + LPF (z ⁻¹ ) · I (l) _{n + 1} ‥‥‥‥ (2)

As described above, in the digital signal processing unit 13, first, the predicting unit 10 predicts the amount of positional deviation, and then the limiter 11 limits the high frequency gain to advance the phase, and the band synthesizing unit 12 further. After performing band combination of the predicted value and the current value to improve S / N, the phase compensation means 5 performs phase compensation to obtain a control output with improved gain margin.

FIG. 13 is a time chart showing the operation timing at that time. Signal I _n from the A / D converter 4 at time n.DELTA.t, I _n-1, I _n-2 on the basis of making predictions value I (p) _{n + 1} predictive, the prediction value I (p) _{n + The} control output O _{n + 1} is calculated from ₁ and is calculated at time (n + 1) Δt by D
Input to the / A conversion means 6. The D / A conversion means 6 converts this control output O _{n + 1} into an analog signal and sends it to the drive means 7, and the drive means 7 moves the transfer means 1 to the target position according to the signal. As a result, a control output with no phase delay can be obtained, and a broadband servo system can be realized.

[0014]

Since the conventional digital controller of the feedback servo system is constructed as described above, not only the predicting means 10 and the band synthesizing means 12 which are complicated in construction are required, Band synthesis means 12
High-pass filter 14 and low-pass filter 15 in
It is complicated to determine the time constant of, and as a result, the gain is increased above the gain crossover frequency, the oscillation of the servo system due to the device resonance of the transfer system becomes a problem, and the nonlinear phase compensation is performed. There was a problem that it was difficult to secure the stability of the servo system.

The inventions set forth in claims 1 and 2 have been made to solve the above problems, and are stable even if the phase advance amount in the phase compensating means is appropriately suppressed. It is an object of the present invention to obtain a digital controller for a feedback servo system that can be controlled in a stable manner and a phase compensation method thereof.

The inventions described in claims 3 and 4 are
An object of the present invention is to obtain a digital controller for a feedback servo system and a phase compensation method for the same, which can prevent a gain increase above a gain crossover frequency, suppress mechanical vibration of a transfer system, and perform stable control.

[0017]

According to a first aspect of the present invention, there is provided a feedback servo system digital control device comprising:
As a phase compensating means for compensating the phase of the output of the A / D converting means, a continuous time transfer function set so that the relative order thereof, that is, the difference between the order of the denominator polynomial and the order of the numerator polynomial is larger than 1. Is used to obtain a discrete-time transfer function when performing phase compensation by performing a zero-order hold-invariant transformation.

According to a second aspect of the present invention, there is provided a phase compensation method for a digital controller for a feedback servo system, wherein a continuous-time transfer function set so that its relative order is larger than 1 is used for sampling timing. Using the discrete-time transfer function obtained by the zero-order hold invariant conversion with the period of, one sampling is performed from the input of the current and past A / D conversion means and the output of the current and past D / A conversion means. The phase of the output of the D / A conversion means in the cycle future is compensated.

According to the third aspect of the present invention, the feedback servo system digital control device has a relative order greater than 1 as the phase compensating means for compensating the phase of the output of the A / D converting means. The set continuous-time transfer function is bi-linearly converted by using a sampling frequency which is about twice the peak frequency of the mechanical vibration in the high-frequency region of the control target, and the discrete-time transfer function for phase compensation. Is used.

According to a fourth aspect of the present invention, there is provided a phase compensation method for a digital controller for a feedback servo system, wherein a continuous-time transfer function set so that its relative order is larger than 1 is used as a controlled object. Using a discrete-time transfer function obtained by performing a bilinear transformation with a frequency about twice the peak frequency of mechanical vibration in the high-frequency region as the sampling frequency, the current and past inputs of the A / D conversion means and the present And the phase compensation of the output of the D / A conversion means in the future is performed by one sampling period from the output of the past D / A conversion means.

[0021]

The phase compensating means in the invention described in claim 1 is obtained by setting the continuous-time transfer function in phase compensation so that its relative order is larger than 1, and performing zero-order hold invariant transformation on it. Using the discrete-time transfer function, the phase of the output of the D / A conversion means of one sampling period from the input of the current and past A / D conversion means and the output of the current and past D / A conversion means By performing the compensation, a feedback servo system digital controller capable of canceling the phase delay due to the control output being delayed by one sampling time is realized without using a complicated predicting means or band synthesizing means.

In the phase compensating method according to the second aspect of the invention, the continuous-time transfer function in the phase compensation is set so that its relative order is larger than 1, and it is set to the zero-order in the cycle of sampling timing. Hold-invariant conversion is performed to obtain a discrete-time transfer function, and the obtained discrete-time transfer function is used based on the current and past A / D conversion means inputs and the current and past D / A conversion means outputs. One sampling cycle to compensate the phase of the output of the D / A conversion means in the future.

Further, the phase compensating means in the invention according to claim 3 sets the transfer function of the continuous time in the phase compensation so that the relative order thereof is larger than 1, and sets it to the mechanical vibration in the high frequency region of the controlled object. A digital controller for a feedback servo system capable of suppressing mechanical resonance in the high frequency region of the transfer system and increasing the gain margin of the servo system by performing bilinear conversion with a frequency approximately twice as high as the peak frequency of To achieve.

In the phase compensating method according to the invention as defined in claim 4, the transfer function of the continuous time in the phase compensation is set so that its relative order is larger than 1, and the mechanical function is controlled in the high frequency region of the controlled object. Of the peak frequency of 2 is sampled and bilinearly transformed to obtain a discrete-time transfer function, and the input of the present and past A / D conversion means and the output of the present and past D / A conversion means Based on the above, the phase of the output of the D / A conversion means in the future of one sampling period is compensated using the obtained discrete time transfer function.

[0025]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the invention described in claims 1 and 2. In the figure, 1 is a transfer means as a controlled object, 2 is a displacement detection means, 3 is a sampling means, 4 is an A / D conversion means, 6 is a D / A conversion means, 7 is a drive means, and 8 is a sampling means. The timing generation means 9 is a target position setting means, and since it is the same part as those of the prior art which are assigned the same reference numerals in FIG. 9, detailed description thereof will be omitted.

Reference numeral 17 designates a phase compensating means corresponding to the one designated by reference numeral 5 in FIG.
Set the relative order, which is the difference between the order of the denominator polynomial and the order of the numerator polynomial, to be greater than 1, and obtain the discrete-time transfer function when performing phase compensation by performing the zero-order hold invariant transformation. They are different. The transfer function of the continuous time is shown below.

[0027]

[Equation 1]

The obtained discrete-time transfer function is shown below.

[0029]

[Equation 2]

Next, the operation will be described. When the position of the transfer means 1 is deviated from the target position, the positional deviation signal generated by the positional deviation detecting means 2 which detects it is detected by the sampling means 3
Are sampled at a predetermined sampling timing period.
The sampled signal is converted into a digital signal by the A / D conversion means 4 and phase-compensated by the phase compensation means 17,
The D / A conversion means 6 converts the analog signal again. D
The signal analog-converted by the A / A converter 6 is driven by the driver 7.
Is input to move the transfer means 1 until it coincides with the target position.

FIG. 2 is a time chart showing the operation timing during this period. In FIG. 2, I _n is time n
The output of the sampling unit 3 at Δt is shown, and O _n is the output of the D / A conversion unit 6 at time nΔt. The signal I _n output from the sampling unit 3 at time nΔt is subjected to A / D conversion, phase compensation, and D / A conversion, and then at time (n + 1) Δt from the D / A conversion unit 6. Is output.

Further, FIG. 3 shows the phase characteristic of the conventional phase compensating means 5 which performs bilinear conversion of the continuous-time transfer function represented by the equation (3) and the zero-order when the transfer function is set as follows. Phase compensation means 17 of this embodiment for performing hold-invariant conversion
FIG. 3 is an explanatory diagram showing a comparison with the phase characteristics of FIG.

[0033]

[Equation 3]

In this case, the sampling timing period Δt is set to 20 μs (= 50 kHz), in the figure, (a) shows the phase characteristic of the conventional phase compensating means 5, and (b) shows the phase compensating means of this embodiment. 17 shows the phase characteristics of No. 17. As shown in FIG. 3, the conventional phase compensator 5 has a frequency of 1.3.
What only got a phase advance of 67 ° at kHz,
In the phase compensating means 17 of this embodiment, the frequency is 1.6 kHz.
It can be seen that a phase lead of 71 ° is obtained at z.

Here, a discrete-time transfer function obtained by bilinearly transforming the continuous-time transfer function shown in the equation (5),
D / A conversion means 6 when the conventional phase compensation means 5 is used
The output O _{n + 1} calculation formula and the respective coefficients thereof are shown below.

[0036]

[Equation 4]

Further, the D / A conversion means in the case of using the phase compensation means 17 of this embodiment by the discrete-time transfer function obtained by performing the zero-order hold invariant conversion of the continuous-time transfer function shown in the equation (5). The arithmetic expression of the output O _{n + 1} of 6 and each coefficient thereof are shown below.

[0038]

[Equation 5]

As described above, according to this embodiment, the output signal O _{n + 1} of one sampling time future is output without using the prediction signal I (p) _{n + 1} which is conventionally required. The signal O _n and the previous output signals O _n-1 , O _n-2 , ..., And the current input signal I _n and the previous input signals I _n-1 , I _n-2 , ...
It is possible to calculate from, and it is possible to cancel the phase delay due to the dead time of outputting the control output with a delay of one sampling time without using the predicting means and the band synthesizing means.

Example 2. Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing an embodiment of the invention described in claims 3 and 4, and the same parts as in FIG. In the figure, 18 is a discrete-time transfer when performing phase compensation by bilinearly transforming a continuous-time transfer function with a sampling frequency that is about twice the peak frequency of mechanical vibration in the high-frequency region of the control target. This is a phase compensating means different from that denoted by reference numeral 17 in FIG. 1 in that a function is obtained. The converted discrete time transfer function is shown below. The factor of the numerator polynomial of this transfer function includes (1 + z ^-1 ).

[0041]

[Equation 6]

Next, the operation will be described. Again,
Similar to the case of the first embodiment, the displacement of the transfer means 1 from the target position is detected by the displacement detection means 2, the displacement signal is sampled by the sampling means 3 and sent to the A / D conversion means 4. , A phase compensating means 1 for the signal converted into a digital signal
After phase compensation at 8, the D / A conversion means 6 converts the analog signal again and sends it to the driving means 7 to move the transfer means 1 until it coincides with the target position.

FIG. 5 is an explanatory view showing the frequency characteristic of the gain of the phase compensating means, and FIG. 5 (A) is 1.4 kHz.
A phase advance element C1 (s) whose quadratic numerator polynomial and denominator polynomial shown below that give a phase lead of about 60 ° in z and whose denominator polynomial is third (relative order is 1) is set to a sampling timing period Δt of 20.
μs (= 50 kHz) was realized by bilinear conversion,
The frequency characteristic of the gain of the phase compensation means 18 of this embodiment is shown.

[0044]

[Equation 7]

On the other hand, FIG. 5B shows about 60 at 1.4 kHz.
Both the numerator polynomial and the denominator polynomial shown below that give a phase advance of ° are quadratic (relative order 0) phase advance element C2.
(s), the sampling timing period Δt is set to 20 μs (= 50
The frequency characteristic of the gain of the phase compensating means realized by the bilinear conversion is shown for comparison.

[0046]

[Equation 8]

As described above, the gain of the phase compensating means 18 in the second embodiment is 25 kHz, which is half the sampling timing frequency (50 kHz), as shown in FIG. Shows.

FIG. 6 is an explanatory diagram showing the frequency characteristics of gain and phase from the drive current of the focus actuator to the lens displacement when the second embodiment is applied to the focus actuator of the optical disk device. In this case, a gain peak due to mechanical resonance of the transfer system is seen around 25 kHz.

FIG. 7 shows an open loop transfer characteristic when a feedback system is constituted by the focus actuator having the frequency characteristic shown in FIG. 6 and the phase compensating means 18 having the frequency characteristic shown in FIG. 8 is an explanatory diagram and FIG.
FIG. 7 is an explanatory diagram showing an open loop transfer characteristic when a feedback system is constituted by the focus actuator having the frequency characteristic shown in FIG. 6 and the phase compensating means having the frequency characteristic shown in FIG. 5B. In the open loop transfer characteristic shown in FIG. 8, the gain peak due to the mechanical resonance of the transfer system around 25 kHz remains as it is, but in the open loop transfer characteristic shown in FIG. 7, the gain near the 25 kHz due to the mechanical resonance of the transfer system remains. The peak is suppressed, and the gain margin of the servo system is greatly improved as compared with that shown in FIG.

[0050]

As described above, according to the invention described in claim 1, the phase compensating means for compensating the phase of the output of the A / D converting means is set so that its relative order is larger than one. Since the continuous-time transfer function is subjected to the zero-order hold invariant conversion to obtain the discrete-time transfer function at the time of phase compensation, it is wasteful that the control output is delayed by one sampling time. It is possible to cancel the phase delay due to time without using a complicated predicting means or band synthesizing means, and it is possible to obtain a feedback servo system digital controller capable of realizing a simple and stable wideband servo system at a low cost. is there.

According to the second aspect of the present invention, the continuous-time transfer function set so that its relative order is larger than 1 is subjected to zero-order hold invariant conversion, and the obtained discrete-time transfer function is obtained. By using the present and past inputs of the A / D conversion means and the outputs of the present and past D / A conversion means, phase compensation of the output of the D / A conversion means of one sampling period in the future is performed. Therefore, the phase delay due to the dead time that the control output is output with a delay of one sampling time can be canceled without using a complicated predicting means or band synthesizing means.
There is an effect that a simple and stable servo system can be realized at low cost.

According to the invention described in claim 3, A
In the phase compensation means for compensating the phase of the output of the / D conversion means,
The continuous-time transfer function whose relative order is set to be larger than 1 is subjected to bilinear conversion with a frequency about twice the peak frequency of mechanical vibration in the high-frequency region of the control object as the sampling frequency, and phase compensation is performed. Since it is configured to use the one that obtains the discrete-time transfer function at the time, even if the phase compensating means is required to have an excessive amount of phase lead, and causes a gain increase above the gain crossover frequency, Vibrations due to mechanical resonance of the transfer system are reliably suppressed, the gain margin of the servo system is improved, and there is an effect that a feedback servo system digital controller that can easily and inexpensively realize a stable broadband servo system is obtained. ..

Further, according to the invention described in claim 4, the number of transmissions of the continuous time set so that the relative order is larger than 1 is about twice the peak frequency of the machine signal in the high frequency region of the controlled object. Bi-linear transformation using the frequency of as the sampling frequency, and using the obtained discrete-time transfer function,
Since the phase compensation of the output of the D / A converting means in the future of one sampling period is performed based on the inputs of the current and past A / D converting means and the outputs of the current and past D / A converting means, An excessive amount of phase lead is required for the phase compensation means,
Even if the gain rises above the gain crossover frequency, vibration due to mechanical resonance of the transfer system is reliably suppressed, the gain margin of the servo system is improved, and a stable wideband servo is simple and inexpensive. It has the effect of realizing a system.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a time chart showing the operation timing of the above embodiment.

FIG. 3 is an explanatory diagram showing a comparison of the phase characteristics of the phase compensating means of the above-described embodiment and the conventional phase compensating means.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing the frequency characteristics of the gain of the phase compensating means of the embodiment and other phase compensating means in comparison.

FIG. 6 is an explanatory diagram showing the frequency characteristics of gain and phase from the drive current of the focus actuator to the lens displacement when the above embodiment is applied to the focus actuator of the optical disc device.

FIG. 7 is an explanatory diagram showing an open loop transfer characteristic in the case where a feedback system is constituted by the focus actuator and the phase compensating means of the above embodiment.

FIG. 8 is an explanatory diagram showing an open loop transfer characteristic when a feedback system is configured by the focus actuator and the other phase compensation means.

FIG. 9 is a block diagram showing a conventional digital controller of a feedback servo system.

FIG. 10 is a block diagram showing the configuration of the band synthesizing means.

FIG. 11 is an explanatory diagram showing a frequency characteristic of a gain of the band synthesizing means.

FIG. 12 is a time chart showing the operation timing of a conventional digital controller of a feedback servo system.

FIG. 13 is a time chart showing operation timing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transfer means (controlled object) 2 Position shift detection means 3 Sampling means 4 A / D conversion means 6 D / A conversion means 7 Drive means 17 Phase compensation means 18 Phase compensation means

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[Procedure amendment]

[Submission date] October 1, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0053

[Correction method] Change

[Correction content]

According to the fourth aspect of the present invention, the continuous-time transfer function set so that its relative order is larger than 1 is about twice the peak frequency of the machine signal in the high-frequency region of the controlled object. Bi-linear transformation using the frequency of as the sampling frequency, and using the obtained discrete-time transfer function,
Since the phase compensation of the output of the D / A converting means in the future of one sampling period is performed based on the inputs of the current and past A / D converting means and the outputs of the current and past D / A converting means, An excessive amount of phase lead is required for the phase compensation means,
Even if the gain rises above the gain crossover frequency, vibration due to mechanical resonance of the transfer system is reliably suppressed, the gain margin of the servo system is improved, and a stable wideband servo is simple and inexpensive. It has the effect of realizing a system.

Claims (4)

[Claims] 1. A positional deviation detecting means for detecting a positional deviation amount from a target position of a controlled object, a sampling means for sampling an output of the positional deviation detecting means in accordance with a sampling timing, and an output of the sampling means. , And a discrete-time transfer function obtained by performing a zero-order hold-invariant conversion of the continuous-time transfer function whose relative order is set to be greater than 1. Phase compensating means for compensating the phase of the output of the analog / digital converting means, digital / analog converting means for analogizing the output of the phase compensating means, and a control target of the controlled object according to the output of the digital / analog converting means. A feedback servo system digital control device having a drive means for controlling a position. 2. A displacement amount from a target position of a controlled object is detected and sampled at a predetermined sampling timing,
A phase in a digital controller of a feedback servo system for controlling the position of the controlled object by converting the digital signal into a digital signal by the analog / digital converting means and performing phase compensation, and then reconverting the analog signal by the digital / analog converting means. In the compensation method, the continuous-time transfer function in the phase compensation is set so that its relative order is greater than 1, and the continuous-time transfer function is transformed by the zero-order hold invariant conversion at the cycle of the sampling timing. A time transfer function is obtained, and the obtained discrete time transfer function is used to input the present and past analog-digital conversion means and the present and past digital signals.
A phase compensation method for a digital controller of a feedback servo system, characterized in that phase compensation of the output of the digital-analog converter in the future of one sampling period is performed based on the output of the analog converter. 3. A positional deviation detecting means for detecting an amount of positional deviation from a target position of a controlled object, a sampling means for sampling an output of the positional deviation detecting means in accordance with a sampling timing, and an output of the sampling means. And a continuous time transfer function set so that the relative order thereof is larger than 1 with a frequency about twice the peak frequency of mechanical vibration in the high frequency region of the controlled object. Using the discrete-time transfer function obtained by the bilinear transformation as the sampling frequency, the phase compensating means for compensating the phase of the output of the analog-digital converting means and the output of the phase compensating means are analogized. Digital-analog conversion means, and the digital
A feedback servo system digital control device comprising: a drive unit that controls the position of the controlled object according to the output of the analog conversion unit. 4. A displacement amount from a target position of a controlled object is detected and sampled at a predetermined sampling timing,
A phase in a digital controller of a feedback servo system for controlling the position of the controlled object by converting the digital signal into a digital signal by the analog / digital converting means and performing phase compensation, and then reconverting the analog signal by the digital / analog converting means. In the compensation method, the continuous-time transfer function in the phase compensation is set so that its relative order is greater than 1, and the continuous-time transfer function is about 2 times the peak frequency of mechanical vibration in the high-frequency region of the controlled object.
A discrete-time transfer function is obtained by a bilinear transformation with a doubled frequency as a sampling frequency, and the obtained discrete-time transfer function is used to calculate the current and past inputs of the analog-digital conversion means and the current and past inputs. A phase compensation method for a digital controller of a feedback servo system, characterized in that phase compensation of the output of the digital-analog converter in the future of one sampling period is performed based on the output of the digital-analog converter.