JP3695944B2 - Disturbance suppression device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a disturbance suppression device that suppresses a malfunction of a control target due to a disturbance signal, and is likely to be affected by external vibration, impact, etc. Suitable for information recording / reproducing apparatus such as SSVC (Solid State Video Camera) composed of a camera that stores imaging information in a solid-state memory, such as a magnetic) disk reproducing / recording apparatus, a computer optical (magnetic) disk reproducing / recording apparatus Is.
[0002]
[Prior art]
With the development of optical (magnetic) disk technology, optical (magnetic) disk devices are used in various situations, and optical (magnetic) disk devices are often used while being carried outdoors as well as indoors. Yes. Along with this, the problem of vibration and shock applied to the player from the outside with the optical (magnetic) disk device has become important.
[0003]
In the conventional optical (magnetic) disk device, the servo is likely to be lost due to disturbance such as vibration or shock. For example, in a device that is used in a situation where the player itself is not stationary, such as a portable or in-vehicle CD player, focus servo that is focus control or tracking that is track follow-up control due to various disturbances generated by the movement of the device. The servo was off.
[0004]
In order to solve such problems, portable CD players and MD players are equipped with an external storage device called a shock proof memory, and once information is stored in the memory at a high speed, the information is read out at a normal speed. The method is adopted. This technique makes it possible for the user to hear that there is no skipping on the surface if there is an impact of a few seconds even if the servo slippage occurs.
[0005]
Also, in-vehicle CD players have realized a structure in which vibration is not transmitted to the player by wrapping the player with a shock absorbing material.
[0006]
[Problems to be solved by the invention]
However, external hardware components are indispensable when using hardware to reduce the effects of vibration due to disturbances, and are not easy to apply. There was a drawback.
[0007]
Furthermore, the range of application of the method is limited due to the characteristics of the hardware. For example, the shock-proof memory method cannot be applied to a recording type optical (magnetic) disk device because the reproduction signal is temporarily held in a storage medium. Met.
[0008]
In addition, the method using a shock absorber for in-vehicle use has a drawback that the entire device becomes dimensionally large and cannot be applied to a portable optical (magnetic) disk device that is required to be downsized.
[0009]
In recent years, high-speed rotation CD-ROMs for computers have rapidly spread. However, the influence of vibration generated by a high-speed rotation motor on an actuator including an optical system cannot be ignored.
[0010]
Accordingly, the present invention solves the above-described problems and establishes a general-purpose disturbance suppression technique that is not a technique applied only to a specific optical (magnetic) disk device. As a software process without adding new wear parts, the disturbance observer is applied to the focus servo system and tracking servo system of optical (magnetic) disk devices to build a system that is resistant to disturbances such as vibration and shock. Objective.
[0011]
[Means for Solving the Problems]
The disturbance suppressing device of the present invention includes a control target (1) that is affected by a disturbance, a control unit (2) that generates a drive signal for the control target (1), and a desired input signal of the control target (1). An error signal (6) indicating a difference from the input signal (4) is generated based on the output signal (5) from (4) and the control object (1), and the error signal (6) is generated by the control unit. An error signal generator (3) to output to (2), a first disturbance observer calculator (11) for obtaining a first disturbance observer signal based on an output signal of the error signal generator (3), and the controller based on the drive signal and the first disturbance observer signal (2) determine the second disturbance observer signal, a second disturbance observer calculating unit for output to the controlled object (1) and (12), is composed of the first 1 disturbance observer calculating unit (11) includes a low-pass filter The second disturbance observer calculation unit (12) is derived from the low-pass filter and is derived from the ideal model of the controlled object (1) and passes a signal in a specific frequency band. It is characterized by increasing the gain .
[0013]
The first disturbance observer calculation unit (11) and the second disturbance observer calculation unit (12) are realized and processed as digital control devices.
[0014]
The controlled object (1) is an objective lens positioning device used for recording / reproducing information on / from an optical recording medium or a magneto-optical recording medium.
[0015]
The error signal (6) is a tracking error signal for performing track following control or a focus error signal for performing focus control.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the present invention will be described with reference to FIGS. 1 to 6 by taking as an example a “tracking servo system” when a tracking actuator of a CD player is a control target.
[0017]
In the embodiment of the present invention, a tracking servo system using a tracking actuator will be described. However, the disturbance suppressing device of the present invention is not limited to this, and can be applied to a focus servo system for a focus actuator. is there.
[0018]
FIG. 1 is a basic configuration diagram of a positioning control device for an optical (magnetic) disk device using a disturbance observer.
[0019]
In the same figure, the disturbance suppressing device of the present invention is
(1) A model of the control object 1 that is close to reality taking into account nonlinear elements such as friction, dead time element, and higher order resonance (hereinafter referred to as “control object”, and the transfer function of the control object 1 is defined as P _a (s ))
(2) Control unit 2 for improving the steady state characteristics and stability of the system,
(3) A tracking error signal (hereinafter referred to as a reference error signal) indicating a deviation from the reference signal of the control target 1 based on the reference input signal 4 that is a desired position of the control target 1 and the output signal 5 that represents the actual position of the control target 1 Simply referred to as an “error signal”).
(4) A first disturbance observer calculation unit 11 that receives the error signal 6 as an input and outputs a feedback signal 13 by calculation similarly to the control unit 2;
(5) a second disturbance observer calculation unit 12 that adds the calculation result signal 14 of the control unit 2 and uses the signal 15 as an input signal and outputs the control signal 7;
It is composed of
[0020]
Specifically, the control unit 2 receives the error signal 6 and performs calculation as a compensation element such as PID control or phase advance / delay control, and then outputs the calculation result signal 14.
[0021]
Similar to the control unit 2, the first disturbance observer calculation unit 11 receives the error signal 6 and outputs a feedback signal 13 by calculation, and is added to the calculation result signal 14 of the control unit 2 to obtain a signal 15. The second disturbance observer calculation unit 12 receives the signal 15 as an input signal and outputs a control signal 7. The control signal 7 becomes the input signal 9 of the controlled object 1 together with the disturbance signal 8.
[0022]
The first disturbance observer calculation unit 11 is derived from the low-pass filter Q shown in FIG. 1 and the ideal model P _n (s) of the actuator that is the control target 1 shown in FIG. 1, and this first disturbance observer calculation is performed. The unit 11 performs an operation with the error signal 6 as an input, and outputs the operation result as a feedback signal 13. The feedback signal 13 is added to the operation result signal 14 of the control unit 2 to be a signal 15.
[0023]
Further, the second disturbance observer calculation unit 12 is derived from the low-pass filter Q of FIG. 1, and the second disturbance observer calculation unit 12 performs calculation with the signal 15 as an input, and then outputs the control signal 7. The control signal 7 is added to the disturbance signal 8 to become a signal 9 to become an input signal 9 of the controlled object 1 and drive the controlled object 1.
[0024]
Here, the low-pass filter Q can realize the transfer function Q (s) / P _n (s) of the first disturbance observer calculation unit 11, that is, the denominator of the transfer function of the disturbance observer calculation unit 11 has the numerator order. In order to be larger or equal, it is necessary to set the transfer characteristic so that the gain does not increase at high frequencies.
[0025]
The first disturbance observer calculation unit 11 is represented by a transfer function Q (s) / P _n (s) and includes a first filter having a characteristic of allowing a signal in a specific frequency band to pass.
[0026]
The second disturbance observer calculation unit 12 is represented by a transfer function 1 / (1-Q (s)) using a low-pass filter Q, and has a characteristic of increasing the gain of a signal in a low frequency band. It consists of two filters.
[0027]
FIG. 2 is a disturbance observer block as a digital servo for digitally processing the positioning control device of FIG.
[0028]
In FIG. 2, the control unit 2, the first disturbance observer calculation unit 11, and the second disturbance observer calculation unit 12 designed in the continuous time domain are all separated from the transfer function in the continuous time domain using a bilinear transformation. Q (s) / P _n (s) is converted to Q (z ⁻¹ ) / P _n (z ⁻¹ ), 1 / (1-Q (s)) is 1 / Each is converted to (1-Q (z ⁻¹ )).
[0029]
Further, each pulse transfer function is realized as a digital filter in the digital signal processing unit. The device 16 is an AD converter for converting the error signal 6 in the continuous time domain into the error signal 18 in the discrete time domain, and the device 17 is for converting the discretized control signal 19 into the control signal 7 in the continuous time domain. It is a DA converter.
[0030]
Here, FIG. 3 shows a flowchart for deriving the pulse transfer functions of the first disturbance observer calculation unit 11 and the second disturbance observer calculation unit 12.
[0031]
In step S1 in FIG. 3, initial settings such as a sampling frequency are performed. In step S2, an ideal model P _n (s) of the control target 1 is set. In step S3, the gain values in the circuit blocks for the first disturbance observer calculation unit 11 and the second disturbance observer calculation unit 12 shown in FIG. 2 are set.
[0032]
These gain values differ depending on each optical (magnetic) disk device. However, in the optical (magnetic) disk device of the present invention, the error signal generating gain in the error signal generating unit 3, the driver gain for driving the actuator, the light This applies to the optical gain of the pickup unit.
[0033]
In step S4, the order of the low-pass filter and the cutoff frequency are set.
[0034]
In step S5, the transfer function Q (s) of the low-pass filter is derived.
[0035]
In step S6, the relative order of the transfer function Q (s) / _Pn (s) of the first disturbance observer calculation unit 11 is obtained. If the order of the numerator is larger than the order of the denominator, the process returns to step S4. Is less than or equal to the denominator order, the process proceeds to step S7.
[0036]
In step S7, the transfer function 1 / (1-Q (s)) in the second disturbance observer calculation unit 12 is derived. In step S8, the transfer function Q (s) / P _n (s) of the first disturbance observer calculation unit 11 and the transfer function 1 / (1−Q (s)) of the second disturbance observer calculation unit 12 are digitalized. Filtering is performed, using all bilinear transforms, from continuous time domain transfer function to discrete time domain pulse transfer function, Q (z ^-1 ) / P _n (z ^-1 ), 1 / (1-Q (z ^-1 )).
[0037]
Next, the present embodiment using the disturbance observer calculation unit composed of the first disturbance observer calculation unit 11 or the second disturbance observer calculation unit 12 designed according to FIG. 3 will be described using frequency characteristics.
[0038]
FIG. 4 shows an example of a computer simulation result of the frequency response from the disturbance signal 8 (= d) to the output signal 5 (= y) in a system designed by setting the pass band of the low-pass filter 4 to 800 (Hz). It is.
[0039]
In FIG. 4, the vertical axis represents gain (disturbance attenuation), and the horizontal axis represents frequency. The dotted line graph is for the system to which the disturbance observer is not applied, and the solid line graph is the data for the system to which the disturbance observer is applied.
[0040]
From FIG. 4, it can be seen that the system to which the disturbance observer is applied has a significant disturbance suppressing force in the low frequency range, particularly in the pass band of the low pass filter Q.
[0041]
Further, the disturbance observer having the configuration of the present invention shown in FIG. 2 is applied to a tracking servo control system of an actual CD player, and the disk device is intentionally installed on an exciter that generates a disturbance signal. A comparative experiment of the suppression effect is performed, and the actual disturbance observer effect is shown by the experimental result.
[0042]
FIG. 5 shows a comparison experiment result of the error signal 6 in the system to which the disturbance observer is not applied and the system to which the disturbance observer is applied when the sine wave disturbance signal of 25 (Hz) and 3 (m / s ² ) is added in the tracking direction of the CD player. It is.
[0043]
In the two graphs, the upper signal waveform represents the error signal of the device without the disturbance observer, and the lower signal waveform represents the error signal of the device with the disturbance observer. As is clear from the result of the excitation comparison experiment in FIG. 5, the influence of the sinusoidal disturbance appears remarkably in the error signal of the system to which the disturbance observer is not applied.
[0044]
On the other hand, it can be seen that the influence of the sinusoidal disturbance is greatly suppressed in the error signal 6 of the system to which the disturbance observer is applied.
[0045]
Furthermore, not only a continuous sinusoidal disturbance signal but also a similar excitation experiment was performed for an instantaneous shock disturbance. FIG. 6 shows an error signal in a system to which a disturbance observer is not applied and a system to which the disturbance observer is applied when a sinusoidal disturbance signal is generated for one period of generation time 100 (ms) and 13 (m / s ² ) in the tracking direction of the CD player. It is a comparative experiment result.
[0046]
In the two graphs shown in FIG. 6, the upper signal waveform represents the error signal 6 of the apparatus not equipped with the disturbance observer, and the lower signal waveform represents the error signal 6 of the apparatus equipped with the disturbance observer.
[0047]
As for the experimental results in FIG. 6, as in FIG. 5, the error signal 6 of the system to which the disturbance observer is not applied is affected by the vibration and the amplitude is very large. However, in the system to which the disturbance observer is applied, the vibration is generated. After that, it can be confirmed that the normal control state is restored in about 200 (ms).
[0048]
In the above embodiment, the tracking servo system has been described as an example. However, the present invention is not limited to this, and it goes without saying that the present invention can also be applied to a focus servo control system of an optical (magnetic) disk. Needless to say, in this case, the error signal 8 becomes a “focus error signal”.
[0049]
Furthermore, the present invention is realized as digital servo control, and all of the control unit 2 and the disturbance observer calculation unit are realized by using a digital signal processing device.
[0050]
【The invention's effect】
As is apparent from the above description, according to the present invention, the optical (magnetic) disk device having the configuration shown in FIG. 2 can be used as an information recording / reproducing device without adding any hardware components such as an external memory and an external sensor. It is very effective in reducing the influence of disturbances such as vibrations and shocks in the positioning control of the used disturbance suppressing device, specifically, actuators such as focus servo and tracking servo.
[0051]
Further, since this is a disturbance suppression technique using a control theory that is not a conventional countermeasure against vibrations in hardware, other optical (magnetic) disk devices having a similar control structure have the same effect.
[0052]
Further, regarding a control system composed of a PID controller and a phase advance / lag controller that have been widely used in the past, the two operation blocks shown in FIG. 2, that is, the first disturbance observer calculation unit 11 and the second disturbance observer calculation. The disturbance signal applied to the control system can be suppressed only by adding the section 12.
[0053]
Moreover, the disturbance suppression area can be easily adjusted by setting the pass band of the low-pass filter.
[Brief description of the drawings]
FIG. 1 is a block diagram of a disturbance observer driven by an error signal.
FIG. 2 is a block diagram of a disturbance observer as a digital servo.
FIG. 3 is a flowchart for deriving a disturbance observer calculation unit.
FIG. 4 is a diagram illustrating a frequency response characteristic of a disturbance characteristic.
FIG. 5 is a diagram showing a comparison experiment result of an error signal in a system to which a disturbance observer is not applied and a system to which a disturbance observer is applied when a sine wave disturbance signal is added.
FIG. 6 is a diagram showing a comparison experiment result of an error signal in a system to which a disturbance observer is not applied and a system to which the disturbance observer is applied when a sinusoidal disturbance signal is added for one cycle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Model of real control object 2 ... Control part 3 ... Error signal generation part 4 ... Reference input signal 5 ... Output signal 6 ... Error signal 7 ... Control signal 8 ... Disturbance signal 9 ... Input signal to control object (1) DESCRIPTION OF SYMBOLS 10 ... Disturbance estimation signal 11 ... 1st disturbance observer calculating part 12 ... 2nd disturbance observer calculating part 13 ... Output signal 14 of 1st disturbance observer calculating part ... Output signal 15 of the control part 2 ... 2nd disturbance observer calculating part Input signal 16 ... AD converter 17 ... DA converter 18 ... Discrete time domain error signal 19 ... Discrete time domain control signal 20 ... Disturbance observer

Claims (4)

A control object (1) that is affected by a disturbance, a control unit (2) that generates a drive signal for the control object (1), a desired input signal (4) of the control object (1), and the control object ( An error signal (6) indicating a difference from the input signal (4) is generated based on the output signal (5) from 1), and the error signal (6) is output to the control unit (2). A generator (3);
A first disturbance observer calculation unit (11) for obtaining a first disturbance observer signal based on the output signal of the error signal generation unit (3);
A second disturbance observer calculation unit (12) for obtaining a second disturbance observer signal based on the drive signal of the control unit (2) and the first disturbance observer signal and outputting the second disturbance observer signal to the control target (1);
Consisting of
The first disturbance observer calculation unit (11) includes a low-pass filter and an ideal model of the control target (1), and allows a signal in a specific frequency band to pass through.
The second disturbance observer calculation unit (12) includes the low-pass filter and increases the gain of a signal in a low frequency band.    The disturbance suppressing device according to claim 1, wherein the first disturbance observer calculating unit (11) and the second disturbance observer calculating unit (12) are realized and processed as a digital control device.    3. The disturbance suppressing device according to claim 1, wherein the control object (1) is an objective lens positioning device used for recording / reproducing information on / from an optical recording medium or a magneto-optical recording medium.    4. The disturbance suppressing device according to claim 1, wherein the error signal (6) is a tracking error signal for performing track following control or a focus error signal for performing focus control. .

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