JPH01235082A - Servo device for optical disk drive device - Google Patents

Abstract

PURPOSE:To cope with deterioration with age of the title device by securing such constitution where a control means controls the gain of a servo system via a gain control means at the time of detection of the start of working to automatically obtain the secondary resonance frequency and the resonance value of a mechanism system and actuating a notch filter based on these obtained values. CONSTITUTION:At the time of detection of the start of working, a control means 12 controls the gain of a servo system via a gain control means 11 to obtain the secondary resonance frequency and the resonance value of a mechanism system. Then the means 12 actuates a notch filter 3 contained in the servo system based on those obtained resonance frequency and value. As a result, the center frequency and its resonance value of the filter 3 are automatically controlled by self-learning actions so as to secure previously accordance with the secondary resonance frequency and the resonance value of the mechanism system. Then the servo control is ensured hereafter during a steady action based on said frequency and value of the filter 3. Therefore, the control of the filter 3 is not required for each product put on a production line despite the variance of parts of the mechanism system. Thus it is possible to cope with the deterioration with age of a servo device for an optical disk driver.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a servo device for an optical disk drive device.

In a conventional optical disk drive device, a servo device including a voice coil and a near motor is configured as shown in FIG.

A signal generated from the positional deviation signal generating means 1 in response to the positional deviation of the controlled object [not shown] from the target position is applied to the notch filter 3 via the 1-phase compensation means 2, where it is band-stopped. After that, a servo system is configured so that the driving means 4 drives the mechanical system 5 to control the object to be controlled in a direction to bring it closer to the target position. Here, notch filter 3
is interposed to prevent oscillation of the servo system due to secondary resonance of the mechanical system 5. Conventionally, the notch filter 3
As shown in the figure, the notch filter 3 is of a fixed center frequency type composed of a resistor 6, a capacitor 7, voltage followers 8, 9, etc., and the transfer function of the notch filter 3 is 1+R"C2S2 1+ (RC/4 (1- K))S+R2C2S”. Here, K is the gain of the voltage follower, S is the Laplace operator, and R and C are the values of the resistor 6 and capacitor 7. FIG. 6 shows the frequency characteristics of this notch filter 3, and the center frequency fN can be determined by fn=1/2πCR. The resonance value can be adjusted with a variable resistor 10.

Even if the notch filter 3 with a fixed center frequency is used in this way, the values of each resistor 6 and capacitor 7 are determined so as to match the 52nd order resonance frequency of the Ia system, and the resonance value is adjusted using the variable resistor 10. By adjusting, oscillation of the servo system due to secondary resonance of the mechanical system 5 can be prevented.

Problems to be Solved by the Invention However, - In boat fishing, the secondary resonance frequency and resonance value of the mechanical system 5 vary widely depending on the parts. However, even if the secondary resonance frequency and resonance value of the mechanical system vary, the servo can be adjusted without having to adjust it for each product one by one. The purpose is to provide a servo device that can be

Means for Solving the Problems The servo device of the present invention includes a positional deviation signal generating means for detecting a positional deviation of a controlled object from a target position, and a notch for band blocking passage of an output signal of the positional deviation signal generating means. A servo system is composed of a filter and a drive means for driving a mechanism system for moving a controlled object based on an output signal of the notch filter, and a gain adjustment means for adjusting a gain of the servo system, and an optical disk drive device. control means for adjusting the gain of the servo system using the gain adjustment means when detecting the start of operation to obtain a secondary resonance frequency and a resonance value of the mechanical system, and operating the notch filter using these values; It is characterized by having the following.

According to this configuration, when detecting the start of operation of the optical disk drive apparatus, the control means adjusts the gain of the servo system using the gain adjustment means and automatically adjusts the gain of the servo system.
The next resonance frequency and resonance value are determined, and the control means operates the notch filter using the determined values.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3. Components having the same functions as those in FIG. 4 showing the conventional example will be described with the same reference numerals.

FIG. 1 shows a servo system of the present invention, in which a gain adjustment means 11 is interposed in the servo system, and a control means 12 for setting the frequency characteristics of this gain adjustment means 11 and the notch filter 3 is also provided.

Next, the operation will be explained based on the configuration of the control means 12.

When power-on of the optical disk drive device is detected, the control means 12 uses the gain adjustment means 11 to set a gain G1 lower than that in the normal state, and applies servo to the notch filter 3 with an instruction to stop its operation. Next, the control means 12 uses the gain adjustment means 11 to gradually increase the servo gain. At this time, the amplitude of the positional deviation signal generated at the output of the positional deviation signal generating means 1 gradually decreases, but once a certain servo gain is reached, the amplitude of the positional deviation signal begins to increase. At this time, the servo gain is the gain at which the mechanical system 5 starts to oscillate due to secondary resonance. The control means 12 temporarily fixes the servo gain here. FIG. 2 schematically shows the relationship between the positional deviation signal and the servo gain up to this point, and G is the gain at which oscillation starts.

Next, the control means 12 operates the notch filter 3 and gives an instruction to sweep its center frequency fn from the maximum value to the minimum value considered as the secondary resonance frequency of the mechanical system 5.

Then, the frequency at which the amplitude of the positional deviation signal becomes the minimum is estimated to be the secondary resonance frequency of the mechanical system 5, and the center frequency fN is fixed at that frequency. Further, the control means 12 similarly adjusts the resonance value of the notch filter 3 using the gain adjustment means 11.

Finally, the control means 12 uses the gain adjustment means 11 to increase the servo gain to the treasure value G3, and ends the start-up operation.

The control means 12 is configured to perform the above-mentioned series of learning and automatic adjustment operations each time the optical disk drive device starts operating. Here, the start of operation of the optical disk drive device is defined as the time when the power is turned on or when the power is turned on. This refers to when a start command given after power is detected is detected. Figure 3 shows the servo system's round transfer function and gain 61~G.
, shows a schematic diagram of the relationship between . Here, f t fz + f
3 are gain crossover frequencies corresponding to Go, G, ,G, respectively.

fMxrfMz are the primary and secondary resonance frequencies of the mechanical system 5.

The notch filter 3 is composed of a digital filter using a DSP (digital signal processor), and is expressed by the following equation.

Z″. is the n-cycle delay operator, and T is the sampling period. The center frequency fN of the notch filter 3 is f
It corresponds to the average value of l and f2, and the resonance value is determined by the value of f2-f, so from the desired center frequency and resonance value, f, f
By determining 2 and further determining α and β, the coefficients of the digital filter can be determined. In this way, the resonance frequency and its resonance value can be swept numerically.

Effects of the Invention As described above, according to the present invention, the gain adjusting means adjusts the gain of the servo system, and when the start of operation of the optical disk drive device is detected, the gain adjusting means is used to adjust the gain of the servo system to adjust the gain of the servo system. Since the control means is provided to determine the secondary resonance frequency and resonance value of the optical disc drive and operate the notch filter installed in the servo system using these values, the mechanical system is adjusted in advance before the optical disk drive device enters normal operation. The center frequency and resonance value of the notch filter can be automatically adjusted by self-learning to match the secondary resonance frequency and resonance value of Even if there are variations in parts, there is no need to go through the process of adjusting the notch filter for each product on the production line, and as it can handle changes over time, it can be expected to operate stably over a long period of time. .

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an embodiment of the servo device of the present invention;
The figure is a schematic diagram of the relationship between the amplitude of the positional deviation signal and the servo gain during the self-adjustment process of the same device, Figure 3 is a frequency characteristic diagram of the servo gain of the same device, Figure 4 is a configuration diagram of a conventional servo device, and FIG. 5 is a block diagram of the fixed center frequency type notch filter in FIG. 4, and FIG. 6 is a transfer characteristic diagram of the same nonch filter. DESCRIPTION OF SYMBOLS 1... Positional deviation signal generation means, 3... Notch filter, 4... Drive means, 5... Mechanical system, 11... Gain adjustment means, 12... Control means. Agent Yoshihiro Morimoto Figure 2 CrlcT2

Claims (1)

[Claims] 1. A positional deviation signal generating means for detecting the positional deviation of the controlled object from the target position, a notch filter for band-blocking passage of the output signal of the positional deviation signal generating means, and a mechanical system for moving the controlled object. A servo system is constituted by a drive means driven based on an output signal of the notch filter, a gain adjustment means for adjusting the gain of the servo system, and the gain adjustment means is used when detecting the start of operation of the optical disk drive device. A servo device comprising: a control means for adjusting a gain of a servo system to obtain a secondary resonance frequency and a resonance value of the mechanical system, and operating the notch filter using these values.