JPH04358369A - Information recording/reproducing device - Google Patents

Abstract

PURPOSE:To make the seek operation of a head accurate by synchronously operating a speed control for every specified cycle waiting until next speed detection. CONSTITUTION:An optical disk 1 is rotated at a constant speed by driving a driving system on an information recording medium. An optical system 2 is provided with a sensor for optically recording information on the disk 1, reproducing the recorded information of the disk 1 and detecting a reflected light. A condensing objective lens provided in the optical system 2 is moved in the direction of a focus by a focus actuator 13 and the objective lens is moved in the direction of a tracking by a tracking actuator 12. Here, an error signal is detected and control the speed of the disk 1 by the focus or tracking difference detectors 3 and 4 based on the output of the sensor. At this time, the speed control for every specified cycle is waited until the next speed detection and the speed control is synchronized with the speed detection. Thus, the follow up ability of the information recording or the regenerating head to a target head is improved and the seek operation of the head is accurately controlled.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an information recording/reproducing device for recording or reproducing information on an information recording medium such as a magnetic disk or magneto-optical disk, and in particular to a speed control device for a head used for recording or reproducing information. It is related to.

0002

[Prior Art] Conventionally, as a speed control method for moving an information recording or reproducing head to a desired position on an information recording medium, a method in which the speed of the head is sequentially monitored and seek is performed according to a predetermined operation schedule is common. It is true. FIG. 6 is a diagram showing the relationship between the reference speed, the actual speed, and the current applied to the actuator for driving the head in the general speed control method. In the figure, the reference speed Vref
represents the planned speed of the head, which is calculated according to the residual distance to the target position. Reference speed Vref
is determined by the following formula.

[0003] Vref = [2・α(S−λ/2・N)]1/2
...(1) Note that in equation (1), S is the target moving distance, α is the deceleration acceleration, and N is the zero cross count value. Further, in order to cause the head speed to follow this reference speed, the actual head speed is sequentially detected. For example, the zero-crossing point of the tracking error signal is detected, the time Δtn from the zero-crossing point to the next zero-crossing point is measured, and from this time and the track pitch λ, the current head speed Vn
is calculated. Expressed by the formula, it is as follows. Note that the distance between zero cross points corresponds to 1/2 of the track pitch λ.

[0004]Vn =λ/2×1/Δtn...(2
) When controlling the speed of the head, an actuator command value is calculated from the current speed and the current target speed at regular intervals, and the head speed is controlled by the obtained command value. Command value Act is calculated by the following formula.

[0005]Act=K(Vref-Vn)...
(3) However, K is the feedback gain of the speed control system. In this way, in the conventional method, the head speed is sequentially detected and the command value obtained from the detected head speed and the target speed is fed back at regular intervals to control the head to the target speed as shown in FIG. The vehicle was followed by the vehicle and sought to reach the target position according to a predetermined schedule.

[0006]

However, in the conventional speed control method described above, the head speed can only be obtained at each track cross, so when speed control is performed at a fixed period, for example, as shown in FIG. When speed control is performed at point Pc, the speed obtained at point Pc' is used, and a time delay of Δtc occurs during this time. Similarly, at points Pb and Pa, Δtb and Δt
A. A time delay will occur. Therefore, the velocity at point Pc becomes c', which is a value different from the original velocity c, and similarly, at point Pb, the velocity is b' compared to the original velocity b.
, Pa, the original speed a becomes a'. As described above, in the past, it was difficult to accurately control the seek operation of the head because a large error occurred in the head speed due to the timing difference between speed detection and control.

The present invention has been made to solve these problems, and its purpose is to provide an information recording system in which the seek operation of the head can be accurately controlled by synchronizing speed detection and speed control. The purpose is to provide a playback device.

[0008]

[Means for Solving the Problems] It is an object of the present invention to provide means for calculating a target speed of an information recording or reproducing head according to a residual distance to a target position of an information recording medium, and An information recording device comprising means for detecting speed, and means for controlling a head driving means based on the speed obtained at each predetermined cycle and the target speed, and seeking the head to the target position while following the target speed. This is achieved by an information recording and reproducing apparatus characterized in that the speed control at each predetermined cycle is performed on standby until the next speed detection, and the speed control is performed in synchronization with the speed detection.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an information recording/reproducing apparatus according to the present invention. Note that FIG. 1 shows an optical disc device as an example.

In FIG. 1, reference numeral 1 denotes an optical disk which is an information recording medium, and is rotated at a constant speed by a drive system (not shown). Reference numeral 2 denotes an optical system for optically recording information on the optical disc 1 or reproducing recorded information on the optical disc 1. The optical system 2 includes a semiconductor laser that is a light source for recording and reproduction, various optical components that perform predetermined optical processing on the laser beam, a sensor that detects reflected light from the optical disk 1, and the like. 1
A tracking actuator 2 moves a condensing objective lens (not shown) provided in the optical system 2 in the tracking direction, and a focus actuator 13 moves the objective lens in the focusing direction. The optical system 2 and these two actuators are built into the optical head and configured to be movable in the radial direction of the optical disc 1. 14 is a linear motor that moves the optical head in the radial direction of the optical disk 1, and 10 is a driver for the linear motor 14.

Further, 3 is a tracking error detector that detects a tracking error signal based on the sensor output within the optical system 2, and 4 is a focus error detector that similarly detects a focus error signal based on the sensor output. The error signal detected by each error detector is
After being converted into a digital signal by the converter 5, it is output to the digital signal processing section 6. The digital signal processing unit 6 constitutes the main control unit of the optical disc device of this embodiment, and includes an I/O control unit 7 that controls input and output of signals, and arithmetic processing necessary for control according to a predetermined control program. Execute C
It is composed of a PU 8 and a memory 9 for storing various data used for control. In addition, the digital signal processing section 6
has the role of speed control when the optical head seeks. In this speed control, the timing of the speed control is performed in synchronization with the zero cross point, which is the speed detection timing, and this will be described in detail later. When controlling the seek operation of the optical head, the CPU 8 calculates a command value to the driver 10 of the linear motor 14, and this command value is sent to the D/A converter 11 via the I/O control section 7. Here, the signal is converted into an analog value and then applied to the driver 10. Similarly, the command values for the tracking actuator 12 and focus actuator 13 are also sent to the CPU.
8 are sent to the D/A converter 11 via the I/O control unit 7, each converted into an analog signal, and then output to the tracking actuator 12 and the focus actuator 13.

Next, the operation of this embodiment will be explained. FIG. 2 is a time chart showing the relationship between the target speed and actual speed of the optical head, the speed control timing, and the tracking error signal in the speed control of this embodiment. In the figure,
a, b, c, and d indicate the original fixed-cycle speed control timing, and a', b', c', and d' indicate the speed control timing of this embodiment. a', b', c', d
As shown in the figure, the timing ' coincides with the zero-crossing point of the tracking error signal, and the speed control is performed in synchronization with the zero-crossing point, which is the speed detection timing. For example, constant cycle speed control at point a waits until the next zero cross point a', and executes speed control at point a'. Also, b, c, d
Similarly, speed control is not performed at the points b', c', and d', which are the next zero-crossing points. In this case, the target speed of the optical head may be calculated using the above-mentioned equation (1) at each speed control point. Further, the current speed Vn is detected by a well-known zero-crossing counting method, but here it is calculated by the following equation, taking into account the waiting time until the zero-crossing point.

[0013]Vn = (λ/2・r0)/Δt...(
4) However, r0 is the zero cross count value, and Δt is the sum of the speed control interval and the waiting time until the next zero cross point. Speed detection using the above zero-cross counting method is performed up to two tracks before the target track, and thereafter the speed is detected by counting the time between zero-crossing points. In FIG. 2, the speed control from point d' onwards is based on the speed detection. In addition, in this embodiment, since speed control is performed with constant acceleration, the steady deviation Ve
exists, but this steady-state deviation can be compensated for in various ways. The steady-state deviation Ve is expressed by the following formula.

Ve = α/ωn = α/(2πf0) (5)
However, α is the deceleration acceleration in the speed control profile,
f0 is the speed control band.

Based on the above basic concept, the concrete operation of this embodiment will be explained. FIG. 3 is a flowchart showing the overall speed control operation during optical head seek in this embodiment. In FIG. 3, first, the number of jumps (SK-TRACK), which is the number of tracks from the current position of the optical head to the target position, is input to the CPU 8 (S31), and then it is determined whether the number of jumps is more than two. (S32). When the number of input tracks is more than 2, a speed control cycle timer is set to perform speed control at a constant cycle (S33), and when the number is 2 or less, the timer is set to 1/2.
A timer for measuring the time between tracks is set (S34). The period of the speed control period timer is set to 4 kHz here. After that, the track counting operation is started (S35), the tracking servo loop is turned off (S36), and furthermore, as an initial drive, D
The linear motor 14 is started by setting an acceleration pulse to the /A converter 11 and applying it to the driver 10 (S37). The initial setting is thus completed, and the main routine remains in a standby state until the target track is reached (S38).

FIG. 4 shows an interrupt routine that is executed every fixed period of the speed control period timer set in S33 when the number of jumps is two or more. The period of the speed control period timer corresponds to the period of the speed control timing shown in FIG. 2, and the interrupt routine is executed at fixed periods such as a, b, c, and d. In this interrupt routine, as described above, speed control is not performed at fixed cycle speed control timings, but speed control is performed each time by waiting until the next zero-crossing point of the tracking error signal. Figure 4
, first, in S41 to S43, processing for detecting the speed at the zero cross point is executed. S41 is a process of measuring the waiting time until the next zero-crossing point with respect to the constant cycle speed control timing, and is timed by the timer function of the CPU 8. Further, S42 is a process of inputting the count value of the zero-crossing point of the tracking error signal to the CPU 8, and S43 is a process of detecting the next zero-crossing point.

When the zero-crossing point is detected, the CPU 8 calculates the current speed Vn and target speed Vref at the zero-crossing point (S44), and also issues a command to the driver 10 of the linear motor 14 from the obtained current speed and target speed. A value is calculated (S45). The current speed Vn is calculated using the obtained time and zero cross count value as described above (
The target speed Vref is calculated using the equation (1). Further, the command value Act of the driver 10
is calculated using equation (3). The obtained command value is sent to the D/A converter 11 via the I/O control unit 7, where it is converted into an analog signal and then output to the driver 10 (S
46). Thereby, the driver 10 drives the linear motor 14 based on the given command value, and the speed of the optical head is controlled to follow the target speed. Next, determine whether the number of remaining tracks to the target is within 2 (S
47), if two or more remain, the processing of one interrupt routine ends. Then, the same process is performed again at point b, which is the speed control timing of the next cycle shown in FIG. 2, and the interrupt routine process is executed at regular intervals, such as at point c and point d. In this way, the target track is approached, and when it is determined that the number of remaining tracks is less than 2 (S47), the previously set speed control period timer is turned off (S48), and the A timer is started (S49), and the processing of the interrupt routine is ended.

FIG. 5 is a flowchart showing the speed control operation when the timer for the time between 1/2 tracks is set. In this speed control, each time a zero-crossing point is detected, the time between zero-crossing points is measured (S5
1) The time measurement result is stored in a register (not shown) of the CPU 8. In FIG. 2, the timer starts when the optical head reaches point d', and measures the time from point d' to the next zero-crossing point of the tracking error signal. The CPU 8 calculates the current speed Vn of the optical head using the above-mentioned equation (2) using the timed time, and calculates the target speed Vref using the above-mentioned equation (1) (S5
2). Next, the CPU 8 calculates a command value from the obtained current speed and target speed (S53), and outputs it to the driver 10 (S54). The command value of the driver 10 is calculated by the above-mentioned equation (3). This completes one control operation, and the same control is performed each time a zero-crossing point is detected, such as the next zero-crossing point and the next zero-crossing point. In this way, the optical head approaches the target track, and when the optical head reaches the target track in S38 of FIG. 3, the speed of the optical head becomes zero as shown in FIG. As a result, the optical head stops when it reaches the target track, and the seek operation ends.

As described above, in this embodiment, the speed control is performed in synchronization with the speed detection, so the timing of speed detection and speed control coincide, and the timing of speed detection and speed control coincides, eliminating the problem caused by time delay as in the conventional case. This solves the problem of speed errors. Therefore, since control can be performed using an accurate current speed, the optical head seeks to the target position while almost following the target speed as shown in Figure 2, which is clear from the comparison with the conventional speed profile shown in Figure 7. As a result, the ability to follow the target speed can be significantly improved compared to the conventional method.

In the above embodiment, when measuring time, the timer function of the CPU 8 is used.
An external timer or counter with similar functions may be provided. In addition, although the explanation was given using an optical disk device as an example,
The present invention is not limited to this, and a recording/reproducing apparatus using a magnetic disk can of course be suitably used.

[0021]

As described above, according to the present invention, it is possible to significantly improve the followability of the information recording or reproducing head to the target speed, and the seek operation of the head can be accurately controlled.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an information recording/reproducing apparatus of the present invention.

FIG. 2 is a time chart showing the relationship between the target speed of the optical head, the actual speed, speed control timing, and tracking error signal in speed control of the optical head in the embodiment of FIG. 1;

FIG. 3 is a flowchart showing the overall speed control operation of the optical head in the embodiment of FIG. 1;

FIG. 4 is a flowchart showing an interrupt routine when setting the speed control period timer in the flowchart of FIG. 3;

FIG. 5 is a flowchart showing a routine for setting time measurement between 1/2 tracks in the flowchart of FIG. 3;

FIG. 6 is an explanatory diagram showing the relationship between a reference speed, an actual speed, and an applied current to an actuator in a general head speed control method.

FIG. 7 is a time chart showing the relationship between the target speed of the head, the actual speed, the tracking error signal, and the speed control timing in a conventional method of performing speed control at constant intervals.

[Explanation of symbols]

1 Optical disc 2 Optical system 3 Tracking error detector 6 Digital signal processing section 8 CPU 10 Driver 12 Tracking actuator 14 Linear motor

Claims (1)

[Claims] 1. Means for calculating a target speed of an information recording or reproducing head according to a residual distance to a target position of an information recording medium; means for detecting the speed of the head; In the information recording and reproducing apparatus, the information recording and reproducing apparatus includes means for controlling a head driving means based on the set speed and a target speed, and for seeking to a target position while making the head follow the target speed. An information recording/reproducing device characterized in that it waits until the next speed detection and performs speed control in synchronization with the speed detection.