JPS61251913A - Method and device for positioning carriage - Google Patents

Abstract

PURPOSE:To stop a carriage in a target position accurately when the carriage cannot be stopped immediately because the speed of the carriage is too high, by using the first pulse which allows the carriage to follow up a prescribed pattern to move the carriage to the target position and the second pulse which stops the carriage in the position control mode. CONSTITUTION:In case of fine adjustment of a light spot 51 on an optical disc 49, a tracking signal which a tracking signal generating circuit 53 generates by the output of a tracking sensor 52 is inputted to an MPU 76. The MPU 76 turns on a speed control mode switch 73 to set the speed control mode, and the intersections between a moving grating 61 and a fixed grating 62 are detected by a moire sensor 63 to output a moire pulse 69 from a moire pulse generating circuit 67. Reference clocks in the pulse 69 are counted by a moire pulse interval measurer 74, and the counted value is applied to the MPU 76. The second pulse other than the first pulse which moves the carriage to the target position is used to stop the carriage in the target position accurately when the speed of the carriage is high.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for positioning a carriage, and particularly to a carriage that is required to be positioned accurately with respect to a target position, such as a carriage on which a head is mounted in an optical disk device. Concerning carriage positioning.

[Background of the invention]

A conventional carriage positioning method and apparatus will be described using a carriage mounted with a head in an optical disk device as an example. That is, access to an optical disk in an optical disk device is performed by a coarse actuator that moves the head in the radial direction of the optical disk, and a fine actuator that is provided within the head and makes fine adjustments. The speed of the coarse actuator is first controlled to move the head at an optimum speed based on the number of seek instruction moiré lines that indicate the amount of movement of the head, and when it approaches the target position, the speed control is switched to position control. The operation of such a coarse actuator will be explained using the drawings.

FIG. 4 is a block diagram showing a conventional phase actuator control system, and is configured to switch between speed control and position control using a mode changeover switch. In speed control, a seek instruction moiré number indicating the amount of movement of the head is set in the difference counter 1. here,
The number of moire lines refers to the number of lines at which the movable side grating 12 provided on the head carriage and the fixed side grating 11 that is fixed to the main body of the apparatus and do not move optically intersect, as shown in FIG. This shows the amount of movement of the carriage.

The optimum speed generator 2 determines a predetermined optimum speed based on the number of seek instruction moiré lines set in the difference counter]-, and outputs a target speed signal to the speed comparator 3.

The speed comparator 3 compares the actual speed (zero at the beginning of speed control) signal of the coarse actuator output from the coarse actuator speed detector 7 with the target speed signal, and calculates the difference between the actual speed signal and the target speed signal as a mode. It is output to the current amplifier 5 via the switching circuit 4. As a result, the coil 6 for driving the coarse actuator is energized, and the coarse actuator moves at an optimum speed.

When the coarse actuator moves, as shown in FIG. 6, the moire sensor 8 detects the optical intersection of the fixed side grating 11 and the movable side grating 12 as a moire signal, and the moire pulse generation circuit 9 outputs a moire pulse based on the moire signal. do. The difference counter 1 counts down the internally set number of seek instruction moiré lines every time a moire pulse is input. Further, the coarse actuator speed detector 7 detects the time interval of the coarse actuator from the interval of moiré pulses and outputs it to the speed comparator 3. The speed control described above is executed until the content of the difference counter 1 becomes zero, that is, until the seeks for the number of moiré lines instructed to seek are completed. When the content of the difference counter 1 becomes zero, a switching signal S is output to the mode switching circuit 4, and the mode is switched to position control. FIG. 7 shows flowcharts 1 to 1 which outline the speed control described above.

In position control, the position of the sum actuator is locked in the following manner. That is, the moire signal output from the moire sensor 8 is sent to the compensation circuit 10 as a position error signal.
is input. The output of the compensation circuit 1o is inputted to a coarse actuator driving coil 6 via a mode switching circuit 4 and a current amplifier 5, and the coarse actuator is driven. FIG. 6 is a waveform diagram for explaining the above-mentioned position control, and a position where the coarse actuator movement distance is A is set as the target position. In this case, at time to, the count value of the difference counter 1 becomes zero, and at this point the speed control shifts to the position control. If the moire signal is positive, the coarse actuator is driven in the inner circumferential direction as shown in FIG.
When the moire signal is negative, the coarse actuator is driven in the outer circumferential direction.

In this way, the position control of the coarse actuator is executed and the target position is reached! Locked to Ao.

However, the conventional coarse actuator position control described above has the following problems. That is, the moiré signal is the sixth
As shown in the figure, it changes sinusoidally as a function of the position of the coarse actuator, and has nonlinear characteristics as a position error signal. In such a system, the following phenomenon occurs depending on the speed of the coarse actuator when switching from speed control to position control.

That is, if the speed of the coarse actuator is too fast, position control is started at a position that is more than ±1800 away from the target position AO, expressed in terms of the phase of a sine wave. As a result, the target position is
±360° expressed not by position A but by the phase of the sine wave
3 from distant position A+I, A-, or position A
Position control is performed using positions shifted by 60 degrees as target positions. As a result, the coarse actuator moves to the target position.
1!11 A The problem arises that the position is locked at a position deviated from o.

FIG. 8 is a time chart showing a state in which position control is started when the speed of the coarse actuator is too high. As shown in the figure, speed control is started at time To, and shifts to position control at the rising edge of the moiré pulse at time to. At this time, since the speed of the coarse actuator is too fast, the position is not locked to the target position A, but is locked to a position A+I which is 360° ahead of the target position A in the phase of the sine wave.

A conventional technique related to a method for positioning a carriage on which a head is mounted in the above-mentioned optical disk device is described in, for example, Japanese Patent Laid-Open No. 58-091536.

[Purpose of the invention]

The present invention has been made in view of the problems of the prior art described above, and an object of the present invention is to provide a method and apparatus for positioning a carriage that can reliably lock the carriage at a target position.

[Summary of the invention]

In the carriage positioning method of the present invention, in order to position a carriage capable of reciprocating along a predetermined route to a target position on the route, a first sine wave signal whose period changes depending on the moving speed of the carriage is transmitted. and forming a first pulse based on the first sine wave signal, and causing the carriage to follow a predetermined speed pattern until the count value of the -th pulse reaches a target number. mode, and when the target number is reached, the carriage is switched to a position control mode for stopping the carriage at the target position.
A second pulse having a predetermined phase relationship with the pulse of Drive the carriage in a direction in which the numerical value returns to the value at the start of counting, and after the count value of the second pulse returns to the value at the start of counting, drive the carriage in accordance with the first sine wave signal. The carriage is controlled so that the carriage is stopped at a position where the first sine wave signal becomes zero.

Further, the carriage positioning device of the present invention includes a first grid provided on the carriage and a second grid fixed to the device main body.
a first sinusoidal signal having a period dependent on a moving speed of the carriage, and a first pulse based on the first sinusoidal signal;
pulse forming means for counting the first pulses and controlling the speed of the carriage by following a predetermined speed pattern until the counted value reaches the target value; After reaching the target position, the carriage is provided with a position control means for positioning the carriage to the target position based on the position error signal, and in particular, a third grating is provided on the carriage,
A second sine wave signal having a predetermined phase difference with the first sine wave signal is formed by optical intersection with the second grating, and a second pulse is formed based on the second sine wave signal. Second to do
pulse forming means; counting means for counting up/down the second pulse according to the moving direction of the carriage after shifting to position control; In order to move the carriage in the direction returning to the starting value, the counted value is used as a position error signal for the position control means, and when the counted value is equal to the counting starting value,
The present invention is characterized by comprising a switching means for changing the position error signal of the position control means to a first sine wave signal.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram showing a servo system of a recording and reproducing device for an optical disk device, which is an application example of the present invention. A light beam emitted from a light source (not shown) of the optical head is focused by an objective lens 50 to form a light spot 51 on the optical disk 49. At this time, the NA of the objective lens is set to 0.
50. When the wavelength of the light source is 83° nun, the spot size (diameter at which the intensity is 1/e2) is about 1.6 μm.

Regarding the method of creating a tracking signal representing the deviation between the track center and the spora 1 center, see Japanese Patent Application Laid-Open No. 49-509.
There are the spot-four-pull method disclosed in Japanese Patent Laid-Open No. 49-60702 and a method using diffracted light, but the details will not be described here.

Fine adjustment of the light spot 51 by the fine actuator is performed as follows. That is, a tracking signal is generated by the tracking signal generation circuit 53 from the output signal of the tracking sensor 52, and feedback control is performed using this tracking signal as an error signal for the number of seek instruction tracks inputted to the MPU 76, and the galvanometer mirror 55 for tracking is to drive. As a result, guide grooves (for example, pitch 1.6) are formed on the optical disk 49.
μm). The above operation is similar to that of a conventional fine actuator.

Next, access to the optical disk 49 by the coarse actuator to which the present invention is applied will be explained. First, access using a coarse actuator is performed when the head needs to be moved so far that it cannot be covered by access using a fine actuator. For example, when seeking over 200 tracks, access is performed using a coarse actuator. Access by the coarse actuator is achieved by energizing the coil 58 from the amplifier 86 and moving the entire carriage 59.

First, speed control will be explained. The MPU 76 turns on only the speed control mode switch 73 to set the speed control mode. Next, of the two movable side gratings 60 and 61 provided on the carriage 59, the movable side grating 61 and the fixed side grating 62
The moire sensor 63 detects the intersection with the moire signal 65.
Output as . The moire pulse generator 67 receives the moire signal 65 and outputs a moire pulse 69. The moire pulse interval measuring device 74 counts how many pulses of the reference clock (1.0 MHz) are output within the output interval of the moire pulse 69 and outputs the counted value to the MPU 76 .

The MPU 76 refers to an internal pulse interval/speed table (consisting of ROM) 77 to determine the moiré pulse 6.
Convert the pulse interval of 9 to actual speed.

On the other hand, the MPU 76 sets the number of seek-instructed moiré lines in an internally provided difference counter (not shown). The MPU 76 creates a seek moiré number/target speed table (R
78 (consisting of OM), the target speed is determined. Next, the MPU 76 outputs the difference between the actual speed and the target speed to the D/A converter 80 as a speed error signal. D/A converter 80
converts the input digital speed error signal into an analog speed error signal and outputs it to the speed control compensation circuit 87.

The compensation circuit 87 outputs a current signal according to the speed error signal to the amplifier 86 via the speed control mode switch 73,
This energizes the coil 58 of the coarse actuator and drives the carriage 59. Note that the difference counter in the MPU 76 is counted down each time the moiré pulse 69 is output (for example, at the time of rising).

Therefore, an appropriate target speed of the carriage 59 can always be accurately determined, and appropriate speed control can be performed until the content of the difference counter in the MPU 76 becomes zero. The speed control described above is similar to the speed control according to the prior art, and the same processing as shown in the flowchart shown in FIG. 4 is executed.

Next, position control, which is a feature of the present invention, will be explained.

When the difference counter in the MPU 76 becomes zero,
The MPU 76 turns off the speed control mode switch 73, turns on the position control mode switch 82, and shifts to position control. The position control is based on two moiré pulses 69.62 based on two movable gratings 61.62 provided on the carriage 59.
70.

In other words, the two movable side gratings 61 and 62 are in phase with each other by 9
They are provided on the carriage 59 at positions shifted by 0'. As a result, the moire signals 65 and 66 outputted by the moire sensors 63 and 66 are 99 degrees each other, as shown in FIG.
It becomes a sine wave with a phase difference of 0°. Moiré signal 65 with
．． 66, moire pulse generation circuits 67 and 68 form moire pulses 69.70 with 10% of the amplitude as a threshold level, as shown in FIG. These moiré pulses 69 and 70 also have a phase difference of 90° from each other. Moiré pulses 69° and 70 are input to a running direction detector 71, and a running direction signal 72 is input to an MPU 76 and a moire pulse counter 81. When the running direction signal 72 indicates the inner circumferential direction, the moire pulse counter 81 decrements by 1 at the rise and fall of the moire pulse 70, and when the running direction signal 72 indicates the outer circumferential direction, the moire pulse counter 81 decrements the moire pulse 70 by one turn. Count up at the end of the rising stage. The moiré pulse counter 81 is reset by the MPU 76 when the count value of the difference counter within the MPU 76 becomes zero, that is, when shifting from speed control to position control. As a result, the moire pulse counter 81 counts the deviation from the target position by 1- at a period of 1/2 of the moire pulse 70. For example, in FIG. 2, target position A
Assuming that the coarse actuator moves from O to position AO' which is 400° in the outer circumferential direction, the count value 83 of the moiré pulse counter 81 becomes 3.

Next, when the count value 83 of the moire pulse counter 81 is zero, the moire position error signal input switch 85 is turned on, and the moire signal 65 is input to the compensation circuit 84 for position control. Further, when the count value 83 of the moire pulse counter 81 is a number other than zero, the moire position error signal input switch 85 is turned off, and the output of the D/A converter 88 (an analog of the count value of the moire pulse counter 81) is turned off. value) is input to a compensation circuit 84 for position control. Therefore, in this case, the analog value of the counted value 83 (including the + and - signs) is input to the compensation circuit 84, and the analog value of the counted value 83 is input to the compensation circuit 84, and the analog value of the counted value 83 is inputted to the coil via the amplifier 86 so that the counted value 83 of the moiré pulse counter 81 becomes zero. 5
8 is energized. As a result, the carriage 59 moves and the count value 83 of the moire pulse counter 81 gradually approaches zero, and when it reaches zero, the moire position error signal input switch 8
5 is turned on, and the moiré signal 65 is input to the compensation circuit 84. Therefore, the position error signal input to the compensation circuit 84 for position control has a waveform as shown in FIG. 2, for example.

FIG. 3 is a time chart showing an example of the operation of the embodiment described above, and shows a case where the speed control is shifted to the position control while the speed of the carriage 59 is still too high. That is, at time To, speed control is started, and at time to, the speed control shifts to position control. At this time, the speed of the carriage 59 has not decreased sufficiently, and therefore, the phase of the sine wave of the moiré signal 65 is 360 degrees from the target position A.
Move to advanced position A+I. Thereafter, a position error signal based on the count value 83 of the moiré pulse counter 81 is used to detect time 1. From there, the carriage 59 is driven in the direction of the target position A. At time t2, when the count value 83 of the moiré pulse counter 81 counts down to zero,
A position error signal based on the moire signal 65 is input to the compensation circuit 84. As a result, the carriage 59 is locked to the target position A.

In addition, in the embodiment described below, the movable side grating 6
0.61 and the fixed side grating 62, the moiré pulses 69 and 70 have been described as having a phase difference of 90 degrees from each other, but needless to say, the present invention is limited to the phase difference of 90 degrees. It's not a thing. .

Further, in the above embodiment, the moire pulse counter 81 counts the rise and fall of the moire signal 70, but the present invention is not limited to this, and for example, the moire pulse counter 81 counts the rise and fall of the moire signal 70. It is also possible to adopt a configuration in which a pulse signal (having a frequency twice that of the moiré pulse 70 described above) generated by the moire pulse 70 is counted.

〔Effect of the invention〕

According to the carriage positioning method and apparatus of the present invention, when shifting from speed control to position control, the carriage can be reliably stopped at the target position even if the carriage speed is too high to stop immediately.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention, and is a block diagram showing a servo system of a recording/reproducing device of an optical disk device.
3 is a time chart showing an example of the operation of the embodiment shown in FIG. 1, and FIG. 4 is a coarse actuator for accessing an optical disk according to the prior art. A block diagram showing the control system of
Figure 5 is an explanatory diagram showing the movable side grating and the fixed side grating, and Figure 6 is the control system of the conventional coarse actuator shown in Figure 5.
9- Waveform diagram for explaining the operation, FIG. 7 is a flowchart 1 to 1 to show the speed control of the control system of the conventional coarse actuator shown in FIG. 5, and FIG. 8 is a waveform diagram for the conventional coarse actuator shown in FIG. This is a time chart 1- showing an example of the operation of the control system. 49... Optical disk, 50... Objective lens, 51...
・Light spot, 52...1 Herakking sensor, 53
... 1 - racking signal generation circuit, 55 ... galvanometer mirror-158 ... coil, 59 - carriage, 60
．． 61... Movable side lattice, 62... Fixed side lattice, 63
．． 64...Moire sensor, 65.66...Moire signal, 67, 68・Moire pulse generation circuit, 69°70・
・Moire pulse, 7]... Running direction detector, 72...
・Travel direction signal, 73...Speed control mode switch, 7
4...Moire pulse interval measuring device, 76...MPU, 77
...Pulse interval/speed table, 78...Moiré number/target speed table, 80.88...D/A converter,
81... Moiré pulse counter, 82... Position control mode switch, 84.87... Compensation circuit, 85...
Moiré position error signal input switch, 86...Amplifier.

Claims (1)

[Claims] 1. In order to position a carriage capable of reciprocating along a predetermined route to a target position on the route, a first sine wave signal whose period changes depending on the moving speed of the carriage is provided. and a speed control mode in which a first pulse is formed based on the first sine wave signal, and the carriage follows a predetermined speed pattern until the count value of the first pulse reaches a target number. In the servo system, a second pulse having a predetermined phase relationship with the first pulse is driven, and when the target number is reached, the carriage is switched to a position control mode for stopping the carriage at the target position. The second pulse is generated and the second
count the pulses of and drive the carriage in a direction in which the count value of the second pulse returns to the value at the start of counting, and after the count value of the second pulse returns to the value at the start of counting,
A method for positioning a carriage, characterized in that the carriage is driven and controlled in accordance with the first sine wave signal, and the carriage is stopped at a position where the first sine wave signal becomes zero. 2. The count of the second pulse is 1/2 of the second pulse.
2. The carriage positioning method according to claim 1, wherein the carriage positioning method is performed every cycle. 3. The second pulse is created from a second sine wave signal having a predetermined phase relationship with the first sine wave signal, as set forth in claim 1 or 2. Carriage positioning method. 4. The first sine wave signal is formed by detecting an optical intersection between a movable side grating attached to the carriage and a fixed side grating provided opposite thereto. The carriage positioning method according to the range 1, 2, or 3. 5. The second sine wave signal is formed by detecting an optical intersection between a movable side grating attached to the carriage and a fixed side grating provided opposite thereto. A method for positioning the carriage as described in scope 3. 6. Detecting the optical intersection of the first grating provided on the carriage and the second grating fixed to the apparatus main body to form a first sine wave signal having a period corresponding to the moving speed of the carriage. , a first pulse forming means for forming a first pulse based on the first sine wave signal, and counting the first pulse and following a predetermined speed pattern until the counted value reaches a target value. In the servo system, the servo system is equipped with a speed control means for controlling the speed of the carriage by adjusting the count value, and a position control means for positioning the carriage at the target position based on a position error signal after the count value reaches a target value. A second sine wave signal having a predetermined phase difference with the first sine wave signal is formed by optically crossing the second sine wave signal, and based on the second sine wave signal, a second sine wave signal is formed. a second pulse forming means for forming a second pulse; a counting means for counting up/down the second pulse according to the moving direction of the carriage after shifting to position control; When they are not equal, the count value is used as a position error signal for the position control means to move the carriage in the direction in which the count value returns to the count start value, and when the count value is equal to the count start value, the position control means 1. A carriage positioning device comprising: switching means for converting a position error signal of the means into a first sine wave signal. 7. The carriage positioning device according to claim 6, wherein the counting means counts up/down every 1/2 period of the second pulse.