JPH05325449A - Speed controller for carriage - Google Patents

Abstract

PURPOSE:To efficiently execute a rough retrieval by registering in advance a speed table which can set various kinds of maximum acceleration corresponding to a positional error. CONSTITUTION:In a target speed computer 3, an acceleration conversion table in which a relation between a distance X between a position of a carriage and a target position and a target speed V of the carriage at its position is registered in advance with regard to plural accelerations alpha, beta (alpha<beta) is stored. At the time of controlling the speed of the carriage 1, a position detector 2 detects a carriage position, a speed detector 5 detects a carriage speed, and outputs are inputted to a subtracter 4 through a signal converter 6, respectively. Subsequently, the subtracter 4 reads out acceleration appropriate relating to the target position from the conversion table and calculates the carriage speed from a set speed and a detected speed. Therefore, the carriage can be moved efficiently by applying the maximum speed and small acceleration at a distant position and a close position, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carriage speed control device, and more particularly to a device for controlling the movement speed of a carriage in positioning a head of an optical disk device.

[0002]

2. Description of the Related Art An optical disk device can store a large amount of information as compared with a floppy disk or a hard disk, but has a problem that access time is slow. As a factor that greatly affects the access time, there is a carriage moving mechanism that mounts an optical head.

Conventionally, in the carriage moving mechanism used in this kind of apparatus, a conversion table called a target speed table in which the relationship between the target position and the speed is registered in advance is built into the system, and the speed of the optical head according to this table. Is always controlled.

The target speed table used for controlling the speed of the carriage is a function of the position of the carriage and is represented by the following equation. V = √ (2αX) V: Velocity α: Maximum acceleration X: Distance to target position

The maximum acceleration α is determined by the weight of the carriage, the propulsive force of the linear motor, etc. As a result, a target speed table showing the relationship between the distance X from the target position and the target speed V at that position is determined as shown in FIG.

Here, when the optical head accesses a track, the linear motor performs a rough search up to the vicinity of the target position and a fine search near the target position to reduce the access time. In order to perform the rough search at high speed, the maximum acceleration or a value close to the maximum acceleration is used. The head is moved to the target position by feeding back to the carriage using the speed error between the speed of this target speed table and the actual speed obtained from the speed detector.

[0007]

However, in the target speed table in the above-mentioned conventional apparatus, there are variations in the maximum acceleration due to various influences in the actual movement of the carriage, and it is possible to match the target speed table during deceleration. There are often situations where it is not possible. Therefore, when the head reaches the target position, deceleration is insufficient and the speed remains, and when the carriage stops, the positional error from the target position becomes large.

If the target speed table is set by the acceleration that can be ensured at least against such inconvenience, there is a problem that the time required for the rough search increases.

The present invention has been made in view of the above problems of the conventional apparatus, and a speed table capable of setting different maximum accelerations according to position errors is registered in advance in the system to improve the efficiency of rough search. A speed control device is provided.

[0010]

To achieve the above object, the present invention provides a speed detector for detecting the speed of a carriage, a position detector for detecting the position of the carriage, a position of the carriage and a target position. Of the relationship between the distance X of X and the target speed V of the carriage at that position, a target speed calculator for calculating the target speed from a table in which a plurality of accelerations are registered in advance, and a speed based on the data from the target speed calculator and A carriage speed control device is configured by including a calculator that calculates the speed of the carriage from the speed detected by the speed detector.

[0011]

According to the above construction, at a position away from the target position, the maximum acceleration is used to move at a high speed, and even if sufficient acceleration cannot be obtained, a plurality of accelerations are registered in advance in the table. Therefore, it is possible to follow a table with a reduced acceleration, and it is possible to improve the efficiency of carriage movement.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a general mechanism of speed servo control for moving a carriage to a target position, which has been conventionally used, will be described with reference to FIG.

In FIG. 2, in the servo circuit of the optical disk device, a position detector 2 for detecting the speed of the carriage 1 is arranged in the carriage movement path. The control unit of the apparatus has a built-in target speed table in which the relationship between the distance X between the current position of the carriage 1 and the target position and the target speed V of the carriage 1 at that position is set in advance. From this table, the target speed calculator 3 reads the speed information corresponding to the detected position of the carriage 1, and the speed information corresponding to the output of the position detector 2 is supplied to the subtractor 4 via the signal converter 6. It

The other input of the subtractor 4 is supplied with the speed information detected by the speed detector 5 as a signal through the signal conversion circuit 6, and the subtractor 4 executes subtraction between the both input signals. The moving speed of the carriage 1 is determined. This carriage speed is detected by the speed detector 5 and serves the purpose of the servo circuit.

In this embodiment, the above-mentioned target speed table registers the relationship between the distance X between the current position of the carriage 1 and the target position and the target speed V of the carriage 1 at that position, but at least two different values are registered. Acceleration α, β (α <β)
The relationship in which is set is registered in advance. The distance at which these two accelerations α and β are switched is X1, and the maximum speed is Vma.
When x is set, the target speed V becomes as follows depending on the distance from the target position and the speed. When 0 ≦ X ≦ X1, V = √ (2αX) When X1 ≦ X and V ≦ Vmax V = √ (2β (X−X0)) where X0 is the position where V = 0 when the acceleration β. When V> Vmax It is represented by V = Vmax.

FIG. 1 shows a target speed table of the present embodiment in which the above two accelerations α and β are set. At a distance far from the target, the carriage 1 moves at the maximum speed Vmax, and when the position detector 2 detects that the position is close to the target position, the acceleration β is read out to approach the target position, and when the distance X becomes smaller. The acceleration α is read from the table, and the carriage 1 moves to the target position with a small acceleration.

[0017]

As described above, according to the present invention, the target velocity table based on the acceleration that can perform the coarse search stably and can be ensured at the minimum can be used regardless of the variation in the maximum acceleration that can be generated by the carriage. It is possible to perform a rough search faster than the case.

[Brief description of drawings]

FIG. 1 is a diagram showing a target speed table having a plurality of accelerations according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a speed servo control system that moves to a target position by using a target speed table and speed information of a speed detector.

FIG. 3 is a diagram showing a conventional target speed table.

[Explanation of symbols]

 1 Carriage 2 Position detector 3 Target speed calculator 4 Subtractor 5 Speed detector 6 Signal converter X Distance between current carriage position and target position V Target speed at current carriage position

Claims (1)

[Claims] 1. A relationship between a speed detector for detecting the speed of the carriage, a position detector for detecting the position of the carriage, a distance X between the position of the carriage and a target position, and a target speed V of the carriage at that position. A target speed calculator that calculates a target speed from a table in which a plurality of accelerations are registered in advance, and a calculator that calculates the speed of the carriage from the speed based on the data from the target speed calculator and the detected speed of the speed detector. A carriage speed control device comprising: