JPH0817016B2 - Disk unit - Google Patents

Description

Detailed Description of the Invention 【Overview】

The present invention relates to a disk device equipped with a servo circuit that controls a speed by applying a seek current according to a difference between a target speed and an actual speed to a voice coil motor, and can favorably raise an acceleration current even if a difference amount is small. For the purpose of increasing the speed, an accelerating means for forcibly adding a predetermined value for acceleration to the difference signal at the acceleration stage at the seek start is provided in the servo loop.

[Industrial applications]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk device provided with a servo circuit that controls a speed of a head carriage toward a target track position by passing a seek current according to a difference between a target speed and an actual speed to a voice coil motor. In recent years, the speed of seek access for moving the head to a target track position in a disk device is increasing, and with the increase in the speed of seek access, a so-called 1-difference seek for moving the head to an adjacent track position is performed. Access is also required to be significantly faster,
A highly responsive servo circuit that matches the speed of the difference seek is required.

[Prior art]

Conventionally, in a servo circuit of a disk device for stopping and moving a head to a target track position by driving a head carriage with a voice coil motor, a seek start is performed in accordance with a difference amount between a target track and a current track position. A speed control servo loop for generating a speed and supplying a seek current according to the difference between the target speed and the actual speed to the voice coil motor is provided. Here, the target speed keeps a predetermined maximum speed level above a predetermined difference amount, and when the target speed is below a predetermined difference amount, for example, it has a characteristic of decreasing in proportion to the square value of the difference amount. The target speed is at the minimum speed level.

[Problems to be Solved by the Invention]

However, in the servo circuit of such a disk device, a seek current corresponding to the difference between the target speed determined by the difference amount and the actual speed is applied at the start of the seek to accelerate the seek current. When the target speed level is extremely small, the rise of the acceleration current flowing through the voice coil motor becomes worse. That is, as shown in FIG. 5, in one difference seek, when the seek current starts to flow at the seek start at time t1 and the actual speed comes out, the actual speed and the target speed are very small because the target speed level is very small. There is a problem that the seek current at the time of acceleration becomes a triangle, the rise of the acceleration current is deteriorated, and the access time of one difference seek becomes long as a result of there being no difference. The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a disk device that realizes high-speed access by favorably raising the acceleration current even if the difference amount is small.

[Means for Solving the Problems]

FIG. 1 is an explanatory view of the principle of the present invention. First, the present invention provides a disk device having a servo loop for supplying a seek current corresponding to a difference signal ΔE between a target speed E1 and an actual speed E2 to a voice coil motor 10 to control a speed of a head carriage 12 toward a target track position. The servo circuit of is targeted. Regarding such a servo circuit, in the present invention, the predetermined value Ecc for acceleration is selected at the addition point 16 to which the acceleration signal generating means for generating the predetermined value Ecc for acceleration and the difference signal ΔE of the servo loop are input. Switching means 18 for supplying the electric power, an acceleration end detecting means for detecting the end of acceleration when the difference signal ΔE becomes zero in the acceleration stage, and a switching means 18 is turned on at the time of seek start to turn the addition point 16 to a predetermined acceleration point. A switching control means for supplying a value (Ecc) and turning off the switching means 18 upon detection of the acceleration end by the acceleration end detection means to stop the supply of the predetermined value (Ecc) for acceleration to the addition point is provided. And

[Action]

In the disk device of the present invention having such a configuration, even if the target velocity level is one difference seek with a very small target velocity level, the predetermined velocity for acceleration is forcibly irrelevant regardless of the difference between the target velocity and the actual velocity. Since the value is added to the servo loop, the seek current can quickly rise to the saturation level during the acceleration period, and a sufficient acceleration current can be passed, so the access time for one differential seek is greatly shortened. It is possible to meet the demand for high-speed equipment.

【Example】

FIG. 2 is a block diagram of an embodiment showing an embodiment of the present invention. In FIG. 2, reference numeral 22 is an MPU which constitutes a control logic, and generates target speed data for seek operation based on the current head position and target track position at the time of access from the host device. In addition, the forward command signal C1 or the reverse command signal C2 is output according to the target track direction. 24 is a target speed generation circuit, which converts the target speed data from the MPU 22 corresponding to forward or reverse to an analog signal voltage from the DA converter, and the switch 26-1 turned on by the forward command signal C1 during the forward control. A target speed signal for forward is generated via the switch, and a target speed signal for reverse control is output via the changeover switch 26-2 which is turned on by the reverse command signal C2 at the time of reverse control. 28 is a velocity error amplifier, which is a target speed voltage for forward or reverse from the target speed generation circuit 24.
E1 is input via the resistor R1 or R2, the difference signal ΔE from the actual speed E2 input via the resistor R3 is obtained, and the difference signal ΔE amplified by the amplifier 30 in which the capacitor C1 and the resistor R4 are connected to the feedback circuit is calculated. appear. The output of the velocity error amplifier 28 is input to the speed control / position control switching circuit 32. The speed control / position control switching circuit 32 is provided with a changeover switch 34-1 for inputting the output of the velocity error amplifier 28 and a changeover switch 34-2 for inputting a position signal from a position signal generating circuit (not shown). The changeover switch 34-1 is turned on by a coarse signal (speed control signal) from the MPU 22, while the changeover switch 34-2 is controlled by a fine signal (position control signal) from the MPU 22. That is, from the seek start until the difference amount to the target track becomes zero, the coarse signal becomes valid and the changeover switch 34
When -1 is turned on, speed control is performed, and when the difference amount becomes zero, the fine signal becomes valid and the changeover switch 34-2 is turned on to switch to position control to keep the head on the target track. Change The outputs of the changeover switches 34-1 and 34-2 are commonly connected via resistors R8 and R9, input to an amplifier 36 having a feedback resistor R10 and an input resistor R11, and the power amplifier of the next stage via the amplifier 36.
The power amplifier 38 converts the output voltage from the amplifier 36 into a driving current, and the driving current is supplied to the voice coil motor 10. Voice coil motor 10 is head 40
The head 40 is mechanically connected to the head carriage 12, and controls the movement of the head 40 in the radial direction of the disk medium (not shown). The servo signal from the disk medium obtained by the head 40 is given to the demodulation circuit 42, and the position signal demodulated by the demodulation circuit 42 and the voice coil motor 10 detected by the power amplifier 38.
The actual speed E2 is obtained by the speed detection circuit 44 based on the current signal flowing to the amplifier 30 provided in the velocity error amplifier 28.
It is fed back to the input stage of through the resistor R3. The structure of such a servo circuit is the same as the conventional one,
In addition to this, in the present invention, an acceleration forcibly adding a predetermined voltage for acceleration to the input stage of the amplifier 36 provided in the speed control / position control switching circuit 32 at the acceleration stage at the seek start. Means are newly provided. That is, the resistor R6 and the changeover switch 18 are connected to the input of the amplifier 36.
A circuit for inputting the positive power supply voltage + Ecc via -1 and a circuit for inputting the negative power supply voltage -Ecc via the resistor R7 and the changeover switch 18-2 are provided as acceleration value generating means. Changeover switch for inputting power supply voltage + Ecc 18-
1 is ON / OFF controlled by the forward acceleration signal C3, and the changeover switch 18-2 for inputting the power supply voltage −Ecc is ON / OFF controlled by the reverse acceleration signal C4. FIG. 3 shows an acceleration control circuit of the present invention for generating a forward acceleration signal C3 and a reverse acceleration signal C4 for the changeover switches 18-1, 18-2 provided in the speed control / position control switching circuit 32 of FIG. It is a block diagram of an Example. In FIG. 3, a difference signal ΔE from the velocity error amplifier 28 is input to the acceleration control circuit, and
Forward command signal C1 and reverse command signal C from MPU22
2. A seek signal C3 indicating that the seek operation is in progress, and a seek start pulse P are input. The difference signal ΔE is given to the positive input terminal of the comparator 46,
The minus input terminal of the comparator 46 is grounded, and when the difference signal ΔE becomes zero voltage, that is, when the actual speed voltage E2 reaches the target speed voltage E1 after the seek start and coincides, it is detected as the acceleration end point. , H level output is inverted to L level output. The comparator 46 constitutes acceleration end detection means.
The output of the comparator 46 is input to the AND gate 50 via the inverter 48 and directly to the AND gate 52. The AND gate 50 receives the forward command signal C1 and the seek signal C3, and the AND gate 52 receives the reverse command signal C2 and the seek signal C3. The outputs of the AND gates 50 and 52 are input to the NOR gate 54 and further input to the clear terminal CLR of the FF 58 via the inverter 56. The seek start pulse P is applied to the clock terminal CLK of the FF 58, and the seek start pulse P is applied to the D terminal via the capacitor. The output of the FF58 is input to each of the NAND gates 60 and 62, the forward command signal C1 is input to the NAND gate 60 via the inverter 64, and the NAND gate 60 is also input.
The reverse command signal C2 is input to 62 via the inverter 66. Then, the output of the NAND gate 60 becomes the forward acceleration signal C3 for adding the acceleration voltage + Ecc to the servo loop difference signal ΔE, and the output of the NAND gate 62 becomes the servo loop difference signal ΔE a predetermined value for acceleration −. It becomes the reverse acceleration signal C4 for adding Ecc. Next, the operation of the embodiment shown in FIGS. 2 and 3 will be described with reference to the operation timing chart of FIG. In FIG. 4, first, when a seek start pulse P for one difference forward seek is output at time t1, the MPU 22 sets the forward command signal C1 and the seek signal C3 to H level in accordance with the seek start pulse P. . Therefore, the FF 58 receiving the seek start pulse P is set, and the C6 signal as an output falls from the H level to the L level. At the start of seek, the difference signal ΔE is at the maximum level, the comparator 46 produces an H level output, the AND gate 50 is disabled by the inversion of the inverter 48, and the forward command signal C1 and the seek signal C3 are both at H level. Even when the level is reached, the C5 signal from the NOR gate 54 is kept at the L level. In this way, when the FF58 is set by receiving the seek start pulse P and the output C6 signal falls from the H level to the L level, at this time, the NAND gate 60 causes the inverter based on the forward command signal C1 which becomes the H level. Since the L level signal is input from 64, the forward acceleration signal C3, which was at the H level until then, falls to the L level. Due to the operation of the acceleration control circuit shown in FIG. 3, the forward acceleration signal C3 to the changeover switch 18-1 of the speed control / position control changeover circuit 32 shown in FIG. The power supply voltage which becomes + Ecc when closed is supplied to the input of the amplifier 36 via the resistor R6. On the other hand, at the same time as the seek start, the target speed data corresponding to one difference seek is given to the target speed generating circuit 24, and a very small signal voltage is obtained through the changeover switch 26-2 which is turned on by the forward command signal C1. The target speed signal E1 is input to the velocity error amplifier 28, the actual speed signal E2 at that time is input from the speed detection circuit 44 at the same time, and the difference signal Δ between the target speed E1 and the actual speed E2 is input from the amplifier 30.
Changeover switch 34 in which E is on by the coarse signal
Input to the amplifier 36 via -1. Therefore, at the input stage of the amplifier 36, the power supply voltage + Ecc input by the control of the reverse acceleration signal C3 is added to the difference signal ΔE, and the control voltage of the addition value (ΔE + Ecc) from the amplifier 36 is added to the power amplifier 38. As a result, the power amplifier 38 causes the acceleration seek current to rise quickly to the voice coil motor 10. Upon receiving this seek current, the head carriage 12 moves the head 40 to the target track. Subsequently, at time t2, when the difference signal ΔE to the comparator 46 shown in FIG. 3 reaches zero voltage, the output of the comparator 46 is inverted to L level, and the end of acceleration is detected. The L level output of the comparator 46 puts the AND gate 50 into the permissible state via the inverter 48, and the C5 signal from the NOR gate 54 becomes the H level and FF58.
Are reset, and as a result, the C6 signal as an output returns to the H level. Therefore, when the forward acceleration signal C3 from the AND gate 60 returns to the H level, the changeover switch 18-1 provided in FIG. 2 is turned off, and the acceleration control by adding the power supply voltage + Ecc is canceled. Therefore, after the time t2, the deceleration current based on the difference signal ΔE generated by the difference between the target speed signal E1 and the actual speed signal E2 flows, and the coarse signal returns to the H level at the seek end at the time t3 to control the speed. And at the same time, the fine signal changes from H level to L level, and the changeover switch 34
When -2 turns on, it switches to position control based on the position signal. Further, at time t4, if the seek start pulse P for the reverse seek is generated based on the access from the host device, the reverse command signal C2 from the MPU22 becomes the H level, and the third seek is performed in the same manner as the forward seek. The reverse acceleration signal C4 from the NAND gate 62 provided in the acceleration control circuit of the figure becomes L level, and the changeover switch 18-2 of FIG. The seek current of the difference seek is satisfactorily raised in the acceleration stage.

【The invention's effect】

As described above, according to the present invention, by forcibly adding a predetermined value for acceleration to the difference signal of the servo loop at the acceleration stage at the time of seek start, the 1-reference seek in which the target speed signal is very small. Even in this case, the seek current can be satisfactorily raised and sufficient acceleration characteristics can be obtained, and the speed can be increased even for seek access with a small difference amount including one difference seek. Further, by detecting the timing when the target speed is reached, that is, the end of acceleration is detected and the acceleration up is turned off, optimal acceleration control can be performed even if the performance of the carriage varies. In addition, the hardware switches the switch to supply and stop the accelerating voltage. Switching can be done on the order of nanoseconds, and it is possible to sufficiently follow one track seek with an extremely short seek time, which corresponds to high track density. it can.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention; FIG. 2 is a block diagram of an embodiment of the present invention; FIG. 3 is a block diagram of an embodiment of an acceleration control circuit of the present invention; Operation Timing Chart of Example; FIG. 5 is an explanatory diagram of a conventional 1-difference seek. In the figure, 10: voice coil motor 12: head carriage 14: acceleration means 16: addition point 18: switching means 18-1, 18-2: changeover switch (for acceleration control), 20: timer means 22: MPU (control logic) ) 24: Target speed generation circuit 26-1, 26-2: Changeover switch (for forward / reverse switching) 28: Velocity error amplifier 30,36: Amplifier 32: Speed control / position control switching circuit 34-1, 34-2 : Changeover switch (for speed control / position control switching) 38: Power amplifier 40: Head 42: Demodulation circuit 44: Speed detection circuit 46: Comparator 48, 56, 64, 66: Inverter 50, 52: AND gate 54: NOR Gate 58: FF

Claims (1)

[Claims] 1. A servo loop for supplying a seek current according to a difference signal (ΔE) between a target speed (E1) and an actual speed (E2) to a voice coil motor to control the speed of a head carriage toward a target track position. In a servo circuit of a disk device equipped with, an acceleration value generating means for generating a predetermined value (Ecc) for acceleration, and a predetermined value for acceleration at an addition point to which a difference signal (ΔE) of the servo loop is input. A switching means for selectively supplying a value (Ecc), an acceleration end detecting means for detecting the end of acceleration when the difference signal becomes zero in the acceleration stage, and the switching means is turned on at the seek start to turn on the addition point. To a predetermined value (Ecc) for acceleration, and when the acceleration end detection means detects the end of acceleration, the switching means is turned off to stop the supply of the predetermined value (Ecc) for acceleration to the addition point. Control means, A disk device provided.