JPH06251519A - Method for controlling seeking - Google Patents

Abstract

PURPOSE:To optimally control a speed reduction and a stop even when the parameter of a VCM is fluctuated by measuring the parameter, etc., of the voice coil motor(VCM) at the time of the speed acceleration and controlling the speed reduction so as to be made similar to a set speed reduction current model based on the measuring result. CONSTITUTION:When the speeds for an accelarated current transitional area 1 reaching the maximum speed current of a VCM current and a maximum speed acceleration area 2 for which the maximum accelerated current is flown are in an acceleration condition, the current of the VCM is detected and the torque constant number of the VCM, the parameter of the VCM of the change, etc., of a winding wire resistance value and the acceleration of the VCM relating to a current transitional condition are detected. Based on these detection results, control models are set corresponding to a decelerated current transitional area 3, a maximum decelerated area 4, a linear speed control area 5 and a settling control area 6, the deceleration and the stop are carried out so as to come coser to these models, optimum deceleration and top controls are carried out even when the parameter and a power voltage are fluctuated and a highspeed and stable seeking operation is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method in which a voice coil motor (hereinafter referred to as VCM) is used to move a controlled object to perform positioning, and more particularly to a seek operation for moving between tracks in a disk device. The present invention relates to a suitable seek control method.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram of a positioning servo device of a magnetic disk device. Positioning servo device 1
Has two modes of operation. One is a tracking mode for following a specific track, and the other is a seek mode for moving between tracks. In the tracking mode, the analog switch 3 is switched to the phase compensation circuit 4 by the tracking / seek switching signal 2a from the CPU 2.
The output of is switched to the side that selects and the position control loop is configured. Further, in the seek mode, the output of the speed error amplifier 5 is switched to the side to be selected to form a speed feedback control loop.

A seek mode for moving between tracks will be described. The CPU 2, which has received a command from the external device, calculates the distance between the current track and the target track, outputs the target speed data 2b corresponding to the distance to the D / A converter 6, and the tracking / seek switching signal 2
a is output to switch the analog switch 3 to the side for selecting the output of the speed error amplifier 5.

As shown in FIG. 2 (c), since the moving speed of the head in the stopped state is zero, the current speed signal 7a outputted from the position-speed conversion circuit 7 and the D / A converter 6 are outputted. A large error occurs with the output target speed signal 6a. Therefore, it is amplified by the speed error amplifier 5,
The control amount 8a supplied to the VCM drive circuit 8 via the analog switch 3 becomes the maximum acceleration control amount as shown in FIG. 2 (a), and the current 9a flowing through the VCM 9 is affected by the coil inductance, as shown in FIG. As shown in), it gradually increases, and the current speed also increases accordingly.

The movement of the head attached to the VCM via the carriage is detected by the position detection circuit 10 by a position signal 1
The current speed signal 7a is obtained by the position-speed conversion circuit 7. Further, the track passing pulse generation circuit 11 generates a track passing pulse 11a every time one track passes, and the counter 12 counts the number of passing tracks from the start of movement. The CPU 2 reads the passing track number 12a, which is a counter value, and generates target speed data 2b according to the remaining track number. Generally, the target speed calculation function for deceleration control with uniform acceleration is
It is given by the number 1.

[0006]

[Equation 1]

As shown in FIG. 2C, the current speed signal 7
When a reaches the target speed signal 6a, the control amount shown in FIG. 2A becomes zero, and when the current speed signal 7a becomes larger than the target speed signal 6a, the control amount is generated in the deceleration direction, and the target speed curve becomes Along the target track. When the speed is sufficiently reduced to approach the target track, the CPU 2 switches the analog switch 3 to the position control system and shifts to the tracking mode.

However, there is a problem that a sufficient deceleration current is not generated when shifting from the acceleration state to the deceleration state.
As shown in FIG. 2C, the current speed overshoots the target speed. If this becomes large, the error between the current speed and the target speed at the point of approaching the target track and switching to the position control becomes large, and after switching to the position control, the target track cannot be stopped, causing a malfunction.

Therefore, Japanese Patent Application Laid-Open No. 54-12082 proposes a technique for improving the followability to the target speed signal by feedforward control. Also,
Even if the control amount starts decelerating, the coil current of the VCM does not immediately follow, and the time until the decelerating current follows the control amount depends on the resistance of the VCM coil (which changes with temperature) and the influence of the power supply voltage. receive. On the other hand,
Japanese Patent No. 28238 proposes a technique of detecting a temperature or a power supply voltage and changing a target speed curve so that the target speed curve can be stably controlled.

[0010]

The feedforward control is to switch the control amount to the deceleration control in consideration of the tracking delay with respect to the target speed of the VCM in advance, and to change the parameter of the VCM (VCM torque constant, coil winding resistance, Although it is set within a range in which stable control is possible even if there is a power supply voltage fluctuation), optimum control is not performed with respect to parameter fluctuation. Further, in order to detect the temperature and the power supply voltage and change the target speed curve, a temperature sensor and a power supply voltage detection circuit are required, which causes a problem of increasing the number of parts.

The present invention has been made to solve the above problems, and seek control that maximizes the ability of the controlled object and stably controls it against the parameter variation factor of the controlled object VCM. The purpose is to provide a method.

[0012]

In order to solve the above problems, a seek control method according to a first aspect of the present invention is directed to a seek operation for moving a controlled object such as a head using a voice coil motor to perform positioning. It is characterized in that the parameters of the motor are measured while in an acceleration state, and deceleration control is performed so as to approach a preset deceleration current model based on the measurement result.

A control method according to a second aspect of the present invention is characterized by predicting a current transient state during deceleration from a current transient state during acceleration of the voice coil motor.

According to a third aspect of the present invention, the acceleration during acceleration of the voice coil motor is multiplied by a predetermined coefficient to predict the deceleration acceleration, and the acceleration during acceleration and the acceleration during deceleration are calculated based on the acceleration during acceleration. It is characterized in that the coefficient, which is a ratio between the acceleration and the acceleration during deceleration, is determined.

[0015]

In the seek control method according to the first aspect, the parameters of the voice coil motor are measured in the acceleration state,
Since the deceleration control is performed based on the measurement results so that it approaches the preset deceleration current model, even if the voice coil motor parameter changes, the optimum deceleration / stop control can be performed according to the changed parameter. It enables high-speed and stable seek operation.

A seek control method according to a second aspect of the present invention predicts the transient state of the current during deceleration from the transient state of the current during acceleration of the voice coil motor, and controls the operation during deceleration.

A seek control method according to a third aspect of the present invention considers a torque constant variation due to the position of the voice coil motor and a torque constant difference due to the current direction of the voice coil motor from the acceleration during acceleration of the voice coil motor, and considers the torque constant difference during deceleration. Predict acceleration and perform seek control.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The seek control method according to the present invention measures the parameters of the VCM to be controlled when the vehicle is in the accelerating state, and performs deceleration control so as to approach a preset deceleration current model based on the measurement result.

If the speed of the head to be controlled is zero when the control amount for maximum acceleration and maximum deceleration as shown in FIG. 3 is output and the target track is reached, control with the shortest seek time is possible. However, in this control method, only the timing of the deceleration start point indicated by the symbol C in FIG. 3 can be controlled only, and it is difficult to realize such control with respect to the fluctuation of the controlled object.

Therefore, although maximum acceleration and maximum deceleration are performed,
In the vicinity of the target track, linear speed control is performed,
It is desirable to shorten the time for performing linear velocity control as much as possible within the range where stable control is possible. Therefore, FIG.
Assuming the control model shown in (1), control is performed to approximate it.

FIG. 4 shows the waveform of each part during seek by the seek method according to the present invention. FIG. 4 (a) shows the control amount,
(B) shows the VCM current, and (c) shows the VCM speed. Figure 4
With respect to the control amount of (a), the VCM current is roughly divided into six regions as shown in FIG. 4 (b). Area 1: Acceleration current transition area (area until VCM current reaches maximum acceleration current) Area 2: Maximum acceleration area (area where maximum acceleration current flows in VCM) Area 3: Deceleration current transition area (maximum VCM current) Area from acceleration current to maximum deceleration current) Area 4: Maximum deceleration area (area where maximum deceleration current flows in VCM) Area 5: Linear speed control area (VCM speed control with control current less than maximum deceleration current) Area 6): Settling control area (area until stop on the target track by position feedback control)

Therefore, the VCM parameters are measured in the acceleration regions of the regions 1 and 2, and the deceleration start point C, the linear velocity control start point D, and the target velocity in the region 5 are determined.

First, a simple example will be shown for determining the parameter expressing the behavior of the VCM current. In the region 1 shown in FIG. 4B, when the control amount shown in FIG. 4A gives the maximum acceleration control amount to the VCM drive circuit 8, the VCM drive circuit 8 supplies a constant voltage limited by the power supply voltage to the VCM coil. It is applied to both ends (see the equivalent circuit shown in FIG. 5A). VCM
Assuming that the current flowing through the coil causes a first-order lag due to the influence of the inductance L (it is assumed that there is no influence due to the back electromotive force for ease of explanation), FIG.
The waveform is as shown in (b), and the VCM current i (t) is expressed by Equation 2.

[0024]

[Equation 2]

When this equation 2 is represented by a discrete expression, it can be represented as equation 3 when the sample number is n and the sampling period is Δt as shown in FIG. 5B.

[0026]

[Equation 3]

If A and B shown in the equation 3 are determined,
Power supply voltage, VCM coil inductance L, VCM
By the influence of the coil resistance R and the internal resistance of the VCM drive circuit 7, it is possible to predict how the VCM current will behave in the deceleration current region of the region 3 of FIG. 4B.
Although various methods of determining A and B are conceivable, they can be easily obtained by measuring in-2, in-1, in and performing the calculation represented by Formula 4.

[0028]

[Equation 4]

The measurement of in-2, in-1, and in can be easily realized by A / D converting the VCM current. Further, the parameters relating to the torque constant and inertia of the VCM can be expressed as an acceleration per unit current, and as a simple example, the viscous resistance of the VCM bearing, the force of the flexible wire acting on the VCM, and the force of the air flow due to the disk rotation are used. Ignoring this, in the area 2 of FIG. 4B, the constant current driving VCM is performing uniform acceleration motion, so as shown in FIG. 6, the track numbers arranged at equal intervals Tp are Tn, Assuming Tn + 1 and Tn + 2, the time t1 required to pass between Tn and Tn + 1
Then, from the time t2 required to pass between Tn + 1 and Tn + 2, the maximum acceleration αmax of the VCM in the region 2 of FIG.

[0030]

[Equation 5]

Times t1 and t2 required to pass
Can be easily realized by the means for measuring the interval between the track passing pulses 11a in FIG. The value obtained by dividing this αmax by the current value in the constant current drive state is the acceleration α per unit current.
Becomes

As described above, the VCM in the area 1 of FIG.
Determine the parameters A and B expressing the behavior of the current,
After that, when the VCM current reaches the maximum acceleration current, FIG.
An example of determining the maximum acceleration αmax and the unit current acceleration α in the region 2 of (b) has been shown.

Next, after the maximum acceleration αmax and the unit current acceleration α are determined in the maximum acceleration region 2 of FIG. 4B, the linear velocity control region 5 when controlled by the control model shown in FIG. 4B is passed. An example of predicting the distance X5 moving in and the speed V4 entering the linear speed control area 5 from the maximum deceleration area 4 will be shown.

Although various control models can be considered, as a simple control model, as shown in FIG. 4B, after entering the settling control area 6 from the area 5, the distance to the target track is X6, and the entry speed is To V5, area 5
The time for performing the linear velocity control of is the time t5, and the control current for performing the linear velocity control in the region 5 is -1 / 2Imax, which has the opposite sign of the maximum acceleration current Imax and the absolute value of 1/2. Note that the control model is not limited to this as long as it is within a range in which stable control is possible. X5 and V4 in the case of controlling with this control model can be obtained as Expression 6.

[0035]

[Equation 6]

Although the maximum acceleration αmax previously obtained is used here, when an acceleration current and a deceleration current whose absolute values are equal to each other are applied to the VCM, the torque constant changes depending on the VCM position and the torque constant difference depending on the VCM current direction. Therefore, the absolute values of acceleration and deceleration cannot be said to be equal.
Therefore, if αmax is multiplied by a coefficient in consideration of the torque constant variation factor and used as αdmax, the prediction accuracy of X5 and V4 is further improved.

As described above, in the area 2 of FIG. 4B, the distance X5 traveled while passing through the linear speed control area 5 and the speed V4 at which the maximum deceleration area 4 enters the linear speed control area 5 are predicted. An example was given.

Next, an embodiment for determining the optimum deceleration start point C after determining X5 and V4 in the area 2 of FIG. 4B will be described. Now, after determining X5 and V4 in the area 2 of FIG. 4B, the moving distance X2 from the start of movement to the present time and the current speed V2 can be known by the method described in the description of the related art. It is assumed that the current time is the time of the deceleration start point C, and the predicted calculation of the position and speed at the time of entering the linear speed control region 5 after passing through the regions 3 and 4 from the present time is performed.

First, assuming that the current time is the time of the deceleration start point C, the time t3 required to enter the area 3 and pass through the area 3 is the maximum VCM current as shown in FIG. 4 (b). It is a time from the acceleration current Imax to −Imax having opposite signs and equal absolute values. A simple method for obtaining t3 is to use the parameters A and B expressing the behavior of the VCM current previously obtained by ignoring the back electromotive force, perform the repetitive calculation shown in Formula 7, and set n to −Imax ≧ In. If found, the current will reach -Imax after n sample times.

[0040]

[Equation 7]

Therefore, the time t3 required to pass through the region 3 is given by the equation 8.

[0042]

[Equation 8]

Further, the distance X3 moved while passing through the area 3
And the velocity V3 after passing through the region 3 is given by the equation 9.

[0044]

[Equation 9]

Here, V / R and τ are obtained by the equation 10.

[0046]

[Equation 10]

Speed V3 after passing through the area 3 obtained here
Then, after entering the area 4 and n samples after entering the area 4, the moving distance X4 (n) and the moving speed V4 (n) are
It is expressed by the recurrence formula of Expression 11.

[0048]

[Equation 11]

This iterative calculation is performed by increasing n until the relation of equation 12 is established.

[0050]

[Equation 12]

V4 (n) when the relational expression of Expression 12 is established
If the value of is smaller than the previously obtained V4, the maximum acceleration of the region 2 is still continued. That is, it is understood that the maximum deceleration point C is not yet reached. Also, X4 (1), V4 (1), X4
During the repeated calculation of (2), V4 (2) ... V4 (n)
If ≦ V4, maximum acceleration is continued.

In this way, if the above calculation is performed while continuing the maximum acceleration in the region 2, V4 will eventually be obtained.
(N) becomes equal to or larger than V4. At this time, the control amount is the maximum deceleration control amount − as shown in FIG.
Set to Umax and start deceleration control. That is, this time point is the optimum deceleration start point C that approaches the current model.

Further, X3, V3, X4 (n), V4
Also regarding αmax and α used in the calculation formula of (n), the torque constant variation and VCM depending on the position of VCM described above
Is a coefficient for correcting the torque constant difference depending on the current direction of
The prediction accuracy is improved by multiplying x and α.
In the above, one example of determining the optimum deceleration start point C in the area 2 of FIG. 4B has been shown.

Next, the control amount is switched to the maximum deceleration, and after entering the region 3, it waits until the VCM current reaches the maximum deceleration current. Then, the VCM current reaches the maximum deceleration current, and the area 4
An example in which the linear speed control start point D shown in FIG. First, the distance XT from the current position to the entry into the settling control area 6 is expressed by Expression 13.

[0055]

[Equation 13]

In the linear velocity control area 5, the target velocity VT at the distance XT is given by the equation 14 since the target velocity VT at the distance XT is controlled by the uniform acceleration of -1 / 2αmax from the control model.

[0057]

[Equation 14]

When the speed control is performed only by the proportional control,
The velocity feedback gain is Kv, and the controlled variable u is
It becomes 5.

[0059]

[Equation 15]

As shown in FIG. 4 (a), the control amount u in the region 5 is considered to be 1/2 of the maximum deceleration control amount-Umax as a control model. It is the starting point D of the linear speed control.

[0061]

[Equation 16]

Although the case where the speed control is performed only by the proportional control is shown, the integral control may be added. Also, as for αmax used during the calculation of the target speed VT, αmax may be multiplied by a coefficient for correcting the torque constant variation depending on the position of the VCM and the torque constant difference depending on the current direction of the VCM described above. Regarding this coefficient, by obtaining the maximum deceleration acceleration by the same method as the above-mentioned maximum acceleration αmax during acceleration while passing through the region 4,
It is also possible to update the coefficient relating to the torque constant difference depending on the VCM current direction. The example of determining the linear speed control start point D in the region 4 has been described above.

Next, at the linear speed control start point D, after entering the area 5, speed feedback control is performed with the target speed being VT given by the above-mentioned equation 14, as described in the prior art. When XT = 0, the settling control region 6 is entered, and the position feedback control is performed to stop on the target track. The example of the seek control according to the present invention has been described above.

Further, in the above-mentioned embodiment, the control model shown in FIG. 4 has been described, but when the seek distance becomes long, the control model shown in FIG. 7 can be applied. In the above-described embodiment, while determining the optimum deceleration start point C while passing through the maximum acceleration region 2, when the current speed is equal to or exceeds the predetermined maximum speed Vmax, the control amount is set to 0 and the deceleration is performed. All can be handled in the same manner except that the VCM current initial value in the current transient region 3 is started from zero.

When the seek distance is short, the maximum value Umax of the controlled variable is previously set as in the control model shown in FIG.
Can be set lower and treated in the same way.

[0066]

As described above, the seek control method according to the present invention measures the parameters of the voice coil motor at the time of acceleration and controls at the time of deceleration / stop so as to approach the preset current model based on the measurement result. Therefore, the variation of the torque constant of each VCM, the fluctuation of the torque constant depending on the position, the difference of the torque constant depending on the current direction, the V
Stable and optimum seek control can be performed against fluctuations in CM coil winding resistance due to temperature and fluctuations in power supply voltage. In addition,
By predicting the transient state of the current during deceleration from the transient state of the current during acceleration of the voice coil motor, it is possible to seek a stable and optimal seek against the above parameter fluctuations without changing the structure of the conventional servo control device. You can control. In addition, the prediction accuracy can be improved by determining the coefficient that is the ratio of the acceleration during acceleration and the acceleration during deceleration based on the acceleration during acceleration and the acceleration during deceleration.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a head positioning servo device in a magnetic disk device.

FIG. 2 is a waveform diagram of each part during seek in the conventional control method.

[Figure 3] Waveform diagram of each part during seek by maximum acceleration and maximum deceleration

FIG. 4 is a waveform diagram of each part during seek by the seek method according to the present invention.

FIG. 5: Transient region waveform of VCM current acceleration current

FIG. 6 is an explanatory diagram for calculating VCM acceleration.

FIG. 7: Waveform diagram of each part during seek when the seek distance is long

FIG. 8 is a waveform diagram of each part during seek when the seek distance is short.

[Explanation of symbols]

1 ... Positioning servo device, 2 ... CPU, 4 ... Phase compensation circuit, 7 ... Position-speed conversion circuit, 8 ... VCM drive circuit, 9
... Voice coil motor (VCM), 10 ... Position detecting circuit, 11 ... Track passing pulse generating circuit.

Claims (3)

[Claims] 1. In a seek operation in which a voice coil motor is used to move a controlled object such as a head to perform positioning, the parameters of the voice coil motor are measured when in an accelerating state, and based on the measurement results. A seek control method, wherein deceleration control is performed so as to approach a preset deceleration current model. 2. The seek control method according to claim 1, wherein the transient state of the current during deceleration is predicted from the transient state of the current during acceleration of the voice coil motor. 3. The acceleration during acceleration of the voice coil motor is multiplied by a predetermined coefficient to predict deceleration acceleration, and the acceleration during acceleration and the acceleration during deceleration are based on the acceleration during acceleration and the acceleration during deceleration. 2. The seek control method according to claim 1, wherein the coefficient, which is a ratio with