JPH0828081B2 - Positioning control device for magnetic head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head positioning control device in a magnetic disk device.

(Prior Art) Magnetic head positioning control of a magnetic disk device, in particular,
In the track following control, a feedback control system for making the magnetic head follow the target track position based on the position error signal between the current position of the magnetic head and the target data track position obtained from the position error detecting means.
Phase lead and phase delay compensating elements are used as compensating elements, and the control band of the position tracking control system of the magnetic head is about
400Hz is realized. In this control system, the magnetic head drive motor itself has two integral elements, so a sufficient low-frequency feedback gain is secured, and it is a so-called type 2 servo system for the target input. The control system has a zero deviation. However, it has been pointed out that it is 0 type against force disturbance and weak against external force. On the other hand, in recent years, a position error signal is passed through an integrator and a coefficient unit to add respective outputs, and the addition result and a negative feedback signal of a motor speed signal obtained from an electronic tachometer or the like are used as a motor drive amplifier. The method of using the so-called PID control method of directly inputting into has become popular. This method uses one integrator of the motor itself and one integrator of the PID controller to maintain the type 2 property for the target input, and one PID controller for the force disturbance. This is a method in which Type 1 characteristics can be secured by the effect of the integrator, and is a control method having an effect of suppressing force disturbance.

(Problems to be Solved by the Invention) Although the PID control method described above has type 1 characteristics with respect to disturbance, it is required for the position tracking control system of the magnetic head to have a further disturbance suppression effect. Has been done. As a method for improving the effect of suppressing the force disturbance, it is conceivable to increase the shape of the servo system from the disturbance such as type 2 and type 3. As a method for this, it is easy to imagine that an integrating element is inserted in series with the output of the position error detector, but this method can increase the number of shapes from disturbance, but on the other hand, the phase margin of the control system is sufficient. However, there is a problem that the overshoot becomes large when the position control system starts to work for track access or the like.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic head positioning control device in which the influence of a force disturbance in a magnetic disk device is reduced.

(Means for Solving the Problem) According to the present invention, a position error detecting means for obtaining a position error signal indicating a difference between a target position to be followed by a magnetic head and the magnetic head position, a motor for driving the magnetic head, and the above In a magnetic disk device comprising a motor drive section for applying a current to a motor and a speed detecting means for detecting a moving speed of the motor, a band of a position tracking control system of the magnetic head is received by receiving an output of the position error detecting means. Positioning control device for magnetic head comprising first compensating means for determining, and second compensating means for giving a command value to the motor drive unit by receiving the output of the first compensating means and the output of the speed detecting means. Wherein the first compensating means integrates the output of the position error detecting means, a first integrator multiplying the output of the position error detecting means by a constant, and the first integrator. Of a second coefficient unit for multiplying the output of the integrator by a constant and a first adder for adding the outputs of the first and second coefficient units, the second compensating means of the first adder A subtractor for taking the difference between the output and the output of the speed detector, a second integrator for integrating the subtractor output, a third coefficient unit for multiplying the output of the second integrator by a constant, and the subtraction A magnetic head positioning control device, comprising: a fourth coefficient unit for multiplying the output of the container by a constant, and a second adder for adding the outputs of the third and fourth coefficient units. A first compensating unit integrates the output of the position error detecting unit, a first integrator that multiplies the output of the position error detecting unit by a constant, and a first integrator that multiplies the output of the first integrator by a constant. A second coefficient unit and a third coefficient unit for multiplying the output of the speed detector by a constant and the first, second and third coefficient units. A second adder for adding the outputs of the number adders, wherein the second compensating means obtains the difference between the output of the first adder and the output of the speed detector, and the subtractor. A second integrator that integrates outputs, a fourth coefficient unit that multiplies the output of the second integrator by a constant, a fifth coefficient unit that multiplies the output of the subtractor by a constant, and the fourth and fifth A magnetic head positioning control device comprising a second adder for adding the outputs of the coefficient units.

(Operation) The magnetic head positioning control device of the present invention has a velocity feedback control system of type 1 both in the magnetic head position tracking control system from the speed command and the force disturbance, and further, the magnetic head position tracking control system is integral-compensated. With this configuration, it is possible to realize a type 2 position tracking control system from the target input and the force disturbance while ensuring the phase margin, and to control the magnetic head that can sufficiently reduce the influence of the force disturbance.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings. However, in the following description, the signal name and the signal value are represented by the same symbol.

FIG. 1 is a block diagram showing the configuration of a magnetic head positioning control device of a magnetic disk device according to an embodiment of the present invention.

The output of the speed detector 7 which detects the speed of the motor is fed back to the second compensating means and the second compensating means. The output a of the first compensating means is input, and further, the speed detecting means 7
Of the second compensating means 4 which uses the output of the above as a feedback input, and the motor driving part 5 which receives the output of the second compensating means 4 and generates a drive current to the motor 6, the motor 6 and the speed detecting means 7.
The closed loop consisting of the motor 6 having the output a of the first compensating means 3 as a target value and the output of the speed detecting means 7 as a controlled variable.
The speed feedback control system of is constructed. The first compensating means 3 which receives the output of the position error detecting means 2 and the output of the position error detecting means 2 and the output of the speed detecting means 7 inputs the output a of the first compensating means, and further the speed detecting means. A second compensating means 4 which uses the output of 7 as a feedback input, and a motor drive section 5 which receives the output of the second compensating means 4 and generates a drive current to the motor 6, a motor comprising a motor 6 and a speed detecting means 7. The speed feedback control system of 6 and the integral of the speed of the motor 6 are connected in series to form a controller in the position control system of the motor 6, which is a new control target.

The signal x reproduced by the magnetic head 1 becomes a position word difference signal e indicating the difference between the current position of the magnetic head 1 and the target data track position by the position error detector 2. The first compensating means 3 includes the output e of the position error detector 2 and the velocity detector 7
And outputs the speed command a, which is the target speed of the motor 6 for driving the magnetic head, to the second compensator 4. As described above, the motor 6 receives the output a of the first compensating means, the second compensating means 4 which receives the output of the speed detecting means 7 as a feedback input, and the output of the second compensating means 4 to the motor 6. In the closed loop composed of the motor drive unit 5 for generating the drive current, the motor 6, and the speed detecting means 7, the motor 6 having the output a of the first compensating means 3 as the target value and the output of the speed detecting means 7 as the controlled variable Since the above speed feedback control system is constructed, the output of the first compensating means becomes the target speed of the speed feedback control system. FIG. 3 is a diagram showing an example of the configuration of the first compensating means 3 in FIG. 1 using the Laplace transform operator s, coefficient units K ₃ , K ₄ and adder. It is a PI controller for position. Further, FIG. 4 shows an example of the configuration of the first compensating means 3 in FIG. 1, the Laplace transform operator s, coefficient units K ₃ ′ and K ₄ ′,
It illustrates using K ₅ and an adder. This compensator is a composite system of PI compensation relating to the position of the magnetic head 1 and velocity feedback compensation, and when K ₅ is zero,
It becomes the PI controller shown in FIG. The second compensating means 4 receives the speed command a and the output v of the speed detecting means 7 and outputs a motor drive signal b to the motor drive section 5. FIG. 2 is a diagram showing a configuration example of the second compensating means 4 in FIG. 1 by using an operator s of Laplace transform, coefficient units K ₁ , K ₂ , an adder and a subtractor. This compensator is a PI compensator for the speed of the motor 6 that drives the magnetic head 1. The motor drive unit 5 receives the output b of the second compensating means 4, sends a current i to the motor 6 in proportion to the output b, drives the magnetic head 1, and compensates the output v of the speed detecting means 7 for the second compensation. It is fed back to the means to control the speed of the motor 6.

FIG. 5 is a graph showing the dynamics of the motor 6, the first compensating means 3 and the second compensating means 4, which are Laplace transform operators s fourth.
It is the figure shown by the structure of a figure, the structure of FIG. 2, and the structure of FIG.

The characteristics from the force disturbance q and the characteristics from the target input r will be described below with reference to FIG. Since the structure of the first compensating means shown in FIG. 3 can be realized by setting K ₅ to zero in FIG. ₅ , the case of using the first compensating means having the structure of FIG. 4 will be described here. .

In FIG. 5, the transfer function W _ry (s) from the target value r to the magnetic head position x and the transfer function W _qy (s) from the force disturbance q to the magnetic head position x are expressed by equations (1) and (2). Like Here, K _F and M represent the force constant of the motor and the weight of the movable part, respectively.

_{d 3 = K F · K 1} · (1-K 5) / M d 2 = K F · {K 1 · K 3 + K 2 · (1-K 5)} / M d 1 = K F · (K 1・ K ₄ + K ₂ · K ₃ / M d ₀ = K _F · K ₂ · K ₄ / M n ₂ = K _F · K ₁ · K ₃ / M n ₂ = 1 / M Equation (1), (2) From the transfer function indicated by, it is understood that a control system of type 2 is constructed from the target value input and a type 2 control system is constructed from the force disturbance.

To explain how to determine K _{1 to} K ₅ , K _F = 1 and M = 1 and K ₅
Consider the case of = 0.

If the servo band of the position tracking control system is ω ₀ , K ₁ , K ₂
Is determined so that the servo band of the speed system is 10ω ₀ or more. For example, when ω ₀ = 2, K ₁ and K ₂ are the servo bands 20 of the speed system, and K ₁ = 20 and K ₂ = 100, respectively.

By doing this, the transfer function of the inner loop with respect to velocity can be approximated to 1, since its servo band is sufficiently wide with respect to that of position. Therefore, the position control system parameters K ₃ , K ₄
Is 1 / s, and PI is such that the servo band is 2.
Design the controller. As a result, K ₃ = 2 and K ₄ = 1. At this time, equations (1) and (2) are as follows.

At this time, the phase margin is about 70 degrees, and the maximum value of the gain of the equation (4) is about -40 dB at 1.5ω ₀ . That is, the effect of the force disturbance can be suppressed to 1/100 or less while securing the phase margin.

As can be seen from the equation (1), K ₅ is effective when the highest-order coefficient of the numerator of the equation (1) is adjusted and the zero point of the equation (1) is moved. A finer positioning control system can be realized by moving the zero point from K _{1 to} K ₅ using K ₁ or K ₃ and determining the denominator with the remaining four parameters.

(Effects of the Invention) As described above, according to the present invention, the velocity control loop is formed in the position control loop by integral compensation,
Further, by integrating and compensating the position control system, a sufficient phase margin can be secured in the position control system, and at the same time, a position control system of the magnetic head can be constructed which reduces the influence of force disturbance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a configuration example of a second compensating means in the embodiment of FIG. 1, and FIG. 1 is a diagram showing a configuration example of a first compensating means in the embodiment of FIG. 1, FIG. 4 is a diagram showing another configuration example of the first compensating means in the embodiment of FIG. 1, and FIG. 5 is a magnetic head positioning. It is a figure showing the example of composition of a control system using operator s of Laplace transformation. In the figure, 1 ... Magnetic head, 2 ... Position error detecting means, 3 ... First compensating means, 4 ... Second compensating means, 5 ... Motor drive section, 6 motor, 7 ... ... speed detecting means, a ...... first compensation means output, b ...... second compensation means output, e ...... position error signal, i ...... motor drive _{current, K 1, K 2, K} 3, K 3 ′, K
₄ , K ₄ ′, K ₅ ... constant, q ... force disturbance, r ... target data track position, s ... Laplace transformation operator, v ... motor speed, x ... magnetic head position .

Claims (2)

[Claims] 1. A position error detection means for obtaining a position error signal indicating a difference between a target position to be followed by a magnetic head and the magnetic head position, a motor for driving the magnetic head, and a motor drive for applying a current to the motor. And a magnetic disk device including a speed detecting means for detecting the moving speed of the motor, a first integrator for integrating the output of the position error detecting means, and a constant multiple of the output of the position error detecting means. First compensating means comprising a first coefficient unit, a second coefficient unit for multiplying the output of the first integrator by a constant, and a first adder for adding the outputs of the first and second coefficient units. A subtractor that takes the difference between the output of the first adder and the output of the speed detector, a second integrator that integrates the output of the subtractor, and a constant multiple of the output of the second integrator. The third coefficient unit and the subtractor output And a second adder for adding the outputs of the third and fourth coefficient units, wherein the output of the second compensator is the motor driving unit. To a magnetic head positioning control device. 2. A position error detection means for obtaining a position error signal indicating a difference between a target position to be followed by a magnetic head and the position of the magnetic head, a motor for driving the magnetic head, and a motor drive for supplying a current to the motor. And a magnetic disk device including a speed detecting means for detecting the moving speed of the motor, a first integrator for integrating the output of the position error detecting means, and a constant multiple of the output of the position error detecting means. A first coefficient unit, a second coefficient unit that multiplies the output of the first integrator by a constant, a third coefficient unit that multiplies the output of the speed detector by a constant, and the first, second, and third coefficient units. Compensating means for adding the outputs of the first and second adders, a subtractor for taking the difference between the output of the first adder and the output of the speed detector, and the output of the subtractor are integrated. A second integrator to
A fourth coefficient unit for multiplying the output of the second integrator by a constant, a fifth coefficient unit for multiplying the output of the subtractor by a constant, and a second addition for adding the outputs of the fourth and fifth coefficient units. A magnetic head positioning control device, comprising: a second compensating means including a container, and the output of the second compensating means being an output to the motor drive section.