JPH04245079A - Control system for positioning head - Google Patents

Abstract

PURPOSE:To obtain an accurate head positioning controller by adding a disturbance cancel loop in a state that a lead/lag filter and a PID control unit remain as they are. CONSTITUTION:A position error detector 2 detects a position error signal (e) from a signal reproduced by a magnetic head 1, and inputs the signal (e) to a lead/lag filter 3. The filter 3 has phase advance/delay elements, and decides a parameter of a filter 6 so as to stabilize a control system by the advance element with an actuator 4 as a model. The output (e) of the detector 2 is twice pseudo-differentiated by a pseudo-differentiator 5, an adder 9 for adding the output of the differentiator 5, the output of a low pass filter 6 and the output of the filter 3, is added, and the output of the adder 9 is input to the actuator 4. The actuator 4 drives the head 1, disturbance is canceled, and the track of the accurate head 1 can be positioned by canceling a disturbance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head positioning control system, and more particularly to a head positioning control system for magnetic disk drives and optical disk drives.

0002

2. Description of the Related Art In magnetic disk drives, efforts are being made to increase their capacity and speed. In order to increase the capacity of disk devices, increasing the TPI by making the track pitch finer and increasing the BPI by increasing the recording density are being carried out in parallel, but in particular, increasing the capacity of disk devices by increasing the TPI. So, with the narrowing of the track pitch,
Progress is being made in increasing the precision of head positioning. Furthermore, increasing capacity and increasing speed are important factors, and high-speed access control systems for this purpose are also being considered.

Now, in high-speed/high-precision head positioning control, as is well known, it is more important to suppress disturbances to the actuator, such as the influence of cables such as FPCs, parameter fluctuations of individual actuators, and the influence of aging. This has become an issue for precise control.

US Pat. No. 4,679 is an example of a conventional head positioning control system that solves these problems.
A control method shown in No. 103 has been proposed. This control method captures all of the above-mentioned disturbances, parameter fluctuations, and secular changes as thrust or torque disturbances, assumes that these disturbances are step disturbances, configures a full-order observer that includes disturbance estimation, and also uses the estimated disturbances. By applying an input to the actuator to cancel the disturbance, the disturbance is suppressed and, as a result, highly accurate positioning is achieved.

[0005] In addition to the above-mentioned control method, a control method that uses a minimum dimension observer instead of a full-order observer has also been proposed.

[0006]

[Problems to be Solved by the Invention] US Pat. No. 4,679 describes an example of the conventional head positioning control method described above.
In the control method shown in No. 103, when the observer's band is made wider than the control system's band, large pulsations and range overs occur in the estimated value, resulting in difficulty in stabilizing the control system. , the band is set sufficiently lower than the control system band. For example, if the control system band is 300Hz, the observer band is 5
It is set as Hz. For this reason, there is a drawback that it takes time until disturbance suppression is performed, and a disturbance suppression method that responds more quickly is desired. Also,
Since disturbance suppression is performed assuming a step-like disturbance,
There is a drawback that head position deviation occurs in response to disturbances other than step-like inputs. Furthermore, in the control method shown in U.S. Pat. No. 4,679,103, conventionally used lead-lag filters and PI
There is also the drawback that a new controller must be designed in place of a controller such as the D control, and the technology of conventional design methods cannot be used.

The present invention was devised in view of the above-mentioned problems, and it is possible to suppress the influence of disturbance by using the conventional controller as is and adding a new disturbance suppression loop. The object of the present invention is to provide a head positioning control system that can achieve a sufficiently high suppression speed.

[0008]

[Means for Solving the Problems] A head positioning control system according to the first invention detects a positional error that is a positional deviation between a recording/reproducing head that records and reproduces data and a disk on which the data is recorded. A head positioning control system comprising a position error detector, a controller that converges the position error according to an output signal of the position error detector, and an actuator unit that receives an output from the controller and drives the recording/reproducing head. , a differentiator that pseudo-twice differentiates the output of the position error detector, a low-pass filter that low-passes the input to the actuator section, and an output of the differentiator, an output of the low-pass filter, and an output of the controller. and an adder that inputs the added output to the actuator section.

The head positioning control system of the second invention includes a position error detector that detects a position error that is a positional deviation between a recording/reproducing head that records and reproduces data and a disk on which the data is recorded; a speed estimator that detects the moving speed of the recording and reproducing head; a controller that converges the position error according to the position error detector output signal and the speed estimator output; and a controller that receives the output of the controller and detects the recording and reproducing head. A head positioning control system comprising an actuator section for driving the head, a differentiator for pseudo-one-time differentiation of the output of the speed estimator, a low-pass filter for low-passing an input to the actuator section, and an output of the differentiator. and an adder that inputs an output obtained by adding the output of the low-pass filter and the output of the controller to the actuator section.

0010

[Operation] By taking the above-mentioned measures, parameter fluctuations and torque disturbances can be suppressed while using conventional control measures such as lead-lag filters and PID controllers, and furthermore, disturbance suppression can be performed at a sufficiently high speed. A realizable head positioning control system can be constructed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the first invention, and FIG. 2 is a block diagram showing an actuator section in the embodiment shown in FIG.

The present embodiment shown in FIG. 1 shows an example of application to a magnetic head positioning feedback control system in a magnetic disk drive using a lead-lag filter 3.

In FIG. 1, the present embodiment includes a position error detector 2 for detecting a position error, which is a positional deviation between a magnetic head 1 for recording and reproducing data and a disk (not shown) on which data is recorded. and a lead-lag filter 3 that converges the position error according to the output signal of the position error detector 2.
The magnetic head 1 receives the output of the lead-lag filter 3.
an actuator section 4 that drives the position error detector 3, a pseudo differentiator 5 that pseudo-twice differentiates the output of the position error detector 3, and a low-pass filter 6 that low-passes the input to the actuator section 4;
The adder 9 is configured to input an output obtained by adding the output of the pseudo differentiator 5, the output of the low-pass filter 6, and the output of the lead-lag filter 3 to the actuator section 4.

A position error detector 2 detects a position error signal e from the signal reproduced by the magnetic head 1, and inputs the position error signal e to a lead-lag filter 3. The lead-lag filter 3 is composed of a phase lead element and a phase lag element, and as is already well known, the parameters of the filter are determined using the actuator section 4 as a model so that the control system is stabilized by the phase lead element.

FIG. 2 is a block diagram showing the actuator section in the embodiment shown in FIG.

In the actuator section 4 shown in FIG.
K1 represents a current amplifier gain, and K2 represents a thrust/acceleration conversion gain. Furthermore, q is a torque (or thrust) disturbance, and u is a current value input to the actuator section 4.

Next, the control operation in this embodiment will be explained using FIGS. 1 and 2.

[0019] In the following, to simplify the explanation, K2 is set to 1.
It will be explained as follows.

Generally, in a voice coil motor for a magnetic disk drive, variations in parameters can be equivalently regarded as torque disturbance. At this time, equation (1) can be derived from FIG.

[0021]

From equation (1), the disturbance q can be induced as follows.

[0023]

Therefore, considering the input gain of the actuator section 4, the input to the actuator section 4 for canceling the disturbance q is as follows.

[0025]

Generally, since there is no differentiator, (3
) In order to realize the first term on the right side of the equation, it is necessary to use pseudo-differentiation.

The pseudo differentiator 5 in FIG. 1 realizes the first term on the right side of equation (3), and as can be seen from equation (3), an appropriate low-pass filter is used so that the relative order is 0 or more. It takes the form of equation (4). Equation (4) shows the case where the relative order is 1. As mentioned above, it is necessary that the relative order is 0 or more.

[0028]

[0029] ω1, ω2, ω3 in equation (4)
There is a method of determining this by taking into account the frequency components of the disturbance, etc., and setting it so that the disturbance can be converged at a sufficient speed.

If we try to execute the second term on the right side of equation (3) as is, an infinite gain will be created. Since this is physically impossible, it must be realized through a low-pass filter. The low-pass filter 6 in FIG. 1 is for realizing the second term on the right side of equation (3). As the low-pass filter 6, it is possible to use one based on ω1, ω2, and ω3 used in equation (4) from the viewpoint of circuit scale.

In this way, by canceling the disturbance, more accurate track positioning control of the magnetic head, ie, track following control, can be achieved.

FIG. 3 is a block diagram showing an embodiment of the second invention.

The present embodiment shown in FIG. 3 shows an example of application to a head positioning feedback control system using the PID controller 7.

In FIG. 3, the present embodiment includes a position error detector 2 for detecting a positional error which is a positional deviation between a recording/reproducing magnetic head 1 for recording and reproducing data and a disk on which data is recorded; a speed estimator 8 that detects the moving speed of the magnetic head 1; and a P that converges the position error according to the output signal of the position error detector 2 and the output of the speed estimator 8.
An ID controller 7 , an actuator section 4 that receives the output of the PID controller 7 and drives the magnetic head 1 , and a speed estimator 8
a pseudo differentiator 5a that pseudo-differentiates the output once, and a low-pass filter 6 that low-passes the input to the actuator section 4.
and an adder 9 which inputs an output obtained by adding the output of the pseudo differentiator 5a, the output of the low-pass filter 6, and the output of the PID controller 7 to the actuator section 4.

Next, the operation of this embodiment will be explained using FIG. 3.

The position error detector 2 detects a position error signal e from the signal reproduced by the magnetic head 1, and inputs the position error signal e to the PID controller 7 and, at the same time, to the speed estimator 8. As is well known, the speed estimator 8, for example,
This is realized using a method such as an electronic tachometer or an observer, and the estimated speed v is input to the PID controller 7. The output of the PID controller 7 is input to the actuator section 4, and as a result, the magnetic head 1 is driven, and the position error is converged. P
The ID controller 7 performs integral and proportional control regarding the position error e, and proportional control regarding the estimated speed v, and as is already well known,
Perform phase control to stabilize the control system.

When the speed estimator 8 is used, the following relationship is derived from FIG. Here again, K2 is assumed to be 1 to simplify the explanation.

[0038] e=-(q+K1・u)/s

(5) From equation (5), the disturbance q can be induced as follows.

q=-s・e−K1・u

(6) Therefore, considering the input gain of the actuator section 4, the input to the actuator section 4 that cancels the disturbance q is as follows.

-q/K1=s・e/K1+u

(7) Regarding the realization of the right side of equation (7), we have already written (3)
It can be realized by a method similar to the method explained in the equation, but in this case, the order of the filter for realizing the pseudo differentiator 5a may be one or more. Furthermore, when the speed estimator 8 is used, it is effective for both speed control and position control.

[0041]

Effects of the Invention As explained above, the present invention uses only a position error signal or a position error signal and an estimated speed signal while leaving the lead-lag filter and PID controller used in the conventional system as they are. By adding a loop for canceling external disturbances, it is possible to realize a highly accurate head positioning control device that suppresses the effects of torque disturbances, parameter fluctuations, and the like.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the first invention.

FIG. 2 is a block diagram showing an actuator section in the embodiment shown in FIG. 1;

FIG. 3 is a block diagram showing an embodiment of the second invention.

[Explanation of symbols]

1 Magnetic head 2 Position error detector 3 Lead-lag filter 4 Actuator section 5, 5a Pseudo differentiator 6 Low-pass filter 7 PID controller 8 Speed estimator 9 Adder e Position error signal K1 Current amplifier gain K2 Thrust/acceleration conversion gain q Torque (or thrust) disturbance u Input to the actuator v Estimated speed signal

Claims (2)

[Claims] 1. A position error detector for detecting a position error that is a positional deviation between a recording/reproducing head for recording and reproducing data and a disk on which the data is recorded; In a head positioning control system comprising a controller that converges the signal, and an actuator unit that receives the output of the controller and drives the recording/reproducing head, the output of the position error detector is
a differentiator that performs differential differentiation, a low-pass filter that low-passes the input to the actuator section, and an addition that inputs an output obtained by adding the output of the differentiator, the output of the low-pass filter, and the output of the controller to the actuator section. A head positioning control system characterized by having a head positioning control system. 2. A position error detector for detecting a positional error that is a positional deviation between a recording/reproducing head for recording and reproducing data and a disk on which the data is recorded, and a speed for detecting a moving speed of the recording/reproducing head. A head comprising an estimator, a controller that converges the position error according to the position error detector output signal and the speed estimator output, and an actuator unit that receives the output of the controller and drives the recording/reproducing head. In the positioning control system, a differentiator that differentiates the output of the speed estimator pseudo-once, a low-pass filter that low-passes the input to the actuator section, and an output of the differentiator, an output of the low-pass filter, and the controller. 1. A head positioning control system comprising: an adder for inputting an output obtained by adding the output to the actuator section.