JP3853635B2 - Disk controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a disk control apparatus that performs actuator control of an optical head in order to read a signal from a disk. In particular, the present invention relates to a disk control apparatus that performs actuator control that causes an optical head to be faithfully traced to a track on the disk.
[0002]
[Prior art]
As a conventional disk control apparatus, a disk control apparatus disclosed in Japanese Patent Laid-Open No. 1-303631 is well known. FIG. 13 is a block diagram of a conventional disk control device.
[0003]
In FIG. 13, the position information of the head is output by the position sensor 14 provided in the optical head 16. The speed estimation observer 20 estimates the speed information based on the current information that actually flows through the actuator coil 4 via the drive circuit 23 and the position information.
[0004]
Then, by adding the estimated speed information and the tracking control output using the error signal detected in the tracking error signal generation circuit 17 amplified in the amplification circuit 18, the drive circuit that drives the actuator coil 4 By determining the output current of 23, stable tracking control can be realized without providing a phase compensation circuit.
[0005]
[Problems to be solved by the invention]
In such a disk controller, it is necessary to provide a position sensor 14 or a circuit for detecting the amount of current in order to obtain position information and current information required by the speed estimation observer 20. Therefore, although the control performance of the disk device itself is improved, there is a problem that the power consumption increases due to the cost increase due to the increase in the number of parts, the circuit space expansion, and the circuit scale increase. It was.
[0006]
Further, in the conventional disk control device, since two inputs for normal filter processing and observer processing are separate, two completely independent calculation processes are required.
[0007]
Furthermore, if the position information or current information changes greatly during the transition after starting the observer, such as when the control is pulled in, the estimated value of the observer is greatly shaken, and the time until convergence to a stable state becomes considerably long. There was also a problem.
[0008]
In order to solve the above problems, the present invention can perform stable control even if it is subjected to disc misalignment or vibration without providing a new control circuit, and can quickly converge to a stable state. An object is to provide a disk control device.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a disk control apparatus according to the present invention includes an optical head that irradiates light onto a recording surface of an optical disk to form a light spot and detects the reflected light, and the light spot to the recording surface of the optical disk. A light spot moving unit that moves vertically or in the radial direction thereof, a position error detection circuit that detects a deviation amount from an optimum position based on position information detected by the optical head, and a position error detection circuit PID control circuit that performs phase compensation for the amount of misalignment, and input to the PID control circuit Ru Deviation amount and output from PID control circuit Signal in the state before it is processed in the later stage And both As input An observer that performs an estimation operation, an output from the PID control circuit, an output addition circuit that adds the output from the observer, and a drive circuit that drives the light spot moving unit based on the output from the output addition circuit Features.
[0010]
With this configuration, an observer can be introduced without adding new hardware, and control performance can be greatly improved without increasing costs and power consumption. It should be noted that both the processing in the PID filter and the processing in the observer can be performed in a time division manner using a single filter.
[0011]
The disk control apparatus according to the present invention includes an optical head that irradiates light onto a recording surface of an optical disk to form a light spot and detects reflected light, and the light spot is perpendicular to the recording surface of the optical disk or its radius. A light spot moving unit that moves in the direction, a position error detection circuit that detects a shift amount from an optimum position based on position information detected by the optical head, a shift amount detected by the position error detection circuit, and the like Based on a state determination circuit for determining a control state, a PID control circuit that performs at least phase compensation or the like with respect to a deviation detected by the position error detection circuit, and an input to the PID control circuit. Ru Deviation amount and output from PID control circuit Signal in the state before it is processed in the later stage And both As input Based on the output of the observer that performs the estimation operation, the output from the PID control circuit, the output addition circuit that adds the output from the observer, and the state determination circuit, Start / stop An observer control circuit for controlling the light spot and a drive circuit for driving the light spot moving unit based on the output from the output addition circuit.
[0012]
With this configuration, by providing an integral term in the observer, it is possible to converge stably even when position information or current information changes greatly, such as at the time of pull-in, and match the optimal convergence pattern. Is also possible.
[0013]
Further, the disk control apparatus according to the present invention includes an optical head that irradiates light onto a recording surface of an optical disk to form a light spot and detects reflected light, and the light spot is perpendicular to the recording surface of the optical disk or its radius A light spot moving unit that moves in a direction, a position error detection circuit that detects a shift amount from an optimum position based on position information detected by the optical head, and a shift amount detected by the position error detection circuit A PID control circuit that performs at least phase compensation, a state determination circuit that determines a control state based on an operation time of the PID control circuit, and an input to the PID control circuit. Ru Deviation amount and output from PID control circuit Signal in the state before it is processed in the later stage And both As input Based on the output of the observer that performs the estimation operation, the output from the PID control circuit, the output addition circuit that adds the output from the observer, and the state determination circuit, Start / stop An observer control circuit for controlling the light spot and a drive circuit for driving the light spot moving unit based on the output from the output addition circuit.
[0014]
With this configuration, even by performing time management based on system control commands, it is possible to stably converge against large changes in position information and current information at the time of pull-in, etc., and to match the optimal convergence pattern It becomes.
[0015]
Further, the disk control device according to the present invention has an observer. Start-up It is preferable to further include an integral term preset circuit for setting the integral term of the observer to a predetermined value at the timing to perform. It is because it can be made to converge more effectively.
[0016]
In the disk control device according to the present invention, the integral term preset circuit includes an observer. Start-up It is preferable to update the integral term of the PID filter at the same time. It is because it can be made to converge more effectively.
[0017]
The disk control device according to the present invention includes an observer. Start It is preferable to further include an integral value calculation circuit that calculates an integral term of the observer based on the integral term of the PID filter at the timing and sets the calculated integral term of the observer. This is because the convergence condition can be dynamically updated according to the situation, and the convergence can be performed more effectively.
[0018]
In the disk control device according to the present invention, the integral value calculation circuit includes an observer. Start It is preferable to update the integral term of the PID filter at the same time. It is because it can be made to converge more effectively.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
Hereinafter, a disk controller according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a disk control device according to a first embodiment of the present invention. In FIG. 1, reference numeral 16 denotes an optical head for detecting reflected light from the disk 1. Reference numeral 4 denotes an actuator coil that drives the objective lens when a current flows. However, the objective lens itself is not shown in FIG.
[0020]
A tracking error signal generation circuit 17 generates a tracking error signal from the output of the optical head 2. That is, the tracking error signal generation circuit 17 detects the amount of deviation from the position to be originally tracked.
[0021]
Further, 8 is a PID control circuit used in normal actuator control, and is composed of a low-frequency compensation circuit 8A, a proportional operation circuit 8B, and a phase compensation circuit 8C.
[0022]
Reference numeral 40A denotes a first disturbance estimation observer that estimates the disturbance applied to the actuator using the output of the tracking error signal generation circuit 17 and the output of the PID control circuit 8 as inputs, and FIG. 2 to FIG. Will be described later. Reference numeral 23 denotes a drive circuit that drives the actuator coil 4 by passing a current in accordance with a value obtained by adding the output of the PID control circuit 8 and the output of the first disturbance estimation observer 40A.
[0023]
Next, the first disturbance estimation observer 40A will be described in detail with reference to FIGS. First, FIG. 3 is a configuration diagram of an original model in which a basic type third disturbance estimation observer 40C is incorporated into a PID control loop that controls an actuator suspension.
[0024]
In FIG. 3, 9 is an actuator suspension that supports the objective lens with four wires. Reference numeral 41 denotes a V → F conversion circuit that converts the voltage value (V) output from the PID control circuit 8 into the driving force (F) of the actuator, and 47 denotes the displacement amount (X) of the actuator that is input to the PID control circuit. It is an X → V conversion circuit that converts voltage (V).
[0025]
FIG. 4 is a detailed block diagram of the third disturbance estimation observer 40C. In FIG. 4, Mn is a nominal value of the lens mass supported by the actuator, and s is a Laplace operator. g1 and g2 are constants that determine the characteristics of the disturbance estimation observer. Further, (1 / Mn · 1 / s · 1 / s) in FIG. 4 represents a model of a secondary resonance type actuator.
[0026]
In the prototype model shown in FIG. 3, considering that the block diagram is modified so that the input and output of the PID control circuit 8 become the input of the third disturbance estimation observer 40C, the third disturbance estimation observer 40C is handed. Without addition, it can be easily transformed into the block diagram shown in FIG.
[0027]
That is, as shown in FIG. 5, reference numeral 42 denotes an inverse conversion of the V → F conversion circuit 41, and an F → V conversion circuit that converts the driving force (F) of the actuator into a voltage value (V) output from the PID control circuit 8. It is. Similarly, reference numeral 48 denotes an inverse conversion of the X → V conversion circuit 47, which is a V → X conversion circuit that converts the input voltage (V) of the PID control circuit into the displacement amount (X) of the actuator.
[0028]
Further, if the configuration of the third disturbance estimation observer 40C is changed to the second disturbance estimation observer 40B shown in FIG. 2, the block diagram of FIG. 5 can be transformed into the configuration shown in FIG. . Further, when the V → F conversion circuit 41, the F → V conversion circuit 42, and the V → X conversion circuit 48 connected to the input / output of the second disturbance estimation observer 40B are considered as the first disturbance estimation observer 40A, FIG. As shown, the input and output of the PID control circuit 8 can be used as the input of the first disturbance estimation observer 40A.
[0029]
In the operation of the disk controller configured as described above, both the PID control circuit 8 and the first disturbance estimation observer 40A are operating during tracking control. Then, the first disturbance estimation observer 40A estimates the disturbance applied to the actuator using the input and output of the PID control circuit 8, so that the drive command from the PID control circuit 8 can be accurately corrected, and the disturbance is efficiently processed. Can be suppressed.
[0030]
As described above, according to the first embodiment, it is not necessary to provide a position sensor or a drive current detection circuit by using the input and output of the PID control circuit 8 as the input of the first disturbance estimation observer 40A. . Therefore, an observer can be introduced without adding new hardware or the like, and control performance can be greatly improved without increasing costs and power consumption.
[0031]
Furthermore, the input and output in the process combining the PID control circuit 8 and the first disturbance estimation observer 40A are the same as the input and output in the case of the PID control circuit 8 alone, and these processes are configured by digital filters. In this case, since the time division processing can be performed as a series of filter processing, the circuit configuration itself can be simplified.
[0032]
Although the observer is used only for disturbance estimation in the first embodiment, the observer is not particularly limited to the first embodiment because the observer can perform speed estimation and the like.
[0033]
(Embodiment 2)
A disk control apparatus according to a second embodiment of the present invention will be described below with reference to the drawings. FIG. 7 is a block diagram of the disk control apparatus according to the second embodiment of the present invention. In FIG. 7, the constituent elements other than 43 and 44 are the same constituent elements as those in the first embodiment shown in FIG.
[0034]
In FIG. 7, reference numeral 43 denotes a system controller for controlling the entire system. Reference numeral 44 denotes a state determination circuit that determines the transition time of the tracking pull-in operation based on the operation command output from the system controller 43 and the tracking error signal output from the tracking error signal generation circuit 17.
[0035]
The operation of the disk controller configured as described above will be described with reference to the timing chart of FIG.
[0036]
In FIG. 8, when a system control command for tracking ON is output from the system controller 43 in the tracking OFF state, the PID control circuit 8 creates a control signal from the tracking error signal input at that time and controls the tracking pull-in operation. I do. As a result, the actuator coil 4 is driven by the drive circuit 23, and the amplitude of the tracking error signal that has been output in the form of a sine wave is reduced so that the pull-in operation is performed. Then, the state determination circuit 44 determines from the movement of the system control command and the tracking error signal that the pull-in operation is being performed.
[0037]
When the state determination circuit 44 detects that the tracking error signal is stabilized at the center value and the off-track amount is within the predetermined range and determines that the steady state is entered, the state determination circuit 44 activates the first disturbance estimation observer 40A. Let The first disturbance estimation observer 40A performs disturbance estimation using a tracking error signal near the zero cross point from the start of processing.
[0038]
Since the disordered tracking error signal at the time of tracking pull-in cannot accurately indicate the movement of the actuator 9, using the tracking error signal at the time of tracking pull-in reduces the accuracy of disturbance estimation. End up. However, the tracking error signal in the vicinity of the zero cross point faithfully shows the movement of the actuator 9, and more accurate disturbance estimation processing can be performed.
[0039]
As described above, according to the second embodiment, the state determination circuit 44 determines the control state from the system control command and the tracking error signal, detects the transition from the pull-in operation to the steady state, and sets the disturbance estimation observer A40A. By starting up, the first disturbance estimation observer A40A can perform disturbance estimation with accurate information from the time of startup, and can prevent control from becoming unstable due to disturbance estimation with a large error. .
[0040]
Further, in the second embodiment, the control state is determined from the system control command and the tracking error signal. However, a method realized by time management from the system control command is also possible, and the method is particularly limited to the second embodiment. Is not to be done.
[0041]
Furthermore, in the second embodiment, the operation for controlling the activation of the first disturbance estimation observer 40A in the pull-in operation is described. However, for example, even when tracking control is disturbed due to an external impact or the like in a steady state. Similarly, the first disturbance estimation observer 40A can be controlled. That is, it is also possible to perform control for stopping the first disturbance estimation observer 40A again until the pull-in is completed and the steady state is reached.
[0042]
In the second embodiment, the observer is used for disturbance estimation. However, the observer can be used for speed estimation or the like, and is not particularly limited to the second embodiment.
[0043]
(Embodiment 3)
A disk control apparatus according to a third embodiment of the present invention will be described below with reference to the drawings. FIG. 9 is a configuration diagram of the disk control device according to the third embodiment of the present invention. In FIG. 9, the constituent elements other than 45 are the same constituent elements as those in the first and second embodiments shown in FIGS. Reference numeral 45 denotes an integral value preset circuit that presets the integral term of the first disturbance estimation observer 40A with a predetermined value in accordance with an instruction from the state determination circuit 44.
[0044]
The operation of the disk controller configured as described above will be described with reference to the timing chart of FIG.
[0045]
The tracking pull-in operation from the tracking OFF state is the same as in the second embodiment, and the PID control circuit 8 that receives the system control command output from the system controller 43 creates a control signal using the tracking error signal, A pull-in operation is performed to shift to a steady state.
[0046]
Next, when the state determination circuit 44 determines that the steady state has been reached from the tracking error signal, it gives a command to the integral term preset circuit 45 to preset the integral term of the first disturbance estimation observer 40A with a predetermined value, and at the same time, The disturbance estimation observer 40A is activated. In the first disturbance estimation observer 40A, since the integral term is set to a predetermined value from the start of operation, an accurate disturbance estimation output is ensured from the beginning, and the control disturbance at the start of the first disturbance estimation observer 40A is disturbed. Can be suppressed.
[0047]
As described above, according to the third embodiment, the state determination circuit 44 determines the control state from the system control command and the tracking error signal, detects the transition from the pull-in operation to the steady state, and performs the first disturbance estimation. By presetting and starting the integral term of the observer 40A to a predetermined value, the first disturbance estimation observer 40A can perform disturbance estimation assuming a predetermined estimated DC disturbance from the time of activation, and estimate a disturbance with a large error. This makes it possible to prevent the control from becoming unstable.
[0048]
In the third embodiment, the control state is determined from the system control command and the tracking error signal. However, a method realized by time management from the system control command is also possible, and in particular, the third embodiment. It is not limited to.
[0049]
Furthermore, in the third embodiment, the activation of the first disturbance estimation observer 40A and the operation of controlling the integral term in the pull-in operation are described. However, for example, tracking control is disturbed due to an external impact or the like in a steady state. Also in this case, the first disturbance estimation observer 40A is controlled in the same manner, and the first disturbance estimation observer 40A is stopped until the drawing is completed again and the steady state is reached, and the integral term of the disturbance estimation observer A40A is set to a predetermined value at the time of activation. You can also preset by value.
[0050]
Further, in the third embodiment, only the integral term of the first disturbance estimation observer 40A is preset, but at the same time, a method of presetting the integral term of the low frequency compensation circuit 8A in the PID control circuit 8 is also effective. It is not particularly limited to the third embodiment.
[0051]
Furthermore, although the observer is used for disturbance estimation in the third embodiment, the observer is not particularly limited to the third embodiment because it can also perform speed estimation and the like.
[0052]
(Embodiment 4)
A disk control apparatus according to a fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 11 is a block diagram of a disk control apparatus according to Embodiment 4 of the present invention. In FIG. 11, the components other than 46 are the same as those in the first to third embodiments shown in FIGS. 1, 7, and 9, and the description thereof is omitted. Reference numeral 46 denotes an integral value calculation circuit that calculates and sets the integral term of the first disturbance estimation observer 40A so that the output value to the drive circuit 23 does not deviate from the integral term of the PID control circuit 8 according to an instruction from the state determination circuit 44. .
[0053]
The operation of the disk controller configured as described above will be described with reference to the timing chart of FIG.
[0054]
The tracking pull-in operation from the tracking OFF state is the same as in the second and third embodiments, and the PID control circuit 8 that has received the system control command output from the system controller 43 uses the tracking error signal to control signals. Is created, and a pull-in operation is performed to shift to a steady state.
[0055]
Next, when the state determination circuit 44 determines that the steady state has been reached from the tracking error signal, it gives a command to the integration value calculation circuit 46, and the drive circuit 23 determines the integration value of the low frequency compensation circuit 8A in the PID control circuit 8 at that time. The integral value of the first disturbance estimation observer 40A is calculated and set so that the output value to is not shifted, and the first disturbance estimation observer 40A is activated and the integral term of the low-frequency compensation circuit 8A is reset. In the first disturbance estimation observer 40A, since the integral term is set to the optimum value from the start of operation, an optimum disturbance estimation output is secured from the beginning, and the control disturbance at the start of the first disturbance estimation observer 40A is disturbed. Can be suppressed.
[0056]
As described above, according to the fourth embodiment, the state determination circuit 44 determines the control state from the system control command and the tracking error signal, detects the transition from the pull-in operation to the steady state, and detects the PID control circuit 8. The integral term of the first disturbance estimation observer 40A is calculated and set so that the output value to the drive circuit 23 does not deviate from the integral term of the low-frequency compensation circuit 8A, and the first disturbance estimation observer 40A is activated. The first disturbance estimation observer 40A incorporates the estimated DC disturbance according to the operating state at the time from the start, so that accurate disturbance estimation can be performed under optimum conditions, and control can be performed by disturbance estimation with a large error. It can be prevented from becoming unstable.
[0057]
Further, in the fourth embodiment, the control state is determined from the system control command and the tracking error signal. However, a method realized by time management from the system control command is also possible, and the method is particularly limited to the fourth embodiment. It is not something.
[0058]
Furthermore, in the fourth embodiment, the activation of the first disturbance estimation observer 40A and the operation of controlling the integral term in the pull-in operation are described. For example, tracking control has flowed due to an external impact or the like in a steady state. In this case as well, the first disturbance estimation observer 40A is similarly controlled, and the first disturbance estimation observer 40A is stopped until the re-drawing is completed and the steady state is reached. It is also possible to calculate and set the integral term of one disturbance estimation observer 40A.
[0059]
In the fourth embodiment, the observer is used for disturbance estimation. However, the observer can perform speed estimation and the like, and is not particularly limited to the fourth embodiment.
[0060]
【The invention's effect】
As described above, according to the disk control device of the present invention, by using the input and output of the PID control processing as the input of the observer processing means for estimating disturbance or the like, the observer can be added without adding new hardware. Can be introduced, and the control performance can be greatly improved without increasing costs and power consumption.
[0061]
In addition, when the control state at that time is detected and the observer process is turned ON / OFF, or when the integral term in the observer is preset at the ON time, the position information and current information change greatly at the time of pull-in, etc. However, it is possible to prevent the integral term in the observer from becoming abnormally large and to match the optimum convergence pattern.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a disk control device according to a first embodiment of the present invention;
FIG. 2 is a configuration diagram of a disturbance estimation observer in the disk control device according to the first embodiment of the present invention.
FIG. 3 is a configuration diagram of a prototype model when a disturbance estimation observer is introduced to PID control.
FIG. 4 is a configuration diagram of a disturbance estimation observer in a prototype model when a disturbance estimation observer is introduced in PID control.
FIG. 5 is a configuration diagram of a deformation model when a disturbance estimation observer is introduced to PID control.
FIG. 6 is a configuration diagram of a deformation model when a disturbance estimation observer is introduced to PID control.
FIG. 7 is a configuration diagram of a disk control device according to a second embodiment of the present invention.
FIG. 8 is a timing chart showing various signals at the time of tracking pull-in in the disk control device according to the second embodiment of the present invention;
FIG. 9 is a configuration diagram of a disk control device according to a third embodiment of the present invention.
FIG. 10 is a timing chart showing various signals at the time of tracking pull-in in the disk control device according to the third embodiment of the present invention;
FIG. 11 is a configuration diagram of a disk control device according to a fourth embodiment of the present invention.
FIG. 12 is a timing chart showing various signals at the time of tracking pull-in in the disk control device according to the fourth embodiment of the present invention;
FIG. 13 is a configuration diagram of a conventional disk control device.
[Explanation of symbols]
1 disc
4 Actuator coil
8 PID control circuit
8A low frequency compensation circuit
8B proportional operation circuit
8C phase compensation circuit
9 Actuator suspension
14 Position sensor
16 Optical head
17 Tracking error signal generation circuit
18 Amplifier circuit
20 Speed estimation observer
23 Drive circuit
40A First disturbance estimation observer
40B Second disturbance estimation observer
40C Third disturbance estimation observer
41 V → F conversion
42 F → V conversion
43 System controller
44 State determination circuit
45 Integration term preset circuit
46 Integral value calculation circuit
47 X → V conversion
48 V → X conversion

Claims (8)

An optical head for irradiating the recording surface of the optical disc with light to form a light spot and detecting the reflected light;
A light spot moving section for moving the light spot perpendicularly to the recording surface of the optical disc or in the radial direction thereof;
A position error detection circuit for detecting a deviation amount from an optimum position based on position information detected in the optical head;
A PID control circuit that performs at least phase compensation on the amount of deviation detected by the position error detection circuit;
And observers performed the previous SL shift amount which are input der to the PID control circuit, the estimation operation both signals and in the state before performing the subsequent processing an output signal from the PID control circuit as an input,
An output addition circuit for adding the output from the PID control circuit and the output from the observer;
A disk control device comprising: a drive circuit that drives the light spot moving unit based on an output from the output addition circuit.   2. The disk control device according to claim 1, wherein both processing in the PID control circuit and processing in the observer are performed in a time division manner using a single filter. An optical head for irradiating the recording surface of the optical disc with light to form a light spot and detecting the reflected light;
A light spot moving section for moving the light spot perpendicularly to the recording surface of the optical disc or in the radial direction thereof;
A position error detection circuit for detecting a deviation amount from an optimum position based on position information detected in the optical head;
A state determination circuit for determining a control state based on at least the deviation amount detected by the position error detection circuit;
A PID control circuit that performs at least phase compensation on the amount of deviation detected by the position error detection circuit;
And observers performed the previous SL shift amount which are input der to the PID control circuit, the estimation operation both signals and in the state before performing the subsequent processing an output signal from the PID control circuit as an input,
An output addition circuit for adding the output from the PID control circuit and the output from the observer;
An observer control circuit for controlling start / stop of the observer based on the output of the state determination circuit;
A disk control device comprising: a drive circuit that drives the light spot moving unit based on an output from the output addition circuit. An optical head for irradiating the recording surface of the optical disc with light to form a light spot and detecting the reflected light;
A light spot moving section for moving the light spot perpendicularly to the recording surface of the optical disc or in the radial direction thereof;
A position error detection circuit for detecting a deviation amount from an optimum position based on position information detected in the optical head;
A PID control circuit that performs at least phase compensation on the amount of deviation detected by the position error detection circuit;
A state determination circuit for determining a control state based on an operation time of the PID control circuit;
And observers performed the previous SL shift amount which are input der to the PID control circuit, the estimation operation both signals and in the state before performing the subsequent processing an output signal from the PID control circuit as an input,
An output addition circuit for adding the output from the PID control circuit and the output from the observer;
An observer control circuit for controlling start / stop of the observer based on the output of the state determination circuit;
A disk control device comprising: a drive circuit that drives the light spot moving unit based on an output from the output addition circuit. 5. The disk control device according to claim 3, further comprising an integral term preset circuit that sets an integral term of the observer to a predetermined value at a timing of starting the observer. 6. The disk control device according to claim 5, wherein the integral term preset circuit simultaneously updates the integral term of the PID control circuit at a timing of starting the observer. The integrated value calculation circuit which calculates the integral term of the observer based on the integral term of the PID control circuit at the timing of starting the observer, and sets the calculated integral term of the observer. The disk controller described. 8. The disk control device according to claim 7, wherein the integral value calculation circuit updates the integral term of the PID control circuit at the same time when the observer is activated .

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