WO2016067741A1

WO2016067741A1 - Servo control device and servo control method

Info

Publication number: WO2016067741A1
Application number: PCT/JP2015/074693
Authority: WO
Inventors: 佑介金武; 伸夫竹下
Original assignee: 三菱電機株式会社
Priority date: 2014-10-29
Filing date: 2015-08-31
Publication date: 2016-05-06
Also published as: JPWO2016067741A1

Abstract

Provided are a servo control device and method that can ensure control stability while allowing use of a high frequency bandwidth as a control bandwidth. In the present invention, servo control devices (10, 11) can implement the servo control method, and are each provided with: a signal detection unit (50) that generates a control target position signal indicating the position of a movably supported control target (20); and a central control unit (60) that generates, on the basis of a control target position signal SIG0 generated by the signal detection unit (50), a control signal SIG2 for controlling a drive mechanism (30) that drives the control target. The central control unit (60) includes a gain increase filter (62) that has a gain frequency characteristic which locally increases the amplitude gain at a predetermined specific frequency, for an open loop characteristic of an open loop that includes the signal detection unit (50) and the drive mechanism (30).

Description

Servo control device and servo control method

The present invention relates to a servo control device having a drive mechanism control unit that controls a drive mechanism that drives a controlled object, and a servo control method.

In general, in a control system including a drive mechanism control unit that controls a drive mechanism that drives a control target based on a signal indicating the position of the control target, feedback control that causes the position of the control target to follow a target position is used. . Such feedback control requires high-precision control of the position of the controlled object and stable control (control stability) so that the drive mechanism does not oscillate. Generally, in order to realize highly accurate control, it is necessary to use a high frequency band as a control band that is a frequency band used by the control system. However, in a control system that uses a high frequency band as a control band, the gain margin becomes small and the stability of control is impaired. This is because a phase delay occurs due to a calculation delay of a control filter included in a control system using a high frequency band as a control band. Further, when the drive mechanism has a resonance point (resonance frequency), a phase delay occurs at the resonance frequency. Thus, generally, in feedback control, the accuracy of control and the stability of control are in a trade-off relationship. Therefore, generally, in order to improve the stability of control, a low frequency band is used as a control band.

As a countermeasure, Patent Document 1 proposes a positioning control device in which a filter having an anti-resonance point near the resonance frequency of the drive mechanism and having a resonance point near the anti-resonance frequency is added. Thereby, the resonance point in the open loop characteristic is moved to the high frequency side, and the control band is increased without impairing the stability of the control.

Further, Patent Document 2 proposes a control circuit that includes a notch filter that attenuates the amplitude of a specific frequency component and adjusts the frequency at which the gain (gain) of the notch filter is minimized to the resonance frequency of the drive mechanism. . Thereby, only a component near the resonance frequency in the open loop characteristic is greatly attenuated to ensure a large gain margin.

JP 2001-195850 A (Claim 2, paragraph 0015, FIGS. 2 to 4) Japanese Patent Laid-Open No. 9-44863 (paragraphs 0012 and 0022, FIG. 1, FIG. 5 and FIG. 7)

However, the resonance frequency of the drive mechanism varies for each drive mechanism. Further, the resonance frequency of the drive mechanism varies depending on the temperature of the drive mechanism. In the control device of Patent Literature 1, a state in which the resonance frequency of the drive mechanism matches the frequency of the resonance point of the added filter may occur due to variations in the resonance frequency of each drive mechanism. When such a state occurs, there is a problem that the amplitude at the resonance point in the open loop characteristic is further increased, the gain margin is decreased, and the stability of the control is impaired.

Also, in the control circuit of Patent Document 2, a phase lag occurs below the frequency at which the gain of the notch filter is minimized, so there is a problem that the phase lag in the open loop characteristic increases and the control stability is impaired.

Therefore, the present invention has been made to solve the above-described problems of the prior art, and in the present invention, a gain increasing filter for locally increasing an amplitude gain at a specific frequency in an open loop characteristic is added. By doing so, the phase delay is improved in the high frequency band, so that the high frequency band can be used as the control band used for servo control. For this reason, an object is to realize highly accurate control.

A servo control device according to the present invention is a servo control device that controls a drive mechanism that drives a control target, and a signal detection unit that generates a control target position signal that is a signal indicating the position of the control target that is movably supported. And a central control unit that generates a control signal for controlling the drive mechanism based on the control target position signal generated by the signal detection unit, and the central control unit includes the signal detection unit And an open loop characteristic of the open loop including the drive mechanism, including a gain increasing filter having a gain frequency characteristic for locally increasing an amplitude gain at a predetermined specific frequency.

The servo control method according to the present invention is a servo control method for controlling a drive mechanism that drives a control object, and drives the control object that is movably supported based on a control signal supplied from a central control unit. An open loop characteristic of an open loop including a step, a step of generating a control target position signal that is a signal indicating the position of the control target by a signal detection unit, and the central control unit includes the drive mechanism and the signal detection unit In the above, the control signal is obtained from the control target position signal generated by the signal detector using a gain increasing filter having a gain frequency characteristic that locally increases the gain of the amplitude at a predetermined specific frequency. And generating.

The present invention can provide a servo control device and a servo control method capable of using a higher frequency band than the conventional control band while ensuring the stability of control.

It is a block diagram which shows roughly the structure of the servo control apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows schematically the other structure of the servo control apparatus which concerns on Embodiment 1 of this invention. FIG. 3 is a block diagram illustrating components of a main part of the servo control device according to the first embodiment. FIG. 6 is a block diagram showing other components of the main part of the servo control device according to the first embodiment. It is a figure which shows an example of the transfer function of the gain increase filter of the servo control apparatus which concerns on Embodiment 1. FIG. (A) And (b) is a figure which shows the frequency characteristic of the gain increase filter of the servo control apparatus which concerns on Embodiment 1. FIG. (A) And (b) is a figure which shows the open loop characteristic of the servo control apparatus which concerns on Embodiment 1. FIG. FIG. 3 is a block diagram illustrating an example of a configuration of a digital filter as a gain increasing filter of the servo control device according to the first embodiment. It is a block diagram which shows roughly the structure of the optical disk apparatus which is a servo control apparatus concerning Embodiment 2 of this invention. It is a block diagram which shows roughly the structure of the magnetic disc apparatus which is a servo control apparatus concerning Embodiment 3 of this invention. It is a block diagram which shows roughly the structure of the motor control apparatus which is a servo control apparatus which concerns on Embodiment 4 of this invention.

In the present invention, by adding a gain increasing filter that locally increases the gain of the amplitude at a specific frequency in the open loop characteristic, the phase delay is improved, the gain margin is secured, and the control stability is maintained. can do.

Further, in the present invention, a frequency that suppresses an increase in gain near the resonance frequency can be selected as the specific frequency of the gain increase filter. For this reason, control stability can be maintained even when the drive mechanism has a resonance point and there is a variation in resonance frequency for each drive mechanism.

Embodiment 1 FIG.
FIG. 1 is a block diagram schematically showing a configuration of a servo control device 10 according to the first embodiment of the present invention. The servo control device 10 is a device that can perform the servo control method according to the first embodiment.

As shown in FIG. 1, the servo control device 10 according to the first embodiment includes a signal detection unit 50 and a central control unit 60. The servo control device 10 can include a sample SA, a control target 20, a drive mechanism 30, or a drive mechanism control unit 40.

The signal detection unit 50 generates a control target position signal SIG0 that is a signal indicating the position of the control target 20 that is movably supported. The central control unit 60 generates a control signal SIG2 for controlling the drive mechanism 30 that drives the control target 20, based on the control target position signal SIG0 generated by the signal detection unit 50.

The central control unit 60 is a gain increase having a gain frequency characteristic for locally increasing the gain of the amplitude at a predetermined specific frequency in the open loop characteristics of the open loop including the signal detection unit 50 and the drive mechanism 30. A filter (62 shown in FIGS. 3 and 4 described later) is included.

Further, in the servo control method according to the first embodiment, the drive mechanism control unit 40 controls the drive mechanism 30 that drives the control target 20 that is movably supported based on the control signal SIG <b> 2 supplied from the central control unit 60. An open loop in which the signal detection unit 50 includes a control target position signal SIG0 that is a signal indicating the position of the control target 20, and the central control unit 60 includes the signal detection unit 50 and the drive mechanism 30. And generating a control signal SIG2 for controlling the drive mechanism 30 from the control target position signal SIG0 generated by the signal detector 50. In the step of generating the control signal SIG2, the central control unit 60 gains a gain increase filter (62 shown in FIGS. 3 and 4 described later) having a gain frequency characteristic that locally increases the gain of the amplitude at a specific frequency. ) Is used.

The control object 20 is arranged at a position facing the sample SA, for example. The control target 20 is, for example, a device or a member for scanning the sample SA in three dimensions, and is supported by the main body of the servo control device 10 so as to be movable. Here, “scanning” refers to detecting the state of a desired position (detected position SA0) of the sample SA while moving or detecting information recorded at this position. The sample SA has, for example, a thin plate shape. In addition, “three-dimensional” can be expressed in the x-axis direction and the y-axis direction (that is, the xy orthogonal coordinate system) parallel to the detection surface (the lower surface of the sample SA in FIG. 1) including the detection position of the sample SA. xy plane) and a z-axis direction perpendicular to the surface to be detected of the sample SA (that is, a direction orthogonal to the xy plane that can be expressed in the xy orthogonal coordinate system).

When the control target 20 is an objective lens of an optical pickup, the optical pickup irradiates the sample SA with a light beam, receives reflected light (optical signal) from the sample SA, and receives the reflected light received. The electric signal (detection signal) corresponding to the signal is generated, and the generated electric signal is supplied to the signal detection unit 50. Details in the case where the control target 20 is an objective lens of an optical pickup will be described in the second embodiment.

The drive mechanism 30 is, for example, a resonance type actuator that realizes highly efficient operation by being driven at a resonance point (resonance frequency) of the drive mechanism 30. The drive mechanism 30 moves the control object 20 that scans the sample SA in three dimensions according to the relative positional relationship between the sample SA and the control object 20. However, the drive mechanism 30 may be an actuator having a configuration having no resonance point.

The drive mechanism control unit 40 gives a command signal corresponding to the control signal SIG <b> 2 given from the central control unit 60 to the drive mechanism 30 to control the operation of the drive mechanism 30. The drive mechanism control unit 40 may be a part of the central control unit 60.

The central control unit 60 generates a control signal SIG2 for controlling the drive mechanism 30 based on the control target position signal SIG0 given from the signal detection unit 50. The central control unit 60 outputs a control signal SIG2 to the drive mechanism control unit 40.

The signal detection unit 50 receives the electrical signal (detection signal) output from the control target 20, and gives a control target position signal SIG0, which is a signal indicating the position of the control target 20, to the central control unit 60. The control target position signal SIG0 is a signal indicating the relative positional relationship between the sample SA and the control target 20, for example.

The configuration of the servo control device 10 is not limited to the example of FIG. This will be described later with reference to FIG. Moreover, in FIG. 1, the example of control in case the controlled object 20 is displaced to the x-axis direction, the y-axis direction, and the z-axis direction is shown. However, the servo control device 10 to which the present invention is applied is not limited to such a form. The present invention is also applicable, for example, when a certain axis is used as a reference axis and the control object 20 is displaced in a direction (a certain angle direction) that forms a predetermined angle with respect to the reference axis.

FIG. 2 is a block diagram schematically showing another configuration of the servo control device according to the first embodiment of the present invention. The servo control device 11 is a device that can perform the servo control method according to the first embodiment.

FIG. 2 is different from FIG. 1 in that the controlled object 20, the drive mechanism 30, and the drive mechanism control unit 40 are not included in the servo control device 11. That is, the servo control device 11 according to the first embodiment may include the signal detection unit 50 and the central control unit 60. In FIG. 2, the sample SA is not included in the servo control device 11, but may be included.

1 shows a configuration in which the control target 20 (lens) and the drive mechanism 30 (voice coil motor) cannot operate independently, like an optical pickup. Therefore, for example, the control target 20, the drive mechanism 30, the drive mechanism control unit 40, and the sample SA (optical disk) are included in the servo control device 10.

On the other hand, the configuration example of the servo control device 10 shown in FIG. 2 shows a case where the drive mechanism 30 is a motor or the like, for example. For example, since the motor can be driven by open loop control, it is omitted from the components of the servo control device 10 in FIG.

The control object 20, the drive mechanism 30, the drive mechanism control unit 40, the signal detection unit 50, the central control unit 60, and the sample SA in FIG. 2 are the same as those shown in FIG.

FIG. 3 is a block diagram showing components of a main part of the servo control device 10 according to the first embodiment. That is, FIG. 2 is a block diagram showing components of a main part of the servo control device 10 in FIG. As shown in FIG. 3, the central control unit 60 includes, for example, a control filter 61 and a gain increase filter 62. Further, in FIG. 3, the configuration corresponding to the drive mechanism 30 and the drive mechanism control unit 40 in FIG. 1 is shown by one block (30, 40).

3, the signal detection unit 50 supplies the control filter 61 with a control target position signal SIG0 indicating the position of the control target 20.

The control filter 61 includes a filter for realizing feedback control as a constituent element. The control filter 61 includes, for example, a PID (Proportional Integral Derivative) control filter.

In the servo control device 10 according to the first embodiment, the control filter 61 generates the control signal SIG1 from the control target position signal SIG0. Then, the control filter 61 supplies the control signal SIG1 to the gain increase filter 62.

The gain increase filter 62 is a filter that locally increases an amplitude gain (dB) at a specific frequency. The gain increasing filter 62 has a function of locally increasing the amplitude at a specific frequency with respect to the input control signal SIG1. That is, the gain increase filter 62 generates the control signal SIG2 in which the amplitude of the input control signal SIG1 is locally increased. The gain increasing filter 62 outputs this control signal SIG2.

The drive mechanism 30 is controlled by the drive mechanism control unit 40. The drive mechanism 30 drives the controlled object 20 in accordance with the control signal SIG2 output from the gain increasing filter 62.

The control object 20 outputs a signal indicating the position of the control object 20, for example. The signal detection unit 50 receives a difference signal (deviation) between the signal indicating the position of the control target output from the control target 20 and the target position signal of the control target 20. The signal detection unit 50 generates a control target position signal SIG0 corresponding to the difference signal.

Note that the signal detection unit 50 may perform the following processing. The signal detection unit 50 receives a signal indicating the position of the control target 20 output from the control target 20 and a target position signal of the control target 20. The signal detection unit 50 calculates these difference signals (deviations). The signal detection unit 50 generates a control target position signal SIG0 corresponding to the calculated difference signal.

The central control unit 60 performs feedback control for causing the control target 20 to follow the target position based on the control target position signal SIG0.

3, the gain increase filter 62 is inserted between the control filter 61 and the control target 20. In other words, the gain increasing filter 62 is arranged at the subsequent stage of the control filter 61. However, the gain increasing filter 62 may be inserted between the signal detection unit 50 and the control filter 61. In other words, the gain increasing filter 62 may be disposed in front of the control filter 61.

The gain increasing filter 62 may include an analog filter using a resistor, a capacitor, a coil, an operational amplifier, or the like as a constituent element. Further, the gain increasing filter 62 may include a digital filter such as a general-purpose microcomputer or DSP (Digital Signal Processing) as a constituent element.

FIG. 4 is a block diagram showing the main components of the servo control device 11 according to the first embodiment, which is different from FIG. That is, FIG. 3 is a block diagram showing components of a main part of the servo control device 11 in FIG. 4 is different from FIG. 3 in that the control target 20, the drive mechanism 30, and the drive mechanism control unit 40 are not included in the servo control device 11. That is, the servo control device 11 according to the first embodiment may include the signal detection unit 50 and the central control unit 60.

The components in FIG. 4 are the same as those shown in FIG.

An example of the gain increase filter 62 including an analog filter as a component will be described. FIG. 5 is a diagram illustrating an example in which a peaking filter that is an analog filter is employed as the gain increasing filter 62 of the servo control device 10 and the servo control device 11 according to the first embodiment.

FIG. 5 shows an example of a transfer function of a peaking filter as the gain increasing filter 62. The gain increasing filter 62 is a filter other than the peaking filter as long as the gain (gain) of the amplitude in the specific frequency range is locally large and the gain of the amplitude in the specific frequency range can be locally increased. It may be.

The peaking filter as the gain increasing filter 62 can include a common biquadratic filter as a constituent element. The “biquadratic filter” is a filter whose denominator and numerator of the transfer function are both quadratic, and the transfer function is described by the following equation (1), for example.

Here, s is a complex variable. ω ₀ represents the peak frequency PKf ₀ [Hz] expressed in radians [rad / sec]. The peak frequency PKf ₀ [Hz] is a frequency at which the gain of the amplitude of the gain increasing filter 62 is maximized. A ₀ is a constant that determines the gain of the amplitude of the gain increasing filter 62. Q ₀ is a constant that determines the peak width of the signal output from the gain increasing filter 62.

6 (a) and 6 (b) are diagrams showing gain frequency characteristics and phase frequency characteristics of the gain increasing filter 62 according to the first embodiment. The gain increasing filter 62 shown in FIGS. 6A and 6B is a peaking filter having a transfer characteristic indicated by the transfer function shown in Expression (1).

FIG. 6A shows the characteristic (gain frequency characteristic) of the gain [dB] of the amplitude with respect to the frequency [Hz]. FIG. 6B shows the characteristic (phase frequency characteristic) of the phase [degree] with respect to the frequency [Hz].

6A and 6B, ω ₀ indicating the peak frequency PKf ₀ [Hz] in radians [rad / sec], a constant A _0, and a constant Q ₀ are set to the following values: is doing.
ω ₀ = 753982.24 [rad / sec]
(That is, PKf ₀ = 1.2 × 10 ⁵ [Hz])
A ₀ = 2.5
Q ₀ = 1.413

6A, the horizontal axis represents the frequency [Hz] of the signal output from the gain increasing filter 62, and the vertical axis represents the gain [dB] of the amplitude of the peaking filter as the gain increasing filter 62. 6B, the horizontal axis indicates the frequency [Hz] of the signal output from the peaking filter as the gain increase filter 62, and the vertical axis indicates the phase of the signal output from the peaking filter as the gain increase filter 62. Degree].

In FIG. 6A, the amplitude gain is calculated by the following equation (2).
Gain of amplitude [dB] = 20 · log ₁₀ X Formula (2)

Here, X is a real value. For example, X = (output amplitude) / (input amplitude). That is, the amplitude gain [dB] in FIG. 6A is a value obtained by converting the real value X to a decibel value. Gain increase filter 62 shown in FIG. 6 (a), it is desirable to have a peak frequency PKF _0. The peak frequency PKf ₀ is a frequency at which the gain of the amplitude becomes maximum (maximum) in the gain frequency characteristic. Further, the gain-increasing filter 62 shown in FIG. 6 (a), having a peak frequency PKF ₀ (i.e., PKF ₀ in FIG. 6 (a)) to gradually gain distribution gain of the amplitude decreases with increasing distance from.

Further, the gain increasing filter 62 has a phase frequency characteristic having a frequency domain FD ₁ for advancing the phase in a frequency range below a specific frequency and a frequency domain FD ₂ for delaying the phase in a frequency range exceeding the specific frequency. Can do.

As can be understood from FIG. 6B, in the peaking filter as the gain increasing filter 62, the phase advances at a frequency lower than the peak frequency PKf ₀ that is a specific frequency (the phase is larger than 0 degree). Further, the peaking filter as a gain-increasing filter 62, (less the phase of 0 degree) phase is delayed at frequencies above the peak frequency PKF ₀ a specific frequency.

A method for determining the peak frequency PKf ₀ in the peaking filter as the gain increasing filter 62 will be described with reference to FIGS. 7 (a) and 7 (b).

FIGS. 7A and 7B are diagrams showing the open loop characteristics of the servo control device 10 and the servo control device 11 according to the first embodiment. In FIG. 7A, the horizontal axis indicates the frequency [Hz] of the signal output from the gain increase filter 62, and the vertical axis indicates the gain [dB] of the amplitude of the gain increase filter 62. In FIG. 7B, the horizontal axis indicates the frequency [Hz] of the signal output from the gain increase filter 62, and the vertical axis indicates the phase [degree] of the signal output from the gain increase filter 62. The horizontal and vertical axes in FIGS. 7A and 7B are the same as those described in FIGS. 6A and 6B, respectively.

7A, a gain frequency characteristic curve 70a indicates an amplitude gain [dB] as an open loop characteristic of the comparative example. In FIG. 7B, a phase frequency characteristic curve 71a indicates the phase [degree] as the open loop characteristic of the comparative example.

The open loop characteristic of the comparative example does not include a gain increase filter (gain increase filter 62 shown in FIG. 2). The open loop of the comparative example includes the signal detection unit 50, the control filter 61, and the drive mechanism 30 of FIGS. 3 and 4, and does not include the gain increase filter 62. That is, here, the comparative example refers to general feedback control in which the control target 20 is controlled by the control filter 61. The open loop of the comparative example is represented by, for example, the product of the transfer function of the signal detection unit 50, the transfer function of the control filter 61, and the transfer function of the drive mechanism 30 shown in FIGS.

The control filter 61 includes a phase compensation filter as a component for realizing feedback control. The control filter 61 has a phase compensation function in order to perform feedback control.

The gain frequency characteristic curve 70a and the phase frequency characteristic curve 71a are indicated by broken lines, respectively.

7A, a gain frequency characteristic curve 70b shows the gain [dB] of the amplitude as the open loop characteristic in the first embodiment. In FIG. 7B, a phase frequency characteristic curve 71b indicates the phase [degree] as the open loop characteristic in the first embodiment. The open loop characteristic in the first embodiment includes a gain increasing filter. This gain increasing filter is the gain increasing filter 62 shown in FIGS. 3 and 4, and has the characteristics shown in FIGS. 6 (a) and 6 (b). The open loop of the first embodiment includes a signal detection unit 50, a central control unit 60, and a drive mechanism 30. The gain frequency characteristic curve 70b and the phase frequency characteristic curve 71b are each indicated by a solid line.

7A and 7B, GAf ₀ [Hz] indicates a frequency at which the amplitude gain is 0 [dB] in the comparative example and the first embodiment. THf ₀ [Hz] indicates a frequency at which the phase is −180 [degrees] in the comparative example. THf ₁ [Hz] indicates a frequency at which the phase is −180 [degrees] in the first embodiment. REf ₀ [Hz] indicates the resonance frequency (resonance point) of the drive mechanism 30 in the comparative example and the first embodiment.

Here, a method of determining the peak frequency PKf ₀ [Hz] in FIGS. 6A and 6B will be described.

In FIG. 7B, in order to change the phase frequency characteristic curve 71a of the comparative example to the phase frequency characteristic curve 71b of the first embodiment, the peak is set so as to satisfy both the following first condition and second condition. It is desirable to determine the frequency PKf ₀ [Hz]. That is, the phase near the frequency GAf ₀ [Hz] at which the amplitude gain becomes 0 [dB] can be advanced by the first condition and the second condition.
First condition: PKf ₀ ≧ GAf ₀
Second condition: PKf ₀ ≧ THf ₀

The first condition is a condition that the peak frequency PKf ₀ is equal to or higher than the frequency GAf ₀ [Hz]. In the open loop characteristics of the open loop including the signal detection unit 50 and the drive mechanism 30, the frequency GAf ₀ [Hz] is a frequency at which the amplitude gain is 0 [dB]. A broken line in FIG. 7A indicates a position where the gain is 0 [dB].

The second condition is a condition that the peak frequency PKf ₀ is equal to or higher than the frequency THf ₀ [Hz]. In the open loop characteristics of the open loop including the signal detection unit 50 and the drive mechanism 30, the frequency THf ₀ [Hz] is a frequency at which the phase of the broken line in FIG. 7B is −180 [degrees].

In the comparative example (broken line in FIG. 7B), the frequency THf ₀ [Hz] is a frequency at which the phase is −180 [degrees]. In the open loop characteristics (Embodiment 1) of the open loop including the signal detection unit 50 and the drive mechanism 30, the frequency THf ₁ [Hz] indicates a position where the phase is −180 [degrees].

When the drive mechanism 30 has a resonance point, the gain margin decreases when the gain of the amplitude at the resonance frequency REf ₀ [Hz] is increased. For this reason, it is desirable to determine the peak frequency PKf ₀ [Hz] so as to satisfy the following third condition.
Third condition: PKf ₀ > REf ₀

The third condition is a condition that the peak frequency PKf ₀ is a frequency greater than the resonance frequency REf ₀ [Hz]. The drive mechanism 30 has a resonance point. The resonance frequency REf ₀ [Hz] is the frequency at the resonance point of the drive mechanism 30.

Note that when the drive mechanism 30 does not have a resonance point, the first condition and the second condition may be satisfied.

In the case of FIGS. 6A, 6B, 7A, and 7B, the following conditions are satisfied. The frequency GAf ₀ = 4.1 × 10 ³ [Hz]. The frequency GAf ₀ is a frequency at which the amplitude gain is 0 [dB]. The frequency THf ₀ = 1.0 × 10 ⁴ [Hz]. The frequency THf ₀ is a frequency at which the phase is −180 [degrees] in the comparative example. The resonance frequency REf ₀ = 2.0 × 10 ⁴ [Hz]. The resonance frequency REf ₀ is the resonance frequency of the drive mechanism 30. The peak frequency PKf ₀ = 1.2 × 10 ⁵ [Hz]. The first condition, the second condition, and the third condition are all satisfied.

As a result, as shown in FIG. 7A, the gain increase filter 62 can reduce the change in amplitude at the resonance point (resonance frequency REf ₀ ). For example, in FIG. 7A, the gain of the amplitude at the resonance point is not changed by the gain increasing filter 62.

Further, as shown in FIG. 7B, the gain increase filter 62 can increase the phase advance amount of the frequency GAf ₀ [Hz]. The frequency GAf ₀ [Hz] is a frequency at which the amplitude gain becomes 0 [dB]. For example, the region 72 is a region in which the phase delay is improved by the gain increasing filter 62. In FIG. 7 (b), the region 72 is the frequency region from the frequency GAF ₀ to frequency THf _1.

Next, an example of the gain increasing filter 62 including a digital filter as a component will be described.

FIG. 8 is a block diagram illustrating an example of a calculation block when the digital filter is a constituent element in the gain increasing filter 62 of the servo control device 10 according to the first embodiment.

In FIG. 8, 80a, 80b, 80c, 80d, 80e, and 80f are multipliers each having a predetermined multiplication coefficient. That is, the gain increasing filter 62 shown in FIG. 6 includes multipliers 80a, 80b, 80c, 80d, 80e, and 80f.

Reference numerals 80g and 80h denote delay elements (z ⁻¹ ) as delay elements of one sample time. That is, the gain increasing filter 62 shown in FIG. 6 includes delay devices 80g and 80h. The delay units 80g and 80h include, for example, a shift register as a constituent element.

80i, 80j, 80k, and 80l are calculation blocks that function as adders. That is, the gain increasing filter 62 shown in FIG. 6 includes adders 80i, 80j, 80k, and 80l.

In the control filter 61 and the gain increasing filter 62, the characteristics of an arbitrary biquadratic filter can be realized by using a digital filter as a constituent element. As a result, a filter having the same gain frequency characteristic and phase frequency characteristic as the gain increasing filter 62 shown in FIGS. 6A and 6B can be realized.

As described above, in the servo control device 10, the servo control device 11, and the servo control method according to the first embodiment, the gain increase filter 62 is added to improve the phase delay and secure the gain margin. , Control stability can be maintained. The gain increasing filter 62 locally increases the gain of the amplitude at a specific frequency in the open loop characteristic. Here, the specific frequency is, for example, the peak frequency PKf ₀ [Hz] in FIGS. 6A and 6B. Further, the improvement of the phase delay is, for example, an improvement of the phase delay in the region 72 in FIG.

Further, in the servo control device 10, the servo control device 11, and the servo control method according to the first embodiment, the phase delay is improved in a high frequency band. For this reason, a high frequency band can be used as a control band used for servo control. Here, the high frequency band is a region that is larger than the frequency THf ₀ [Hz] and lower than the frequency THf ₁ [Hz], for example, as a region 72 in FIG. 7B. For this reason, more accurate control can be realized than in the case of the comparative example in which a low frequency band is used as the control band. Here, the low frequency band is, for example, a region below the frequency THf ₀ [Hz] in FIG.

Here, the frequency THf ₁ [Hz] is a frequency at which the phase delay becomes −180 [degrees] in the servo control device 10 and the servo control device 11 according to the first embodiment. At frequencies below the frequency THf ₁ [Hz], the phase delay is smaller than −180 [degrees].

Furthermore, in the servo control device 10, the servo control device 11, and the servo control method according to the first embodiment, a frequency that does not increase or decrease the gain at the resonance frequency can be selected as the specific frequency. That is, the servo control device 10, the servo control device 11, and the servo control method can suppress fluctuations in gain at the resonance frequency. Here, the specific frequency is, for example, the peak frequency PKf ₀ [Hz] in FIGS. 6A and 6B. The resonance frequency is, for example, the resonance frequency REf ₀ [Hz] in FIG.

For this reason, even when the drive mechanism 30 has a resonance point, even when there is a variation in the resonance frequency REf ₀ [Hz] for each drive mechanism 30 as in the product variation, the stability of the control is maintained. Can do.

Embodiment 2. FIG.
In the first embodiment, the general servo control device 10 and the servo control device 11 have been described. The servo control device 90 according to the second embodiment is an optical disc device in which the control target 20 is an objective lens of an optical pickup.

FIG. 9 is a block diagram schematically showing the configuration of an optical disc apparatus that is the servo control apparatus 90 according to the second embodiment.

As shown in FIG. 9, the servo control device 90 according to the second embodiment includes a spindle motor 91, a spindle control unit 92, a thread motor 93, a thread control unit 94, a laser control unit 95, and an optical pickup. 100, an actuator control unit 110, a signal detection unit 120, and a central control unit 130. The spindle motor 91 rotates the optical disc OD. The actuator control unit 110 corresponds to the drive mechanism control unit 40 shown in the first embodiment.

Optical disc OD includes a read-only disc, a write once disc, and a rewritable disc. A read-only disc can only be played. The write-once disc can be played back and additionally recorded, and cannot be rewritten. The rewritable disc can be reproduced, additionally recorded, and rewritten. The optical disc OD is, for example, a BD (Blu-ray Disc) (registered trademark), a DVD (Digital Versatile Disc), a CD (Compact Disc), or the like. The optical disc OD corresponds to the sample SA shown in the first embodiment.

Spindle motor 91 rotates optical disc OD. The rotation method of the spindle motor 91 includes a CAV (Constant Angular Velocity) method with a constant angular velocity or a CLV (Constant Linear Velocity) method with a constant linear velocity. The spindle controller 92 controls the spindle motor 91.

The thread motor 93 moves the optical pickup 100 in the tracking direction of the optical disc OD. The tracking direction is the radial direction of the optical disc OD. In FIG. 9, the tracking direction is the x-axis direction.

The thread control unit 94 controls the thread motor 93.

The laser control unit 95 controls the laser light source 102.

The optical pickup 100 includes a laser light source 102, a beam splitter 103, an objective lens 104, a light detection unit 105, a lens unit 101, an elastic support member, and an actuator 106. The beam splitter 103 reflects the laser light from the laser light source 102. The objective lens 104 focuses the laser beam reflected by the beam splitter 103 on the information recording surface of the optical disc OD. The objective lens 104 corresponds to the control target 20 shown in the first embodiment. The light detection unit 105 includes a light receiving element that receives reflected light reflected by the optical disc OD and transmitted through the objective lens 104 and the beam splitter 103 and converts it into an electrical signal. The lens unit 101 is a unit including these components 102 to 105. The elastic support member 107 supports the objective lens 104 in the lens unit 101 so as to be movable. The actuator 106 is a drive mechanism that moves the objective lens 104 in the tracking direction and the focusing direction (z-axis direction) against the elastic force of the elastic support member 107. The actuator 106 corresponds to the drive mechanism 30 shown in the first embodiment.

The actuator control unit 110 as a drive mechanism control unit controls the actuator 106 in response to a command signal from the central control unit 130. The actuator control unit 110 corresponds to the drive mechanism control unit 40 shown in the first embodiment. The central control unit 130 corresponds to the central control unit 60 shown in the first embodiment. The actuator control unit 110 may be a part of the central control unit 130.

The signal detection unit 120 inputs an electrical signal from the light detection unit 105. That is, the signal detection unit 120 receives an electrical signal from the light detection unit 105. Then, the signal detection unit 120 outputs the generated signal. The signal detection unit 120 corresponds to the signal detection unit 50 shown in the first embodiment.

The signal generated by the signal detection unit 120 is an objective lens position signal, a focus error signal, a tracking error signal, or the like. The objective lens position signal is a signal indicating the position of the objective lens 104. The focus error signal is a control signal for the objective lens 104 to focus the laser beam on the information recording surface of the optical disc OD. The tracking error signal is a control signal for the objective lens 104 to follow a track on the information recording surface of the optical disc OD.

In FIG. 9, the direction F is the focusing direction. The direction T is the tracking direction. The direction T is the radial direction of the optical disc.

As a method for generating the focus error signal, for example, a known method such as an astigmatism method can be used. As a method for generating the tracking error signal, for example, a known method such as a push-pull method, a DPP (Differential Push-Pull) method, or a DPD (Differential Phase Detection) method can be used.

The central control unit 130 issues a command for controlling the actuator 106 to the actuator control unit 110. The central control unit 130 includes the control filter 61 and the gain increase filter 62 described in FIG.

In the second embodiment, the control filter 61 includes a filter for realizing feedback control as a constituent element, similar to that shown in the first embodiment. The control filter 61 includes, for example, a PID control filter as a constituent element.

In the second embodiment, the gain increasing filter 62 is, for example, a peaking filter, similar to the one shown in the first embodiment. The peak frequency PKf ₀ [Hz], which is the frequency at which the gain of the gain increase filter 62 is maximized, is the same as that in the first embodiment in FIGS. 6 (a), 6 (b), 7 (a), and 7 This is the same as described with reference to (b).

Note that, when it is desired to cause the objective lens 104 to follow the target position, the objective lens position signal among the signals output from the signal detection unit 120 is used. Further, when the objective lens 104 is to be recorded and reproduced by following the target track on the information recording surface of the optical disc OD, the focus error signal and the tracking error signal among the signals output from the signal detection unit 120 are used. Use.

The configuration of the servo control device 90 according to the second embodiment is not limited to the configuration in FIG.

As described above, according to the servo control device 90 and the servo control method according to the second embodiment, as in the case of the first embodiment, by including the gain increasing filter, the amplitude at the resonance point of the actuator can be increased. The change can be made smaller than before, and the amount of phase advance at a frequency where the gain of the amplitude of the open loop characteristic becomes 0 [dB] can be made larger than before. For this reason, the servo control apparatus 90 and the servo control method can make a control band higher than before. As a result, the servo control device 90 and the servo control method can realize high-precision control by ensuring the control stability and increasing the control band as compared with the prior art.

Embodiment 3 FIG.
In the second embodiment, the case where the control target 20 is an objective lens of an optical pickup has been described. In the third embodiment, the case where the control target 20 is a magnetic head of a magnetic disk device will be described. The magnetic disk device according to the third embodiment is an example of a servo control device that performs servo control, and is, for example, a hard disk device (HDD).

FIG. 10 is a block diagram schematically showing a configuration of a magnetic disk device which is the servo control device 140 according to the third embodiment.

As shown in FIG. 10, the servo control device 140 according to the third embodiment includes a magnetic disk MD, a control target 150, an actuator 160, an actuator control unit 170, a signal detection unit 180, and a central control unit 190. With. The control target 150 is a magnetic head of the magnetic disk device. The control target (magnetic head) 150 corresponds to the control target 20 of the first embodiment. The actuator 160 is a drive mechanism for the magnetic head. The actuator 160 corresponds to the drive mechanism 30 of the first embodiment. The actuator control unit 170 is a drive mechanism control unit. The actuator controller 170 corresponds to the drive mechanism controller 40 of the first embodiment. The actuator control unit 170 may be a part of the central control unit 190.

Also, the servo control device 140 includes a spindle motor 141 and a spindle motor control unit 142. The spindle motor 141 rotates the magnetic disk MD as a sample. The magnetic disk MD corresponds to the sample SA of the first embodiment. The spindle motor control unit 142 controls the spindle motor 141.

In Embodiment 3, the controlled object 150 includes a magnetization pattern detection unit. The actuator 160 includes an arm that supports the magnetization pattern detection unit. The actuator control unit 170 includes an arm control unit that moves the arm.

The signal detection unit 180 generates a magnetic head position signal indicating the position of the control target 150 as a magnetic head. Then, the signal detection unit 180 outputs the generated signal. The signal detection unit 180 corresponds to the signal detection unit 50 of the first embodiment.

The central control unit 190 gives a control signal SIG2 for controlling the actuator 160 to the actuator control unit 170. Further, the central control unit 190 includes the control filter 61 and the gain increase filter 62 described in FIG.

In the third embodiment, the control filter 61 includes a filter for realizing feedback control as a constituent element, similar to that shown in the first embodiment. The control filter 61 includes, for example, a PID control filter as a constituent element.

In the third embodiment, the gain increasing filter 62 is a peaking filter, similar to that shown in the first embodiment. The peak frequency PKf ₀ [Hz], which is the frequency at which the gain of the gain increase filter 62 is maximized, is the same as that in the first embodiment in FIGS. 6 (a), 6 (b), 7 (a), and 7 It is set so as to satisfy the same condition as described with reference to (b).

Note that the configuration of the servo control device 140 according to Embodiment 3 is not limited to the configuration of FIG.

As described above, according to the servo control device 140 and the servo control method according to the third embodiment, as in the case of the first embodiment, by including the gain increasing filter, the amplitude at the resonance point of the actuator can be increased. The change can be made smaller than before, and the amount of phase advance at a frequency where the gain of the amplitude of the open loop characteristic becomes 0 [dB] can be made larger than before. For this reason, the servo control device 140 and the servo control method can make the control band higher than before. Thereby, the servo control device 140 and the servo control method can realize highly accurate control by making the control band higher than the conventional one while ensuring the stability of the control.

Embodiment 4 FIG.
In the fourth embodiment, a case where the control target 20 is a mirror and the drive mechanism 30 is a motor will be described. That is, the fourth embodiment is an example of a servo control device that controls the mirror position by a motor so that the mirror has a desired angle.

FIG. 11 is a block diagram schematically showing a configuration of a motor control device that is the servo control device 200 according to the fourth embodiment.

As shown in FIG. 11, the servo control device 200 according to the fourth embodiment includes a signal detection unit 240 and a central control unit 250. FIG. 11 shows the control object 210, the actuator 220, and the actuator control unit 230.

The control object 210 is a mirror. The control target 210 corresponds to the control target 20 of the first embodiment. The actuator 220 is a motor. The actuator (motor) 220 corresponds to the drive mechanism 30 of the first embodiment.

Actuator control unit 230 controls actuator 220 in accordance with a command signal from central control unit 250. The actuator control unit 230 corresponds to the drive mechanism control unit 40 of the first embodiment. The actuator control unit 230 may be a part of the central control unit 250.

The signal detection unit 240 generates a mirror angle detection signal indicating the angle of the control object 210 as a mirror. And the signal detection part 240 outputs the produced | generated signal. The signal detection unit 240 corresponds to the signal detection unit 50 of the first embodiment.

The central control unit 250 gives a control signal SIG2 for controlling the actuator 220 to the actuator control unit 230. The central control unit 250 includes the control filter 61 and the gain increase filter 62 described in FIG. The central control unit 250 corresponds to the central control unit 60 of the first embodiment.

In the fourth embodiment, the control filter (61 in FIG. 4) includes a filter for realizing feedback control as a constituent element, similar to that shown in the first embodiment.
The control filter 61 includes, for example, a PID control filter as a constituent element.

In the fourth embodiment, the gain increasing filter (62 in FIG. 4) is a peaking filter, similar to that shown in the first embodiment. The peak frequency PKf ₀ [Hz], which is the frequency at which the gain of the gain increasing filter 62 is maximized, is the same as that in the first embodiment shown in FIGS. 6 (a), 6 (b), 7 (a), and 7 It is set so as to satisfy the same condition as described with reference to (b).

Note that the configuration of the servo control device 200 according to the fourth embodiment is not limited to the configuration of FIG. For example, the control object 210 may be a table that moves in accordance with the rotation of a motor (actuator 220) instead of a mirror. In this case, the signal detection unit 240 generates a position detection signal indicating the position of the control target 210 as a table. In general, the control object 210 is a driven body that moves according to the rotation of the motor (actuator 220). That is, the driven body (control target) 210 that moves according to the rotation of the motor 220 corresponds to the control target 20 of the first embodiment.

As described above, according to the servo control device 200 and the servo control method according to the fourth embodiment, as in the case of the first embodiment, by including the gain increase filter, the amplitude at the resonance point of the actuator can be increased. The change can be made smaller than before, and the amount of phase advance at a frequency where the gain of the amplitude of the open loop characteristic becomes 0 [dB] can be made larger than before. For this reason, the servo control apparatus 200 and the servo control method can make a control band higher than before. As a result, the servo control device 200 and the servo control method can realize high-precision control by ensuring a stable control and increasing the control band as compared with the prior art.

Modified example.
The servo control devices and servo control methods according to the first to fourth embodiments described above may be realized only by hardware resources such as electronic circuits, or may be realized by cooperation of hardware resources and software. May be. When realized by cooperation of hardware resources and software, the servo control device and the servo control method are realized, for example, by a computer program being executed by a computer. More specifically, it is realized by reading a computer program recorded on a recording medium such as a ROM (Read Only Memory) into a main storage device and executing it by a central processing unit (CPU). . The computer program may be provided by being recorded on a computer-readable recording medium such as an optical disk, or may be provided via a communication line such as the Internet.

It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist of the present invention.

The servo control device and the servo control method according to the present invention are an optical disk device and a magnetic disk as long as the device controls a position of a control target (particularly a relative position between a sample and a control target) using a drive mechanism. Various devices other than the device and the motor control device, for example, a production facility such as a robot having a control object that performs precise position control by an actuator, or an automobile, a ship having a control object that performs precise position control by an actuator, The present invention can be applied to various apparatuses such as transportation equipment such as aircraft.

DESCRIPTION OF SYMBOLS 10 Servo control apparatus, 11 Servo control apparatus, 20 Control object, 30 Drive mechanism, 40 Drive mechanism control part, 50 Signal detection part, 60 Central control part, 61 Control filter, 62 Gain increase filter, 70a Gain frequency characteristic in comparative example Curve, 70b gain frequency characteristic curve, 71a phase frequency characteristic curve in comparative example, 71b phase frequency characteristic curve, 80a to 80f multiplier, 80g, 80h delay device (shift register), 80i to 80l adder, 90 servo control device, 91 Spindle motor, 92 Spindle controller, 93 Thread motor, 94 Thread controller, 95 Laser controller, 100 Optical pickup, 101 Lens unit, 102 Laser light source, 103 Beam splitter, 104 Objective lens, 105 Light detector, 106 107, elastic support member, 110 actuator control unit, 120 signal detection unit, 130 central control unit, 140 servo control device, 141 spindle motor, 142 spindle motor control unit, 150 controlled object, 160 actuator, 170 actuator control unit, 180 Signal detection unit, 190 central control unit, 200 servo control device, 210 control target, 220 actuator, 230 actuator control unit, 240 signal detection unit, 250 central control unit, SA sample, OD optical disc, MD magnetic disc, FD ₁ phase Advancing frequency domain, FD ₂ delaying frequency domain, F, T direction.

Claims

A servo control device for controlling a drive mechanism for driving a controlled object,
A signal detection unit that generates a control target position signal that is a signal indicating the position of the control target that is movably supported;
A central control unit that generates a control signal for controlling the drive mechanism based on the control target position signal generated by the signal detection unit;
With
The central control unit is a gain increase having a gain frequency characteristic that locally increases an amplitude gain at a predetermined specific frequency in an open loop characteristic of the open loop including the signal detection unit and the driving mechanism. A servo control device comprising a filter.
2. The servo control device according to claim 1, wherein the gain increasing filter has a peak frequency which is a frequency at which the gain of the amplitude is maximum in the gain frequency characteristic.
The peak frequency is equal to or higher than a frequency at which an amplitude gain in the open loop characteristic becomes 0 [dB], and a phase in the open loop characteristic when the central control unit does not include the gain increasing filter is −180 [ The servo control device according to claim 2, wherein the servo control device has a frequency equal to or higher than a degree.
The drive mechanism has a resonance point;
The servo control device according to claim 2, wherein the peak frequency is higher than a resonance frequency that is a frequency of the resonance point.
The gain increasing filter has a phase frequency characteristic having a frequency region that advances a phase in a frequency range less than the specific frequency, and a frequency region that delays a phase in a frequency range exceeding the specific frequency. The servo control device according to any one of claims 1 to 4.
The servo control device according to any one of claims 1 to 5, wherein the gain increasing filter includes a biquadratic filter.
The control target is an objective lens provided in an optical pickup that scans on an optical disc, and the drive mechanism is an actuator that drives the objective lens, or
The control target is a magnetic head that scans on a magnetic disk, and the drive mechanism is an actuator that drives the magnetic head, or
The servo control device according to claim 1, wherein the drive mechanism is a motor, and the control target is a driven body that moves according to the rotation of the motor.
A servo control method for controlling a drive mechanism that drives a controlled object,
Based on the control signal supplied from the central control unit, driving the control object that is supported in a movable manner;
Generating a control target position signal, which is a signal indicating the position of the control target, in a signal detection unit;
In the open loop characteristic of the open loop including the drive mechanism and the signal detection unit, the central control unit gain gain having a gain frequency characteristic that locally increases the gain of the amplitude at a predetermined frequency. Generating the control signal from the control target position signal generated by the signal detection unit using a filter;
A servo control method characterized by comprising:
9. The servo control method according to claim 8, wherein the gain increasing filter has a peak frequency which is a frequency at which an amplitude gain is maximum in the gain frequency characteristic.
The peak frequency is equal to or higher than the frequency at which the gain of the amplitude in the open loop characteristic becomes 0 [dB], and the transfer function of the signal detection unit and the transfer of the control filter as the phase compensation filter provided in the central control unit 10. The servo control method according to claim 9, wherein a phase in an open loop characteristic expressed by a product of a function and a transfer function of the driving mechanism is equal to or higher than a frequency at which -180 [degrees] is obtained.