Steering mirror control system

Abstract

The adjustment time when changing the tilt angle of the steering mirror's reflective surface will be shortened, enabling high-speed driving. [Solution] A steering mirror control system comprising: a steering mirror with an adjustable tilt angle of the reflective surface; an actuator for driving the steering mirror; a tilt angle detection mechanism for detecting the tilt angle of the reflective surface; and a control unit that compares the detected value detected by the tilt angle detection mechanism with a predetermined target value and provides feedback control to the actuator to eliminate the deviation, wherein the control unit includes a position controller that performs phase compensation near the resonant frequency of the steering mirror, and inputs a signal indicating the target value to the downstream of the position controller for feedback control.

Description

Technical Field

[0001] The present invention relates to a steering mirror control system for controlling a steering mirror capable of adjusting the tilt angle of a reflecting surface.

Background Art

[0002] In recent years, research has been actively conducted towards the practical application of a laser fusion reactor that generates energy by irradiating a fuel pellet composed of deuterium and tritium with high-power laser light to cause implosion and initiate a fusion reaction.

[0003] As a laser fusion reactor, inside the reactor body for extracting energy, a spherical fuel pellet is projected at high speed using a fuel projection mechanism, and high-power pulsed laser light is uniformly irradiated on the fuel pellet that has reached a predetermined position (for example, the central position) inside the reactor body from all directions to cause a fusion reaction. There is a fuel projection type. In such a fuel projection type, energy is continuously generated by repeating the projection of the fuel pellet and the irradiation of the laser light at a rate of several times per second, and it is considered that by guiding this to the outside, power generation of several million kilowatts can be performed.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the fuel projection method described above, the position of the fuel pellets projected onto the reactor body is not always constant. Due to slight changes in friction between the fuel projection mechanism and the fuel pellets, the position shifts slightly (a few millimeters) each time a pellet is projected. Therefore, it is being considered to place a steering mirror equipped with a gimbal mechanism having multiple rotation axes in the optical path of the laser beam, and to drive an actuator each time a fuel pellet is projected to finely adjust the reflection angle, thereby irradiating the center of the shifted fuel pellet with the laser beam.

[0006] In order to increase the energy output of a laser fusion reactor, it is necessary to shorten the period for projecting fuel pellets and the period for irradiating with pulsed laser light, thereby causing fusion reactions to occur continuously at short intervals. However, the response speed of the steering mirror becomes the rate-limiting factor in this process. In other words, when the actuator is driven to change the tilt angle of the steering mirror's reflective surface in steps, the settling time until the tilt angle stabilizes near the target value becomes the rate-limiting factor. In particular, steering mirrors used in laser fusion reactors to reflect high-power laser light tend to be large in size, which lowers the resonant frequency and makes it easier for the settling time during control to become longer.

[0007] The present invention has been made in view of these problems, and its main objective is to shorten the settling time when changing the inclination angle of the steering mirror's reflective surface, thereby enabling high-speed driving. [Means for solving the problem]

[0008] In other words, the steering mirror control system according to the present invention comprises a steering mirror with an adjustable tilt angle of the reflective surface, an actuator for driving the steering mirror, a tilt angle detection mechanism for detecting the tilt angle of the reflective surface, and a control unit that compares the detected value detected by the tilt angle detection mechanism with a predetermined target value and performs feedback control of a control signal output to the actuator so that the deviation is eliminated. The control unit has a position controller that compensates for the phase near the resonant frequency of the steering mirror and increases the control gain, and is characterized in that it performs feedback control by inputting the signal indicating the target value to the stage after the position controller rather than before it.

[0009] With this configuration, even if low-frequency gain compensation is not included in the position controller, a step change in the tilt angle of the steering mirror's reflective surface that tracks the target value can be achieved. The absence of phase lag associated with low-frequency gain compensation means that a higher control gain can be set while maintaining phase margin. A higher control gain means a lower Q value in the overall system transfer function. A lower Q value is equivalent to a shorter settling time when changing the tilt angle of the steering mirror's reflective surface, thus enabling high-speed operation (for example, 10 Hz or more, as used in commercial laser fusion reactors).

[0010] In the case of the steering mirror, it is preferable that the position controller does not perform gain compensation in the low-frequency band. With this configuration, the low-frequency band of the overall system transfer function approximates the low-frequency band of the overall system transfer function without feedback control. Therefore, even without gain compensation in the low-frequency band, the step change in the tilt angle of the steering mirror's reflective surface can be achieved in a way that follows the target value.

[0011] Preferably, the steering mirror is feedback-controlled such that the position controller performs phase compensation only at the resonant frequency of the steering mirror, and maintains the high gain at the resonant frequency of the steering mirror without suppressing it. In this way, the high gain at the resonant frequency of the steering mirror can be directly converted into the control gain while maintaining the phase margin, further shortening the settling time when changing the tilt angle of the reflective surface of the steering mirror and enabling even faster driving.

[0012] Preferably, the steering mirror comprises a mirror body having the reflective surface, a gimbal mechanism having a pitch axis for rotating the mirror body vertically and a yaw axis for rotating the mirror body horizontally, and a counterweight for balancing the rotation in the gimbal mechanism. If the position controller included in the control unit described above does not perform low-frequency gain compensation, then in rotation around an axis asymmetric with respect to the direction of gravity, the effect of gravity due to the weight of the actuator cannot be feedback-controlled. Specifically, due to the asymmetry of the weight balance, an initial offset angle is applied to the steering mirror, and the drive range of the actuator is narrowed by the amount that cancels out this offset, thus reducing the drive range. Therefore, by providing a counterweight to balance the rotation around the axis, the asymmetry of rotation around the axis can be eliminated, the initial offset angle of the steering mirror can be eliminated, and the reduction in the drive range can be suppressed.

[0013] Preferably, the counterweight is for balancing the rotation around an axis that is asymmetrical with respect to gravity in the gimbal mechanism. This approach eliminates the rotational asymmetry around an axis asymmetrical to the direction of gravity, thereby eliminating the initial offset angle of the steering mirror and suppressing a decrease in the drive range. This is particularly useful when the steering mirror itself is installed at an angle.

[0014] As a specific aspect that significantly brings out the effects of the present invention, there is one in which the steering mirror reflects laser light for irradiating fuel in a laser fusion reactor and adjusts its traveling direction.

Effects of the Invention

[0015] According to the present invention configured as described above, the settling time when changing the tilt angle of the reflecting surface of the steering mirror is shortened, and it becomes possible to drive at high speed.

Brief Description of the Drawings

[0016] [Figure 1] A diagram schematically showing a laser fusion reactor of an embodiment of the present invention. [Figure 2] A front-side perspective view schematically showing the configuration of the steering mirror of the same embodiment. [Figure 3] A rear-side perspective view schematically showing the configuration of the steering mirror of the same embodiment. [Figure 4] A front-side plan view schematically showing the configuration of the steering mirror of the same embodiment. [Figure 5] A diagram schematically showing the configuration of the control mechanism of the steering mirror of the same embodiment. [Figure 6] A diagram schematically showing the control block of the steering mirror of the same embodiment.

Modes for Carrying Out the Invention

[0017] Hereinafter, a laser fusion reactor 200 including a steering mirror control system S according to an embodiment of the present invention will be described based on the drawings.

[0018] The steering mirror control system S of this embodiment is used in a laser fusion reactor 200 that generates energy by irradiating a fuel pellet P (for example, a small spherical fuel composed of deuterium and tritium. Note that the constituent elements and shape are not limited to this) with high-power laser light to cause implosion and generate a fusion reaction. Specifically, as shown in FIG. 1, this laser fusion reactor 200 includes a reactor main body V, a fuel injection mechanism F that injects the fuel pellet P into the reactor main body V at high speed (for example, about 100 m / s), and a laser irradiation mechanism L that irradiates the fuel that has reached a predetermined irradiation position R set in the reactor main body V with laser light (laser light for implosion) at the right timing. In this laser fusion reactor 200, the fuel injection mechanism F injects the fuel pellet P into the reactor main body V at a constant cycle (for example, about 10 Hz), and laser light is sequentially irradiated from the laser irradiation mechanism L to the fuel pellets P that are continuously injected.

[0019] The laser irradiation mechanism L includes a laser light source L1 that emits laser light and an optical system L2 that guides the laser light emitted from the laser light source L1 to the fuel pellet P injected into the reactor main body V. The laser fusion reactor 200 includes a plurality (for example, 100 or more) of laser irradiation mechanisms L, and can irradiate the fuel pellet P injected into the reactor main body V with laser light from a plurality of directions (the entire circumference) simultaneously.

[0020] The laser light source L1 is capable of outputting pulsed laser light with high energy sufficient to implode the fuel pellet P at a high repetition frequency (for example, about 10 Hz), and is installed outside the reactor main body V. The laser light source L1 of this embodiment emits laser light having a peak wavelength of 1064 nm, but is not limited to this.

[0021] The optical system L2 includes a plurality of mirrors that reflect laser light. The optical system L2 includes, as the mirror, a steering mirror (also referred to as a movable mirror) 100 whose angle of the reflecting surface 1s can be adjusted.

[0022] The laser irradiation mechanism L is equipped with a steering mirror control system S that reflects the laser beam in any direction to adjust its direction of travel. The steering mirror control system S of this embodiment includes a steering mirror 100 and a control mechanism 4 that controls the inclination angle of the reflective surface 1s of the steering mirror 100. By operating the steering mirror 100 with the control mechanism 4 to adjust the direction of travel of the laser beam, the laser beam can be irradiated onto the fuel pellet P, whose passing position is slightly (a few millimeters) off from the center of the irradiation position R each time it is projected onto the reactor body V. The steering mirror control system S of this embodiment will be described in detail below.

[0023] As shown in Figures 2-4, the steering mirror 100 comprises a mirror body 1 that reflects high-energy laser light (implosion laser light), a support part 2 that supports the mirror body 1, and a gimbal mechanism 3 interposed between the mirror body 1 and the support part 2, which tilts the mirror body 1 at any angle relative to the support part 2.

[0024] The mirror body 1 has a disc shape with a circular reflective surface 1s. The mirror body 1 is made of a translucent substrate such as a glass substrate, and a dielectric multilayer film (not shown) is formed on its front surface, which reflects the implosion laser light, in order to provide high laser damage resistance. The implosion laser light intersects within the dielectric multilayer film formed on the front surface of the mirror body 1 and is also intersected on the central axis of the mirror body 1. The reflective surface 1s is formed by the front surface of the dielectric multilayer film, and the implosion laser light is reflected by the dielectric multilayer film.

[0025] A dielectric multilayer film is constructed by layering multiple dielectric films with different refractive indices. Specifically, this dielectric multilayer film is formed using materials such as titanium oxide, barium oxide, and zirconium oxide, and has a reflectivity of, for example, 99% or more.

[0026] The support portion 2 of this embodiment comprises a plate-shaped base 21 and a pair of support plates 22 that are mounted upright on the surface of the base 21 (also called the base surface 21s). The pair of support plates 22 are positioned so that their face plates face each other. The mirror body 1 is installed so that its outer circumferential surface is sandwiched between the face plates of the pair of support plates 22, and the mirror body 1 is supported by this pair of support plates 22 so that its reflective surface 1s stands approximately perpendicular to the base surface 21s.

[0027] The gimbal mechanism 3 has multiple rotation axes extending in directions that intersect each other. Specifically, this gimbal mechanism 3 includes a first rotation axis 3a, which is a pitch axis that rotates the reflective surface 1s of the mirror body 1 in the vertical direction within a predetermined range, and a second rotation axis 3b, which is a yaw axis that rotates the reflective surface 1s of the mirror body 1 in the horizontal direction within a predetermined range. Here, the first rotation axis 3a is parallel to the base surface 21s, and the second rotation axis 3b is set to be perpendicular to the first rotation axis 3a. In the following, the optical axis direction of the mirror body 1 at the reference position (initial position) where the rotation angle of each rotation axis of the gimbal mechanism 3 is 0° (i.e., the direction perpendicular to the reflective surface 1s and perpendicular to the first rotation axis 3a and the second rotation axis 3b) will be defined as the reference axis direction.

[0028] More specifically, the gimbal mechanism 3 comprises a first rotating frame 31 connected to the support plate 22 of the support section 2 and rotatable about a first rotation axis 3a, and a second rotating frame 32 that supports the mirror body 1 and is connected to the first rotating frame 31 and rotatable about a second rotation axis 3b. The first rotating frame 31 is an annular plate shape, and its outer circumferential surface is connected to the pair of support plates 22 via the first rotation axis 3a. The second rotating frame 32 is also an annular plate shape, and its outer diameter is smaller than the inner diameter of the first rotating frame 31. This second rotating frame 32 is mounted inside the first rotating frame 31. Specifically, the outer circumferential surface of the second rotating frame 32 is connected to the inner circumferential surface of the first rotating frame 31 via the second rotation axis 3b. The mirror body 1 is then fitted inside the second rotating frame 32.

[0029] In the steering mirror 100 of this embodiment, at least one (specifically both) of the first rotation axis 3a and the second rotation axis 3b is made up of an elastically deformable shaft with both ends fixed, and the mirror body 1 rotates around the rotation axis as this shaft twists, but it is not limited to this configuration. For example, at least one or both of the first rotation axis 3a and the second rotation axis 3b may be configured as a highly flexible rotation mechanism using bearings or the like, with neither end of the shaft fixed.

[0030] Next, we will explain the control mechanism 4 that controls the inclination angle of the reflective surface 1s of the mirror body 1. The inclination angle of the reflective surface 1s of the mirror body 1 referred to here is the inclination angle of the optical axis of the reflective surface 1s of the mirror body 1 with respect to the reference axis direction.

[0031] The control mechanism 4 drives the gimbal mechanism 3 to control the tilt angle of the reflective surface 1s of the mirror body 1. As shown in Figure 5, it comprises an actuator 41 that drives the gimbal mechanism 3, a tilt angle detection mechanism 42 that detects the tilt angle of the reflective surface 1s of the mirror body 1, a fuel position detection sensor 43 that detects the passage position and passage time of fuel pellets P projected into the furnace body V, and a control unit 44 that controls the actuator 41.

[0032] This actuator 41 is configured to expand and contract in the direction of the reference axis in accordance with the voltage output from the control unit 44, and uses, for example, a voice coil motor. The control mechanism 4 of this embodiment includes, as actuators 41, a pair of first actuators 41a for driving the gimbal mechanism 3 around the first rotation axis 3a, and a pair of second actuators 41b for driving the gimbal mechanism 3 around the second rotation axis 3b.

[0033] The first actuator 41a and the second actuator 41b are installed in contact with the back surface of the first rotating frame 31 and the second rotating frame 32, respectively, so that their extension and retraction directions coincide with the reference axis direction. The first actuator 41a is installed in a pair, vertically arranged on the back side of the first rotating frame 31, when viewed from the reference axis direction. The second actuator 41b is installed in a pair, horizontally arranged on the back side of the second rotating frame 32, when viewed from the reference axis direction.

[0034] The tilt angle detection mechanism 42 in this embodiment utilizes the principle of an optical lever. It detects the tilt angle of the reflective surface 1s by irradiating a detection light onto the detection surface 1d set on the back of the mirror body 1 and sensing the reflected light. In this embodiment, the detection surface 1d is parallel to the reflective surface 1s set on the front of the mirror body 1, but it is not limited to this and they may be inclined relative to each other. The tilt angle detection mechanism 42 does not utilize an optical lever; it may also use a different method.

[0035] Specifically, the tilt angle detection mechanism 42 includes a light emitting unit 42a that emits detection light to the detected surface 1d of the mirror body 1, a light receiving element 42b that senses reflected light from the detected surface 1d, and a tilt angle calculation unit 42c that calculates the tilt angle of the reflective surface 1s of the mirror body 1 or a related value (for example, the amount of displacement of the tilt angle) based on a predetermined algorithm based on the sensing content of the light receiving element 42b.

[0036] The light-emitting section 42a is equipped with a detection light source such as an LED (light-emitting diode), SLD (superluminescent diode), or LD (laser diode), and emits detection light from the back side toward the mirror body 1.

[0037] The light-receiving element 42b receives the detection light reflected from the detection surface 1d and measures the position of the light spot and the intensity of the detection light. Examples include a PSD (Position Sensitive Detector) and a QPD (Quadrant Photodiode).

[0038] The tilt angle calculation unit 42c receives an electrical signal from the light receiving element 42b that changes depending on the intensity of the detected light and the position of the light spot, calculates the tilt angle of the mirror body 1 or a related value based on the change in the electrical signal, and outputs an angle information signal indicating this calculated value to the control unit 44.

[0039] The fuel position detection sensor 43 detects the time it takes for fuel pellets P projected into the reactor body V by the fuel projection mechanism F to pass through the irradiation position R, and the amount of displacement of the fuel pellets P from the center of the irradiation position R (passage position). This fuel position detection sensor 43 may be configured using, for example, a plurality of reflective or transmissive photointerrupters (not shown) arranged in the projection direction of the fuel pellets P. The fuel position detection sensor 43 generates a signal (fuel position signal) indicating the passage position and passage time of the detected fuel pellets P, and outputs this to the control unit 44.

[0040] The control unit 44 outputs control signals to the first actuator 41a and the second actuator 41b based on the angle information signal output from the tilt angle detection mechanism 42 and the fuel position information signal output from the fuel position detection sensor 43. Specifically, the control unit 44 functions as a target value calculation unit 44a that calculates the target tilt angle (target value) of the target mirror body 1 based on the position of the fuel pellet P indicated by the fuel position information signal, and as a control signal output unit 44b that outputs control signals to each actuator 41.

[0041] Specifically, the control signal control unit 44b compares the calculated target tilt angle (target value) with the current measured tilt angle (detected value) of the mirror body 1 indicated by the tilt angle detection mechanism 42, and generates control signals to control the displacement of the first actuator 41a and the second actuator 41b so that the deviation between them is eliminated, and outputs them to each actuator 41. Specifically, the control signal output unit 44b feedback controls the control signals output to each actuator 41 so that the measured tilt angle matches the target tilt angle (so that the deviation between the target value and the detected value is eliminated). The control unit 44 generates a control signal each time a fuel pellet P is projected from the fuel projection mechanism F and outputs it to each actuator 41.

[0042] In this embodiment, as shown in Figure 6, the control signal output unit 44b includes a position controller 441 that performs phase compensation near the resonant frequency of the steering mirror 100. The signal indicating the target value calculated by the target value calculation unit 44a is input not before the position controller 441, but after it, i.e., directly before the actuator 41 of the steering mirror 100, to perform feedback control.

[0043] Specifically, the position controller 441 is configured to perform feedback control to suppress the control gain in the low-frequency band and increase the control gain in the high-frequency band. More specifically, the position controller 441 does not perform gain compensation in the low-frequency band. Even more specifically, the position controller 441 performs phase compensation only near the resonant frequency of the steering mirror 100 and is configured to perform feedback control so as not to suppress the high gain of the steering mirror 100 near the resonant frequency. In other words, the control signal output unit 44b is configured to perform feedback control using only phase lead compensation, without phase lag compensation (gain compensation). Furthermore, if sufficient phase margin can be secured at the unity gain frequency, the gain in the low-frequency band can be suppressed by a high-pass filter or the like. In other embodiments, a high-pass filter may not be implemented.

[0044] In this embodiment, the steering mirror 100 further includes a first counterweight 51 for balancing rotation around the pitch axis in the gimbal mechanism 3, and a second counterweight 52 for balancing rotation around the yaw axis in the gimbal mechanism 3. These counterweights 51 and 52 are for balancing rotation around axes asymmetric with respect to gravity in the gimbal mechanism 3.

[0045] As shown in Figures 2 and 4, the first counterweight 51 and the second counterweight 52 are attached to the first rotating frame 31 and the second rotating frame 32, respectively. Specifically, the first counterweight 51 has a curved strip shape when viewed from above and is attached to the top and bottom of the front surface of the first rotating frame 31 so as to be symmetrical with respect to the pitch axis 3a. The second counterweight 52 also has a curved strip shape when viewed from above and is attached to the left and right of the front surface of the second rotating frame 32 so as to be symmetrical with respect to the yaw axis 3b.

[0046] By arranging the system so that the target value signal is input to the stage after the position controller 441 rather than before, the transfer function of the entire system, including feedback control, becomes G(s) / {1+C(s)·H(s)·G(s)}. Since no gain compensation is performed in the low-frequency band, C(s)<<1 in the low-frequency band, so G(s) / {1+C(s)·H(s)·G(s)}≈G(s), which approximates the transfer function G(s) of the entire system without feedback control.

[0047] In many control systems, the target value signal is often input to the stage before the position controller 441. In this case, the transfer function of the entire system, including feedback control, is C(s)·H(s)·G(s) / {1+C(s)·H(s)·G(s)}. If low-frequency gain compensation is not performed in this case (i.e., C(s)<<1), then C(s)·H(s)·G(s) / {1+C(s)·H(s)·G(s)}≈0, and the step change will not track the target value. Therefore, normally, low-frequency gain compensation is performed (i.e., C(s)>>1), so that C(s)·H(s)·G(s) / {1+C(s)·H(s)·G(s)}≈1, thereby achieving target value tracking. However, such gain compensation introduces a phase lag, making it difficult to set a higher control gain (even with phase compensation) in order to maintain phase margin.

[0048] With the laser fusion reactor 200 using the steering mirror control system S of this embodiment configured in this way, even if low-frequency gain compensation is not included in the position controller 441, a step change in the tilt angle of the reflective surface 1s of the steering mirror 100 that tracks the target value can be achieved. The absence of phase delay associated with low-frequency gain compensation means that a higher control gain can be set near the resonance frequency while maintaining phase margin. A higher control gain means a lower Q value for the transfer function of the entire system. A lower Q value is equivalent to a shorter settling time when changing the tilt angle of the reflective surface 1s of the steering mirror 100, so high-speed driving (for example, 10 Hz or higher, which is used in commercial laser fusion reactors) becomes possible. In addition, if there is sufficient phase margin at the unity gain frequency, the feedback gain in the low-frequency band is suppressed by implementing a high-pass filter in the low-frequency band, and G(s) is quickly approximated in the low-frequency band. These measures shorten the period for projecting the fuel pellets P and the period for irradiating with pulsed laser light, allowing for continuous fusion reactions at shorter intervals and increasing the energy output of the laser fusion reactor 200.

[0049] However, the present invention is not limited to the embodiments described above. For example, the steering mirror control system S of the above embodiment was used to reflect implosion laser light in a laser fusion reactor 200, but is not limited to this. The steering mirror control system S of other embodiments may be used for other purposes, for example, in a fast-ignition type laser fusion reactor 200 to reflect laser light for heating fuel pellets P, or in other types of laser fusion reactors. Furthermore, the steering mirror control system S is not limited to use in the laser fusion reactor 200, and may be used for any purpose of reflecting laser light. Also, the steering mirror 100 may be used to reflect light other than laser light.

[0050] In the above embodiment, a dielectric multilayer film was formed on the front surface of the mirror body 1 and this dielectric multilayer film was set as the reflective surface, but the embodiment is not limited to this. In other embodiments, a dielectric multilayer film may not be formed on the front surface of the mirror body 1.

[0051] In other embodiments, the steering mirror 100 may not have to include either the first counterweight 51 or the second counterweight 52, nor may it have to include both.

[0052] Furthermore, while the gimbal mechanism 3 in the above embodiment had multiple intersecting rotation axes, it is not limited to this. The gimbal mechanism 3 in other embodiments may have only one rotation axis, and the mirror body 1 may be tiltable in only one direction.

[0053] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. [Explanation of symbols]

[0054] S ···Steering mirror control system 200... Laser fusion reactor P...Meat pellets V...furnace body F...Fuel injection mechanism L... Laser irradiation mechanism L1... Laser light source L2...Optical system 100... Steering mirror 1 ···Mirror body 11. Dielectric multilayer film 3. Gimbal mechanism 4. Control mechanism 42. Tilt angle detection mechanism 42a...Light output section 42b... Light-receiving element 42c...Inclination angle calculation section 44... Control Unit 51 ···First Counterweight 52 ···Second Counterweight

Claims

1. A steering mirror with an adjustable tilt angle for the reflective surface, An actuator for driving the steering mirror, A tilt angle detection mechanism for detecting the tilt angle of the reflective surface, The system includes a control unit that compares the detected value detected by the tilt angle detection mechanism with a predetermined target value and provides feedback control to the actuator to eliminate the deviation. A steering mirror control system comprising a control unit which includes a position controller that performs phase compensation near the resonant frequency of the steering mirror, and a signal indicating the target value which is input to the downstream of the position controller for feedback control.

2. The steering mirror control system according to claim 1, wherein the position controller is feedback controlled so as not to perform gain compensation in the low-frequency band.

3. The steering mirror control system according to claim 2, wherein the position controller performs phase compensation only at the resonant frequency of the steering mirror and provides feedback control so as not to suppress the high gain at the resonant frequency of the steering mirror.

4. The aforementioned steering mirror, A mirror body having the aforementioned reflective surface, A gimbal mechanism having a pitch axis for rotating the mirror body vertically and a yaw axis for rotating the mirror body horizontally, The steering mirror control system according to claim 2 or 3, further comprising a counterweight for balancing the rotation around each axis of the gimbal mechanism.

5. The steering mirror control system according to claim 4, wherein the counterweight is for balancing the rotation of the gimbal mechanism around an axis asymmetric with respect to the direction of gravity.

6. The steering mirror control system according to claim 1, wherein the steering mirror adjusts its direction of travel by reflecting laser light used to irradiate fuel in a laser fusion reactor.

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