Novel Fast Steering Mirror Based on Piezoelectric and Electromagnetic Composite Drive

Abstract

The present invention relates to a novel fast steering mirror based on piezoelectric and electromagnetic composite drive, belonging to the technical field of optical instrument devices. Existing fast steering mirrors have deficiencies in terms of driving accuracy, response speed, and stability. The key points of the technical solution of the present invention lie in the combined structure of a base, a mirror assembly, a piezoelectric drive unit, an electromagnetic drive unit, and a control module. The control module adopts a time-division multiplexing strategy to achieve the switching of the piezoelectric and electromagnetic drive circuits, and at the same time collects key parameters through a time-division monitoring algorithm. This fast steering mirror is mainly used in high-precision optical systems and can achieve fast and accurate beam pointing adjustment.

Description

Technical Field

[0001] The present invention relates to the technical field of optical instrument equipment. More specifically, the present invention relates to a novel fast steering mirror based on piezoelectric and electromagnetic composite drive. Background Art

[0002] In modern optical systems, as a key beam pointing control device, the fast steering mirror is widely used in fields such as laser communication, optical imaging, and adaptive optics. Its main function is to quickly and accurately adjust the propagation direction of the beam to meet the requirements of the system for beam pointing accuracy and response speed.

[0003] The traditional driving methods of fast steering mirrors mainly include piezoelectric drive and electromagnetic drive. The piezoelectric drive has the advantages of fast response speed and high displacement accuracy, but the output force is small, and there are non-linear characteristics such as hysteresis and creep, which will affect the driving accuracy and stability when working under large loads or for a long time. For example, in some optical systems that require rapid adjustment of large-aperture mirrors, piezoelectric actuators may not be able to provide sufficient driving force to achieve rapid response.

[0004] The electromagnetic drive has the advantages of large output force and long stroke, but the response speed is relatively slow, and it is easily affected by external magnetic fields. In optical systems with extremely high requirements for response speed, the response time of electromagnetic actuators may not meet the dynamic requirements of the system. In addition, heat is generated during the operation of the electromagnetic drive, resulting in changes in the performance of the actuator and affecting the stability of the fast steering mirror.

[0005] In order to overcome the deficiencies of a single driving method, some studies have attempted to adopt composite drive technology. However, there are many problems in the switching control of the driving circuit, signal acquisition and processing, and the collaborative work between each driving unit of the existing composite drive fast steering mirrors. For example, during the switching process of the driving circuit, interference signals are likely to appear, affecting the normal operation of the fast steering mirror; inaccurate signal acquisition leads to the inability to timely adjust the driving parameters to ensure the accuracy and stability of the fast steering mirror.

[0006] At the same time, the mechanical structure design of the fast steering mirror also has an important impact on its performance. Traditional connection structures and support methods may introduce additional vibrations and noises, reducing the dynamic performance of the fast steering mirror. In addition, under different working environments, factors such as temperature changes will cause thermal deformation of the structure of the fast steering mirror, thereby affecting its beam pointing accuracy. Therefore, how to design a novel fast steering mirror that can effectively combine the advantages of piezoelectric drive and electromagnetic drive and solve the above problems at the same time has become an urgent technical problem in the current optical field. Summary of the Invention

[0007] An object of the present invention is to solve at least the above problems and provide at least the advantages described hereinafter.

[0008] To achieve these objects and other advantages according to the present invention, a novel fast steering mirror based on piezoelectric and electromagnetic composite drive is provided, including:

[0009] A base provided with four mounting planes, wherein positioning bosses are provided on two opposite mounting planes, and mounting grooves are provided on the other two opposite mounting planes;

[0010] A mirror assembly connected to the base through three groups of flexible hinges, and the three groups of flexible hinges are evenly distributed in a 120° circle;

[0011] A piezoelectric drive unit including two piezoelectric ceramic drivers symmetrically distributed on both sides of the mirror assembly. One end of each piezoelectric ceramic driver is fixed to the positioning boss of the base through an epoxy resin adhesive layer, and the other end is connected to the edge of the mirror assembly through a ball head connector;

[0012] An electromagnetic drive unit including two groups of coil assemblies and two groups of permanent magnet assemblies. The two groups of coil assemblies are respectively embedded in the mounting grooves of the base, and the two groups of permanent magnet assemblies are symmetrically fixed to the bottom surface of the mirror assembly. The magnetic pole direction of each permanent magnet assembly forms an angle with the axis direction of the corresponding coil assembly;

[0013] A control module including a piezoelectric drive circuit, an electromagnetic drive circuit and a microcontroller unit. The output end of the piezoelectric drive circuit is connected to the piezoelectric ceramic driver through a silver wire, and the output end of the electromagnetic drive circuit is connected to the coil assembly through a copper wire. The microcontroller unit is configured to implement a frequency switching of 10 kHz ± 100 Hz between the piezoelectric drive circuit and the electromagnetic drive circuit by using a time-division multiplexing strategy;

[0014] Wherein, the microcontroller unit closes the electromagnetic power supply to collect the impedance phase angle during the piezoelectric drive stage, and closes the piezoelectric excitation to collect the current ripple coefficient during the electromagnetic drive stage through a time-division monitoring algorithm. Each drive cycle contains 16 - 20 alternating switching pulses;

[0015] The telescopic direction of the piezoelectric ceramic driver forms a deflection angle with the rotation axis of the mirror assembly, and the axis direction of the coil assembly forms a deflection angle with the rotation axis of the mirror assembly.

[0016] Preferably, each drive cycle contains 16 alternating switching pulses;

[0017] The magnetic pole direction of each permanent magnet assembly forms a 45° angle with the axis direction of the corresponding coil assembly;

[0018] The telescopic direction of the piezoelectric ceramic driver forms a 15° deflection angle with the rotation axis of the mirror assembly;

[0019] The axial direction of the coil assembly forms a 30° deflection angle with the rotation axis of the mirror assembly.

[0020] Preferably, the switching frequency of the drive signal is 10 kHz ± 100 Hz and satisfies:

[0021] The resonance frequency of the piezoelectric ceramic actuator is 9.5 - 10.5 kHz, and the deviation from the switching frequency is ≤ ±5%;

[0022] The mechanical response bandwidth of the electromagnetic drive unit is 0 - 5 kHz, and the switching frequency is twice the upper limit of the bandwidth.

[0023] Preferably, the control module further includes:

[0024] A multi-dimensional feedback compensation unit, which includes a three-axis MEMS accelerometer embedded in the back of the mirror assembly and a linear Hall sensor array disposed below the permanent magnet assembly;

[0025] A dynamic switching engine, which adopts a time-sharing monitoring strategy, collects the impedance phase angle during the piezoelectric drive stage and the current ripple coefficient during the electromagnetic drive stage, and realizes the adaptive compensation of the switching frequency through the microcontroller unit;

[0026] When it is detected that the temperature of the piezoelectric ceramic actuator rises, the switching frequency shifts to a lower frequency and the duty ratio of the electromagnetic drive signal is increased by 3%;

[0027] When the Hall sensor detects that the displacement exceeds the tolerance, a compensation pulse sequence is inserted, and the pulse width is linearly proportional to the displacement error amount.

[0028] Preferably, the time-sharing monitoring strategy further includes a time-sharing isolation strategy:

[0029] During the piezoelectric drive stage, the power supply circuit of the coil assembly is cut off by a relay in the electromagnetic drive circuit, and the electromagnetic drive signal is blocked from being transmitted to the coil assembly through an optocoupler isolator;

[0030] During the electromagnetic drive stage, the power supply circuit of the piezoelectric ceramic actuator is cut off by a relay in the piezoelectric drive circuit, and the residual charge of the piezoelectric ceramic actuator is discharged through a reverse-parallel diode;

[0031] Among them, a protection time gap is provided between the piezoelectric drive stage and the electromagnetic drive stage, and the protection time gap is 2% of the duration of a single switching cycle and not less than 1 μs.

[0032] Preferably, the permanent magnet assembly includes:

[0033] Gradient magnetization laminate, which includes a neodymium-iron-boron-based bottom layer and a samarium-cobalt intermediate layer, where the magnetic polarization intensity of the neodymium-iron-boron-based bottom layer is ≥ 1.3 T, and the samarium-cobalt intermediate layer is provided with a honeycomb microporous structure, and the pores of the honeycomb microporous structure are filled with a flexible silicone damping material;

[0034] Halbach array, which is arranged on the upper surface of the samarium-cobalt intermediate layer. The Halbach array is composed of 4 neodymium-iron-boron permanent magnet sheets. The magnetization directions of adjacent neodymium-iron-boron permanent magnet sheets differ by 22.5°, and the overall magnetic pole direction forms a fixed 45° angle with the axis direction of the coil assembly. The vertical field component is enhanced through the magnetic field superposition effect of the Halbach array;

[0035] Thermal expansion compensation structure. Symmetrical stress relief grooves with a laser etching depth of 0.2 - 0.3 mm are formed on the surface of the samarium-cobalt intermediate layer and in the area outside the Halbach array. Invar alloy sheets are embedded in the symmetrical stress relief grooves, and the length direction of the symmetrical stress relief grooves is consistent with the radial direction of the rotation axis of the mirror assembly.

[0036] Preferably, the thickness of each layer in the gradient magnetization laminate is as follows: the neodymium-iron-boron-based bottom layer is 1.5 - 1.8 mm, the samarium-cobalt intermediate layer is 0.6 - 0.8 mm, the depth of the honeycomb microporous structure of the samarium-cobalt intermediate layer is 0.6 - 0.8 mm, and the honeycomb porosity is 30% - 40%.

[0037] Preferably, the flexible hinge is an elastic metal sheet with a rectangular cross-section, and the thickness is 0.2 - 0.5 mm;

[0038] Both ends of the flexible hinge are respectively provided with mounting holes. One end of each group of flexible hinges is fixed to the base by screws, and is located below the mirror assembly and deviated from the rotation axis of the mirror assembly. The other end of each group of flexible hinges is fixed to the side wall edge of the mirror assembly by screws, so that the flexible hinge is arranged obliquely, and the inclination angle forms a 20° angle with the rotation axis of the mirror assembly.

[0039] Preferably, the ball head connector includes:

[0040] Ball head seat, which is fixed in a preset mounting hole on the edge of the mirror assembly by screws;

[0041] Ball head rod, one end of which is threadedly connected to the output end of the piezoelectric ceramic actuator, and the other end is provided with a ball head with a diameter of 2 - 3 mm, and the surface of the ball head is coated with a diamond-like carbon coating;

[0042] The ball head seat is provided with a hemispherical mating groove, and the inner wall of the hemispherical mating groove is coated with a polytetrafluoroethylene wear-resistant layer. The ball head forms a clearance fit with the hemispherical mating groove, and the fit clearance is 0.05 mm.

[0043] The present invention has at least the following beneficial effects:

[0044] First, by combining the advantages of piezoelectric drive and electromagnetic drive, the present invention achieves a good balance between high precision and large driving force for the fast steering mirror. The application of the time-division multiplexing strategy and the time-division monitoring algorithm effectively reduces the interference between drive circuits, improves the accuracy of signal acquisition, and thus ensures the driving accuracy and stability of the fast steering mirror. At the same time, the reasonable mechanical structure design reduces the introduction of vibration and noise, and improves the dynamic performance of the fast steering mirror.

[0045] Second, the optimized number of switching pulses and the angular relationship of each component enable the fast steering mirror to more precisely control the rotation of the mirror surface during the driving process, further improving the driving accuracy and stability. The specific angular setting is beneficial to giving full play to the synergistic effect of piezoelectric drive and electromagnetic drive, and improving the overall performance of the fast steering mirror.

[0046] Third, ensuring that the switching frequency of the drive signal matches the resonant frequency of the piezoelectric ceramic actuator and the mechanical response bandwidth of the electromagnetic drive unit avoids the performance degradation caused by frequency mismatch. This allows the fast steering mirror to maintain good performance under different working conditions, and improves the reliability and stability of the system.

[0047] Fourth, the setting of the multi-dimensional feedback compensation unit and the dynamic switching engine enables the fast steering mirror to automatically adjust the switching frequency according to different working conditions and achieve adaptive compensation. In the case of temperature changes and displacement out-of-tolerance, etc., it can take timely measures to ensure the accuracy and stability of the fast steering mirror, and improve the robustness of the system.

[0048] Fifth, the implementation of the time-division isolation strategy effectively avoids the interference signals that occur during the switching process of the drive circuit, and ensures the normal operation of the fast steering mirror. The setting of the protection time gap further improves the safety and reliability of the system, and reduces the damage to the fast steering mirror caused by the impact during the moment of circuit switching.

[0049] Sixth, the unique design of the permanent magnet assembly, including the gradient magnetization laminate, the Halbach array, and the thermal expansion compensation structure, improves the performance and stability of the permanent magnet. The structure and material selection of the gradient magnetization laminate enhance the magnetic field strength, the magnetic field superposition effect of the Halbach array further enhances the vertical field component, and the thermal expansion compensation structure reduces the influence of temperature changes on the performance of the permanent magnet, thereby improving the accuracy and stability of the fast steering mirror.

[0050] Seventh, reasonably determining the thickness and porosity of each layer of the gradient magnetization laminate can optimize the performance of the permanent magnet. Appropriate thickness and porosity can ensure the magnetic field strength and stability of the permanent magnet, while reducing the weight of the permanent magnet and improving the dynamic performance of the fast steering mirror.

[0051] Eighth, the design of the structure and installation method of the flexible hinge effectively reduces the transmission of vibration and noise, and improves the dynamic performance of the fast steering mirror. The flexure hinge arranged obliquely can better adapt to the rotation of the mirror surface and provide stable support. At the same time, the selection of beryllium bronze material ensures the strength and durability of the flexure hinge.

[0052] Ninth, the design of the structure and material of the ball head connector improves its wear resistance and fitting accuracy. The application of diamond-like carbon coating and polytetrafluoroethylene wear-resistant layer reduces the friction and wear between the ball head and the ball head seat, ensuring the reliable connection between the piezoelectric drive unit and the mirror assembly, thereby improving the drive accuracy and stability of the fast steering mirror.

[0053] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and will also be understood by those skilled in the art through the research and practice of the present invention. Brief Description of the Drawings

[0054] Figure 1 The top view layout schematic diagram of the fast steering mirror of one technical solution of the present invention;

[0055] Figure 2 The detailed view of the permanent magnet assembly of one technical solution of the present invention;

[0056] Figure 3 The schematic diagram of the Halbach array of one technical solution of the present invention.

[0057] Reference numerals in the drawings: base 1, mounting plane 2, boss 3, mounting groove 4, flexure hinge 5, permanent magnet assembly 6, ball head connector 7, piezoelectric ceramic actuator 8, neodymium iron boron-based bottom layer 9, samarium cobalt intermediate layer 10, Halbach array 11, symmetric stress relief groove 12. Detailed Embodiments

[0058] The following further describes the present invention in detail with reference to the drawings, so that those skilled in the art can implement it according to the description in the specification.

[0059] It should be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified; in the description of the present invention, the orientation or positional relationship indicated by terms such as... is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of the present invention.

[0060] As Figures 1 to 3As shown in the figure, the present invention provides a novel fast steering mirror based on piezoelectric and electromagnetic composite drive, including:

[0061] A base 1, on which there are four mounting planes 2, and positioning bosses 3 are provided on two opposite mounting planes 2, and mounting grooves 4 are provided on the other two opposite mounting planes 2;

[0062] A mirror assembly, which is connected to the base 1 through three groups of flexible hinges 5, and the three groups of flexible hinges 5 are evenly distributed in a 120° circumference;

[0063] A piezoelectric drive unit, which includes two piezoelectric ceramic drivers 8, and the two piezoelectric ceramic drivers 8 are symmetrically distributed on both sides of the mirror assembly. One end of each piezoelectric ceramic driver 8 is fixed to the positioning boss 3 of the base 1 through an epoxy resin adhesive layer, and the other end is connected to the edge of the mirror assembly through a ball head connector 7;

[0064] An electromagnetic drive unit, which includes two groups of coil assemblies and two groups of permanent magnet assemblies 6. The two groups of coil assemblies are respectively embedded in the mounting grooves 4 of the base 1, and the two groups of permanent magnet assemblies 6 are symmetrically fixed to the bottom surface of the mirror assembly. The magnetic pole direction of each permanent magnet assembly 6 forms an angle with the axis direction of the corresponding coil assembly;

[0065] A control module, which includes a piezoelectric drive circuit, an electromagnetic drive circuit and a microcontroller unit. The output end of the piezoelectric drive circuit is connected to the piezoelectric ceramic driver 8 through a silver wire, and the output end of the electromagnetic drive circuit is connected to the coil assembly through a copper wire. The microcontroller unit is configured to adopt a time-division multiplexing strategy to realize the switching of the piezoelectric drive circuit and the electromagnetic drive circuit at 10 kHz ± 100 Hz;

[0066] Among them, the microcontroller unit closes the electromagnetic power supply through a time-division monitoring algorithm to collect the impedance phase angle during the piezoelectric drive stage, and closes the piezoelectric excitation to collect the current ripple coefficient during the electromagnetic drive stage. Each drive cycle contains 16 - 20 alternating switching pulses;

[0067] The telescopic direction of the piezoelectric ceramic driver 8 forms a deflection angle with the rotation axis of the mirror assembly, and the axis direction of the coil assembly forms a deflection angle with the rotation axis of the mirror assembly.

[0068] In the above technical solution, specifically, for the connection structure between the base 1 and the mirror assembly, the base 1 can be made of 6061 aluminum alloy material, and its four mounting planes 2 can be arranged symmetrically in the X-axis and Y-axis directions. Among them, positioning bosses 3 are provided on two mounting planes 2 in the X-axis direction, the thickness of the positioning bosses 3 can be set to 1.2 - 1.5 mm, and a V-shaped positioning groove can be machined on the surface of the positioning bosses 3. Mounting grooves 4 are provided on two mounting planes 2 in the Y-axis direction, the groove depth can be set to 2.0 - 2.5 mm, and M3 threaded holes can be opened at the bottom of the grooves for fixing the coil assembly. The mirror assembly can be made of fused quartz material, with a diameter that can be selected in the range of 30 - 50 mm and a thickness of 3 - 5 mm. Three groups of flexible hinges 5 can be evenly distributed in a 120° circle, and the included angle between the axis of each group of hinges and the mirror rotation axis can be set to 20° ± 2°. During assembly, the positioning bosses 3 can be located in the positive and negative X-directions of the base 1, the mounting grooves 4 are located in the positive and negative Y-directions, and both ends of the flexible hinges 5 are fixed to the sides of the base 1 and the mirror assembly with M1.6 stainless steel screws respectively.

[0069] For the piezoelectric and electromagnetic drive units, the piezoelectric ceramic actuator 8 can be selected as the AE0203D08 model of NEC Corporation, and its telescopic amount range can be set to 0 - 15 μm, and the drive voltage range is 0 - 150 V. The ball diameter of the ball head connector 7 can be selected in the 2.5 mm specification, and the inner diameter of the ball head seat can be set to 2.55 mm to form a clearance fit of 0.05 mm. In the coil assembly, the number of coil turns can be set to 200 - 250 turns. The permanent magnet assembly 6 can be selected as N35EH grade neodymium iron boron material, and its size can be set to 10 × 10 × 3 mm. During assembly, the piezoelectric actuator can be symmetrically installed on both sides of the mirror in the ±X direction, and the center line of the ball head connector 7 can form a 15° included angle with the mirror rotation axis. The coil assembly can be embedded in the mounting groove 4 in the Y-axis direction of the base 1, and its axis forms a 30° included angle with the mirror rotation axis. The permanent magnet assembly 6 can be pasted on both sides of the bottom surface of the mirror in the ±Y direction.

[0070] For the control module, the microcontroller unit can select the STM32H743 chip from STMicroelectronics. Its PWM output frequency can be set to 9.9 - 10.1 kHz. The piezoelectric drive circuit can select the PA85 high-voltage operational amplifier module from APEX, with an output voltage range of 0 - 200V. The electromagnetic drive circuit can select the DRV8870 motor drive chip from TI, with a peak output current of 3.6A. The time-division multiplexing strategy can set each drive cycle to include 18 switching pulses. Among them, the duty cycle of the piezoelectric drive stage can be set to 45%, and the duty cycle of the electromagnetic drive stage is 55%. The impedance phase angle detection can use the AD5933 impedance analysis chip, with a sampling frequency of 100 kHz. The current ripple coefficient measurement can use the INA240 current detection amplifier, with a bandwidth of 500 kHz. The control signal line can use a silver-plated copper wire with a diameter of 0.1 mm, and the power line uses a multi-strand copper wire with a diameter of 0.5 mm. During assembly, the control module can be installed in the installation cavity reserved on the bottom surface of the base 1 and connected to each drive unit through an FPC flexible circuit board.

[0071] This technical solution realizes high-bandwidth precision control through a composite drive method. The piezoelectric drive unit provides high-frequency micro-displacement compensation, and the electromagnetic drive unit realizes large-stroke coarse adjustment. The time-division multiplexing control strategy effectively avoids the mutual interference between the two drive methods, and the 10 kHz switching frequency matches the resonance characteristics of the piezoelectric material. The combined design of the flexible hinge 5 and the ball head connector 7 reduces mechanical hysteresis while ensuring motion accuracy. The actual measurement shows that this structure can achieve a resolution of 0.1 μrad within the deflection range of ±5°, and the closed-loop bandwidth reaches 5 kHz, which is 2.3 times faster than the response speed of a fast steering mirror with a single drive method, and the power consumption is reduced by 18%.

[0072] In another technical solution, further, each drive cycle contains 16 alternating switching pulses;

[0073] The magnetic pole direction of each permanent magnet assembly 6 forms a 45° angle with the axis direction of the corresponding coil assembly;

[0074] The telescopic direction of the piezoelectric ceramic actuator 8 forms a 15° deflection angle with the rotation axis of the mirror assembly;

[0075] The axis direction of the coil assembly forms a 30° deflection angle with the rotation axis of the mirror assembly.

[0076] In the above technical solution, specifically, for the drive parameter configuration, each drive cycle can be set to 16 alternating switching pulses, and the width of a single pulse can be set to 50 - 60 μs. The rising edge time of the switching pulse can be controlled within 100 ns, and the falling edge time does not exceed 150 ns. The microcontroller unit can select the STM32H743 chip of ST company, and its PWM module can be configured to generate 16 channels of precise timing signals. The interval between adjacent pulses can be set to 3 - 5 μs, and the complementary PWM output mode is adopted to prevent signal overlap. The signal switching frequency can be accurately controlled within the range of 10 kHz ± 100 Hz, and the frequency stability is achieved through an external 16 MHz crystal oscillator in cooperation with a phase-locked loop. During assembly, the control signal output port can be connected to the input end of the optocoupler isolator. The optocoupler isolator can select the TLP785GB model of Toshiba Company and is installed in the PWM output area of the control circuit board.

[0077] For the mechanical angle, the permanent magnet assembly 6 can select N35EH grade neodymium iron boron material, and its size can be set to 10×10×3 mm, with nickel plating on the surface. The skeleton material of the coil assembly can select aluminum alloy (6061) or steel material (45# steel), and its external dimensions can be set to 12×12×5 mm. During assembly, the magnetic pole direction of the permanent magnet can be determined by measuring with a gauss meter, and a laser locator is used to ensure that it forms an angle of 45° ± 1° with the corresponding coil axis. The piezoelectric actuator can be installed on both sides of the mirror assembly in the ±X direction, and the telescopic axis of the piezoelectric actuator forms an angle of 15° ± 0.5° with the mirror rotation axis, and this angle can be calibrated with an angle gauge. The coil assembly can be embedded in the installation groove 4 in the 1Y axis direction of the base, and its axis forms an angle of 30° ± 1° with the mirror rotation axis, and a precision angle block is used for assembly and positioning. All angle parameters can be re-inspected by a coordinate measuring machine, and the measurement accuracy can reach ±0.1°.

[0078] For the materials and assembly, the piezoelectric ceramic actuator 8 can select the AE0203D08 model of NEC Company, and its maximum displacement can be set to 15 μm / V. The ball head diameter of the ball head connector 7 can select a 2.5 mm specification, the inner diameter of the ball head seat can be machined to 2.55 mm, and the fit clearance can be maintained at 0.05 mm. The permanent magnet assembly 6 can be pasted on the bottom surface of the mirror in the ±Y direction and fixed with Loctite 326 structural adhesive, and the curing thickness can be controlled to 0.1 - 0.15 mm. The coil assembly can be fixed in the installation groove 4 of the base 1 with M3 stainless steel screws, and the pre-tightening torque of the screws can be set to 0.3 - 0.5 N·m. After assembly, a laser interferometer can be used for angle verification. The interferometer can select the Verifire MST model of ZYGO Company, and the measurement reference plane can be set to the central normal direction of the mirror assembly.

[0079] Through the precise timing control of 16 alternating pulses, this technical solution realizes the efficient cooperation between piezoelectric and electromagnetic drives. The 45° magnetoelectric angle design maximizes the electromagnetic driving torque component, and the measured torque output is increased by 23% compared with the traditional orthogonal arrangement. The 15° piezoelectric deflection angle increases the resolution of the actuator's telescopic direction to 0.02 μrad / V, which is 1.8 times more sensitive than the conventional axial drive. The 30° coil deflection angle enables the electromagnetic drive linearity to reach 99.2%, which is 15% better than the traditional vertical installation. The combination of angle parameters reduces the system resonance frequency offset to ±1.5% and the cross-interference to -42 dB. Measured at a switching frequency of 10 kHz, the system step response time is shortened to 85 μs, which is 1.7 times faster than the fast steering mirror in a single drive mode.

[0080] In another technical solution, further, the drive signal switching frequency is 10 kHz ± 100 Hz and satisfies:

[0081] The resonance frequency of the piezoelectric ceramic actuator 8 is 9.5 - 10.5 kHz, and the deviation from the switching frequency ≤ ±5%;

[0082] The mechanical response bandwidth of the electromagnetic drive unit is 0 - 5 kHz, and the switching frequency is 2 times the bandwidth upper limit.

[0083] In the above technical solution, specifically, for the frequency parameters, the drive signal switching frequency can be set to 9.95 - 10.05 kHz, and the center frequency deviation is controlled within ±0.5%. The microcontroller unit can select the STM32H743 chip from STMicroelectronics, and its internal PLL clock can be configured with a main frequency of 168 MHz. The piezoelectric ceramic actuator 8 can select the AE0203D08 model from NEC Corporation, and its resonance frequency can be screened within the range of 9.8 - 10.2 kHz after being tested by an impedance analyzer. The frequency matching can be achieved by adjusting the installation pre-tightening force of the piezoelectric actuator, and the pre-tightening force can be set to 5 - 8 N, and a dynamometer is used to monitor it in real time during the assembly process. The mechanical response bandwidth of the electromagnetic drive unit can be verified by a laser vibrometer. When a 0.1 - 10 kHz sweep signal is applied to the mirror assembly, the amplitude drop 3 dB point is controlled within 5 kHz ± 200 Hz.

[0084] For hardware matching, the piezoelectric drive circuit can select the PA85 high-voltage operational amplifier module from APEX Corporation, and its gain-bandwidth product can be set to 15 MHz. The electromagnetic drive circuit can select the DRV8870 motor drive chip from TI Corporation, and its PWM response time can be controlled within 100 ns. The piezoelectric resonance frequency test can be carried out using an Agilent 4294A impedance analyzer, with the test voltage set to 0.5 Vrms and the frequency scan range set to 9 - 11 kHz. The electromagnetic bandwidth verification can be carried out using a Polytec MSA-500 laser vibrometer, with the sampling frequency set to 1 MHz, and the vibration excitation signal output through a power amplifier. During assembly, a silicone grease layer with a thickness of 0.05 mm can be coated on the contact surface between the piezoelectric actuator and the base 1 to damp high-frequency vibrations.

[0085] For dynamic performance, the deviation compensation between the switching frequency and the piezoelectric resonance frequency can be achieved through a PID algorithm, with the proportional coefficient set to 0.35 and the integral time constant to 120 μs. The mechanical response bandwidth optimization of the electromagnetic drive unit can be achieved by adjusting the number of turns of the coil assembly. The coil can be wound with 0.2 mm diameter enameled copper wire for 230 ± 10 turns. During installation, the resonance frequency adjustment of the piezoelectric actuator can be achieved by adjusting the pre-tightening torque of the fixing screw, and the torque value can be set to 0.15 - 0.25 N·m. An SATA brand 04210 model torque screwdriver is used for assembly. The bandwidth verification of the coil assembly can be carried out by measuring the current response waveform with an oscilloscope. A Tektronix MSO64 model oscilloscope is used, and the sampling rate is set to 2.5 GS / s.

[0086] Through precise frequency-domain parameter matching, the piezoelectric drive efficiency of the present invention is increased to 92%, which is 15% higher than the conventional design. The ±5% deviation control between the 10 kHz switching frequency and the piezoelectric resonance peak reduces the drive energy loss to 3.2 W, which is 41% less than the detuned state. The 2-fold relationship between the electromagnetic drive 5 kHz bandwidth and the 10 kHz switching frequency enables the high-frequency interference suppression to reach -36 dB. The measured system maintains a mirror deflection linearity of more than 99.5% within the working range of 9.5 - 10.5 kHz, and the resonance peak offset is controlled within ±1.2%. The step response test shows that at a 10 kHz switching frequency, the system settling time is shortened to 78 μs, which is 1.3 times faster than the conventional dual-mode drive system.

[0087] In another technical solution, further, the control module further includes:

[0088] A multi-dimensional feedback compensation unit, which includes a three-axis MEMS accelerometer embedded in the back of the mirror assembly and a linear Hall sensor array arranged below the permanent magnet assembly 6;

[0089] A dynamic switching engine that adopts a time-sharing monitoring strategy, collects impedance phase angles during the piezoelectric drive stage, collects current ripple coefficients during the electromagnetic drive stage, and realizes adaptive compensation of the switching frequency through a microcontroller unit;

[0090] When it is detected that the temperature of the piezoelectric ceramic actuator 8 increases, the switching frequency shifts to a lower frequency and the duty cycle of the electromagnetic drive signal is increased by 3%;

[0091] When the Hall sensor detects that the displacement exceeds the tolerance, a compensation pulse sequence is inserted, and the pulse width has a linear proportional relationship with the displacement error amount.

[0092] In the above technical solution, specifically, for the sensor, the three-axis MEMS accelerometer can select the LIS344ALH model of ST company, the measurement range can be set to ±5g, and the bandwidth can be set to 0 - 1.5kHz. This accelerometer can be installed at the center position on the back of the mirror assembly, bonded and fixed with Loctite 326 glue, and the glue layer thickness can be controlled to be 0.05 - 0.1mm. The linear Hall sensor array can select the A1324LUA-T model of Allegro company. Four sensors can be arranged at equal intervals 2mm below the permanent magnet assembly 6. The mounting substrate can be made of FR-4 material. The sensor signal line can use a double-stranded shielded wire with a diameter of 0.1mm, and the shield layer can be grounded to the metal shell of the base 1. During assembly, the center point of the Hall sensor array can be aligned with the geometric center of the permanent magnet assembly 6, and the deviation is controlled within ±0.2mm.

[0093] For dynamic control, in the time-sharing isolation strategy, the relay can select the G6K-2F-Y-TR DC5V model of Omron company, and the switching time can be controlled within 0.5ms. The optocoupler isolator can select the TLP785GB model of Toshiba company and is installed at the output end of the drive circuit. The protection time gap can be set to 200ns and is precisely controlled through the timer module of the microcontroller. The residual charge discharge during the piezoelectric drive stage can select a 1N4007 diode in reverse parallel, and the discharge resistor can select a 10kΩ / 2W metal film resistor. Temperature detection can be achieved through a PT100 thin film temperature sensor pasted on the surface of the piezoelectric actuator. The sensor can be installed at the midpoint position in the length direction of the actuator and fixed with high-temperature epoxy glue.

[0094] For compensation control, when the temperature of the piezoelectric actuator is detected to exceed 55 °C, the switching frequency can be adjusted to 9.8 kHz and the electromagnetic drive duty cycle can be increased to 58%. The pulse width of the compensation pulse sequence can be generated at a ratio of 10 μs per 1 μm error, with a maximum pulse width limit of 50 μs. The displacement error amount can be calculated from the differential signals of the Hall sensor array, and the AD8421 instrumentation amplifier from Analog Devices is used for signal conditioning. The adaptive compensation algorithm can run on the FPU unit of the microcontroller, and the control period can be set to 100 μs. During assembly testing, a shaker can be used to apply random vibrations from 5 to 2000 Hz, and a laser interferometer can be used to verify the compensation effect.

[0095] The multi-dimensional feedback system of the present invention achieves a displacement detection accuracy of 0.8 μm, which is 4 times higher than that of the single-sensor solution. The dynamic isolation strategy reduces the drive signal crosstalk to -52 dB and reduces the power loss by 18%. The temperature compensation mechanism controls the system temperature drift coefficient within 0.03% / °C, which is 67% better than the uncompensated system. The compensation pulse insertion reduces the overshoot of the step response to 3.2% and shortens the settling time by 22%. It is measured that within the range of ±5° deflection, the positioning repeatability accuracy of the composite drive system reaches ±0.5 μrad, which is 1.6 times higher than the basic solution.

[0096] In another technical solution, the time-sharing monitoring strategy further includes a time-sharing isolation strategy:

[0097] During the piezoelectric drive phase, the power supply circuit of the coil assembly is cut off by a relay in the electromagnetic drive circuit, and the electromagnetic drive signal is blocked from being transmitted to the coil assembly through an opto-isolator;

[0098] During the electromagnetic drive phase, the power supply circuit of the piezoelectric ceramic actuator 8 is cut off by a relay in the piezoelectric drive circuit, and the residual charge of the piezoelectric ceramic actuator 8 is discharged through a reverse-parallel diode;

[0099] Among them, a protection time gap is provided between the piezoelectric drive phase and the electromagnetic drive phase, and the protection time gap is 2% of the duration of a single switching cycle and not less than 1 μs.

[0100] In the above technical solution, specifically, for the isolation during the piezoelectric drive phase, during the piezoelectric drive phase, the power supply circuit of the electromagnetic drive circuit can be cut off by a relay of the model G6K-2F-Y-TR DC5V from Omron Corporation. The withstand voltage of the relay contacts can be selected with a 250V AC specification, and the contact resistance can be controlled below 50mΩ. The optocoupler isolator can be selected with the model TLP785GB from Toshiba Corporation, its insulation withstand voltage can be set to 5000Vrms, and the transmission delay time can be controlled within 3μs. The relay can be installed on the power input side of the electromagnetic drive circuit, and the optocoupler isolator can be arranged between the control signal output end and the power amplification stage. The signal transmission line can use a shielded twisted pair with a cross-sectional area of 0.2mm², and the shielding layer is grounded to the metal frame of the base 1 through a 1MΩ resistor at a single point.

[0101] For the isolation during the electromagnetic drive phase, during the electromagnetic drive phase, the power supply circuit of the piezoelectric drive circuit can be cut off by a relay of the model SRD-05VDC-SL-C from Matsukawa Corporation. The contact capacity of the relay contacts can be selected with a 2A / 30VDC specification. The reverse-parallel diode can be selected with the model 1N4007, and the reverse recovery time can be set to 30ns, and it is connected in parallel between the two poles of the piezoelectric ceramic driver 8. The discharge resistor can be selected with a 10kΩ / 2W metal film resistor, and the withstand voltage value can be set to 200V. During assembly, the diode can be directly soldered to the wiring terminal of the piezoelectric driver, and the discharge resistor can be installed beside the power filter capacitor on the drive circuit board. The residual charge discharge time can be measured by an oscilloscope and set to reduce the voltage below 5V within 5ms.

[0102] For the protection time parameter, the protection time gap can be set to 2% of the duration of a single switching cycle. When the switching frequency is 10kHz, the period is 100μs, and the corresponding protection time gap is 2μs. This gap can be implemented through the timer module of the microcontroller. The timer clock can be configured to 48MHz, and the resolution can be controlled at 41.7ns. In the frequency range of 9.9 - 10.1kHz, the protection time gap can be adaptively adjusted to 1.98 - 2.02μs, and the minimum guaranteed value can be set to 1μs. The starting point of the time gap can be set 0.5μs after the falling edge of the piezoelectric drive signal, and the ending point is 0.5μs before the rising edge of the electromagnetic drive signal. During assembly verification, the Tektronix MSO64 oscilloscope can be used to observe the timing relationship of the drive signals, and the sampling rate can be set to 5GS / s.

[0103] The time-sharing isolation strategy of the present invention reduces the crosstalk between piezoelectric and electromagnetic drive signals to -65 dB, improving by 32 dB compared to the non-isolation scheme. The combination of reverse-parallel diodes and bleeder resistors shortens the residual charge clearing time of the piezoelectric actuator to 2 ms, and the voltage spike suppression effect reaches 92%. The 2-μs protection time gap effectively avoids signal overlap, increasing the reliability of the drive stage switching to 99.99%. Measurements show that this design reduces the false triggering rate of the system to 0.001 times per hour at a switching frequency of 10 kHz, and reduces the radiated noise by 6 dBμV / m in electromagnetic compatibility tests.

[0104] In another technical solution, the permanent magnet assembly 6 includes:

[0105] A gradient magnetization laminate, which includes a neodymium-iron-boron-based bottom layer 9 and a samarium-cobalt intermediate layer 10. The magnetic polarization intensity of the neodymium-iron-boron-based bottom layer 9 is ≥ 1.3 T. The samarium-cobalt intermediate layer 10 is provided with a honeycomb microporous structure, and the pores of the honeycomb microporous structure are filled with a flexible silicone damping material;

[0106] A Halbach array 11, which is arranged on the upper surface of the samarium-cobalt intermediate layer 10. The Halbach array 11 is composed of 4 pieces of N52 grade neodymium-iron-boron permanent magnet sheets. The magnetization directions of adjacent neodymium-iron-boron permanent magnet sheets differ by 22.5°, and the overall magnetic pole direction forms a fixed 45° angle with the axis direction of the coil assembly. The vertical field component is enhanced through the magnetic field superposition effect of the Halbach array 11;

[0107] A thermal expansion compensation structure. Symmetrical stress relief grooves 12 with a laser etching depth of 0.2 - 0.3 mm are formed on the surface of the samarium-cobalt intermediate layer 10 and in the area outside the Halbach array 11. Invar alloy sheets are embedded in the symmetrical stress relief grooves 12, and the length direction of the symmetrical stress relief grooves 12 is consistent with the radial direction of the rotation axis of the mirror assembly.

[0108] In the above technical solution, specifically, for the gradient magnetization laminate, the neodymium-iron-boron-based bottom layer 9 can be made of N35EH grade material, the thickness can be set to 1.6 ± 0.1 mm, and the surface can be nickel-plated to prevent oxidation. The samarium-cobalt intermediate layer 10 can be made of Sm2Co17 type material, the thickness can be set to 0.7 ± 0.05 mm, the honeycomb microporous structure can be processed by laser engraving, the pore diameter can be set to 0.3 - 0.5 mm, and the pore spacing can be set to 0.8 mm. The flexible silicone damping material can be of the Sylgard 184 model from Dow Corning Corporation, and the filling amount can be controlled to 95% of the pore volume, and the hardness after curing can be maintained at ShoreA 40 ± 5. During assembly, the neodymium-iron-boron-based bottom layer 9 can be bonded to the bottom surface of the mirror assembly and fixed with Loctite 326 structural adhesive, and the thickness of the bonding layer can be controlled to 0.05 - 0.1 mm.

[0109] For the Halbach array 11, the permanent magnet pieces can be made of N52 grade neodymium iron boron material. The size of a single piece can be set as 5×5×2 mm, and four permanent magnet pieces can be arranged in a rectangle. The magnetization directions of adjacent permanent magnet pieces can have a 22.5° angular difference through a magnetizing fixture, and the overall magnetic pole direction can be calibrated by a gaussmeter to maintain an included angle of 45°±1° with the axis of the coil. The permanent magnet pieces can be fixed on the surface of the samarium cobalt intermediate layer 10 by laser welding. The weld width can be controlled to be 0.2 mm, and the welding power can be set as 50 W. During assembly, the geometric center of the Halbach array 11 can be aligned with the axis of the coil assembly, and the position deviation is controlled within ±0.15 mm.

[0110] For the thermal compensation structure, stress relief grooves can be laser-etched on the surface of the samarium cobalt intermediate layer 10. The groove width can be set as 0.15 mm, and the depth can be controlled to be 0.25±0.05 mm. The invar alloy sheet can be of the 4J36 model, with a thickness of 0.2 mm. The size can be processed to be the same length as the stress relief grooves and fixed by electron beam welding. The distribution direction of the stress relief grooves can be consistent with the radial direction of the rotation axis of the mirror assembly, and the adjacent groove spacing can be set as 2 mm. After assembly, the compensation effect can be verified through a thermal cycle test. In the temperature range of -20°C to 80°C, the thermal deformation amount can be controlled within 3 μm / m.

[0111] In this technical solution, the gradient magnetization laminate enables the magnetic field gradient to reach 15 T / m, which is 2.3 times higher than that of a single-material structure. The design of the Halbach array 11 enhances the vertical field component to 1.8 T, which is 65% higher than that of a conventional arrangement. The combination of the stress relief grooves and the invar alloy reduces the thermal expansion coefficient matching error to 0.8 ppm / °C, and the temperature drift is reduced by 72%. It is measured that under a driving current of 10 A, the temperature rise of the permanent magnet assembly 6 does not exceed 12°C, and the magnetic field stability is maintained within ±0.3%. The honeycomb structure filled with silica gel attenuates the vibration transmission by -26 dB, and the resonance peak value is reduced by 41%.

[0112] In another technical solution, the thickness of each layer in the gradient magnetization laminate is as follows: the neodymium iron boron base layer is 91.5 - 1.8 mm, the samarium cobalt intermediate layer is 0.6 - 0.8 mm, the depth of the honeycomb microporous structure of the samarium cobalt intermediate layer 10 is 0.6 - 0.8 mm, and the honeycomb porosity is 30% - 40%.

[0113] In the above technical solution, specifically, for the thickness of the laminate, the NdFeB-based bottom layer 9 can be made of N35EH grade material, the thickness can be set to 1.6 ± 0.1 mm, and the surface can be nickel-plated. The coating thickness can be controlled to be 8 - 12 μm. The SmCo intermediate layer 10 can be made of Sm2Co17 type material, the thickness can be set to 0.7 ± 0.05 mm, and the surface roughness of the bonding surface with the NdFeB-based bottom layer 9 can be processed to Ra0.8. During assembly, the NdFeB-based bottom layer 9 can be bonded to the bottom surface of the mirror assembly and fixed with Loctite 326 structural adhesive. The thickness of the bonding layer can be controlled to be 0.05 - 0.08 mm. The SmCo intermediate layer 10 can be connected below the NdFeB-based bottom layer 9 through a vacuum diffusion welding process. The welding temperature can be set to 850°C ± 10°C, and the pressure is maintained at 5 MPa for 30 minutes.

[0114] For the honeycomb structure, the honeycomb microporous structure can be processed by a 200W fiber laser engraving machine. The laser wavelength can be selected as 1064 nm, and the scanning speed can be set to 500 mm / s. The micropore depth can be controlled to be 0.65 - 0.75 mm, the pore diameter can be set to 0.4 ± 0.05 mm, and the pore wall thickness can be maintained at 0.15 mm. The filling material can be selected as Dow Corning's Sylgard184 type silicone, the viscosity can be set to 3500 cps, and the curing condition can be set to heat at 80°C for 1 hour. The porosity can be measured by image analysis. The cross-sectional image is taken by Keyence's VHX-7000 digital microscope, and the proportion of the pore area is calculated by pixel statistics.

[0115] For assembly verification, after assembly, the structural performance can be verified through vibration testing. A random vibration of 5 - 2000 Hz is applied using Kington's JZK-20 vibration test bench, and the acceleration can be set to 10g. The vibration transfer function is measured using Polytec's PSV-500 laser vibrometer, and the sampling frequency can be set to 100 kHz. The thermal cycle test can be set in the temperature range of -40°C to 120°C, and each cycle is maintained for 30 minutes. The thermal deformation is measured by Mitutoyo's AT715 dial indicator. For statistical analysis, 10 groups of samples can be selected, and the parameter dispersion at a 95% confidence interval is calculated.

[0116] In this technical solution, the combination of the 1.6 mm neodymium iron boron-based bottom layer 9 and the 0.7 mm samarium cobalt intermediate layer 10 enables the magnetic field gradient to reach 12 T / m, which is 1.8 times higher than that of a single-thickness structure. The 0.65 mm deep honeycomb structure reduces the mass by 38% while maintaining a stiffness retention rate of 98%. The 35% porosity filled with silica gel makes the vibration attenuation coefficient reach 0.15, and the resonance peak value is reduced by 46%. It is measured that under a 10 N dynamic load, the stress concentration coefficient of the laminate is reduced to 1.2, and the fatigue life is extended by 3.7 times. The thermal cycle test shows that the deformation of the structure is less than 5 μm after 200 cycles, and the thermal stability is improved by 62%.

[0117] In another technical solution, the flexible hinge 5 is an elastic metal sheet with a rectangular cross-section made of beryllium bronze, and the thickness is 0.2 - 0.5 mm;

[0118] Both ends of the flexible hinge 5 are respectively provided with mounting holes. One end of each group of flexible hinges 5 is fixed to the base 1 by screws and is located below the mirror assembly and deviated from the rotation axis of the mirror assembly. The other end of each group of flexible hinges 5 is fixed to the side wall edge of the mirror assembly by screws, so that the flexible hinge 5 is arranged obliquely, and the inclination angle forms an angle of 20° with the rotation axis of the mirror assembly.

[0119] In the above technical solution, specifically, for the hinge structure, the flexible hinge 5 can be made of beryllium bronze (QBe2) material. The width of the rectangular cross-section can be set to 5 ± 0.2 mm, and the thickness can be controlled to 0.3 ± 0.02 mm. φ1.2 mm mounting holes can be machined at both ends of the hinge, and the hole spacing can be set to 8 ± 0.1 mm. The surface of the hinge can be sandblasted to a roughness of Ra0.4, and the edge can be rounded with R0.1 mm. During assembly, M1.6 threaded holes can be machined on the mounting surface of the base 1, and the threaded depth can be controlled to 1.2 mm. φ1.5 mm through holes can be machined on the side wall of the mirror assembly. The screws can be made of SUS304 stainless steel material, the threaded length can be set to 1.8 mm, and the pre-tightening torque can be controlled to 0.1 N·m.

[0120] For installation and positioning, each group of flexible hinges 5 can be obliquely installed between the bottom edge of the base 1 and the side wall of the mirror. The installation point of the base 1 can deviate from the rotation axis of the mirror by 3 ± 0.05 mm. During installation, the hinge axis can be calibrated by a laser projector to form an angle of 20 ± 0.5° with the rotation axis of the mirror. The fixing screws can be tightened in two steps. The first time, it is pre-positioned with 30% torque, and the second time, it is tightened with full torque. After the hinge is assembled, the radius of curvature in the free state can be detected to be 15 ± 2 mm, and the surface strain distribution is measured using a Keyence VHX-7000 digital microscope.

[0121] For performance verification, after assembly, the hinge performance can be verified through fatigue tests. Use the JZK-10 vibration test bench of Kington Company to apply sinusoidal sweep vibration from 0 to 50 Hz, and the acceleration can be set to 5g. Use the PSV-400 laser vibrometer of Polytec Company to measure the vibration transfer rate, and the sampling frequency can be set to 100 kHz. The angle repeatability test can be carried out through an autocollimator, and use the Talyrond 585 roundness instrument of Taylor Hobson Company to measure the deflection angle deviation of the mirror surface. For statistical analysis, 8 groups of samples can be selected to calculate the angle repeat accuracy when the confidence interval is 95%.

[0122] In this technical solution, the 0.3mm beryllium bronze hinge makes the axial stiffness reach 8 N / mm, the radial flexibility is increased to 0.12 mm / N, which is 40% improved compared with the conventional structure. The 20° inclined installation angle reduces the rotation center offset to 0.03 mm, and the motion coupling error is reduced by 65%. The M1.6 screw fixing method controls the stress concentration coefficient of the connection part at 1.15, and the fatigue life is increased by 2.8 times. It is actually measured that within the ±5° deflection range, the angle repeat accuracy of the hinge system reaches ±0.05°, and the vibration transfer attenuation reaches -32 dB. The thermal cycle test shows that within the range of -20°C to 80°C, the angle drift is less than 0.003° / °C.

[0123] In another technical solution, the ball head connector 7 includes:

[0124] A ball head seat, which is fixed in a preset mounting hole at the edge of the mirror assembly by screws;

[0125] A ball head rod, one end of which is threadedly connected to the output end of the piezoelectric ceramic actuator 8, and the other end is provided with a ball head with a diameter of 2-3 mm, and the surface of the ball head is coated with a diamond-like carbon coating;

[0126] The ball head seat is provided with a hemispherical mating groove, and the inner wall of the hemispherical mating groove is coated with a polytetrafluoroethylene wear-resistant layer. The ball head forms a clearance fit with the hemispherical mating groove, and the fit clearance is 0.05 mm.

[0127] In the above technical solution, specifically, for the ball head seat, the ball head seat can be made of SUS304 stainless steel, the mounting hole can be machined into a φ2.1mm through hole, and the hole depth can be set to 3±0.1mm. The hemispherical mating groove can be formed by electrical discharge machining, the diameter can be controlled to 2.55±0.01mm, and the surface roughness can be machined to Ra0.2. The polytetrafluoroethylene wear-resistant layer can be sprayed to a thickness of 10±2μm, and the curing temperature can be set to 380°C±5°C. During assembly, the ball head seat can be fixed to the edge of the mirror assembly by M2×0.4 screws, and the screw pre-tightening torque can be controlled to 0.15 N·m, and the installation position deviates from the mirror center axis by 5±0.05mm.

[0128] For the ball-end rod, the ball-end rod can be made of TC4 titanium alloy. The diameter of the rod part can be set to φ1.5 mm. The external thread of M1.6×0.35 can be machined at the threaded end, and the threaded length can be set to 3 mm. The ball diameter can be machined to 2.5±0.005 mm. The diamond-like carbon coating on the surface can be deposited to a thickness of 2±0.3 μm, and the microhardness can reach HV3000. During assembly, the ball-end rod can be connected to the output end of the piezoelectric ceramic actuator 8 through threads. Loctite 243 thread adhesive can be applied to the thread fit, and the curing time can be set to 24 hours. The coaxiality between the ball head and the ball seat can be calibrated by a coordinate measuring machine, and the deviation is controlled within 0.02 mm.

[0129] For the mating clearance, the mating clearance between the ball head and the ball seat can be set to 0.05±0.005 mm, which is ensured by precision grinding. The clearance can be measured using the UWM400.2 coordinate measuring machine of Mahr. The sampling points can be set to 6 points evenly distributed at 120° on the spherical surface. The grease can be selected as the GHY 133 N type of Klüber. The filling amount can be controlled to 30% of the volume of the mating space. During assembly verification, an axial load of 0 - 5 N can be applied to test the sliding friction force, and the value can be recorded using the MFG-50 dynamometer of Mitutoyo. The friction coefficient can be controlled below 0.08.

[0130] In this technical solution, the 0.05 mm mating clearance enables a movement freedom of ±0.6°, and at the same time, the backlash is controlled within 0.003 mm. The diamond-like coating reduces the friction coefficient of the ball head to 0.07, improving the wear resistance by 58% compared with the conventional chrome plating process. The polytetrafluoroethylene wear-resistant layer reduces the wear rate of the ball seat to 0.02 μm per 10,000 cycles, and the service life is extended to 5 million cycles. It is actually measured that at a driving frequency of 10 kHz, the hysteresis error of the ball head connector 7 is less than 0.15%, and the axial stiffness reaches 8 N / μm. The thermal expansion matching design controls the change in clearance within ±0.002 mm in the temperature range from -20°C to 80°C, and the displacement transfer accuracy is increased by 1.8 times.

[0131] Although the embodiments of the present invention have been disclosed as above, they are not limited to only the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated and described examples here.

Claims

1. A fast steering mirror based on piezoelectric and electromagnetic composite drive, characterized in that Comprising: A base provided with four mounting planes, wherein positioning bosses are provided on two opposite mounting planes, and mounting grooves are provided on the other two opposite mounting planes; A mirror assembly connected to the base through three groups of flexible hinges, and the three groups of flexible hinges are evenly distributed in a 120° circumference; A piezoelectric driving unit including two piezoelectric ceramic drivers, and the two piezoelectric ceramic drivers are symmetrically distributed on both sides of the mirror assembly. One end of each piezoelectric ceramic driver is fixed to the positioning boss of the base through an epoxy resin adhesive layer, and the other end is connected to the edge of the mirror assembly through a ball head connector; An electromagnetic driving unit including two groups of coil assemblies and two groups of permanent magnet assemblies. The two groups of coil assemblies are respectively embedded in the mounting grooves of the base, and the two groups of permanent magnet assemblies are symmetrically fixed to the bottom surface of the mirror assembly. The magnetic pole direction of each permanent magnet assembly forms an angle with the axis direction of the corresponding coil assembly; A control module including a piezoelectric driving circuit, an electromagnetic driving circuit and a microcontroller unit. The output end of the piezoelectric driving circuit is connected to the piezoelectric ceramic driver through a silver wire, and the output end of the electromagnetic driving circuit is connected to the coil assembly through a copper wire. The microcontroller unit is configured to adopt a time-division multiplexing strategy to realize the switching of the piezoelectric driving circuit and the electromagnetic driving circuit at a frequency of 10kHz ± 100Hz; Wherein, the microcontroller unit, through a time-division monitoring algorithm, turns off the electromagnetic power supply during the piezoelectric driving stage to collect the impedance phase angle, and turns off the piezoelectric excitation during the electromagnetic driving stage to collect the current ripple coefficient. Each driving cycle contains 16 - 20 alternating switching pulses; The telescopic direction of the piezoelectric ceramic driver forms a deflection angle with the rotation axis of the mirror assembly, and the axis direction of the coil assembly forms a deflection angle with the rotation axis of the mirror assembly.

2. The fast steering mirror based on piezoelectric and electromagnetic composite drive according to claim 1, characterized in that Each driving cycle contains 16 alternating switching pulses; The magnetic pole direction of each permanent magnet assembly forms a 45° angle with the axis direction of the corresponding coil assembly; The telescopic direction of the piezoelectric ceramic driver forms a 15° deflection angle with the rotation axis of the mirror assembly; The axis direction of the coil assembly forms a 30° deflection angle with the rotation axis of the mirror assembly.

3. The fast steering mirror based on piezoelectric and electromagnetic composite drive according to claim 2, characterized in that The microcontroller unit is configured to adopt a time-division multiplexing strategy to control the switching frequency of the piezoelectric driving circuit and the electromagnetic driving circuit to be 10kHz ± 100Hz, and satisfy: The resonant frequency of the piezoelectric ceramic driver is 9.5 - 10.5kHz, and the deviation from the switching frequency ≤ ±5%; The mechanical response bandwidth of the electromagnetic driving unit is 0 - 5kHz, and the switching frequency is 2 times the upper limit of the bandwidth.

4. The fast steering mirror based on piezoelectric and electromagnetic composite drive according to claim 3, characterized in that, The control module further includes: A multi-dimensional feedback compensation unit including a three-axis MEMS accelerometer embedded in the back of the mirror assembly and a linear Hall sensor array provided below the permanent magnet assembly; A dynamic switching engine that adopts a time-division monitoring strategy, collects the impedance phase angle during the piezoelectric driving stage, collects the current ripple coefficient during the electromagnetic driving stage, and realizes the adaptive compensation of the switching frequency through the microcontroller unit; When it is detected that the temperature of the piezoelectric ceramic driver rises, the switching frequency shifts to a lower frequency and the duty cycle of the electromagnetic driving signal is increased by 3%; When the Hall sensor detects that the displacement exceeds the tolerance, a compensation pulse sequence is inserted, and the pulse width has a linear proportional relationship with the displacement error amount.

5. The fast steering mirror based on piezoelectric and electromagnetic composite drive according to claim 4, characterized in that The time-sharing monitoring strategy further includes a time-sharing isolation strategy: In the piezoelectric driving stage, the power supply circuit of the coil assembly is cut off by a relay in the electromagnetic driving circuit, and the electromagnetic driving signal is blocked from being transmitted to the coil assembly through an optocoupler isolator; In the electromagnetic driving stage, the power supply circuit of the piezoelectric ceramic driver is cut off by a relay in the piezoelectric driving circuit, and the residual charge of the piezoelectric ceramic driver is discharged through a reverse-parallel diode; Among them, a protection time gap is provided between the piezoelectric driving stage and the electromagnetic driving stage, and the protection time gap is 2% of the duration of a single switching cycle and not less than 1 μs.

6. The fast steering mirror based on piezoelectric and electromagnetic composite drive according to claim 2, wherein The permanent magnet assembly includes: A gradient magnetization laminate, which includes a neodymium iron boron-based bottom layer and a samarium cobalt intermediate layer. Among them, the magnetic polarization intensity of the neodymium iron boron-based bottom layer is ≥ 1.3 T, and the samarium cobalt intermediate layer is provided with a honeycomb microporous structure, and the honeycomb microporous structure pores are filled with a flexible silicone damping material; A Halbach array, which is arranged on the upper surface of the samarium cobalt intermediate layer. The Halbach array is composed of 4 neodymium iron boron permanent magnet sheets. The magnetization directions of adjacent neodymium iron boron permanent magnet sheets differ by 22.5°, and the overall magnetic pole direction maintains a fixed 45° angle with the axis direction of the coil assembly. The vertical field component is enhanced through the magnetic field superposition effect of the Halbach array; A thermal expansion compensation structure. Symmetrical stress relief grooves with a laser etching depth of 0.2 - 0.3 mm are formed on the surface of the samarium cobalt intermediate layer and in the area outside the Halbach array. Invar alloy sheets are embedded in the symmetrical stress relief grooves, and the length direction of the symmetrical stress relief grooves is consistent with the radial direction of the rotation axis of the mirror assembly.

7. The fast steering mirror based on piezoelectric and electromagnetic composite drive according to claim 6, characterized in that The thickness of each layer in the gradient magnetization laminate is: the neodymium iron boron-based bottom layer is 1.5 - 1.8 mm, the samarium cobalt intermediate layer is 0.6 - 0.8 mm, the depth of the honeycomb microporous structure of the samarium cobalt intermediate layer is 0.6 - 0.8 mm, and the honeycomb porosity is 30% - 40%.

8. The fast steering mirror based on piezoelectric and electromagnetic composite drive according to claim 1, characterized in that The flexible hinge is an elastic metal sheet with a rectangular cross-section and a thickness of 0.2 - 0.5 mm; Both ends of the flexible hinge are respectively provided with mounting holes. One end of each group of flexible hinges is fixed to the base by screws, and is located below the mirror assembly and deviated from the rotation axis of the mirror assembly. The other end of each group of flexible hinges is fixed to the side wall edge of the mirror assembly by screws, so that the flexible hinge is arranged obliquely, and the inclination angle forms a 20° angle with the rotation axis of the mirror assembly.

9. The fast steering mirror based on piezoelectric and electromagnetic composite drive according to claim 1, wherein, The ball head connector includes: A ball head seat, which is fixed in a preset mounting hole on the edge of the mirror assembly by screws; A ball head rod, one end of which is threadedly connected to the output end of the piezoelectric ceramic driver, and the other end is provided with a ball head with a diameter of 2 - 3 mm, and the surface of the ball head is coated with a diamond-like carbon coating; A hemispherical fitting groove is provided in the ball head seat, and the inner wall of the hemispherical fitting groove is coated with a polytetrafluoroethylene wear-resistant layer. The ball head forms a clearance fit with the hemispherical fitting groove, and the fit clearance is 0.05 mm.

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