Fast mirror high-bandwidth driving method and system based on diagonal motor vector control

Abstract

The application discloses a fast mirror high-bandwidth driving method and system based on diagonal motor vector control, and belongs to the technical field of precise optical control. Two pairs of voice coil motor coils are connected in series to form two pairs of independent control pairs, and a push-pull resultant force is realized through current direction control; an eddy current sensor detects the deflection angles of X and Y axes respectively, signals are sent into a controller for real-time processing, the posture of a mirror holder is fed back in real time, and a closed-loop control is formed; the controller generates a torque instruction according to a target angle instruction, after synthesis, a PWM signal is output to drive the motor; through the diagonal layout and the torque synthesis control strategy, the deflection of the X and Y axes is driven by four motors, and high-bandwidth, low-crosstalk and high-precision double-axis motion control is realized.

Description

Technical Field

[0001] This invention relates to the field of precision optical control technology, and is particularly applicable to the high-bandwidth drive control of dual-axis fast-reflecting mirrors in laser communication, adaptive optics systems, astronomical telescope tracking systems, and precision alignment systems of photolithography equipment. It can achieve high-precision dynamic attitude adjustment and is especially suitable for scenarios with high requirements for system compactness, anti-interference, and redundancy reliability. It is a high-bandwidth drive method and system for fast-reflecting mirrors based on diagonal motor vector control. Background Technology

[0002] In precision optical systems, the fast-reflecting mirror (FRMirror) is a core actuator; its response speed and control precision directly determine the system performance. Current mainstream designs suffer from the following key drawbacks:

[0003] like Figure 1 As shown, the X-axis and Y-axis voice coil motors and eddy current sensors are arranged in both horizontal and vertical directions, which has the following drawbacks:

[0004] The motors and sensors are arranged independently along a 90° orthogonal direction. Each set of motor control pairs completes its work independently, controlling the deflection of its own axis. Since the motors and sensors are arranged along the X and Y axes, independent installation space needs to be reserved for each axis, resulting in an increase of more than 30% in the overall size of the mirror body and base, making it difficult to adapt to miniaturized optical systems.

[0005] With the same base size, the physical distance between the motor and the sensor is close in a 90° layout. The alternating magnetic field of the motor during operation can easily interfere with the sensor signal, especially the eddy current field of the eddy current sensor, which leads to increased detection noise. At the same time, mechanical vibration can easily cause resonant coupling when transmitted in orthogonal directions, which further deteriorates the detection accuracy.

[0006] like Figure 2 The rectangular, same-side output layout of the four motors shown has the following defects:

[0007] Single-axis motion relies on the coordinated drive of two motors on the same side (e.g., the Y-axis requires two motors M3 and M4 on the left side to output force in opposite directions, and the X-axis requires two motors M1 and M2 on the right side to output force in the same direction), which causes the equivalent control lever arm to be shortened to 60%-70% of its original length, limiting the system stiffness and making it prone to low-frequency resonance.

[0008] The motor's output direction is at a 45° angle to the target's motion axis. Control commands need to be decoupled through complex coordinate transformations, which introduces phase delay and directly limits the system bandwidth.

[0009] Non-orthogonal force output directions cause mutual interference between X-axis and Y-axis motions, which can easily lead to attitude instability under high-frequency operating conditions.

[0010] If the bandwidth response index of one axis is to be increased, the above two solutions have obvious limitations. Increasing the motor power will lead to heat accumulation, and a 1°C increase in mirror temperature can introduce more than 5μrad of thermal drift. Reducing the inertia will sacrifice the rigidity of the mirror. Although the complex feedforward compensation algorithm can partially alleviate the delay, it will increase the controller's computational load by more than 30%, making it difficult to meet the microsecond-level response requirements.

[0011] In summary, a new technical solution is needed to address the technical problems existing in the above-mentioned layout scheme. Summary of the Invention

[0012] This invention relates to a high-bandwidth drive method and system for fast-reflecting mirrors based on diagonal motor vector control, aiming to solve the technical problems existing in traditional dual-axis fast-reflecting mirror drive systems, such as shortened lever arm, large control delay, severe inter-axis coupling, significant electromagnetic interference, and limited system bandwidth.

[0013] A high-bandwidth drive method for fast-reflecting mirrors based on diagonal motor vector control includes:

[0014] System layout and wiring: The voice coil motors distributed at the four corners of the fast reflector base are divided into two control pairs, FA and FB, according to the diagonal. The negative terminals of the two voice coil motors in each control pair are connected, and the current flows in from the positive terminal on one side and flows out from the positive terminal on the other side, forming a push-pull couple.

[0015] Four eddy current sensors are distributed at the midpoints of the four sides of the fast-reflecting mirror base, and are marked as X+, X-, Y+ and Y- respectively. They are used to sense the deflection of the mirror support in the X-axis and Y-axis directions and transmit the data to the controller.

[0016] Closed-loop control process: The controller initiates a real-time closed-loop cycle, executing the following steps sequentially within each cycle to ensure dynamic response and control accuracy:

[0017] a. Command Reception: The controller receives the target angle command sent by the host computer through the RS422 interface. The command format is (θ, φ), where θ is the target deflection angle on the X-axis and φ is the target deflection angle on the Y-axis. The command update frequency is fixed at 5kHz.

[0018] b. Feedback Acquisition: The four eddy current sensors output acquisition signals, which are differentially amplified and received by the controller. After that, they are digitally filtered to obtain the actual deflection angles (α, β) of the mirror support on the X and Y axes.

[0019] c. Torque command generation: Compare the target angle (θ,φ) with the actual angle (α,β) to calculate the X-axis angle deviation ΔX=θ-α and the Y-axis angle deviation ΔY=φ-β;

[0020] ΔX and ΔY are input into the preset position loop PID of the controller, and through proportional P, integral I, and derivative D operations, they are converted into "X-axis target torque Tx" and "Y-axis target torque Ty" required to achieve angle correction.

[0021] d. Output command synthesis and PWM control:

[0022] Output synthesis: The component force commands of the same control pair are superimposed to obtain the total output force command of the FA control pair FA=Tx+Ty, and the total output force command of the FB control pair FB=Tx-Ty;

[0023] PWM Conversion: Converts the control pairs FA and FB into PWM signals with adjustable duty cycles. The signal frequency is fixed at 100kHz. The duty cycle is positively correlated with the output command size. The greater the output demand, the higher the PWM duty cycle.

[0024] Signal amplification and driving: After the PWM signal is amplified by the motor drive circuit, it is input into the motor circuits controlling FA and FB respectively, driving the motor to generate a push-pull couple, which drives the mirror holder and the optical mirror to deflect.

[0025] e. Real-time closed-loop iteration: During the deflection process, the eddy current sensor continuously collects the mirror holder attitude signal and feeds it back to the controller to enter the next cycle. Steps bd are repeated until the deviation between the actual angle of the mirror holder and the target angle is less than the allowable threshold, so as to achieve dynamic stable control.

[0026] Furthermore, before implementing the closed-loop control process, the following steps are required:

[0027] Setting the positive direction of control: Establish a Cartesian coordinate system based on the positions of the four eddy current sensors. The positive direction of control for FA is defined by the positive output of the voice coil motor in the first quadrant and the reverse output of the voice coil motor in the third quadrant. The positive direction of control for FB is defined by the reverse output of the voice coil motor in the second quadrant and the positive output of the voice coil motor in the fourth quadrant.

[0028] Furthermore, the system includes an optical mirror, a mirror holder, a voice coil motor, a flexible shaft system, a shaft system adapter, a quick-reflecting mirror base, an eddy current sensor, and a controller;

[0029] The optical mirror is fixedly mounted on the mirror holder, and the four voice coil motors are respectively located between the four corners of the mirror holder and the quick-reflecting mirror base. The magnetic cylinder of each voice coil motor is fixedly connected to one corner of the mirror holder, and the coil of each voice coil motor is fixedly connected to one corner of the quick-reflecting mirror base.

[0030] The four voice coil motors are divided diagonally to form two control pairs FA and FB. The negative terminals of the two voice coil motors in each control pair are connected. Current flows in from the positive terminal on one side and flows out from the positive terminal on the other side, forming a push-pull couple to provide driving force for the deflection of the mirror holder.

[0031] One end of the flexible shaft system is rotatably connected to the four sides of the mirror holder, providing the mirror holder with rotational freedom in the X and Y axes, and the other end is fixedly connected to the middle of the quick-reflecting mirror base through the shaft system adapter.

[0032] The four eddy current sensors are distributed at the midpoints of the four sides of the fast-reflecting mirror base, and are marked as X+, X-, Y+ and Y- respectively. They are used to sense the deflection of the mirror support in the X-axis and Y-axis directions and transmit the data to the controller.

[0033] Furthermore, the distance between adjacent voice coil motors is 100mm.

[0034] Furthermore, the controller uses a Xilinx Kintex-7 FPGA as its control core.

[0035] Furthermore, the eddy current sensor is model CS-1000.

[0036] Beneficial effects:

[0037] This invention effectively solves the problems of shortened lever arm, large delay, and severe coupling in traditional layouts by using diagonal grouping of motors and vector control strategy, significantly improving the dynamic response performance and multi-axis coordination capability of fast-reflecting mirrors, and is particularly suitable for high-bandwidth, high-precision optical control systems. Attached Figure Description

[0038] Figure 1 This is a layout diagram showing the X-axis and Y-axis voice coil motors and eddy current sensors, both along the horizontal and vertical directions.

[0039] Figure 2 This is a diagram showing the rectangular output layout of four motors on the same side.

[0040] Figure 3 This is a layout diagram of the present invention based on diagonal motor vector control.

[0041] Figure 4 This is a schematic diagram of the system structure of the present invention.

[0042] Figure 5 This is a flowchart of the control method of the present invention.

[0043] In the figure, 1-optical mirror, 2-mirror holder, 3-voice coil motor, 4-flexible shaft system, 5-shaft system adapter, 6-fast-reflecting mirror base, 7-eddy current sensor. Detailed Implementation

[0044] like Figures 3-5 As shown, the fast-reflecting mirror high-bandwidth driving method based on diagonal motor vector control is characterized by comprising:

[0045] System layout and wiring: The voice coil motors 3 distributed at the four corners of the fast reflector base 6 are divided into two control pairs, FA and FB, along the diagonal. The negative terminals of the two voice coil motors 3 in each control pair are connected together, and the current flows in from the positive terminal on one side and out from the positive terminal on the other side. Based on this wiring method, when current flows, there must be one voice coil motor 3 in each control pair that outputs force in the positive direction and the other voice coil motor 3 that outputs force in the reverse direction, forming a push-pull couple. Real-time current signals can also be collected by connecting 0.1Ω sampling resistors in series in the control pairs FA and FB, and fed back to the sampling interface of the controller to monitor and avoid torque attenuation caused by motor heat accumulation, and ensure the accuracy of torque commands.

[0046] Figure 3 The diagram shows that the control pair FA is composed of voice coil motors 3 designated M1 and M3, and the control pair FB is composed of voice coil motors 3 designated M2 and M4.

[0047] Four eddy current sensors 7 are distributed at the midpoints of the four sides of the fast-reflecting mirror base 6, and are marked as X+, X-, Y+ and Y- respectively. They are used to sense the deflection of the mirror holder 2 in the X-axis and Y-axis directions and transmit the data to the controller.

[0048] Setting the positive direction of control: Establish a Cartesian coordinate system based on the positions of the four eddy current sensors 7. The positive direction of control for FA is defined by the positive output of the voice coil motor 3 (code M1) located in the first quadrant and the reverse output of the voice coil motor 3 (code M3) located in the third quadrant. The positive direction of control for FB is defined by the reverse output of the voice coil motor 3 (code M2) located in the second quadrant and the positive output of the voice coil motor 3 (code M4) located in the fourth quadrant.

[0049] Closed-loop control process: The controller initiates a real-time closed-loop cycle, executing the following steps sequentially within each cycle to ensure dynamic response and control accuracy:

[0050] a. Command Reception: The controller receives the target angle command sent by the host computer through the RS422 interface. The command format is (θ, φ), where θ is the target deflection angle on the X-axis and φ is the target deflection angle on the Y-axis. The command update frequency is fixed at 5kHz.

[0051] b. Feedback acquisition: The four eddy current sensors 7 output acquisition signals, which are differentially amplified and received by the controller. After that, they are digitally filtered to obtain the actual deflection angles (α, β) of the mirror on the X and Y axes.

[0052] c. Torque command generation: Compare the target angle (θ,φ) with the actual angle (α,β) to calculate the X-axis angle deviation ΔX=θ-α and the Y-axis angle deviation ΔY=φ-β;

[0053] ΔX and ΔY are input into the preset position loop PID in the controller, and through proportional P, integral I, and derivative D operations, they are converted into "X-axis target torque Tx" and "Y-axis target torque Ty" required to achieve angle correction.

[0054] In the torque command generation step, the X-axis PID torque calculation process is as follows:

[0055] To control the sampling period, k=0,1,2,3,…, the proportional term, integral term, and differential term are calculated sequentially:

[0056] Proportional term: , For proportional parameters, The angle deviation at time k;

[0057] Integral term: , Let be the angle deviation at time j, where j ranges from 0 to k. The integration parameters are defined; the integration is performed using a summation method, and an integration limit is added to prevent integration saturation. , The maximum value of the integral term. This is the minimum value of the integral term;

[0058] Differential term: , For differential parameters;

[0059] X-axis torque: ;

[0060] Correspondingly, the Y-axis PID torque calculation process is as follows:

[0061] Differential term: , For differential parameters;

[0062] Integral term: , Let be the angle deviation at time j, where j ranges from 0 to k. The integration parameters are defined; the integration is performed using a summation method, and an integration limit is added to prevent integration saturation. , The maximum value of the integral term. This is the minimum value of the integral term;

[0063] Differential term: , For differential parameters;

[0064] Y-axis torque: ;

[0065] d. Output command synthesis and PWM control:

[0066] Output synthesis: The component force commands of the same control pair are superimposed to obtain the total output force command of the FA control pair FA=Tx+Ty, and the total output force command of the FB control pair FB=Tx-Ty;

[0067] PWM Conversion: Converts the control pairs FA and FB into PWM signals with adjustable duty cycles. The signal frequency is fixed at 100kHz. The duty cycle is positively correlated with the output command size. The greater the output demand, the higher the PWM duty cycle.

[0068] Signal amplification and driving: After the PWM signal is amplified by the motor drive circuit, it is input into the motor circuits of FA and FB respectively to drive the motor to generate a push-pull couple, which drives the mirror drag 2 and the optical mirror 1 to deflect.

[0069] e. Real-time closed-loop iteration: During the deflection process, the eddy current sensor continuously collects the mirror holder attitude signal and feeds it back to the controller to enter the next cycle. Steps bd are repeated until the deviation between the actual angle of the mirror holder 2 and the target angle is less than the allowable threshold, so as to achieve dynamic stable control.

[0070] Furthermore, the system includes an optical mirror 1, a mirror holder 2, a voice coil motor 3, a flexible shaft system 4, a shaft system adapter 5, a quick-reflecting mirror base 6, an eddy current sensor 7, and a controller;

[0071] The optical mirror 1 is fixedly mounted on the mirror holder 2, and the four voice coil motors 3 are respectively located between the four corners of the mirror holder 2 and the quick-reflecting mirror base 6. The magnetic cylinder of each voice coil motor 3 is fixedly connected to one corner of the mirror holder 2, and the coil of each voice coil motor is fixedly connected to one corner of the quick-reflecting mirror base 6.

[0072] The four voice coil motors 3 are divided diagonally to form two control pairs FA and FB. The negative terminals of the two voice coil motors 3 in each control pair are connected. Current flows in from the positive terminal on one side and flows out from the positive terminal on the other side, forming a push-pull couple to provide driving force for the deflection of the mirror holder.

[0073] One end of the flexible shaft system 4 is rotatably connected to the four sides of the mirror holder 2, providing the mirror holder 2 with rotational freedom in the X and Y axis directions, and the other end is fixedly connected to the middle of the quick-reflecting mirror base 6 through the shaft system adapter 5.

[0074] The four eddy current sensors 7 are distributed at the midpoints of the four sides of the fast-reflecting mirror base 6, and are marked as X+, X-, Y+ and Y- respectively. They are used to sense the deflection of the mirror support in the X-axis and Y-axis directions and transmit the data to the controller.

[0075] Furthermore, the distance between adjacent voice coil motors 3 is 100mm, and the air gap between the magnet and the coil of the voice coil motor 3 is maintained at 1.0mm ± 0.05mm.

[0076] Furthermore, the controller uses a Xilinx Kintex-7 FPGA as its control core.

[0077] Furthermore, the eddy current sensor 7 is model CS-1000, and the four eddy current sensors 7 are respectively aligned with the edge measuring surface of the mirror holder, with an initial gap of 1.0mm.

[0078] This invention effectively solves the problems of shortened lever arm, large delay, and severe coupling in traditional layouts by using diagonal grouping of motors and vector control strategy. Each axis control is driven by four voice coil motors simultaneously, which effectively improves the single-axis closed-loop bandwidth and makes full use of the motor torque. It significantly improves the dynamic response performance and multi-axis coordination capability of fast reflectors, and is particularly suitable for high-bandwidth, high-precision optical control systems.

Claims

1. A high-bandwidth driving method for fast-reflecting mirrors based on diagonal motor vector control, characterized in that, include: System layout and wiring: The voice coil motors distributed at the four corners of the fast reflector base are divided into two control pairs, FA and FB, according to the diagonal. The negative terminals of the two voice coil motors in each control pair are connected, and the current flows in from the positive terminal on one side and flows out from the positive terminal on the other side, forming a push-pull couple. Four eddy current sensors are distributed at the midpoints of the four sides of the fast-reflecting mirror base, and are marked as X+, X-, Y+ and Y- respectively. They are used to sense the deflection of the mirror support in the X-axis and Y-axis directions and transmit the data to the controller. Closed-loop control process: The controller starts a real-time closed-loop cycle, and executes the following steps in sequence within each cycle: a. Command Reception: The controller receives the target angle command sent by the host computer through the RS422 interface. The command format is (θ, φ), where θ is the target deflection angle on the X-axis and φ is the target deflection angle on the Y-axis. The command update frequency is fixed at 5kHz. b. Feedback Acquisition: The four eddy current sensors output acquisition signals, which are differentially amplified and received by the controller. After that, they are digitally filtered to obtain the actual deflection angles (α, β) of the mirror support on the X and Y axes. c. Torque command generation: Compare the target angle (θ,φ) with the actual angle (α,β) to calculate the X-axis angle deviation ΔX=θ-α and the Y-axis angle deviation ΔY=φ-β; ΔX and ΔY are input into the preset position loop PID in the controller, and through proportional P, integral I, and derivative D operations, they are converted into "X-axis target torque Tx" and "Y-axis target torque Ty" required to achieve angle correction. d. Output command synthesis and PWM control: Output synthesis: The component force commands of the same control pair are superimposed to obtain the total output force command of the FA control pair FA=Tx+Ty, and the total output force command of the FB control pair FB=Tx-Ty; PWM Conversion: Converts the control pairs FA and FB into PWM signals with adjustable duty cycles. The signal frequency is fixed at 100kHz. The duty cycle is positively correlated with the output command size. The greater the output demand, the higher the PWM duty cycle. Signal amplification and driving: After the PWM signal is amplified by the motor drive circuit, it is input into the motor circuits controlling FA and FB respectively, driving the motor to generate a push-pull couple, which drives the mirror drag and optical mirror to deflect. e. Real-time closed-loop iteration: During the deflection process, the eddy current sensor continuously collects the mirror holder attitude signal and feeds it back to the controller to enter the next cycle. Steps bd are repeated until the deviation between the actual angle of the mirror holder and the target angle is less than the allowable threshold, so as to achieve dynamic stable control.

2. The fast-reflecting mirror high-bandwidth driving method based on diagonal motor vector control according to claim 1, characterized in that, Before implementing the closed-loop control process, the following steps are required: Setting the positive direction of control: Establish a Cartesian coordinate system based on the positions of the four eddy current sensors. The positive direction of control for FA is defined by the positive output of the voice coil motor in the first quadrant and the reverse output of the voice coil motor in the third quadrant. The positive direction of control for FB is defined by the reverse output of the voice coil motor in the second quadrant and the positive output of the voice coil motor in the fourth quadrant.

3. The fast-reflecting mirror high-bandwidth drive method based on diagonal motor vector control according to claim 2, utilizing a fast-reflecting mirror high-bandwidth drive system based on diagonal motor vector control, is characterized in that... The fast-reflecting mirror high-bandwidth drive system based on diagonal motor vector control includes an optical mirror, a mirror holder, a voice coil motor, a flexible shaft system, a shaft system adapter, a fast-reflecting mirror base, an eddy current sensor, and a controller. The optical mirror is fixedly mounted on the mirror holder, and the four voice coil motors are respectively located between the four corners of the mirror holder and the quick-reflecting mirror base. The magnetic cylinder of each voice coil motor is fixedly connected to one corner of the mirror holder, and the coil of each voice coil motor is fixedly connected to one corner of the quick-reflecting mirror base. The four voice coil motors are divided diagonally to form two control pairs FA and FB. The negative terminals of the two voice coil motors in each control pair are connected, and the current flows in from the positive terminal on one side and flows out from the positive terminal on the other side, forming a push-pull couple to provide driving force for the deflection of the mirror holder. One end of the flexible shaft system is rotatably connected to the four sides of the mirror holder, providing the mirror holder with rotational freedom in the X and Y axes, and the other end is fixedly connected to the middle of the quick-reflecting mirror base through the shaft system adapter. The four eddy current sensors are distributed at the midpoints of the four sides of the fast-reflecting mirror base, and are marked as X+, X-, Y+ and Y- respectively. They are used to sense the deflection of the mirror support in the X-axis and Y-axis directions and transmit the data to the controller.

4. The fast-reflecting mirror high-bandwidth driving method based on diagonal motor vector control according to claim 3, characterized in that, The distance between adjacent voice coil motors is 100mm.

5. The fast-reflecting mirror high-bandwidth driving method based on diagonal motor vector control according to claim 3, characterized in that, The controller uses a Xilinx Kintex-7 FPGA as its control core.

6. The fast-reflecting mirror high-bandwidth driving method based on diagonal motor vector control according to claim 3, characterized in that, The eddy current sensor is model CS-1000.

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