A dynamic goniometry system and method using a synchronization frequency

Abstract

This invention relates to the interdisciplinary field of optical precision measurement and automated control, specifically a dynamic angle measurement system using a synchronous frequency. The system comprises a measurement unit, a scanning control unit, a linkage unit, a frequency synchronization unit, a reference unit, a data processing unit, and a host computer. The reference unit provides an angle reference. The frequency synchronization unit provides a reference clock signal, drives the scanning control unit to generate control signals, and also drives the measurement unit to output external angle signals. The frequency synchronization unit reads and synthesizes the control signals and the external angle signals, and sends them to the linkage unit and the data processing unit. The data processing unit calculates error signals. The linkage unit adjusts the operating parameters of the measurement unit and the scanning control unit to improve scanning accuracy. This invention also includes a method. This invention achieves ultra-high frequency, high-precision synchronization, meeting the stringent requirements of high-precision equipment for measurement synchronization and accuracy. It also achieves deep real-time linkage between measurement and control, further improving measurement reliability and accuracy.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of optical precision measurement and automated control, and in particular to a dynamic angle measurement system and method using a synchronous frequency. Background Technology

[0002] In high-end applications of dynamic angle calibration in satellite inertial navigation and high-orbit Earth observation scanning control systems, extremely high angle measurement accuracy is required, typically reaching 0.1 arcseconds or even higher. However, existing technologies have many problems:

[0003] Frequency matching challenge: To ensure measurement stability, high-precision photoelectric autocollimators typically use a data acquisition frequency of 60Hz, while scanning control systems, to achieve high-precision motion control, use a data return frequency as high as 8kHz or even higher. This significant frequency difference results in a time error of at least 16ms in traditional software synchronization methods, causing motion control commands to fail to correspond to the actual measured angle in real time. The dynamic angle measurement error can reach more than 0.5 arcseconds, which cannot meet the requirements of high-precision scenarios.

[0004] Defects in the linkage mechanism: Existing angle measuring devices lack a coordinated linkage design between the photoelectric autocollimator and the scanning control system. During dynamic measurement, it is impossible to adjust the scanning control system based on the real-time measurement data of the photoelectric autocollimator, nor can the measurement parameters of the photoelectric autocollimator be optimized based on the motion state of the scanning control system. This results in low overall measurement efficiency and makes it difficult to achieve high-precision, high-speed dynamic measurements.

[0005] Insufficient market adaptability: Most angle measuring devices on the market are designed for general-purpose scenarios and lack adaptability to the specific needs of high-precision niche markets (accounting for less than 5%) such as semiconductor manufacturing and aerospace. For example, they cannot achieve dynamic measurement with a large field of view of more than 3000 arcseconds while ensuring high-precision measurement of 0.1 arcseconds, making it difficult to meet the comprehensive requirements of these fields for measurement devices with high precision, large field of view, and high dynamic response. Summary of the Invention

[0006] The purpose of this invention is to provide a dynamic angle measurement system and method using a synchronization frequency, which mainly solves the problems existing in the prior art. It overcomes the synchronization problem between the acquisition frequency of the measurement unit and the return frequency of the scanning control unit, and also constructs a linkage mechanism between the two to improve measurement accuracy and efficiency.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is to provide a dynamic angle measurement system using a synchronization frequency, characterized in that it includes a measurement unit, a scanning control unit, a linkage unit, a frequency synchronization unit, a reference unit, a data processing unit, and a host computer.

[0008] The host computer is connected to the measurement unit, the scanning control unit, and the linkage unit, and directly or indirectly configures their operating parameters; the measurement unit, the scanning control unit, and the frequency synchronization unit are all mounted on the reference unit, which provides the angle reference.

[0009] The frequency synchronization unit provides a synchronized reference clock signal to the measurement unit, the scanning control unit, and the linkage unit. Driven by the reference clock signal, the scanning control unit generates a control signal to control the mechanical scanning unit to perform rotational scanning at a predetermined angular velocity. Driven by the reference clock signal, the measurement unit measures the angle of the mechanical scanning unit and outputs an external angle signal. The frequency synchronization unit reads the control signal and the external angle signal, synchronizes them, generates a composite signal, and sends it to the linkage unit and the data processing unit. The data processing unit calculates an error signal based on the composite signal and feeds it back to the linkage unit. The linkage unit adjusts the operating parameters of the measurement unit and the scanning control unit based on the composite signal and the error signal, thereby improving the scanning accuracy of the mechanical scanning unit.

[0010] Furthermore, the measurement unit includes a photoelectric autocollimator and a data acquisition module;

[0011] The photoelectric autocollimator and the data acquisition module read the operating parameters set by the host computer; the photoelectric autocollimator configures optical components according to the operating parameters, and then uses the optical components to measure the real-time angle of the mechanical scanning unit; the data acquisition module converts the real-time angle into an external angle signal in digital form at the sampling frequency configured by the operating parameters, and sends it to the frequency synchronization unit.

[0012] Furthermore, the scanning control unit includes a motion control module, an angle measurement module, and a control interface module;

[0013] The motion control module generates the control signal based on the operating parameters and sends it to the mechanical scanning unit and the frequency synchronization unit. The mechanical scanning unit drives the mechanical scanning based on the control signal. The angle measurement module uses a sensor to generate the internal angle signal of the mechanical scanning unit and transmits it to the motion control module to complete closed-loop control during the mechanical scanning process. The host computer and the linkage unit configure the operating parameters through the control interface module. Specifically, the host computer sends the field of view accuracy to the control interface module, which converts it into specific operating parameters. The linkage unit directly sends the operating parameters to the control interface module.

[0014] Furthermore, the linkage unit includes a host computer interface module, a linkage control module, and a data interaction module;

[0015] The host computer interface module is connected to the host computer and receives the working parameters sent by the host computer; the linkage control module is connected to the measurement unit, the scanning control unit and the frequency synchronization unit through the data interaction module; the linkage control module reads the synthesized signal from the frequency synchronization unit, and then generates new working parameters according to the linkage strategy in the working parameters, and sends them to the measurement unit or the scanning control unit, thereby dynamically adjusting the working state of the measurement unit and the scanning control unit.

[0016] Furthermore, the frequency synchronization unit includes a high-speed interface module, a programmable logic module, and a crystal oscillator module;

[0017] The high-speed interface module is connected to the measurement unit, the scanning control unit, and the linkage unit via a low-latency trigger cable; the low-latency trigger cable is fixed to the high-speed interface module via a coaxial bayonet connector.

[0018] The crystal oscillator module generates a high-speed clock signal, which serves as a reference clock signal and is provided to the measurement unit and the scanning control unit through the high-speed interface module. The programmable logic module uses the high-speed interface module to read the control signal and the external angle signal, performs interpolation compensation on the signal with the lower sampling rate, and then synchronously merges the control signal and the external angle signal into the composite signal, which is then sent to the linkage unit through the high-speed interface module.

[0019] Furthermore, the reference unit includes a multi-tooth indexing stage and a vacuum adsorption platform; the measuring unit is mounted on the multi-tooth indexing stage, which provides the angular reference; the scanning control unit, the frequency synchronization unit, and the data processing unit are adsorbed and mounted on the vacuum adsorption platform.

[0020] This invention also discloses an angle measurement method using the above-mentioned dynamic angle measurement system with synchronous frequency, characterized by comprising the following steps:

[0021] Step S100: Using the host computer, send the working parameters to the measurement unit, the scanning control unit, and the linkage unit;

[0022] In step S200, the frequency synchronization unit provides a reference clock signal to the measurement unit and the scanning control unit;

[0023] In step S300, the measuring unit, driven by the reference clock signal, measures the mechanical scanning unit, generates the external angle signal, and sends it to the frequency synchronization unit; the sampling rate of the external angle signal is lower than that of the reference clock signal, and is obtained by down-frequency buffering of the reference clock signal.

[0024] In step S400, the scanning control unit generates the control signal under the drive of the reference clock signal and sends it to the frequency synchronization unit; the sampling rate of the control signal is lower than that of the reference clock signal.

[0025] In step S500, the frequency synchronization unit performs interpolation upsampling and fitting compensation on the signal with the low sampling rate in the external angle signal and the control signal, and finally merges the upsampling external angle signal and the control signal to form the composite signal, which is then sent to the linkage unit and the data unit.

[0026] In step S600, the data processing unit reads the synthesized signal, calculates error statistics, generates an error signal, and feeds it back to the linkage unit;

[0027] In step S700, the linkage unit reads and parses the synthesized signal, and adjusts the operating parameters of the measurement unit and the scanning control unit in conjunction with the error signal; if scanning needs to continue, it jumps to step S300.

[0028] Further, in step S200, the generation of the reference clock signal includes the following steps:

[0029] Step S201: The frequency synchronization unit uses the included crystal oscillator module to generate a high-speed reference clock signal;

[0030] Step S202: The frequency synchronization unit generates the reference clock signal based on the high-speed reference clock signal and sends the reference clock signal to the measurement unit and the scanning control unit;

[0031] In step S203, the frequency synchronization unit reads the count values ​​of the timers in the measurement unit and the scanning control unit at preset intervals; the timers are driven by the reference clock signal.

[0032] In step S204, the frequency synchronization unit, based on the proportional-integral-derivative control algorithm, compares the count value and adjusts the phase of the reference clock signal.

[0033] Further, the control signal is generated in step S400, which includes the following steps:

[0034] Step S401: The scanning control unit uses a phase-locked loop to divide the reference clock signal to form a control generation signal; the control generation signal drives the generation of the control signal.

[0035] In step S402, the scanning control unit monitors the control generation signal using the reference clock signal; when the jitter of the control generation signal exceeds the sampling threshold, the scanning control unit regenerates the control generation signal based on the reference clock signal.

[0036] Further, in step S500, generating the synthesized signal includes the following steps:

[0037] Step S501: The frequency synchronization unit selects the signal with a lower sampling rate from the external angle signal and the control signal as the signal to be processed, and the signal with a higher sampling rate as the target signal.

[0038] In step S502, the frequency synchronization unit uses a bilinear interpolation algorithm to up-interpolate the signal to be processed so that its frequency matches the frequency of the target signal.

[0039] Step S503: The frequency synchronization unit uses a third-order Bezier curve to fit and compensate the signal to be processed after frequency up-interpolation.

[0040] Step S504: For the fitted and compensated signal to be processed, timestamps are marked using the reference clock signal as the standard to form the processed signal;

[0041] Step S505: Align the timestamps of the processed signal and the target signal, and merge the processed signal and the target signal into the synthesized signal.

[0042] In view of the above technical features, the dynamic angle measurement system and method using synchronous frequency of the present invention have the following significant advantages:

[0043] 1. This invention achieves ultra-high frequency, high-precision synchronization. By using a 40MHz synchronization clock input and an interpolation algorithm to align the data acquired by the measurement unit with the data returned by the scanning control unit, the time synchronization error between the two is reduced from 16ms in the traditional scheme to within 12.5 microseconds, an improvement of 1280 times. This significant improvement in time synchronization accuracy effectively solves the problem of large dynamic angle measurement errors caused by frequency mismatch, optimizing the root mean square error (RMSE) of dynamic angle measurement to 0.15 arcseconds (3σ), meeting the stringent requirements of high-precision equipment for measurement synchronization and accuracy.

[0044] 2. In this invention, the measurement unit and the scanning control unit achieve real-time depth linkage using a linkage unit. Combined with a 40MHz synchronization clock, the states of the measurement unit and the scanning control unit are synchronized with high precision, enabling real-time depth interaction and collaborative operation between them. When a deviation occurs in the measurement angle, the system can quickly respond and adjust the scanning motion parameters based on precisely synchronized data, reducing the error compensation time to sub-millisecond levels. Simultaneously, by optimizing the measurement parameters according to the scanning motion state, the overall measurement efficiency is improved by 5 to 8 times, maintaining extremely high measurement accuracy and dynamic response performance even at an ultra-low uniform scanning speed of 0.00005 degrees / second.

[0045] 3. In this invention, targeting the niche high-precision market (accounting for less than 5%) such as aerospace, this invention achieves a 3000 arcsecond wide field of view measurement with a high precision of 0.1 arcsecond through a dynamic matching algorithm of field of view and precision (F=A*α), breaking through the bottleneck of traditional devices that make it difficult to achieve both high precision and wide field of view. In addition, the high-precision synchronization characteristics brought by the 40MHz synchronous clock further improve the measurement reliability and accuracy of the system in these high-precision scenarios, filling a market gap.

[0046] 4. This invention also possesses strong system scalability, adaptable to photoelectric autocollimators with different accuracy levels above 0.1 arcsecond. By adjusting the synchronization parameters and linkage control algorithm, it can achieve any combination of 10-100Hz acquisition frequency and control frequency above 200Hz. The flexible configurability of the 40MHz synchronization clock also provides possibilities for future higher frequency data synchronization needs and integration with other high-precision equipment, meeting the diverse needs of future high-precision measurement technology development. Attached Figure Description

[0047] Figure 1 This is a system block diagram of a preferred embodiment of the dynamic angle measurement system using a synchronous frequency according to the present invention;

[0048] Figure 2 This is a flowchart of a preferred embodiment of the angle measurement method of the present invention using a dynamic angle measurement system with a synchronous frequency.

[0049] In the diagram: 100 - Measurement unit, 200 - Scan control unit, 300 - Linkage unit, 400 - Frequency synchronization unit, 500 - Reference unit, 600 - Data processing unit, 700 - Host computer, 800 - Mechanical scanning unit;

[0050] 101-Photoelectric autocollimator; 102-Data acquisition module;

[0051] 201-Motion control module, 202-Angle measurement module, 203-Control interface module;

[0052] 301 - Host computer interface module; 302 - Linkage control module; 303 - Data interaction module;

[0053] 401 - High-speed interface module; 402 - Programmable logic module; 403 - Crystal oscillator module;

[0054] 501 - Multi-tooth indexing stage; 502 - Vacuum adsorption platform. Detailed Implementation

[0055] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0056] Please see Figure 1 This invention discloses a dynamic angle measurement system and method using a synchronization frequency. As shown in the figure, a preferred embodiment of the system comprises a measurement unit 100, a scanning control unit 200, a linkage unit 300, a frequency synchronization unit 400, a reference unit 500, a data processing unit 600, and a host computer 700.

[0057] The host computer 700 can be a server or a PC. It provides the human-machine interface for the dynamic angle measurement system, configures operating parameters before the system starts working, and records the working process. The host computer 700 is electrically connected to the measurement unit 100, the scanning control unit 200, the linkage unit 300, and the data processing unit 600. It directly configures the measurement operating parameters for the measurement unit 100, indirectly configures the scanning operating parameters for the scanning control unit 200, and directly configures the linkage parameters for the linkage unit 300, such as the linkage strategy and the linkage start threshold. It further processes the data from the data processing unit 600.

[0058] The host computer 700 itself does not require an angle reference and is not sensitive to angle deviations. It can be installed independently and connected to other working units via cables. The measurement unit 100, scan control unit 200, frequency synchronization unit 400, and data processing unit 600 are all mounted on the reference unit 500, which provides the angle reference. This ensures that the measurement unit 200 and scan control unit 300 start working based on a reliable angle reference. At the same time, the frequency synchronization unit 400 can be placed as close as possible to the measurement unit 200 and scan control unit 300 to reduce cable transmission delay.

[0059] The reference unit 500 includes a multi-tooth indexing stage 501 and a vacuum adsorption platform 502. The multi-tooth indexing stage 501 has extremely high angular positioning accuracy, with an absolute accuracy of 0.3 arcseconds over 360 degrees and 0.1 arcseconds within 40 degrees, and a flatness of 0.005 mm, providing a high-precision angular reference for the entire measurement system. The flatness of the vacuum adsorption platform 502 is controlled between -0.002 mm and +0.002 mm. It has a vacuum adsorption function, which can effectively fix the measured object, reduce external vibration interference, and is suitable for high-precision measurement environments such as cleanrooms. Specifically, the measurement unit 100 is mounted on the multi-tooth indexing stage 501, while the scanning control unit 200, frequency synchronization unit 400, and mechanical scanning unit 800 are mounted on the vacuum adsorption platform 502 using vacuum adsorption. Vacuum adsorption ensures that the scanning control unit 200 and frequency synchronization unit 400 are fixed in position during operation and also facilitates disassembly and position adjustment. During the calibration phase of the dynamic angle measurement system, the measuring unit 100 is aligned with the mechanical scanning unit 800 by adjusting the multi-tooth indexing stage 501, thus locking the initial angle.

[0060] The measurement unit 100 consists of an optoelectronic autocollimator 101 and a data acquisition module 102. The optoelectronic autocollimator 101 includes optical components and uses optical principles to measure the angular deviation of the object being measured. Its absolute angular measurement accuracy is ≤0.1 arcseconds, repeatability is ≤0.04 arcseconds, and resolution reaches 0.001 arcseconds. The optoelectronic autocollimator 101 integrates an adaptive aperture assembly and an optical path fine-tuning mechanism. The aperture diameter can be precisely adjusted within the range of 0.5-5mm, while the adjustment accuracy of the optical path fine-tuning mechanism is 0.01 arcseconds, enabling dynamic adjustment of the field of view from 50 arcseconds × 50 arcseconds to 3000 arcseconds × 3000 arcseconds. The data acquisition module 102 performs photoelectric signal conversion, converting the angular deviation into a digital signal. It connects to the optoelectronic autocollimator 101, acquires angle measurement data in real time, outputs data at a frequency of 60Hz, and transmits the acquired data to the frequency synchronization unit 400. The optical path in the photoelectric autocollimator 101 is configurable, and the specific configuration method is taken from the measurement working parameters provided by the host computer 700. The data acquisition module 102 also reads the sampling rate configuration from the measurement working parameters, and generates an external angle signal in digital form at a specified sampling frequency under the drive of an external reference clock signal. The external reference clock signal comes from the frequency synchronization unit 400.

[0061] The scanning control unit 200 consists of a motion control module 201, an angle measurement module 202, and a control interface module 203. The control interface module 203 serves as the interface connecting the scanning control unit 200 to the linkage unit 300, the frequency synchronization unit 400, and the host computer 700. According to its linkage strategy, the linkage unit 300 directly sends new scanning operating parameters to the scanning control unit 200 through the control interface module 203, thereby changing the operating mode of the motion control module 201 and adjusting its scanning behavior. The host computer 700 configures the motion control module 201 indirectly. Specifically, the host computer 700 does not directly send scanning operating parameters; instead, it sends the field of view precision to the control interface module 203. The mapping algorithm built into the control interface module 203 converts this precision into specific scanning operating parameters before configuring the motion control module 201. The mapping algorithm automatically configures scanning control parameters, including scanning speed (>=0.00005 degrees / second) and field of view, based on different precision requirements. The field of view is set based on the capabilities of the measurement unit 100, i.e., the field of view and accuracy of the photoelectric autocollimator 101, and the conversion formula is as follows:

[0062] F = A * α

[0063] Where α is the target accuracy and A is the field of view, both measured in arcseconds.

[0064] The scanning control unit 200 also receives a reference clock signal from the frequency synchronization unit 400 through the control interface module 203, and generates control signals at the same time.

[0065] The motion control module 201 possesses high-precision motion control capabilities, with a scanning control accuracy ≤0.1 arcseconds and a data sampling frequency of 8kHz. It can precisely control scanning motion and supports ultra-low-speed stable scanning with acceleration of 0.003 degrees / second and a constant speed of 0.00005 degrees / second. Driven by an external clock, the motion control module 201 outputs motor control signals to each specific motor in the connected mechanical scanning unit 800 at a specified sampling frequency (e.g., 8kHz) according to the scanning operating parameters, and simultaneously sends the control signals to the frequency synchronization unit 400. The external reference clock signal comes from the frequency synchronization unit 400. The motors in the mechanical scanning unit 800 actuate, driving the system to perform rotary mechanical scanning at a predetermined angular velocity.

[0066] The angle measurement module 202 consists of multiple sensors. These sensors, arranged near the mechanical scanning unit 800, obtain the angle signal of the mechanical scanning unit 800 as an internal angle signal after calibration using external data (e.g., measurement unit 100). The internal angle signal is transmitted to the motion control module 201, thereby forming a fast closed-loop control during the mechanical scanning process. However, the measurement accuracy of the angle measurement module 202 is lower than that of the external data provided by the measurement unit 100. Therefore, in high-precision angle mechanical scanning scenarios, it is still necessary to link with the measurement unit 100 to ensure scanning accuracy. The sampling frequency of the internal angle signal is 64kHz.

[0067] The linkage unit 300 includes a host computer interface module 301, a linkage control module 302, and a data interaction module 303. The host computer interface module 301 connects the linkage control module 302 to the host computer 700. The data interaction module 303 connects the linkage control module 302 to the measurement unit 100, the scanning control unit 200, and the frequency synchronization unit 400, enabling bidirectional data transmission between them and ensuring that each unit can share measurement data, control commands, and status information in real time.

[0068] The linkage control module 302 receives linkage parameters from the host computer 700, synthesized signals from the frequency synchronization unit 400, and error feedback from the data processing unit 600. The synthesized signal includes an external angle signal from the measurement unit 100 synchronized by the frequency synchronization unit 400 and a control signal from the scanning control unit 200. Based on the linkage strategy and linkage threshold in the linkage parameters, when the synthesized signal triggers the linkage threshold, the linkage control module 302 generates new operating parameters according to the linkage strategy and sends them to the measurement unit 100 and the scanning control unit 200. This adjusts the operating mode of the measurement unit 100 and the scanning control unit 200, for example, by making the mechanical scanning lead or lag, or by adjusting the external measurement parameters, thereby making the scanning process more accurate and smooth. For example, when the photoelectric autocollimator 101 in the measurement unit 100 detects an angular deviation exceeding a set threshold (e.g., 0.15 arcseconds), the linkage control module 302 generates a compensation command and sends it to the motion control module 201 in the scanning control unit 200 to adjust the scanning motion parameters and achieve error compensation. At the same time, based on the motion state of the scanning control unit 200, the linkage control algorithm unit can also optimize the measurement parameters of the photoelectric autocollimator 101, such as adjusting the sampling frequency and field of view.

[0069] The frequency synchronization unit 400 includes a high-speed interface module 401, a programmable logic module 402, and a crystal oscillator module 403. The frequency synchronization unit 400 has two functions: providing an external reference clock signal and aligning the sampling frequency difference between the measurement unit 100 and the scan control unit 200, ensuring that each external angle signal and control signal are aligned individually to generate a composite signal that is sent to the linkage unit 300. The linkage unit 300 then provides external corrections to the scan control unit 200 according to its linkage strategy.

[0070] The high-speed interface module 401 includes multiple cable interfaces. These cable interfaces are used to connect low-latency trigger cables, thereby connecting the programmable logic module 402 and crystal oscillator module 403 to the measurement unit 100, scan control unit 200, linkage unit 300, and data processing unit 600. The low-latency trigger cables are secured to the cable interfaces on the high-speed interface module 401 via coaxial bayonet connectors.

[0071] The crystal oscillator module 403 provides a reference clock signal. It generates a high-speed reference clock signal using physical characteristics; in this embodiment, it is 40MHz, with a signal period of 25ns. This, combined with the programmable logic module 402, achieves sub-nanosecond synchronization accuracy calibration, theoretically compressing the time synchronization error to ≤12.5μs. This high-speed reference clock signal is input to the measurement unit 100 and the scan control unit 200 via a low-latency trigger cable on the high-speed interface module 401, providing them with a synchronized reference clock signal and a unified time reference, ensuring the time consistency between data acquisition and control commands. The measurement unit 100 and the scan control unit 200 operate under the same clock source, with identical frequency and phase of the reference clock signal. Simultaneously, the high-speed reference clock signal also serves as the reference clock signal for the programmable logic module 402 itself.

[0072] The programmable logic module 402 employs an FPGA chip and incorporates a dual-rate data processing architecture to align external angle signals and control signals. In this embodiment, the measurement unit 100 outputs external angle signals at a frequency of 60Hz, while the scanning control unit 200 generates control signals at a rate of 8KHz. Therefore, after reading the control signals and external angle signals using the high-speed interface module 401, the programmable logic module 402 performs interpolation compensation on the external angle signals. The interpolated external angle signals are up-frequencyd to 8KHz, allowing them to correspond one-to-one with the control signals and be synchronously merged into a composite signal, which is then sent to the linkage unit 300 and the data processing unit 600 via the high-speed interface module.

[0073] After reading the synthesized signal from the frequency synchronization unit 400, the data processing unit 600 extracts the synchronized 8kHz angle data and the 8kHz position data of the scanning control system, and performs time error calculations on them. In this embodiment, the time difference of 99% of the sampling points is required to be ≤37.5 microseconds (corresponding to 0.3 sampling points in an 8kHz cycle, based on the high precision characteristics of a 40MHz synchronization clock); simultaneously, the root mean square error (RMSE) is calculated using the dynamic angle measurement error formula Δθ=|θsync,i-Pi|, requiring RMSE ≤0.15 arcseconds (3σ). If the accuracy does not meet the requirements, the data processing unit 600 feeds back the error information to the linkage unit 300. The linkage unit 300 adjusts the linkage control algorithm parameters according to the error situation, optimizes the working state of the measurement unit 100 and the scanning control unit 200, and re-measures until the accuracy requirements are met. In different scenarios, the synthesized signal is also used for specific calculations, such as in the semiconductor manufacturing scenario, where harmonic error data within a ±1000 arcsecond field of view is extracted as an error reference.

[0074] Please see Figure 2 The present invention also discloses an angle measurement method utilizing the above-described dynamic angle measurement system using a synchronization frequency. A preferred embodiment includes the following steps:

[0075] Step S1: Configure operating parameters.

[0076] The operating parameters of the measurement unit, scanning control unit, and linkage unit are configured using a host computer. For the measurement unit, factory parameters include the input test range and required accuracy. For the linkage unit, these are the linkage strategy and linkage threshold. For the scanning control unit, the configuration information sent by the host computer is processed again to form the final scanning operating parameters. Specifically, the host computer sets the field of view accuracy A based on the target accuracy α and the autocollimator accuracy, and calculates the theoretical field of view F using the formula F = A * α. For example, when A = 3000 arcseconds and α = 0.1 arcseconds, F = 300 arcseconds. Simultaneously, other parameters such as the scanning speed V (e.g., 0.0001 degrees / second) are determined based on actual measurement requirements.

[0077] Step S2: Send a synchronization reference signal.

[0078] The frequency synchronization unit generates a unified synchronization reference signal, which is sent to the measurement unit and the scanning control unit in two paths. The reference clock signal is in phase and has the same frequency.

[0079] Step S21: Generate a high-speed reference clock signal.

[0080] The frequency synchronization unit includes a crystal oscillator module. Utilizing its physical characteristics, the crystal oscillator module, driven by an oscillation circuit, acts as a source to generate a high-speed reference clock signal.

[0081] Step S22: Generate a reference clock signal.

[0082] The high-speed reference clock signal generated by the crystal oscillator is modified to become a reference clock signal. The reference clock signal is transmitted to the measurement unit and the scan control unit respectively through the low-latency trigger cable on the high-speed interface module, serving as the reference clock signal to drive their internal logic operations.

[0083] Step S23: Read back the count value.

[0084] Each of the measurement unit and the scanning control unit has a timer. These timers are driven by the same reference clock signal, and theoretically their counts should be identical. However, due to phase jitter during actual operation, the counts may deviate slightly. The frequency synchronization unit reads the counts of these two timers at preset intervals (every 5ms, or every 200,000 cycles at a 40MHz clock) via a low-latency trigger cable on the high-speed interface module.

[0085] Step S24, clock phase adjustment.

[0086] After the frequency synchronization unit reads back the count values ​​of the two timers, it adjusts the phase of the reference clock signal sent to the measurement unit and the scanning control unit based on the difference between the two, according to the proportional-integral-derivative control algorithm, so as to reduce the difference between them.

[0087] Step S3: Acquire external angle signals.

[0088] The measurement unit uses a reference clock signal from the frequency synchronization unit as its clock input and periodically scans the rotating mechanical module in the mechanical scanning unit to measure its angle and generate an external angle signal. The external angle signal is sent to the frequency synchronization unit via a low-latency trigger cable. Because each optical measurement requires a certain amount of time to stabilize, there is an upper limit to the sampling rate of the optical measurement results. In this embodiment, the sampling rate is 60Hz, meaning one external angle signal is generated per second. The sampling action of the measurement unit is driven by a down-frequency version of the reference clock signal, and its sampling time is related to the phase of the reference clock signal. Simultaneously with the sampling of the external angle signal, a timestamp is applied to it using the reference clock signal. That is, the timestamp is applied using a 40MHz reference clock signal, while the actual data sampling uses a down-frequency clock (60Hz) after eliminating clock jitter through a phase alignment algorithm.

[0089] Step S4: Generate control signals and monitor the sampling reference clock signal.

[0090] The scanning control unit is also driven by a reference clock signal. It generates control signals, which directly control the various motors in the mechanical scanning unit and are also sent to the frequency synchronization unit via low-latency trigger cables. The more frequently the control signals are sent, the more precise the control of the mechanical scanning unit; however, the motor's response speed must also be considered, therefore the generation frequency is lower than that of the reference clock signal. In this embodiment, the control signal generation rate is 8K, meaning eight thousand control signals are generated per second. The scanning control unit's action of generating control signals is driven by a down-frequency version of the reference clock signal, and the timing of its command generation is related to the phase of the reference clock signal.

[0091] Step S41: Generate control signals.

[0092] Because the frequency of the generated command is lower than that of the reference clock signal, but it needs to be aligned with the rising or falling edge of the reference clock signal, the scan control unit uses a phase-locked loop to divide the input reference clock signal to produce an 8kHz control generation signal. The phase of the control generation signal is aligned with the reference clock signal, only the frequency is lower. The scan control unit triggers the generation of the control signal at the rising or falling edge of the control generation signal, thus ensuring that the generation of the control signal originates from the reference clock signal and eliminating data transmission delay in the asynchronous clock domain. Simultaneously, the reference clock signal is used to timestamp the control signal.

[0093] Step S42: Monitor and adjust the generated control signal.

[0094] The frequency-divided sampling reference clock signal will still fluctuate due to various errors and interferences during actual operation. Therefore, the scan control unit uses the reference clock signal to monitor the control generation signal. When the jitter of the control generation signal exceeds the preset sampling threshold in the operating parameters, the scan control unit reinitializes the control generation signal, that is, it regenerates the control generation signal based on the reference clock signal, ensuring that the edge of the control generation signal is aligned with the edge of the reference clock signal. In this embodiment, the sampling threshold is: a deviation of >12.5 microseconds for three consecutive cycles.

[0095] Step S5: Generate the synthesized signal.

[0096] The sampling rate of the external angle signal and the generation rate of the control signal are different, so they cannot be directly aligned one-to-one. In this embodiment, the external angle signal is 60Hz, while the control signal is 8kHz. The frequency synchronization unit performs a 133.33-fold interpolation upsampling (8000 / 60) and fitting compensation on the lower-frequency signal, i.e., the external angle signal, in the 40MHz frequency domain, to make it also reach the 8kHz frequency. At the same time, taking advantage of the high time resolution of the 40MHz clock, a ±1 nanosecond timestamp is implemented at each interpolation point. Finally, the upsampling external angle signal and the control signal are matched one-to-one according to the timestamp, merged to form a composite signal, and sent to the linkage unit. In the frequency synchronization unit, a pipelined architecture is used to implement the interpolation calculation. Taking advantage of the 40MHz clock frequency, the interpolation calculation time is compressed to within 25ns, thereby meeting the real-time processing requirements of 8kHz data.

[0097] Step S51: Select a low-frequency signal.

[0098] The frequency synchronization unit uses the low-frequency external angle signal as the signal to be processed and the high-frequency control signal as the target signal. In subsequent processing, the frequency of the signal to be processed is increased to match the frequency of the target signal.

[0099] Step S52: Frequency upsampling and interpolation of the signal to be processed.

[0100] The frequency synchronization unit uses a bilinear interpolation algorithm to up-interpolate the external angle signal, matching its frequency to the control signal frequency, thus obtaining an up-frequency external angle signal of 8kHz. The bilinear interpolation algorithm is as follows:

[0101]

[0102] Where: θ 60Hz (t) represents the angle value collected at 60Hz;

[0103] This is the time difference between the sampling point and the nearest 60Hz sampling point;

[0104] T 60Hz = 1 / 60 of a second;

[0105] T 8KHz = 1 / 8000 of a second.

[0106] Step S53: Fitting and compensating the signal to be processed.

[0107] The frequency synchronization unit uses a third-order Bézier curve to fit and compensate the external angle signal during frequency upsampling, making it smoother. The formula for the third-order Bézier curve compensation algorithm is as follows:

[0108] ync(t) = bilinear interpolation result + k·Δt^2·(θ) 60Hz(t+2T 60Hz )-2θ 60Hz (t+T 60Hz )+θ 60Hz (t))

[0109] Where: the coefficient k is dynamically calculated:

[0110] and Adaptively adjusted based on the 40MHz clock sampling interval.

[0111] Step S54: Mark the timestamp of the signal to be processed.

[0112] The frequency synchronization unit timestamps the fitted and compensated signal to be processed using a reference clock signal as a standard, forming the processed signal. The timestamp in the original external angle signal before interpolation remains unchanged. The timestamp of the new interpolation point is calculated and marked based on the interpolation position and the edge of the reference clock signal.

[0113] Step S55: Generate the synthesized signal.

[0114] The processed signal contains the same number of data points as the target signal, and all are timestamped. The original timestamps in the external angle signal and the timestamps in the control signal are both generated based on a 40MHz reference clock signal. Therefore, the difference in timestamps between each data point in the processed signal and each data point in the control signal is less than 1 nanosecond. The frequency synchronization unit aligns the data points with the closest timestamps as a single data point in the composite signal, thus generating the composite signal. Each second of the composite signal contains 8K data points, each containing two sets of data: angle data from the processed external angle signal and control data from the control signal.

[0115] Step S6: Calculate the error data.

[0116] The data processing unit reads the synthesized signal and, using the aligned up-frequency external angle signal and control signal, calculates the control error, i.e., the difference between the desired control angle and the actual angle, forming an error signal. The data processing unit then feeds back the error signal to the linkage unit.

[0117] Step S7, linkage adjustment.

[0118] The linkage unit reads the synthesized signal through a low-latency trigger cable, parses the real-time angle and control data, combines it with the error signal, and determines whether to intervene based on the operating parameters configured by the host computer. For example, when the deviation between the measured angle and the commanded angle is greater than 0.15 arcseconds, the linkage unit generates a feedforward compensation command and sends it to the scanning control unit to adjust the motor motion parameters and achieve real-time error compensation. Simultaneously, based on the motion state of the mechanical scanning unit, the linkage unit can also adjust the adaptive aperture and optical path fine-tuning mechanism of the measuring unit to optimize measurement parameters and ensure measurement accuracy. During the linkage process, the 40MHz synchronous clock ensures high-precision data synchronization, making the transmission of compensation commands more timely and accurate, further improving the dynamic response performance of the system. When the mechanical scanning unit performs large-angle scanning, the measurement operating parameters need to be adjusted multiple times.

[0119] If the scan is not finished, proceed to step S3 to continue signal acquisition and adjustment.

[0120] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A dynamic angle measurement system using a synchronization frequency, characterized in that, It includes a measurement unit, a scanning control unit, a linkage unit, a frequency synchronization unit, a reference unit, a data processing unit, and a host computer; The host computer is connected to the measurement unit, scanning control unit, and linkage unit, and directly or indirectly configures their operating parameters; the measurement unit, scanning control unit, and frequency synchronization unit are all mounted on the reference unit, which provides the angle reference. The frequency synchronization unit provides a synchronized reference clock signal to the measurement unit, the scanning control unit, and the linkage unit; driven by the reference clock signal, the scanning control unit generates a control signal to control the mechanical scanning unit to perform rotational scanning at a predetermined angular velocity; Driven by a reference clock signal, the measurement unit measures the angle of the mechanical scanning unit and outputs an external angle signal. The frequency synchronization unit reads the control signal and the external angle signal, synchronizes the control signal and the external angle signal, generates a composite signal, and sends it to the linkage unit and the data processing unit. The data processing unit calculates the error signal based on the composite signal and feeds it back to the linkage unit. Based on the composite signal and the error signal, the linkage unit adjusts the operating parameters of the measurement unit and the scanning control unit, thereby improving the scanning accuracy of the mechanical scanning unit. The measurement unit includes an opto-autocollimator and a data acquisition module; The scanning control unit includes a motion control module, an angle measurement module, and a control interface module; the motion control module generates the control signal according to the working parameters and sends it to the mechanical scanning unit and the frequency synchronization unit; the mechanical scanning unit drives the mechanical scanning based on the control signal. The angle measurement module uses a sensor to generate the internal angle signal of the mechanical scanning unit and transmits it to the motion control module to complete closed-loop control during the mechanical scanning process. The host computer and the linkage unit configure the working parameters through the control interface module. Specifically, the host computer sends the field of view accuracy to the control interface module, which converts it into specific working parameters. The linkage unit directly sends the working parameters to the control interface module. The linkage unit includes a host computer interface module, a linkage control module, and a data interaction module. The host computer interface module is connected to the host computer and receives the working parameters issued by the host computer. The linkage control module is connected to the measurement unit, the scanning control unit, and the frequency synchronization unit via the data interaction module. The linkage control module reads the synthesized signal from the frequency synchronization unit, and then generates new working parameters according to the linkage strategy in the working parameters, and sends them to the measurement unit or the scanning control unit, thereby dynamically adjusting the working state of the measurement unit and the scanning control unit. The reference unit includes a multi-tooth indexing stage and a vacuum adsorption platform; the measuring unit is installed on the multi-tooth indexing stage, which provides the angular reference; the scanning control unit, the frequency synchronization unit, and the data processing unit are adsorbed and installed on the vacuum adsorption platform.

2. The dynamic angle measurement system using a synchronous frequency according to claim 1, characterized in that, The photoelectric autocollimator configures optical components according to the operating parameters, and then uses the optical components to measure the real-time angle of the mechanical scanning unit; the data acquisition module converts the real-time angle into the external angle signal in digital form at the sampling frequency configured by the operating parameters, and sends it to the frequency synchronization unit.

3. The dynamic angle measurement system using a synchronous frequency according to claim 1, characterized in that, The frequency synchronization unit includes a high-speed interface module, a programmable logic module, and a crystal oscillator module; The high-speed interface module is connected to the measurement unit, the scanning control unit, and the linkage unit via a low-latency trigger cable; the low-latency trigger cable is fixed to the high-speed interface module via a coaxial bayonet connector. The crystal oscillator module generates a high-speed clock signal, which serves as a reference clock signal and is provided to the measurement unit and the scanning control unit through the high-speed interface module. The programmable logic module uses the high-speed interface module to read the control signal and the external angle signal, performs interpolation compensation on the signal with the lower sampling rate, and then synchronously merges the control signal and the external angle signal into the composite signal, which is then sent to the linkage unit through the high-speed interface module.

4. An angle measurement method using a dynamic angle measurement system with a synchronous frequency as described in claim 1, 2, or 3, characterized in that, Includes the following steps: Step S100: Using the host computer, send the working parameters to the measurement unit, the scanning control unit, and the linkage unit; In step S200, the frequency synchronization unit provides a reference clock signal to the measurement unit and the scanning control unit; In step S300, the measuring unit, driven by the reference clock signal, measures the mechanical scanning unit, generates the external angle signal, and sends it to the frequency synchronization unit; the sampling rate of the external angle signal is lower than that of the reference clock signal, and is obtained by down-frequency buffering of the reference clock signal. In step S400, the scanning control unit generates the control signal under the drive of the reference clock signal and sends it to the frequency synchronization unit; the sampling rate of the control signal is lower than that of the reference clock signal. In step S500, the frequency synchronization unit performs interpolation upsampling and fitting compensation on the signal with the low sampling rate in the external angle signal and the control signal, and finally merges the upsampling external angle signal and the control signal to form the composite signal, which is then sent to the linkage unit and the data processing unit. In step S600, the data processing unit reads the synthesized signal, calculates error statistics, generates an error signal, and feeds it back to the linkage unit; In step S700, the linkage unit reads and parses the synthesized signal, and adjusts the operating parameters of the measurement unit and the scanning control unit in conjunction with the error signal; if scanning needs to continue, it jumps to step S300.

5. The angle measurement method according to claim 4, characterized in that, In step S200, the generation of the reference clock signal includes the following steps: Step S201: The frequency synchronization unit uses the included crystal oscillator module to generate a high-speed reference clock signal; Step S202: The frequency synchronization unit generates the reference clock signal based on the high-speed reference clock signal and sends the reference clock signal to the measurement unit and the scanning control unit; Step S203: The frequency synchronization unit reads the count values ​​of the timers in the measurement unit and the scanning control unit at preset intervals; The timer is driven by the reference clock signal; In step S204, the frequency synchronization unit, based on the proportional-integral-derivative control algorithm, compares the count value and adjusts the phase of the reference clock signal.

6. The angle measurement method according to claim 4, characterized in that, The control signal is generated in step S400, which includes the following steps: Step S401: The scanning control unit uses a phase-locked loop to divide the reference clock signal to form a control generation signal; the control generation signal drives the generation of the control signal. In step S402, the scanning control unit monitors the control generation signal using the reference clock signal; when the jitter of the control generation signal exceeds the sampling threshold, the scanning control unit regenerates the control generation signal based on the reference clock signal.

7. The angle measurement method according to claim 4, characterized in that, In step S500, generating the synthesized signal includes the following steps: Step S501: The frequency synchronization unit selects the signal with a lower sampling rate from the external angle signal and the control signal as the signal to be processed, and the signal with a higher sampling rate as the target signal. In step S502, the frequency synchronization unit uses a bilinear interpolation algorithm to up-interpolate the signal to be processed so that its frequency matches the frequency of the target signal. Step S503: The frequency synchronization unit uses a third-order Bezier curve to fit and compensate the signal to be processed after up-frequency interpolation. Step S504: For the fitted and compensated signal to be processed, timestamps are marked using the reference clock signal as the standard to form the processed signal; Step S505: Align the timestamps of the processed signal and the target signal, and merge the processed signal and the target signal into the synthesized signal.

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