Dynamic angle measurement system and method using synchronous frequency

Abstract

The invention relates to the crossing field of optical precision measurement and automatic control, in particular to a dynamic angle measurement system using synchronous frequency, which comprises a measurement unit, a scanning control unit, a linkage unit, a frequency synchronization unit, a reference unit, a data processing unit and an upper computer. The reference unit provides an angle reference. The frequency synchronization unit provides a reference clock signal, drives the scanning control unit to generate a control signal, and further drives the measurement unit to output an external angle signal. The frequency synchronization unit reads and synthesizes the control signal and the external angle signal, and sends the control signal and the external angle signal to the linkage unit and the data processing unit. The data processing unit calculates an error signal. The linkage unit adjusts the working parameters of the measuring unit and the scanning control unit, and the scanning precision is improved. The invention also comprises a method. According to the invention, ultrahigh-frequency high-precision synchronization is realized, strict requirements of high-precision equipment on measurement synchronism and precision are met, depth real-time linkage of measurement and control is also realized, and the measurement reliability and accuracy are further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the cross field of optical precision measurement and automation control, and in particular to a dynamic angle measurement system and method using synchronous frequency. BACKGROUND

[0002] In the dynamic angle calibration high-end application in satellite inertial navigation and high-orbit earth observation scanning control system, the angle measurement precision requirement is very high, and usually needs to reach 0.1 arcsecond or even higher. However, the existing technology has many problems:

[0003] Frequency matching problem: In order to ensure the measurement stability, the high-precision photoelectric autocollimator generally sets the data acquisition frequency to 60Hz, and in order to realize high-precision motion control, the scanning control system returns data at a frequency of 8KHz or even higher. The huge frequency difference between the two causes at least 16ms of time error in the traditional software synchronization mode, so that the motion control command and the actual measurement angle cannot be corresponded in real time, and the dynamic angle measurement error can reach more than 0.5 arcsecond, which cannot meet the needs of high-precision scenes.

[0004] Linkage mechanism defect: The existing angle measurement device lacks the cooperative linkage design of the photoelectric autocollimator and the scanning control system. In the dynamic measurement process, the scanning control system cannot be feedback adjusted according to the real-time measurement data of the photoelectric autocollimator, and the measurement parameters of the photoelectric autocollimator cannot be optimized according to the motion state of the scanning control system, resulting in low overall measurement efficiency and difficulty in realizing high-precision and high-speed dynamic measurement.

[0005] Insufficient market adaptation: Most of the angle measurement devices on the market are designed for general scenarios, and lack adaptation ability for special needs of high-precision niche markets such as semiconductor manufacturing and aerospace, which account for less than 5%. For example, it is difficult to realize dynamic measurement of a large field of view of more than 3000 arcseconds while ensuring high-precision measurement of 0.1 arcsecond, and it is difficult to meet the comprehensive requirements of high-precision, large field of view and high dynamic response of measurement devices in these fields. SUMMARY

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

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is to provide a dynamic angle measurement system using synchronous frequency, characterized in that it comprises a measurement unit, a scanning control unit, a linkage unit, a frequency synchronization unit, a reference unit, a data processing unit and an upper 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 working parameters; the measurement unit, the scanning control unit and the frequency synchronization unit are all installed on the reference unit, and the angle reference is provided by the reference unit;

[0009] The frequency synchronization unit provides a synchronous reference clock signal to the measurement unit, the scanning control unit and the linkage unit; the scanning control unit generates a control signal under the drive of the reference clock signal, for controlling the mechanical scanning unit to rotate and scan at a predetermined angular velocity; the measurement unit measures the angle of the mechanical scanning unit under the drive of the reference clock signal, 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 an error signal based on the composite signal and feeds it back to the linkage unit; the linkage unit adjusts the working 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] Further, the measurement unit comprises an optoelectronic autocollimator and a data acquisition module;

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

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

[0013] 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 mechanical scanning based on the control signal; the angle measurement module generates an internal angle signal of the mechanical scanning unit using a sensor, and transmits it to the motion control module to complete closed-loop control during mechanical scanning; the host computer and the linkage unit configure the working parameters through the control interface module; wherein 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.

[0014] Further, the linkage unit comprises 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 issued by the host computer; the linkage control module is connected to the measurement unit, the scanning control unit and the frequency synchronization unit by using 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 the new working parameters to the measurement unit or the scanning control unit, so as to dynamically adjust the working state of the measurement unit and the scanning control unit.

[0016] Further, the frequency synchronization unit comprises a high-speed interface module, a programmable logic module and a crystal oscillator module.

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

[0018] The crystal oscillator module generates a high-speed clock signal as a reference clock signal, which is provided to the measurement unit and the scanning control unit through the high-speed interface module; the programmable logic module reads the control signal and the external angle signal by using the high-speed interface module, interpolates and compensates the signal with a lower sampling rate, synchronously combines the control signal and the external angle signal into the synthesized signal, and then sends the synthesized signal to the linkage unit through the high-speed interface module.

[0019] Further, the reference unit comprises a multi-tooth indexing table and a vacuum adsorption platform; the measurement unit is installed on the multi-tooth indexing table and is provided with an angle reference by the multi-tooth indexing table; the scanning control unit, the frequency synchronization unit and the data processing unit are adsorbed and installed on the vacuum adsorption platform.

[0020] The application further discloses an angle measurement method using the dynamic angle measurement system with synchronized frequency.

[0021] In step S100, the host computer sends 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] Step S300, the measurement unit measures the mechanical scanning unit under the driving of the reference clock signal, generates the external angle signal, and sends the external angle signal to the frequency synchronization unit; the sampling rate of the external angle signal is lower than that of the reference clock signal, and the reference clock signal is obtained by frequency reduction buffering;

[0024] Step S400, the scanning control unit generates the control signal under the driving of the reference clock signal, and sends the control signal to the frequency synchronization unit; the sampling rate of the control signal is lower than that of the reference clock signal;

[0025] Step S500, the frequency synchronization unit performs interpolation frequency raising and fitting compensation on the signal with a lower sampling rate in the external angle signal and the control signal, and finally combines the frequency-raised external angle signal and the control signal to form the synthesized signal and send the synthesized signal to the linkage unit and the data unit;

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

[0027] Step S700, the linkage unit reads and analyzes the synthesized signal, adjusts the working parameters of the measurement unit and the scanning control unit in combination with the error signal, and jumps to step S300 if scanning needs to continue.

[0028] Further, in step S200, the generation of the reference clock signal comprises the steps of,

[0029] Step S201, the frequency synchronization unit generates a high-speed reference clock signal by using a crystal oscillator module;

[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] Step S203, the frequency synchronization unit reads the count value of the respective timer in the measurement unit and the scanning control unit at a preset interval; the timer is driven by the reference clock signal;

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

[0033] Further, in step S400, the generation of the control signal comprises the steps of,

[0034] Step S401, the scanning control unit divides the reference clock signal by using a phase-locked loop to form a control generation signal; the control generation signal drives the generation of the control signal;

[0035] Step S402, the scanning control unit monitors the control generation signal by using the reference clock signal; when the jitter of the control generation signal exceeds a 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 comprises the steps of:

[0037] Step S501, the frequency synchronization unit selects the signal with a lower sampling rate in the external angle signal and the control signal as the to-be-processed signal, and selects the signal with a higher sampling rate as the target signal;

[0038] Step S502, the frequency synchronization unit uses a bilinear interpolation algorithm to interpolate the to-be-processed signal to increase its frequency to match the frequency of the target signal;

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

[0040] Step S504, the to-be-processed signal after fitting and compensation is marked with a timestamp based on the reference clock signal to form a processed signal;

[0041] Step S505, the timestamps of the processed signal and the target signal are aligned, and the processed signal and the target signal are combined into the synthesized signal.

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

[0043] 1、The present application realizes ultra-high frequency high-precision synchronization, between the measurement unit and the scanning control unit, by using a 40MHz synchronization clock input, and by using an interpolation algorithm to align the collected data of the measurement unit and the returned data of the scanning control unit, so that the time synchronization error between the two is reduced from 16ms in the traditional scheme to within 12.5 microseconds, which is improved by 1280 times. After the time synchronization accuracy is greatly improved, the problem of large dynamic angle measurement error caused by frequency mismatch is effectively solved, and the root mean square error (RMSE) of dynamic angle measurement is optimized to 0.15 arc seconds (3σ), which meets the strict requirements of high-precision equipment on measurement synchronization and accuracy.

[0044] 2、In the application, the measurement unit and the scanning control unit realize deep real-time linkage through the linkage unit. In combination with the 40MHz synchronous clock, the states of the measurement unit and the scanning control unit are subjected to high-precision data synchronization, realizing deep real-time interaction and cooperative work of the measurement unit and the scanning control unit. When the measurement angle deviates, the system can quickly respond and adjust the scanning motion parameters based on the accurately synchronized data, and the error compensation time is shortened to sub-millisecond level; at the same time, the measurement parameters are optimized according to the scanning motion state, so that the overall measurement efficiency is improved by 5 to 8 times, and the measurement precision and dynamic response performance are still very high under the ultra-low uniform speed scanning of 0.00005 degrees / second.

[0045] 3、In the application, for the high-precision small market (accounting for less than 5%) such as aerospace, the application realizes 3000 angular second large field of view measurement under 0.1 angular second high precision through the field of view-precision dynamic matching algorithm (F=A*alpha), breaks through the bottleneck that the traditional device is difficult to balance high precision and large field of view, and further improves the measurement reliability and accuracy of the system in these high-precision scenes, and fills the market gap.

[0046] 4、The application also has strong system expansibility, can adapt to photoelectric autocollimator with different precision levels of more than 0.1 angular second, and can realize any combination of 10-100Hz acquisition frequency and more than 200Hz control frequency through adjusting the synchronous working parameters and linkage control algorithm. The flexible configurability of the 40MHz synchronous clock also provides the possibility for future higher frequency data synchronization demand and integration with other high-precision devices, and meets the diversified demand of future high-precision measurement technology development. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a system block diagram of a preferred embodiment of the dynamic angle measurement system using a synchronous frequency of the application;

[0048] Figure 2 is a method flow chart of a preferred embodiment of the angle measurement method of the dynamic angle measurement system using a synchronous frequency of the application.

[0049] In the figure: 100-measurement unit, 200-scanning control unit, 300-linkage unit, 400-frequency synchronization unit, 500-reference unit, 600-data processing unit, 700-upper 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 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 table, 502 - vacuum suction platform. DETAILED DESCRIPTION

[0055] The application will be further described below in connection with specific embodiments. It should be understood that these embodiments are only used to illustrate the application and not to limit the scope of the application. Furthermore, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content of the application, and these equivalent forms also fall within the scope of the appended claims.

[0056] Please refer to Figure 1 The application discloses a dynamic angle measurement system and method using synchronous frequency. As shown in the figure, a preferred embodiment thereof is composed of 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, which provides a man-machine interface of the dynamic angle measurement system, configures working parameters before the system works, and records the working process, etc. 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, directly configures measurement working parameters for the measurement unit 100, indirectly configures scanning working parameters for the scanning control unit 200, directly configures linkage parameters, such as linkage strategy, linkage starting threshold, etc., for the linkage unit 300, and further processes data of the data processing unit 600, etc.

[0058] The host computer 700 itself does not need an angle reference, is not sensitive to angle deviation, can be installed separately, and is connected to other working units through a cable. The measurement unit 100, the scanning control unit 200, the frequency synchronization unit 400 and the data processing unit 600 are all installed on the reference unit 500, and an angle reference is provided by the reference unit 500, so that the measurement unit 200 and the scanning control unit 300 can start working based on a reliable angle reference, and the frequency synchronization unit 400 can be as close as possible to the measurement unit 200 and the scanning control unit 300, reducing transmission delay of the cable.

[0059] The reference unit 500 comprises a multi-tooth indexing table 501 and a vacuum adsorption platform 502. The multi-tooth indexing table 501 has extremely high angular positioning accuracy, with an absolute accuracy of 0.3 arc seconds for 360 degrees and an accuracy of 0.1 arc seconds within 40 degrees, and a flatness of 0.005 mm, thereby providing a high-precision angular reference for the entire measurement system. The vacuum adsorption platform 502 has a flatness controlled between -0.002 mm and +0.002 mm, and has a vacuum adsorption function, which can effectively fix the measured object and reduce external vibration interference, and is suitable for high-precision measurement environments such as clean rooms. Specifically, the measurement unit 100 is installed on the multi-tooth indexing table 501, and the scanning control unit 200, the frequency synchronization unit 400, and the mechanical scanning unit 800 are installed on the vacuum adsorption platform 502 using the vacuum adsorption method. The vacuum adsorption method can not only ensure the fixed position of the scanning control unit 200 and the frequency synchronization unit 400 during work, but also facilitate disassembly and adjustment of the position. During the calibration stage of the dynamic angle measurement system, the multi-tooth indexing table 501 is adjusted to point the measurement unit 100 to the mechanical scanning unit 800, and the initial angle is locked.

[0060] The measurement unit 100 is composed of an optoelectronic autocollimator 101 and a data acquisition module 102. The optoelectronic autocollimator 101 comprises an optical assembly and measures the angular deviation of the measured object using optical principles, with an absolute angular measurement accuracy of ≤0.1 arc seconds, a repeatability of ≤0.04 arc seconds, and a resolution of 0.001 arc seconds. The optoelectronic autocollimator 101 integrates an adaptive diaphragm assembly and a light path fine adjustment mechanism, and the diaphragm aperture can be accurately adjusted within a range of 0.5-5 mm, while the adjustment accuracy of the light path fine adjustment mechanism is 0.01 arc seconds, enabling dynamic adjustment of the field of view range from 50 arc seconds x 50 arc seconds to 3000 arc seconds x 3000 arc seconds. The data acquisition module 102 converts the optoelectronic signal and converts the angular deviation into a digital signal. It is connected with the optoelectronic autocollimator 101, and real-time acquisition of angular measurement data is realized, with a data output frequency of 60 Hz. The collected data is transmitted to the frequency synchronization unit 400. The light path in the optoelectronic autocollimator 101 can be configured, and the specific configuration method is obtained from the measurement working parameters provided by the upper computer 700. The data acquisition module 102 also reads the sampling rate configuration from the measurement working parameters, and generates an external angular signal in the form of a digital signal 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 is composed of a motion control module 201, an angle measurement module 202 and a control interface module 203. The control interface module 203 is the interface of the scanning control unit 200 connecting to the linkage unit 300, the frequency synchronization unit 400 and the host computer 700. According to its linkage strategy, the linkage unit 300 sends new scanning working parameters to the scanning control unit 200 directly through the control interface module 203, so as to change the operation mode of the motion control module 201 and adjust the scanning behavior. The host computer 700 is configured to the motion control module 201 in an indirect way. Specifically, the host computer 700 does not send scanning working parameters directly, but sends the field of view precision to the control interface module 203, which is converted into specific scanning working parameters by the mapping algorithm built-in the control interface module 203, and then configures the motion control module 201. The mapping algorithm automatically configures scanning control parameters including scanning speed (>= 0.00005 degrees / second), field of view range, etc. according to the requirements of different precision. Among them, the field of view range is set according to the capability of the measurement unit 100, i.e. the field of view and precision of the photoelectric autocollimator 101, and the conversion formula is:

[0062] F=A*α

[0063] Wherein, α is the target precision, and A is the field of view range, whose unit is angular second.

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

[0065] The motion control module 201 has high-precision motion control capability, and the scanning control precision is less than or equal to 0.1 angular second, and the data sampling frequency is 8KHz, which can accurately control the scanning motion and support super-low-speed stable scanning with acceleration of 0.003 degrees / second and uniform speed of 0.00005 degrees / second. The motion control module 201 drives under the external clock, and outputs motor control signals to each specific motor in the mechanical scanning unit 800 connected thereto according to the scanning working parameters at a specified sampling frequency (for example, 8KHz), and sends the control signal to the frequency synchronization unit 400. The external reference clock signal comes from the frequency synchronization unit 400. The motor in the mechanical scanning unit 800 acts, and the system rotates the mechanical scanning at a predetermined angular velocity.

[0066] The angle measurement module 202 is composed of multiple sensors. These sensors are arranged near the mechanical scanning unit 800. After calibration with external data (e.g. the measurement unit 100), the mechanical scanning unit 800 angle signal is obtained as an internal angle signal. The internal angle signal is transmitted to the motion control module 201, thereby forming a fast closed-loop control during mechanical scanning. However, the measurement accuracy of the angle measurement module 202 is lower than the external data provided by the measurement unit 100, so in the scenario of high-precision angle mechanical scanning, it is still necessary to work 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 they can share measurement data, control instructions, and state information in real time.

[0068] The linkage control module 302 receives linkage parameter actions from the host computer 700, receives a synthesized signal from the frequency synchronization unit 400, and also receives error feedback from the data processing unit 600. The synthesized signal contains the external angle signal from the measurement unit 100 and the control signal from the scanning control unit 200 after synchronization by the frequency synchronization unit 400. According to 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 working parameters according to the linkage strategy and sends them to the measurement unit 100 and the scanning control unit 200, thereby adjusting the working mode of the measurement unit 100 and the scanning control unit 200, such as making the mechanical scanning lead or lag, or adjusting the external measurement parameters, so that the scanning process is more accurate and smooth. For example, when the photoelectric autocollimator 101 in the measurement unit 100 detects that the angle deviation exceeds the set threshold (such as 0.15 angular seconds), the linkage control module 302 generates compensation instructions and sends them to the motion control module 201 in the scanning control unit 200, adjusting the scanning motion parameters to achieve error compensation; at the same time, according to 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, field of view range, etc.

[0069] The frequency synchronization unit 400 comprises 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, one is to provide a reference clock signal to the outside, and the other is to align the sampling frequency difference between the measurement unit 100 and the scan control unit 200, so that each external angle signal and control signal is aligned one by one, respectively, to generate a composite signal sent to the linkage unit 300, for the linkage unit 300 to provide external correction to the scan control unit 200 according to its linkage strategy.

[0070] The high-speed interface module 401 comprises a plurality of cable interfaces. The low-delay trigger cables are connected to the programmable logic module 402 and the crystal oscillator module 403 through the cable interfaces, and are connected to the measurement unit 100, the scan control unit 200, the linkage unit 300 and the data processing unit 600. The low-delay trigger cables are fixed to the cable interfaces on the high-speed interface module 401 through coaxial bayonet connectors.

[0071] The crystal oscillator module 403 is used to complete the function of providing a reference clock signal, which generates a high-speed reference clock signal by using physical characteristics, 40M in this embodiment, i.e. the signal period is 25ns, which realizes sub-nanosecond level synchronization precision calibration in cooperation with the programmable logic module 402, and theoretically compresses the time synchronization error limit to ≤12.5μs. The high-speed reference clock signal is input to the measurement unit 100 and the scan control unit 200 through the low-delay trigger cables on the high-speed interface module 401, to provide synchronized reference clock signals for them, to provide a unified time reference for both, and to ensure the time consistency of data acquisition and control instructions. The measurement unit 100 and the scan control unit 200 are driven by the same source clock, and the frequency and phase of the reference clock signal are the same. At the same time, the high-speed reference clock signal also serves as the reference clock signal of the programmable logic module 402 itself.

[0072] The programmable logic module 402 adopts an FPGA chip with a built-in double-rate data processing architecture, which is used to complete the function of aligning the external angle signal and the control signal. In this embodiment, the measurement unit 100 outputs the external angle signal at a frequency of 60Hz, while the scan control unit 200 generates the control signal at a speed of 8K. Therefore, the programmable logic module 402 performs interpolation compensation on the external angle signal after reading the control signal and the external angle signal through the high-speed interface module 401. The interpolated external angle signal is up-converted to 8K, so that it can correspond to the control signal one by one, and is synchronized and merged into a composite signal, which is then sent to the linkage unit 300 and the data processing unit 600 through the high-speed interface module.

[0073] The data processing unit 600 reads the synthesized signal from the frequency synchronization unit 400, extracts the synchronized 8KHz angle data and the 8KHz position data of the scanning control system therefrom, and performs time error difference calculation thereon. In the present embodiment, it is required that the time difference of 99% of the sampling points be ≤ 37.5 microseconds (corresponding to 0.3 sampling points of an 8KHz period, based on the high-precision characteristics of a 40MHz synchronization clock); at the same time, the root mean square error (RMSE) is calculated by the dynamic angle error formula Δθ = |θsync,i - Pi|, and it is required that the RMSE be ≤ 0.15 angular seconds (3σ). If the precision 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-performs measurement until the precision requirements are met. In different scenarios, the synthesized signal is also used for special operations, for example, in the semiconductor manufacturing scenario, the harmonic error data within a ±1000 angular second field of view are extracted as error references.

[0074] Referring to Figure 2 The present application also discloses an angle measurement method using the above-mentioned dynamic angle measurement system using a synchronization frequency. A preferred embodiment thereof comprises the following steps:

[0075] Step S1, configuring working parameters.

[0076] The host computer configures the working parameters of the measurement unit, the scanning control unit and the linkage unit. For the measurement unit, the factory parameters include the input test range and the required precision. For the linkage unit, the linkage strategy and the linkage threshold are configured. For the scanning control unit, the configuration information sent by the host computer is processed twice to form the final scanning working parameters. Specifically, the host computer sets the field of view precision A based on the target precision a and the autocollimator precision, and calculates the theoretical field of view range F by the formula F = A * a. For example, when A = 3000 angular seconds and a = 0.1 angular seconds, F = 300 angular seconds. At the same time, other parameters such as the scanning speed V (e.g. 0.0001 degrees / second) are determined in combination with the actual measurement requirements.

[0077] Step S2, sending 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 signals are of the same frequency and phase.

[0079] Step S21, generating a high-speed reference clock signal.

[0080] The frequency synchronization unit includes a crystal oscillator module. The crystal oscillator module utilizes its physical characteristics to generate a high-speed reference clock signal as a source under the drive of an oscillator circuit.

[0081] Step S22, generating the reference clock signal.

[0082] The high-speed reference clock signal generated by the crystal oscillator is shaped to become the reference clock signal. The reference clock signal is transmitted to the measurement unit and the scan control unit respectively through the low-delay trigger cable on the high-speed interface module, as the reference clock signal driving their internal logic actions.

[0083] Step S23, reading back the count value.

[0084] In the measurement unit and the scan control unit, there is a timer respectively. The timer is driven by the same reference clock signal, and in theory, the count values should be exactly the same. But due to the phase jitter in actual operation, the count values will have slight deviations. The frequency synchronization unit reads the count values of the two timers at preset intervals (every 5ms, 200,000 cycles at 40MHz clock) through the low-delay trigger cable on the high-speed interface module.

[0085] Step S24, adjusting the clock phase.

[0086] After the frequency synchronization unit reads back the count values of the two timers, according to the difference between the two, based on the proportional-integral-derivative control algorithm, the phase of the reference clock signal sent to the measurement unit and the scan control unit is adjusted to reduce the difference between the two.

[0087] Step S3, collecting external angle signals.

[0088] The measurement unit takes the reference clock signal from the frequency synchronization unit as the clock input, periodically scans the rotating mechanical module in the mechanical scanning unit, measures its angle and generates the external angle signal. The external angle signal is sent to the frequency synchronization unit through the low-delay trigger cable. Because a certain time is needed for optical measurement to stabilize, there is an upper limit to the sampling rate of the optical measurement result. In this embodiment, the sampling rate is 60Hz, i.e. one external angle signal is generated every second. The sampling action of the measurement unit is driven by the reduced frequency reference clock signal, and the sampling time is related to the phase of the reference clock signal. At the same time of sampling the external angle signal, a timestamp is labeled for it using the reference clock signal. That is, the 40M reference clock signal is labeled, and the actual data sampling is sampled by the reduced frequency clock (60Hz) after eliminating clock jitter through the phase alignment algorithm.

[0089] Step S4, generating control signals and monitoring the sampling reference clock signal.

[0090] The scanning control unit is also driven by the reference clock signal, which generates control signals, on one hand directly controls each motor in the mechanical scanning unit, and on the other hand sends to the frequency synchronization unit through a low-delay trigger cable. The more frequently the control signals are sent, the more accurate the control of the mechanical scanning unit is, but the response speed of the motor also needs to be considered, so the generation frequency is lower than that of the reference clock signal. In the embodiment, the generation speed of the control signal is 8K, that is, eight thousand control signals are generated per second. The action of the scanning control unit to generate the control signal is driven by the reduced frequency of the reference clock signal, and the time of generating the command is related to the phase of the reference clock signal.

[0091] Step S41, generating a control signal.

[0092] Because the generation frequency of the command is lower than that of the reference clock signal, but it is necessary to align the rising edge or falling edge of the reference clock signal, the scanning control unit uses a phase-locked loop to divide the input reference clock signal by 8K to generate a control signal. The phase of the control signal is aligned with that of the reference clock signal, only the frequency is reduced. The scanning control unit triggers the generation of the control signal at the rising edge or falling edge of the control signal, so that the generation of the control signal is the same as that of the reference clock signal, and the delay of the asynchronous clock domain data transmission is eliminated. At the same time of generating the control signal, the reference clock signal is used to mark the time stamp.

[0093] Step S42, monitoring and adjusting the control generation signal.

[0094] The sampling reference clock signal divided out will still jitter due to various errors and disturbances in actual operation. Therefore, the scanning control unit will monitor the control generation signal using the reference clock signal. When it is found that the control generation signal jitter exceeds the sampling threshold preset in the working parameter, the scanning control unit reinitializes the control generation signal, that is, generates the control generation signal based on the reference clock signal again, to ensure that the edge of the control generation signal is aligned with that of the reference clock signal. In the embodiment, the sampling threshold is that the deviation of three consecutive periods is greater than 12.5 microseconds.

[0095] Step S5, generating a synthesis 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 by one. In the embodiment, the external angle signal is 60Hz, and the control signal is 8K. The frequency synchronization unit performs 133.33 times interpolation frequency up-conversion (8000 / 60) and fitting compensation on the low-frequency signal in it, that is, the external angle signal, so that it also reaches the frequency of 8K, while using the high time resolution characteristics of the 40MHz clock to realize the timestamp marking of ±1 nanosecond at each interpolation point. Finally, the up-converted external angle signal and the control signal are corresponded one by one according to the timestamp, and are combined to form a synthetic signal, which is sent to the linkage unit. In the frequency synchronization unit, the interpolation calculation is realized by using the pipeline architecture, and the single interpolation calculation time is compressed to within 25ns by using the 40MHz clock frequency advantage, so as to meet the real-time processing requirements of 8KHz data.

[0097] Step S51, selecting a low-frequency signal.

[0098] The frequency synchronization unit takes the low-frequency external angle signal as the signal to be processed and takes the high-frequency control signal as the target signal. In the subsequent processing process, the frequency of the signal to be processed is raised to be consistent with the frequency of the target signal.

[0099] Step S52, frequency up-conversion of the signal to be processed.

[0100] The frequency synchronization unit uses the bilinear interpolation algorithm to perform frequency up-conversion on the external angle signal, so that its frequency matches the frequency of the control signal, that is, the frequency up-converted external angle signal with a frequency of 8K is obtained. The bilinear interpolation algorithm is:

[0101]

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

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

[0104] T 60Hz = 1 / 60 seconds;

[0105] T 8KHz = 1 / 8000 seconds.

[0106] Step S53, fitting compensation of the signal to be processed.

[0107] The frequency synchronization unit uses a third-order Bezier curve to perform fitting compensation on the frequency up-converted external angle signal, so that it is smoother. The formula of the third-order Bezier curve compensation algorithm is:

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

[0109] Wherein: k coefficient is dynamic calculation:

[0110] And According to 40MHz clock sampling interval adaptive adjustment.

[0111] Step S54, the signal to be processed is marked with a time stamp.

[0112] The frequency synchronization unit marks the time stamp of the signal to be processed after fitting compensation with the reference clock signal as the standard, forming a processed signal. The time stamp in the original external angle signal before interpolation is unchanged, and the time stamp of the new interpolation point formed by interpolation is marked after calculating its time stamp according to the interpolation position combined with the edge of the reference clock signal as the reference.

[0113] Step S55, generate a synthetic signal.

[0114] In the processed signal, the number of data points contained is consistent with the target signal, and both are marked with a time stamp. The original time stamp in the external angle signal and the time stamp of the control signal are both generated based on the 40M reference clock signal, so the time stamp of each data point in the processed signal and each data point in the control signal has a small difference of less than 1 nanosecond. The frequency synchronization unit aligns the data point closest to the time stamp as a data point of the synthetic signal, thereby generating the synthetic signal. The synthetic signal contains 8K data points per second, and each data point contains two sets of data: angle data from the processed external angle signal, and control data from the control signal.

[0115] Step S6, calculate error data.

[0116] The data processing unit reads the synthetic signal, and uses the aligned upsampled external angle signal and the control signal to calculate the control error, i.e. the difference between the expected angle and the actual angle, forming an error signal. The data processing unit feeds back the error signal to the linkage unit.

[0117] Step S7, linkage adjustment.

[0118] The linkage unit reads the combined signal through a low-delay trigger cable, analyzes real-time angle data and control data, combines error signals, and determines whether to intervene in linkage according to working parameters configured by the upper computer. For example, when the deviation between the measured angle and the command angle is greater than 0.15 angular seconds, the linkage unit generates a feedforward compensation command and sends it to the scanning control unit to adjust the motor motion parameters, realizing real-time error compensation. At the same time, according to the motion state of the mechanical scanning unit, the linkage unit can also adjust the adaptive light diaphragm aperture and light path fine adjustment mechanism of the measurement unit, optimize the measurement parameters, and ensure the measurement accuracy. During the linkage process, the 40MHz synchronization clock ensures the high-precision synchronization of the data, making the sending of the compensation command more timely and accurate, and further improving the dynamic response performance of the system. During the process of large-angle scanning of the mechanical scanning unit, the measurement working parameters need to be adjusted multiple times.

[0119] When the scanning is not completed, jump to step S3 to continue signal acquisition and adjustment.

[0120] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, which is based on the content of the specification and drawings, is also included in the patent protection scope of the present application.

Claims

1. A dynamic angle measurement system using synchronous 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 measuring unit, the scanning control unit and the linkage unit to directly or indirectly configure their working parameters; the measuring unit, the scanning control unit and the frequency synchronization unit are all installed on the reference unit, and the reference unit provides an angle reference; The frequency synchronization unit provides a synchronized reference clock signal to the measurement unit, the scanning control unit and the linkage unit; the scanning control unit, driven by the reference clock signal, generates a control signal for controlling the mechanical scanning unit to rotate and scan at a predetermined angular velocity; Driven by the reference clock signal, the measuring 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; the linkage unit adjusts the working parameters of the measuring 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.

2. The dynamic angle measurement system using synchronous frequency according to claim 1, characterized in that: The measuring unit includes a photoelectric autocollimator and a data acquisition module; The photoelectric autocollimator and the data acquisition module read the working parameters set by the host computer; the photoelectric autocollimator configures optical components according to the working 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 the form of a digital signal at a sampling frequency configured by the working parameters, and sends it to the frequency synchronization unit.

3. The dynamic angle measurement system using synchronous frequency according to claim 1, characterized in that: 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 an 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; wherein, the host computer sends the field of view accuracy to the control interface module, which is converted into the specific working parameters by the control interface module; the linkage unit directly sends the working parameters to the control interface module.

4. The dynamic angle measurement system using synchronous frequency according to claim 1, characterized in that: 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 uses the data interaction module to be connected to the measurement unit, the scanning control unit and the frequency synchronization unit; the linkage control module reads the synthetic 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 status of the measurement unit and the scanning control unit.

5. The dynamic angle measurement system using 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 as a reference clock signal, which 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 a lower sampling rate, and then synchronously merges the control signal and the external angle signal into the synthetic signal, which is then sent to the linkage unit through the high-speed interface module.

6. The dynamic angle measurement system using synchronous frequency according to claim 1, characterized in that: The reference unit includes a multi-tooth indexing table and a vacuum adsorption platform; the measuring unit is installed on the multi-tooth indexing table, and the multi-tooth indexing table provides an angle reference; the scanning control unit, the frequency synchronization unit and the data processing unit are adsorbed and installed on the vacuum adsorption platform.

7. An angle measurement method using the dynamic angle measurement system using synchronous frequency according to claim 1, characterized in that: Contains steps: Step S100, using the host computer to send the working parameters to the measurement unit, the scanning control unit, and the linkage unit; 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 to generate the external angle signal, which is sent to the frequency synchronization unit. The external angle signal has a sampling rate lower than that of the reference clock signal and is obtained by down-converting the reference clock signal. 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; Step S500: The frequency synchronization unit performs interpolation up-conversion and fitting compensation on the signal with a lower sampling rate among the external angle signal and the control signal, and finally combines the up-conversion external angle signal and the control signal to form the composite signal, and sends the composite signal to the linkage unit and the data unit. Step S600: the data processing unit reads the synthesized signal, calculates error statistics and generates an error signal, which is fed back to the linkage unit; In step S700 , the linkage unit reads and analyzes the synthesized signal, and adjusts the operating parameters of the measurement unit and the scanning control unit in combination with the error signal; if scanning needs to be continued, the process jumps to step S300 .

8. The angle measurement method using a dynamic angle measurement system using a synchronous frequency according to claim 7, characterized in that: In step S200, the generation of the reference clock signal includes the steps of: Step S201, the frequency synchronization unit generates a high-speed reference clock signal using the included crystal oscillator module; 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 respective 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 compares the count value based on a proportional-integral-derivative control algorithm and adjusts the phase of the reference clock signal.

9. The angle measurement method using a dynamic angle measurement system using a synchronous frequency according to claim 7, characterized in that: In step S400, the control signal is generated, including the steps of: Step S401: the scanning control unit divides the reference clock signal by using a phase-locked loop to generate 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 a sampling threshold, the scanning control unit regenerates the control generation signal based on the reference clock signal.

10. The angle measurement method using a dynamic angle measurement system using a synchronous frequency according to claim 7, 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 among 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; Step S502: The frequency synchronization unit uses a bilinear interpolation algorithm to up-convert and 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 perform fitting compensation on the signal to be processed after the up-conversion interpolation; Step S504, marking a timestamp on the signal to be processed after fitting compensation based on the reference clock signal to form a processed signal; Step S505 , aligning the timestamps of the processed signal and the target signal, and combining the processed signal and the target signal into the synthesized signal.

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