High-frequency disturbance suppression method based on repeated sampling in tilting mirror system

Abstract

The invention discloses a high-frequency disturbance suppression method based on repeated sampling in a tilting mirror system, which is mainly used for tracking and controlling real-time high-frequency disturbance signals and reducing optical axis errors, especially for high-frequency disturbance signals which are limited in sensor sampling and difficult to suppress. The method comprises the steps of identifying whether an unknown signal is aliasing or not through a sampling scheme with a variable sampling period and obtaining frequency information of actual disturbance, and then recovering an actual high-frequency signal component exceeding the Nyquist frequency of a sensor through a repeated sampling algorithm. And finally, designing a multi-rate parallel repetitive control scheme to compensate and suppress high-frequency disturbance signals exceeding the closed-loop bandwidth. The method can effectively solve the problem that tracking control is difficult to realize due to aliasing of high-frequency disturbance signals when sampling of the image sensor is limited, and improves the anti-interference capability of the system.

Description

Technical Field

[0001] The present invention belongs to the field of tracking control, and specifically relates to a high-frequency disturbance suppression method based on repeated sampling in a tilt mirror system, which is mainly used for disturbance suppression of visual axis stabilization in a tilt mirror control system to improve the high-frequency disturbance suppression performance of the system. Background Art

[0002] Tilt mirrors have the advantages of high bandwidth, fast response, and small size, and are widely used in laser communications, telescope systems, astronomical instruments, etc. However, according to the sampling theorem, image sensors with limited sampling frequency are difficult to obtain actual signals exceeding the Nyquist frequency, which directly leads to the difficulty of effective trajectory tracking and disturbance suppression in the tilt mirror control system.

[0003] Commonly used methods such as non-uniform sampling, compressed sensing, and sub-Nyquist sampling algorithms use advanced techniques to accurately capture and reconstruct high-frequency signals while maintaining or reducing the sampling rate. These techniques ensure signal integrity and accurate reconstruction through algorithm optimization, making it possible to sample at conditions below the Nyquist sampling rate, providing new solutions for various practical application scenarios. However, the original purpose of these methods is to recover the real signal under specific conditions including other information such as frequency, amplitude, phase, etc., which requires high real-time performance. In addition, the optimization algorithms used in reconstructing the original signal are complex and computationally intensive, which will bring heavy computational pressure and burden to the digital control system. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a high-frequency disturbance suppression method based on repeated sampling in a tilting mirror system, which adopts a repeated sampling method based on closed-loop error and a parallel repeated control scheme to effectively suppress high-frequency disturbances, simplify the process of high-frequency signal recovery, and has good real-time tracking performance and significant disturbance suppression effect.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for suppressing high-frequency disturbances in a tilt mirror system based on repeated sampling, the method comprising the following steps:

[0007] Step 1: Build a closed-loop feedback control system for the tilt mirror, and adjust the parameters of the proportional-integral controller so that the disturbance information from the base and the optical path of the system is reflected in the closed-loop error, thereby meeting the requirements of the stability and effectiveness of the tilt mirror control system and making the closed loop of the system have a low-frequency disturbance suppression effect.

[0008] Step 2: At the closed-loop error end, a variable period sampling method is applied to identify the error signal spectrum information under different sampling results, and the identified error signal spectrum information is compared to calculate the frequency information of the actual disturbance of the unknown signal;

[0009] Step 3: At the closed-loop error end, the repeated sampling method is used to recover the spectrum components of the actual high-frequency disturbance exceeding the Nyquist frequency of the sensor;

[0010] Step 4: Based on the closed-loop feedback control, a parallel repetitive controller is designed at the closed-loop error end to compensate and suppress the high-frequency disturbance signal restored by repeated sampling.

[0011] Furthermore, the application of the variable period sampling method to identify the error signal spectrum information under different sampling results includes:

[0012] Step 11: Use the original sampling frequency of the sensor The closed-loop error signal is sampled, and Fourier transform is performed on the sampled signal to obtain the frequency of the aliased signal generated by undersampling: , determine the set of aliasing frequencies ;

[0013] Step 12: Design a new sampling frequency ,satisfy , where m is the parameter to be designed, and the frequency of the aliased signal generated after secondary sampling is . Determine the corresponding set of other aliasing frequencies ,when When , is the true frequency of the disturbance signal. , then proceed to the next step;

[0014] Step 13: Take two aliasing frequency sets , And the frequency range of the disturbance signal The intersection of is defined as the set of true frequencies of the disturbance signal When the real frequency set If there is only one element, the one element is determined to be the true frequency of the disturbance signal; if the true frequency set If there is more than one element in , repeat step 12 and determine a set of aliasing frequencies again. , and then take the real frequency set and The intersection of Gather until There is only one frequency element in .

[0015] Further, in order to simplify the calculation process and reduce the calculation complexity, the application of the repeated sampling algorithm to restore the actual high-frequency signal spectrum components exceeding the Nyquist frequency of the sensor includes: the result of the M-fold resampling is derived as follows: ,in and They are the DFT results of M-fold upsampling and M-point rectangular sequence, and k represents the sampling time.

[0016] Furthermore, a multi-rate parallel repetitive control is designed to improve the high-frequency disturbance suppression capability of the closed-loop system. The controller is designed as , respectively, proportional-integral controller and repeat controller Two parts, where the repeating controller , N is the integer order of the repetitive controller, is the fractional order of the repetitive controller, is the delay compensation factor;

[0017] when When the value of is close to 1, the repetitive controller It can effectively reduce the amplification phenomenon of the water bed at non-periodic frequencies and avoid destroying the stability of the system in the high-frequency region;

[0018] For the delay compensation link, it is designed as , used to achieve delay compensation in the high-frequency part and improve the stability of closed-loop control in the high-frequency part;

[0019] The fractional-order delay filter designed as an all-pass type can effectively solve the problem of excessive fluctuation of the disturbance frequency in the high-frequency part, and is used to suppress the disturbance at any characteristic frequency point.

[0020] Furthermore, this method can achieve trajectory tracking and disturbance suppression of signals exceeding the Nyquist frequency of the sensor, effectively reducing closed-loop errors.

[0021] Compared with the existing method, the present invention has the following advantages:

[0022] (1) This control method can effectively improve the system's ability to suppress disturbances exceeding the Nyquist frequency under the condition of limited sensor sampling;

[0023] (2) The control method identifies and recovers high-frequency signals at the closed-loop error end, effectively dealing with disturbances from the base and optical link;

[0024] (3) This control method uses a parallel repetitive control scheme to improve the control performance of the sensitivity function, with better stability and robustness;

[0025] (4) The control structure of the invention is simple, the computational complexity is low, and it is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1It is a schematic diagram of the implementation principle of a high-frequency disturbance suppression method based on repeated sampling in a tilt mirror system of the present invention;

[0027] Figure 2 It is a schematic diagram of repeated sampling of the present invention;

[0028] Figure 3 This is a schematic diagram of the multi-rate parallel repetitive control principle of the present invention;

[0029] Figure 4 This is a comparison chart of the closed-loop error of the system after adding repeated sampling control. DETAILED DESCRIPTION

[0030] The present invention is described below in conjunction with the accompanying drawings and specific embodiments. Those skilled in the art can understand the effects and advantages of the present invention based on the contents disclosed in this specification.

[0031] like Figure 1 As shown, the tilt mirror control system consists of a perturbation tilt mirror, a control tilt mirror, a target (simulated by a laser in the present invention), an image sensor, a repeated sampling control module, etc. When the system is running, the image sensor provides the closed-loop system with a line of sight error, and drives the deflection of the tilt mirror through the control quantity output to keep the target in the center position; in addition, the perturbation tilt mirror can simulate high-frequency disturbances from the optical link, and the repeated sampling control module is used to identify, recover and suppress high-frequency disturbances that exceed the Nyquist frequency of the sensor. The figure also shows an implementation principle diagram of a high-frequency disturbance suppression method based on repeated sampling in a tilt mirror system proposed by the present invention, and its implementation steps are as follows:

[0032] Step 1: Build a closed-loop feedback control system for the tilt mirror, and adjust the parameters of the proportional-integral controller so that all disturbance information from the base and the optical path of the system is reflected in the line of sight error, so as to meet the requirements of stability and effectiveness of the tilt correction system, and make the closed loop of the system have a low-frequency disturbance suppression effect;

[0033] Step 2: At the closed-loop error end, a variable period sampling method is applied to identify the error signal spectrum information under different sampling results, and the identified error signal spectrum information is compared to calculate the frequency information of the actual disturbance of the unknown signal;

[0034] Step 3: At the closed-loop error end, the repeated sampling method is used to recover the actual high-frequency disturbance spectrum components exceeding the Nyquist frequency of the sensor;

[0035] Step 4: Based on the closed-loop feedback control, a parallel repetitive controller is designed at the closed-loop error end to compensate and suppress the high-frequency disturbance signal restored by repeated sampling.

[0036] like Figure 2As shown, the undersampling sequence, repeated sampling process and repeated sampling results proposed by the present invention are shown in FIG. represents convolution. The aliasing frequency is due to undersampling. is the actual frequency, It is the aliasing frequency generated after M times repeated sampling. As can be seen from the figure, after repeated sampling, an undersampled aliasing signal can restore part of the original signal spectrum components in the frequency domain. The law of the restored original signal spectrum components is that the result of upsampling follows the result of rectangular sequence DFT. To distribute the peripheral lines, is the digital angular frequency.

[0037] like Figure 3 As shown, it shows the principle diagram of repeated sampling control of the method proposed in the present invention, wherein the dotted line is low-rate sampling, and the dot-dash line is high-rate sampling. represents the discrete model of the system, and denote the discrete transfer functions of the proportional-integral controller and the repetitive controller, respectively, represents repeated sampling, (kT) and (kMT) represents a discrete signal with sampling intervals of T and MT, is the downsampler, r( ), e( ),u( ) and y( ) represent the input signal, error signal, control signal and output signal of the closed-loop system respectively, Represents system delay: caused by image sensor delay, analog-to-digital / digital-to-analog conversion, and driver hysteresis. In order to unify the characteristics of the system, the delay part is unified into high-rate sampling. According to the block diagram, the sensitivity transfer function can be derived as follows:

[0038] (1)

[0039] Further simplifying the sensitivity transfer function, it is known that At high frequencies, it can be satisfied, and equation (1) can be divided into two parts: proportional-integral control part and repeat control section .in The control performance is limited by the system delay link, which directly limits the effective control bandwidth of the proportional-integral control algorithm and makes it difficult to effectively suppress high-frequency disturbances. To improve the high-frequency trajectory tracking and disturbance suppression performance of the sensitivity function. The repetitive controller with delay compensation characteristics and fractional-order delay filter performance designed by the present invention is , and further obtain the repeated control sensitivity function as ,satisfy and is a fractional-order delay filter, ,when hour, Infinite gain can be obtained, which is of great significance for achieving interference suppression and trajectory tracking at any characteristic frequency point. When the increase is infinitely close to but not equal to 1, Close to 1, that is, 0 dB, it effectively reduces the waterbed amplification of the non-periodic frequency part of the traditional repetitive control.

[0040] In order to demonstrate the effect of the parallel repetitive control algorithm on improving the disturbance suppression capability beyond the sensor Nyquist frequency, a parallel control structure was added and the corresponding controller was designed to conduct position tracking experiments. Figure 4 As shown in the figure, the position error comparison before and after adding repeated sampling and repeated controller is shown. In order to verify the validity of the repeated measurement results, a high-speed sensor is added to collect the actual measurement results. Only when the two sets of results are consistent can the validity of the method be demonstrated. Figure 4 It can be seen that due to the limited sensor sampling, the tracking performance of the actual high-frequency signal is directly restricted. When the repetitive controller is not added (w / o: shown by the dotted line), the closed-loop error of the system is too large and it is difficult to achieve trajectory tracking. After adding the repetitive controller (w: shown by the solid line), the closed-loop error is greatly reduced in both the actual sampling results and the repeated sampling results, which shows that this method is effective for tracking control beyond the Nyquist frequency of the sensor.

[0041] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-frequency disturbance suppression method based on repeated sampling in a tilt mirror system, characterized in that: The method comprises the following steps: Step 1: Build a closed-loop feedback control system for the tilt mirror, and adjust the parameters of the proportional-integral controller so that the disturbance information from the base and the optical path is reflected in the closed-loop error; Step 2: At the closed-loop error end, a variable period sampling method is applied to identify the error signal spectrum information under different sampling results, and the identified error signal spectrum information is compared to calculate the actual disturbance frequency information of the unknown signal; Step 3: At the closed-loop error end, the repeated sampling method is used to recover the actual high-frequency disturbance signal exceeding the Nyquist frequency of the sensor; Step 4: Based on closed-loop feedback control, a parallel repetitive controller is designed at the closed-loop error end to compensate and suppress the actual high-frequency disturbance signal restored by the repeated sampling method.

2. The method for suppressing high-frequency disturbances based on repeated sampling in a tilt mirror system according to claim 1, characterized in that: The method of using the variable period sampling method to identify the error signal spectrum information under different sampling results includes: Step 11: Use the original sampling frequency of the sensor The closed-loop error signal is sampled, and Fourier transform is performed on the sampled signal to obtain the frequency of the aliased signal generated by undersampling: , determine the set of aliasing frequencies ; Step 12: Design a new sampling frequency ,satisfy , where m is the parameter to be designed, and the frequency of the aliased signal generated after secondary sampling is , determine the corresponding set of other aliasing frequencies ,when When , is the true frequency of the disturbance signal; when , then proceed to the next step; Step 13: Take two aliasing frequency sets , And the frequency range of the disturbance signal The intersection of is defined as the set of true frequencies of the disturbance signal , when the real frequency set If there is only one element, the one element is determined to be the true frequency of the disturbance signal; if the true frequency set If there is more than one element in , repeat step 12 and determine another set of aliasing frequencies. , and then take the real frequency set and The intersection of Gather until There is only one frequency element in .

3. The high-frequency disturbance suppression method based on repeated sampling in a tilt mirror system according to claim 1, characterized in that: The method of applying a repeated sampling algorithm to recover the actual high-frequency disturbance signal exceeding the Nyquist frequency of the sensor includes: According to the derivation, the result of resampling is ,in , and They are respectively the DFT results of M-fold repeated sampling, upsampling and M-point rectangular sequence, and k represents the sampling time.

4. The method for suppressing high-frequency disturbance based on repeated sampling in a tilt mirror system according to claim 1, characterized in that: The method of designing a parallel repetitive controller at the closed-loop error end based on closed-loop feedback control to compensate and suppress the actual high-frequency disturbance signal restored by the repeated sampling method includes: Design a multi-rate parallel repetitive controller as , respectively, proportional-integral controller and repeat controller Two parts; Among them, the repeated controller , N is the integer order of the repetitive controller, is the fractional order of the repetitive controller, is the delay compensation factor; when When the value of is close to 1, the repetitive controller Ability to reduce waterbed amplification at non-periodic frequencies; It is a delay compensation link, used to realize delay compensation of high frequency part; The all-pass fractional-order delay filter is designed to suppress disturbances at any characteristic frequency point.

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