Phase regulation and control method and device suitable for zero elimination interference system

Abstract

The invention discloses a phase regulation and control method and device suitable for a zero elimination interference system, and the method employs a piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm and a composite control algorithm, solves a problem that the piezoelectric ceramic hysteresis nonlinear high-precision fitting operation amount is large, improves the piezoelectric ceramic control precision, and improves the precision of the piezoelectric ceramic hysteresis nonlinear high-precision fitting operation. The operand is simplified, and factors such as system errors and environmental disturbance are suppressed. The invention further provides a corresponding phase regulation and control device based on the method, and the device comprises a PC terminal, a controller, a piezoelectric amplifier, a piezoelectric actuator, a phase regulation reflector, a capacitive displacement sensor, a sensor controller and a zero elimination interference system, and has the advantages of high precision, small operand and adjustable and controllable phase.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical imaging, and in particular relates to a phase control method and device suitable for a nulling interference system. Background Art

[0002] The zero-cancellation interferometry technology utilizes the design of the interference system to introduce a π phase shift on one interferometer arm and no phase shift on the other interferometer arm, thereby suppressing or eliminating starlight and achieving astronomical high-contrast imaging. This is beneficial for studying and analyzing the physical properties of planets, and is conducive to a better understanding of the formation of the universe, the search for habitable exoplanets, and the search for new planets suitable for human survival.

[0003] The current methods for achieving null interference are: using two telescopes to form the simplest interferometer, and changing the distance and direction between the two telescopes to make the delay reach half the wavelength; or adding a glass plate with a thickness of e=λ0 / [2(n-1)] to one of the interference arms of the Bracewell null interferometer, where λ0 is the wavelength and n is the refractive index of the glass plate, to obtain a π phase shift at a specific wavelength λ0, but the nulling effect drops rapidly at λ≠λ0; or using multiple telescopes for achromatic interferometric observations, and almost achieving a π phase shift by balancing the slight difference in the air path with the path difference between the two zinc selenide elements; or using the geometric phase method or phase grating for interference nulling.

[0004] In order to achieve more precise phase control and obtain more phase information, piezoelectric ceramics can be used as driving devices. Piezoelectric ceramics are widely used in precision and ultra-precision machining, nanomanipulation, measurement and other fields due to their advantages such as high resolution and large output force. However, in practical applications, piezoelectric ceramics have inherent characteristics such as hysteresis and creep, which lead to the instability of the piezoelectric ceramic micro-displacement output system, among which hysteresis has the greatest impact. Therefore, in order to achieve precise control of piezoelectric ceramics, it is necessary to analyze and control their hysteresis characteristics.

[0005] For the existing modeling methods of piezoelectric ceramic hysteresis phenomenon, such as Preisach hysteresis, Prandtl-Ishlinskii (PI) hysteresis, Duhem hysteresis, polynomial hysteresis and other commonly used models, the Preisach model parameters are difficult to identify, the inverse model is difficult to solve, the PI model is difficult to calculate, and the Duhem model modeling and parameter identification are relatively difficult. Compared with the above models, the polynomial hysteresis model has the advantages of small amount of calculation, simple modeling, and easy inversion. However, the existing polynomial model has the disadvantage of large amount of calculation when fitting with high precision. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a phase control method and device suitable for a zero interference elimination system, which improves the hysteresis fitting accuracy, simplifies the amount of calculation, improves the control accuracy of the phase and makes the phase adjustable. In order to achieve the above purpose, the technical solution adopted by the present invention is as follows: A phase control method applicable to a nulling interference system, the method comprising the following steps: Step S1: The PC end, the controller, the piezoelectric amplifier, the piezoelectric actuator, and the phase adjustment mirror are sequentially connected in communication, and the capacitive displacement sensor attached to the phase adjustment mirror is sequentially connected in communication with the sensor controller and the PC end to form a phase control device of the zero interference elimination system; Step S2: Under the condition that the phase control device is open-loop, the PC sends a command, and a high-voltage signal is output after passing through the controller and the piezoelectric amplifier to control the piezoelectric actuator to generate displacement. The capacitive displacement sensor and the sensor controller transmit the measured displacement change to the PC, record the displacement change, and obtain mapping data including the input voltage and output displacement of the piezoelectric actuator; Step S3: performing an initial third-order polynomial fitting based on the obtained mapping data, determining the voltage segmentation points according to the fitted error data changes and the system's motion stroke, fitting each segment of the curve using the piezoelectric ceramic hysteresis nonlinear curve segmentation self-matching polynomial fitting algorithm, and modeling the piezoelectric ceramic hysteresis nonlinear curve; Step S4: According to the established piezoelectric ceramic hysteresis nonlinear curve model, based on a composite control algorithm consisting of feedforward control and PID control, the output displacement of the established piezoelectric ceramic hysteresis nonlinear curve model is controlled to obtain the error range of each component of the phase control device; Step S5: Under the condition that the phase control device is closed-loop, based on the error range of each device, the PC sends instructions to control the phase of the zero-cancellation interference system.

[0007] Furthermore, the step S3 of modeling the piezoelectric ceramic hysteresis nonlinear curve includes: Step S31: performing initial fitting on the hysteresis rise curve and the hysteresis fall curve respectively using a third-order polynomial expression according to the mapping data obtained in step S2; Step S32: Under the same voltage, calculate the difference between the displacement data in the obtained mapping data and the displacement obtained by the initial fitting of the third-order polynomial, find the pre-selected voltage segmentation point according to the size of the displacement difference corresponding to each voltage point and the change of the displacement difference between the two sampling points before and after the voltage point, and then determine the final voltage segmentation point according to the system motion stroke, and the final voltage segmentation point satisfies: in the two curves before or after the final voltage segmentation point, the fitting error of at least one curve is greater than the preset threshold; Step S33: according to the final voltage segmentation point, the hysteresis nonlinear curve is divided into two segments of the final voltage segmentation point plus the number of segments, and each segment of the curve is respectively fitted with a first-order polynomial and a polynomial fitting up to an eighth-order polynomial by using a segmented self-matching polynomial fitting algorithm. In the self-matching fitting process, the highest polynomial fitting term and polynomial expression of each segment of the curve are self-matched based on the fitting tolerance range of the system; Step S34: Based on the obtained polynomial expression of each curve segment, a piezoelectric ceramic hysteresis nonlinear curve model is established.

[0008] Further, the step S4 includes: Step S41: According to the piezoelectric ceramic hysteresis nonlinear curve model established in step S3, the obtained input voltage and output displacement data are reversed, that is, a feedforward control expression is obtained according to the input displacement-output voltage data using a piecewise self-matching polynomial fitting algorithm; Step S42: taking the difference between the expected output value of the PC and the feedback signal of the sensor controller as the input value of the PID algorithm to establish PID control; Step S43: Using the composite control algorithm established in steps S41 and S42, the PID control parameters of the phase control device are set based on the errors of various components in the system and external disturbances to control the output displacement of the system.

[0009] On the other hand, the present invention also provides a phase control device suitable for a zero interference cancellation system, the device comprising a PC terminal, a controller, a piezoelectric amplifier, a piezoelectric actuator, a phase adjustment reflector, a capacitive displacement sensor, a sensor controller and a zero interference cancellation system. Wherein, under the condition that the phase control device is open-loop, the PC end sends a command, outputs a high-voltage signal after passing through the controller and the piezoelectric amplifier, controls the piezoelectric actuator to generate displacement, receives the displacement change measured by the capacitive displacement sensor and the sensor controller, records the displacement change, and obtains mapping data including the input voltage and output displacement of the piezoelectric actuator; An initial third-order polynomial fitting is performed based on the obtained mapping data. The voltage segmentation points are determined according to the fitted error data changes and the system's motion stroke. Each segment of the curve is fitted using the piezoelectric ceramic hysteresis nonlinear curve segmentation self-matching polynomial fitting algorithm to model the piezoelectric ceramic hysteresis nonlinear curve. According to the established piezoelectric ceramic hysteresis nonlinear curve model, based on a composite control algorithm consisting of feedforward control and PID control, the output displacement of the established piezoelectric ceramic hysteresis nonlinear curve model is controlled to obtain the error range of each component of the phase control device; Under the closed-loop condition of the phase control device, based on the error range of each device, the PC sends instructions again to control the phase of the zero-cancellation interference system.

[0010] The beneficial effects of the present invention are: The present invention utilizes a piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm. After the piezoelectric ceramic hysteresis curve is segmented, a polynomial expression of each segment of the curve is self-matched, thereby improving the fitting accuracy, simplifying the amount of calculation, and improving the phase control accuracy of the zero interference elimination system. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG1 is a flow chart of a phase control method applicable to a nulling interference system according to the present invention; FIG2 is a schematic diagram of a phase control device applicable to a nulling interference system of the present invention; FIG3 is a signal trend diagram of a phase control device applicable to a zero-cancellation interference system of the present invention; FIG4 is a flow chart of a piecewise self-matching polynomial fitting algorithm for a piezoelectric ceramic hysteresis nonlinear curve according to the present invention; FIG5 is a diagram showing the effect of the initial fitting of the hysteresis nonlinear curve by the third-order polynomial of the present invention; FIG6 is a diagram showing the effect of the piecewise self-matching polynomial fitting algorithm for the hysteresis nonlinear curve of piezoelectric ceramics according to the present invention; FIG7 is a schematic diagram of a phase control method applicable to a nulling interference system of the present invention; FIG8 is a diagram showing the simulation results of phase control accuracy based on the method of the present invention.

[0012] Reference numerals: 1. PC terminal; 2. Controller; 3. Piezoelectric amplifier; 4. Piezoelectric actuator; 5. Capacitive displacement sensor; 6. Sensor controller; 7. Zero interference system; 71. Phase adjustment reflector; 72. Reflector; 73. Beam combiner; 74. Fixed corner cube prism; 75. Telescope. DETAILED DESCRIPTION

[0013] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] The present invention proposes a phase control method and device suitable for a nulling interference system, which are used to achieve the adjustment of the phase of the nulling interference system from 0 to 2π. The movement stroke required by the system during phase control is 0 to 3μm. The maximum fitting error of the hysteresis nonlinear curve modeling allowed by the system during phase control is 2nm, and the phase control accuracy requirement is ±20nm.

[0015] like Figure 1 The flow chart of a phase control method suitable for a zero-elimination interference system is shown in FIG. Figure 2The schematic diagram of a phase control device suitable for a nulling interference system is shown. The device uses a PC terminal 1, a controller 2, a piezoelectric amplifier 3, a piezoelectric actuator 4, a capacitive displacement sensor 5, a sensor controller 6 and a phase adjustment reflector 71 to control the phase of the nulling interference system 7. The nulling interference system 7 includes a phase adjustment reflector 71, a reflector 72, a beam combiner 73, a fixed corner cube prism 74 and a telescope 75. It is a nulling interference system composed of two telescopes 75, and its principle is the Bracewell nulling interference principle. In the whole device, the PC terminal 1 is connected to the controller 2, the controller 2 is connected to the piezoelectric amplifier 3, the piezoelectric amplifier 3 is connected to the piezoelectric actuator 4, the phase adjustment reflector 71 should be consistent with the displacement movement of the piezoelectric actuator 4, the capacitive displacement sensor 5 attached to the phase adjustment reflector 71 is connected to the sensor controller 6, and the sensor controller 6 is connected to the PC terminal 1. Without loss of generality, the device can perform the following steps involved in a phase control method suitable for a nulling interference system.

[0016] The signal trend of the phase control device of the zero-cancellation interference system is shown in the figure Figure 3 As shown, first, the PC terminal 1 compiles the expected output value, the signal fed back by the sensor controller 6 and the composite control algorithm into the controller 2. After calculation by the algorithm in the controller 2, the corresponding low-voltage control signal is output to the piezoelectric amplifier 3. After the piezoelectric amplifier 3, the high-voltage signal is transmitted to the piezoelectric actuator 4 to drive it to undergo a slight deformation. The slight deformation produced by the piezoelectric actuator 4 will drive the phase adjustment mirror 71 to undergo a slight displacement, thereby changing the optical delay line of the zero-cancelling interference system and playing a role in phase regulation. The movement of the phase adjustment mirror 71 will change the displacement signal received by the capacitive displacement sensor 5. The sensor controller 6 receives the displacement signal from the capacitive displacement sensor 5 and feeds it back to the PC terminal 1, thereby realizing closed-loop control of the entire system.

[0017] For details, please refer to Figure 1 A phase control method suitable for a zero-cancellation interference system comprises the following steps: Step S1: Connecting various devices according to the circuit to form a phase control device of the zero interference elimination system; Step S2: Under the condition of the system open loop, the PC terminal 1 sends a command, the piezoelectric actuator 4 generates a corresponding displacement, the capacitive displacement sensor 5 and the sensor controller 6 transmit the measured displacement change to the PC terminal 1, record the displacement change, and obtain the mapping data of the input voltage and output displacement of the piezoelectric actuator 4; Step S3: performing an initial third-order polynomial fitting based on the obtained mapping data, determining the voltage segmentation points according to the fitted error data changes and the system's motion stroke, fitting each segment of the curve using the piezoelectric ceramic hysteresis nonlinear curve segmentation self-matching polynomial fitting algorithm, and modeling the piezoelectric ceramic hysteresis nonlinear curve; Step S4: According to the established piezoelectric ceramic hysteresis nonlinear curve model, based on a composite control algorithm consisting of feedforward control and PID control, the output displacement of the established piezoelectric ceramic hysteresis nonlinear curve model is controlled to obtain the error range of each component of the phase control device; Step S5: Under the closed-loop condition of the phase control device, based on the established piezoelectric ceramic hysteresis nonlinear curve model and composite control algorithm, as well as the error range of each device, the PC sends instructions to control the phase of the zero-cancellation interference system.

[0018] When implementing phase control, the piezoelectric ceramic hysteresis nonlinear curve must first be modeled, and then the system phase control simulation must be performed. Based on the simulation results, it is determined whether the control algorithm and the selection of each device meet the system requirements. A piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm is used to model the piezoelectric ceramic hysteresis nonlinear curve. The modeling flowchart is shown below. Figure 4 The specific steps are: Step S31: Under the open-loop condition of the system, the input and output data of the rising hysteresis curve and the falling hysteresis curve of the piezoelectric ceramic are collected, such as Figure 5 The rising hysteresis sampling point curve and the falling hysteresis sampling point curve are respectively initially fitted to the rising hysteresis curve and the falling hysteresis curve according to the collected data using a third-order polynomial expression (here, such as least squares fitting), as shown in FIG. Figure 5 The third-order fitting curve of the rising process and the third-order fitting curve of the falling process; Step S32: Under the same voltage, calculate the difference between the displacement of the hysteresis sampling point and the third-order fitting displacement, find the pre-selected voltage segmentation point according to the size of the displacement difference corresponding to each voltage point and the change of the displacement difference between the two sampling points before and after the voltage point, and then determine the final voltage segmentation point according to the system motion stroke. The final voltage segmentation point satisfies the following conditions: in the two curves before or after the final voltage segmentation point, at least one curve has a large fitting error, that is, the fitting effect is not good, that is, it exceeds the preset threshold, and the system fitting tolerance curve is as follows: Figure 5 The tolerance range curve of 2 nm is shown in the figure; Step S33: According to the selected final voltage segmentation point, the hysteresis sampling point curve is divided into two segments of the final voltage segmentation point number plus the segmented self-matching polynomial fitting algorithm of the piezoelectric ceramic hysteresis nonlinear curve proposed in the present invention, and each segment of the curve is respectively fitted with a first-order polynomial up to an eighth-order polynomial, i.e., j≤8, and n=j is set as the highest order of the polynomial fitting. The polynomial fitting expression is: y i =a1U i n +a2U i n-1 +…+ a n+1 , where i = 1…N, N is the number of hysteresis sampling points in the fitting segment after the hysteresis sampling point curve is segmented, U i is the voltage data corresponding to the hysteresis sampling point, y i is the displacement value of the polynomial fit.

[0019] In the self-matching fitting process, the maximum fitting error required by the system is used as the criterion. Figure 5 The tolerance range curve of the fitting is 2 nm, and the maximum error C of each fitting order is j Compared with the maximum fitting error required by the system, if C j ≤The maximum fitting error required by the system, then j at this time is the highest term of the fitting segment at this moment, otherwise, j++, and a new round of polynomial fitting is performed. If j>8, it means that the first-order to eighth-order polynomial fitting cannot meet the system's requirement for the maximum fitting error. At this time, reselect the segmentation points or add segmentation points, and then use the piezoelectric ceramic hysteresis nonlinear curve segmentation self-matching polynomial fitting algorithm to self-match the highest polynomial fitting term and polynomial expression of each segment of the curve; Step S34: According to step S33, a polynomial expression of each curve segment is obtained, and a piezoelectric ceramic hysteresis nonlinear curve model is established. The fitting effect of the piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm is shown in FIG6 .

[0020] Figure 5 As shown, the initial third-order polynomial expression is: Rising stage: y=-1.7488 10 -6 U 3 +2.7458 10 -4 U 2 +0.0654U-0.0471; Descending stage: y=2.4510 10 -7 U 3 -3.3103 10 -4 U2 +0.1104U+0.1478; where U is the voltage at the hysteresis sampling point, and y is the displacement value of the third-order polynomial fitting.

[0021] As can be seen from Figure 5, between the movement stroke of 0 and 3μm, many fitting errors in the initial fitting of the third-order polynomial are greater than 2 nanometers. According to the fitting effect, 15V is selected as the first undetermined voltage segmentation point of the piezoelectric ceramic rising hysteresis sampling point curve, and 30V is selected as the first undetermined voltage segmentation point of the piezoelectric ceramic falling hysteresis sampling point curve. According to the movement stroke, 45V is used as the second undetermined voltage segmentation point of the piezoelectric ceramic rising hysteresis sampling point curve, and the displacement corresponding to 30V of the piezoelectric ceramic falling hysteresis sampling point curve is greater than 3μm. Since in the piezoelectric ceramic rising hysteresis sampling point curve, the stroke corresponding to the 45V voltage includes the stroke corresponding to the 15V voltage, finally, 45V is selected as the voltage segmentation point Ua of the piezoelectric ceramic rising hysteresis sampling point curve, and 30V is selected as the voltage segmentation point Ub of the piezoelectric ceramic falling hysteresis sampling point curve. Among them, the maximum fitting error between the rising hysteresis sampling point curve 0~45V and the falling hysteresis sampling point curve 30~0V is 2 nanometers, and the maximum fitting error between the rising hysteresis sampling point curve 45~150V and the falling hysteresis sampling point curve 150~30V is 30 nanometers. The piezoelectric ceramic hysteresis nonlinear curve is fitted using the piecewise self-matching polynomial fitting algorithm. The fitting diagram is shown in Figure 6. The fitting error is within 2 nanometers in the displacement of 0~3μm. The fitting expression is: 0~45V (including 45V) rising stage: y1=-7.7761 10 -6 U 3 +8.9831 10 -4 U 2 +0.0482U+0.0153; 45~150V rising stage: y1=-2.2754 10 -4 U 2 +0.1093U-1.1826; 30~0V (including 30V) descending stage: y1=-6.7234 10 -6 U 3 +2.3373 10 -4 U 2 +0.0987U+0.1830; 150~30V descending stage: y1=4.2649 10 -7 U 3 -3.7789 10 -4 U 2+0.1139U+0.0866. Wherein, U is the voltage at the hysteresis sampling point, and y1 is the displacement value fitted by the piecewise self-matching polynomial fitting algorithm of the hysteresis nonlinear curve of the piezoelectric ceramic.

[0022] From the above content, it can be concluded that the piecewise self-matching polynomial fitting algorithm for the hysteresis nonlinear curve of piezoelectric ceramics improves the modeling accuracy of the system within the motion range, while the amount of calculation is simplified.

[0023] Then, the composite control algorithm is used to control the established piezoelectric ceramic hysteresis nonlinear curve model.

[0024] Feedforward control, that is, swapping the input and output data collected in the experiment, and then fitting it with the piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm to establish an inverse model, in which the maximum error of the voltage fitting in the rising stage is 0.2V. Since the error of the voltage fitting in the falling stage cannot be less than 0.2V in the fitting of the first-order to eighth-order polynomials, the falling hysteresis sampling point curve is segmented, so that the maximum error of the voltage fitting in the falling stage of 3.174~0.183μm is 0.01V, and the maximum error of the voltage fitting in the falling stage of 10.102~3.174μm is 0.3V. The expression of the inverse model is: Rising stage: U n =-4.3919 10 -4 x 6 +0.0146x 5 -0.1848x 4 +1.2104x 3 -4.2886x 2 +19.7618x-0.2337; descending stage 3.174~0.183μm (including 3.174μm): U n =0.0670x 3 -0.2690x 2 +10.2168x-1.8611; descending stage 10.102~3.174μm: U n =0.0029x 6 -0.1155x 5 +1.8629x 4 -15.6352x 3 +72.2248x 2 -162.3499x+162.7711. Among them, x is the displacement of the hysteresis sampling point, U n is the voltage obtained using the inverse model expression. The PID control expression used is: U(k)=K p e(k)+Kd [e(k) - e(k-1)] + K i ∑e(k), where e(k) is the deviation at this moment, and e(k-1) is the deviation at the previous moment. are the proportional, integral and differential coefficients respectively, ∑e(k) is the accumulated error, and U(k) is the output voltage of the PID control algorithm at this moment.

[0025] The principle diagram of the phase control method is shown in FIG7 , and the specific steps are as follows: Step S41, convert the expected displacement into the expected displacement x(k) according to the optical path difference and phase difference formula x(k)=λθ / (2π), where λ is the wavelength and θ is the phase difference. Compare the displacement x(k) at the current moment with the displacement x(k-1) at the previous moment to determine whether it is in an ascending state or a descending state; According to the rising or falling state and the discriminant of the displacement segmentation point, it enters different expressions. That is, in the rising stage, x enters the rising stage expression: -4.3919 10 -4 x 6 +0.0146x 5 -0.1848x 4 +1.2104x 3 -4.2886x 2 +19.7618x-0.2337; in the descending stage, if x(k)≤x2(x2=3.174μm), x enters the descending stage of 3.174~0.183μm. In the expression: 0.0670x 3 -0.2690x 2 +10.2168x-1.8611, on the contrary, x enters the stage of decreasing 10.102~3.174μm. In the expression: 0.0029x 6 -0.1155x 5 +1.8629x 4 -15.6352x 3 +72.2248x 2 -162.3499x+162.7711, the output value obtained and the voltage adjusted by PID are combined and divided by k, k=30, which is equal to the amplification factor K of the piezoelectric amplifier, and the low-voltage signal U1 is output. Figure 7 The letters representing coefficients such as a1, a2, d2, c1, etc. are consistent with the coefficients in the above expression; After magnification of The piezoelectric amplifier outputs a high-voltage amplified signal U2=KU1, where K=30; Since the piezoelectric ceramic actuator itself is a capacitive material, it is generally regarded as a capacitor in the entire circuit. The entire drive circuit can be regarded as a Therefore, according to the formula U m = (1-e -t / （RC） ) U2,, the driving voltage U applied to the piezoelectric ceramic is obtained m , where R is the equivalent resistance of the driving circuit and C is the equivalent capacitance of the piezoelectric actuator. From the formula, it can be seen that as time increases, e -t / （RC） decays to 0 quickly, so after a short time, U m =U2; According to the discriminant of the rising or falling state and the voltage segmentation point, and the piecewise polynomial expression of fitting the piezoelectric ceramic hysteresis nonlinear curve obtained above, the input voltage U m Entering different expressions, in the rising stage, if U m ≤Ua (Ua=45V), enter the expression: -7.7761 10 -6 U 3 +8.9831 10 -4 U 2 +0.0482U+0.0153; otherwise, enter the expression: -2.2754 10 -4 U 2 +0.1093U-1.1826; in the descending stage, if U m ≤Ub (Ub=30V), enter the expression: -6.7234 10 -6 U 3 +2.3373 10 -4 U 2 +0.0987U+0.1830; otherwise, enter the expression: 4.2649 10 -7 U 3 -3.7789 10 -4 U 2 +0.1139U+0.0866, the corresponding output displacement is obtained , Figure 7 The letters representing coefficients such as q1, p2, g2, and w1 in are consistent with the coefficients in the above expressions; In step S42, the sensor controller 6 feeds back the output displacement to the system, and uses the difference between the expected displacement and the output displacement as the input of the PID control algorithm. The entire system forms a closed-loop feedback system to suppress system errors, external disturbances and other factors that interfere with the stability of the system. In the flow chart, m, n, f, v, and l are possible errors in various parts of the device.

[0026] Step S43, set the PID parameter to K p =4, K i =6, K d =0, the errors of each part of the system components are m=0.001V, n=0.1V, f=0.1V, v=2nm, l=5nm, the equivalent resistance R and the equivalent capacitance C are R=100Ω, C=3.1μF respectively, and the amplification factor of the piezoelectric amplifier is K=30.

[0027] The phase of the zero interference system can be adjusted from 0 to 2π, that is, the displacement can be moved from 0 to 3 μm. The simulation diagram of the phase adjustment accuracy of the system is shown in the figure below. Figure 8 As shown in the figure, when the system displacement achieves an upward and downward movement of 0~3μm, ┼ represents the expected output displacement, • represents the simulated output displacement, and the two curves represent the tolerance range of the system control accuracy, which can be obtained from Figure 8 It can be seen that the simulation output displacement is almost within the tolerance range of the system control accuracy.

[0028] 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 phase control method suitable for a nulling interference system, characterized in that: The method comprises the following steps: Step S1: The PC end, the controller, the piezoelectric amplifier, the piezoelectric actuator, and the phase adjustment mirror are sequentially connected in communication, and the capacitive displacement sensor attached to the phase adjustment mirror is sequentially connected in communication with the sensor controller and the PC end to form a phase control device of the zero interference elimination system; Step S2: Under the condition that the phase control device is open-loop, the PC sends a command, and a high-voltage signal is output after passing through the controller and the piezoelectric amplifier to control the piezoelectric actuator to generate displacement. The capacitive displacement sensor and the sensor controller transmit the measured displacement change to the PC, record the displacement change, and obtain mapping data including the input voltage and output displacement of the piezoelectric actuator; Step S3: performing an initial third-order polynomial fitting based on the obtained mapping data, determining the voltage segmentation points according to the fitted error data changes and the system's motion stroke, fitting each segment of the curve using the piezoelectric ceramic hysteresis nonlinear curve segmentation self-matching polynomial fitting algorithm, and modeling the piezoelectric ceramic hysteresis nonlinear curve; Step S4: According to the established piezoelectric ceramic hysteresis nonlinear curve model, based on a composite control algorithm consisting of feedforward control and PID control, the output displacement of the established piezoelectric ceramic hysteresis nonlinear curve model is controlled to obtain the error range of each component of the phase control device; Step S5: Under the condition that the phase control device is closed-loop, based on the error range of each device, the PC sends instructions to control the phase of the zero-cancellation interference system.

2. A phase control method applicable to a nulling interference system as claimed in claim 1, characterized in that: The step S3 of modeling the piezoelectric ceramic hysteresis nonlinear curve comprises: Step S31: performing initial fitting on the hysteresis rise curve and the hysteresis fall curve respectively using a third-order polynomial expression according to the mapping data obtained in step S2; Step S32: Under the same voltage, calculate the difference between the displacement data in the obtained mapping data and the displacement obtained by the initial fitting of the third-order polynomial, find the pre-selected voltage segmentation point according to the size of the displacement difference corresponding to each voltage point and the change of the displacement difference between the two sampling points before and after the voltage point, and then determine the final voltage segmentation point according to the system motion stroke, and the final voltage segmentation point satisfies: in the two curves before or after the final voltage segmentation point, the fitting error of at least one curve is greater than the preset threshold; Step S33: according to the final voltage segmentation point, the hysteresis nonlinear curve is divided into two segments of the final voltage segmentation point plus the number of segments, and each segment of the curve is respectively fitted with a first-order polynomial and a polynomial fitting up to an eighth-order polynomial by using a segmented self-matching polynomial fitting algorithm. In the self-matching fitting process, the highest polynomial fitting term and polynomial expression of each segment of the curve are self-matched based on the fitting tolerance range of the system; Step S34: Based on the obtained polynomial expression of each curve segment, a piezoelectric ceramic hysteresis nonlinear curve model is established.

3. A phase control method applicable to a nulling interference system as claimed in claim 1, characterized in that: The step S4 comprises: Step S41: According to the piezoelectric ceramic hysteresis nonlinear curve model established in step S3, the obtained input voltage and output displacement data are reversed, that is, a feedforward control expression is obtained according to the input displacement-output voltage data using a piecewise self-matching polynomial fitting algorithm; Step S42: taking the difference between the expected output value of the PC and the feedback signal of the sensor controller as the input value of the PID algorithm to establish PID control; Step S43: Using the composite control algorithm established in steps S41 and S42, the PID control parameters of the phase control device are set based on the errors of various components in the system and external disturbances to control the output displacement of the system.

4. A phase control device suitable for a nulling interference system, characterized in that: The device includes a PC terminal, a controller, a piezoelectric amplifier, a piezoelectric actuator, a phase adjustment reflector, a capacitive displacement sensor, a sensor controller and a zero interference system; Wherein, under the condition that the phase control device is open-loop, the PC end sends a command, outputs a high-voltage signal after passing through the controller and the piezoelectric amplifier, controls the piezoelectric actuator to generate displacement, receives the displacement change measured by the capacitive displacement sensor and the sensor controller, records the displacement change, and obtains mapping data including the input voltage and output displacement of the piezoelectric actuator; An initial third-order polynomial fitting is performed based on the obtained mapping data. The voltage segmentation points are determined according to the fitted error data changes and the system's motion stroke. Each segment of the curve is fitted using the piezoelectric ceramic hysteresis nonlinear curve segmentation self-matching polynomial fitting algorithm to model the piezoelectric ceramic hysteresis nonlinear curve. According to the established piezoelectric ceramic hysteresis nonlinear curve model, based on a composite control algorithm consisting of feedforward control and PID control, the output displacement of the established piezoelectric ceramic hysteresis nonlinear curve model is controlled to obtain the error range of each component of the phase control device; Under the closed-loop condition of the phase control device, based on the error range of each device, the PC sends instructions again to control the phase of the zero-cancellation interference system.

Images