Phase control method and device suitable for nulling interference system

Abstract

The application discloses a phase control method and device suitable for a zero cancellation interference system. The method utilizes a piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm and a composite control algorithm, solves the problem of large operation amount of high-precision fitting of piezoelectric ceramic hysteresis nonlinearity, improves the control precision of the piezoelectric ceramic, simplifies the operation amount, and suppresses system errors, environmental disturbances and other factors. Based on the above method, a corresponding phase control device is also provided. The device comprises a PC end, a controller, a piezoelectric amplifier, a piezoelectric actuator, a phase adjustment mirror, a capacitive displacement sensor, a sensor controller and a zero cancellation interference system, and has the advantages of high precision, small operation amount and adjustable phase.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical imaging, and particularly relates to a phase control method and device suitable for a nulling interferometer system. BACKGROUND

[0002] The nulling interferometer technology utilizes the design of an interference system to introduce a pi phase shift on one interference arm and not introduce a phase shift on the other interference arm, so as to suppress or eliminate starlight, realize astronomical high-contrast imaging, and be beneficial to the research and analysis of the physical properties of planets and the 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 realizing nulling interference include: the simplest interferometer composed of two telescopes, the delay of which reaches one-half wavelength by changing the distance and direction between the two telescopes; a glass plate with a thickness e = λ0 / [2(n-1)] can be added to one interference arm of the Bresenham nulling interferometer, where λ0 is the wavelength and n is the refractive index of the glass plate, so that a pi phase shift can be obtained at a specific wavelength λ0, but the nulling effect rapidly decreases at λ≠λ0; multiple telescopes can be used for achromatic interference observation, and a pi phase shift can be almost achieved by balancing the small differences in air paths and the path differences between two zinc selenide elements; the geometric phase method or phase grating can also be used for interference nulling.

[0004] In order to realize more accurate phase control and obtain more phase information, piezoelectric ceramics can be used as a driving device. Piezoelectric ceramics are widely used in precise and ultra-precise machining, nanomanipulation, measurement, etc. due to their high resolution and large output force. However, in practical applications, piezoelectric ceramics have inherent characteristics such as hysteresis and creep, which cause the piezoelectric ceramic micro-displacement output system to be unstable, and the hysteresis has the greatest impact. Therefore, in order to realize accurate control of piezoelectric ceramics, the hysteresis characteristics of piezoelectric ceramics need to be analyzed and controlled.

[0005] Compared with the existing modeling methods for the hysteresis phenomenon of piezoelectric ceramics, such as Preisach hysteresis, Prandtl-Ishlinskii (P-I) hysteresis, Duhem hysteresis, and polynomial hysteresis, the Preisach model has difficulty in parameter identification and inverse model solving, the P-I model has difficulty in calculation, and the Duhem model has difficulty in modeling and parameter identification. Compared with the above-mentioned models, the polynomial hysteresis model has the advantages of small calculation amount, simple modeling, and easy inverse solving, but the existing polynomial model has the disadvantage of large calculation amount in high-precision fitting. SUMMARY

[0006] To solve the above technical problems, the application provides a phase control method and device suitable for a nulling interference system, improves the hysteresis fitting accuracy, simplifies the operation amount, improves the phase control accuracy and makes the phase controllable.

[0007] A phase control method suitable for a nulling interference system, the method comprising the following steps:

[0008] Step S1: sequentially communicate and connect a PC end, a controller, a piezoelectric amplifier, a piezoelectric actuator and a phase adjustment mirror, sequentially communicate and connect a capacitive displacement sensor attached to the phase adjustment mirror and a sensor controller and the PC end, and constitute a phase control device of the nulling interference system;

[0009] Step S2: under the open loop condition of the phase control device, the PC end sends an instruction, outputs a high-voltage signal through the controller and the piezoelectric amplifier, controls the piezoelectric actuator to generate displacement, and the capacitive displacement sensor and the sensor controller transmit the measured displacement change to the PC end, record the displacement change, and obtain mapping data including the input voltage and the output displacement of the piezoelectric actuator;

[0010] Step S3: according to the obtained mapping data, perform initial third-order polynomial fitting, determine voltage segmentation points according to the fitting error data change and the motion stroke of the system, and use a piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm to fit each curve and model the piezoelectric ceramic hysteresis nonlinear curve;

[0011] Step S4: according to the established piezoelectric ceramic hysteresis nonlinear curve model, based on a composite control algorithm composed of feedforward control and PID control, control the output displacement of the established piezoelectric ceramic hysteresis nonlinear curve model, and obtain the error range of each device of the phase control device;

[0012] Step S5: under the closed loop condition of the phase control device, based on the error range of each device, send an instruction from the PC end to control the phase of the nulling interference system.

[0013] Further, the step S3 of modeling the piezoelectric ceramic hysteresis nonlinear curve comprises:

[0014] Step S31: according to the mapping data obtained in step S2, use a third-order polynomial expression to perform initial fitting on the hysteresis rising curve and the hysteresis falling curve respectively;

[0015] Step S32: under the same voltage, the displacement data in the obtained mapping data is calculated to obtain the difference between the displacement obtained by the initial fitting of the third-order polynomial, according to the size of the displacement difference corresponding to each voltage point and the change of the displacement difference of the two sampling points before and after the voltage point, the preselected voltage segmentation point is found out, and the final voltage segmentation point is determined according to the system motion stroke, and the final voltage segmentation point satisfies: at least one curve in the two curves before or after the final voltage segmentation point has a fitting error greater than a preset threshold;

[0016] Step S33: according to the final voltage segmentation point, the hysteresis nonlinear curve is divided into the final voltage segmentation point plus two segments of curves, and the piecewise self-matching polynomial fitting algorithm is used to perform first-order to eighth-order polynomial fitting on each segment of curve, and in the self-matching fitting process, the polynomial fitting highest term and polynomial expression of each segment of curve are self-matched according to the fitting tolerance range of the system as the criterion;

[0017] Step S34: based on the obtained polynomial expression of each segment of curve, a piezoelectric ceramic hysteresis nonlinear curve model is established.

[0018] Further, the step S4 comprises:

[0019] 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, the input displacement-output voltage data are used to obtain a feedforward control expression by using the piecewise self-matching polynomial fitting algorithm;

[0020] Step S42: the difference between the expected output value of the PC end and the feedback signal of the sensor controller is used as the input value of the PID algorithm, and a PID control is established;

[0021] Step S43: the composite control algorithm established by steps S41 and S42 is used to set the PID control parameters of the phase regulation device based on the errors of various devices of the system and external disturbances, and the output displacement of the system is controlled.

[0022] On the other hand, the application also provides a phase regulation device suitable for a zero cancellation interference system, the device comprising a PC end, a controller, a piezoelectric amplifier, a piezoelectric actuator, a phase adjustment mirror, a capacitive displacement sensor, a sensor controller and a zero cancellation interference system,

[0023] The PC end sends an instruction under the open-loop condition of the phase regulation device, outputs a high-voltage signal 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;

[0024] According to the obtained mapping data, initial third-order polynomial fitting is carried out, voltage segmentation points are determined according to error data changes of the fitting and a motion stroke of the system, each curve is fitted by using a piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm, and the piezoelectric ceramic hysteresis nonlinear curve is modeled;

[0025] According to the established piezoelectric ceramic hysteresis nonlinear curve model, the output displacement of the piezoelectric ceramic hysteresis nonlinear curve model is controlled based on a composite control algorithm composed of feedforward control and PID control, and error ranges of each device of the phase control device are obtained.

[0026] Under the closed loop condition of the phase control device, the PC end sends instructions again based on the error ranges of each device, and the phase of the null interference system is controlled.

[0027] The present application has the following advantages:

[0028] In the present application, a piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm is used, after the piezoelectric ceramic hysteresis curve is segmented, a polynomial expression of each curve is self-matched, the fitting precision is improved, the operation amount is simplified, and the phase control precision of the null interference system is improved. BRIEF DESCRIPTION OF DRAWINGS

[0029] Fig. 1 is a flow chart of a phase control method suitable for a null interference system according to the present application;

[0030] Fig. 2 is a schematic diagram of a phase control device suitable for a null interference system according to the present application;

[0031] Fig. 3 is a signal trend diagram of a phase control device suitable for a null interference system according to the present application;

[0032] Fig. 4 is a flow chart of a piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm according to the present application;

[0033] Fig. 5 is an effect diagram of a third-order polynomial initial fitting hysteresis nonlinear curve according to the present application;

[0034] Fig. 6 is an effect diagram of a piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm according to the present application;

[0035] Fig. 7 is a principle diagram of a phase control method suitable for a null interference system according to the present application;

[0036] Fig. 8 is a phase control precision simulation result diagram based on the method according to the present application.

[0037] Reference signs:

[0038] 1. PC terminal; 2. Controller; 3. Piezoelectric amplifier; 4. Piezoelectric actuator; 5. Capacitive displacement sensor; 6. Sensor controller; 7. Zero interference cancellation system; 71. Phase adjustment reflector; 72. Reflector; 73. Beam combiner; 74. Fixed corner cube prism; 75. Telescope. DETAILED DESCRIPTION

[0039] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] The present invention proposes a phase control method and device suitable for a nulling interference system, which is used to adjust the phase of the nulling interference system from 0 to 2π. The required motion range of 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.

[0041] like Figure 1 The flow chart of a phase control method suitable for a zero-cancellation interference system is shown in FIG. Figure 2 The diagram shows a phase control device suitable for a nulling interferometer system. The device utilizes 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 mirror 71 to control the phase of the nulling interferometer system 7. The nulling interferometer system 7 includes a phase adjustment mirror 71, a reflector 72, a beam combiner 73, a fixed corner cube 74, and a telescope 75. The nulling interferometer system is composed of two telescopes 75 and operates according to the Bracewell nulling interferometer principle. In the entire device, the PC terminal 1 is connected to the controller 2, which is connected to the piezoelectric amplifier 3, which is connected to the piezoelectric actuator 4. The phase adjustment mirror 71 should maintain consistent displacement with the piezoelectric actuator 4. The capacitive displacement sensor 5 attached to the phase adjustment mirror 71 is connected to the sensor controller 6, which is connected to the PC terminal 1. Without loss of generality, the device can perform the steps involved in the following phase control method suitable for a nulling interferometer system.

[0042] The signal trend of the phase control device of the zero-cancelling interference system is shown in the figure below. Figure 3As 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, and the controller 2 outputs the corresponding low-voltage control signal to the piezoelectric amplifier 3 after the algorithm calculation, and the piezoelectric amplifier 3 transmits the high-voltage signal to the piezoelectric actuator 4, which is driven to produce a slight deformation. The slight deformation of the piezoelectric actuator 4 drives the phase adjustment mirror 71 to move slightly, thereby changing the optical delay line of the null interference system and playing a role in phase adjustment. The movement of the phase adjustment mirror 71 changes the displacement signal received by the capacitive displacement sensor 5, and the sensor controller 6 receives the displacement signal from the capacitive displacement sensor 5 and feeds it back to the PC terminal 1, realizing closed-loop control of the entire system.

[0043] In particular, referring again to Figure 1 A phase adjustment method suitable for a null interference system includes the following steps:

[0044] Step S1: Connect each device according to the circuit to form a phase adjustment device of a null interference system.

[0045] Step S2: Under the condition of system open loop, the PC terminal 1 sends instructions, the piezoelectric actuator 4 generates corresponding displacement, and 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.

[0046] Step S3: Perform initial third-order polynomial fitting according to the obtained mapping data, determine the voltage segmentation point according to the fitting error data change and the motion stroke of the system, and use the piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm to fit each curve and model the piezoelectric ceramic hysteresis nonlinear curve.

[0047] Step S4: According to the established piezoelectric ceramic hysteresis nonlinear curve model, based on the composite control algorithm composed of feedforward control and PID control, control the output displacement of the established piezoelectric ceramic hysteresis nonlinear curve model, and obtain the error range of each device of the phase adjustment device.

[0048] Step S5: Under the condition of closed loop of the phase adjustment device, based on the established piezoelectric ceramic hysteresis nonlinear curve model and the composite control algorithm, and the error range of each device, send instructions from the PC terminal to adjust the phase of the null interference system.

[0049] In the implementation of phase control, firstly, the piezoelectric ceramic hysteresis nonlinear curve is modeled, then the simulation of system phase control is carried out, and whether the control algorithm and the selection of each device meet the system requirements is judged according to the simulation results. The piezoelectric ceramic hysteresis nonlinear curve is modeled by using a piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm, and the flow chart of modeling is shown in Figure 4 The specific steps are as follows:

[0050] Step S31: Under the open loop condition of the system, the input and output data of the piezoelectric ceramic rising hysteresis curve and the falling hysteresis curve are collected, such as the rising hysteresis sampling point curve and the falling hysteresis sampling point curve in Figure 5 According to the collected data, the rising hysteresis curve and the falling hysteresis curve are initially fitted by using a third-order polynomial expression (for example, least square fitting), such as the third-order fitting curve of the rising process and the third-order fitting curve of the falling process in Figure 5

[0051] Step S32: Under the same voltage, the difference between the hysteresis sampling point displacement and the third-order fitting displacement is calculated, according to the size of the displacement difference corresponding to each voltage point and the change of the displacement difference of the two sampling points before and after the voltage point, the preselected voltage segmentation point is found out, and finally the voltage segmentation point is determined according to the system movement stroke. The final voltage segmentation point meets the following conditions: at least one curve in the two curves before or after the final voltage segmentation point has a large fitting error, that is, the fitting effect is poor, that is, it exceeds the preset threshold. The fitting tolerance curve of the system is shown in Figure 5 The tolerance range curve of fitting 2 nanometers is shown in

[0052] Step S33: According to the selected final voltage segmentation point, the hysteresis sampling point curve is divided into the final voltage segmentation point plus two segments of curves, and each segment of curve is fitted by using the piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm proposed in the present application, that is, the first-order, up to the eighth-order (j≤8) polynomial fitting is carried out, and n=j is taken as the highest order of polynomial fitting. The polynomial fitting expression is as follows: y i =a1U i n + a2U i n-1 +…+ a n+1 , wherein i=1…N, N is the number of hysteresis sampling points of the fitting segment at this moment after the hysteresis sampling point curve is segmented, U i is the voltage data corresponding to the hysteresis sampling point, and y i is the displacement value of the polynomial fitting.

[0053] In the self-matching fitting process, the maximum fitting error required by the system is taken as the criterion, that is, Figure 5 ​the tolerance range of 2 nanometers, the maximum error C of each order fitting is obtained j If C j ≤ the maximum fitting error required by the system, then j is the highest order 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 polynomial fitting of the first to eighth order cannot meet the demand of the maximum fitting error required by the system, at this time, the segmentation point is reselected or the segmentation point is increased, and then the piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm is used to self-match the polynomial fitting highest order and the polynomial expression of each segment curve.

[0054] Step S34: According to step S33, the polynomial expression of each segment curve is obtained, the piezoelectric ceramic hysteresis nonlinear curve model is established, and the fitting effect of the piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm is shown in FIG. 6.

[0055] Figure 5 The initial third-order polynomial expression is as follows:

[0056] The rising stage is y = -1.7488 10 -6 U 3 + 2.7458 10 -4 U 2 + 0.0654U - 0.0471

[0057] The falling stage is y = 2.4510 10 -7 U 3 - 3.3103 10 -4 U 2 + 0.1104U + 0.1478; wherein U is the hysteresis sampling point voltage, and y is the displacement value of the third-order polynomial fitting.

[0058] As can be seen from FIG. 5, between the motion stroke 0~3μm, many fitting errors in the third order polynomial initial fitting are greater than 2nm. 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 descending hysteresis sampling point curve. According to the motion stroke, 45V is further selected 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 descending hysteresis sampling point curve is greater than 3μm. Since in the piezoelectric ceramic rising hysteresis sampling point curve, the stroke corresponding to 45V voltage contains the stroke corresponding to 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 descending hysteresis sampling point curve. The maximum error between the fitting of the rising hysteresis sampling point curve 0~45V and the descending hysteresis sampling point curve 30~0V is 2nm, and the maximum error between the fitting of the rising hysteresis sampling point curve 45~150V and the descending hysteresis sampling point curve 150~30V is 30nm. The piezoelectric ceramic hysteresis nonlinear curve is fitted by using the segmented self-matching polynomial fitting algorithm, and the schematic diagram of the fitting is shown in FIG. 6. The fitting error is within 2nm in the displacement 0~3μm, and the expression obtained by fitting 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 hysteresis sampling point voltage, and y1 is the displacement value fitted by using the piezoelectric ceramic hysteresis nonlinear curve segmented self-matching polynomial fitting algorithm.

[0059] From the above, piezoelectric ceramic hysteresis nonlinear curve piecewise self-matching polynomial fitting algorithm improves the modeling accuracy of the system in the motion stroke, and the operation amount is simplified.

[0060] Then, the piezoelectric ceramic hysteresis nonlinear curve model is controlled by using the composite control algorithm.

[0061] The feedforward control is to exchange the input and output data collected by experiment, and then use the piezoelectric ceramic hysteresis nonlinear curve piecewise self-matching polynomial fitting algorithm to fit and establish the inverse model, wherein the maximum error of the voltage fitting in the rising stage is 0.2V. Since the voltage fitting in the falling stage cannot be less than 0.2V in the fitting of the first-order to eighth-order polynomial, the falling hysteresis sampling point curve is segmented to make the maximum error of the voltage fitting in the falling stage 3.174~0.183μm be 0.01V, and the maximum error of the voltage fitting in the falling stage 10.102~3.174μm be 0.3V. The expression of the inverse model is: the 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; the falling stage 3.174~0.183μm (including 3.174μm): U n =0.0670x 3 -0.2690x 2 +10.2168x-1.8611; the falling stage 10.102~3.174μm:

[0062] U n =0.0029x 6 -0.1155x 5 +1.8629x 4 -15.6352x 3 +72.2248x 2 -162.3499x+162.7711. Wherein, x is the hysteresis sampling point displacement, U n is the voltage obtained by using the inverse model expression. The expression of the PID control used is: U(k)=K p e(k)+K d [e(k)-e(k-1)]+K i ∑e(k), where e(k) is the deviation at this moment, e(k-1) is the deviation at the last moment, are the proportional, integral and differential coefficients, ∑e(k) is the accumulated error, and U(k) is the output voltage of the PID control algorithm at this moment.

[0063] The schematic diagram of the phase control method is shown in FIG. 7, and the specific steps are as follows:

[0064] In step S41, the expected displacement is converted into 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. The displacement x(k) at the current moment is compared with the displacement x(k-1) at the previous moment to determine whether it is in an ascending state or a descending state;

[0065] According to the ascending or descending state and the displacement segmentation point discriminant, different expressions are entered. That is, in the ascending phase, x enters the ascending phase expression:

[0066] -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 phase, if x(k)≤x2(x2=3.174μm), x enters the descending 3.174~0.183μm phase expression: 0.0670x 3 -0.2690x 2 +10.2168x-1.8611, otherwise x enters the descending 10.102~3.174μm phase expression: 0.0029x 6 -0.1155x 5 +1.8629x 4 -15.6352x 3 +72.2248x 2 -162.3499x+162.7711, the obtained output value and the voltage adjusted by the PID are combined and divided by k, k=30, which is equal to the amplification factor K of the piezoelectric amplifier, to output a low-voltage signal U1, Figure 7 where a1, a2, d2, c1, etc. represent the letters of the coefficients, which are consistent with the coefficients in the above expressions;

[0067] After being amplified by the piezoelectric amplifier with an amplification factor of , the high-voltage amplified signal U2=KU1 is output, where K=30.

[0068] Since the piezoelectric ceramic actuator itself is a capacitive material, it is generally regarded as a capacitor in the whole circuit, and the whole driving circuit can be regarded as a circuit. Therefore, from the formula U m = (1 - e -t / （RC） )U2, the driving voltage U m applied to the piezoelectric ceramic is obtained, 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 e -t / （RC） quickly decays to 0 as time increases, so after a short time, U m = U2.

[0069] According to the discriminant of the rising or falling state and the voltage segmentation point, and the segmented polynomial expression of the fitting piezoelectric ceramic hysteresis nonlinear curve obtained above, the input voltage U m enters 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 falling 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, to obtain the corresponding output displacement , Figure 7 q1, p2, g2, w1, etc. in the expression represent the same coefficients as in the above expression;

[0070] Step S42, the output displacement is fed back to the system by the sensor controller 6, the difference between the expected displacement and the output displacement is taken as the input of the PID control algorithm, the whole system forms a closed loop feedback system, the error of the system, the disturbance of the outside world and other interference factors affecting the stability of the system are suppressed, in the flow chart, m, n, f, v, l are the possible errors of each part of the device.

[0071] Step S43, the parameters of the PID are K p =4, K i =6, K d =0, the errors of each part of the system device 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 and C=3.1μF respectively, and the amplification factor K of the piezoelectric amplifier is 30.

[0072] The phase 0~2π of the zero cancellation interference system is controlled, that is, the displacement 0~3μm is moved, and the phase control precision simulation diagram of the system is as shown in Figure 8 When the system displacement realizes the rising and falling movement of 0~3μm, ┼ represents the expected output displacement, • represents the simulation output displacement, and the two curves represent the tolerance range of the system control precision, which can be seen from Figure 8 It can be seen that the simulation output displacement is almost within the tolerance range of the system control precision.

[0073] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above is only a specific embodiment of the present application and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A phase control method applicable to a nulling interference system, characterized in that: The method comprises the following steps: Step S1: Connecting the PC, controller, piezoelectric amplifier, piezoelectric actuator, and phase adjustment mirror in sequence, and connecting the capacitive displacement sensor attached to the phase adjustment mirror to the sensor controller and PC in sequence to form a phase control device for the nulling interference system; Step S2: Under the open-loop condition of the phase control device, the PC sends a command, which outputs a high-voltage signal after passing through the controller and piezoelectric amplifier to control the piezoelectric actuator to generate displacement. The capacitive displacement sensor and 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 based on the change in the fitted error data and the motion stroke of the system, and fitting each segment of the piezoelectric ceramic hysteresis nonlinear curve using a segmented self-matching polynomial fitting algorithm to model 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 error range of each component, the PC sends instructions to control the phase of the zero-cancellation interference system.

2. A phase control method for a nulling interference system according to claim 1, characterized in that: 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 based on 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 based on the size of the displacement difference corresponding to each voltage point and the change in the displacement difference between the two sampling points before and after the voltage point. Then, determine the final voltage segmentation point based on the system motion range. The final voltage segmentation point satisfies the following conditions: the fitting error of at least one curve in the two curve segments before or after the final voltage segmentation point is greater than a preset threshold. Step S33: Based on the final voltage segmentation point, the hysteresis nonlinear curve is divided into two segments, the number of which is equal to the final voltage segmentation point plus two segments. A piecewise self-matching polynomial fitting algorithm is used to perform polynomial fitting of first order and up to eighth order on each segment. During the self-matching fitting process, the highest polynomial fitting term and polynomial expression of each segment are self-matched based on the fitting tolerance range of the system. Step S34: establishing a piezoelectric ceramic hysteresis nonlinear curve model based on the obtained polynomial expression of each curve segment.

3. The phase control method for a nulling interference system according to claim 1, wherein: The step S4 comprises: Step S41: Based on the piezoelectric ceramic hysteresis nonlinear curve model established in step S3, the input voltage and output displacement data are inverted, that is, a feedforward control expression is obtained based on the input displacement-output voltage data using a piecewise self-matching polynomial fitting algorithm; Step S42: Using 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 mirror, a capacitive displacement sensor, a sensor controller and a null interference cancellation system; The PC sends a command under the open-loop condition of the phase control device, 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 changes in the fitted error data and the system's motion range. The piezoelectric ceramic hysteresis nonlinear curve segmentation self-matching polynomial fitting algorithm is used to fit each curve segment and 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.

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