CN114253139B - Nano-positioning platform control system based on switching structure - Google Patents
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Abstract
The invention discloses a nano positioning platform control system based on a switching structure, which belongs to the field of precise positioning control and comprises the following components: the first rectification switcher is used for rectifying a non-smooth input signal input into the system into a smooth input signal and outputting the smooth input signal; the second rectification switcher is used for rectifying the non-smooth output signal of the controlled nano positioning platform into a smooth feedback signal and negatively feeding back the smooth feedback signal to the first adder; the first adder is used for subtracting the smooth input signal from the smooth feedback signal to obtain a first difference signal and outputting the first difference signal; the first integrator is used for carrying out integration processing on the first difference signal to obtain a first integrated signal and outputting the first integrated signal; an inversion switch for inverting the first integrated signal into a non-smooth integrated signal and outputting the non-smooth integrated signal; and the control unit is used for generating a corresponding control signal according to the non-smooth integral signal so as to control the controlled nano positioning platform. The system control bandwidth is increased, so that the positioning platform realizes higher signal tracking frequency.
Description
Technical Field
The invention belongs to the field of precise positioning control, and particularly relates to a nano positioning platform control system based on a switching structure.
Background
Nanotechnology is widely used in various engineering and scientific fields, for example, in precision equipment such as ultra-precision machine tool processing, nanomanipulators, data storage devices, and the like, and plays an indispensable important role. The atomic force microscope (Atomic Force Microscope, AFM) is a high-speed and high-precision measuring instrument, which is an important part in high-end precision manufacturing, the precision and the performance of the high-speed and high-precision measuring instrument depend on the precision and the performance of a nanometer positioning platform to a great extent, and the research of the high-precision nanometer positioning platform has extremely important significance for the research and the development of the high-precision measuring instrument.
The precision and imaging quality of AFM are directly related to the scanning speed of its scanner, which is the two-dimensional nano positioning platform. In recent years, the rapid development of nanotechnology has increasingly demanded AFM imaging speed, for example, dynamic behavior of some biomacromolecules and dynamic scenes of chemical reaction progress, which are usually in millisecond order, and high-speed AFM imaging is required to capture the images. However, the scanning frequency of the AFM is usually less than 20-30Hz, so that the sample imaging usually takes tens of seconds, and the requirement of dynamic images cannot be met. In the high-speed signal tracking process of the nanometer positioning platform, nonlinear phenomena represented by hysteresis, vibration and creep are more obvious, meanwhile, the influence of sensor noise on control precision is more and more large, and the problem of tip vibration of signals greatly weakens the imaging quality of AFM, which are difficult problems for realizing high-speed nanometer positioning control. How to enable the nano positioning platform to achieve higher signal tracking frequency and stronger sensor noise immunity has important theoretical significance and engineering practical value.
Disclosure of Invention
Aiming at the defects and improvement demands of the prior art, the invention provides a nano positioning platform control system based on a switching structure, which aims to increase the control bandwidth of the system by utilizing the controllability of a low-frequency smooth signal, so that the positioning platform realizes higher signal tracking frequency and has stronger sensor noise resistance.
In order to achieve the above object, the present invention provides a nano positioning platform control system based on a switching structure, including: the first rectification switcher is used for rectifying a non-smooth input signal input into the system into a smooth input signal and outputting the smooth input signal; the input end of the second rectification switcher is connected with the output end of the controlled nano positioning platform and is used for rectifying a non-smooth output signal of the controlled nano positioning platform into a smooth feedback signal and negatively feeding back the smooth feedback signal to the first adder; the first adder is used for subtracting the smooth input signal from the smooth feedback signal to obtain a first difference signal and outputting the first difference signal; the first integrator is used for carrying out integration processing on the first difference signal to obtain a first integrated signal and outputting the first integrated signal; an inversion switch for inverting the first integrated signal into a non-smooth integrated signal and outputting the non-smooth integrated signal; and the control unit is used for generating a corresponding control signal according to the non-smooth integral signal and controlling the controlled nano positioning platform by utilizing the control signal.
Still further, the control unit includes: the input end of the self-adaptive filter is connected with the output end of the controlled nano positioning platform and is used for carrying out self-adaptive filtering on a non-smooth output signal of the controlled nano positioning platform and then negatively feeding back to the second adder; the second adder is used for subtracting the non-smooth integral signal from the signal output by the adaptive filter to obtain a second difference signal and outputting the second difference signal; the second integrator is used for carrying out integration processing on the second difference signal to obtain a second integrated signal and outputting the second integrated signal; and the control subunit is used for generating the control signal according to the second integral signal and controlling the controlled nano positioning platform by utilizing the control signal.
Still further, the control subunit includes: the input end of the damping compensator is connected with a driver of the controlled nano positioning platform and is used for carrying out damping compensation on the resonance wave crest of the controlled nano positioning platform and then negatively feeding back to the third adder; the third adder is used for subtracting the second integrated signal from the signal output by the damping compensator to obtain a third difference signal and outputting the third difference signal; and the hysteresis eliminator is used for generating the control signal according to the third difference signal by utilizing a nonlinear hysteresis inverse model and controlling the controlled nanometer positioning platform by utilizing the control signal.
Furthermore, the first integrator, the inversion switcher and the control unit form a primary control structure, the control unit is a secondary control structure embedded in the primary control structure, the control subunit is a tertiary control structure embedded in the secondary control structure, and parameters of each stage of control structure are sequentially determined from inside to outside.
Further, the first integrator is a second-order integrator or more, and the second integrator is a first-order integrator.
Furthermore, the adaptive filter is configured to perform fast fourier transform on the non-smooth output signal to obtain a noise spectrogram, adaptively select one or more filtering modes according to noise distribution in the noise spectrogram, and set corresponding weights for each filtering mode to perform adaptive filtering.
Further, the system uses the damping compensator to change the zero pole of the transfer function of the controlled nano-positioning platform, and reduces the order of the transfer function of the controlled nano-positioning platform so as to reduce the open-loop first resonant frequency of the controlled nano-positioning platform and realize damping-reducing compensation.
Further, the hysteresis eliminator constructs the nonlinear hysteresis inverse model through a linear operator superposition mode.
Further, the rectification modes of the first rectification switch and the second rectification switch are as follows:
y′＝(-1)(i-1)r(t)+2[i/2]A
the inversion mode of the inversion switcher is as follows:
y＝(-1)(i-1)r(t)+2(-1)i[i/2]A
Wherein y' is a rectified signal, r (t) is a signal before rectification, i is system time, A is the amplitude of r (t), y is an inverted signal, and the frequencies of y and r (t) are the same.
In general, through the above technical solutions conceived by the present invention, the following beneficial effects can be obtained:
(1) The rectification switcher is designed in the nano positioning platform control system based on the switching structure, the high-frequency irregular signal is converted into the low-frequency regular signal and then is sent to the first-stage integral controller, the signal after the first-stage control is inverted into the high-frequency non-smooth signal to carry out the second-stage control, and the real signal control is completed, so that the controller is prevented from directly tracking the bandwidth of the high-frequency signal, and the bandwidth of the system and the tracking performance of the high-frequency irregular signal are improved;
(2) The decoupling of system tuning is realized by adopting a multi-stage nested closed-loop feedback control structure from outside to inside, the control effects of noise resistance, bandwidth increase, nonlinearity elimination and the like are designed separately layer by layer, dynamic and static compensation separation is realized, a static compensation unit utilizing open-loop data mainly acts on a three-stage control structure, a dynamic compensation unit for signal real-time tracking mainly acts on a primary control structure and a secondary control structure, and the two control structures are successfully separated; finally, the system can solve the problem of high-frequency and high-noise signal tracking, complete the high-speed and accurate tracking of the two-dimensional nanometer positioning platform, and can be used for influencing the design of an atomic force microscope.
Drawings
FIG. 1 is a block diagram of a nano-positioning platform control system based on a switching structure according to an embodiment of the present invention;
fig. 2 is a design flow chart of a nano positioning platform control system based on a switching structure according to an embodiment of the present invention.
Fig. 3 is an effect diagram of the control of the nano positioning platform control system based on the switching structure according to the embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
In the present invention, the terms "first," "second," and the like in the description and in the drawings, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.
Fig. 1 is a block diagram of a nano positioning platform control system based on a switching structure according to an embodiment of the present invention. Referring to fig. 1, the nano-positioning platform control system based on the switching structure includes a first rectifying switch, a second rectifying switch, a first adder, a first integrator, an inversion switch and a control unit.
The input end of the first rectifying switch is a system input end, and the output end of the first rectifying switch is connected with one input end of the first adder. The input end of the second rectification switcher is connected with the output end of the controlled nanometer positioning platform, and the output end of the second rectification switcher is connected with the other input end of the first adder in a negative feedback way. The output end of the first adder is connected with the input end of the first integrator, the output end of the first integrator is connected with the input end of the inversion switch, the output end of the inversion switch is connected with the input end of the control unit, and the output end of the control unit is connected with the controlled nanometer positioning platform.
The first rectifying switch is used for rectifying a non-smooth input signal input into the system into a smooth input signal and outputting the smooth input signal to the first adder. The second rectification switcher is used for rectifying the non-smooth output signal of the controlled nano positioning platform into a smooth feedback signal and negatively feeding back the smooth feedback signal to the first adder. The first adder is used for subtracting the smooth input signal from the smooth feedback signal to obtain a first difference signal and outputting the first difference signal to the first integrator. The first integrator is used for performing integration processing on the first difference signal to obtain a first integrated signal and outputting the first integrated signal to the inversion switcher. The inversion switch is used for inverting the first integrated signal into a non-smooth integrated signal and outputting the non-smooth integrated signal to the control unit. The control unit is used for generating a corresponding control signal according to the non-smooth integral signal and controlling the controlled nano positioning platform by utilizing the control signal.
The rectification switcher and the inversion switcher realize the conversion of input and output signals by switching signals at specific sampling nodes, and the specific mathematical expression of the switching mode is related to the input signal form and the scanning mode of the controlled nanometer positioning platform. The rectification switches and the inversion switches should have consistency, and in each real-time control, the mathematical expression of the switching of each rectification switch is the same, and the inversion switches keep the inverse mathematical expression of the switching of the rectification switches.
A smooth signal refers to a signal that is temporally infinitely conductive within a defined domain. A non-smooth signal refers to a signal that has sharp points within a defined domain and is not infinitely conductive. The non-smooth input signal and the non-smooth output signal are both high-frequency signals, and the smooth input signal and the smooth feedback signal are both low-frequency signals.
According to an embodiment of the invention, the control unit comprises an adaptive filter, a second adder, a second integrator and a control subunit.
One input end of the second adder is an input end of the control unit and is connected with the output end of the inversion switch. The input end of the self-adaptive filter is connected with the output end of the controlled nanometer positioning platform, and the output end of the self-adaptive filter is connected with the other input end of the second adder in a negative feedback way. The output end of the second adder is connected with the input end of the second integrator, the output end of the second integrator is connected with the control subunit, and the output end of the control subunit is the output end of the control unit.
The self-adaptive filter is used for carrying out self-adaptive filtering on the non-smooth output signal of the controlled nano positioning platform and then feeding the non-smooth output signal back to the second adder. The second adder is used for subtracting the non-smooth integral signal from the signal output by the adaptive filter to obtain a second difference signal and outputting the second difference signal to the second integrator. The second integrator is used for performing integration processing on the second difference signal to obtain a second integrated signal and outputting the second integrated signal to the control subunit. The control subunit is used for generating the control signal according to the second integral signal and controlling the controlled nano positioning platform by utilizing the control signal.
According to an embodiment of the invention, the control subunit comprises a damping compensator, a third adder and a hysteresis canceller.
An input end of the third adder is an input end of the control subunit and is connected with an output end of the second integrator. The input end of the damping compensator is connected with a driver of the controlled nanometer positioning platform, and the output end of the damping compensator is connected with the other input end of the third adder in a negative feedback way. The output end of the third adder is connected with the input end of the hysteresis eliminator, and the output end of the hysteresis eliminator is the output end of the control subunit.
The damping compensator is used for carrying out damping compensation on the resonance wave crest of the controlled nano positioning platform and then negatively feeding back to the third adder. The third adder is used for subtracting the second integrated signal from the signal output by the damping compensator to obtain a third difference signal and outputting the third difference signal to the hysteresis eliminator. The hysteresis eliminator is used for generating the control signal according to the third difference signal by utilizing the nonlinear hysteresis inverse model and controlling the controlled nanometer positioning platform by utilizing the control signal.
The self-adaptive filter is used for carrying out fast Fourier transform on the non-smooth output signal to obtain a noise spectrogram, adaptively selecting one or more filtering modes according to noise distribution in the noise spectrogram, and setting corresponding weights for the filtering modes so as to carry out self-adaptive filtering. The filtering modes are low-pass filtering, high-pass filtering, mean filtering, gaussian filtering and the like, the weight proportion of each filtering mode is adaptively selected, and each sensor data is truly recorded while the signal authenticity is not affected.
The system changes the zero pole of the transfer function of the controlled nano positioning platform by using the damping compensator, reduces the order of the transfer function of the controlled nano positioning platform, reduces the open-loop first resonant frequency of the controlled nano positioning platform, realizes damping reduction compensation, and improves the bandwidth performance of the system.
The open loop first resonant frequency refers to the frequency corresponding to the first peak in the open loop frequency response plot. For the nano positioning platform, the control bandwidth is directly determined by the open loop first resonant frequency, and under the condition that no compensation is adopted, 10% of the open loop first resonant frequency is the upper limit of the control bandwidth of the system, and the open loop frequency curve of the system can be identified by the input and output results under the open loop. In this embodiment, a linear damping compensator is added to the feedback branch to change the pole-zero of the three-stage control structure, and a system pole-zero with reasonable design is allocated according to two indexes of stability and rapidity to achieve the goal.
The hysteresis eliminator builds the nonlinear hysteresis inverse model in a linear operator superposition mode and serves as a feedforward input to counteract the high-frequency hysteresis nonlinear part. The hysteresis eliminator is designed to counteract hysteresis nonlinearity of the nano positioning platform under the high-frequency input signal. The hysteresis nonlinearity is in a hysteresis loop shape, that is, the same input may correspond to different output at different time points, and the hysteresis canceller adopts an inverse cancellation mode to cancel each other by constructing an inverse hysteresis loop. Specifically, a hysteresis model is constructed by adopting a data driving mode of linear operator accumulation, and the inverse hysteresis parameters are obtained by identifying the hysteresis parameters under an open loop model and utilizing an inverse analysis mode.
The nano positioning platform control system based on the switching structure can control the platform to move in two coordinate axis directions in a two-dimensional plane. The hysteresis eliminator adopts Prandtl-ISHLINSKII linear operator model modeling, and then establishes a hysteresis inverse model according to an analytical inverse mode, so as to eliminate hysteresis nonlinearity in the high-speed positioning process of the nanometer positioning platform, and the controller can be designed in a linear mode. The damping compensator adopts a second-order linear system compensation mode, so that the bandwidth of the system is increased. The formed three-stage control structure is mainly used for carrying out static compensation on the model, and the difficulty of dynamic control after the static compensation is reduced.
The first integrator, the inversion switcher and the control unit form a primary control structure; the control unit is a secondary control structure embedded in the primary control structure. In the primary control structure, a first integrator and an inversion switch are connected with the secondary control structure in series; in the secondary control structure, a second integrator is connected with the tertiary control structure in series, and a self-adaptive filter is arranged on a feedback loop.
The non-smooth input signal is transmitted from outside to inside from the primary control structure to the secondary control structure and then to the tertiary control structure. The primary control structure is mainly used for increasing the bandwidth of the system and completing the rapid and accurate tracking of the high-frequency signals. The control subunit is a three-level control structure embedded in the two-level control structure, the parameters of each level control structure are sequentially determined from inside to outside, namely, each controller parameter in the three-level control structure is determined firstly, each controller parameter in the two-level control structure is determined, and each controller parameter in the one-level control structure is determined finally.
The first integrator is a second-order integrator or more, and the second integrator is a first-order integrator. The first integrator is used to track a simple signal of low frequency or direct current due to the action of the rectifying switch, and is designed as a high-order integrator for eliminating tracking errors. The second integrator is used for increasing the robustness of the system to noise and external interference, and the second integrator for processing high-frequency noise and external interference is designed to be a low-order integrator, so that the gain of the noise relative to the final output is reduced to a very low bandwidth and the second integrator acts as a dynamic filtering unit. The secondary control structure is mainly used for filtering the sensor and increasing the robustness of the system to external disturbance and sensor noise in the actual environment.
In this embodiment, the controlled nano-positioning platform works in a mode of matching a fast axis with a slow axis and scanning line by line, and the reference input signal of the fast axis is a triangular wave signal with a frequency of 100Hz and an amplitude of 1 μm, for example. The first rectification switcher performs signal switching at the tip of the triangular wave to convert the triangular wave signal into a ramp wave signal, the rectification process of the second rectification switcher is the same, the difference value between the ramp wave signal and the smooth feedback signal is input into the first integrator, and at the moment, the first integrator only needs to track the ramp wave signal without tip jitter, so that the requirement on the bandwidth of a controller is greatly reduced. The inversion switcher switches the ramp wave signal output by the first integrator once every 0.005s, changes the output ramp wave signal into a triangular wave signal with the frequency of 100Hz again, and inputs the triangular wave signal into the secondary control structure to complete the control of the real triangular wave signal. In this example, the rectification modes of the first rectification switch and the second rectification switch are:
y′＝(-1)(i-1)r(t)+2[i/2]A
the inversion mode of the inversion switcher is as follows:
y＝(-1)(i-1)r(t)+2(-1)i[i/2]A
Wherein y' is a rectified signal, r (t) is a signal before rectification, i is system time, A is the amplitude of r (t), y is an inverted signal, and the frequencies of y and r (t) are the same.
It is understood that the first rectifying switch and the second rectifying switch may also adopt other rectifying modes, and the inversion switch may adopt corresponding inversion modes.
In the nano positioning platform control system based on the switching structure, the tracking performance of the system on the high-frequency irregular signals is improved through a plurality of rectification switches and inversion switches; the decoupling of system tuning parameters is realized through the multi-stage closed-loop feedback control structure from outside to inside; noise disturbance and high-frequency nonlinearity can be effectively processed through a damping compensator, a hysteresis eliminator and a self-adaptive filter; finally, the system can solve the problem of high-frequency and high-noise signal tracking, complete the high-speed and accurate tracking of the two-dimensional nanometer positioning platform, and can be used for influencing the design of an atomic force microscope.
The embodiment of the invention also provides a design method of the nano positioning platform control system based on the switching structure, which has the design principle that: firstly, static compensation calibration is completed by using open-loop data, then real-time control of a nano positioning system is completed by using a controller of a closed-loop circuit, and potential interference and model errors are eliminated; according to the sequence from inside to outside, the three-level control structure is designed firstly, then the two-level control structure is designed, and finally the first-level control structure is designed.
A first part: static compensation module design. Specifically, S101-S102 and S201-S203 are included.
S101 is an open loop identification process of the nano positioning platform. Specifically, for example, a sinusoidal voltage signal with the amplitude of 40V and the frequency of 100Hz is given through a voltage amplifier and is sequentially input into a piezoelectric ceramic driver as an input signal to drive the nano positioning platform to move; the displacement feedback data of the capacitive sensor 6s is collected at a sampling frequency of 2MHz as output data. Thereby, the collection process of open loop data is completed.
S102 is an open loop static noise data acquisition process of the nano positioning platform. Specifically, the given voltage signal of the piezoelectric ceramic driver is 0, under which condition displacement feedback data of the capacitive sensor 6s is collected at a sampling frequency of 2MHz as static noise data.
Further, based on the data acquired in S101-S102, the static compensation process of the model in S201-S203 is completed.
S201 is parameter design of a damping compensator. Specifically, according to the open-loop data obtained in S101, a linear system identification box of matlab is used to identify and obtain a transfer function P (S) of the nano positioning platform system:
The model is a third-order system, and the pole-zero of P(s) can be changed by using a damping compensator, so that a second-order form which is easy to control is obtained. In particular, utilize The allocation design is carried out on the zero poles of P(s), and the main transfer function in the P(s) model is/>Damping coefficient is xi=0.05, and transfer function form of damping compensator is/>Which is a second order linear compensator.
S202 is a parameter design process of the hysteresis canceller. In order to eliminate hysteresis, a linear operator model is firstly constructed, and in the embodiment, a Prandtl-ISHLINSKII linear operator model is selected for modeling:
Wherein v (t) is signal input, y c (t) is signal output, F is operator model, p 0 and p (r) are parameters to be identified, and positive operator number r=10 is taken here. 11 parameters can be identified according to open loop data, namely [0.0827,0.0827,0.0259,0.0076,0.0165,0.0025,0.0149,0.0186-0.0044,0.0359,0.0281 ] respectively, and the 11 parameters can be used for constructing a positive hysteresis model, and the hysteresis model of the inverse can be analyzed and calculated based on the positive hysteresis model:
Wherein w (t) is the inverse model input, Is an inverse model operator,/>To construct the parameters of the inverse model, the total number of inverse operators n=11. The 11 parameters a of the inverse hysteresis model calculated from the above parameters p 0, p (r) and w (t) are [12.097, -6.0485, -0.8194, -0.1989, -0.3847, -0.0532, -0.2948, -0.3187, -0.0704, -0.5142,0.3197], thereby completing the design and parameter identification of the inverse hysteresis canceller.
S203 is a design process of the adaptive filter. Specifically, the sensor displacement output data acquired in S101 and S102 are subjected to fast Fourier transform, spectrum data obtained by the fast Fourier transform show that the amplitude is maximum near the main frequency, and other auxiliary frequencies are scattered; the latter obtained spectral data shows that the noise is uniformly distributed in each band, similar to white noise. The high-pass/low-pass filtering cannot solve the noise problem, so that the self-adaptive mean filtering is used as a main filtering means, the low-pass filtering is used as an auxiliary means, the former is weighted more, the average summation is carried out on data of every 10 samples, the latter is given less weight, and the high-frequency noise is filtered.
A second part: and (5) dynamic control module design. Specifically, the method comprises D101-D103 and D201-D202.
D101 is the parameter selection process of the nanometer positioning scanning mode and the scanning frequency. In this embodiment, the nano-positioning platform adopts the most commonly used mode of fast-slow axis matching and progressive scanning, and here, the difficult fast axis control is considered, and the given frequency of the fast axis direction is 100Hz and the amplitude is 1um triangular wave signal.
D102 is the rectified signal switching process. For the reference signal, D102, the triangular wave signal is changed into a ramp wave signal, and the specific expression is y' = (-1) (i-1) r (t) +2[ i/2] a, and the periodic signal is changed into a ramp wave signal by performing signal switching every 0.005s, in this embodiment, the first rectifying signal switcher and the second rectifying signal switcher have the same form, while maintaining the same parameters.
D103 is the inversion signal switching process. The ramp wave signal is inversely switched into a triangular wave signal, the specific expression is y= (-1) (i-1)r(t)+2(-1)i [ i/2] A, and the signal switching frequency in D103 and D102 is 200Hz.
D201 and D202 are respectively the design process of the secondary controller parameter and the primary controller parameter. The design principle from inside to outside is followed in D201 and D202. Since the main way of designing the integrator parameters is by calculating an initial range and then optimizing the final controller parameters continuously in practical experiments. Therefore, in this embodiment, the second integrator in the inner loop two-stage control structure obtained by optimization is calculated asSo that the difference between the input of the secondary control structure and the filtered sensor feedback signal is minimized. After the inner loop secondary control structure is obtained, parameters of a first integrator in the outer loop primary control structure are matched and designed, the first integrator needs to be capable of well tracking rectified ramp signals, and finally the first integrator is obtained in the form of/>
Based on the above, the design calculation of all parameters in the nano positioning platform control system based on the switching structure in the embodiment is completed. It should be noted that the above is only to illustrate the design flow by taking a specific scenario as an example, and parameters of each device may take other values.
Referring to fig. 3, an effect diagram of the two-dimensional nano-positioning platform under the control of the nano-positioning platform control system based on the switching structure is shown. It can be seen that under the control of the system in this embodiment, the two-dimensional nano positioning platform can complete the tracking process of the triangular wave reference signal with the amplitude of 1 μm and 100Hz, the average relative error of signal tracking is 1.4%, and the maximum relative error is not more than 3.5%. In actual operation, under the condition that the technical schemes are the same or similar, the structural form and the device parameters can be flexibly changed to meet the actual demands.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (3)
1. A nano-positioning platform control system based on a switching structure, comprising:
The first rectification switcher is used for rectifying a non-smooth input signal input into the system into a smooth input signal and outputting the smooth input signal;
The input end of the second rectification switcher is connected with the output end of the controlled nano positioning platform and is used for rectifying a non-smooth output signal of the controlled nano positioning platform into a smooth feedback signal and negatively feeding back the smooth feedback signal to the first adder;
The first adder is used for subtracting the smooth input signal from the smooth feedback signal to obtain a first difference signal and outputting the first difference signal;
the first integrator is used for carrying out integration processing on the first difference signal to obtain a first integrated signal and outputting the first integrated signal;
An inversion switch for inverting the first integrated signal into a non-smooth integrated signal and outputting the non-smooth integrated signal;
The control unit is used for generating a corresponding control signal according to the non-smooth integral signal and controlling the controlled nano positioning platform by utilizing the control signal;
The control unit includes:
the input end of the self-adaptive filter is connected with the output end of the controlled nano positioning platform and is used for carrying out self-adaptive filtering on a non-smooth output signal of the controlled nano positioning platform and then negatively feeding back to the second adder;
The second adder is used for subtracting the non-smooth integral signal from the signal output by the adaptive filter to obtain a second difference signal and outputting the second difference signal;
The second integrator is used for carrying out integration processing on the second difference signal to obtain a second integrated signal and outputting the second integrated signal;
the control subunit is used for generating the control signal according to the second integral signal and controlling the controlled nano positioning platform by utilizing the control signal;
The control subunit includes:
The input end of the damping compensator is connected with a driver of the controlled nano positioning platform and is used for carrying out damping compensation on the resonance wave crest of the controlled nano positioning platform and then negatively feeding back to the third adder;
The third adder is used for subtracting the second integrated signal from the signal output by the damping compensator to obtain a third difference signal and outputting the third difference signal;
The hysteresis eliminator is used for generating the control signal according to the third difference value signal by utilizing a nonlinear hysteresis inverse model and controlling the controlled nanometer positioning platform by utilizing the control signal;
the first integrator, the inversion switcher and the control unit form a primary control structure, the control unit is a secondary control structure embedded in the primary control structure, the control subunit is a tertiary control structure embedded in the secondary control structure, and parameters of each stage of control structure are sequentially determined from inside to outside;
The self-adaptive filter is used for carrying out fast Fourier transform on the non-smooth output signal to obtain a noise spectrogram, adaptively selecting one or more filtering modes according to noise distribution in the noise spectrogram, and setting corresponding weights for the filtering modes so as to carry out self-adaptive filtering;
The system utilizes the damping compensator to change the zero pole of the transfer function of the controlled nano positioning platform, reduces the order of the transfer function of the controlled nano positioning platform, reduces the open-loop first resonant frequency of the controlled nano positioning platform, and realizes damping reduction compensation;
The rectification modes of the first rectification switcher and the second rectification switcher are as follows:
y′＝(-1)(i-1)r(t)+2[i/2]A
the inversion mode of the inversion switcher is as follows: y= (-1) (i-1)r(t)+2(-1)i [ i/2] a; y' is the rectified signal, r (t) is the signal before rectification, i is the system time, A is the amplitude of r (t), y is the inverted signal, and the y and r (t) frequencies are the same.
2. The system of claim 1, wherein the first integrator is a second order or more integrator and the second integrator is a first order integrator.
3. The nano-positioning platform control system based on a switching structure according to claim 1, wherein the hysteresis canceller builds the nonlinear hysteresis inverse model by means of linear operator superposition.
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