Piezoelectric driver hysteresis modeling and feedforward control method based on improved PI model

文档序号:1672407 发布日期:2019-12-31 浏览:9次 中文

阅读说明:本技术 基于改进pi模型的压电驱动器迟滞建模及前馈控制方法 (Piezoelectric driver hysteresis modeling and feedforward control method based on improved PI model ) 是由 王文 王健 王瑞金 居冰峰 徐振龙 周茂瑛 于 2019-09-16 设计创作,主要内容包括:本发明公开了基于改进PI模型的压电驱动器迟滞建模及前馈控制方法。传统PI模型在描述压电陶瓷驱动器的非对称迟滞曲线时,误差大。本发明基于改进PI模型的迟滞非线性模型设计压电陶瓷驱动器的前馈控制器,把各时刻压电陶瓷驱动器的期望输出位移输入到前馈控制器,并利用迭代关系式进行迭代,求得压电陶瓷驱动器迭代完成后的输入电压,然后将该电压作用于压电陶瓷驱动器上,得到压电陶瓷驱动器在各个时刻对应的实际输出位移。本发明可以改变单个算子在零点处的输出位移,提高模型在零点处的精度;改进PI模型能同时表征对称与非对称的迟滞曲线,基于改进PI模型压电驱动器的前馈控制器可以很好抑制压电陶瓷驱动器的迟滞特性。(The invention discloses a piezoelectric driver hysteresis modeling and feedforward control method based on an improved PI model. When the traditional PI model describes the asymmetric hysteresis curve of the piezoelectric ceramic driver, the error is large. The invention designs a feedforward controller of a piezoelectric ceramic driver based on a hysteresis nonlinear model of an improved PI model, inputs expected output displacement of the piezoelectric ceramic driver at each moment into the feedforward controller, iterates by using an iteration relational expression to obtain input voltage after the iteration of the piezoelectric ceramic driver is completed, and then acts on the piezoelectric ceramic driver to obtain the corresponding actual output displacement of the piezoelectric ceramic driver at each moment. The invention can change the output displacement of a single operator at the zero point, and improve the precision of the model at the zero point; the improved PI model can represent symmetric and asymmetric hysteresis curves at the same time, and a feedforward controller of the piezoelectric driver based on the improved PI model can well inhibit the hysteresis characteristic of the piezoelectric ceramic driver.)

1. The piezoelectric driver hysteresis nonlinear model modeling method based on the improved PI model is characterized in that: the method comprises the following specific steps:

1) the Play operator is improved to be an M-Play operator:

y(t)=p·max{u(t)-r,min{u(t)+ηr,y(t-T)}}

wherein y (T) is output displacement of the operator at the time T, u (T) is input voltage of the operator at the time T, p is a weight coefficient, r is a threshold, T is a time interval of input voltage at an adjacent time point, eta is a threshold correction coefficient, max is a maximum value, and min is a minimum value;

2) improving the PI model into a PMPI model, namely a piezoelectric driver hysteresis nonlinear model based on the improved PI model; the PMPI model is as follows:

Figure FDA0002202833230000011

wherein, y0Is the initial displacement of a piezoceramic driver, i.e. piezoceramic driverThe output displacement of the actuator at the time point 0 is Y (0), Y (t) is the output displacement of the piezoelectric ceramic actuator at the time point t, p0Is a linear coefficient, piIs the weight coefficient of the ith operator, riIs the threshold value of the ith operator, etaiThreshold correction factor for the ith operator, a1And a2Are all nonlinear coefficients, n is the total number of operators, yi(T-T) is the output displacement of the ith operator at the time T-T.

2. The feedforward control method of the piezoelectric driver based on the improved PI model is characterized in that: the method comprises the following specific steps:

designing the feedforward controller expression of the piezoelectric ceramic driver as follows:

Figure FDA0002202833230000012

u to the right of the equation for the feedforward controller expressiondU for (t)d(T-T) and set ud(0) When the voltage is equal to 0, the iterative relationship between the T moment and the T-T moment is obtained as follows:

Figure FDA0002202833230000013

wherein, yd(t) is the desired output displacement of the piezoceramic driver, ud(t) is the piezoelectric ceramic actuator input voltage obtained from the desired output displacement of the piezoelectric ceramic actuator at time t, ud(T-T) is the piezoelectric ceramic driver input voltage obtained according to the expected output displacement of the piezoelectric ceramic driver at the time of (T-T); part of a non-linear polynomial

Figure FDA0002202833230000014

Figure FDA0002202833230000023

wherein the content of the first and second substances,

Figure FDA0002202833230000024

And (2) inputting the expected output displacement of the piezoelectric ceramic driver at each moment into a feedforward controller, iterating by using the iteration relation of the formula (1) until the iteration times are equal to the total number of the sampled moment points, obtaining the input voltage of the piezoelectric ceramic driver at each moment, and then acting the input voltage at each moment on the piezoelectric ceramic driver to obtain the corresponding actual output displacement of the piezoelectric ceramic driver at each moment.

Technical Field

The invention belongs to the technical field of micro-nano driving, and particularly relates to piezoelectric driver hysteresis nonlinear modeling based on an improved PI model and a feedforward control method of a piezoelectric ceramic driver.

Background

In recent years, with the rapid development of microelectronic information device manufacturing, micro-nano manufacturing and ultra-precision machining technologies, the requirement of manufacturing equipment on precision is higher and higher. Motor drivers in the traditional sense cannot meet the rigorous requirements of precise motion, and intelligent material drivers capable of directly converting electric or magnetic energy into mechanical energy need to be adopted. The piezoelectric ceramic driver has the advantages of high displacement resolution, high frequency response, high rigidity, small volume, high reliability and the like, and is widely applied to the fields of micro-nano processing equipment, precise instruments and meters, atomic force microscopes, ultra-precise machine tools and the like.

The piezoelectric ceramic driver utilizes the inverse piezoelectric property of piezoelectric material to produce deformation under the action of input voltage or current so as to attain the goal of mechanical movement. However, the piezoelectric ceramic driver has complex hysteresis nonlinearity between an input signal and an output displacement, and compared with the traditional nonlinear characteristic, the hysteresis nonlinearity reflects a special nonlinear relation between the input signal and the output signal. The existence of the hysteresis nonlinear relation reduces the driving precision of the piezoelectric ceramic driver and seriously influences the application of the piezoelectric ceramic driver.

At present, scholars at home and abroad propose various hysteresis nonlinear modeling methods, such as a Prandtl-Ishlinskii model (commonly called PI model). However, the conventional PI model has poor precision when describing the residual displacement at the zero point, and can only be used for representing a symmetric hysteresis curve, and a large error is generated when describing an asymmetric hysteresis curve of the piezoelectric ceramic driver. In addition, when designing a feedforward controller for a piezoelectric ceramic driver, an inverse model of the hysteresis nonlinear model is required. The accuracy and solution of the inverse model determines the compensation accuracy and complexity of the feedforward controller.

Disclosure of Invention

Aiming at the limitation of the existing modeling method, the invention provides a piezoelectric ceramic driver hysteresis nonlinear modeling based on an improved PI model and a feedforward control method of the piezoelectric ceramic driver. The modeling method can represent symmetric and asymmetric hysteresis curves at the same time, and effectively improves the precision of residual displacement at the zero point of the model.

The invention relates to a piezoelectric driver hysteresis nonlinear model modeling method based on an improved PI model, which comprises the following specific steps:

1) the Play operator is improved to be an M-Play operator:

y(t)=p·max{u(t)-r,min{u(t)+ηr,y(t-T)}}

wherein y (T) is output displacement of the operator at the time T, u (T) is input voltage of the operator at the time T, p is a weight coefficient, r is a threshold, T is a time interval of input voltage at an adjacent time point, eta is a threshold correction coefficient, max is a maximum value, and min is a minimum value.

2) Improving the PI model into a PMPI model, namely a piezoelectric driver hysteresis nonlinear model based on the improved PI model; the PMPI model is as follows:

wherein, y0Is the initial displacement of the piezoelectric ceramic driver, i.e. the output displacement Y (0) of the piezoelectric ceramic driver at the time 0, Y (t) is the output displacement of the piezoelectric ceramic driver at the time t, p0Is a linear coefficient, piIs the weight coefficient of the ith operator, riIs the threshold value of the ith operator, etaiThreshold correction factor for the ith operator, a1And a2Are all nonlinear coefficients, n is the total number of operators, yi(T-T) is the output displacement of the ith operator at the time T-T.

The invention relates to a feedforward control method of a piezoelectric driver based on an improved PI model, which comprises the following specific steps:

designing the feedforward controller expression of the piezoelectric ceramic driver as follows:

Figure BDA0002202833240000022

when adjacent time points input electricityThe time interval T of pressing is very small, due to ud(t) and ud(T-T) are nearly equal, so u, to the right of the feedforward controller expression equationdU for (t)d(T-T) and set ud(0) When the voltage is equal to 0, the iterative relationship between the T moment and the T-T moment is obtained as follows:

wherein, yd(t) is the desired output displacement of the piezoceramic driver, ud(t) is the piezoelectric ceramic actuator input voltage obtained from the desired output displacement of the piezoelectric ceramic actuator at time t, ud(T-T) is the piezoelectric ceramic driver input voltage obtained according to the expected output displacement of the piezoelectric ceramic driver at the time of (T-T); part of a non-linear polynomial

Figure BDA0002202833240000025

In order to remove the function sign of the analytical inverse model of the nonlinear polynomial portion, the analytical inverse model of the nonlinear polynomial portion is removed and written asIf 'y'd(t)=yd(t)-P[ud](T-T), thenThe calculation formula of (a) is as follows:

Figure BDA0002202833240000031

wherein the content of the first and second substances,

Figure BDA0002202833240000032

is y'd(t) substituting the analytical inverse model excluding the polynomial part

Figure BDA0002202833240000033

The symbolic expression of the function in (1),

Figure BDA0002202833240000034

to remove the linear coefficients of the analytical inverse model of the polynomial part,

Figure BDA0002202833240000035

to remove the weighting coefficients of the ith operator in the analytical inverse model of the polynomial part,to remove the threshold value, y ', of the ith operator in the analytical inverse model of the polynomial part'd(t-T)=yd(t-T)-P[ud](t-2T)。

And inputting the expected output displacement of the piezoelectric ceramic driver at each moment into a feedforward controller, iterating by using the iteration relation of the formula (1) until the iteration times are equal to the number of sampling points, obtaining the input voltage of the piezoelectric ceramic driver at each moment, and then acting the input voltage at each moment on the piezoelectric ceramic driver to obtain the corresponding actual output displacement of the piezoelectric ceramic driver at each moment.

The invention has the following beneficial effects:

1. compared with the traditional PI model, the improved PI model provided by the invention introduces the parameter eta and the nonlinear polynomial a1u3(t)+a2u2(t); the output displacement of a single operator at the zero point can be changed through the parameter eta, so that the precision of the whole model at the zero point is improved; and a nonlinear polynomial a1u3(t)+a2u2The introduction of (t) makes up the defect that the traditional PI model can only represent the symmetric hysteresis curve, and the improved PI model can simultaneously represent the symmetric and asymmetric hysteresis curves. Compared with the traditional PI model, the improved PI model has the advantage that the precision is obviously improved.

2. The invention solves the inverse model of the improved model in an iterative mode, solves the problem that the analytic inverse model cannot be obtained due to the introduction of a polynomial, and applies the inverse model to a feedforward controller which can well inhibit the hysteresis characteristic of the piezoelectric ceramic driver.

Drawings

FIG. 1 is a schematic diagram of a conventional Play operator;

FIG. 2 is a schematic diagram of the M-Play operator of the present invention at different η values;

FIG. 3 is a schematic diagram of the feed forward controller of the present invention;

FIG. 4 is a diagram showing the effect of fitting a conventional PI model to a PMPI model of the present invention;

FIG. 5 is a graph of the fitting error of a conventional PI model with a PMPI model of the present invention;

FIG. 6 is a graph showing the comparison effect between the actual displacement of the complex attenuation triangular wave and the expected displacement signal obtained by the control method of the present invention;

FIG. 7 is a signal error diagram of the actual displacement and the expected displacement of the complex attenuation triangular wave obtained by the control method of the present invention.

Detailed Description

The invention will be further explained with reference to the drawings.

As shown in FIG. 1, the conventional Play operator (C-Play operator for short) is

y(t)=p·max{u(t)-r,min{u(t)+r,y(t-T)}}

Wherein y (T) is output displacement of the operator at the time T, u (T) is input voltage of the operator at the time T, p is a weight coefficient, r is a threshold value, T is a time interval of input voltage at an adjacent time point, max is a maximum value, and min is a minimum value.

The conventional PI model (CPI model for short) is:

Figure BDA0002202833240000041

wherein, y0Is the initial displacement of the piezoelectric ceramic driver, i.e. the displacement Y (0) of the piezoelectric ceramic driver at the time 0, Y (t) is the output displacement of the piezoelectric ceramic driver at the time t, p0Is a linear coefficient, piIs the weight coefficient of the ith operator, riIs the threshold value of the ith operator, and n is the total number of operatorsNumber, yi(T-T) is the output displacement of the ith operator at the time T-T.

The invention relates to a piezoelectric driver hysteresis nonlinear model modeling method based on an improved PI model, which comprises the following specific steps:

1) as shown in fig. 2, the Play operator is modified to the M-Play operator:

y(t)=p·max{u(t)-r,min{u(t)+ηr,y(t-T)}}

wherein y (T) is output displacement of the operator at the time T, u (T) is input voltage of the operator at the time T, p is a weight coefficient, r is a threshold, T is a time interval of input voltage at an adjacent time point, eta is a threshold correction coefficient, max is a maximum value, and min is a minimum value.

2) The PI model is improved to the PMPI model:

wherein, y0Is the initial displacement of the piezoelectric ceramic driver, i.e. the output displacement Y (0) of the piezoelectric ceramic driver at the time 0, Y (t) is the output displacement of the piezoelectric ceramic driver at the time t, p0Is a linear coefficient, piIs the weight coefficient of the ith operator, riIs the threshold value of the ith operator, etaiThreshold correction factor for the ith operator, a1And a2Are all nonlinear coefficients, n is the total number of operators, yi(T-T) is the output displacement of the ith operator at the time T-T.

Compared with the traditional PI model, the PMPI model introduces a parameter eta and a nonlinear polynomial a1u3(t)+a2u2(t) of (d). As can be seen from fig. 2, the output displacement of a single operator at the zero point can be changed by the parameter η, so as to improve the accuracy of the whole model at the zero point; and a nonlinear polynomial a1u3(t)+a2u2The introduction of (t) makes up for the defect that the traditional PI model can only represent the symmetric hysteresis curve.

As shown in fig. 3, the feedforward control method of the piezoelectric actuator based on the improved PI model specifically includes the following steps:

due to non-linearitySex polynomial a1u3(t)+a2u2(t), the PMPI model does not have an analytic inverse model, and the inverse model can be solved only in an iterative mode, so that the feedforward controller expression for designing the piezoelectric ceramic driver is as follows:

Figure BDA0002202833240000051

when the time interval T of the input voltage at the adjacent time point is small, u is due tod(t) and ud(T-T) are nearly equal, so u, to the right of the feedforward controller expression equationdU for (t)d(T-T) and set ud(0) When the voltage is equal to 0, the iterative relationship between the T moment and the T-T moment is obtained as follows:

Figure BDA0002202833240000052

wherein, yd(t) is the desired output displacement of the piezoceramic driver, ud(t) is the piezoelectric ceramic actuator input voltage obtained from the desired output displacement of the piezoelectric ceramic actuator at time t, ud(T-T) is the piezoelectric ceramic driver input voltage obtained according to the expected output displacement of the piezoelectric ceramic driver at the time of (T-T); part of a non-linear polynomial

Figure BDA0002202833240000053

Figure BDA0002202833240000054

In order to remove the function sign of the analytical inverse model of the nonlinear polynomial portion, the analytical inverse model of the nonlinear polynomial portion is removed and written asThe feedforward controller structure of the piezoelectric ceramic driver is shown in FIG. 3, [ P ]]Representing a non-linear polynomial part P [ u ]d](t-T),[MPI]-1An analytical inverse model excluding the polynomial part, and y (t) is the actual output displacement of the piezoelectric ceramic actuator. If it isRemember 'y'd(t)=yd(t)-P[ud](T-T), then

Figure BDA0002202833240000056

The calculation formula of (a) is as follows:

Figure BDA0002202833240000061

wherein the content of the first and second substances,

Figure BDA0002202833240000062

is y'd(t) substituting the analytical inverse model excluding the polynomial part

Figure BDA0002202833240000063

The symbolic expression of the function in (1),

Figure BDA0002202833240000064

to remove the linear coefficients of the analytical inverse model of the polynomial part,to remove the weighting coefficients of the ith operator in the analytical inverse model of the polynomial part,

Figure BDA0002202833240000066

to remove the threshold value, y ', of the ith operator in the analytical inverse model of the polynomial part'd(t-T)=yd(t-T)-P[ud](t-2T)。

And (2) inputting the expected output displacement of the piezoelectric ceramic driver at each moment into a feedforward controller, iterating by using the iteration relation of the formula (1) until the iteration times are equal to the total number of the sampled moment points, obtaining the input voltage at each moment, and then acting the input voltage at each moment on the piezoelectric ceramic driver to obtain the corresponding actual output displacement of the piezoelectric ceramic driver at each moment. The invention realizes that the actual output displacement of the piezoelectric ceramic driver is basically equivalent to the expected output displacement.

A specific set of parameter values for the PMPI model is given below: as shown in the figureAs shown in fig. 5, 2000 sampling points are selected, and each sampling point corresponds to a time t; setting y0=0,p0T is 4.770, 0.001s, and the threshold of the i-th operator is ri(i-1); a is obtained by differential evolution algorithm (or by adopting least square method, neural network algorithm and other parameter identification methods) identification1、a2And threshold correction coefficient eta of ith operatoriAnd a weight coefficient piAs shown in table 1:

TABLE 1

Figure BDA0002202833240000067

In addition, the parameter values required to give the conventional PI model are shown in table 2:

TABLE 2

Figure BDA0002202833240000071

In Table 2, the weight coefficient piAnd is also identified by a differential evolution algorithm.

As shown in fig. 4, the experimental data is a relationship curve of a given set of voltage data and the actual output displacement data of the corresponding piezoelectric ceramic driver; as can be seen from fig. 4, under the same set of voltage data as the experimental data, the output displacement obtained by the PMPI model based on the specific parameter values is closer to the actual output displacement of the piezoelectric ceramic driver than the output displacement obtained by the conventional PI model based on the specific parameter values; as can be seen from fig. 5, the fluctuation of the curve of the variation of the error between the output displacement based on the PMPI model and the actual output displacement of the piezoelectric ceramic driver with the sampling point position is smaller than the fluctuation of the curve of the variation of the error between the output displacement based on the conventional PI model and the actual output displacement of the piezoelectric ceramic driver with the sampling point position; therefore, the output displacement of the PMPI model of the invention is closer to the actual output displacement of the electroceramic driver than the output displacement of the traditional PI model.

As shown in fig. 6, a feedforward controller of a piezoelectric actuator based on a PMPI model is designed, an expected output displacement of the piezoelectric ceramic actuator at each time is input to the feedforward controller, iteration is performed by using an iteration relation of formula (1), until the number of iterations is equal to 2000, an input voltage of the piezoelectric ceramic actuator at each time is obtained, and then the input voltage at each time is applied to the piezoelectric ceramic actuator, so as to obtain an actual output displacement corresponding to the piezoelectric ceramic actuator at each time; as can be seen from fig. 6, the actual output displacement curve of the piezoelectric ceramic driver based on the PMPI model of the present invention with different times is very close to the expected output displacement curve of the piezoelectric ceramic driver with different times; as can be seen from fig. 7, the variation curve of the error between the actual output position of the piezoelectric ceramic driver based on the PMPI model of the present invention and the expected output displacement of the piezoelectric ceramic driver fluctuates little with different time. Therefore, the invention can solve the inverse model of the PMPI model in an iterative mode and apply the inverse model to the feedforward controller, so that the obtained feedforward controller can well inhibit the hysteresis characteristic of the piezoelectric ceramic driver.

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