Self-adaptive control method for piezoelectric ceramic output force in temperature change environment

Abstract

The invention belongs to the field of piezoelectric ceramic output characteristic measurement, and discloses a piezoelectric ceramic output force adaptive control method in a temperature change environment. The method comprises the following steps: firstly, building an output characteristic test platform of the piezoelectric actuator in a variable-temperature environment, collecting experimental data of input voltage and output force of the piezoelectric ceramic actuator, building an output force-voltage dynamic hysteresis model of the piezoelectric actuator through the test data, solving a hysteresis inverse model on the basis, compensating the output force lost due to a hysteresis effect, and calculating the output characteristic of the piezoelectric actuator according to the hysteresis inverse model. And finally, constructing a variable parameter algorithm of the piezoelectric ceramic output force-voltage model in the temperature change environment, selecting adaptive model parameters through temperature feedback, and forming a variable parameter regulation and control method of the output force-voltage model in the temperature change environment. According to the method, the practicability of an output force-voltage model is improved by applying a variable parameter algorithm, the problems of reduction of piezoelectric ceramic output performance and system control instability caused by temperature change in an actual system are avoided, and meanwhile, factors such as dynamic hysteresis of the piezoelectric ceramic actuator are considered.

Description

Technical Field

[0001] The invention belongs to the field of piezoelectric ceramic output characteristic measurement and relates to a piezoelectric ceramic output force adaptive control method. Background Art

[0002] Aircraft wind tunnel model tests can obtain their key aerodynamic characteristics and effectively reduce their development technical risks and costs. Due to the small interference to the flow field, aircraft models are often fixed in the wind tunnel by cantilever support to achieve the measurement of model aerodynamics. However, during the wind tunnel test, the model cantilever support has low stiffness and weak damping, and is prone to irregular vibration due to the disturbance of the unsteady flow field, resulting in inaccurate aerodynamic measurement data at a fixed angle of attack. Therefore, the vibration of the wind tunnel model must be actively suppressed to ensure the accuracy and smooth progress of the wind tunnel test data.

[0003] With the rapid development of piezoelectric materials, due to their fast response speed, compact structure and other characteristics, they can efficiently convert electrical energy into mechanical energy. As an actuator for aircraft wind tunnel models, they can achieve good vibration suppression effects. Active vibration control methods based on piezoelectric ceramic actuators are widely used. However, the output characteristics of piezoelectric ceramics are different at different temperatures, and there are obvious differences in the control effects. The output modeling method with fixed parameters cannot fully exert the vibration suppression ability of the actuator, and the output performance of the wind tunnel model vibration control system is limited. Therefore, it is necessary to consider the influence of variable temperature conditions on the vibration suppression output characteristics, and model the output characteristics of the vibration suppression force, so as to achieve precise control of the vibration suppression force and efficient and rapid suppression of aircraft model vibration.

[0004] Liu Yu et al.'s patent "Large aspect ratio model longitudinal vibration front and rear shock absorber coordination control method and system" with patent number CN202210922741.X introduces a large aspect ratio model longitudinal vibration front and rear shock absorber coordination control method, which uses the accelerometer signal of the vibration suppression system's center of mass as the feedback signal, and according to the principle of moment balance, drives the front shock absorber located between the balance and the strut and the rear shock absorber located in the middle bracket of the strut, respectively, which can effectively determine the shock absorber output for the vibration at different positions of the "model-balance-strut system", and realize the front and rear shock absorber coordination control of the longitudinal vibration of the large aspect ratio model in the wind tunnel test. However, this method does not consider the relationship between the input and output changes of piezoelectric ceramics at different temperatures, and cannot be applied to the active vibration suppression system of the aircraft wind tunnel model that changes in temperature and needs to consider the force-voltage dynamic hysteresis.

[0005] Based on the problems existing in the above technologies, it is necessary to propose an adaptive control method for the output force of piezoelectric ceramics under temperature-changing environment. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present invention proposes an adaptive control method for the output force of piezoelectric ceramics under a temperature-varying environment, taking into account the influence of variable temperature conditions on the output characteristics of piezoelectric ceramic actuators, and realizing precise control of the output force. The method first builds an output characteristic test platform for piezoelectric actuators under a variable temperature environment, collects experimental data on the input voltage and output force of the piezoelectric ceramic driver, and then constructs a dynamic hysteresis model of the output force-voltage of the piezoelectric actuator through the test data. On this basis, the hysteresis inverse model is solved to compensate for the output force lost due to the hysteresis effect. Finally, a variable parameter algorithm for the output force-voltage model of piezoelectric ceramics under a temperature-varying environment is constructed, and the adapted model parameters are selected through temperature feedback to form a variable parameter control method for the output force-voltage model under a temperature-varying environment, thereby improving the driving accuracy and response stability of the piezoelectric actuator. The use of variable parameter algorithm improves the practicability of the output force-voltage model, avoids the problem of temperature changes in actual systems leading to reduced piezoelectric ceramic output performance and system control instability, and takes into account factors such as the dynamic hysteresis of the piezoelectric ceramic actuator. Compared with the traditional single parameter modeling method, it is more universal and effective and can be applied to various systems containing piezoelectric ceramic actuators.

[0007] The technical solution of the present invention:

[0008] A method for adaptively controlling the output force of piezoelectric ceramics under a temperature-varying environment is disclosed. The output force of piezoelectric ceramics under different temperatures and input voltages is measured through a piezoelectric ceramic actuator output characteristic test platform, and an output force-voltage dynamic hysteresis model and a variable parameter algorithm are constructed. A variable parameter control method for the model under a temperature-varying environment is formed through temperature feedback. The method uses a variable parameter algorithm to improve the practicality of the piezoelectric ceramic output force-voltage model, and avoids the problem of reduced output performance of piezoelectric ceramics and instability of system control caused by temperature changes in actual systems.

[0009] The specific steps are as follows:

[0010] Step 1: Build a test platform for the output characteristics of piezoelectric ceramic actuators under temperature variation

[0011] Assemble the piezoelectric ceramic force output characteristic test platform, and realize different temperature environments through high and low temperature test chambers; install the piezoelectric ceramic actuator to the piezoelectric ceramic output characteristic test device, and apply a preload force to the piezoelectric ceramic actuator; connect the power amplifier to the piezoelectric ceramic actuator; connect the piezoelectric ceramic actuator, thermocouple, and force sensor to the data acquisition module; collect the input voltage and output force data of the piezoelectric ceramic actuator at different temperatures;

[0012] Step 2: Construct a dynamic hysteresis model of the output force-voltage of a piezoelectric ceramic actuator

[0013] Based on the classic hysteresis model, the Prandtl-Ishlinskii (PI) model is used as the basic framework. The model can better describe the hysteresis characteristics and has certain flexibility and scalability. Aiming at the limitations of the PI model in practical applications, a unilateral aubacklash operator with asymmetric characteristics is proposed. By improving the threshold distribution characteristics and adding an asymmetric correction coefficient, the strict symmetric characteristics of the backlash operator output are eliminated, and the corresponding API model is obtained.

[0014] Mechano-electric hysteresis operator:

[0015] H a , r , b , c [ u ] ( t ) = max { au + r ,min { bu + c , H ( t − 1 ) } } (1)

[0016] Output force-voltage dynamic hysteresis API model:

[0017] F API [ u ] ( t ) = ∑ i = 1 n w i H a i , r i , b i , c i [ u ] ( t ) = w T H [ u ] ( t ) (2)

[0018] Modify the threshold parameters in the API model to associate the original hysteresis operator threshold parameters with the frequency:

[0019] (3)

[0020] The hysteresis model calculation output can change with the change of input voltage frequency, and the output force-voltage dynamic hysteresis model of the piezoelectric ceramic actuator is obtained; wherein, H a , r , b , c [ u ] ( t ) is the output of the force-electric hysteresis operator, is the hysteresis operator output at the previous moment, is the input voltage, , is the asymmetric correction coefficient of the hysteresis operator, is the threshold of the mechano-electric hysteresis operator, is a numeric constant, F API [ u ] ( t ) is the output force of the piezoelectric ceramic under force-electric hysteresis, is the number of force-electric hysteresis operators, is the weight of the electro-mechanical hysteresis operator, is the weight matrix of the electromechanical hysteresis operator, H [ u ] ( t ) is the electromechanical hysteresis operator matrix, is a numeric constant, is the voltage derivative, is the initial value of the numerical constant;

[0021] Step 3: Solve the hysteresis inverse model of the piezoelectric ceramic actuator to compensate the output force

[0022] The hysteresis inverse model is solved by numerical method. First, the output force data under different input voltages and input frequencies are generated by using the built piezoelectric ceramic force-position output characteristic test platform to form a data set. A neural network is constructed, with the output force and frequency as the input layer neurons and the input voltage as the output layer neurons. The neural network is trained with a large amount of data to learn the mapping law from output force, frequency to input voltage, thereby obtaining an inverse model. When the desired output force is given, it is input into the inverse model to obtain the corresponding compensation voltage, and then the compensation voltage is applied to the piezoelectric ceramic actuator as the actual input voltage, thereby compensating for the output force lost due to hysteresis and making the output force closer to the desired output force.

[0023] Step 4: Construct variable parameter algorithm for hysteresis model under variable temperature environment

[0024] Based on the above API dynamic hysteresis model, temperature-related terms are introduced. The ambient temperature is set as T, and the temperature-time function h(T) is constructed. The asymmetric correction coefficient of the original hysteresis operator in the API model is associated with the temperature-time function h(T) to reflect the effect of temperature on model parameters, so that the model characteristics change with temperature. Then, the adaptive model parameters are selected through temperature feedback to improve the universality of the model.

[0025] (4)

[0026] in, , is the temperature correction coefficient, is the temperature change, , is the offset of the temperature correction coefficient;

[0027] The optimized API dynamic hysteresis model is embedded in the piezoelectric ceramic actuator control system, which automatically matches the appropriate parameters to solve the required input voltage according to the real-time temperature and expected output force, achieving precise and intelligent control.

[0028] Beneficial effects of the present invention:

[0029] The method proposed in this paper adopts an adaptive control method for the output force of piezoelectric ceramics under a temperature-changing environment. The constructed API dynamic hysteresis model can accurately solve the input voltage of the piezoelectric ceramic actuator under different temperature environments, and solves the problem that the dynamic hysteresis error of the piezoelectric ceramic actuator is too large and the temperature change is large, which leads to the limited output performance of the piezoelectric ceramic actuator in the actual system, making the control result more accurate and higher in precision. The model is easy and fast to establish and train, has strong adaptability, and can be applied to all systems containing piezoelectric ceramic actuators. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1It is a connection diagram of the output characteristic test platform of the variable temperature environment piezoelectric actuator of the present invention;

[0031] Figure 2 It is a flow chart of the method for adaptively controlling the output force of a piezoelectric ceramic actuator of the present invention;

[0032] Figure 3 The output force data curve of the piezoelectric ceramic actuator at different actuation frequencies when the ambient temperature is 20°C. The X-axis is the input voltage and the Y-axis is the output force.

[0033] Figure 4 The output force-voltage dynamic hysteresis model prediction result curve of piezoelectric ceramic actuator at different actuation frequencies, where the X-axis is the input voltage and the Y-axis is the output force.

[0034] Figure 5 1 is a data curve of the output force of the piezoelectric ceramic actuator at different temperatures in the embodiment, wherein the X-axis is the input voltage and the Y-axis is the output force.

[0035] Figure 6 This is the relationship curve between the asymmetric correction coefficient of the dynamic hysteresis model and temperature. The X-axis is the ambient temperature and the Y-axis is the symmetric correction coefficient value.

[0036] Figure 7 The following is the prediction result curve of the output force-voltage dynamic hysteresis model of the piezoelectric ceramic actuator at different temperatures, where the X-axis is the input voltage and the Y-axis is the output force.

[0037] In the figure: 1-power amplifier, 2-high and low temperature test chamber, 3-piezoelectric ceramic output characteristic test device, 4-piezoelectric ceramic actuator, 5-thermocouple, 6-force sensor, 7-data acquisition module, 8-real-time controller, 9-host computer. DETAILED DESCRIPTION

[0038] The implementation process of the present invention is described in detail below in conjunction with the technical scheme and the accompanying drawings.

[0039] Figure 1 The output force data collection principle diagram of the piezoelectric ceramic actuator. The piezoelectric ceramic output characteristic test device 3 used has a built-in thermocouple 5 and a force sensor 6, which can obtain the ambient temperature and the output force of the piezoelectric ceramic actuator 4 in real time. The overall test system can ensure the synchronous measurement and collection of force and electricity, and has the characteristics of compact structure and easy use.

[0040] Figure 2This is a flow chart of the adaptive control method for piezoelectric ceramic output force under temperature-varying environment. The entire predictive modeling method is divided into the following four parts: assembling the piezoelectric ceramic output characteristic test system, constructing the output force-voltage dynamic hysteresis model of the piezoelectric ceramic actuator, solving the hysteresis inverse model of the piezoelectric ceramic actuator to compensate the output force, and constructing a variable parameter algorithm for the hysteresis model under temperature-varying environment and conducting experimental verification.

[0041] Step 1: Build a test platform for the output characteristics of piezoelectric actuators under temperature variation

[0042] like Figure 1 As shown, a piezoelectric ceramic force output characteristic test platform is assembled, and different temperature environments are realized through a high and low temperature test box 2; the piezoelectric ceramic output characteristic test device 3 is an integrated processing configuration, and the bottom end is connected to the force sensor 6 through bolts. A through groove is opened in the center of the piezoelectric ceramic output characteristic test device 3 to install the piezoelectric ceramic actuator 4, and an initial pre-tightening force is applied to the piezoelectric ceramic actuator 4 through the bolts at the top of the piezoelectric ceramic output characteristic test device 3; the power amplifier 1 is connected to the piezoelectric ceramic actuator 4; the piezoelectric ceramic actuator 4, the thermocouple 5, and the force sensor 6 are connected to the data acquisition module; the input voltage and output force data of the piezoelectric ceramic actuator 4 at different temperatures are collected;

[0043] Conduct data acquisition experiments, control the test system to output a variable frequency sinusoidal voltage input signal through LabVIEW software; the host computer 9 transmits the control signal to the real-time controller 8, which then transmits it to the power amplifier 1. The power amplifier 1 converts the control signal into a voltage input to the piezoelectric ceramic actuator 4. The piezoelectric ceramic output characteristic test device 3 is placed in a high and low temperature test chamber 2, and multiple groups of experiments are carried out at different temperatures. The data acquisition module 7 reads and stores the pressure sensor output signal in real time, thereby completing the output force data acquisition;

[0044] In this embodiment, LabVIEW software is used to control the test system to input a sinusoidal voltage with a gradually increasing amplitude, and the formula is as follows:

[0045] (5)

[0046] The parameters in the formula are , .

[0047] Step 2: Construct a dynamic hysteresis model of the output force-voltage of a piezoelectric ceramic actuator

[0048] Based on the classic hysteresis model, the Prandtl-Ishlinskii (PI) model is used as the basic framework. The model can better describe the hysteresis characteristics and has certain flexibility and scalability. Aiming at the limitations of the PI model in practical applications, a unilateral aubacklash operator with asymmetric characteristics is proposed. By improving the threshold distribution characteristics and adding an asymmetric correction coefficient, the strict symmetric characteristics of the backlash operator output are eliminated, and the corresponding API model is obtained.

[0049] Mechano-electric hysteresis operator:

[0050] H a , r , b , c [ u ] ( t ) = max { au + r ,min { bu + c , H ( t − 1 ) } } (1)

[0051] Output force-voltage dynamic hysteresis API model:

[0052] F API [ u ] ( t ) = ∑ i = 1 n w i H a i , r i , b i , c i [ u ] ( t ) = w T H [ u ] ( t ) (2)

[0053] Modify the threshold parameters in the API model to associate the original hysteresis operator threshold parameters with the frequency:

[0054] (3)

[0055] The hysteresis model calculation output can change with the change of input voltage frequency, and the output force-voltage dynamic hysteresis model of the piezoelectric ceramic actuator is obtained; wherein, H a , r , b , c [ u ] ( t ) is the output of the force-electric hysteresis operator, is the hysteresis operator output at the previous moment, is the input voltage, , is the asymmetric correction coefficient of the hysteresis operator, is the threshold of the mechano-electric hysteresis operator, is a numeric constant, F API [ u ] ( t ) is the output force of the piezoelectric ceramic under force-electric hysteresis, is the number of force-electric hysteresis operators, is the weight of the electro-mechanical hysteresis operator, is the weight matrix of the electromechanical hysteresis operator, H [ u ] ( t ) is the electromechanical hysteresis operator matrix, is a numeric constant, is the voltage derivative, is the initial value of the numerical constant;

[0056] Step 3: Solve the hysteresis inverse model of the piezoelectric ceramic actuator to compensate the output force

[0057] The hysteresis inverse model is solved by numerical method. First, the output force data under different input voltages and input frequencies are generated by using the constructed piezoelectric ceramic force-position output characteristic test platform to form a data set. The piezoelectric ceramic driver input voltage and output force neural network is constructed by MATLAB software, with the output force and actuation frequency as the input layer neurons, and the input voltage as the output layer neurons. The initial weight and threshold of each node are set to a random number between 1 and -1. The neural network is trained with a large amount of data to learn the mapping law from output force, frequency to input voltage, thereby obtaining an inverse model. When the desired output force is given, it is input into the inverse model to obtain the corresponding compensation voltage, and then the compensation voltage is applied to the piezoelectric ceramic actuator as the actual input voltage, thereby compensating for the output force lost due to hysteresis and making the output force closer to the desired output force.

[0058] Step 4: Construct variable parameter algorithm for hysteresis model under variable temperature environment

[0059] Based on the above API dynamic hysteresis model, temperature-related terms are introduced. The ambient temperature is set as T, and the temperature-time function h(T) is constructed. The asymmetric correction coefficient of the original hysteresis operator in the API model is associated with the temperature-time function h(T) to reflect the effect of temperature on the model parameters and make the model characteristics change with temperature. Then, the adaptive model parameters are selected through the feedback of the ambient temperature data by thermocouples to improve the universality of the model.

[0060] (4)

[0061] The optimized API dynamic hysteresis model is embedded in the piezoelectric ceramic actuator control system, and preset experiments are carried out on the piezoelectric ceramic force output device. The required input voltage is automatically solved by automatically matching appropriate parameters according to the real-time temperature and expected output force. At the same time, the output force of the piezoelectric ceramic actuator is measured in real time and compared with the expected output value to verify the effectiveness of the established piezoelectric ceramic output force adaptive control method.

[0062] This method proposes an adaptive control method for the output force of piezoelectric ceramics under a temperature-varying environment. The constructed API dynamic hysteresis model of the piezoelectric ceramic actuator takes into account the influence of the dynamic hysteresis of the piezoelectric ceramics and the external ambient temperature. It can accurately solve the input voltage of the piezoelectric ceramic actuator under different temperature environments, and solves the problem of the piezoelectric ceramic actuator's output performance being limited due to excessive dynamic hysteresis error and large temperature changes in the actual system, making the control result more accurate and higher in precision. The model is easy and fast to establish and train, has strong adaptability, and can be applied to all systems containing piezoelectric ceramic actuators.

Claims

1. A method for adaptively controlling the output force of piezoelectric ceramics under temperature-varying conditions, characterized in that: Here are the steps: Step 1: Build a test platform for the output characteristics of piezoelectric ceramic actuators under temperature variation The piezoelectric ceramic actuator is installed on the piezoelectric ceramic output characteristic test device, and a preload force is applied to the piezoelectric ceramic actuator; the power amplifier is connected to the piezoelectric ceramic actuator; the piezoelectric ceramic actuator, the thermocouple, and the force sensor are all connected to the data acquisition module; the input voltage and output force data of the piezoelectric ceramic actuator at different temperatures are collected; Step 2: Construct the piezoelectric ceramic actuator output force-voltage dynamic hysteresis API model The PI model is selected as the basic framework, and a unilateral aubacklash operator with asymmetric characteristics is proposed. By improving the threshold distribution characteristics and adding an asymmetric correction coefficient, the strict symmetric characteristics of the backlash operator output are eliminated, and the output force-voltage dynamic hysteresis API model is obtained. Mechano-electric hysteresis operator: （1） Output force-voltage dynamic hysteresis API model: （2） Modify the threshold parameters in the output force-voltage dynamic hysteresis API model and associate the original hysteresis operator threshold parameters with frequency: （3） The output of the hysteresis model changes with the input voltage frequency, and the output force-voltage dynamic hysteresis API model of the piezoelectric ceramic actuator is obtained; in, is the output of the force-electric hysteresis operator, is the hysteresis operator output at the previous moment, is the input voltage, , is the asymmetric correction coefficient of the hysteresis operator, is the threshold of the mechano-electric hysteresis operator, is a numeric constant, is the output force of the piezoelectric ceramic under force-electric hysteresis, is the number of force-electric hysteresis operators, is the weight of the electro-mechanical hysteresis operator, is the weight matrix of the electromechanical hysteresis operator, is the electromechanical hysteresis operator matrix, is a numeric constant, is the voltage derivative, is the initial value of the numerical constant; Step 3: Solve the hysteresis inverse model of the piezoelectric ceramic actuator to compensate the output force The hysteresis inverse model is solved by a numerical method. First, the output characteristic test platform is used to generate output force data generated under different input voltages and input frequencies to form a data set. A neural network is constructed, with the output force and input frequency as input layer neurons and the input voltage as output layer neurons. The neural network is trained with the data in the data set to learn the mapping law from output force, input frequency to input voltage, and obtain the hysteresis inverse model. When the desired output force is given, it is input into the hysteresis inverse model to obtain the corresponding compensation voltage, and then the compensation voltage is applied to the piezoelectric ceramic actuator as the actual input voltage, thereby compensating for the output force lost due to hysteresis and making the output force closer to the desired output force. Step 4: Construct variable parameter algorithm for hysteresis model under variable temperature environment On the basis of the output force-voltage dynamic hysteresis API model, the temperature-related term is introduced, the ambient temperature is set as T, and the temperature-time variation function h(T) is constructed. The original asymmetric correction coefficient of the hysteresis operator in the output force-voltage dynamic hysteresis API model is associated with the temperature-time variation function h(T) to reflect the effect of the ambient temperature on the output force-voltage dynamic hysteresis API model parameters, so that the output force-voltage dynamic hysteresis API model characteristics change with temperature, and then the adaptive output force-voltage dynamic hysteresis API model parameters are selected through temperature feedback to improve the universality of the output force-voltage dynamic hysteresis API model. （4） in, , is the temperature correction coefficient, is the temperature change, , is the offset of the temperature correction coefficient; The optimized output force-voltage dynamic hysteresis API model is embedded in the control system of the piezoelectric ceramic actuator, and the required input voltage is automatically solved by automatically matching appropriate parameters according to the real-time temperature and expected output force, thus achieving precise and intelligent control.

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