| Precision drive technology is one of the important supporting technologies in the fields of precision instruments,biomedicine,integrated circuits and aerospace technology.However,with the continuous development of science and technology,the above-mentioned high-tech fields have increasingly higher requirements on technical characteristics such as the structure size and positioning accuracy of the actuator,and the traditional drive technology has gradually become weak.Piezoelectric drive technology is a new type of drive technology based on the inverse piezoelectric effect,with vibration and friction as the main driving methods.Compared with traditional technology,the driving device using piezoelectric driving technology has the advantages of small size,light weight,high precision,fast response and no magnetic field interference,therefore,it has important application value and development potential.The stick-slip piezoelectric actuator belongs to the stepping piezoelectric actuator.Because of its compact structure,simple control,high precision and large stroke,the stick-slip piezoelectric actuator has received extensive attention from scholars in related fields.However,the existing researches on stick-slip piezoelectric actuator still have some deficiencies in the analysis of performance influencing factors,the theoretical guidance of structural design and optimization,and the research on drive signals and control methods.As a result,the advantages of this type of actuator in terms of structure size,bearing capacity,driving speed and positioning accuracy cannot be fully exerted.In order to solve the above problems,based on the analysis and study of the principle and mechanism of the stick-slip piezoelectric actuator,the dynamic model of the actuator is established,the main factors affecting its performance are studied,new type of drive methods to optimize and improve its performance are proposed,the research on the micro-miniaturization of the structure is carried out,and the control system is developed.In this paper,the influence of the shape of the driving foot,the preload on piezo-stacks,the driving preload and the friction coefficient on the operating state of the stick-slip piezoelectric actuator is studied by combining the experimental test and the finite element simulation.Furthermore,considering multiple factors such as piezoelectric stack,flexible mechanism,mover mass,coupling angle,friction drive,contact deformation,etc.,a general dynamic model of stick-slip piezoelectric drive is established based on the modular idea.The dynamic model is numerically calculated in MATLAB/Simulink,and the influence of parameters such as motion coupling angle,drive signal symmetry,flexible mechanism stiffness,and mover mass on the performance of the drive is analyzed.In order to improve the speed,driving force and positioning accuracy of the stick-slip piezoelectric actuator,the paper first designs a wing-bone-like drive device using the parasitic motion driving method.The test results show that its reciprocating motion error is 4.5 μm,its bidirectional motion speed are 88.68 μm/s and 70.95 μm/s,and its vertical load capacity is 200 g.On this basis,improvements are made by supplementing the preload adjustment function and optimizing the flexible mechanism.After the improvement,the reciprocating motion error of the actuator is reduced to 1.5 μm,the bidirectional motion speed are increased to 1.56 mm/s and 1.05 mm/s,and the vertical load capacity is still 200 g.Since the parasitic motion driving method cannot effectively utilize the performance of the piezo-stacks,the paper proposes two improved driving methods: multi-stack cooperative driving method and stack displacement amplification driving method.The developed cooperative drive actuator has the maximum speed of 151.4 mrad/s and the vertical load capacity of 636.9 g;the displacement-amplified actuator has the open-loop displacement resolution of 0.594 μm,the peak speed of 0.74 mm/s,and the vertical load capacity of 3.6 kg.In order to realize the miniaturization of the actuator,the research on structure simplification and size optimization is carried out in this paper.First of all,on the basis of the displacement-amplified actuator,the structural form of the flexible mechanism is optimized from the series type to the parallel type,and the structural features of the asymmetric stiffness and the parallelogram flexible mechanism are organically integrated,so that the size of the flexible mechanism is reduced from 112 mm ×70 mm × 5 mm to 40 mm × 22 mm × 5 mm,the drive speed is increased to 18.08 mm/s,and the horizontal load capacity is 120 g.In order to further reduce the size of the actuator,a cantilever beam drive foot is designed to replace the drive preload adjustment mechanism,and the displacement amplification function of the flexible mechanism is cancelled,a size optimization method based on dynamic model and genetic algorithm is proposed,and a miniaturized stick-slip piezoelectric actuator is developed,its size is only 27 mm × 25 mm × 20 mm,the maximum speed is 4.1 mm/s,and the horizontal load capacity is 110 g.Based on the miniaturized stick-slip piezoelectric actuator,the research on the driving signal and control method is carried out in this paper.Firstly,the sawtooth wave signal commonly used in stick-slip piezoelectric actuator is optimized,and a waveform optimization method based on the dynamic model is proposed.The optimized sawtooth wave can increase the speed of the actuator by 20.56% and 29.48% under the conditions of 100 Hz and 1000 Hz,respectively.Furthermore,this paper studies the motion control method of the actuator and writes the supporting control software,which realizes the precise control of the driving device,proposes the fuzzy control variable speed method to reduce the displacement overshoot of the actuator,and proposes the fuzzy/PID compound control method in order to suppress the oscillation of the actuator,the steady-state positioning error is less than 10 nm.Finally,two miniaturized stick-slip piezoelectric driving devices are combined into a two-degree-offreedom positioning platform,which is integrated into the nanoindentation test system to achieve precise positioning of the material specimen.The research work of this paper is based on mechanism analysis-improving performancereducing size-control research,and systematically researches on stick-slip piezoelectric actuators from the inside out.Through the establishment of dynamic model,improvement of driving method,reduction of structure size,optimization of driving waveform,development of control system and other research work,the miniaturized actuator can achieve excellent performance in terms of size,speed,driving force and positioning accuracy.The research results of this paper provide an important theoretical and application basis for the stick-slip piezoelectric actuator,and are of great significance for promoting the development of piezoelectric precision drive technology. |
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