| Ultra-precision positioning technology in micro/nano scale has become a key technology in many high-tech fields such as ultra-precision manufacture and measurement, precision optical engineering, modern medical, aerospace science. However, traditional actuators can not fulfil the high-precision requirements in many high-tech fields. Piezoelectric actuator is one kind of new actuators, it has its own advantages such as high-precision resolution, high response speed and compact size, so piezoelectric actuators have been used in a wide range of high-precision positioning devices.Step-type piezoelectric actuators can overcome the piezoelectric materials’ disadvantage in small working stroke, thus many researchers have paid much attention on them. This paper presents some high-precision piezoelectric actuators with large working stroke based on inchworm principle and parasitic-inertia principle. These designed actuators can overcome the existing piezoelectric actuators’ shortcomings in low resolution, small output force and complex structure. This paper gives a detailed analysis on the moving principles and the strcutures, and also presents the dynamic models for inchworm-type piezoelectric actuators and parasitic-interia-type piezoelectric actuators. Experimental results show that these designed piezoelectric actuators can achieve large working stroke and high resolution at the same time, and this paper may have some meaning for the development of piezoelectric actuators.The inchworm-type piezoelectric actuator is inspired by the movement of the real inchworm in nature. This paper uses multiple-layer flexure hinges and piezoelectric stacks to design an inchworm-type rotary piezoelectric actuator, and when the clamping units, driving units and preload units work together, it can produce large-stroke rotary motion with high resolution. This paper presents the detailed working principle and structure design of it, also gives the calculation of the stress and resonant models. To investigate the working performances, an experiment system has been established, and the testing results show that the rotary resolution is 4.95 μrad, the maximum rotary speed is 6508.5 μrad/s and the maximum torque is 93.1 N·mm.The first inchworm-type piezoelectric actuator has a complex structure, and it is difficult to manufacture and control. Based on the first inchworm-type piezoelectric rotary actuator, this paper also proposed a simplified inchworm-type piezoelectric actuator. The proposed triangle-type flexure hinge can achieve the clamping motion and driving motion at the same time, thus the inchworm moving principle and the control method can be simplified. The testing results indicate that the rotary resolution is about 25 μrad, the maximum rotary speed and output torque are 71300 μrad/s and 19.6 N·m respectively.What’s more, this paper also presents the dynamic model of the dsigned inchworm-type piezoelectric rotary actuators based on the Lu Gre friction. The results from the Matlab/Simulink show that the built dynamic has a good coordination with the experiments.To achieve large working stroke and high resolution within a compact size, we use the simpler motion principle, parasitic-inertia type, to propose the parasitic-inertia type piezoelectric actuator. Different calculation method have been compared to analyze the amplification ratio of the used bridge-type flexure hinge. The parasitic motion of the bridge-type flexure hinge can make one piezoelectric actuator produce two motions(driving motion and preloading motion), thus the performance of the existing inertia piezoelectric actuators can be improved. Moreover, to improve the resolution of step-type actuators, this paper proposed the dual-servo PID control method. One piezoelectric stack can achieve the coarse motion and fine motion by using this control method, thus the resolution of step-type piezoelectric actuators can be highly improved. The experimental results show that open-loop rotary resolution of the designed parasitic-inertia type piezoelectric actuator is 6.92 μrad; the highest moving speed is about 32000 μrad/s; the closed-loop resolution using the dual-servo PID control method is about 1.54 μrad which is about 250 times higher than that without the dual-servo PID control method.Howerver, the output force of the designed parasitic-inertia type actuator is still small, so we proposed other two improved parasitic-inertia actuators. One improved parasitic-inertia type actuator uses two piezoelectric stacks which are placed vitically to get higher moving speed and larger output force, the testing results show that its resolution is about 0.41 μm, the maximum moving speed is 0.735 mm/s and the output force is 0.294 N. The other improved parasitic-inertia actuator utilizes a parallelogram-type flexure hinge to simplify the whole structure and improve the working performance, the experimental results show that the open-loop resolution is 0.04 μm, the maximum moving speed is 14.25 mm/s, the maximum output force is about 3.43 N. The dynamic model of the proposed parasitic-inertia type piezoelectric actuator based on Lu Gre friction has been given, and Matlab/Simulink is used to calculate the dynamic model.Inchworm-type piezoelectric actuators are situable for the applications which are strict in output force, but not in moving speed. Parasitic-inertia type actuators are fit for some appliciations which have the high requirements for moving speed and compact size. Moreover, we also proposed a piezoelectric-driven micro-manipulation system which is based on the designed piezoelectric actuators. A piezo-driven micro grapper is manufactured to grip the small objects. The proposed nano-manipulation grapper can make some real-time maniplutation for some small objects when works tegother with microscope and small force-back units.This paper mainly focuses on the research about large-stroke piezoelectric actuators with high resolution, and it may have some meaning for the development of ultra-precision nanopositioning systems. |
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