The Research On An Inertial Piezoelectric Actuator For A Microminiature Pipe Robot

Micro robotics is a forward research of interdisciplinary knowledge and an advanced electro-mechanical system, which developed rapidly on the basis of superfine machining techniques and micro-electro-mechanical products. It's a development trend of micro robots that micro actuator, micro sensor, micro energy source and control system are integrated highly. Study of micro actuator is always the core of micromechanics development, and indicates the country's micromechanics development level in a way.The research is sponsored by the National Natural Science Foundation of China under Grant No. 69774020 and 50475152. Interdisciplinary knowledge, such as Physics of Crystals, Piezoelectricity, Mechanics of Material and Thermodynamics is utilized to design and manufacture an inertial piezoelectric actuator for in-pipe micro robot. The actuator is composed of a body and four elastic legs. The body is a mass rod. Each leg is a composite piezoelectric bimorph cantilever beam. When the actuator is driven by an asymmetric waveform voltage, such as saw-toothed waveform, it will move according to the dynamic relationship between the maximum static friction force and the inertial force. Its structure is simple and unique. The driving method is handy. It can flexibly move forward and backward.The constituent equations of a composite piezoelectric bimorph cantilever beam under both applied voltage and external force are deducted, which include constituent equations of a typical piezoelectric bimorph and a bimorph with an interlayer. The relations between the tip deflection of the beam and the thickness (or elastic modulus) of the interlayer are analyzed by the numerical calculation while the external force (or applied voltage) is changed. The effect of the interlayer parameters on the tip deflection is verified by the experiments and theories, proving the validity of the equation. The establishment of the equations further perfects the theory of bimorphs.After the effect of the interlayer on the actuator's performance is considered fully, a dynamic model of the actuator is established, analyzing the relationship between the locomotive states and system parameters. A GUI on relation between the actuator's kinematic performance and system parameters is obtained, which can simulate the kinematic state of the actuator under arbitrary sizes, performance parameters, environment parameters and voltage parameters and get the relation curve between the actuator velocity and every parameter separately. The parameters of actuator are optimized by a new arithmetic which is constructed by introducing fuzzy rules in particle swarm optimization (PSO). Effects of population size, initial inertia weight, acceleration constants, maximum particle velocity and maximum number of iterations on PSO are studied in detail. It is proved by calculation that fuzzy rules are better than the way of making the inertia weight fixing or descending linearly in adjusting the inertia weight on line. Compared with the other optimization arithmetic, it has merits of simpler concept, less calculation, and realization more easily.Two different model actuators are made. An electrical source consisting of high voltage amplifier 3583 is designed for the actuator. Supplying deflection voltage to 3583, an adjustable direct current high voltage power supply is designed. An experiment system of the actuator is built up. The relations of the velocity with driving voltage, driving frequency and load mass are tested. The technology performance indexes of the actuator are obtained by the testing. The experimental data is fitted to polynomial by least squares optimization. The error is analyzed quantitatively and qualitatively.