Electromechanical Performance Modeling Of Artificial Muscle (IPMC) And Its Applications As Actuator

Ionic polymer-metal composite (IPMC) is a new type of smart materials, which belongs to one class of electroactive polymers, and it can generate large deformation within voltage. The merits of IPMC are low driving voltage, large deformation, noiselessness, big thrust-weight ratio and flexibility, so it is extremely suitable for micro electronic mechanical system (MEMS); now it becomes one of central research issues as a small actuator or sensor all over the world. Further, to increase the transmission efficiency, simplify the drive mechanism, reduce the structure size and improve system reliability, the research goals are making IPMC materials becoming smaller, more fine, smarter, more flexible, and more intelligence.Although IPMC has above advantages, the electrical response properties are of instability and its corresponding drive mechanism is imperfect, inducing that most of its applications remain in the laboratory testing stage. For improving the performance of IPMC actuator, this dissertation will focus on the electrical response characteristics, covering IPMC fabrication, modification, modeling, experiments and applications. The main research contents are as follows:(1) IPMC membrane with platinum was fabricated; in order to obtain its water swelling properties, deformation characteristics under electrical stimulation, and mechanical output characteristics, all of them are measured. Further, the grid-based IPMC film with platinum was fabricated for overcoming the relaxation phenomenon of general IPMC material, the former can hold deformation at least 5 minutes without relaxation (general IPMC film occurred relaxation within 30 seconds). Therefore, this new type IPMC can improve the stability of IPMC electrical response.(2) It was found that within voltage excitation the general IPMC strips with platinum had nonlinear large deformation in its root. Even in the absence of electrical power in its free part, its tip deformation could also achieve large deformation just resulting from the root electrical response deformation. This dissertation concentrates on this kind of electrical excitation model for simulating and explaining the above phenomenon and analyzing the internal physical changes of IPMC. Based on Nemat-Nasser coupling model, energy conservation law is utilized to derive an improved simulation model by considering electrical, chemical, mechanical and fluid fields together. The results showed a large improvement for simulation accuracy up to 13% (original Nemat-Nasser model's error for this kind of IPMC is 72%).(3) As to three IPMC membranes with different performance, their electrical response simulation had been completed. Both in root and free parts of IPMC strip, the changing principle of the water uptake, the internal stress and strain, Young's modulus and other key performance parameters had been calculated and simulated, and the results showed strong nonlinear relationships; finally the nonlinear relationship between the IPMC tip displacement response and time was solved. The experimental and simulation results are in good agreement, and so it can verify that the above model is reasonable, reliable and validity.(4) Three performance parameters (deformation, stress and strain) nonlinear changes of IPMC strips were found in the start-up state, and their simulation results were carried out. In the start-up state, the relationships between these three performance parameters and their excitation voltages were approximately exponential increase trends; in stable state the stress and strain followed the exponential increase trend, but the deformation became an approximate linear increasing relationship. Then, by designing the test of IPMC electrical actuation, it can be testified that the reason leading to the above phenomena are charging effects from the IPMC material itself.(5) Three IPMC grippers with simple structures were designed and fabricated. The advantages of them are low energy consumption, simple structure, flexible, quiet, small size, big thrust-weight ratio, etc., and especially for the parts with high accuracy surface the IPMC materials could not damage the surface finish.This research activity is funded by National Natural Science Foundation of China General Programs (Grant No.50407004 and Grant No.50875123).