Polymeric Gel Actuator And Its Application To Robots

It is very important to develop novel actuators for robots, especially for micro-robots. As one of the smart material actuators, polymeric gel converts chemical energy into mechanical energy directly, from this aspect, it is the most bio-mimetic actuator for its extreme similarity to humans' or animals' muscles. Presented in this dissertation is a polymeric gel actuator and its application to robots, including 4 aspects as follows.Firstly, on the aspect of PAN (poly-acrylonitrile) gel muscle's preparation: there are two steps in PAN's preparation-cross-linking (annealing) and saponification. Making the gel's length contraction ratio(LCR) the maximum, the ideal preparation condition is got. In order to build dynamic model, dynamic parameters including storage moduli E', loss moduli E" and loss shift tan were tested, the relation between E', E", and stimulating vibration frequency was obtained, gel muscle's E' and E" under different pH at low frequencies were concluded, and the data were fitted with polynomial. Through lots of trial and some theoretical analysis, a different saponification time from the former was chosen, in order to make the LCR largest when loaded. Output mechanical energy is a significant target for gel muscle actuator, from the view of making output mechanical energy the largest, the best load is obtained through experiments, while the concentration of acids and alkalis is 2M and 1M respectively. Then the graph depicting the relation between pH and gel's LCR is got, which can be implemented to control gel actuator's position and velocity by controlling pH value. Combined with microscopic mechanism of gel's volume change, apreliminary explanation was given then.Secondly, on the aspect of microscopic mechanism of gel's volume change and macroscopic modeling: according to Flory's gel swelling theory, an expression to describe gel's swelling was deduced from the angle of chemical potential and osmotic pressure, which accounts for PAN's expansion and shrink behavior qualitatively and is accordant with the observed phenomenon. Expression of volumetric strain and pH value about ionic polymeric gel was got, as well as the corresponding graph. They illustrate the fact that PAN gel contracts in acids and swells in alkalis. By adjusting the polymer solution's ionic strength, a kind of gel whose volumetric strain and solution's pH value are monotonic can be achieved, which will improve PAN's controlled performance greatly. Assuming a capillary model, the relation between EMC (Electro- Mechano-Chemical) gel's weight and time during the process of swelling was gained. With the theory of macro-deformation, the gel's bending curvature is also obtained, either by the deformation mechanism of pH value or electrical field. Because the stress of cross-linked polymer will not relax to zero from the macroscopic view, three elements visco-elastic model can be applied to simulate PAN gel muscle.Then, on the aspect of gel muscle's application to robots: according to bio-mimetics, two kinds of simple parallel and gel muscle driven wrist-like apparatus were designed, which enrich the variety of parallel robots, and can be used to further study on configuration optimization. Till now, forward position kinematics of general Stewart platform has not been solved analytically, here analytic solution of a kind of simple serial-parallel apparatus was obtained through some simplification, which is available for real time control of serial-parallel robots. The wrist-like apparatus's dynamics was analyzed with Lagrange method, a whole of closed dynamic equations without restriction force wasderived, combined with gel muscle's dynamic model, a dynamic model of the whole system that can be used for real-time control was concluded. Intel 8031 based control system was employed to fulfill the irrigation of acids and alkalis automatically, taking place of handwork, and preparing for the future task of position and velocity servo-system. Combining gel actuator with industrial application, an industry-promising in-pipe mobil...