Modeling and Control of a Flexible Ionic Polymer Metal Composite(IPMC) Actuator for Underwater Propulsion

MODELING AND CONTROL OF A FLEXIBLE IONIC POLYMER METAL COMPOSITE(IPMC) ACTUATOR FOR UNDERWATER PROPULSION by Shivakanth Gutta Woosoon Yim, Examination Committee Chair Professor of Mechanical Engineering University of Nevada, Las Vegas The goal of this research is to model and control the underwater vehicle propelled by IPMC actuator. IPMC consists of an ionic membrane sandwiched between two metallic electrodes. When an external voltage is applied, IPMC undergoes large deformation due to transport of ions. Due to its ability to work in aqueous environments, it can be used for developing small scale underwater vehicles. First, Finite element approach is used to describe the dynamics of the both single and segmented IPMC actuator. In the approach presented, each element is attached with a local coordinate system that undergoes rigid body motion along with the element and the deformation of the element is expressed in local coordinate frame. This large deflection model is combines with Clumped RC model to model the dynamics of the IPMC. iii Next, hydrodynamic model for the IPMC driven vehicle is developed. Frictional resistive forces are considered for modeling the interaction with water. The hydrodynamic coefficients are identified using FLUENT CFD analysis. The developed hydrodynamic model is validated using the experimental data. An autonomous IPMC propelled vehicle is developed to overcome the limited applications tethered vehicle developed earlier. In this research, two kinds of control algorithms based on system identification are developed. A PI controller is designed using simulation data and implemented for controlling speed and orientation of the vehicle. Using the identified linear model, a decoupling control algorithm is developed to eliminate the interactions in tracking speed and orientation (heading angle) of the vehicle. The developed algorithm implemented on original non-linear plant. A path planning algorithm is presented to control the trajectory of the vehicle in the presence of obstacles. Obstacles are approximated by polygonal shapes that approximate their actual dimensions and the vehicle is approximated by a rectangle that encloses the largest deformation of the oscillating IPMC actuator. To simplify the problem of collision detection, vehicle is shrunk to a line while obstacles are expanded by a half width of the rectangle representing the vehicle. The path generated by the algorithm is discretized with respect to time and controlled simultaneously for the orientation angle and speed of the vehicle. A model reference adaptive controller (MRAC) is designed for underwater vehicle propelled by the Ionic polymer metal composite (IPMC) actuator. Trajectories of iv the vehicle are controlled by simultaneously controlling the bias and amplitude of the sinusoidal voltage applied to the IPMC actuator attached at the rear end of the vehicle. Using Lyapunov stability theory and factorization of the high frequency gain matrix, an adaptive output feedback control is designed for trajectory control of a heading angle and a speed of the vehicle. In the proposed approach, SDU (Square Diagonal and Upper triangular matrix) decomposition of the high frequency gain (HFG) matrix is used. Only signs of the leading principle minors of the HFG matrix are assumed to be known. Simulations results are presented to show that precise trajectory control of the heading and speed is achieved in spite of the coupling between controlled variables.