Control of Ionic Polymer-Metal Composites for Active Catheter Systems via Linear Parameter-Varying Approach

Abstract

The ionic polymer metal composite (IPMC) is one type of electro-active material with the characteristics of low electric driving potential, large deformation, and aquatic manipulation. It is highly attractive to biomedical applications as an actuator or a sensor. The main purpose of this study is to explore closed-loop control schemes to an IPMC actuator for active catheter systems. In this article, by measuring frequency responses of a 20 mm × 5 mm × 200 μm IPMC, an empirical model is developed and used for closed-loop control. From previous work, two resonant peaks ranged at 3—4 Hz and 18—20 Hz are found in the Bode diagram for the frequency responses of IPMC. Based on this fact, a 4th order transfer function was modeled to describe the system. A parameter-dependent transfer function was then created to describe the bending dynamics of IPMC in response to different driving voltages. As IPMC actuators are nonlinear and slow time-varying systems, the controller was designed using linear parameter varying (LPV) approach. Compared with the conventional closed-loop PID control, the maximum overshoot and steady-state error was decreased to 2% and 1.32%, respectively. The rise time was about 0.186 s, which is within the limit for many biomedical applications.