Adaptive control of ionic polymer-metal composite in air and under water using a modified direct self-tuning regulator embedded with integral action

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Abstract

Due to its large deformation response to a low voltage, ionic polymer-metal composite (IPMC) is a highly attractive actuator for many applications in air or under water. However, the dynamic characteristics of IPMC are nonlinear and vary with time, especially in water actuations. In this study, a modified direct self-tuning regulator (DSTR) with integral action was designed to control the tip-displacement of the IPMC, which is a non-minimum phase system to serve in air and underwater applications. The modified DSTR consisted of a pole-placement controller embedded with integral action, a reference model, and a self-tuning mechanism. The reference model specified the dynamic characteristic of the closed-loop IPMC system, and the controller parameters were automatically adjusted by the self-tuning mechanism to minimize the tracking error from the comparison between the response and the reference model output. The integral action may circumvent low-frequency distortions such as the back-relaxation phenomenon. Also, the DSTR may easily control the non-minimum phase system of the IPMC by tuning a delay factor in the reference model. The DSTR was implemented to control an IPMC (0.2mm × 5mm × 35mm) actuated in air and under water, and the tracking performances were compared with a proportional-integral-derivative controller (PID). In contrast with the PID, the parameters of which were determined by the Ziegler-Nichols rule and produced large root-mean-squared tracking errors, the DSTR yielded good tracking performances for actuations both in air and under water from 0.01 to 1Hz. Through control of the modified DSTR, IPMC may have a wide range of applications in the future.

Original languageEnglish
Article number105016
JournalSmart Materials and Structures
Volume20
Issue number10
DOIs
Publication statusPublished - 2011 Oct 1

All Science Journal Classification (ASJC) codes

  • Signal Processing
  • Civil and Structural Engineering
  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Electrical and Electronic Engineering

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