Multi-level Fuzzy-QFT Control of Conjugated Polymer Actuators

Conjugated polymer actuators can be employed to achieve micro and nano scale precision, and have wide range of applications including biomimetic robots and biomedical devices. In comparison to robotic joints, they do not have friction or backlash, but on the other hand, they have complicated electro-chemo-mechanical dynamics which makes modeling and control of the actuator really difficult. Besides the positive characteristics of these actuators, they have some disadvantages such as creep, hysteresis, highly uncertain and time-varying dynamic. This paper consists of two major parts. In the first part the Takagi–Sugeno (T–S) Fuzzy model is used to represent the uncertain dynamic of the actuator. The resulted Fuzzy model will be validated using existing experimental data. In the second part a multi-level controlling approach will be used to control the highly uncertain dynamic of conjugated polymer actuators. The firstlevel controller is a fuzzy controller and the second-level controller is a QFT controller. The fuzzy controller is designed to perform the main control action, while the QFT controller is used as a safeguard. The obtained results show that the designed controller can achieve good performance despite the existence of uncertain actuator dynamics.