Speed control mechanism for IPMC based biomimetic flapping thruster

The increasing need for real preliminary information verification in small space for any underwater operations involving search and rescue, archaeological exploration and oceanographic studies had inspired the development of biomimetic underwater flapping thruster using Ionic Polymer Metal Composite (IPMC) smart actuator. However, one of the problems with this kind of thruster is the inconsistent and uncontrollable thrust generation due to no proposed control mechanism. Therefore, the main objective of this paper is to equip this biomimetic flapping thruster with speed control mechanism to ensure the motion of this thruster is following the pre-determined speed. The IPMC actuator was utilized as the thruster's caudal fin to move the thruster body at certain speed. Meanwhile, an Inertial Measurement Unit (IMU) device was used as the speed and orientation sensor for open loop and closed loop control experiments. Open loop results prove that the generated thruster instantaneous speed increases with the increases of amplitude of voltage to IPMC. Based on this information, a closed loop control system was developed, and its performance was verified. By controlling the voltage amplitude, the closed loop control system managed to control thruster's instantaneous speed around the 1.5 cm/s setpoint. In conclusion, the speed of IPMC based flapping thruster can be effectively controlled by using IMU device as a speed feedback. The knowledge is critical in providing other IPMC based biomimetic robot researcher a solution for controlling the thrust generation.