DESIGN OF A COMPLIANT BASED BIOMIMETIC PLANAR LOCOMOTIVE MECHANISM

This paper presents the design, development, modeling and control of a biomimetic multi degree of freedom compliant locomotive mechanism that can follow a prescribed trajectory. The research objective of this study is the design of a high mobility and flexible planar locomotive mechanism incorporating large deflecting compliant hinges. The actuation is realized using servo motors. Mechanism is consisted of five sliding carts, rail, 3D-printed supplementary pieces to house motors and pins. Carts are connected by monolithically designed two arm links joined by a large deflecting flexure. Four servo motors are mounted on the driven carts. Since sliding carts are identical, forward motion is achieved by changing the friction of carts through the connecting pins. Dynamical model is created in Matlab Simulink using Euler's laws of motion principle, pseudo rigid body modeling (PRBM), vector closure-loop equations and kinematic constraints. To robustly control the position of the mechanism, first its nonlinear dynamics replaced with a family of linear time invariant systems which have parameter uncertainty. Then a robust controller is designed based on the Quantitative Feedback Theory (QFT) for the desired robust tracking and stability bounds. QFT is one of the most powerful robust control techniques which can take into account both phase and magnitude information of the system and enables the designer to minimize the cost of feedback by clearly observing the design constraints through robust performance bounds. Finally, the performance of the designed controller is validated though nonlinear simulations using the nonlinear dynamics of the mechanism. It has been shown that the mechanism can consistently track the desired inputs both in frequency and time domains.