Design of flexonic mobile node using 3D compliant beam for smooth manipulation and structural obstacle avoidance

Motivated by the needs to develop dexterous flexonic mobile node (FMN) for structural health monitoring where obstacle avoidance is among the most challenging tasks, this paper presents a novel FMN design for navigating on iron-based structures. Unlike most existing magnetic wheel designs, the FMN uses fixed-magnet configuration contributing to smooth motion, self-maintained orientation and automatic negotiation of concave corners. Taking into account of several stringent considerations (including tight dimension, efficient attachment and manipulation flexibility) to facilitate avoidance of structural obstacles in tight space, a prototype FMN incorporating a compliant beam (that results in more DOFs than designs with multiple links and pin/ball joints), along with a 3-step strategy for negotiating a convex corner, has been developed. Although controlling a continuous deforming beam is challenging given limited number of actuators, both simulation and experimental results confirm a simple input/output relation between the rear axle displacement and front axle rotation, which is anticipated to facilitate control implementation of FMN for obstacle avoidance.