Ultra-lightweight anthropomorphic dual-arm rolling robot for dexterous manipulation tasks on linear infrastructures: A self-stabilizing system

Abstract

This paper proposes the application of a very low weight (3.2 kg) anthropomorphic dual-arm system capable of rolling along linear infrastructures such as power lines to perform dexterous and bimanual manipulation tasks like the installation of clip-type bird flight diverters or conduct contact-based inspection operations on pipelines to detect corrosion or leaks. The kinematic configuration of the arms, with three joints at the shoulder and one at the elbow, allows the natural replication of the human movements to conduct these tasks, exploiting also the kinematic redundancy of the shoulder to maintain the equilibrium while perching on the line. The dynamic model of the system is derived to design a self-stabilizing controller that maintains the base of the arms at an equilibrium point. The state-dependent Riccati equation (SDRE) controller is chosen for this purpose since the system is under-actuated and the contribution of the control gain (with nonlinear optimal structure) on all states is critical. The SDRE is a nonlinear optimal controller that extends the margins of stability in comparison with linear ones. Simulation results show that the SDRE performs the regulation to the equilibrium point successfully and evidence better performance with respect to a linear quadratic regulator (LQR). The system is validated in an outdoor testbed consisting of a power line mockup, presenting experimental results to evaluate the SDRE and LQR controllers, demonstrating also the autonomous installation of clip-type bird flight diverters and the aerial deployment using a multirotor platform.