Gibbon-inspired Robust Asymmetric Brachiation along an Upward Slope

Abstract

This paper investigates the robust control of an underactuated brachiating robot. The control schemes are motivated by the applications that require robots to move through lattice structures, such as the inspection and maintenance of power transmission lines and towers. Inspired by the pendulum-like movements that enable gibbons' arboreal locomotion, the controllers are designed to synchronize the brachiator with a virtual oscillator. Two controllers are proposed: a model-dependent feedback linearization scheme and a sliding-mode scheme that is independent of the system model. These controllers are tasked to drive a robotic brachiator in two cases with different geometries: symmetric geometry, where its links have equal lengths, and asymmetric geometry, where its links have different lengths. The numerical results illustrate that the proposed schemes are robust to the arbitrary initial conditions of the brachiator, the motor torque limitation at the elbow joint, as well as the geometry of the brachiator. Furthermore, they are able to perform successful fast swing-up and dynamic brachiating along a structural member with an upward slope in a unified control framework for both symmetric and asymmetric geometries.