Wheel-Based Climbing Robot: Modeling and Control

Abstract

This paper addresses the kinematics modeling and control of a novel nonholonomic wheel-based pole climbing robot called UT-PCR. This robot belongs to a challenging and less-studied class of wheel-based mobile robots in which the relative position of the wheels changes in a complex manner and the robot is constrained to maneuver on a closed geometric surface. The problem is formulated in terms of the kinematic model of the robot, which is derived using non-holonomic constraints imposed by the wheels on the motion. This model is an underactuated driftless nonlinear state space (control system) which is linear in its inputs. Feasibility of complex maneuvering is then proved by an analysis of controllability for this nonlinear system. It is shown that three orientations of the robot cannot be controlled independently. Therefore, three basic movements are introduced as the fundamental elements of the kinematic control strategy and stable controllers are designed to create those basic movements. Simulation and experimental results are provided to show the applicability of the proposed control system.