Abstract
This study aims to examine landing posture control for a generalized twin-body system using methods of input-output linearization and computed torque. The considered system mimics the mechanism of a certain popular cellular phone that is composed of two rigid links and an active joint that not only connects the two links but also offers torques about three orthogonal axes. A standard modeling procedure for robotic dynamics is employed to capture the twin-body dynamics in terms of 312 Euler angles on the basis of the Newton-Euler formulation. Herein, the posture components, i.e., the included angle, the tilt angle, and the first landing body, are employed to represent the landing posture that is particularly designed to prevent the fragile areas of the system from being damaged. Since the three posture components are nonlinear functions of state variables, the standard control strategy cannot be applied. In order to resolve this difficulty, the three posture components are transformed into three control outputs, which are linear functions of state variables. However, the system reveals a nonlinear control problem, and the method of input-output linearization is used to cancel the nonlinear terms. The computed torque method is then utilized to determine the input torques. Finally, the feasibility of the proposed landing posture control is confirmed via MATLAB simulations. This study successfully implemented a standard control strategy to realize landing posture control by establishing transformations from real landing posture components to simulated control outputs, and the controllable regions were defined completely. © 2009 IEEE.