Dynamics and control of space robot considering joint friction

It is well known that friction is an inevitable phenomenon existing in almost all mechanical systems including robotic systems. It can affect dynamic characteristics of mechanical systems and even harm accuracy of manual control. In this paper, we have conducted comprehensive study in detail on dynamics and control of a space robot with joint friction. Dynamic equation of the system is established based on Jourdain's velocity variation principle and the single direction recursive construction method. The Coulomb friction model, the Stribeck friction model and the LuGre friction model are adopted to describe the joint friction. Meanwhile, the calculation method for joint friction is discussed in detail, and the relationship between ideal constraint force and Lagrange multipliers is derived. Moreover, an active controller is designed by the nonlinear decoupling method for the trajectory tracking for the system. The validity of the proposed dynamic model is verified by comparison of numerical simulation results and results obtained from the software ADAMS. And then we carry out a series of simulations in order to observe the influence of joint friction on operating a space robot with different friction models. We also study the interaction between the low-speed motion and joint friction in the process of trajectory tracking. (C) 2015 IAA. Published by Elsevier Ltd. All rights reserved.