2 research outputs found
Adaptive Zero Reaction Motion Control for Free-Floating Space Manipulators
This paper investigates adaptive zero reaction motion control for
free-floating space manipulators with uncertain kinematics and dynamics. The
challenge in deriving the adaptive reaction null-space (RNS) based control
scheme is that it is difficult to obtain a linear expression, which is the
basis of the adaptive control. The main contribution of this paper is that we
skillfully obtain such a linear expression, based on which, an adaptive version
of the RNS-based controller (referred to as the adaptive zero reaction motion
controller in the sequel) is developed at the velocity level, taking into
account both the kinematic and dynamic uncertainties. It is shown that the
proposed controller achieves both the spacecraft attitude regulation and
end-effector trajectory tracking. The performance of the proposed adaptive
controller is shown by numerical simulations with a planar 3-DOF
(degree-of-freedom) space manipulator.Comment: 17 pages, 9 figures, revised for more rigorously presenting the proof
and for improving the presentation, highlighting the contribution, and
correcting some typos based on the reviewers' and AE's comments from IEEE
Transactions on Aerospace and Electronic System
Dynamic Modularity Approach to Adaptive Inner/Outer Loop Control of Robotic Systems
Modern applications of robotics typically involve a robot control system with
an inner PI (proportional-integral) or PID (proportional-integral-derivative)
control loop and an outer user-specified control loop. The existing outer loop
controllers, however, do not take into consideration the dynamic effects of
robots and their effectiveness relies on the ad hoc assumption that the inner
PI or PID control loop is fast enough, and other torque-based control
algorithms cannot be implemented in robotics with closed architecture. This
paper investigates the adaptive control of robotic systems with an inner/outer
loop structure, taking into full account the effects of the dynamics and the
system uncertainties, and both the task-space control and joint-space control
are considered. We propose a dynamic modularity approach to resolve this issue,
and a class of adaptive outer loop control schemes is proposed and their role
is to dynamically generate the joint velocity (or position) command for the
low-level joint servoing loop. Without relying on the ad hoc assumption that
the joint servoing is fast enough or the modification of the low-level joint
controller structure, we rigorously show that the proposed outer loop
controllers can ensure the stability and convergence of the closed-loop system.
We also propose the outer loop versions of several standard joint-space
direct/composite adaptive controllers for rigid or flexible-joint robots, and a
promising conclusion may be that most torque-based adaptive controllers for
robots can be designed to fit the inner/outer loop structure by using the new
definition of the joint velocity (or position) command. Simulation results are
provided to show the performance of various adaptive outer loop controllers,
using a three-DOF (degree-of-freedom) manipulator, and experiment results using
the UR10 robotic system are also presented.Comment: This version is mainly for including the experimental result