Maneuvering and Vibrations Control of a Free-Floating Space Robot with Flexible Arms

Abstract

A free-floating space robot with four linkages, two flexible arms and a rigid end-effector that are mounted on a rigid spacecraft; is studied in this paper. The governing equations are derived using Kane’s method. The powerful tools of Kane’s approach in incorporating motion constraints have been applied in the dynamic model. By including the motion constraints in the kinematic and dynamic equations, a two way coupling between the spacecraft motion and manipulator motion is achieved. The assumed mode method is employed to express elastic displacements, except that the associated admissible functions are supplanted by quasicomparison functions. By a perturbation approach, the resulting nonlinear problem is separated into two sets of equations: one for rigid-body maneuvering of the robot and the other for elastic vibrations suppression and rigid-body perturbation control. The kinematic redundancy of the manipulator system is removed by exploiting the conservation of angular momentum law that makes the rigid manipulator system nonholonimic. Nonholonomic constraints, resulted from the nonintegrability of angular momentum, in association with equations obtained from conservation of linear momentum and direct differential kinematics generate a set of ordinary differential equations that govern the motion tracking of the robot. The digitalized linear quadratic regulator (LQR) with prescribed degree of stability is used as the feedback control scheme to suppress vibrations. A numerical example is presented to show the numerical preferences of using Kane’s method in deriving the equations of motion and also the efficacy of the control scheme. Acquiring a zero magnitude for spacecraft attitude control moment approves the free-floating behavior of the space robot in which considerable amount of energy is saved.

Vibration Control of Maneuvering Spacecraft with Flexible Manipulator Using Adaptive Disturbance Rejection Filter and Command Shaping Technology

“…Jing Cui is with Associated Professor of The College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing, China, 101100, tracycuijing21@gmail.com motion planning and corresponding controller design of this problem [2]. Thereinto, command shaping control, which has advantages of simplification and without use of added sensors, or the need to redesign of the mechanical hardware, has enabled engineers to harness the benefits on spacecraft, flexible robotics arms, and so on [3].…”

“…Some researches have been studied in this classical field with a variety of feedforward and feedback control methods including linear quadratic regulator [2], H in f algorithm [7], Dynamic inversion and μ-synthesis method [8] and so on. In the present paper, disturbance-rejection filters are studied further to explicitly employ the periodic-disturbance frequency into a filter embedded in the feedback control loop.…”

Space Robotics

“…Indeed, large-workspace manipulators such as the SRMS on the Space Shuttle and the SSRMS/JEMRMS on the International Space Station are known to exhibit structural vibrations due to the specific design constraints imposed mainly on their mass [18]. Modeling a robot as flexible-link [19] and/or flexible-joint [20] manipulators and employing the respective methods of control is crucial for minimizing the vibrations [21][22][23][24].…”

Dynamics and tracking control for a free-flying space robot with rigid-flexible links

“…With the help of a virtual space vehicle, a tip trajectory control scheme of a two arm rigid-flexible space robot has been presented [6]. In [7], a free-floating space robot with a rigid spacecraft, four linkages, two flexible arms and a rigid end-effector has been studied. In [8], a trajectory tracking control of the free floating space robot with rigid-flexible manipulators is discussed.…”