Active gravity compensation test bed for a six-DOF free-flying robot
A novel active gravity compensation concept is proposed to simulate space on-orbit microgravity environments for free-flying robots on ground. Here, robots are suspended by active-controlled motion path tracking mechanisms through wires to compensate for gravitational forces. Based on the concept, an experimental test bed was designed and fabricated in laboratory to study on-ground kinematic and dynamic behaviors of a free-flying robot. The experimental fabrication contains an active horizontal motion tracking mechanism composed of primary and secondary active rotating arms. An multi-objective optimization method calculating the tension of the wires to minimize torques on robot joints is approved. The tension of the suspension wires is obtained through passive counterweights using pulley mechanisms. The kinematics and dynamics of a 6-DOF free-flying manipulator were calculated in MATLAB and simulated in MSC Adams under three working conditions: zero-gravity, gravity compensation and gravity. The lowest ratio of the torque compensation reached 80%. Agreements between numerical analyses and simulation results confirm the ability of this gravity compensation concept to simulate the kinematic and dynamic behaviors of free-flying manipulator in space.
Microgravity science and applications projects and payloads
An overview of work conducted by the Microgravity Science and Applications Division of NASA is presented. The goals of the program are the development and implementation of a reduced-gravity research, science and applications program, exploitation of space for human benefits, and the application of reduced gravity research for the development of advanced technologies. Space research of fluid dynamics and mass transport phenomena is discussed and the facilities available for reduced gravity experiments are presented. A program for improving communication with the science and applications communities and the potential use of the Space Station for microgravity research are also examined.
Active Vibration Control for Flexible Space Environment Use Manipulators
A new dynamic control system for flexible space environment use manipulators has been developed from the practical viewpoint. The key concept in the proposed method is that the local position and torque PD feedback loop at each joint should be used for position and structural vibration control. First, the authors derived manipulator dynamics, and then feedback control was developed, using an appropriate potential function. Secondly, an experimental setup using an air suspended SCARA flexible manipulator is described. The effectiveness of this method has been verified by experimental results, adapting it to automatic payload handling.