Two link macro manipulator carrying a two-armed micro manipulator with a "satellite"

Macro/Micro Manipulators

Long reach space manipulators, such as the Space Shuttle Remote Manipulator System (RMS), must be made as lightweight as possible. A lightweight manipulator will have flexibility both in the drive system and in the structure of the manipulator. This flexibility limits the speed and dexterity that can be achieved at the end-point of a manipulator. A much smaller manipulator can be faster and more rigid, at the expense of workspace. Thus the combination of a small "micro" manipulator carried by a large "macro" manipulator creates a robot that can be dexterous over a large area. A planned space macro/micro system is the Space Station manipulator, the SSRMS/SPDM. Another example of a macro/micro manipulator is the human arm/hand.

Experimental System

The experimental system in the lab consists of a planar manipulator operating in a two dimensional space-like environment. The end-point of the macro arm floats on an air bearing over a large, flat granite table. The macro part of the manipulator features two 1.5m long links, each with built in joint flexibility. The two micro arms are similar to the ones on the free-flying space robots. Also shown is a small free floating object that the robot can catch and manipulate. An overhead vision system senses the end-point position of the arms as well as the position of the object.

Research

The goal of the research is to remove the human from the low-level control of moving each arm. Instead, the human should give tasks for the robot to complete autonomously. It is desired to have a low-level control loop that can accurately control the end-point of each micro arm. While much research has been done on controlling redundant robotic systems, many of these techniques break down when there is flexibility between the motor and the robot. Current research is on using techniques such as backstepping to account for the joint flexibility in combination with rigid robot redundancy management schemes.

 

Micro manipulator grabbing the object 

Last modified Mon, 1 Nov, 2010 at 19:34