The next major space activity is seen as the establishment of permanent, ultimately manned, orbiting space stations in low Earth orbit. The concept requires both orbiter based and platform based RMS. Space construction will require erection, deployment and assembly operations. This needs manipulators to possess the ability to accomplish such tasks as • handling and positioning raw and preformed material, • the alighment of structural elements during assembly, • making electrical and fluid connections, • deploying expandable structures. It is expected that the now space proven end effector will be an ideal interface for the on-orbit changeout of a variety of special tools to give the arm the required versatility. Electrical power and data can be provided via the grapple fixture interface. It is envisaged that handling tools could take the form of a three fingered claw to accommodate most shapes up to 0.3 m in diameter. In this concept tapered fingers permit the handling of small objects. Conceptually, parallel jaws could be devised for general purpose work, drogue and cone for internal surfaces and other task specific mechanisms. Assembly and servicing tools are likely to be variations of the UST theme, where a common drive system can provide a multiplicity of functions by work module changeout. With the broad spectrum of specialized tasks to be performed it is reasonable to predict that several manipulator types would be needed. Tasks identified to date show the need for • large arms over 50 m long for the gross placement of large volume, large mass payloads and material transfer and handling, • shuttle RMS arm for general purpose use and satellite manipulation, • small 3 to 10 m arms for precise dextrous or high torque/force application. Space station studies have also identified the need for a seven degree-of-freedom mobile manipulator, possibly with work station attached. Control is envisaged as being from a crew module or from the work station itself. As well, small manipulators could be mounted to work stations, on the end of larger arms, or onto other craft. The fundamental question of manipulator design most often concerns how best to implement control functions. The correct symbiosis of man and machine is achieved only when the command, performance feedback, health and status data transfer between human and machine is fast enough and appropriately formatted in both directions to provide a workable level of control for all routine and emergency situations. To achieve the appropriate control for these advance space applications requires machines to sense tactile, visual, and audio stimuli. However, it should be emphasized that the sensory feedback must act as integral elements in the control system and not be treated as system attachments. The inherent flexibility of large space structures also imposes a requirement for sensory feedback to the arm control from its environment. This is required for although the coordinates of the manipulator system are known, the platform and objects being manipulated may continuously change in shape and location. For the small manipulator, used for dextrous tasks such as alignment and positioning force/feel sensing will also certainly prove to be a requirement. Force/feel recognizes the need to resolve and control the force that can be delivered
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