by an arm during operation and allows tasks such as placing a peg in a hole to be accomplished. In one concept the sensor module is incorporated between the wrist and end effector and a software program has been developed that allows the implementation of force feedback in resolved rate control. The technique of force accommodation may also be implemented whereby the manipulator is automatically restrained from exceeding set values. Force accommodation could be used to apply constant acceleration to a payload, or with a suitable end effector to feel around a pay load. It could also allow the programmed application of desired forces for particular task requirements. Perhaps the most widely known application is force reflection whereby the operator experiences the reflected reaction forces on his hand controllers that tend to oppose the desired motion. This technique is particularly suitable for resolved rate systems, where the forces tend to return the hand controllers to the null position. End effector positioning and orientation are essential and time consuming elements in a manipulator task, and the addition of tactile sensing to measure slip and proximity sensing to measure distances provide a faster and potentially closed loop when system autonomy is required. Total autonomy calls for the development of “smart” sensate end effectors whose sensors provide object location, object avoidance, and adaptive grasp. Control of the manipulator system would be “hand directed” by these sensors. To process this amount of data and output real time controller commands will require the increasing use of microprocessor technology, and this would need to be implemented on a distributed system rather than with one central controller. Microprocessors will allow a small programmable component to replace computer and some electronic functions and with distributed microprocessors complex control algorithms will be implemented in situ. These features make the microprocessor potentially useful as a system component where dedicated local intelligence is needed for high reliability long-term applications. Proximity sensing techniques are frequently systems with emitters and detectors and many are sensitive to lighting and surface optical properties. To overcome some of these objections, Spar has been pursuing the use of a photogrammetric technique for proximity sensing. In this system the payload has a known spatial target mounted to it that is viewed by a camera mounted to the end effector. The arm computer calculates the position, orientation and rate of the payload by reference to the target and applying photogrammetric measurement techniques. This data can then be fed back to provide a real time closed-loop control signal for the RMS. Alternative “vision system” techniques are becoming widely used within industry. Such systems can learn to recognize the object to be processed, and can compute its position and orientation. This information can be used to provide control commands to a manipulator. CONCLUSIONS Future manipulator requirements can be divided into two broad categories: the enhancements to existing performance and capabilities and the development of future generation intelligent manipulators. The near future sees the development of a range of special tools for payload handling and servicing, and as user experience is gained greater demands will be placed upon these systems and enhanced arms and second generation “intelligent” manipulator will be developed. Just as on the ground, in space robots are becoming an important economic force to accomplish the
RkJQdWJsaXNoZXIy MTU5NjU0Mg==