| The development of effective robotic systems requires that critical issues relating to kinematic design, motion control, path planning and dynamics be resolved. This paper investigates the design and implementation of ROBOSIM, a robotic simulation software tool which may be used to resolve these issues. Several NASA related robotic systems studies are summarized. These studies included: the development of a robotic cell for Solid Rocket Booster (SRB) refurbishment; the development of a bilateral mechanism, for repairing and servicing satellites, to be placed on-board the Orbital Maneuvering Vehicle (OMV); and the development of automation and robotics for the U.S. Space Station. A fourth study in which an algorithm for generating off-line programs for the coordinated motion of a robot and positioner used in arc welding operations is treated in greater detail. The algorithm maintains the orientation of the part to be welded so that the weldment is in the downhand position, weld travel speed is constant, and a filler wire (if present) is properly positioned with respect to the path. The example presented included a six degree of freedom robot and a two degree of freedom part positioner. In formulating the control algorithm the robot and positioner are treated as a single mechanism having eight degrees of freedom. The Jacobian of the combined mechanism is formulated and the kinematic redundancies are resolved by imbedding additional constraint equations imposing proper part orientation and filler wire control. ROBOSIM was then used to model the robot, positioner, and a convoluted part. The modelling process results in the development of a data base of kinematic and dynamic properties which may be accessed by a control library. The welding algorithms were then implemented using calls to the control library, and a verification was made by observing their proper operation in graphic simulation. |
