When a robotic manipulator approaches a kinematic singularity, small displacements of the end effector require large motions at the joints of the system. For this reason, a manipulator is unable to track trajectories in workspace regions near singularities, and the presence of singularities limits the range of performable tasks. A robotic welder, for example, is unable to form a continuous weld bead in such regions. To prevent these difficulties, a manipulator should be constructed that has no singular positions within its workspace. A new robotic wrist (the prototype is shown on the next page) is just such a device.
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