Static characteristics of an in-parallel actuated manipulator for clamping and bracing applications

The static characteristics of a three-degree-of-freedom in-parallel actuated manipulator are discussed, along with its desired static actuator characteristics for clamping and bracing applications, where the term `bracing´ refers to a strategy to rigidize the wrist for subsequent fine motion performed by the end-effector or a second manipulator. The short-arm manipulator is characterized by its rigidity, high force-to-weight ratio, and relatively simple inverse kinematics. Particular attention is given to the influences of the joint reactions on the manipulator performance and the appropriate control strategy for clamping and bracing. The static analysis, along with the static representation of velocity and force ellipsoids, establishes a rational basis for minimizing the bending moments which tend to cause an increase in nonlinear friction. Also, it predicts the reaction forces acting at the ball joint for a specified payload, which appear as time-varying external forces/moments on the link actuation