Acceleration analysis and optimal design of a 3-degree-of-freedom co-axis parallel manipulator for pick-and-place applications

Robot acceleration is the bottleneck for high-speed pick-and-place operations. In this article, the extreme acceleration at null velocity is proposed to characterize the acceleration capability for a planar parallel manipulator having a common actuated axis, the V3 robot. Detailed dynamic model of the V3 robot is developed for computing the extreme acceleration. Since each subchain of the robot is comparable to a cantilever beam structure, its bending deflection can be considerable and thus leads to manipulation failure. Characterized by the bending deflection, the bending stiffness is thus proposed. Combining the acceleration, the bending stiffness and kinematic constraints of velocity, accuracy, and dexterity, an optimal design problem is formulated to maximize the dextrous workspace having specified desired performance. The optimized structure shows greatly improved performance in workspace, velocity, acceleration, and accuracy.