This paper deals with the trajectory planning for serial robotic manipulators passing through key points by minimizing execution time, energy consumption and joint jerks. Quintic NURBS curves are adopted to fit the trajectory, of which the trajectory is reparameterized with respect to time for generation of geometric path and motion laws, aiming at continuity of the robot velocity, acceleration and jerk. A trajectory planning approach for optimum robot performance is proposed by solving a multi-objective optimization problem to attain optimal curve parameters and distributed execution time along curve segments simultaneously. The proposed technique of trajectory planning is numerically illustrated with a robotic arm and evaluated by experimental measurements. The comparison of total execution time and joint dynamics with/without variables optimization shows the effectiveness of the proposed approach.
This paper presents a four-limb parallel Schönflies motion generator for the pick-and-place application, whose end-effector is composed of a planetary gear train as the amplification mechanism to realize the full-circle rotation. The kinematic aspects including the workspace, dexterity and singularity are analyzed and evaluated. The singular configurations and the singularity loci are identified both graphically and numerically, which shows that the singular configurations of the manipulator can be avoided by keeping all the limbs working in a prescribed working mode together with the end-effector rotation in a clockwise direction from the neutral orientation. Moreover, the dexterity evaluation is carried out to depict the workspace quality and dexterous working envelope. It turns out that the proposed robot admits a super-ellipsoidal workspace with the fullcircle rotation of the end-effector, suitable for pick-and-place operations. Finally, robot dynamics is considered to select the actuators.
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