Kinematic Sensitivity Evaluation of Revolute and Prismatic 3-DOF Delta Robots

The Delta parallel robot establishes itself as one of the most successful parallel robot designs thanks to its intrinsic properties. Generally, based on the type of actuator, the 3-DOF Delta robot falls into two groups, namely, revolute-input and prismatic-input. The main aim of this paper consists in evaluating and comparing the kinematic performance of the two foregoing types of Delta robots. So far, different kinematic sensitivity indices have been proposed. In this paper, by employing different kinematic sensitivity indices such as manipulability, dimensionally kinematic sensitivity and weighted kinematic sensitivity indices. the kinetostatic performance of the aforementioned robots are compared over a certain workspace. The obtained results showed that the sensitivity of prismatic Delta robot is high in the center of the workspace and the sensitivity increases when the end-effector moves to edges from the center. However sensitivity of the revolute Delta robot is totally different. It is high on the edges and it decreases by moving to center. weighted kinematic sensitivity results show that geometrical features of the robots are very important and it changes the sensitivity values and trend greatly. Moreover, in order to enhance the kinematic performance of the robots, the configuration of the robots are redesigned using optimization of the kinematic sensitivity indices. The results of this paper revealed that kinematic sensitivity indices can be employed in the design step of the robot to reach an optimal kinematic sensitivity in the workspace.