Parametric joint compliance analysis of a 3-UPU parallel robot

Sufficiently low compliance is required for robot end-effectors to perform various tasks with high static and dynamic accuracy. The joint compliance and link compliance of robots are the two major factors for the determination of overall end-effector compliance. Unlike serial robots that can allow larger joint sizes to improve the joint compliance, the joints of parallel robots are usually closely located and hence the joint size cannot be easily increased. Compared with the link compliance, the joint compliance of a parallel robot contributes more to the end-effector compliance, but its importance is often overlooked. To reduce the computational intensity of robot compliance design, analytical joint compliance models are proposed for the class of 3-UPU parallel robots. These joint compliance models can be used to quickly evaluate the compliance contribution of each revolute joint at various parallel robot configurations. Numerical and experimental verifications are provided to demonstrate these models. We expect that the parametric analysis of 3-UPU parallel robot compliance can be facilitated by using the proposed joint compliance models.