Continuous Motion Modeling and Analysis of a New 2UPR‐PRS Mechanism with Variable Rotation Axis

Abstract

Since parallel mechanisms (PMs) have good stiffness, accuracy, and dynamic characteristics, a large number of PMs have been invented recently. A few kinds of them are found to have excellent performances, and one kind is two‐rotational and one‐translational (2R1T) PM. The existing research on 2R1T PMs shows that this kind of mechanism has outstanding rotational properties and a well‐translational workspace. Many 2R1T mechanisms with good performances have been proposed, among which the typical ones are 3PRS, 2UPR‐SPR, and 3UPS‐UP. Based upon the existing 2R1T mechanisms, a new 2R1T mechanism, 2UPR‐PRS, is proposed and analyzed in this paper, which combines PRS and UPR chains, respectively, from 3PRS and 2UPR‐SPR together. In this way, the high stiffness provided by the PRS chain and the variable rotational characteristics from two symmetric UPR chains are integrated into the proposed 2UPR‐PRS mechanism. First, the conceptual design of this mechanism is carried out. Second, its inverse kinematics is solved. Finally, the mobility of the mechanism is analyzed by a newly developed method through a parameterizing twist in a continuous motion manner, and its kinematic model is thus formulated, revealing the rotational characteristics of the mechanism with the variable axis.