Xu Huayang

Kinematics and inverse dynamics analysis for a novel 3-PUU parallel mechanism

The modules of parallel tool heads with 2R1T degrees of freedom (DOFs), i.e., two rotational DOFs and one translational DOF, have become so important in the field of machine tools that corresponding research studies have attracted extensive attention from both academia and industry. A 3-PUU (P represents a prismatic joint, U represents a universal joint) parallel mechanism with 2R1T DOFs is proposed in this paper, and a detailed discussion about its architecture, geometrical constraints, and mobility characteristics is presented. Furthermore, on the basis of its special geometrical constraint, we derive and explicitly express the parasitic motion of the 3-PUU mechanism. Then, the inverse kinematics problem, the Jacobian matrix calculation and the forward kinematics problem are also investigated. Finally, with a simplified dynamics model, the inverse dynamics analysis for the mechanism is carried out with the Principle of Virtual Work, and corresponding results are compared with that of the 3-PRS mechanism. The above analyses illustrate that the 3-PUU parallel mechanism has good dynamics features, which validates the feasibility of applying this mechanism as a tool head module.

Kinematic analysis of cable-driven parallel mechanisms based on minimum potential energy principle

The forward kinematic analysis of the cable-driven parallel mechanism has been a challenging and interesting problem since 10 years ago. This work converts the forward kinematic analysis problem of the cable-driven parallel mechanism to an optimization problem, whose objective is to minimize the potential energy of mobile platform. In order to simplify the optimization problem further so that it can be solved with any simple optimization algorithm in short time, some constraints are introduced to design variables. We utilize the sequential quadratic programming algorithm to solve the simplified optimization problem in this article. The efficiency and effectiveness of the proposed approach are validated with some numerical examples. Furthermore, due to the fact that a required pose may be not stable, the availability of its inverse kinematic solution should be supervised. The aforementioned approach provides a valid tool for solving this type of problems by contrasting the distinction between the required pose and the actual pose calculated by it. The feasibility of applying our proposed method to execute the inverse kinematic analysis of cable-driven parallel mechanism is proved with several examples in this article.