Document Type : Article

**Authors**

^{1}
- State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044, China. - Department of Mechanical and Manufacturing Engineering, Aalborg University, Aalborg 9200, Denmark.

^{2}
State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044, China

**Abstract**

A novel spatial parallel manipulator designed to assemble diagnostic instruments in SG-III is introduced in this paper. Firstly, resorting to screw theory, mobility analysis of this manipulator is investigated. Then the inverse kinematics problem is determined by the method of RPY transformation, with the singularity analyzed. As a key issue in parallel manipulators, it is more difficult to solve the forward kinematics problem, since it is highly nonlinear and coupled. In this work, three different approaches are presented to deal with this issue, which include the back propagation neural network, the simplified ant colony optimization and the proposed improved Newton iterative method. Simulation of each approach is conducted, and their merits and demerits are compared in detail. It is concluded that the improved Newton iterative method which can provide good initial iteration values possesses the best performance to estimate the nonlinear forward kinematic mapping of the considered parallel manipulator

**Keywords**

- parallel manipulator
- kinematics analysis
- Neural network
- ant colony optimization
- Newton iterative method

**Main Subjects**

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Transactions on Mechanical Engineering (B)

January and February 2019Pages 346-357