Static stiffness modelling of EAST articulated maintenance arm using matrix structural analysis method

•A general mathematical approach to estimate the static stiffness of robot system based on matrix structural analysis method has been introduced.•Stiffness model of EAST Articulated Maintenance Arm (EAMA) has been built for purpose of error prediction.•Deflections of EAMA robot have been respectively calculated by the mathematical and simulation models.•Less than 5% deviations have been supposed for EAMA stiffness model. The remote inspection and maintenance of the small pieces in vacuum vessel requires certain accuracy to the serial long-reach robot applied in EAST tokamak. The elastic deformations due to gravity and dynamical forces, however, will cause a big trajectory tracking error to the robot end. Therefore, the error prediction and compensation strategy should always be studied in advance to achieve a high required accuracy. This paper presents a mathematical method to estimate the static stiffness of EAST articulated maintenance arm (EAMA) robot. Firstly, the stiffness matrix of the modular parallelogram mechanism of robot is obtained based on the Matrix Structural Analysis (MSA) method. Considering the real constraint conditions of robot arms, the matrix is further simplified to a final version with minimum dimension to improve the computational efficiency. Secondly, the simulation examples have been given to evaluate the accuracy and reliability of the stiffness equations. And finally, the results show that the presented approach has an acceptable prediction error (less than 5%), which can be applied to other similar robotic systems with long-reach complex links.