For the dimensional parameter optimization of 3-UP
S & S parallel mechanism, an optimal geometric configuration of the shipborne stable platform is obtained to improve its kinematics performance by niche genetic algorithm with the workspace size and global force transmission rate as design indices. Specifically, a combination of numerical and analytical methods is used to determine the validity of constraint conditions such as branch chain length, joint rotation angle, singularity, etc., and to solve the workspace of the parallel stable platform. The minimum singular value of the inverse of force Jacobian matrix is used to define the local force transmission index, and the average value of the local force transmission rate in the workspace is used as the global force transmission index. Taking the weighted sum of the workspace size and the global force transmission rate as the optimization objective, the niche adaptive genetic algorithm is used to complete the optimization solution and obtain the optimal dimensional parameters. The performance comparative analysis with the initial configuration shows that the optimized configuration achieves a 35% improvement in force transmission performance and has better comprehensive kinematics performance. A test prototype is manufactured and related experiments are carried out to verify the effectiveness of the proposed optimization method for dimensional parameters. Finally, the law of the effect of different weight coefficients on the optimization results in the process of multi-objective optimization is discussed, and it is found that better comprehensive performance can be achieved by balanced weights.