Abstract：For a 9-DOF (degree of freedom) hydraulic manipulator, a set of nonlinear equations are established to solve its inverse kinematics of position and orientation. An objective function is proposed to minimize the position and orientation error of the end-effector, and the solution problem of the nonlinear equations is transformed into an optimization problem, which is solved by the differential evolution (DE) algorithm. Firstly, self-adaptive weight coefficients are introduced to avoid the difference of the convergence accuracy of position error and orientation error. In order to overcome the difficulty of the basic DE algorithm in balancing the global and local exploitation abilities, DE/rand/1/bin and DE/best/1/bin, the two evolution models are combined to improve the self-adaptive mutation differential evolution (SAMDE) algorithm, resulting in better convergence accuracy and convergence rate. Finally, the reflection approach is applied to dealing with the individuals exceeding the boundary of the joint angles, and thus the convergence accuracy is improved. Some contrastive experiments with the basic DE algorithm are conducted. The simulation results indicate that the proposed method outperforms the basic DE algorithm in terms of convergence accuracy and convergence rate, and improves the stability significantly.
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