Stiffness-maximum trajectory planning of a hybrid kinematic-redundant robot machine

The paper presents an approach for the trajectory planning of a hybrid serial-parallel redundant robot by investigating the best stiffness performance. The robot under study has 10 degrees of freedom (DOF); six DOF are contributed by a parallel mechanism, and four DOF from serial-link carriage. Due to these redundant degree freedoms, the robot body configuration is under constrained even when the position and orientation of the end-effector has been fixed. In this case, the stiffness of robot varies in all the possible joints configurations. When the path of the end-effector has been prescribed, the robot body configuration can be dominated by taking into account of the stiffness of robot, i.e. among of all the possible configurations, the joints take a value when the stiffness of robot reaches maximum. To solve the stiffness optimization problem differential evolution (DE) algorithm is employed. In the paper the stiffness model as an object function has been built. The evaluation results demonstrate that the DE is an effective method for searching joints parameters in optimum stiffness, and the results with respect to the optimum stiffness show that the joints trajectory planning is feasible for the robot control.