Abstract
The six-degree-of-freedom flexible joint manipulator is a complex system that suffers from the problem that the trajectory planning results are inconsistent with the control results. To keep the planned trajectory within the control range of the manipulator, a hierarchical structure control strategy is designed, which consists of a trajectory planning layer, a model predictive control layer, and a bottom control layer. Specifically, first, the target joint angles are obtained by a time-optimal trajectory planning algorithm based on a genetic algorithm in the trajectory planning layer. Second, in the model predictive control layer, considering the system physical constraints, the model predictive controller is adopted to provide the set points for the Proportion-Differentiation (PD) controllers. Finally, in the bottom control layer, the manipulator moves along the target trajectory under the PD controllers with the feedback control law. The simulation results show that, compared with the PD control strategy, the hierarchical structure control strategy can achieve better control performance and reduce the tracking error of the terminal trajectory by 33.70%.
Highlights
A flexible joint manipulator is light and small and consumes little energy, making this technology widely used in aerospace, medical, industrial assembly, and other fields [1, 2]
The existing results of manipulator control do not consider the consistency between the trajectory optimization results and the control results; that is, the trajectory optimization results may not be feasible in the control implementation
Each level has its own division of labour, which makes complex problems easy to deal with [7]. e 6-designed. Considering that the multidegree-of-freedom (DOF) flexible joint manipulator control strategy is designed for industrial hierarchical structure systems [8]
Summary
A flexible joint manipulator is light and small and consumes little energy, making this technology widely used in aerospace, medical, industrial assembly, and other fields [1, 2]. Many achievements have been made in the trajectory planning and control implementation of manipulator systems [3, 4]. The existing results of manipulator control do not consider the consistency between the trajectory optimization results and the control results; that is, the trajectory optimization results may not be feasible in the control implementation. E 6-DOF flexible joint manipulator control strategy is designed for industrial hierarchical structure systems [8]. E right portion indicates the basic components of the hierarchical structure, which consist of the trajectory planning layer, the MPC layer, and the bottom control layer. Compared with the existing hierarchical structure in the industry, the main function of the trajectory planning layer is to obtain the target trajectory, the MPC layer makes the terminal trajectory of the manipulator approximate the target trajectory, and the bottom control layer implements the final control. When the trajectory planning of a manipulator is carried out, it is usually possible to maximally optimize some
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