In this study, a hyper-redundant manipulator was designed for detection and searching in narrow spaces for aerospace and earthquake rescue applications. A forward kinematics equation for the hyper-redundant manipulator was derived using the homogeneous coordinate transformation method. Based on the modal function backbone curve method and the known path, an improved modal method for the backbone curves was proposed. First, the configuration of the backbone curve for the hyper-redundant manipulator was divided into two parts: a mode function curve segment of the mode function and a known path segment. By changing the discrete points along the known path, the backbone curve for the manipulator when it reached a specified path point was dynamically obtained, and then the joint positions of the manipulator were fitted to the main curve by dichotomy. Combined with engineering examples, simulation experiments were performed using the new algorithm to extract mathematical models for external narrow space environments. The experimental results showed that when using the new algorithm, the hyper-redundant manipulator could complete the tasks of passing through curved pipes and moving into narrow workspaces. The effectiveness of the algorithm was also proven by these experiments.
Abstract. The mapping relationship between the driving space and
the workspace is essential for the precise control of a cable-driven
hyper-redundant robot. For a hyper-redundant robot driven by cables, the
relationships between the driving space and the joint space and between the
joint space and the workspace were studied. A joint-decoupling kinematics
analysis method was proposed and a kinematic analysis was presented. Based
on the analysis of the coupling effect between the cable-driving space and the joint space, a decoupling analysis of the whole cable-driving space and
joint space was conducted to eliminate the coupling effect between the
joints, and the mapping relationship between the driving cables and the
joint angles was obtained. Given the initial and target orientations of the
hyper-redundant robot, the variation law for each joint angle was obtained
using quintic polynomial trajectory planning and the pseudo-inverse Jacobian
matrix, and then the driving cable variation law could be solved. Based on
the results, the joint angle changes and the workspace trajectories were
solved in turn. By comparing with the initial trajectory, the simulation
results verified the appropriateness of the decoupling analysis.
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