Continuum robot has potential to run freely through a cluttered environment as aircraft fuel tank. To improve manual maintenance, we designed an aircraft fuel tank inspection robot which was composed of cable-driven sections. A suitable path is essential for the robot to reach the target zone while avoiding obstacles, but path planning for continuum robot is a challenge due to their complex kinematics models. To depict the collision free planning problem, a nonlinear, constrained optimization formulation was adopted. Projection strategy was presented and an imaginary straight line between the origin and the target was made up as a reference line to simplify the planning problem. We focused on the decrease of computing time complexity, and based on region clipping, a novel forward search method was proposed to solve this optimization-based planning problem. With the reference straight line, the minimum distance summation (MDS) was calculated to decide the optimal path relatively. Experiments on MATLAB were reasonably designed. Simulations and results analysis demonstrated excellent performance of region clipping search method and feasibility of the avoidance algorithm.

A 3D path-tracking algorithm based on endpoint approximation is proposed to implement the path traversal of robots designed to inspect aircraft fuel tanks. Kinematic models of single-joint segments and multiplejoint segments were created. First, each joint segment of the path was divided into many equal sections and the rotation angle was computed. The rotation angle was found for the plane determined by one divided point and the secondary terminal joint segment. Second, the shortest distance search strategy was used to calculate the bending angle of the joint segment. The main advantage of the algorithm was that only the terminal joint segment variables needed to be solved, the joint variables of other joint segments were copied from the adjacent front-end joint segment variables in turn. Finally, evaluation indexes of path tracking performance were proposed to evaluate the effect of the algorithm. Simulations of planar and space path tracking were carried out using MATLAB, and the effectiveness and stability of the tracking algorithm were verified.

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A continuum robot was designed to assist aircraft crew in inspecting fuel tanks, thereby decreasing the workload of fuel tank inspection and improving the efficiency of maintenance. The Rzeppa universal joint and cylindrical helical spring were taken as the joint section of the main body, and the load capacity of continuum robot had been improved greatly. Based on the isokinetic feature of the Rzeppa universal joint, the single-section kinematic analysis of the continuum robot was conducted according to the unit load method of cylindrical helical spring. Next, the influence of variable curvature bending properties of the plant was reduced, and the mapping relationship among the end position, joint variables, and the length of driving cables was obtained. Finally, the simulation and prototype experiments were performed, and the results proved the strong loading capacity of the continuum robot and the effectiveness of the kinematic model.

The Continuum Robot has a multiredundant dof structure, which is extremely advantageous in the unstructured environment, and can complete such tasks as aircraft fuel tank inspection. However, due to its complex kinematics and coupling of joint motion, its motion path planning is also a challenging task. In this paper, a path planning method for Continuum Robot based on an equal curvature model in an aircraft fuel tank environment is proposed. Considering the complexity of calculation and the structural characteristics of Continuum Robot, a feasible obstacle avoidance discrete path is obtained by using the improved RRT algorithm. Then, joint fitting is performed on the existing discrete path according to the kinematic model of Continuum Robot, joint obstacle avoidance was conducted in the process of fitting, and finally, a motion path suitable for the Continuum Robot was selected. A reasonable experiment is designed based on MATLAB, and simulation and analysis results demonstrate excellent performance of this method and feasibility of path planning.