This research proposes a multifaceted approach of three-dimensional trajectory planning based on the combination of Rapidly-exploring Random Tree–Connect algorithm and artificial potential field method to improve the path search ability and dynamic obstacles avoidance capability of unmanned aerial vehicles. Firstly, an improved method of the target gravity is developed by controlling the sampling range to reduce invalid sampling and speed up the convergence speed of the algorithm so as to lessen the restriction of low efficiency and random sampling of the Rapidly-exploring Random Tree–Connect algorithm. Moreover, the regulation factor is introduced into the artificial potential field method to deal with the problem of target unreachable in the trajectory planning. Then the improved Rapidly-exploring Random Tree–Connect algorithm is implemented to plan the global path in a complex environment. This step is carried out via selecting the local target point on the global path found in the global plan, dividing the complex environment into simple environment and utilizing the artificial potential field method to achieve the effect of avoiding unknown dynamic obstacles in the simple environment. Finally, cubic B-spline is employed to smoothing of the planned trajectory. The simulation results demonstrate that the combination of two improved algorithms improves the path search ability and dynamic barrier avoidance capability of the unmanned aerial vehicles.

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For monitoring the online jet characteristics and improving the corresponding diagnostic accuracy, caused by the complex working environment of arc plasma generation systems, an online diagnostic method of arc plasma jet characteristics based on wavelet transform and linear regression theory was proposed. The wavelet denoising to improve the accuracy of plasma jet characteristics and the linear regression theory to predict the plasma arc voltage characteristics have been discussed. Hence, a comprehensive online diagnostic system of plasma jet characteristics has been designed by integrating the proposed method with LabVIEW virtual instrument technology. To verify the effectiveness of the online diagnostic method and system, the corresponding experiments have been conducted by using a homemade plasma generation system with specified working parameters. Sequence, the experimental results have been analyzed and discussed. The experimental results show that: ① the proposed online diagnostic method based on wavelet transform and linear regression theory could effectively improve the accuracy and predict the jet characteristics of plasma jets; ② the online jet characteristics of thermal plasma jet could be monitored by using the corresponding diagnostic system.