Mechatronic Design and Maneuverability Analysis of a Novel Robotic Shark

In this paper,the mechatronic design and maneuverability analysis of a novel robotic shark are presented.To obtain good maneuverability,a barycenter regulating device is designed to assist the posture adjustment at low speeds.Based on the Newton-Euler approach,an analytical dynamic model is established with particular consideration of pectoral fins for threedimensional motions.The hydrodynamic coefficients are computed using computational fluid dynamics(CFD)methods.Oscillation amplitudes and phases are determined by fitting an optimized fish body wave.The performance of the robotic shark is estimated by varying the oscillation frequency and offset angle.The results show that with oscillation frequency increasing,the swimming speed increases linearly.The robotic shark reaches the maximum swimming speed of 1.05 m/s with an oscillation frequency of 1.2 Hz.Furthermore,the turning radius decreases nonlinearly as the offset angle increased.The robotic shark reaches the minimum turning radius of 1.4 times the body length with 0.2 Hz frequency and 12°offset angle.In the vertical plane,as the pectoral fin angle increases,the diving velocity increases nonlinearly with increase rate slowing down.

A self-organization formation configuration based assignment probability and collision detection

The formation control of multiple unmanned aerial vehicles(multi-UAVs)has always been a research hotspot.Based on the straight line trajectory,a multi-UAVs target point assignment algorithm based on the assignment probability is proposed to achieve the shortest overall formation path of multi-UAVs with low complexity and reduce the energy consumption.In order to avoid the collision between UAVs in the formation process,the concept of safety ball is introduced,and the collision detection based on continuous motion of two time slots and the lane occupation detection after motion is proposed to avoid collision between UAVs.Based on the idea of game theory,a method of UAV motion form setting based on the maximization of interests is proposed,including the maximization of self-interest and the maximization of formation interest is proposed,so that multi-UAVs can complete the formation task quickly and reasonably with the linear trajectory assigned in advance.Finally,through simulation verification,the multi-UAVs target assignment algorithm based on the assignment probability proposed in this paper can effectively reduce the total path length,and the UAV motion selection method based on the maximization interests can effectively complete the task formation.

循环水通道阻塞效应对自主水下航行器水动力系数估算的影响

The Reynolds-averaged Navier–Stokes(RANS)equation was solved using computational fluid dynamics to study the effect of the circulating tank wall on the hydrodynamic coefficient of an autonomous underwater vehicle(AUV).Numerical results were compared with the experimental results in the circulating water tank of Harbin Engineering University.The numerical results of the model with different scale ratios under the same water in the flume were studied to investigate the effect of blockage on the hydrodynamic performance of AUV in the circulating flume model test.The results show that the hydrodynamic coefficient is stable with the scale reduction of the model.The influence of blocking effect on AUV is given by combining theoretical calculation with experiment.

Undersea Buried Pipeline Reconstruction Based on the Level Set and Inverse Multiquadric Regularization Method

The electric inversion technique reconstructs the subsurface medium distribution from acquired data.On the basis of electric inversion,objects buried under the earth or seabed,such as pipelines and unexploded ordnance,are detected and located in a contactless manner.However,the process of accurately reconstructing the shape of the target object is challenging because electric inversion is a nonlinear and ill-posed problem.In this work,we present an inverse multiquadric(IMQ)regularization method based on the level set function for reconstructing buried pipelines.In the case of locating underwater objects,the unknown inversion area is split into two parts,the background and the pipeline with known conductivity.The geometry of the pipeline is represented based on the level set function for achieving a noiseless inversion image.To obtain a binary image,the IMQ is used as the regularization term,which‘pushes’the level set function away from 0.We also provide an appropriate method to select the bandwidth and regularization parameters for the IMQ regularization term,resulting in reconstructed images with sharp edges.The simulation results and analysis show that the proposed method performs better than classical inversion methods.