Low-velocity resistance distortion and bionic drag reduction for ship-type paddy field machinery

The resistance between mud surface and ship-type paddy field machine hull accounts for a certain proportion of the total mechanical power consumption during the operation process.The special characteristic has been found via preliminary study,it showed that when starting or working at low velocity,the resistance is much greater than the machine working at the rated velocity.This characteristic affects the dynamic matching and structural design of the machine.The critical velocity of resistance distortion was around 0.025 m/s under the setting experimental conditions,and the mechanism of resistance distortion under multi-medium was analyzed.Based on water film drag reduction theory,a macroscopic structure of crocodile's abdominal armor biomimetic drag reduction method was proposed.Two kinds of bionic macroscopic structure ship board were fabricated.The macroscopic structure can introduce more water into the bottom surface of the hull;thicken the water film,which can reduce the travel resistance.Design and manufacture a ship-type paddy field experimental setup with velocity control,and compare the traditional smooth surface ship board with the two bionic macroscopic structure surfaces through orthogonal test.The experiment results demonstrated that the ship board with rectangle gully structure has better drag reduction effect than the hexagon one in the lower velocity.But when the travel velocity approach to the resistance distortion critical point,the hexagon gully structure become better than the other one.Through the orthogonal test,the best drag reduction combination is 2.5 kg load weight,0.025 m/s travel velocity with hexagon ship board,which decreases the drag by 6.3%.

Posture-invariant hybrid scaling weight measurement algorithm for live eels

To obtain higher economic benefits,large eel breeding companies classify live eels by weight.Due to their strong mobility and smooth body surface,living eels are not suitable for traditional mechanical weight measurement.In this study,a live eel sorting machine based on machine vision was developed,and a novel method was developed for obtaining live eel weight measurements through images.First,a backlit workbench was designed to capture static images of eels,and then the projection area and skeleton length of the images were obtained by image preprocessing.For the eel's body shape,which is generally cylindrical and gradually transitions to a flat tail,the tail posture changes affect the shape of the images;thus,a weight measurement model combining the projected area and the skeleton length was proposed.The optimal scale division coefficient of the weight model was found to be 0.745 by experimentation.Then,select eels of different weight ranges were used for model error verification and to obtain the correction function of the error.The weight gradient was used to confirm the corrected eel weight model.Finally,the system calculation results were compared with the actual measurement results.The root mean square error(RMSE)was 12.94 g,and the mean absolute percentage error(MAPE)was 2.12%.The results show that the proposed method provided a convenient,fast,and low-cost non-contact weight measurement method for live eels,reduced the damage rate of live eels,and can meet the technical requirements of actual production.