Development of walking system for spiral-propelled tidal flat shellfish harvesting device

Most of the tidal flat shellfish harvesting equipment predominantly employed tracked or wheeled walking devices, which encountered issues such as significant sinking of the driving components during operation, poor load-carrying capacity of the devices, and high maintenance costs in the later stage. Therefore, this paper designed a tidal flat walking device based on the principle of spiral propulsion, which could be used for transportation, and conducted structural design and experimental research on the walking device. The impact of the spiral blade structure on working performance was analyzed by using DEM-MBD(discrete element method-multibody dynamics) coupling simulation technology. A single-factor test was carried out to identify the optimal range for height, thickness, and helix angle of spiral blade on the walking mechanism. Subsequently, a three-factor and three-level orthogonal test method was then used to determine the optimal design parameters of blade. Finally, no-load and load operating performance tests were carried out on an experimental prototype, which was constructed according to similar criteria to evaluate the working performance of the designed running gear. The results indicated the following: 1) When all factors were independent, the slip rate of the walking device increased with higher helix angles. Both the traction force and working efficiency of the walking device initially increased and then decreased with higher helix angles. The slip rate of the walking device increased with the thickness increased, while working efficiency and traction coefficient of the walking device followed an initial increase and then decrease pattern. On the other hand, increasing the height-to-diameter ratio resulted in a decrease followed in slip rate of the walking device. The traction coefficient, increased overall with higher height-to-diameter ratios, with working efficiency exhibiting a similar trend. 2) The walking device demonstrated optimal driving performance with a helix angle of 25°, a height of 150 mm, and a thickness of 7.5 mm as determined by orthogonal test. 3) The slip rate of the walking device was 46.92% with no load, 63.56% with a 10 kg load, and 58.34% with a 15 kg load. The slip rate displayed an overall upward trend with increasing load. The subsidence amount was directly proportional to the load, with values of 47.59 mm, 60.09 mm, and 70.22 mm for no load, 10 kg load, and 15 kg load respectively, with a proportional coefficient of 1.512. 4) The rated load of the walking device was approximately 8 kg while the ultimate load was around 21.61 kg, which demonstrated its robust carrying capacity in the tidal flat environment. 5) In comparison with the simulation experiments, the deviation rates of subsidence and slip rate were 10.191% and 3.176% with no load, 3.744% and 3.571% with a 10 kg load, and 24.614% and 4.061% with a 15 kg load respectively. This affirmed that the simulation results could offer reference for prediction and analysis of walking device performance. These research findings were valuable for the development of more efficient tidal flat harvesting equipment with stronger carrying capacity.