Multi-mode amphibious robot can work in the shoal environment. (PHOTO: SCREENSHOT)

By Staff Reporters

A novel multi-mode motion robot named SHOALBOT, developed by a team at Harbin Engineering University in 2022, can operate by depending on only one type of propulsion device and can work flexibly in an amphibious environment, including running on beaches, grassland, the seabed, and moving through water.

Robots that work in water need to minimize the number of drive components to improve reliability and reduce communication pressure. SHOALBOT's unique design enables it to rely on a kind of propulsion device named propeller-leg, giving it the ability to run rapidly on beaches and on seabeds, swimming with multi-degrees-of-freedom in water (such a propulsion system contains only four driving elements), while also helping the robot complete more work and improve its adaptability to outside environment.

Running is more stable than swimming and will not disturb marine life, but when the robot encounters a high obstacle with a large area coverage, switching the motion mode to swimming mode, it can pass directly over obstacles instead of detouring or abandoning its work, something which can improve work efficiency.

The R&D engineers analyzed and optimized the robot's propeller-leg by simulation, combined with an open water test, finding the propeller-leg's thrust in the water before and after optimization differs by 400 percent according to test results.

The research team also optimized the minimum difference between the forward and reverse thrust of the propeller-leg to improve the stability of the robot's movement process and optimized the difference from 25 percent to three percent.

A series of performance evaluation experiments validated that the SHOALBOT has excellent movement ability in an amphibious environment, compared with other published amphibious robots of the same size.