Analysis and implementation of aquatic locomotion on robotic manta ray

Abstract

To accommodate the environmental problem caused by propeller, alternative underwater propulsion system has been well researched. The development of efficient, maneuverable and yet eco-friendly propulsion method is greatly inspired by locomotion of fishes. There are two classification of fish locomotion based on the fins which is utilized to produce thrust. First, the body and caudal fin locomotion infers to group of fishes such as eels, tunas, and dolphins. They undulate or oscillate their body and caudal fin in order to create thrust. Second, the median and paired fin locomotion refers to fishes which use their pectoral fins, pelvic fins, dorsal fin or anal fin to swim. Stingrays, skates and sunfish are categorized under this group. Each type of locomotion has its own distinct features which give more advantage in swimming than any other locomotion.

In this project, the author developed biomimetics manta ray which uses its pectoral fins and performs rajiform motion while swimming. The development emphasized heavily on designing the prototype, controlling its motion, and testing the robustness of whole system. Six flexible rays are driven by servo motors to construct the motion of flapping fins. This enables the operator to modify the flapping frequency amplitude, and number of waves performed across the fin’s chord length. This system could be used for further learning of biomimetic manta ray locomotion.

Furthermore, as manta ray glides through water when precise swimming is not required, the concept of underwater glider is adopted in this prototype. Buoyancy control system was installed in order to increase the overall power efficiency of the prototype. Two control systems were then introduced to control flapping motion and buoyancy separately. Both control systems run continuously and both are remotely controlled by operator via wireless communication. After being assembled together, test run of the full prototype was then conducted in the swimming pool. The processes of designing, constructing, computing and testing are presented in this report.