K.H. Low
Biomimetics, bio-locomotion, underwater robot, undulating fins,modular mechanism, depth control
This paper describes the design of the propulsion system and depth control of a robot fish. The design is inspired from the knifefish. The propulsion system is based on the undulating fins. A simplified model of the fins is constructed by using oscillating servomotors to which are attached cranks holding flexible membranes that can slide permitting the variation of the length of the fins. The depth control was inspired from the gas bladder of fish which changes volume to control the depth based on the buoyancy forces. A buoyancy tank, equipped with two pistons, is used to change the submerged volume. Proximity sensors are used to monitor and limit the piston movement. The robot fish was controlled using microprocessors which takes readings from proximity, depth and pitch sensors, and implements a control scheme. Bluetooth technology was used to interface the robot fish to a laptop to allow the operator to control the robot fish. The propulsion speed was measured as a function of phase angle and a frequency of the servomotors. Testing has also been conducted in an outdoor diving pool to demonstrate the capability of the knifefish robot in various swimming courses and also the depth control of the bio-fish 4 m under the water. The design structures and mechanisms can be scaled down for micro-bio-fish models. The micro-fin model driven by a smart actuator is being tested. The bio-mechatronics implementation can be applied in defence and medical applications as the model is modular, scalable, and re-configurable.
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