Plane-parallel motion of a trimaran capsubot controlled with an internal flywheel

Abstract

Swimming robots driven by internal mass motion are demanded for applications in aggressive media. A novel type of such robot is proposed – a trimaran controlled by a single internal flywheel. The robot consists of a platform, three blades rigidly connected to it, and a flywheel located at the platform. A control torque is applied to the flywheel. The control is the sum of periodic excitation and feedback terms. It provides oscillations of the flywheel. Oscillations of the flywheel cause oscillations of the platform with blades. Oscillating blades submerged in fluid provide the thrust force. The mathematical model of the system is constructed basing on the quasi-steady description of hydrodynamic loads. Parameters of the control law are adjusted to increase the propulsion speed. It is shown that the lateral force acting on each blade plays crucial role in the propulsion. In a wide range of parameters, the system possesses two types of attracting periodic modes of propulsion: high-speed bow-first motion and low-speed stern-first motion. Both these modes are irreversible with respect to the main direction of propulsion. The self-start of the robot to a high-speed mode depends on geometrical parameters and on the control law. The laboratory prototype of the robot is constructed.