Design And Control Of Multi-Degree Of Freedom Bionic Underwater Vehicle

Unmanned underwater vehicles have a wide application prospect in military, civil and other fields. Compared with the traditional propeller propulsion, the bionic propulsion method imitating fish swimming has obvious advantages in efficiency, maneuverability and concealment. But at the same time, caudal fin swing always generates larger lateral force and the thrust force varies periodically. So it is hard for bionic underwater vehicle to sail steadily. A potential way to improve the stability of bionic propulsor is increasing freedom of movement such as long undulating fins. In this paper, the propulsive capability of a multi-degree-of-freedom combinatorial bionic propulsion system is analyzed and control system based on the central mode generator (CPG) is designed. The work and results in detail are as follows:1. A CPG control model based on phase oscillator is established for four-fin and eight-servo systems. The influence of each coupling coefficient on the convergence rate of amplitude, offset and phase difference is analyzed. The response characteristics of CPG model with simultaneous change of multiple control target parameters are discussed. The results show that the CPG model can quickly and stably converge to the new state when the target parameters change, and realize the automatic feedback control of the yaw and pitch of the underwater vehicle.2. Based on the commercial software Fluent, the simulation of the double long-fin wave propagation model under free swimming condition use dynamic mesh is carried out. The effects of frequency, amplitude, wavenumber and the ratio of fin height and fin length on the propulsive capacity of long fins are investigated from the aspects of thrust, lateral force and power. The results provide a guidance for the development of long-fin combination propulsion prototype.3. The CPG control system is designed for the four-long fin propulsion prototype. The corresponding CPGs topology is established for 4 groups and 36 servos system. The PIC microcontroller is used as the control chip and the gyroscope as the sensor, and the course feedback control scheme is established. The simulation results show that the maneuvering can be completed in one cycle. The feedback control torque can be adjusted adaptively according to the deviation angle to ensure the stability of the model.