Study On Depth Control Of Robotic Fish Synergistically Propelled By Pectoral And Caudal Fin

Robotic fish has shown the advantage in the complicated environment and task requirements because of the excellent propulsion and well-adapted,and it is the research hot in the field of robotics.There are two main propulsion mode and Media and Paired fin Propulsion mode.Most researches on robotic fish are based on one of these modes,while few researches on pectoral and caudal fin coordinated propulsion.Motion control in three-dimensional has always been the research focus of robotic fish.The methods to realize the snorkeling mainly include center of gravity method,Angle of attack method and swim bladder method.This project is based on the self-designed box-like pufferfish robot.Under the mode of coordinated propulsion of pectoral and caudal fins,the sliding block mechanism and water capsule mechanism are used to control the snorkeling motion of the robot fish in three-dimensional space.The following research is made on the depth control of the robot fish.1.In the body coordinate system,the relationship between the motion of the two-degree of freedom pectoral fin and the one-degree of freedom caudal fin and the fluid was analyzed.By means of the rotation matrix,the dynamic model of the robot fish in the fluid was established in the spatial coordinate system.Considering the robustness of robotic fish motion control,the Central Pattern Generator(CPG)was used to control the motion of each joint of robotic fish.Based on the dynamical model of robot fish,the CPG parameters are adjusted to realize the basic motion mode.The simulation results show that the robot fish have good robustness.2.In order to realize the stationarity and improve the upper limit of attitude change in the snorkeling movement,using the method of center of gravity and angle of attack to achieve snorkeling.The effects of center of gravity method and angle of attack method on the posture of robot fish were analyzed respectively,based on the finished dynamic model and the CPG network.A fuzzy controller is designed and realized the desired depth control through uniting the method of center of gravity and angle of attack.It can be seen that the performances of the designed controllers are improved compared with the only way of depth control method of robotic fish.3.By using the swim bladder mechanism in the axial position of the robot fish,the relationship between gravity and buoyancy is changed by suction and drainage to realize the floating motion of the robot fish in the water.In the two-dimensional basic motion mode,a PID controller is designed to control the suction and drainage of the swim bladder mechanism to achieve high mobility of snorkeling.In the three-dimensional space movement,the fast snorkeling movement of the robot fish is realized by the swim bladder mechanism.In order to mitigate the influence of the high maneuver of the swim bladder mechanism on the snorkeling trajectory,the pitch Angle fuzzy controller is designed.The trajectory of the robot fish during snorkeling is adjusted based on the barycenter method and the Angle of attack method.