Research On Design And Control System Of Frog-inspired Swimming Robot Actuated By Penumatic Muscles

In recent years,land resources have gradually dried up.It has become the focus of attention of the world to explore the ocean and make it safe and reasonable to develop and benefit mankind.It has led to the demand for scientific research and military safety,such as deep-sea resource exploration,Marine Surveillance alerts,underwater biological research and emergency relief.Benefiting from such demand,the research on bionic diving robot has received much attention and has been developing rapidly.Bionic underwater robot can be divided into many types according to propulsion mode and driving mode.Frogs are amphibians who have two modes of movement in water and on land.Compared with the existing traditional underwater robot,the frog inspired robot can have faster speed and flexibility and has important scientific research value and practical significance.Through the study of the structure design and control system of the imitation frog swimming robot,this paper explores the different sliding mode of the flippers,which are different from the fin swing,the hydrofoil flapping and the backflush propulsion,and solve the problem of joint position servo control of underwater vehicles,it lays the foundation for designing a bionic underwater robot with amphibious characteristics.First of all,in view of the previous research on the mechanism of frog muscle and bone movement and the characteristics of frog movement,the simplified hind limb model of frog like robot was simulated and optimized,and the optimal joint size and angle of installation were obtained.Through the parameters determined before,a frog like robot joint based on the pneumatic muscle reset spring is designed and analyzed,and the advantages and disadvantages of the structure and the original structure are analyzed.In order to better imitate the moving posture of the frog,in view of the nature of the frog's hind limbs,it is reasonable to simplify the design of the hind limbs of a frog like robot with five degrees of freedom.It includes a hip posture adjustment mechanism,a modular frog robot leg and a power detection flipper.We design gas supply system and hardware control circuit system integrated with frog frog robot body.The waterproof main housing structure of the frog robot is designed to accommodate high-speed on-off valves,valves,batteries and hardware circuits.And we seal the legs to ensure that the joints will not flow in the water.Secondly,after the structural design is completed,the pneumatic muscle experiment platform is set up to carry out the isotension experiment,the isobaric test and the equal length experiment.The influence factors of the pneumatic muscle output force are analyzed.Based on the experimental data,the mathematical model of the pneumatic muscle based on the Tondu is corrected.The output characteristics of the high speed switch valve,the gas energy equation and the joint dynamic equation are analyzed,and a single input three order affine nonlinear mathematical model is established,and the connection between the input pulse width modulation(PWM)signal and the joint output angle is established.The S function of MATLAB is used for simulation analysis,and the corresponding static and dynamic output is obtained through different input values.At the same time,the influence of 3 main factors on the simulation model,including the friction of pneumatic muscle,the pressure of gas source and the stiffness of spring,is studied.Third,in order to realize the precise control of the rotation angle of the single joint,the equivalent sliding mode control law is designed based on the three order affine nonlinear mathematical model established above,so that the controller can calculate the control input in real time through the angle of the joint feedback and the actual air pressure of the pneumatic muscle.The dynamic and static control effect of the control law is verified by establishing simulation platform in MATLAB SIMULINK.At the same time,the frog robot swimming is divided into extension stage,slide stage and recovery stage.Based on the swimming trajectory of wild black frog,the trajectory planning is carried out at all stages.Acceleration planning is carried out according to the most important extension stage.Finally,each joint angle is solved by kinematics calculation.Finally,the robot control system is completed,the experimental platform is established,and the robot control program is written.The experiment research on the movement of robot in the water environment is carried out to verify the design of the robot,the rationality of the theoretical analysis,the feasibility of the trajectory planning and the control system.