Design Of A Bionic Frog Robot And Research On Trajectory Planning Of Intermittent Jumping

With the outstanding ability of surmounting obstacles, bionic hopping robot can completed missions such as planetary exploration, military reconnaissance, disaster relief and other work in unstructured and unknown environments instead of human, which has a broad application prospect. The bionic jumping robot has the characteristics of high jumping power,flexible movement that required the driving performance of the bionic hopping robot has high energy density. Moreover, because the jumping motion is a multivariate, variable constraint and under actuated kinematic and dynamic process, the task space trajectory planning research is challenging. In this paper, the key problems of kinematics, dynamics and obstacle navigation trajectory of the bionic frog robot with elastic energy storage element has been researched and validated through the simulation and physical experiment.Base on the analysis of the physiological structure of the frog, a simplified model of the robot mechanism and the joint trajectory of the hind legs during take-off are abstracted, and then SLIP model is used to analyze the jumping motion law of the mass center. According to the high energy density driven performance requirements and jumping movement rules of the bionic frog robot, the structure of intermittent jumping frog robot with elastic storage energy components is designed.The constraint states of each stage with ground are different in the jumping process of the frog leaping robot, so the jumping motion of the bionic frog robot is divided into four phases: preparation, take-off, flight and landing, and the kinematic equations are established respectively by using D-H method. Using the kinematic equation, the relationship between the body posture and the joint angle of the robot, mass-center position, velocity and acceleration of take off phase and toe position and speed of the flight phase are analyzed.Because of the underactuated constraints in the take-off phase of bionic frog robot,the kinetic, gravitational and elastic potential energy of take-off phase are analyzed. And then the kinetic equation is established by Lagrange method, the law of the mass center motion and the motion trajectory of joint space are obtained. At last,the correctness of the kinetic equation is verified by the simulation.The toe trajectory equations are established for research of bionic frog robot obstacle crossing ability and quantitative computation of the bionic frog robot flight trajectory. And the constraints of the bionic frog robot crossing obstacle trajectory planning is established according to the crossing obstacle trajectory requirements, the pose adjustment ability, driving ability, the stability of landing, and ground friction etc. According to the hopping distance,energy consumption and safety requirements of bionic frog robot, a unified objective function has been established by using linear weighted combination method. And then the multi-objective optimization problem is solved by using improved particle swarm optimization algorithm, that different toe flight trajectories to fit different targets are obtained.Finally, storing energy, pose preparing and jumping motions are tested on the bionic frog robot prototype with control system. Then,a jump process was recorded by the camera for the comparative analysis of jump trajectory and theoretical calculation results, which verifies the validity of dynamics analysis and trajectory planning.