| Hopping robot has the characteristics that it can move quickly and flexibly, it also has strong off-road ability. It is particularly suitable for performing tasks in all kinds of complex terrain and bad environment. The hopping movement is sudden and explosive which helps the robot to avoid danger. These benefits have made it become researchers'focus. At home and abroad, research on bionic multi-joint hopping robot is still in its infancy.The frog has great jump ability, and it is also an excellent bionic prototype. The bionic research on frog's hopping principle in this paper is both on the pattern and mechanism. A multi-joint and multi-DOF robot model has been established including frog's fore and hind legs,and the movement mechanism of take-off phase is also been researched.On the analysis of the physiological and hopping movement's characteristics of frog, a five joint simplified model has been abstracted which can reflect hopping movement's characteristics. On the comprehensive analysis of current research on biomimetic hopping robot, the guidelines that design a frog-like robot should follow are determined. And in accordance with the guidelines, a five joint prototype has been designed, which has elastic joints and is drived by synchronous belt.The characteristics of frog's take-off stage has been analysed, on the basis of this, the stage is devided into two parts. The first part which is called "both legs touch the ground ", describes the state that fore and hind legs of frog are keeping contact with the ground. The second part which is called "hind leg touchs the ground", describes the stage that frog's fore legs have left the ground but the hind legs are still keeping contact with the ground.A kinematic model of "both legs touch the ground" has been established in accordance with the theory of parallel mechanism, the vector method is used to solve the positive and inverse solutions of kinematics. The Jacobian matrix of "both legs touch the ground" is formed by solving branched-chains'Jacobian matrices. The "both legs touch the ground" kinematics'positive and inverse solutions are simulated analysis by using Matlab.The "hind leg touchs the ground" kinematics model has been established following the the theory of serial mechanism, The kinematics'positive and inverse solutions is solved by using D-H theory, and the Jacobian matrix has been solved. On this foundation, the judgement of a frog-like robot take-off has been analysed.By establishing a relationship between the various angles and planning the angle between the foot and the ground, the movement principle of take-off stage is analysed. Then the movement principle of "hind leg touchs the ground" is simulated and analysed by using Matlab.Based on multi-body dynamics theory, a four rigid bodys model was built,including body, thigh,calf and foot. The dynamics equation of the stage that hind leg touchs the ground was built using lagrange equation of the second category.The joint torque characteristics were researched using Matlab,and the data coming from chapter IV.Finally,the elastic joint was proved to be effective and correct by the prototype's experiment. |
