Kinematics Analysis On The Serial-parallel Hybrid Leg Of Anovel Quadruped Walking Robot

With the characteristics of high stability and terrain adaptability, research on quadruped walking robot attracts more and more attention of experts and scholar at home and abroad, which become a hot topic in the field of robot. Quadruped walking robots adopt mostly serial leg mechanism or parallel leg mechanism. However, these two kinds of leg mechanisms have their respective limitations, which lead to the limitations of performances of quadruped robots. Hybrid quadruped robots emerge in response to the needs of times.A novel serial-parallel hybrid quadruped walking robot was presented, and its kinematics and statics characteristics were studied. The hybrid leg mechanism, whose hip joint and knee-joint are a spherical parallel manipulator with three degrees of freedom and a revolute pair respectively, is mainly made of hip joint, thigh, knee and calf sequentially. The major research content is as follows:1. Aiming at the presented novel serial-parallel hybrid leg mechanism, degree of freedom analysis was worked out by screw theory, and mechanics coordinates was established based on the D-H method. Considering the least energy-consuming posture as the optimal posture, the forward kinematics and inverse kinematics were obtained by vector method.2. According to vector method and differential transform method, the velocity matrix and acceleration matrix of the hybrid leg were gained, based on which the singularity of the leg was analyzed. Then the singularity dexterity index applying to all hybrid mechanism was put forward, and parameters ? and 2 1L L were optimized. Finally, with boundary search method, workspace of the hybrid leg was figured out by MATLAB software.3. Establishing the statics model of the hybrid leg mechanism and considering the mapping relationship between constraining force and driving force, the actuation statics transmission equation was gained based on the vector theory and virtual work principle. Then global stiffness index of hybrid mechanism was presented. Finally, given the specific parameters of the leg, force situation of the driving motors were figured out by MATLAB when external force and moment were put on the foot end of the leg mechanism.4. Virtual prototype of the hybrid leg mechanism was established on the basis of ADAMS software. Projecting a typical movement trajectory for the foot end of the leg, co-simulation to the kinematics model was carried out by MATLAB and ADAMS. Then combing the inverse kinematics model, forward kinematics model was proved to be correct by MATLAB. At last, experiment was carried out on the successful trial-produced hybrid leg,and the result of the experiment verified the correctness of both forward kinematics model and the inverse kinematics model.The study is of great significance to a series of further studies upon stiffness analysis, dynamic properties, mechanisms optimal design and system control of the novel series-parallel quadruped walking robots.