| About fifty percent of the surface of earch is covered by dene, marish, massif and so on. Though researchers have invent many kinds of wheeled machine, designing and manufacturing a legged robot like myriapod running in natural environment is still a huge challenge. So researches on legged robot have been always an important branch of robot field. Because of the stronger loading capacity and better stability than biped mobile robot as well as simpler structure than hexapod robot and eight-legged robot, research of quadruped mobile robot has glamourous future as platform for application of medical services, environmental monitoring, terrorism prevention, and other related areas.In view of the robot running environment, the structure of multi-motion mode, four legs and wheeled foots are adopted in this vehicle system. This robot can well combine the priorities of wheeled robot and legged robot, change motion mode to stability walking or fast wheeled driving according to different environments, so realize both flexibility and higher speed. This thesis focuses on quadruped motion research and seeks practical and efficient designing methods in the fields of kinematics analysis, stability criterion, gaits planning, foot force control and emebeded control system.Because of changing motion topology structure of quadruped robot, the inverse kinematics of swing leg and supporting leg are studied by combining series and parallel analysis methods. At the same time, in order to exactly evaluate the robot stability and stability margin while walking, one general criteria is proposed, which adopts the minimal distance from supporting edge to center of pressure on ground to estimate robot walking stability. For convenience, the conception of minimal stability distance is introduced and the relations between stability and parameters such as disturb elements, height of center of gravity, obliquity of supporting plane and mass of robot are discussed.Based on the combination of characteristic analysis of animal gait and our robot structure, discontinuous crawl gait for uneven surface and coordinated crawl gait for even surface are proposed with different gait variable value. Meanwhile, two kinds of gaits are compared and analyzed by simulation in the aspect of stability margin and body compliance. At last, turning gait and sway track planning is introduced which provides theory base for later experiments.To maintain quadruped robot scheduled posture on rough terrain and realize good transition of sway leg from free space to constraints space, the whole force model and virtual suspension model of quadruped robot is established. The foot force distribution is optimized and robot posture amending algorithm is proposed based on foot force compensating. Besides, the paper applies improved impedance control based on foot position to make legs achieve good transition from sway status to supporting status and expected force tracking. Such methods avoid computing complicated multi-body dynamics, so has characteristics of high real-time and feasibility.Finally, the embedded hierarchical control system of quadruped robot is proposed. In view of nonlinear of joint load, the embedded controller adopts algorithm of fuzzy regulation with modifiable function and realizes good joint speed tracking. The integration of control system lays the foundation for quadruped robot remote control. At the same time, several experiments such as joint speed and position tracking experiment, one leg impedance experiment, walking experiments on even and uneven plane are carried out. The experiment result confirmed the validity of the designing and theoretical analysis of the robot system.
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