Research On The Stability And Control Technology Of Quadruped Robot In Trotting

Legged robot has stronger environment adaptability than wheel robot,track robot or wheel-track robot in theory.Quadruped robot has better stability than single foot robot and biped robot,and is more concise and easy to realize gait control than the hexapod robot.Now the quadruped robot has become an important research direction of the robot.The gait of quadruped robot includes crawling,pacing,trotting,galloping and so on.The trotting is not only has faster movement speed,but also the gait energy efficiency is the highest among the several gaits.The trotting as a dynamic gait is the focus of the research in the world in the motion stability and control technology.Quadruped robot is a multi-branched,strong coupling,multi-variable and nonlinear complex system.The kinematics and dynamics model is the foundation of the gait planning,stability analysis and gait control.The quadruped robot kinematics model is based on D-H parameters.By analysis the model,the Jacobean matrix of leg mechanism from Cartesian space to joint rotation the angle of space conversion can be get,which is the theoretical foundation of the gait planning,foot trajectory planning and motion control of the quadruped robot.Based on the simplified mass distribution of each component of quadruped robot,the dynamic model of the quadruped robot is established using Newton-Euler method.By analysis the dynamic model,the velocity,acceleration,joint force,joint torque equation can be obtained,which is the foundation of the quadruped robot gait simulation and control.For the quadruped robot turn around the support diagonal cause of gravity,a quadruped robot inverted pendulum dynamic model is established without neglecting the quality of the foot and leg,and the trotting is simplified into the swing of the diagonal bracing.By analysis this model,a new motion planning of the center of gravity can be obtained,which can eliminate the effect of the gravity when the swinging leg and support leg switch.The foot trajectory is satisfied the swinging legs landing stability and motion continuity to make sure the quadruped robot can move faster and smoothly.The simulation experiments by the PRO/E and Adams verify the rationality of trotting planning.There are many factors affect the stability of the trotting gait of quadruped robot including the different gait planning methods,the effects of different environmental factors such as different ground friction force,motor performance,robot structure and so on.Though the planning of center of gravity decreases or eliminates the turn around the supporting diagonal.Body pitch deviation caused by the swing of the swing legs will be introduced to the gait planning and control improving the motion stability and control accuracy.By analysis the effects of the surface friction,the limits of gait speed and step length can be obtained.By analysis the influence of motor performance and robot structure gap,some methods is given to eliminate the influence.The trotting of quadruped robot is a rhythmic motion,the CPG as a controller to control the movement of biological rhythms is very effective to control the trotting from bionic central pattern generator.The Wilson-Cowan neural oscillator is as the basic neural oscillator to build the trotting CPG model,it turns out good rhythm signal output.By analysis controller parameters,the influences about the output in the values of the connection weights of the neural oscillator,oscillator initial,oscillator parameters and time constants are determinedA prototype of quadruped robot using VC++ 6.0 develops the motion control software is used for the trotting and stability control experiment.The results of trotting movement decomposition experiment in suspended state and ground trotting experiment show that the trotting planning can make the quadruped robot trot stability and the swing legs almost no impact to the floor,and the body of the quadruped robot is almost maintain the level and the direction of the moving is almost unchanged.