Kinematics And Dynamics Of The Internal And External Driven Spherical Robots

Spherical robots are a new type of mobile robots with a global shell, and it can obtain the great steady ability after being imposed a disturbance, achieve the omnidirectional rolling, swerve agilely and never overturn. Being a breakthrough of the motion modes of traditional robots, spherical robots are one of the sbjects in great demand for the mobile robots' research.At present, much of spherical robots are driven by inside drive units that are difficult to solve the problem of supplying the enough power source for the robots system. In this paper, a kind of internal and external driven spherical robot is presented and its structural design, performance of overcoming obstacles, kinematics and dynamics analysis are mainly studied.At the beginning, the status in quo of the research on spherical robots was stated and the existing main problems followed. Then the internal and external driven spherical robot was chosen as the studied object. The spherical robot was designed based on the method of applying the robot-driven force couple caused by offseting the gravity center. And, it was driven mainly by the external wind force and had the internal motor as its sub-drive impetus. Using the theory of aerodynamics and statics, the static equilibrium equation of the spherical robot was built. According to the theory of moment balance, the constraint equations that described the performance of overcoming obstacles for the spherical robot was developed. With these equations, wind velocity, the slope angle of the terrain, the height of obstacles, the size and weight of the sphere and the ball-ground contact area were determined to be associated each other by some functions. Moreover, basing on the spherical robot's coordinate conversion described by the generalized Euler angles, its motion model was developed by using of the theorem of momentum moment. The dynamics model of the robot on a plane were established by using the theory of nonholonomic constraints and Lagrange-Routh equations. From this, the differential equations of dynamics for the robot motioning were deduced and the motion analysis programmes were composed. Several typical motion cases of the robot were illustrated and simulated by computer. Finally, the prototype of the internal and external driven spherical robot was produced. Several tests were made and obtained some experimental data. So, the correctness of the robot's motion model has been verified.