Dynamic modeling and control strategy for turning in place motion of a two-coaxial pendulums driven spherical inspector based on stick–slip principle

•The motion principle is analyzed which is particular for the structure of the robot.•The dynamic model is built with consideration of Coriolis Acceleration for accuracy.•Turning in place motion can be realized by the stick–slip based control strategy.•A cosine control function is constructed for smooth trajectory planning.

This paper proposes a turning in place motion control method for a two-coaxial pendulums driven spherical inspector, which is specially designed for inspection tasks. Compared with the traditional pendulum driven spherical robot, the drive unit of two coaxial pendulums brings novel motion principle of the inspector. The spherical inspector features turning in place motion which can enhance the mobility and the adaptation to the environment. The dynamic model of turning in place motion is derived in the light of the theory of moment of momentum. Considering the controllable rotation angle of turning in place motion, a stick–slip principle based control strategy is proposed and a cosine control function is constructed for smooth trajectory planning of the two pendulums. Finally, the effectiveness of turning in place control strategy is validated through both numerical simulation and prototype experiment.