Control of a creeping snake-like robot

The mechanics of an autonomous snake-like robot comprised of a chain of discrete links is formulated. Creeping caused by a serpentine winding of a chain is considered. Winding is generated by internal bending moment between the links. The distribution of moment resembles a wave that propagates with increasing amplitude from the head to the tail. Movement of the chain on the ground generates friction that is described by a longitudinal and a transversal force with respect to a link. The transversal force is assumed to be much larger than the longitudinal one. Such dependence leads to propulsion of the robot in the forward direction if the winding of its body is properly controlled by internal bending moment. To show this, the nonlinear dynamic equations of the chain are solved numerically. Equations describe forces and moments exerted on links of the chain. External friction force, internal bending moment, and damping of flexural chain motion are taken into account. Parameters of internal bending moment were varied in order to find a region of stable movement and optimal propulsion with respect to average velocity in the forward direction. Stability of the creeping and movement of the chain head along an imposed trajectory is achieved by including the distance from the trajectory in control of internal bending moment. The performance of this locomotion and its control are demonstrated by calculated trajectories. The chain movement demonstrated resembles serpentine creeping of a real snake. The end goal of this research is to develop an endoscope capable of creeping and performing actions in complex environments such as interior of machines or biological organisms.