Adaptive Manoeuvring Control for Planar Snake Robots in Uncertain Friction Environments

The locomotion dynamics of a snake robot are greatly influenced by the way it interacts with its surroundings, particularly in terms of friction. Given the variable frictional characteristics of the environments in which holonomic snake robots locomote, this paper introduces a novel friction-adaptive body-shape controller that dynamically adjusts the robot's locomotion parameters in response to changes in friction. One of this paper's contributions is based on deriving a novel linear regression-based representation of the ground friction forces acting on the snake robot, which results in coupled dynamics between the gait tracking and friction parameter estimation errors. Using these coupled dynamics and our proposed friction adaptation law, we prove practical stability of the gait tracking and friction parameter estimation errors in the general case, as well as asymptotic convergence of the gait tracking errors and boundedness of the friction parameter estimation errors in a special case. Simulation results show that the proposed controller is stable and that the gait tracking error and friction parameter estimation errors are converging and bounded.