Detailed slip dynamics for nonholonomic mobile robotic system

These It is well known in the literature that wheeled mobile robot undergoes slip while moving through a flat surface, if certain conditions are violated. Slip is a very common phenomena present in all kind of wheeled mobile robotic system and particularly become prominent while taking a sharp bend on a flat ground. The degree of slip mainly depends on the wheel ground interaction properties at the contact point. Slip is absolutely undesirable as it consumes part of the system energy, erodes the wheel surface and also hampers the system performance and stability. While a system undergoes slip eventually it is very difficult to control the system and to get a proper estimate of system's position. It is very much essential to detect the slip when it is taking place and also to estimate the slip parameters with a set of specific sensors. Once the system undergoes slip it needs to go back to no-slip fulfilling certain conditions. The aim of this paper lies in formulating a detailed slip dynamics & its' solution for a differentially driven non-holonomic mobile robot. Certain switching conditions have been proposed for the transition from no-slip to slip & vice versa. The holonomic and non-holonomic constraints of slip and no-slip are taken into account in the model and when there is no slip then the constraints converge to no-slip constraints. A traction model for each wheel has been proposed which is a function of slip velocities. For motion simulation of WMR the traction model is used in conjunction with system dynamic equations. The simulation has been carried out with the data of a real robot and the simulation results illustrate its performance. Simulation results clearly show that the system dynamics is able to switch from slip to no-slip and vice versa.