A systematic methodology to characterise the running-in and steady-state wear processes
An improved methodology has been developed to characterise running-in and steady-state wear processes. The experimental study was conducted with En 31 steel specimens on reciprocating tester with ball-on-flat geometry under lubricated sliding conditions. The tests were conducted according to a factorial design. The variables selected were the load, temperature and surface roughness. The wear behaviour for a given set of operating conditions has been characterised on the basis of developed methodology. The parametric influence of operating conditions was then analysed on the basis of polynomial relationships. The steady-state wear was found to be significantly influenced by the initial roughness.
This paper considers the problem of trajectory tracking control of a two-wheeled mobile robot in fixed time. By using the differential flatness property, the system model is linearized with several input transformations and an input prolongation. Then a feedback control law is designed to ensure the convergence of tracking errors in fixed time. The dynamic model with disturbances and unmodeled dynamics is also derived, and it is controlled in fixed time by designing a novel integral sliding mode surface. Theoretical results are finally verified by numerical simulations.