FLANK WEAR ESTIMATION UNDER VARYING CUTTING CONDITIONS

A model-based methodology, designed to operate under varying cutting conditions, for on-line estimation of flank-wear rate based on cutting force measurements is introduced. The key idea is to employ a model of the relationship between force and flank wear, together with on-line parameter estimation methods. This permits separation of the direct effect of changing cutting conditions on force from the indirect effect where changing cutting conditions affect the wear which, in turn, affects the force. Simulation results confirm the effectiveness of this strategy for turning with varying speed, feed, or depth of cut. Experiments, conducted for turning operations with a varying depth of cut, show good agreement between estimated wear values and the actual values of tool wear measured intermittently during the cut.

Sliding Modes Control in vehicle longitudinal dynamics control

Sliding Mode Control is a nonlinear control methodology based on the use of a discontinuous control input which forces the controlled system to switch from one continuous structure to another, evolving as a variable structure system. This structure variation makes the system state reach in a finite time a pre-specified subspace of the system state space where the desired dynamical properties are assigned to the controlled system. In the past years, an extensive literature has been devoted to the developments of Sliding Mode Control theory. This kind of methodology offers a number of benefits, the major of which is its robustness versus a significant class of uncertainties and disturbances. Yet, it presents a crucial drawback, the so-called chattering phenomenon, which may disrupt or damage the actuators and induce unacceptable vibrations throughout the controlled system, limiting the practical applicability of the methodology, especially in case of mechanical or electromechanical plants. This drawback has been better studied recently. Theoretical developments, oriented to increase the order of the sliding mode, thus producing efficient Second Order and Higher Order Sliding Mode Control algorithms, may be useful to attenuate the drawbacks caused by the use of a discontinuous control. Then, Sliding Mode Control can be profitably used to efficiently solve automotive control and observation problems, as testified by several recent publications and research projects. The aim of this chapter is to provide an overview of available examples of application of sliding mode control to the automotive field, focusing on recent developments at the University of Pavia