Abstract
Abstract
Eliminating the gap between the grinding wheel and workpiece is a major time-wasting step during grinding operations. Reducing the time of this step has attracted many investigations. Several researchers have investigated the variation in some process parameters during the wheel-workpiece contact. These parameters include grinding force, grinding power and acoustic emission. During the approach of the grinding wheel to the workpiece, there are three primary stages which have an effect on these parameters: hydrodynamic stage, grit contact stage and wheel contact stage. A few researchers introduced a method to identify the start of the wheel contact stage, which is the practical contact stage. Most of these methods depend on predefined threshold values for some measured parameters. This paper introduces a new methodology to identify the wheel-workpiece contact event in surface grinding operations. A hybrid neural network with supervised learning is used to extract the contact event from the measured parameters. It consists of two neural nets. The first is a self-organizing map neural network with unsupervised learning and the second is a feedforward neural network with supervised learning. Using this hybrid network produces first self-organized clusters for the input data at the first network and then the second network recognizes these clusters. This results in the detection and classification of the contact events automatically from the measured data. This presents a very important step towards the full control of grinding operations in a computer numerically controlled (CNC) environment.
