Showing papers by "Mohamed Elbestawi published in 1992"

Tool condition monitoring in turning using fuzzy set theory

Abstract: This paper presents a study on tool condition monitoring in turning using the fuzzy set theory. The tool conditions considered include tool breakage, several states of tool wear, and chatter. Force, vibration, and power sensors are used in this study to monitor the three components of the cutting force, i.e. acceleration of the tool holder in two perpendicular directions, and the spindle motor current respectively. A total of 11 monitoring indices (signature features) are selected to describe the signature characteristics of various tool conditions. A linear fuzzy equation is proposed to describe the relationship between the tool conditions and the monitoring indices. The proposed methodology is verified experimentally using a total of 396 cutting tests performed at 52 different cutting conditions. The proposed methodology is also compared with that of several classification schemes, including the K -mean and the Fisher's pattern recognition methods, the nearest neighbor method and the fuzzy C -mean method. The results indicate an overall 90% reliability of the proposed methodology for detecting tool conditions regardless of the variation in cutting conditions.

Analysis of the robotic disc grinding process

Abstract: Two major aspects of the robotic rigid disc grinding process, namely, disc wear and grinding forces have been examined in the present study. The disc wear is observed to be nonuniform, being greatest at the outer edge of the disc. A simple wear model has been developed by assuming that the amount of wear can be approximated as having a triangular cross section. The dynamic grinding force model developed includes the effects of disc wear and nonlinear stiffness of the robot system. Experiments have been conducted on an actual robotic grinding system to verify the validity of these system models. Several practical issues which should be considered during robotic grinding are discussed.

Surface finish in robotic disk grinding

Abstract: In spite of the various complexities, the ground surface during robotic grinding shows a definite and distinct surface texture. This paper presents a simple model for the surface finish produced during this process. The model is based on two simple assumptions. First is that though many grits remove material, the last grit that cuts largely in the ground surface determines the surface finish value. The second assumption is that the average shape of the active grit is spherical which generates a groove of parabolic cross section. The model is shown to be consistent with surface finish values measured experimentally during robotic rigid disk grinding and is able to predict the effect on surface finish to be expected when a given grinding variable is changed. It can be used for the purpose of process planning to improve the surface finish when desired.

Workpiece burn and surface finish during controlled force robotic disk grinding

Abstract: Workpiece burn and surface finish during robotic disk grinding are studied under controlled force conditions. Workpiece burn occurs due to gradual deterioration in the sharpness of active grains participating in the cutting process. This change in the sharpness of grains can be indirectly monitored by the change in the average coefficient of friction and average depth of cut. Both of these parameters gradually reduce with increasing disk wear due to attrition. In this paper, an analytical expression is derived which can be used to predict the occurrence of such burns during controlled force grinding. The experiments conducted under these conditions using a finely tuned PID controlled showed fair agreement with the predicted results. The experiments also showed that the surface finish gradually improves during successive passes. Hence, an attempt has been made to explain and predict this changing behaviour in the surface finish on the basis of gradual deterioration in the cutting efficiency of the disk. These relations can be used for practical optimization of the robotic grinding process.

Sensing and control for automated robotic edge deburring

Abstract: The authors describe the sensing and control elements of a system for automated robotic edge deburring. The deburring path, automatically generated by a task planner, is corrected online by an active end effector with the objective of controlling the chamfer depth. The sensing system combines the information from force and vision sensors during deburring to provide an improved depth measurement. The vision sensor is then used to verify the deburring performance in an inspection pass. The control system incorporates adaptive predictive control combined with learning control. The system was tested through computer simulations, and deburring experiments performed on one and two-dimensional edges. >