Intelligent control for the centreless grinding of compliant, thin walled cylinders
An advanced system was developed for the intelligent, self-optimising computer numerically controlled grinding of compliant, thin walled cylinders. A study was made of previous developments in the adaptive control of grinding processes. Requirements imposed on the design of computer control systems by the implementation of adaptive control techniques were considered. A manually controlled centreless grinding machine was automated and the mechanical capabilities of the machine were extended so that productivity was limited by process rather than machine constraints. In-process measurement was implemented to allow a control system to account for variations in process conditions. Experimental work performed with highly compliant workpieces exposed problems of process control that were accounted for by machine cycle design and process optimisation. It was considered that the improvements in productivity achieved by maximising material removal rates were limited for highly compliant workpieces. Therefore, a requirement for improving productivity through the design of appropriate machine cycles was identified. The design of a novel machine cycle eliminated the need for separate rough and finish grinding operations whilst allowing the control system to compensate for the high level of system compliance that was experienced. The benefits and disadvantages of the new machine cycle design were revealed by comparing the performance of the automated machine with that of manually operated machine tools. A conceptual framework for an intelligent control system was created that combined process models, learning strategies, process measurement and adaptive control techniques with an economic data base. The conceptual framework was used as a basis for the development of strategies that improved productivity when grinding highly compliant workpieces by the centreless grinding process. A control system was developed which successfully demonstrated the benefits of the approach. The control system was implemented within a commercial C. N. C. system and was put into production on the shop floor. A modular approach to the design of intelligent control systems for grinding processes is defined.