Implementation of a Designed Tool Post for Tool Vibration Compensation Using PMN Actuators.

摘要

Tool vibration is a well-known cause of poor surface finish, accelerated tool wear, and unstable machining operations. Due to the availability of active or 'smart' materials, researchers in the machine tool industry are now focusing on applying active control to attenuate tool vibration during machining. In this thesis research, efforts are dedicated to investigating the mechanical and electrical behavior of a tool post structure in which lead-magnesium-niobate (PMN) actuators are used as built-in devices for vibration control. The research uses the finite element method (FEM) to identify the dynamic characteristics of the tool post, thus establishing an experimental test bed environment for experimental verification. The tool post is implemented in a shop floor machining environment to test its performance, both mechanically and electronically. The results obtained from this investigation justify the tool post design for its effectiveness in carrying out vibration compensation during machining. A 10% to 20% reduction in vibration was observed with the PMN actuators in action. The findings of the research include a 2 to 3 micrometer floating of the dynamic equilibrium position of the tool tip during compensation, and the effect of interplay between actuator-driving frequency and workpiece rotation on in-process compensation. Control of the coupling coefficient deserves special attention for maintaining an acceptable efficiency of conversion from electrical energy to mechanical energy. The knowledge gained from this study has provided guidelines not only for off-line optimization, but also for controller designs when PMN actuators are applied.