Design of a piezoelectric tool for active control of cutting forces in machining
Date
2002
Authors
Tzonev, Nikolay
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Abstract
The work presented in this thesis describes the design, implementation, and testing of a novel 1-DOF piezoelectric-actuated device that is intended to operate as a platform for future realization of various chatter suppression control strategies. The common practice of introducing viscoelastic treatments to dynamically unstable systems is not suitable for applications such as chatter suppression where the cause of the vibrations cannot be properly predicted and simulated. In these cases, active vibration cancellation and prevention technology can sense, isolate, and damp vibrations or noise.
The new device employs a piezoelectric translator acting upon a drum. The design allows for two modes of operation that are functionally separated by a preset internal preload. The first mode of operation is passive and, for as long as the system sensors register contact and the cutting forces remain steady, no active control is attempted.
When the original preload is overcome by the presence of a large external cutting force, the device reacts in a way that counter-acts and stabilizes the external disturbance. The system was found suitable for dynamic control applications within a [0,700] Hz bandwidth. Dynamic tests of the device indicated satisfactory output force characteristics with rapid force degradation outside the upper bandwidth boundary. The assembly was tested with a ShopTask Shopmaster 2000 combination mill/lathe.
This work confirms the feasibility of using piezoelectric sensors and actuators for designing machine-chatter suppression devices that can operate within practical frequency bandwidths. The innovative approach of installing the piezoelectric actuator in series with the active element, rather than the traditional shunted configuration, proved to be capable of delivering the desired dynamic characteristics necessary for implementing future chatter suppressing control strategies.