Control System Design for Active Vibration Control of a Turning Process Using PMN Actuators

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In recent years, intensive research has been conducted concerning the use of smart materials for active vibration control and also vibration attenuation for machine tools. This research merges the two research topics and investigates vibration control of a machining operation using actuators made of smart materials.

In this thesis, the effectiveness of using electrostrictive actuators for active vibration control during a turning process on a conventional engine lathe is investigated. The actuators are made of Lead Magnesium Niobate (PMN) and are in a multi-layered configuration. The test bed is a steel structure, called the Smart Toolpost. It is designed to be a key component of a conventional engine lathe machine tool and its purpose is to transmit compensating energy from the actuators to the tool tip during machining. The unique characteristics of PMN actuators to provide accurate displacements ensure the performance of vibration cancellation on the micron scale. The focus of this research is the design of a control system for performance optimization. This research combines both analytical and experimental approaches. In the analytical aspect, optimal, and adaptive control schemes are proposed. Mathematical models of the smart toolpost, based on first principles, are derived and evaluated. In the experimental aspect, system identification of the toolpost's dynamics as well as the actuator's dynamics is performed. Results from computer simulations are compared with the data obtained from machining experiments, showing good agreements.

Results from this thesis show that PMN actuators are good smart material, candidates for active vibration control. Optimal, and adaptive control, designs are critical to achieve effective broad band vibration compensation. This thesis gives a systematic presentation of the Smart Toolpost's system modeling, control system design, and real-time microprocessor implementation. But most of all, this thesis illustrates that the use of PMN ceramic material as actuators does indeed have practical applications in precision machining.