| The use of the shape memory alloy Nitinol wire is investigated as an actuator for enhancing the damping in structural vibration systems. Classical control and robust control laws for the single-input/single-output case are designed and implemented for a simple cantilever beam. Nitinol wire and a strain gage are used as the actuator and sensor, respectively. A finite element model of the beam is formulated and compared with experimental results. The numerical simulation of several closed-loop control systems is also determined in terms of a response to an initial-condition input and compared with the experimental results of real-time control. The time response of the closed-loop system demonstrates the excellent capability of Nitinol wire to damp out free structural vibration.; To demonstrate the capability of Nitinol wire with a robust controller for the multi-input/multi-output case, a three-mass structural system is designed and built. A finite element model is formulated and is verified experimentally. Strain gages are used as sensors for the three-mass system. Local strain information is used as a measured output and a state-variable model is formulated using the finite element model of the three-mass system. After the actuator dynamics is included into the system model, a robust controller is designed for a two-input/two-output case using the commercial software package MATRIXx. A numerical simulation is performed. Using a 386-based personal computer, a robust control algorithm is implemented. Significantly damped time responses of the closed-loop system are obtained experimentally, and compared with the open-loop response for the fundamental and second modes of vibration. |
