Active Control To Rotor Vibration With SMA

Shape Memory Alloy (SMA) is a new type of metal material. It has characteristics of shape memory, variable stiffness and super-elasticity. Because of these characteristics, the variable stiffness SMA bearing used in rotor system can be designed, and then the stiffness of system can be varied by active control technology when the rotate speed of system is near the critical rotate speed to reduce the maximum vibration amplitude of rotor system. In the paper, active control to rotor vibration with SMA is studied:1) The material performance of SMA , especially the coupled relation of strain, stress and temperature, is studied in nonlinear coupled thermoelasticity theory and the linear result is modified;2) The nonlinear dynamic behavior of rotor system with SMA bearing is studied in the nonlinear theory and the dynamic stability theory and the deference of the soft /hard nonlinear system is pointed out. The stability and bifurcation condition of rotor system are obtained and the way to improve system stability and reduce the vibration amplitude through adjusting system parameters is indicated;3) The strong nonlinear dynamic characteristic of high-speed rotor system is studied. The movement trend of system and the effect of system parameters to dynamic characteristic are indicated. The deference of the strong/weak nonlinear system and the unique characteristic of the strong soft-nonlinear system are pointed out;4) The bifurcation behavior of nonlinear rotor system is studied and the parameter region when chaos phenomenon is appeared is obtained in bifurcation and chaos theory. The way to eliminate chaos phenomenon through adjusting system parameters is indicated. The nonlinear dynamic behavior of journal bearing-rotor system in large parameter space is studied in numerical integral method and Floquet theory and the first and second bifurcation behavior of nonlinear rotor system are discussed;The concept is advanced that realizing the controllable nonlinear stiffness with SFD with the soft-nonlinear of SMA in the super-elasticity state to make the vibration amplitude of system always be in the small solution state to reduce the vibration amplitude of rotor system. The thermomechanics model of SMA5) spring and the close loop control system to reduce vibration through adjusting SMA temperature are set up. The discipline of optimum stiffness control, the optimum control force and the optimum control electric current are obtained;6) The concept of fuzzy control and time-varying control are introduced to reduce the vibration of rotor system. Gradient algorithm is introduced to solve the transient response problem caused by parameter varying with time in variable stiffness control of rotor system. The control discipline to eliminate transient response of rotor system is obtained. Finally, the vibration control effect of active control system is proved by emulation. The emulation results show that the active SMA control can reduce the vibration amplitude of system greatly, and the vibration amplitude of improved system is only 30% of the original one.