| Abstract: | A combined piezoelectric-hydraulic actuator system is developed for active vibration control of a rotorbearing system. The system configuration is designed by positioning the piezo-actuator remotely from the controlled structure and transmitting the control force via a hydraulic line and two pistons. Liquid plastic is employed as a transmission "fluid" to obtain high bulk modulus and low leakage. An acoustic measurement technique is used in predicting its bulk modulus. A modified piezohydraulic system also is developed by integrating the piezoelectric pushers and input pistons into a compact block which can provide x-y direction driving force. Copper tubing is chosen instead of stainless steel tubing for ease of assembly. The liquid plastic transmission fluid composition was adjusted to meet the following requirements: incompressibility and low viscosity in order to be used in a long, bending transmission tubing with better dynamic behavior for AVC. A new integrated multifunctional PID analog/digital controller was applied in the feedback control electronics. A significant reduction of vibration was achieved in the air turbine driven-dual overhung rotating test rig at NASA Lewis by this new piezohydraulic actuator system. A reliable closed loop AVC electromechanical simulation is essential for designing rotor systems supported by magnetic bearings. Accurate predictions of forced response, critical speeds and stability are required to assure machinery health and reliability. This research presents a general methodology which couples a finite element based model of the rotor with state space models of the sensors, control system and actuators. A least squares based algorithm is presented for obtaining the state space representation of the digital (DSP) controller, actuator, and power amplifiers from their measured frequency response functions. This general simulation method is illustrated by application to a cryogenic magnetic bearing test rig at NASA Lewis... |
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