Piezoelectric hydraulic hybrid actuator for a potential smart rotor application

A piezoelectric hydraulic hybrid actuator is proposed as a potential actuator for a trailing edge flap on a smart rotor. Piezoceramics are very attractive for the smart rotor concept due to their high energy density and electro-mechanical coupling. To optimally design systems based on piezoceramic actuators and sensors, accurate prediction of their response and power consumption is necessary. However, at present, experimental data as well as analytical tools in this regard are limited. Additionally, actuation capabilities of conventional piezoceramic actuators are often limited by their small stroke.; In order to address this issue, detailed experiments were conducted on PZT-5H piezoceramic sheet elements to identify their actuation, sensing and power consumption characteristics. The response of PZT-5H sheet actuators was measured under a variety of mechanical loadings and electrical conditions. Using this experimental data, a simple empirical model predicting the hysteretic free strain behavior of a PZT-5H sheet was developed. Calibration of piezoelectric strain sensors was performed along with the theoretical derivation and experimental validation of shear lag and transverse sensitivity correction factors. Power consumption of piezoceramic actuators was modeled and experimentally validated. Empirical correction factors to account for the nonlinear variation of material properties with applied electric field were identified. Additionally, the possibility of reducing the magnitude of current drawn by the actuator was investigated in conjunction with the novel use of a pseudo-inductor.; In order to obtain higher output stroke levels than that of conventional piezoceramic actuators, a hybrid device combining piezoceramic actuation and hydraulic power transmission was investigated. A prototype was designed to meet the requirements of a trailing edge flap on a section of a full scale MD900 rotor blade. The prototype was fabricated and tested, specifically concentrating on high pumping frequency operation. The device was actuated by two P-804.10 piezostacks in series, which had a total length of 36 mm and cross-sectional area 10 mm2. The device was tested up to a pumping frequency of 1 kHz, and achieved its maximum flow rate at a frequency of 300 Hz. Under uni-directional actuation, a blocked force of 33 lbs and a no-load velocity of 1.2 in/sec was measured. Under bi-directional actuation, at a frequency of 5 Hz, the amplitude of the output displacement was measured to be 32 mils under no external load, dropping to 15 mils under an external spring load of 180 lbs/in. The no-load output displacement amplitude drops to 12 mils at a frequency of 10 Hz.; It can be concluded that while the present prototype meets the requirements for a trailing edge flap actuator in terms of blocked force and quasi-static stroke, it does not have adequate bandwidth. In order to satisfy the bandwidth requirements, the flow rate at high pumping frequencies needs to be improved.