Most smart actuators exhibit rate-dependant hysteresis when the working frequency is higher than 5Hz. Although the Preisach model has been a very powerful tool to model the static hysteresis, it cannot be directly used to model the dynamic hysteresis. Some researchers have proposed various generalizations of the Preisach operator to model the rate-dependant hysteresis, however, most of them are application-dependant and only valid for low frequency range. In this thesis, a first-order dynamic relay operator is proposed. It is then used to build a novel dynamic Preisach model. It can be used to model general dynamic hysteresis and is valid for a large frequency range. Real experiment data of magnetostrictive actuator is used to test the proposed model. Experiments have shown that the proposed model can predict all the static major and minor loops very well and at the same time give an accurate prediction for the dynamic hysteresis loops. The controller design using the proposed model is also studied. An inversion algorithm is developed and a PID controller with inverse hysteresis compensation is proposed and tested through simulations. The results show that the PID controller with inverse compensation is good at regulating control; its tracking performance is really limited (average error is 10 micron), especially for high frequency signals. Hence, a simplified predictive control scheme is developed to improve the tracking performance. It is proved through experiments that the proposed predictive controller can reduce the average tracking error to 2 micron while preserve a good regulating performance.

Improved actuator point-to-point positioning performance, as measured by settling time, has been demonstrated in the context of manufacturing automation applications such as circuit board assembly and other product-transfer operations. The control objective is to move a single mass in a single axis from a starting position to a target position following the fastest possible motion trajectory while meeting final-position accuracy requirements. The actuator's achievable force that is available for acceleration is the fundamental variable that determines optimal settling time. The actuator technology employed is the linear variable reluctance motor. Mathematical motor models and simulation programs have been developed to perform several tasks necessary for demonstrating improved actuator performance: (i) optimal commutation under force ripple constraints has been computed to determine ripple-specified force limits and to provide excitation waveforms necessary for force production, (ii) motion profiles for several positioning task scenarios have been generated based on computed ripple-specified force limits, (iii) state space integral position control simulations have been performed to evaluate the degree of success of the proposed relaxation of force ripple constraints in improving settling time and (iv) the computed settling times for positioning tasks have been examined in relation to the copper losses associated with them in order to assess the trade-off. It has been shown that higher force capability is achieved when force-ripple constraints, which have been customarily emphasized in positioning applications, are relaxed. The higher capability is exploited by adopting faster motion trajectories, which are then imposed under feedback control to achieve faster settling time. Improved force capability with relaxed ripple constraints is demonstrated by generating average force versus speed capability curves under ripple constraints ranging from minimal ripple to unconstrained ripple. Improved positioning performance, with relaxed ripple constraints and without violating the final-position accuracy specification, is demonstrated by computing and comparing settling time for multiple positioning tasks with trajectories based on both extremes of force capability, lowest (no-ripple) and highest (unconstrained-ripple) force limits. The results have been demonstrated for two LVR motor configurations: one motor configuration represents typical (switched) linear and rotary variable reluctance motors while the other exhibits features of both switched and synchronous varieties of variable reluctance motors.

Piezoelectric and electrostrictive actuators composed of lead titanate zirconate (PZT) and lead magnesium niobate-lead titanate (PMN-PT) are important in a variety of engineering applications. A review of the literature indicated that published phase diagrams for the PMN-PT system are based primarily on temperatures of dielectric transitions. rather than direct measurements of structural changes. Structural transformations in the PMN-PT ceramic system have not been investigated at non-ambient temperatures for compositions with less than 0.29 PT. The review also revealed that crack growth in cyclic electric fields has been observed in only two compositions of PZT, while no crack initiation or growth is observed in a relaxor composition of PMN-PT. The X-ray diffraction results showed that the PMN-PT samples undergo multiple structural transformations on cooling through the temperature regions of their dielectric transitions. In compositions containing 0.0, 0.08, 0.10 and 0.20, an upper transformation temperature Ta, derived from a sharp change in coefficient of thermal expansion, lies well above the temperature Tm, of the observed maximum in dielectric constant. Lower structural transformation temperatures observed in these c compositions lie close to the freezing temperature Tf, below which ceramics exhibit remanent polarization. The temperatures of an upper structural transformation in PMN-PT ceramics with the higher PT mole fractions 0.30 and 0.35, agree closely with the Curie Temperature Tc. Cracks emanating from the corners of Vickers diamond indents in the soft piezoelectric ceramics BM532 PZT (Navy-Type VI) and PMN-0.30PT were increased in length when subjected to low frequency cyclic electric fields that were applied normal to the crack. Crack growth was observed in fields of 2-5 x Ec, but no new cracks were initiated when these higher fields were applied. Similar induced cracks in hard piezoelectric PZT ceramics, did not exhibit visible crack growth when subjected to low frequency fields with amplitudes up to +3.15 MV/m (1.6 x Ec), which is considered to be a safe maximum to avoid dielectric breakdown in PZT ceramics. No cracks were observed to emanate from the corners of either Vickers, or Knoop, diamond indents in samples of PMN-0.08PT. The intergranular cracks which emanate from the sides of the indents did not grow, and no new cracks were initiated, when the specimens were subjected to similar electric fields.

The dynamics of controlled transitory 2- and 3-D attachment of the separated flow over a 2-D airfoil model are investigated in wind tunnel experiments. Pulsed actuation is effected on time scales that are an order of magnitude shorter than the characteristic convective time scale of the base flow by momentary jets that are generated by a spanwise array of combustion-based actuators. The effects of the transitory actuation on the aerodynamic characteristics of the airfoil are assessed using measurements of the global lift force and pitching moment and of streamwise distributions of surface pressure, and planar and stereoscopic particle image velocimetry (PIV) acquired phase-locked to the actuation waveform. A single spanwise-bounded actuation pulse leads to 2-D severing of the separated vorticity layer and the subsequent shedding of a large-scale stall vortex that are followed by momentary attachment of the upstream boundary layer and ultimately re-separation that are accompanied by a strong transitory change in the airfoil's circulation. It is shown that the primary mechanism for the attachment is alteration of the adverse pressure gradient of the separated base flow by local blockage of the momentary jet and.the formation of the large-scale stall vortex. The disparity between the characteristic time scales of flow attachment and subsequent separation [O(Tconv) and O(10Tconv), respectively] is exploited for temporal and spatial extensions of the attachment and enhancement of the global aerodynamic performance using strings of successive actuation pulses. Pulsed actuation effected by an unbounded actuator array leads to spanwise spreading of the induced transitory 3-D flow attachment well beyond the spanwise edges of the actuators. It is shown that 3-D pulsed actuation enhances the accumulation of vorticity over the airfoil and improves its aerodynamic performance compared to 2-D, spanwise-bounded actuation. When the airfoil is undergoing time-periodic pitch oscillations beyond its static stall margin, a sequence of staged 3-D actuation pulses coupled to the airfoil's motion can lead to reduced lift hysteresis and increased pitch stability (lower “negative damping”) that are typically associated with the presence of dynamic stall.

Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Mechanical and Aerospace Engineering." Includes bibliographical references (p. 201-206).

Thesis (Ph.D.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references.

Thesis (M.App.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 99-101). Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: David B. Goldstein. Vita. Includes bibliographical references. Also available from UMI.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Zinn, Ben T.; Committee Member: Book, Wayne; Committee Member: Glezer, Ari; Committee Member: Neumeier, Yedidia; Committee Member: Seitzman, Jerry.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 325-341). Available also in a digital version from Dissertation Abstracts.