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ABSTRACT: Using high temperature X-ray diffraction, the thermal expansion coefficient (α) of a 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 ceramic is found to decrease from 4 × 10−5 C−1 to 3 × 10−6 C−1 on going from the cubic to the pseudocubic phase. The lattice stiffening indicated by this order of magnitude decrease in α occurs at a distinct temperature (Tα) which is some 80°C above the Tm temperature. Since the structural phase transformation is a necessary, but not sufficient, condition for the transition to the relaxor state, the relaxor region of the phase diagram must be reexamined by direct structural investigation.
Ferroelectric Letters. 08/2010; 2004(Vol. 31):55-61.
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ABSTRACT: A novel complementary clamp piezoworm stage was developed to be integrated into a two-axis configuration for tracking profiles in different size regimes. It is based on novel clamp designs that permit complementary action using the same flexure frame in a compact arrangement. A novel direct connection to a commercial slide was used to eliminate backlash and the need for high-precision alignment of a rod and slide. A model was developed and used to design the controller structure and choose thresholds for smooth operation. Complete assessment of the closed-loop performance of a single-axis and dual-axis stage in different regimes was done. The average positioning accuracy of the stage was plusmn20 nm. For tracking applications, the average error of the two-axis stage was 8 nm in the nanometer regime, 1.72 mum in the micrometer regime, and 1.85 mum in the millimeter regime.
IEEE/ASME Transactions on Mechatronics 01/2010; · 2.87 Impact Factor
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ABSTRACT: The concept of the complementary clamp piezoworm actuator with a diode-shunted delay circuit was experimentally verified through prototype testing. One clamp uses high voltage to grip and low voltage to release while the other clamp operates in reverse fashion. The resulting piezoworm actuator can be driven by a two-channel controller with the two clamps sharing the first channel and the extender piezoelectric stack using the second channel. The piezoworm achieved a speed of 440 mum/s and had a force capacity of 12.5 N when driven in open loop with trapezoidal waveforms. A delay circuit improved the force capacity from 12.5 to 14.7 N using a resistance of 1000 Omega. A closed-loop tracking controller was developed for the prototype. It is shown that the prototype closed-loop system has a repeatability less than plusmn20 nm for a 100 mum step input and can track a 100 mum, 0.05 Hz sine wave with a 1% peak error and less than a 200 nm average error.
IEEE/ASME Transactions on Mechatronics 01/2008; · 2.87 Impact Factor
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ABSTRACT: An inchworm actuator is described, which uses complementary configurations for the two clamping sections. In one configuration, clamping and release are achieved using high and low voltages, respectively, while for the other, clamping and release are achieved using low and high voltages, respectively. The resulting inchworm actuator can be driven by a two-channel controller with the two clamps sharing the first channel and the extender piezoelectric actuator using the second channel. The paper also describes a diode-shunted delay circuit that causes unclamping to occur more slowly than clamping. It is shown that by using the delay circuit in series with each clamp, the overall force drive capability of the actuator is increased. The paper presents simulated and experimental results of clamp force versus time during the switching transient. An analysis of a generalized delay circuit having both resistive and reactive elements shows that a purely resistive design provides the better tradeoff between increased force drive capability and power loss in the delay circuit.
IEEE/ASME Transactions on Mechatronics 07/2006; · 2.87 Impact Factor
