Set Of Piezoelectric Actuators Research Articles

Effect of moisture on the sensing capabilities of piezoelectric actuator/sensor pairs on flax fibre reinforced composite laminates

The sensitivity of the piezoelectric actuators’ response to the moisture uptake has been investigated on flax fibre reinforced composite laminates. Non-woven flax fabric was impregnated with epoxy and composite laminates were fabricated using hand lay-up and cured in a compression moulding machine. The laminates were initially impacted with a drop-weight impact machine at a low energy level, with the aim to generate an artificial surface crack that will allow the moisture to enter the fibre-matrix interface more effectively. A set of piezoelectric actuators and sensors were adhered on the surfaces of the composite panels in a specific rectangular arrangement to allow for wave capturing at various directions. The wave characteristics of the samples were extracted in pristine stage and then the samples were impacted and immersed in distilled water until saturation. At regular intervals after the water immersion, the panels’ weight was measured using a laboratory scale and the wave propagation characteristics of the materials ware measured in order to investigate the gradual effect of moisture on the capabilities of the actuators and sensors. The propagation of stress waves in the dry and wet samples was investigated and the effect of moisture absorption was examined experimentally using piezoelectric wafers until the saturation was reached. Finally, a continuum damage mechanics layerwise time domain spectral finite element model, both for the composite laminate and the rich resin layers, was also developed to simulate the materials’ performance under impact and evaluate the wave propagation within the material at the dry state.

Influence of the tilt error motion of the rotation axis on the test of the equivalence principle with a rotating torsion pendulum.

Improving the precision of current tests of the equivalence principle with a rotating torsion pendulum requires a more complete analysis of systematic effects. Here, we discuss in detail one of the important systematic effects, the influence from the tilt error motion of the rotation axis of a rotary stage, namely, wandering of the instantaneous rotation axis around its average direction. Its influence on the rotating torsion pendulum is modeled phenomenologically, and the parameters in the model are calibrated. It is shown that the influence can contribute a correction of η ≈ 5 × 10-13 to the equivalence-principle violating parameter for a rotary stage whose tilt error motion of interest is about 31nrad in magnitude. We also show that such an influence can be reduced to the level of η ≈ 1 × 10-14 by means of active compensation of the tilt error motion using a set of piezoelectric actuators placed under the stage stator.

A piezoelectric screw-driven motor operating in shear vibration modes

In this study, a piezoelectric screw-driven motor operating in two shear vibration modes is proposed. The working mode of the motor is brand new. Low voltage is sufficient to drive the stator to drive the helical motion of the screw rod, in order to implement high-precision linear motion. The stator structure of this screw-driven motor is formed by obliquely placing four piezoelectric actuators in a four-side hollowed cubic elastic body. A through threaded hole was designed in the z-direction of the stator, exactly fitting the screw rod to be pushed. In the design processes of a screw-driven motor, the finite element analysis software ANSYS was used to analyze the vibration characteristics of the stator structure. The mutually orthogonal z–x and z–y shear vibration modes were designed using ANSYS. The two orthogonal vibration modes are driven by the sine voltage with phase difference between the two sets of piezoelectric actuators. Hence, the stator has elliptical trajectory at the threaded hole edge and drives the screw rod to simultaneously rotate and translate in the axial direction. In the experiment, the screw-driven motor prototype fabricated according to the designed results was measured; it showed that the translational velocity of the screw-driven motor is 2.137 mm/s when applying 16 V peak voltage without mechanical load. The translational velocity of the motor is 1.174 mm/s with 16 g mechanical load under 16 V peak voltage driving.

Modeling and optimization of a novel two-axis mirror-scanning mechanism driven by piezoelectric actuators

Mirror-scanning mechanisms are a key component in optical systems for diverse applications. However, the applications of existing piezoelectric scanners are limited due to their small angular travels. To overcome this problem, a novel two-axis mirror-scanning mechanism, which consists of a two-axis tip-tilt flexure mechanism and a set of piezoelectric actuators, is proposed in this paper. The focus of this research is on the design, theoretical modeling, and optimization of the piezoelectric-driven mechanism, with the goal of achieving large angular travels in a compact size. The design of the two-axis tip-tilt flexure mechanism is based on two nonuniform beams, which translate the limited linear output displacements of the piezoelectric actuators into large output angles. To exactly predict the angular travels, we built a voltage-angle model that characterizes the relationship between the input voltages to the piezoelectric actuators and the output angles of the piezoelectric-driven mechanism. Using this analytical model, the optimization is performed to improve the angular travels. A prototype of the mirror-scanning mechanism is fabricated based on the optimization results, and experiments are implemented to test the two-axis output angles. The experimental result shows that the angular travels of the scanner achieve more than 50 mrad, and the error between the analytical model and the experiment is about 11%. This error is much smaller than the error for the model built using the previous method because the influence of the stiffness of the mechanical structure on the deformation of the piezoelectric stack is considered in the voltage-angle model.

Swing-arm-type PZT dual actuator with fast seeking for optical disk drive

In this paper, a swing-arm-type dual positioning mechanism using a voice coil motor (VCM) and bimorph PZT actuators is proposed for the possible application to the future optical disc drive actuator. A VCM is used as a coarse motion actuator, and a set of piezoelectric actuators is used for fine motion. The two pairs of PZT actuators are arranged in parallel and are carefully designed to deflect in `S' shape such that tension and compression forces are generated simultaneously and thus the hysteresis is minimized. The static and dynamic analyses are performed and the parameter studies on the key dimensions of the set of PZT actuators are investigated. For fast seeking motion, time optimal control scheme combined with PD algorithm is adopted for the fast seeking motion of VCM. Positive position feedback (PPF) control is used to suppress residual vibration for the PZT actuator beams by activating it at the end of VCM swing motion. The feasibility of the suggested actuator system and the control scheme is demonstrated through simulations and experiments.

Study on the Sheet Escape and Feeding Mechanism Using Ultrasonic Vibration (1st Report) - Design Concept and Its Experimental Investigation -

This paper describes sheet feeding method and its design concept using the ultrasonic vibration actuator. The ultrasonic vibration is generated by two sets of piezoelectric actuators. It is an elliptic vibration mode, which rotates two vibration modes in the <I>Y-Z</I> and <I>X-Y</I> planes. This paper also presents a direct drive method using vibratory rotor and an indirect drive method using the idling rotor about sheet feeding mechanism, and it verifies theoretical relations between amplitude UZ1 and sheet feeding speed <I>VH</I> ,<I>VH</I>* and feeding force <I>FH</I> ,<I>FH</I>*. As a result of fundamental experiments, it was proved that a sheet, such as paper and telephone card, could be easily fed using either of their methods and a the highly reliable and compact sheet feeding mechanism could be obtained.