PZT Bimorph Actuators Research Articles

A streamlined fabrication process for high energy density piezoelectric bending actuators

Fabrication of high-performance actuators is often a bottle-neck in the creation of microrobots. In this work, we present a new approach to piezoelectric bimorph actuator fabrication that simplifies the process (in part by reducing the number of materials used) without sacrificing actuator performance. We fabricate PZT bimorph actuators with two active layers, as well as bimorphs with four active layers that are under 2 mm wide – these are more challenging to fabricate than the two-layer bimorphs and thus present a useful test case for our new process. The blocked force and free deflection of the actuators agrees well with expected performance, with energy densities of approximately 1.2 J/kg at electric fields of 1.67 V/µm. We expect this process to enable rapid fabrication of piezoelectric actuators with more layers and at smaller scales than was previously attainable.

Piezoelectric Actuators for Tactile and Elasticity Sensing

Piezoelectric actuators have achieved remarkable progress in many fields, being able to generate forces or displacements to perform scanning, tuning, manipulating, tactile sensing or delivering functions. In this work, two piezoelectric PZT (lead zirconate titanate) bimorph actuators, with different tip contact materials, were applied as tactile sensors to estimate the modulus of elasticity, or Young’s modulus, of low-stiffness materials. The actuators were chosen to work in resonance, taking advantage of a relatively low resonant frequency of the out-of-plane vibrational modes, associated with a convenient compliance, proven by optical and electrical characterization. Optical measurements performed with a scanning laser vibrometer confirmed that the displacement per applied voltage was around 437 nm/V for the resonator with the lower mass tip. In order to determine the modulus of elasticity of the sensed materials, the stiffness coefficient of the resonator was first calibrated against a force sensor, obtaining a value of 1565 ± 138 N/m. The actuators were mounted in a positioning stage to allow approximation and contact of the sensor tip with a set of target materials. Electrical measurements were performed using the resonator as part of an oscillator circuit, and the modulus of elasticity of the sample was derived from the contact resonant frequency curve of the cantilever–sample system. The resulting sensor is an effective, low-cost and non-destructive solution compared to atomic force microscopy (AFM) techniques. Materials with different modulus of elasticity were tested and the results compared to values reported in the literature.

Enabling PZT bimorph actuator with passive polysilicon structure

For the first time, a bimorph thin film lead zirconate titanate (PZT) micro-actuator with thick polysilicon as a passive structural layer is reported. A simple micro-cantilever actuator consisting of 1000 µm long and 250 µm wide with 4 µm thick polysilicon structure flanked by a piezoelectric active layer on the top and bottom side has been fabricated to demonstrate such novel bimorph configuration. The actuator displays a flat profile with only 2 µm of tip deflection which indicates a balanced stress distribution in the structure. It is driven alternatively in both directions, demonstrating its unique suitability for micro-actuation mechanisms where a passive structural layer is required to enhance the mechanical performance and reliability of the system. The static and dynamic measurements show similar characteristics for the top and bottom actuation. The actuator has a measured resonance frequency of 6.3 kHz, and displacement voltage sensitivities of 17.9 and 25.6 nm/V in the upward and downward direction, respectively.

J0440201 位相シフト電圧によるバイモルフアクチュエータの擬似変形波駆動

In the present paper, phase-shifted voltage was applied to discrete electrodes of PZT bimorph actuator in order to derive pseudo-wave deformation. The behavior of deformation of the actuator was calculated by the 3-D FEM piezoelectric analysis. In the model dimensions, thickness was 0.7mm and the wavelength of the deformation wave was 30mm. The AC Voltage of 200V amplitude was applied to the parallel-type bimorph actuator. From the calculated results, it appeared that amplitude of the wave deformation along center was maximum and that along the free-edge was minimum. It was also shown that the curvature in the width direction decreased when width increased. From these results, wide-width design was necessary for manufacturing high-performance actuators.

Design of a waveform tracking system for a piezoelectric actuator

In this work an adaptive model-based predictive control (AMPC) is designed for high-frequency waveform tracking by a PZT bimorph actuator in industrial vibratory feeding. Since the actuator has a narrow bandwidth and significant dynamic hysteresis, the waveform tracking process contains both linear and non-linear errors and the coupling effect between these two needs to be considered before effective compensation can be implemented to obtain a precise vibration trajectory. In the adaptive control, two parallel loops were employed, a linear compensation loop and a non-linear offset loop, to suppress the hybrid errors and let the error eventually converge to an acceptable level by iteration. Since the system varies much more slowly than the control loops, a quasi-time invariant system is assumed in the modelling process and a single-layer neural network is used to compensate the system floating adaptively. Due to the fact that in this application the smoothness of the actuator motion waveform is of critical importance to ensure the mechanical force configuration required in industrial application, each driving waveform must be adapted as a whole, not as a series of discrete input points. Therefore instead of applying a set-point tracking method, a self-tuning process is used in the predictive filter design of the current cycle, and corresponding control is delayed to waveform generation of the next cycle. The control algorithm is then implemented into experiment for vibratory feeding and the result shows satisfactory hysteresis suppression and good waveform tracking.

Vibration Control of Piezoelectric Actuator by Implementation of Optical Positioning Sensor

PZT bimorph actuator is used to design mini-sized vibratory feeder applied in the micro-medical industry. Since the vibration trajectory of PZT bimorph actuator will be controlled to obtain desired parts feeding, optical positioning sensor is used to provide non-contact measurement with precise displacement. Because the torsional vibration causes the rotary motion of the actuator, the angle between the optical sensor and the PZT plate is subjected to change during the vibration procedure. Optical loss due to a varying reflection angle is compensated by multiple-segment micrometer calibration. Satisfactory hysteresis suppression and good waveform tracking is obtained with implementation of optical sensor in piezo-actuating system.

PZT bimorph actuated atomizer based on higher order harmonic resonance and reduced operating pressure

This paper presents the design, fabrication and testing of a PZT bimorph actuated atomizer. The atomizer with the size of 43 mm × 37 mm × 7 mm is composed of a PZT bimorph actuator, which is sandwiched by top and bottom flow channel plates and cover shields. The micronozzle plate is attached onto the top cover shield. UV laser machining and micro electrical discharge machining (μEDM) are applied to fabricate the micronozzles with different geometry. The experimental results indicate that we can justify the frequency response of flow rate by acoustic pressure analysis. The peak flow rates occur at higher order resonances, and the operating pressure is less than 0.1 MPa, which is much lower than that of existing atomizers. Also, the influence of flow rate by changing the distance between the PZT bimorph and the nozzle plate, as well as the flat plate on the bottom cover shield are discussed. The maximum flow rate of 8 ml/min is obtained by using the μEDM-made micronozzle plate, when the atomizer is driven with square pulses at 7 kHz with 50% duty cycle and 27 V peak-to-peak.

Optimal energy density piezoelectric bending actuators

The design and analysis of piezoelectric actuators is rarely optimized for low mass applications. However, emerging technologies such as micro air vehicles, and microrobotics in general, demand high force, high displacement, low mass actuators. Utilization of generic piezoceramics and high performance composite materials coupled with intelligent use of geometry and novel driving techniques yields low cost, rapidly prototyped, ultra-high energy density bending actuators for use in such applications. The design is based upon a laminate plate theory model for a stacked multimorph cantilever actuator, encompassing all possible layups, layer anisotropies, internal and external excitations, and intrinsic and extrinsic geometries. Using these principles, we have fabricated 12 mg PZT bimorph actuators with greater than 2 J kg −1 energy density. This gives a performance increase of an order of magnitude or greater compared to existing commercially available piezoelectric bending actuators.

Design and Construction of a Piezoelectric Point Actuated Active Aperture Antenna

In this research, an antenna’s far field radiation pattern is controlled by controlling the shape of a sub reflector in a Cassegrain antenna system. The antenna is actuated using multiple point actuators in contact with the reflector surface. A lead sarcomata titan ate (PZT) stack coupled with a friction-based compliant mechanism gives the point actuators used in this design an advantage over similar studies using PZT bimorph or PAD actuators. The main advantage stems from the fact that the displacement can be maintained without the continuous application of voltage. An electromechanical model is used to describe the motion of the stack, and the friction based compliant mechanism is modeled similar to power screw-type actuators. A combined finite element-electromagnetic analysis code is used to determine the desired shape of the reflector and the corresponding actuator displacements. The final shape of the reflector is verified using stereo photogrammetry.