Piezo Bender Actuator Research Articles

Design of Piezoelectric Energy Harvester Generating Power over a Range of Excitation Frequencies Using

Today, there is a real desire to develop the piezoelectric ‎power harvester to enhance the performance of Wi-Fi sensors ‎and low-power devices to use them in heavy weather for longer times. In this study, the harvester model built from piezoelectric bimorphs called; “Piezo Bending ‎Actuators 427.0085.11Z” from Johnson Matthey, N42 ‎magnets, and some electrical parts such as; accelerometer, ‎shaker, HP 54601B oscilloscope used ‎in the ‏experimental setup‎. ‎
 The results show, that the system frequency has ‎an inverse relationship with a gap between magnets, where the ‎frequency increases 100% as the distance decreases from 4.6mm ‎to 0.7 mm‏.‏‎ In addition, the amplitude of increases by 104% as ‎the gap decreases from 4.6mm to 0.7 mm. Also, the ‎production power and amplitude have an inverse relation ‎with the magnet distance. ‎Keywords: power harvester, magnetic gap, tuned magnetic force, piezoelectric, resonances.

Investigations of applications of smart materials and methods in fluid valves and drives

In the paper the investigations performed at the Division of Mechtronic Devices at Poznan University of Technology in the area of application of both: smart materials in electro-hydraulic and electro-pneumatic valves, and new methods to control of hydraulic servo drives, are presented. In a first part the piezo bender actuator is shortly described and its application in servo valve is proposed. This actuator replaced the torque motor in the available on the market servo valve. The new valve simulation model is proposed. The simulation and investigations results of the servo valve with the piezo bending actuator are included. In the next part of the paper the application of piezo tube actuator in flapper-nozzle pneumatic valve is described. The test stand and investigations results are presented. Later, in the article, the Model Following Control (MFC) and Fractional order Control (FoC) methods are described. Their application in control of electrohydraulic servo drive is proposed. Some investigations results are included in the paper, showing the advantages of those control methods.

Piezo-bending actuators for isometric or auxotonic contraction analysis of engineered heart tissue.

Engineered heart tissue (EHT) has proven as valuable tool for disease modelling, drug safety screening, and cardiac repair. Especially in combination with the stem cell technology, these in vitro models of the human heart have generated interest not only of basic cardiovascular researchers but also of regulatory authorities responsible for drug safety. A main limitation of 3D-based assays for evaluating cardiotoxicity is their limited throughput. We integrated piezo-bending actuators in a 24-well system for the generation of strip-like rat and human EHT attached to hollow, elastic silicone posts. Muscle contractions of EHTs induced a measurable electrical current in the piezo-bending actuators that could be analysed for contraction amplitude, frequency, and contraction and relaxation kinetics. Compared with the standard video-optical analysis of contractile activity, the new system allows for (a) the analysis of several tissues in parallel, (b) switching between auxotonic and isometric contractions by inserting a stiff metal post in the silicone post opposing the piezo actuator, (c) continuous measurement over days with low data volume (megabyte), (d) automated measurement without the necessity of adjustment of tissue position for video-optical analysis, (e) reduced complexity and costs, (f) high sensitivity of contraction detection, (g) calculation of absolute contraction force, and (h) suitability for variable tissue geometries. The new set-up for contraction analysis based on piezo-bending actuators is a promising new method for the parallel screening of EHT for pharmacological drug effects and other applications of muscle tissue engineering (e.g., skeletal muscle engineering or cardiac repair).

Hexapod Hall scanner for high-resolution large area magnetic imaging.

We demonstrate a six-axis scanning imaging apparatus using piezo bending actuators with a large scan range. The six axes of motion of the bending actuators together with the coupling mechanism to the translation stage allow complete control of the sensor position and orientation over the scanning surface, which is ideal for the use of planar sensors such as Hall devices. In particular, the design allows for in situ correction of the probe tilt angle so that the sensor distance to sample surface can be minimized. We investigate the impact of this alignment on the quality of the measured data using an InSb Hall sensor and a magnetic sample. We also demonstrate a synchronous commutation setup that can greatly enhance the magnetic image by reducing the Hall signal offset.

Investigations of electronic amplifiers supplying a piezobimorph actuator

Piezoelectric bending actuators, also known as bimorphs, are characterized by very good dynamic properties and by displacements in a range of a few millimeters. Therefore these actuators are used in a wide range of applications. However their usage is limited because they require supplying amplifiers with output voltage of about 200V, which are rather expensive. This paper presents investigation results of such amplifiers with high voltage output. The model of a piezobending actuator is proposed and implemented in Matlab-Simulink software in order to simulate the behavior of the actuator supplied by the amplifiers. The simulation results are presented and compared with investigation results of high voltage amplifier used for supplying a piezoactuator. The influence of current limitation of operational amplifier on the actuator current is tested. Finally, a low cost audio power amplifier is proposed to control the piezobender actuator (as a cheaper alternative to the high-voltage amplifier) and its investigations results are presented in the paper.

Application of geometry based hysteresis modelling in compensation of hysteresis of piezo bender actuator

This paper presents results of studies of an application of a new method of piezo bender actuators modelling. A special hysteresis simulation model was developed and is presented. The model is based on a geometrical deformation of main hysteresis loop. The piezoelectric effect is described and the history of the hysteresis modelling is briefly reviewed. Firstly, a simple model for main loop modelling is proposed. Then, a geometrical description of the non-saturated hysteresis is presented and its modelling method is introduced. The modelling makes use of the function describing the geometrical shape of the two hysteresis main curves, which can be defined theoretically or obtained by measurement. These main curves are stored in the memory and transformed geometrically in order to obtain the minor curves. Such model was prepared in the Matlab–Simulink software, but can be easily implemented using any programming language and applied in an on-line controller. In comparison to the other known simulation methods, the one presented in the paper is easy to understand, and uses simple arithmetical equations, allowing to quickly obtain the inversed model of hysteresis. The inversed model was further used for compensation of a non-saturated hysteresis of the piezo bender actuator and results have also been presented in the paper.

Piezo films with adjustable anisotropic strain for bending actuators with tunable bending profiles

We present a method to produce in-plane polarized piezo films with a freely adjustable ratio of the strains in orthogonal in-plane directions. They can be used in piezo bending actuators with a tunable curvature profile. The strains are obtained as mean strains from a periodic polarization pattern produced by a suitable doubly interdigitated electrode structure. This mechanism is demonstrated for several examples using PZT sheets. We further discuss how this tuning and the parameters of the electrode layout affect the overall magnitude of the displacement.

Nanoscale intermittent contact-scanning electrochemical microscopy

A major theme in scanning electrochemical microscopy (SECM) is a methodology for nanoscale imaging with distance control and positional feedback of the tip. We report the expansion of intermittent contact (IC)-SECM to the nanoscale, using disk-type Pt nanoelectrodes prepared using the laser-puller sealing method. The Pt was exposed using a focused ion beam milling procedure to cut the end of the electrode to a well-defined glass sheath radius, which could also be used to reshape the tips to reduce the size of the glass sheath. This produced nanoelectrodes that were slightly recessed, which was optimal for IC-SECM on the nanoscale, as it served to protect the active part of the tip. A combination of finite element method simulations, steady-state voltammetry and scanning electron microscopy for the measurement of critical dimensions, was used to estimate Pt recession depth. With this knowledge, the tip-substrate alignment could be further estimated by tip approach curve measurements. IC-SECM has been implemented by using a piezo-bender actuator for the detection of damping of the oscillation amplitude of the tip, when IC occurs, which was used as a tip-position feedback mechanism. The piezo-bender actuator improves significantly on the performance of our previous setup for IC-SECM, as the force acting on the sample due to the tip is greatly reduced, allowing studies with more delicate tips. The capability of IC-SECM is illustrated with studies of a model electrode (metal/glass) substrate.

The VODKA Sensor: A Bio-Inspired Hyperacute Optical Position Sensing Device

We have designed and built a simple optical sensor called Vibrating Optical Device for the Kontrol of Autonomous robots (VODKA), that was inspired by the “tremor” eye movements observed in many vertebrate and invertebrate animals. In the initial version presented here, the sensor relies on the repetitive micro-translation of a pair of photoreceptors set behind a small lens, and on the processing designed to locate a target from the two photoreceptor signals. The VODKA sensor, in which retinal micro-scanning movements are performed via a small piezo-bender actuator driven at a frequency of 40 Hz, was found to be able to locate a contrasting edge with an outstandingly high resolution 900-fold greater than its static resolution (which is constrained by the interreceptor angle), regardless of the scanning law imposed on the retina. Hyperacuity is thus obtained at a very low cost, thus opening new vistas for the accurate visuo-motor control of robotic platforms. As an example, the sensor was mounted onto a miniature aerial robot that became able to track a moving target accurately by exploiting the robot's uncontrolled random vibrations as the source of its ocular microscanning movement. The simplicity, small size, low mass and low power consumption of this optical sensor make it highly suitable for many applications in the fields of metrology, astronomy, robotics, automotive, and aerospace engineering. The basic operating principle may also shed new light on the whys and wherefores of the tremor eye movements occurring in both animals and humans.

非对称光纤悬臂探头的驱动优化研究

非对称光纤悬臂探头的驱动优化研究

非对称光纤悬臂探头的驱动优化研究

非对称光纤悬臂探头的驱动优化研究

非对称光纤悬臂探头的驱动优化研究

非对称光纤悬臂探头的驱动优化研究

A hyperacute optical position sensor based on biomimetic retinal micro-scanning

Here we describe an active visual process whereby biomimetic micro-movements applied to an artificial retina improve the performances of a visual sensor in terms of both its detection sensitivity and its acuity. The elementary visual scanning sensor described here can detect a thin contrasting bar placed 2.5 m ahead, giving a minimum visibile (i.e., the smallest object width distinctly perceivable by the sensor) which is about 8-fold finer than the pixel angular pitch. In addition, the visual sensor is endowed with hyperacuity as it can locate a contrasting edge with a resolution which is 70-fold greater than its static resolution (i.e., the resolution without scanning). This high-resolution position sensing performance is based on encoding an angular position by an angular speed. The latter is then measured by a motion sensor inspired by those of the housefly. The retinal scanning process is generated by a piezo bender actuator driven at a frequency of 10 Hz by a tiny 1.5-g piezo driver. The small size, small mass and low power consumption of our visual scanning sensor make it well suited for a number of applications in fields ranging from mobile robotics to metrology and space technology, where the high-resolution contactless position sensing of naturally contrasting features is of prime importance.

Fabrication of a novel SEM microgripper by electrochemical and FIB techniques

A novel type of microgripper has been developed that uses combined electrochemical etching and focused ion beam milling techniques to fabricate microgripper end-effecters from a single piece of metal wire. This ensures that the two end-effecters have well-aligned faces, can be made in a relatively simple manner to a flexible/chosen design and can be made from a wide range of materials. The wire used here is tungsten which is easy to etch and allows the gripping force to be maximized. Independent electrical connections to each of the end-effecters allow them to be grounded to prevent charging in the SEM beam and give the option of applying a voltage across an object that is picked up. Actuation of the gripper is accomplished using a trimorph piezo bender actuator giving very good resolution (typically ∼170 nm V−1) and a maximum possible span range of over 20 µm. The gripper has been successfully demonstrated in picking up and placing individual copper microspheres and carbon nanotubes in situ in the SEM.

Two-dimensional scanning realized by an asymmetry fiber cantilever driven by single piezo bender actuator for optical coherence tomography

We develop a fiber based probe that is capable of two-dimensional scanning applicable in optical coherence tomography (OCT). Based on the resonance of the fiber cantilever with asymmetry structure which has two distinguished resonant frequencies in orthogonal directions, Lissajous pattern is produced suitable for two-dimensional scanning upon a sample. Orthogonal resonances of the fiber cantilever are simultaneously excited by single piezo bender actuator with one driving signal consisting of two components corresponding to above-mentioned two resonant frequencies. By integrating a backward-placed two-dimensional position sensitive detector (PSD) into the probe, real-time lateral position of the scanning pattern is registered simultaneously for image reconstruction. Dynamical characteristics of the fiber cantilever are experimentally studied with special consideration on factors determining the resolution of the scanning pattern, including frequency and amplitude ratios between two components of the driving signal and fetching duration used for an en face image. With the developed probe implemented in our established OCT system, en face OCT images of typical samples are obtained with satisfying resolution and contrast, demonstrating the feasibility of such fiber cantilever with asymmetry structure for realizing two dimensional scanning by single actuator, potentially applicable to endoscopic OCT imaging.

Depth-detection methods for microgripper based CNT manipulation in a scanning electron microscope

Current research work on the development of different depth-detection methods for supporting pick-and-place manipulations of carbon nanotubes (CNTs) in a scanning electron microscope (SEM) is presented. A nanorobot station capable of performing this manipulation task in the SEM’s vacuum chamber has been developed, consisting of two cooperating nanorobots. One robot carries an electrothermal microgripper and also performs the coarse approach between microgripper and CNT. The second robot serves as sample holder and realizes the fine positioning of the CNT sample. For a reliable fine approach between microgripper and CNT as well as an intended future automation of handling tasks, depth-detection methods are required in order to precisely measure and align the z-position of microgripper and CNT. Two different methods for z-position estimation are proposed. The depth from focus method uses the focusing information of SEM images whereas the touchdown sensor concept relies on a bimorph piezo bending actuator. The feasibility of both approaches is shown and first experimental results are discussed. Future work has to show how the proposed methods will increase the efficiency of nanorobotic manipulation and how these methods can advance the automation of nanohandling tasks.