Showing papers on "Piezoelectric motor published in 2014"

Rotational piezoelectric wind energy harvesting using impact-induced resonance

Abstract: To improve the output power of a rotational piezoelectric wind energy harvester, impact-induced resonance is proposed to enable effective excitation of the piezoelectric cantilevers' vibration modes and obtain optimum deformation, which enhances the mechanical/electrical energy transformation. The impact force is introduced by forming a piezoelectric bimorph cantilever polygon that is fixed at the circumference of the rotating fan's internal surface. Elastic balls are placed inside the polygon. When wind rotates the device, the balls strike the piezoelectric cantilevers, and thus electricity is generated by the piezoelectric effect. The impact point is carefully chosen to use the first bending mode as much as possible, and thus maximize the harvesting efficiency. The design enables each bimorph to be struck in a similar area and every bimorph is struck in that area at different moments. As a result, a relatively stable output frequency can be obtained. The output frequency can also be changed by choosing different bimorph dimensions, which will also make the device simpler and the costs lower. A prototype piezoelectric energy harvester consisting of twelve piezoelectric cantilevers was constructed. The piezoelectric cantilevers were made from phosphor bronze, the lead zirconium titanate (PZT)-based bimorph cantilever had dimensions of 47 mm × 20 mm × 0.5 mm, and the elastic balls were made from steel with a diameter of 10 mm. The optimal DC output power was 613 μW across the 20 kΩ resistor at a rotation speed of 200 r/min with an inscribed circle diameter of 31 mm.

Energy harvester array using piezoelectric circular diaphragm for broadband vibration

Abstract: A piezoelectric generator fabricated by multiple circular diaphragm piezoelectric harvesters array is provided to harvest power over a broad range of frequencies. Four harvesters with varies tip masses are incorporated on a board with an area of 98 × 98 mm2. In this case, four strong output power peaks are obtained over frequencies from 120 Hz to 225 Hz. With an optimum load resistance of 15 kΩ, the value of four output power peaks is, respectively, 5.14, 6.65, 9.7, and 10 mW for the generator under an acceleration of 9.8 m/s2. By choosing an appropriate combination of tip masses with piezoelectric elements in array, the frequency range of energy harvesting can be obviously widened to meet the broadband vibration.

Magnetic plucking of piezoelectric beams for frequency up-converting energy harvesters

Abstract: In the field of energy harvesting from low-frequency random excitation, a technique known as piezoelectric beam plucking or frequency up-conversion has seen increasing interest. This paper presents an experimentally validated model to calculate the voltage response and power output when actuating piezoelectric beams via a pair of magnets. Using magnetic coupling avoids impact on the brittle piezoceramic material. The relevant equations are derived for the piezoelectric beam, and two different approaches to include the magnetic interaction are presented and discussed. After comparing the models to experimental results, their use in predicting the response to changes in the system, e.g. using thicker magnets, and determination of the optimal load resistance and power output with regards to frequency, are investigated.

Micro ultrasonic motor using a one cubic millimeter stator

Abstract: Ultrasonic motors are expected to be used as micro-actuators, and the miniaturization of these devices is an interesting subject. We present a micro ultrasonic motor using a stator with a volume of approximately 1 mm 3 , which is one of the smallest ultrasonic motors. The stator consists of a metallic cube with a through-hole and piezoelectric elements adhered to its sides; the simplicity of the stator allows it to be miniaturized without special machining processes. The vibration mode that the stator generates for rotation is three waves around the circumference of the hole. This vibration mode can generate certain vibration amplitudes and driving torques even when the stator is miniaturized. In this paper, we build a prototype micro ultrasonic motor and examine its basic characteristics, including impedances and vibration amplitudes. The basic motor performance, such as its torque and rotational speed, is demonstrated experimentally.

A small linear ultrasonic motor utilizing longitudinal and bending modes of a piezoelectric tube

Abstract: A small linear ultrasonic motor which consists of a piezoelectric ceramic Pb(Zr,Ti)O3 (PZT) tube (outside diameter 5 mm, inside diameter 3 mm, length 15 mm, acts as stator) and a shaft (acts as slider) has been developed. The outer surface electrode of the PZT tube is divided into 4 parts to excite longitudinal-bending (L1-B2) modes, which could be then used to produce linear motion. The motor shows a high power (force) density. It has a no-load speed of 0.14 m/s, a stall force of 0.3 N, and a maximum output power of 9.3 mW under an applied voltage of 100 Vpp. The method for further improving the performance has been discussed. The proposed motor can be further miniaturized because of its simple structure, and it has potential to be applied to medical microrobots, endoscopes, or micro laparoscopic devices, etc.

Adaptive control of a fiber scanner with piezoelectric sensing

Abstract: Improved systems, methods, and devices relating to optical fiber scanners are provided. In one aspect, a scanning apparatus includes an optical fiber and a piezoelectric actuator coupled to the optical fiber to deflect a distal end of the optical fiber in a scanning pattern. The apparatus can include drive circuitry coupled to the piezoelectric actuator, sense circuitry electrically coupled to the piezoelectric actuator and the drive circuitry to determine displacement of the piezoelectric actuator, and a processor coupled to the drive circuitry and the sense circuitry to drive the piezoelectric actuator in response to the displacement.

Resonant-type inertia linear motor based on the harmonic vibration synthesis of piezoelectric bending actuator

Abstract: Traditional piezoelectric inertia motors are generally driven at the quasi-static frequency range, which results in a relatively slow moving speed. In this paper, a piezoelectric bending actuator was designed for a resonant-type inertia linear motor. The driving mechanism of the actuator was also studied. The actuator's movement in a periodical sawtooth-shaped waveform was generated by composing two sinusoidal resonant bending vibrations with a frequency ratio of 1:2. A prototype inertia motor was fabricated. Experimental results confirmed the effectiveness of the design. The no-load maximum speed was 28.2 mm/s with drive voltage of 300 Vp–p for a base frequency of 587 Hz. At a preload force of 9.6 N and a driving voltage of 400 Vp–p for the base frequency, the linear speed was 18.5 mm/s with 0.02 N drag load. The moving direction could be reversed by changing the driving voltage's phase.

An analytical solution for curved piezoelectric micromachined ultrasonic transducers with spherically shaped diaphragms.

Abstract: An analytical solution for piezoelectrically actuated spherically shaped diaphragms has been developed to study their dynamic behavior with targeted applications in piezoelectric micromachined ultrasonic transducers (pMUT). The analytical model starts with a curved pMUT composed of a piezoelectric diaphragm with a nominal radius in size, a radius of curvature in shape, and under both possible actuation sources of radial pressure and electric potential. The diaphragm has the piezoelectric material polarized in the direction perpendicular to its surface and sandwiched between two metal electrodes. When an electric field is applied between the two electrodes, the in-plane piezoelectric strain can cause larger out-of-plane deflections than a flat unimorph piezoelectric diaphragm because of the diaphragm's spherical curvature with a clamped periphery for high electromechanical coupling factor. Key performance parameters, including mechanical mode shapes, resonant frequencies, dynamic responses, and displacements, with respect to the curvature and size of the diaphragm have been investigated. Both analytical derivations and numerical simulations using finite element analysis have been performed for the optimal design of the electromechanical coupling factor, with varying factors such as mechanical resonant frequency, radius of curvature, nominal radius, and thickness. As such, this work provides theoretical foundations for the design of curved pMUTs with high electromechanical coupling factor compared with planar-shape pMUTs.

Non-contact piezoelectric rotary motor modulated by giant electrorheological fluid

Abstract: A bidirectional non-contact rotary motor using a piezoelectric torsional vibrator and the giant electrorheological (GER) fluid is described in this paper By applying the dynamic electric signal with a square waveform to the GER fluid, which is in phase with the vibration velocity of the torsional vibrator, bidirectional rotation at an excitation frequency of 118 Hz is achieved This motor generates 104 mN m torque when the electric field strength of 2 kV/mm with 30% duty cycle is applied to the GER fluid, and the rotational speed of up to 714 rad/s is achieved if the electric field strength is increased to 25 kV/mm Similarities and differences of the motor characteristics between this motor and the conventional standing wave ultrasonic motors are discussed The motor performance is not ideal under high electric field strength, indicating that the response time of the GER fluid is dependent on the electric field strength

A piezoelectric direct-drive servo valve with a novel multi-body contacting spool-driving mechanism: Design, modelling and experiment

Abstract: Stack-type piezoelectric actuators, which usually consist of several ceramic layers connected in series, are widely used in piezoelectric direct-drive servo valves (PDDSV). However, poor pulling force capacity of this kind of actuators affects the performances of the direct-drive servo valves. This article presents a new type of PDDSV, whose spool-driving mechanism is composed of a set of independent parts that are not fixed together but are in contact with each other. This multi-body contacting spool-driving mechanism provides bidirectional movement of the spool by a preloaded stack-type piezoelectric actuator and a driving disc spring. This prevents the stack-type piezoelectric actuator from bearing the pulling force due to the inertia and friction of the spool. Design of the proposed servo valve is illustrated in detail and its characteristics are also predicted. Based on a nonlinear dynamic model of the multi-body contacting spool-driving mechanism, a comprehensive dynamic simulation model of the prop...

Improving the accuracy of walking piezo motors

Abstract: Many application areas require ultraprecise, stiff, and compact actuator systems with a high positioning resolution in combination with a large range as well as a high holding and pushing force. One promising solution to meet these conflicting requirements is a walking piezo motor that works with two pairs of piezo elements such that the movement is taken over by one pair, once the other pair reaches its maximum travel distance. A resolution in the pm-range can be achieved, if operating the motor within the travel range of one piezo pair. However, applying the typical walking drive signals, we measure jumps in the displacement up to 2.4 μm, when the movement is given over from one piezo pair to the other. We analyze the reason for these large jumps and propose improved drive signals. The implementation of our new drive signals reduces the jumps to less than 42 nm and makes the motor ideally suitable to operate as a coarse approach motor in an ultra-high vacuum scanning tunneling microscope. The rigidity of the motor is reflected in its high pushing force of 6.4 N.

Optimal Design of Piezoelectric Cantilevered Actuators With Guaranteed Performances by Using Interval Techniques

Abstract: Piezoelectric materials are well recognized for the development of systems and actuators working at the micro/nano-scale such as microsystems. This recognition is thanks to the high resolution, high bandwidth, and high force density that they can offer. However, piezoelectric actuators are typified by low range of displacement relative to other actuators like magnetic or thermal actuators. To obtain the sufficient range of displacement with a piezoelectric actuator, either we use high input voltages or we redesign the actuator to have larger dimensions. The former solution may lead to the destruction of the actuators and the latter is not congruent with the objectives of microsystems where the dimensions should be miniaturized. Furthermore, increasing the dimensions of the actuators reduces their rapidity and bandwidth. This paper proposes an approach based on interval analysis to design piezoelectric actuators with cantilever structures. The aim consists in reducing their dimensions while still satisfying some specified performances in term of output range and in term of resonant frequency (and thus bandwidth). The problem of the design is formulated as a set-inversion problem which can be solved using interval techniques. The obtained results, validated with prototype fabrication and experimental characterization, demonstrate the efficiency and the interests of the proposed method for designing systems and actuators working at the micro/nano-scale in general.

Millipede-inspired locomotion through novel U-shaped piezoelectric motors

Abstract: We report a novel piezoelectric motor that operates at a resonance frequency of 144 Hz, much lower than that of conventional ultrasonic motors, and meets the displacement and gait requirements for designing the locomotion mechanism of a millipede-inspired robot (millibot). The motor structure consists of two piezoelectric bimorphs arranged in a U-shaped configuration. Using the first bending mode for both the piezoelectric bimorphs an elliptical motion was obtained at the tip which led to the successful implementation of millipede inspired locomotion. At an input voltage of 70.7 Vrms, the piezoelectric motor operating at resonance frequency was able to generate torque of 0.03 mN m, mechanical power of 0.84 mW and maximum velocity of 62 rad s−1. Detailed discussion is provided about the principle of operation of the millibot.

Resonance frequency ratio control with an additional inductor for a miniaturized resonant-type SIDM actuator

Abstract: A smooth impact drive mechanism (SIDM) is one type of piezoelectric actuator that converts a saw-shaped piezoelectric displacement to linear (or rotational) motion. For sufficient displacement, a soft-type multilayered piezoelectric element is essential; however, such a piezoelectric element prevents efficient driving due to its low quality factor. To overcome this problem, we proposed a resonant-type SIDM using a hard-type single-layered piezoelectric element. In this resonant-type SIDM, the first and third longitudinal resonant sinusoidal vibration modes were combined to obtain a quasi-saw-shaped waveform. To realize such a saw-shaped waveform, precise adjustment of the resonance frequency ratio is essential. However, it is not easy to regulate the resonance frequency ratio by just the transducer design because of the fabrication error. As a solution for this issue, this study proposes to adjust the frequency ratio by inserting an electrical inductor in series with the piezoelectric transducer. With this method, the resonance frequency ratio was controlled, and the rotor velocity increased as expected.

Piezoelectric vibration sensor for monitoring machinery

Abstract: A vibration sensor includes a piezoelectric crystal; and a base having an upper surface and a lower surface, the piezoelectric crystal attached to the upper surface of the base, the base defining a notch in at least one of the upper surface and the lower surface. Another embodiment of a vibration sensor includes a first piezoelectric crystal; a second piezoelectric crystal; a base attached to the first piezoelectric crystal on first side of the base and attached to the second piezoelectric crystal on a second side of the base opposite the first side of the base; a voltage amplifier in electrical communication to the first piezoelectric crystal; and a charge amplifier in electrical communication to the second piezoelectric crystal.

A bio-inspired piezoelectric motor with simple structured asymmetric stator

Abstract: A new type of micro rotary motor with a single piezoelectric stack actuator has been proposed, developed and tested. The conventional principle of elliptical motion is realized by a proposed mechanism which utilizes a Y-shaped stator and a ring rotor, and the biomimetic gait of an inchworm is achieved by integrating one piezoelectric stack actuator into the stator. The performance of the motor is predicted on the basis of computational simulation. An experimental setup was built to validate the working principles and evaluate the performance. Preliminary results have verified the working principle. Differences between the measured and predicted performances of the motor are analyzed.

Modeling and nonlinear analysis of a micro-switch under electrostatic and piezoelectric excitations with curvature and piezoelectric nonlinearities

Abstract: In this paper, a comprehensive model of a micro-switch with both electrostatic and piezoelectric excitations, which accounts for the nonlinearities due to inertia, curvature, electrostatic forces and piezoelectric actuator is presented to demonstrate the mechanical characteristics of such a micro-system. Dynamic equations of this model are derived by the Lagrange method. Static analysis of this model is performed with five modes through the Galerkin method. The micro-switch beam is assumed as an elastic Euler-Bernoulli beam with clamped-free end conditions. The electrostatic actuation results are compared with other existing experimental and numerical results. Whereas the major drawback of electrostatically actuated micro-switches is the high driving voltage, using the piezoelectric actuator in these systems can provide less driving voltage and control the pull-in voltage. The study demonstrates that when the ratio of electrostatic actuation distance to length of micro-switch is small, the nonlinear piezoelectric term has a significant effect on the pull-in phenomenon. There are three ways to influence the design and control of the mechanical characteristics of this micro-switch: the softening effect due to electrostatic actuation, the hardening effect due to piezoelectric actuation, and varying the length and thickness of the piezoelectric actuator.

Piezoelectric voltage coupled reentrant cavity resonator

Abstract: A piezoelectric voltage coupled microwave reentrant cavity has been developed. The central cavity post is bonded to a piezoelectric actuator allowing the voltage control of small post displacements over a high dynamic range. We show that such a cavity can be implemented as a voltage tunable resonator, a transducer for exciting and measuring mechanical modes of the structure, and a transducer for measuring comparative sensitivity of the piezoelectric material. Experiments were conducted at room and cryogenic temperatures with results verified using Finite Element software.

High-order face-shear modes of relaxor-PbTiO3 crystals for piezoelectric motor applications

Abstract: The face-shear vibration modes of [011] poled Zt ± 45° cut relaxor-PT crystals and their applications for linear piezoelectric motors were investigated. Unlike piezoelectric ceramics, the rotated crystal was found to exhibit asymmetric face-shear deformations, and its two high-order face-shear modes degraded into two non-isomorphic modes. As an application example, a standing wave ultrasonic linear motor (10 × 10 × 2 mm3) operating in high-order face-shear vibration modes was developed. The motor exhibits a large driving force (1.5 N) under a low driving voltage (22 Vpp). These findings could provide guidance for design of crystal resonance devices.

A square-plate piezoelectric linear motor operating in two orthogonal and isomorphic face-diagonal-bending modes

Abstract: We report a piezoelectric linear motor made of a single Pb(Zr,Ti)O3 square-plate, which operates in two orthogonal and isomorphic face-diagonal-bending modes to produce precision linear motion. A 15 × 15 × 2 mm prototype was fabricated, and the motor generated a driving force of up to 1.8 N and a speed of 170 mm/s under an applied voltage of 100 Vpp at the resonance frequency of 136.5 kHz. The motor shows such advantages as large driving force under relatively low driving voltage, simple structure, and stable motion because of its isomorphic face-diagonal-bending mode.

Compact versatile stick-slip piezoelectric motor

Abstract: A motion control system that includes a base, a stage supported by the base and movable with respect to the base, and a motor coupled to the base and operable to move the stage. The motor includes a mounting base arranged to connect the motor to the base, a friction pad engageable with the stage, and a coupling portion including a first end connected to the mounting base and a second end. The friction pad is connected to the coupling portion between the first end and the second end. A piezoelectric element is disposed between the mounting base and the second end and is operable in response to an electrical signal to move the friction pad and the stage. A mounting screw is accessible from an exterior of the base and engages the coupling portion. The mounting screw is the sole attachment mechanism between the motor and the base.

Piezoelectric vibration device for mobile terminal

Abstract: A piezoelectric vibration device for a mobile terminal is disclosed. A bimorph piezoelectric vibrator includes a pair of piezoelectric element layers connected to one of positive and negative poles and a middle electrode plate interposed between the piezoelectric element layers and connected to the other pole. The piezoelectric vibrator generates vibration due to up/down bending displacement by fixing both end portions thereof to an inner surface of a casing of a mobile terminal. A voltage-boosting transformer raises a power source voltage of a mobile terminal to a driving voltage. A driving chip receives the raised driving voltage from the voltage-boosting transformer and drives the piezoelectric vibrator. Weights are attached to at least one of both sides of the piezoelectric vibrator to amplify vibration. Insulation members are provided at both end portions of the piezoelectric vibrator to prevent electricity applied to the piezoelectric vibrator from leaking to the casing.

A device for converting a movement of a user into a voltage

Abstract: A device (10) for converting a movement of a user into a voltage comprises a neck cord (20), a piezoelectric sensor (30) and a printed circuit board (40). The neck cord is coupled to the piezoelectric sensor and provides in use a pulling force that acts on the piezoelectric sensor in a first direction. The printed circuit board is electrically and mechanically coupled to the piezoelectric sensor. The weight of the printed circuit board cause in use a gravity force to act on the piezoelectric sensor in a second direction, which differs from the first direction such that the movement of the user (5) wearing the neck cord causes a change in the shape of the piezoelectric sensor which in response thereto generates the voltage. The voltage may be used as a supply source for an electrical component (41) mounted on the PCB, or may be used as a wake-up signal for an electrical component such as a processor (41) or an accelerometer.

Piezoelectric vibrational energy harvester

Abstract: A vibrational energy harvester having a base and a piezoelectric transducer formed from a layer of piezoelectric material and extending between a first end at the base and a second end. At least a portion of the piezoelectric transducer is arranged in a back and forth pattern between the first and second ends. A magnetic component provides a magnetic field within which at least a portion of the piezoelectric transducer operates so that it exhibits nonlinear behavior. A biomedical implantable device using the vibration energy harvester can extract energy from heartbeat waveforms (heartbeats) to thereby power a device within the body.

Comparison of stabilization of current-actuated and voltage-actuated piezoelectric beams

Abstract: Current controlled piezoelectric beams have become increasingly popular recently. The authors have used a variational approach derive the model for a single piezoelectric beam actuated by a current source at the electrodes, and similarly for the voltage-controlled case. Magnetic effects are included. In addition to the Euler-Bernoulli displacement assumptions for the mechanical part, electrical and magnetic vector potential terms are assumed to be quadratic-through thickness, not linear. Inclusion of magnetic effects significantly changes the stabilizability properties of the model. The voltage-controlled beam leads to a control operator that is unbounded in the energy space, while the current-controlled case leads to a bounded control operator. The two situations are compared from a control perspective.

Piezoelectric material, piezoelectric element, liquid ejecting head, liquid ejecting apparatus, ultrasonic sensor, piezoelectric motor, and power generator

Abstract: A piezoelectric material contains a first component that is a rhombohedral crystal that is configured to have a complex oxide with a perovskite structure and Curie temperature is set to be Tc1 and a second component that is a crystal other than a rhombohedral crystal that is configured to have a complex oxide with the perovskite structure and Curie temperature is set to be Tc2, in which the absolute value of the difference between Tc1 and Tc2 |Tc1-Tc2| is equal to or lower than 50°C, and a composition near an MPB line is provided in a phase diagram that employs a composition ratio of a first component to a second component for the horizontal axis and temperature for the vertical axis

Finite element method analyses of ambient temperature effects on characteristics of piezoelectric motors

Abstract: There have been numerous experimental reports about the environmental effects on characteristics of intelligent actuators, such as the piezoelectric motors. However, the influences of temperature coefficients of material properties, which are the fundamental reasons for the changes of motors’ output characteristics in different ambient temperature condition, are specially difficult to be acquired through experiments. Thus, the optimization for piezoelectric motors driven in extreme environments is scarce till now. This article is aimed to establish one calculating method to solve this problem. First, a theoretical model is developed for investigating the effects of ambient temperature on characteristics of piezoelectric motors by the finite element method. And then, the mechanical and electrical characteristics of a piezoelectric motor are measured to demonstrate the theoretical model. After that, the changes of critical parameters caused by the ambient temperature are discussed. Based on this, the final ...