Lightweight Piezo-composite Actuator Research Articles

Design and evaluation of a LIPCA-actuated flapping device

In this paper, we have introduced a flapping wing mechanism actuated by a unimorphpiezoceramic actuator, LIPCA (lightweight piezo-composite actuator). In theflapping system, the limited actuation displacement produced by bending motion ofthe simply supported actuator was transformed into a large flapping angle byusing a four-bar linkage system. A wing rotation mechanism was also designed andimplemented such that the wing can be passively rotated due to the resultantaerodynamic force during flapping motion. The natural flapping frequency of the devicewas about 9 Hz, where the maximum flapping angle was achieved. Flapping testsunder 4–15 Hz flapping frequencies were performed to investigate the flappingperformance by measuring the vertical force and forward force produced. The maximumforces were produced when the flapping device was actuated near the naturalflapping frequency. The measured force data indicated that the present flappingsystem could produce positive average forces in the vertical and forward directions.

압전 복합재료 작동기 LIPCA와 단일 PZT의 보 진동 제어 성능 비교

본 논문에서는 기존에 개발한 압전 복합재료 작동기인 LIPCA가 동적 구조물의 작동기로 적용 가능한지를 평가하였다. 압전 세라믹 층, 탄소/에폭시 층 및 유리/에폭시 층으로 이루어진 LIPCA 작동기는 단일 PZT에 비하여 성능 및 내구성이 크다는 장점이 있다. 성능 평가를 위하여 정적 작동력 실험과 진동 제어 실험을 수행하였다. 알루미늄 보의 한 쪽 면에 LIPCA와 단일 PZT를 각각 보에 부착하고 반대쪽 면에는 변형률 게이지를 부착하였다. 먼저 정적 작동력 실험에서는 작동 전압에 따른 변형률 신호를 등가 작동 모멘트로 환산하여 크기를 비교함으로써 성능을 평가하였다. 진동 제어 실험에서는 스트레인 게이지의 변형률 신호를 PID 제어 알고리듬을 사용하여 보의 자유 진동을 억제하도록 제어 신호를 생성하였다. 진동 신호가 감쇠하는 정도를 나타내는 안정화 시간을 비교함으로써 성능을 평가하였다. 실험 결과 LIPCA가 정적 작동 뿐 아니라 자유 진동 제어에서도 단일 PZT보다 성능이 우수함을 확인하였다. The purpose of this paper is to evaluate potential application of Lightweight Piezo-composite Actuator (LIPCA) to suppress vibrations of structures. The LIPCA, consisting of a piezoelectric layer, a carbon/epoxy layer and glass/epoxy layers, has advantages in terms of high performance, durability and reliability, compared to the bare piezoelectric ceramic (PZT) actuator. We performed two kinds of experiments on static actuation and active vibration suppression to investigate the actuation performances of the LIPCA and the bare PZT. We attached the actuator on one side and a strain gage on the other side of an aluminum beam. In the static actuation test, we evaluated the performance by comparing equivalent actuation moments of the LIPCA and the bare PZT due to the applied voltage. In the active vibration control test, control signals were generated to suppress the vibration of the beam by the PID control algorithm based on the measured strain signals. The performances were estimated based on settling times of the strain responses. It can be concluded that the LIPCA has better actuation performances than the bare PZT in active control of free vibration as well as static actuation.

Structural Design, Manufacturing, and Wind Tunnel Test of a Small Expandable Wing

This paper describes design, manufacturing, and wind tunnel test of a motor-driven small-scale expandable wing for MAV class vehicles. The bird-like expandable wing has been developed for investigating the influence of aspect ratio change on the lift and drag of the wing. As a typical bird wing, the wing is separated into inner and outer wings. The wing model consists of the linkage system made of carbon composite strip/rod and the remaining part covered with carbon composite sheet and multiple LIPCAs (Lightweight Piezo-Composite Actuators) mimicking wing feathers. The LIPCA actuator was used to control wing camber, which created additional lift. Wind tunnel tests were conducted to investigate the changes in lift and drag during wing folding and expansion, and to observe the influence of LIPCA actuation on the wing. In the tests, effects of the wing fold/expansion and actuation of LIPCA on changes in lift and drag were quantitatively identified.

Power Consumption of Piezo-Composite Actuator at Resonance Frequency

This paper addresses the power consumption of the LIPCA (LIghtweight Piezo-Composite Actuator) device system when electric input was applied at its resonance frequency. The LIPCA device system is composed of a piezoelectric ceramic layer and fiber reinforced lightweight composite layers. Typically, a PZT ceramic layer is sandwiched by a top fiber layer with low CTE (coefficient of thermal expansion) and base layers with high CTE. The advantages of the LIPCA design are weight reduction by using the lightweight fiber reinforced plastic layers without compromising the generation of high force and large displacement, and design flexibility by selecting the fiber direction and the size of prepreg layers. An experimental set-up was specially designed to measure the power consumption of the LIPCA. By measuring the capacitance of the PZT ceramic wafer during the test, the electric power that consumed can be determined. Experimental results revealed a significant increase in capacitance of the PZT ceramic wafer with an increase in the frequency of applied voltage around the natural frequency of the actuator.

Design and Test of Flapping Device Mimicking Insect Flight

This paper addresses detail design and demonstration of an insect-mimicking flappingwing mechanism composed of LIPCA (Lightweight Piezo-Composite Actuator) and linkage system that can amplify the actuation displacement of LIPCA. The angular amplification of the linkage system can provide various flapping angles by adjusting the actuation point of the LIPCA. The device can generate flapping frequency ranging from 5 to 50 Hz depending on weight of the wing and linkages. Flapping tests using different wing mass, area, and aspect ratio were performed to investigate the flapping performance. The test results were described and compared with the estimation. It was found that changes in wing mass, area, and aspect ratio result in significant variation of natural flapping-frequency.

LIPCA 작동기로 구동되는 날갯짓 기구의 설계 및 성능평가

In this paper, we present our recent progress in the LIPCA (Lightweight Piezo-Composite Actuator) application for actuation of a flapping wing device. The flapping device uses linkage system that can amplify the actuation displacement of LIPCA. The feathering mechanism is also designed and implemented such that the wing can rotate during flapping. The natural flapping-frequency of the device was about 9 Hz, where the maximum flapping angle was achieved. The flapping test under 4 Hz to 15 Hz flapping frequency was performed to investigate the flapping performance by measuring the produced lift and thrust. Maximum lift and thrust were produced when the flapping device was actuated at about the natural flapping-frequency.

Performance analysis of a lightweight piezo-composite actuator considering the materialnon-linearity of an embedded PZT wafer

This paper analyzes the performance of lightweight piezo-composite actuators (LIPCAs)including the material non-linearity of the embedded 3203HD PZT wafer. For this analysis,we used a piezo-shell element code based on a nine-node assumed strain shell elementformulation. The material non-linearity was included in the formulation due to the largeobserved discrepancies in the measured displacement and computed actuation displacementbased on the linear analysis, especially at high input voltages. An experimentallyextracted piezo-strain function of the PZT wafer and incremental formulation wereincorporated into the linear finite element code to improve the accuracy of the estimatedactuation displacement of the LIPCA. The non-linear piezo-shell program was used toestimate the non-linear performance of the LIPCA. The actuation displacementpredicted from the non-linear code showed much better agreement with the measureddata.

Design and demonstration of a biomimetic wing section using a lightweight piezo-compositeactuator (LIPCA)

This paper describes the design and evaluation of biomimetic wing sections, where thetrailing edges of the wing sections are actuated by the piezoceramic actuator LIPCA(lightweight piezo-composite actuator). Thermal analogy based on linear elasticity was usedfor the design and analysis of the wing sections. In the actuation test of the wing sections,the effective deflection angle of the trailing edge was approximately five degrees at 300 Vinput. The predicted and measured actuation displacements agreed very well up to aninput of 150 V. However, the real actuation displacement became larger than theestimated value for higher input voltages due to the material non-linearity of the leadzirconate titanate (PZT) wafer in the LIPCA. The biomimetic wing sectionscan be used for control surfaces of small scale unmanned aerial vehicles (UAVs).

Performance evaluation of lightweight piezo-composite actuators

This paper is concerned with the performance evaluation and comparison for several kinds of lightweight piezo-composite actuator (LIPCA) device system. LIPCA device system is composed of a piezoelectric ceramic wafer layer and fiber reinforced light composite layers, typically a PZT ceramic layer is sandwiched by a top fiber layer with low coefficient of thermal expansion (CTE) and base layers with high CTE. To investigate the effect of lay-up structure of the LIPCA on the actuating performance, five kinds of actuator with different lay-up stacking sequence have been designed, manufactured, and tested. The performance of each actuator was evaluated using an actuator test system consisted of an actuator supporting jig, a high voltage actuating power supplier, and a non-contact laser measuring system. From the comparison of the performance of the LIPCA prototypes, it was found that the actuator with higher coefficient of unimorph actuator can generate larger actuating displacement.

Pressure Loading of Piezo Composite Unimorphs

ABSTRACTOver the past decade synthetic jets have emerged as a promising means of active flow control. They have the ability to introduce small amounts of energy locally to achieve non-local changes in the flow field. These devices have the potential of saving millions of dollars by increasing the efficiency and simplifying fluid related systems. A synthetic jet actuator consists of a cavity with an oscillating diaphragm. As the diaphragm oscillates, jets are formed through an orifice in the cavity. This paper focuses on piezoelectric synthetic jets formed using two types of active diaphragms, Thunder® and Lipca. Thunder® is composed of three layers; two metal layers, with a PZT-5A layer in between, bonded with a polyimide adhesive. Lipca is a Light WeIght Piezo Composite Actuator, formed of a number of carbon fiber prepreg layers and an active PZT-5A layer. As these diaphragms oscillate, pressure differences within the cavity as well as average maximum jet velocities are measured. These parameters are measured under load and no-load conditions by controlling pressure at the back of the actuator or the passive cavity. Results show that the average maximum jet velocities measured at the exit of the active cavity, follow a similar trend to the active pressures for both devices. Active pressure and jet velocity increase with passive pressure to a maximum, and then decrease. Active pressure and the jet velocity peaked at the same passive cavity pressure of 18kPa for both diaphragms indicating that the same level of pre-stresses is present in both actuators even though Lipca produces approximately 10% higher velocities than Thunder®.

Actuator Performance Degradation of Piezo-Composite Actuator LIPCA under Cyclic Actuation

This paper is concerned with the fatigue characteristics of LIPCA (LIghtweight Piezo-Composite Actuator) device system. LIPCA device system is composed of a piezoelectric ceramic layer and fiber reinforced light composite layers, typically a PZT ceramic layer is sandwiched by a top fiber layer with low CTE (coefficient of thermal expansion) and base layers with high CTE. The advantages of the LIPCA design are using the lightweight fiber reinforced plastic layers without compromising the generation of high force and large displacement and to have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use resin prepreg system. To investigate the degradation of actuation performance of LIPCA due to the repeated fatigue loading, the repeated loading tests up to several million cycle were performed and the actuation displacement for a given excitation voltage was measured during the test. The fatigue characteristics was measured using an actuator test system consisted of an actuator supporting jig, a high voltage actuating power supplier, and a non-contact laser measuring system and evaluated.

압전 세라믹의 재료 비선형성을 고려한 LIPCA 작동기의 성능 해석

본 논문에서는 압전재의 재료 비선형성을 고려한 경량 압전 복합재 작동기(LIPCA)의 성능 해석을 수행하였다. 성능 해석을 위해 9절점 쉘 요소 정식화에 바탕을 둔 압전 쉘 요소를 이용하였다. LIPCA의 작동 변위를 보다 정확히 예측하기 위하여, 실험을 통해 얻은 압전 변형률 함수와 증분 정식화를 추가하여 기존 선형 유한요소 프로그램을 수정하였다. 이렇게 개발된 재료 비선형 압전 옐 프로그램을 이용하여 LIPCA의 작동변위를 재 계산하였고, 재료 비선형 해석으로 얻은 작동 변위가 선형 해석으로 계산된 작동 변위 보다 측정 변위에 훨씬 근접함을 확인하였다. This paper deals with the performance analysis of LIPCA(Light-weight Piezo-Composite actuator) including the material nun-linearity of the embedded 3203HD PZT wafer. For this analysis, we used a piezo-shell element code based on a nine-node assumed strain shell element formulation. The material non-linearity was implemented in the formulation due to a large observed discrepancy between the measured displacement and the computed actuation displacement based on the linear analysis. An experimentally extracted piezo-strain function of the PZT wafer and incremental formulation were incorporated into the linear finite element code to improve the accuracy of the estimated actuation displacement of the LIPCA. The non-linear piezo-shell program was used to predict the non-linear performance of the LIPCA. The simulated actuation displacement from the non-linear code showed much better agreement with the measured data.

Analysis of LIPCA-C Actuators

This paper has focused on the analysis of newly proposed Lightweight Piezo-composite Curved Actuator. LIPCA was born from the idea that the heavy metal layers of THUNDERTM were replaced by lightweight fiber reinforced plastic layers. Several combinations of composites and PZT wafer have been tested and finally two types are chosen: LIPCA-C1 and C2. Finite element code, developed in the previous work, has been used for the investigation of their static and dynamic behaviors. The maximum actuation displacements and fundamental frequency with respect to the design parameters are presented.