This paper presents an improved version of the insect-mimicking flapping-wing mechanism actuated by LIPCA (Lightweight Piezo-Composite Actuator). As the previous version, the actuation displacement of the actuator is converted into flapping-wing motion by a mechanical linkage system that functioned as displacement amplifier as well. In order to provide feathering motion, the wing is attached to the axis through a hinge system that allows the wing rotation at each end of half-stroke, due to air resistance. In this improved version, the total weight has been reduced to the half of the previous one. The device could produce about 90 degree of flapping angle when it operated at around 10 Hz, which was the natural flapping-frequency. Several flapping tests under different parameter configurations were conducted in order to investigate the characteristic of the generated lift. In addition, the smoke-wire test was also conducted, so that the vortices around the wing can be visually observed. Even though the present wing has smaller wing area, it could produce higher lift then before.
IPMC (Ionic Polymer-Metal Composite) actuators produce large bending displacements under low input voltages and are flexible enough to be implemented for biological and/or biomimetic applications. In this study, IPMC was considered for the development of a natural muscle- like linear actuator. For the purpose of design, numerical analysis was utilized to predict free strain and blocked stress of IPMC-based linear actuators, which we considered as the important parameters of muscle-like actuator. An elementary unit composed of an IPMC and the base polymer, NafionTM, was proposed for an effective linear actuator. In order to find an optimal design and evaluate the actuation characteristics of the proposed elementary unit, actuation displacement and force were numerically calculated. The optimal elementary unit produced the maximum free strain of 25% under an applied 2V input.
This paper presents the design and analysis of an IPMC (Ionic Polymer-Metal Composite) driven micropump. It should be noted that IPMC is a promising material candidate for micropump applications since it can be operated with low input voltages and can produce large stroke volumes along with controllable flow rates. Moreover, the micropump manufacturing process with IPMC is convenient. It is anticipated that the manufacturing cost of the IPMC micropump is competitive when compared to other competing technologies. In order to design an effective IPMC diaphragm that functions as an actuating motor for a micropump, a finite element analysis was utilized to optimize the shape of IPMC diaphragm and estimate stroke volume through several parametric studies. In addition, effect of the pump chamber's pressure on the stroke volume was numerically investigated. Appropriate inlet and outlet nozzle/diffusers for the micropump were also chosen. Based on the selected geometry of nozzle/diffusers and the estimated stroke volume, flow rate of the IPMC micropump was predicted.
An IMPC actuated flapping wing has been designed and demonstrated for mimicking flapping motion of a bird wing. The flapping wing can produce twist motion as well as flap up and down motions. For design of the wing, an equivalent beam model has been proposed based on the measured force-displacement data. The equivalent model is used to determine suitable IPMC actuator patterns that can create twist motion during up- and down-strokes of the wing. The IPMC actuator pattern is inserted in a wing-shaped plastic film to form a complete flapping wing. Experimental results show that the properly shaped IPMCs can create aniosotropic motion that is often required for producing effective thrust and lift forces in bird flight.
In this paper, we present our recent progress in application of LIPCA (LIghtweight Piezo-Composite Actuator) to design and demonstration of a flapping wing device. The flapping device has flexible wings actuated by the LIPCA. The device is designed such that it can create twist motion during up- and down-stroke like bird or insect wings. The motion could be generated by using LIPCA actuator pivoted to the wing. The wing can bend and twist due to bending-twist coupling of the specially designed pivot system. Experimental results show that the properly designed flapping device powered by LIPCA can create anisotropic motion that is often required for producing effective thrust and lift forces in bird or insect flight.
In this paper, material nonlinear behavior of PZT wafer (3202HD, CTS) under high electric field and tensile stress is experimentally investigated and the nonlinearity of the PZT wafer is numerically simulated. In the simulation, new definitions of the piezoelectric constant and the incremental strain are proposed. Empirical functions that can represent the nonlinear behavior of the PZT wafer have been extracted based on the measured piezo-strain under stress. The functions are implemented in an incremental finite element formulation for material nonlinear analysis. With the new definition of the incremental piezo-strain, the measured nonlinear behavior of the PZT wafer has been accurately reproduced even for high electric field.
Biomimetic wing sections actuated by piezoceramics actuator LIPCA have been designed and their actuation displacements estimated by using the thermal analogy and MSC/NASTRAN based on the linear elasticity. The wing sections are fabricated as the design and tested for evaluation. Measured actuation displacements were larger than the estimated values mainly due to the material non-linearity of the PZT wafer. The biomimetic wing sections can be used for control surfaces of small scale UAVs.
In the present work, the existing formulation of nine-node shell element based on Hellinger-Reissner principle is expanded for electro-mechanically coupled field analysis. The electro-mechanical coupling effect of the piezoelectric material is introduced to the formulation through the constitutive relation. Based on the formulation, a linear finite element code is constructed and it is validated by several numerical tests. By using the code, linear analysis of LIPCA(LIghtweight Piezoelectric Composite Actuator) is performed to calculate actuation displacement and stress. Moreover, to improve simulation result more accurately, an experimental piezo-strain function of PZT(3203HD, CTS) wafer that is embedded in LIPCA is obtained from measured data and the function is implemented into the code by adopting incremental method. And then, the actuation displacement of LIPCA is recalculated and the result is compared with the measured data.
This paper deals with a fully coupled assumed strain solid element that can be used for simultaneous moiling of thin sensors and actuators. To solve fully coupled field problems, electric potential is regarded as a nodal degree of freedom in addition to three translations in an eighteen node assumed strain solid element. Therefore, the induced electric potential can be calculated for a prescribed deformation or an applied load. Since the original assumed strain solid element is free of locking, the element can be used to analyze behavior of very thin actuators without locking. Numerical examples, such as a typical bimorph actuator/sensor beam problem shows that the present element can handle fully coupled problems. Using the solid element, we have analyzed the actuation performance of THUNDER and compared the result with measured data. The comparison shows that the numerical estimation agrees well with measured displacement for simply supported boundary condition. It is also found that a particular combination of materials for layers and curvature of THUNDER improve actuation displacement.