Actuators2016, 5(2), 14; doi:10.3390/act5020014 - published 20 May 2016 Show/Hide Abstract
Abstract: This paper introduces recent advances on flapping-wing Micro and Nano Aerial Vehicles (MAVs and NAVs) based on Piezoelectric Actuators (PEA). Therefore, this work provides essential information to address the development of such bio-inspired aerial robots. PEA are commonly used in micro-robotics and precise positioning applications (e.g., micro-positioning and micro-manipulation), whereas within the Unmanned Aerial Vehicles (UAVs) domain, motors are the classical actuators used for rotary or fixed-wing configurations. Therefore, we consider it pertinent to provide essential information regarding the modeling and control of piezoelectric cantilever actuators to accelerate early design and development stages of aerial microrobots based on flapping-wing systems. In addition, the equations describing the aerodynamic behavior of a flapping-wing configuration are presented.
Actuators2016, 5(2), 11; doi:10.3390/act5020011 - published 18 May 2016 Show/Hide Abstract
Abstract: Antiferroelectrics (AFE) can exhibit a “shape memory function controllable by electric field”, with huge isotropic volumetric expansion (0.26%) associated with the AFE to Ferroelectric (FE) phase transformation. Small inverse electric field application can realize the original AFE phase. The response speed is quick (2.5 ms). In the Pb0.99Nb0.02[(Zr0.6Sn0.4)1-yTiy]0.98O3 (PNZST) system, the shape memory function is observed in the intermediate range between high temperature AFE and low temperature FE, or low Ti-concentration AFE and high Ti-concentration FE in the composition. In the AFE multilayer actuators (MLAs), the crack is initiated in the center of a pair of internal electrodes under cyclic electric field, rather than the edge area of the internal electrodes in normal piezoelectric MLAs. The two-sublattice polarization coupling model is proposed to explain: (1) isotropic volume expansion during the AFE-FE transformation; and (2) piezoelectric anisotropy. We introduce latching relays and mechanical clampers as possible unique applications of shape memory ceramics.
Actuators2016, 5(2), 13; doi:10.3390/act5020013 - published 29 April 2016 Show/Hide Abstract
Abstract: Piezoelectric tube actuators are extensively used in scanning probe microscopes to provide dynamic scanning motions in open-loop operations. Furthermore, they are employed as micropositioners due to their high bandwidth, high resolution and ease of excitation. However, these piezoelectric micropositioners exhibit badly damped vibrations that occur when the input excites the dynamic response, which tends to degrade positioning accuracy and performance. This paper deals with vibrations’ feedforward control of a multi-degrees of freedom (DOF) piezoelectric micropositioner in order to damp the vibrations in the direct axes and to reduce the cross-couplings. The novelty in this paper relative to the existing vibrations feedforward controls is the simplicity in design approach, the minimal number of shaper impulses for each input required to damp all modes of vibration at each output, and the account for the strong cross-couplings which only occur in multi-DOF cases. A generalization to a multiple degrees of freedom actuator is first proposed. Then simulation runs on a 3-DOF piezoelectric tube micropositioner have been effectuated to demonstrate the efficiency of the proposed method. Finally, experimental tests were carried out to validate and to confirm the predicted simulation.
Actuators2016, 5(2), 12; doi:10.3390/act5020012 - published 26 April 2016 Show/Hide Abstract
Abstract: Piezoelectric transformers (PTs) are solid-state devices that transform electrical energy into electrical energy by means of a mechanical vibration. These devices are manufactured using piezoelectric materials that are driven at resonance. With appropriate design and circuitry, it is possible to step up and step down the voltages between the input and output sections of the piezoelectric transformer, without making use of magnetic materials and obtaining excellent conversion efficiencies. The initial concept of a piezoelectric ceramic transformer was proposed by Charles A. Rosen in 1954. Since then, the evolution of piezoelectric transformers through history has been linked to the relevant work of some excellent researchers as well as to the evolution in materials, manufacturing processes, and driving circuit techniques. This paper summarizes the historical evolution of the technology.
Actuators2016, 5(1), 10; doi:10.3390/act5010010 - published 21 March 2016 Show/Hide Abstract
Abstract: This paper presents the modeling and design of an actuator consisting of an electrical motor and a magnetic gear. To minimize the overall actuator dimensions, both of the electromagnetic devices need to be optimally designed and matched. An issue in performing a simultaneous design as such arises from a high number of design variables that significantly increases the complexity of the optimization problem. A method to reduce the design variables is discussed in this paper, which is the application of response surface methodology (RSM) to represent the optimized torques of the electrical motor and magnetic gear as polynomial functions of their respective dimensions. Prior to the application of RSM, optimization problem statements are defined for the electrical motor and magnetic gear, for which the optimization objective and constraint functions are derived from analytical electromagnetic models of the considered electromagnetic devices.
Actuators2016, 5(1), 9; doi:10.3390/act5010009 - published 9 March 2016 Show/Hide Abstract
Abstract: Multiferroic magnetoelectric (ME) composites are attractive materials for various electrically and magnetically cross-coupled devices. Many studies have been conducted on fundamental understanding, fabrication processes, and applications of ME composite material systems in the last four decades which has brought the technology closer to realization in practical devices. In this article, we present a review of ME composite materials and some notable potential applications based upon their properties. A brief summary is presented on the parameters that influence the performance of ME composites, their coupling structures, fabrications processes, characterization techniques, and perspectives on direct (magnetic to electric) and converse (electric to magnetic) ME devices. Overall, the research on ME composite systems has brought us closer to their deployment.