Istituto Italiano di Tecnologia

About: Istituto Italiano di Tecnologia is a facility organization based out in Genoa, Italy. It is known for research contribution in the topics: Robot & Humanoid robot. The organization has 4561 authors who have published 14595 publications receiving 437558 citations. The organization is also known as: Italian Institute of Technology & IIT.

Continuous Nonsingular Terminal Sliding-Mode Control of Shape Memory Alloy Actuators Using Time Delay Estimation

Abstract: We have developed a continuous nonsingular terminal sliding-mode control with time-delay estimation (TDE) for shape memory alloys (SMA) actuators. The proposed method does not need to describe a mathematical model of a hysteresis effect and other nonlinearities; thus, it is simple and model free. The proposed control consists of three elements that have clear meaning: a TDE element that cancels nonlinearities in the SMA dynamics, an injection element that specifies desired terminal sliding-mode (TSM) dynamics, and a reaching element using a fast terminal sliding manifold that is activated accordingly when the system trajectory is not confined in the TSM. The proposed control has been successfully implemented in an SMA actuated system and experimental results show the proposed control is easily implementable and highly accurate. Once the TSM and the reaching condition are suitably specified, the tracking performance of the proposed control is improved compared with a conventional time delay control with a linear error dynamics.

Continuous-wave upconverting nanoparticle microlasers

Abstract: Reducing the size of lasers to microscale dimensions enables new technologies1 that are specifically tailored for operation in confined spaces ranging from ultra-high-speed microprocessors2 to live brain tissue3. However, reduced cavity sizes increase optical losses and require greater input powers to reach lasing thresholds. Multiphoton-pumped lasers4-7 that have been miniaturized using nanomaterials such as lanthanide-doped upconverting nanoparticles (UCNPs)8 as lasing media require high pump intensities to achieve ultraviolet and visible emission and therefore operate under pulsed excitation schemes. Here, we make use of the recently described energy-looping excitation mechanism in Tm3+-doped UCNPs9 to achieve continuous-wave upconverted lasing action in stand-alone microcavities at excitation fluences as low as 14 kW cm-2. Continuous-wave lasing is uninterrupted, maximizing signal and enabling modulation of optical interactions10. By coupling energy-looping nanoparticles to whispering-gallery modes of polystyrene microspheres, we induce stable lasing for more than 5 h at blue and near-infrared wavelengths simultaneously. These microcavities are excited in the biologically transmissive second near-infrared (NIR-II) window and are small enough to be embedded in organisms, tissues or devices. The ability to produce continuous-wave lasing in microcavities immersed in blood serum highlights practical applications of these microscale lasers for sensing and illumination in complex biological environments.