Gripper Design for Radio Base Station Autonomous Maintenance System

For an autonomous system to perform maintenance tasks in a networking device or a radio base station (RBS), it has to deal with a series of technological challenges ranging from identifying hardware-related problems to manipulating connectors. This paper describes the development of a robot maintenance system dedicated to detect and resolve faulty links caused by unplugged or poorly connected cables. Although the maintenance system relies on four subsystems, we significantly focus on our low-cost and efficient custom gripper solution developed to handle RJ45 Ethernet connectors. To examine our gripper, we conducted three experiments. First, a qualitative questionnaire was submitted to 30 users in the case of the teleoperated scenario of the gripper attached to a robotic arm. Similarly, we also tested the automatic operation mode. The results showed that our system is reliable and delivers a highly efficient maintenance tool in both teleoperated and autonomous operation modes. The practical experiment containing the removal or unplugging of connectors demonstrated our gripper’s ability to adequately handle these, whereas the feedback from the questionnaire pointed to a positive user experience. The automatic test assessed the gripper’s robustness against the continuous operation.

     

Spectral interferometry of semiconductor nanostructures

Fourier transform spectral interferometry is applied to measure both amplitude and phase of the electric field in different types of semiconductor nanostructures, thus determining the real and imaginary parts of the dielectric function. The importance of measuring the phase is shown and discussed in three studies. First, the phase measurement is used to access directly the refractive index across excitonic resonances in bulk GaAs and AlGaAs-GaAs quantum wells, with unprecedented resolution. Second, we measure the density dependence of the full dielectric function across a Fano resonance in bulk GaAs and show that this allows us to obtain some information on the collisional broadening of the usually hidden linewidth of the coupled exciton/continuum. Third, the phase is studied in a complex heterostructure, a semiconductor microcavity. We investigate and discuss the effect of the cavity detuning and of the excitation density     

Optimizing NFV placement for distributing micro-data centers in cellular networks

With the popularity of mobile devices, the next generation of mobile networks has faced several challenges. Different applications have been emerged, with different requirements. Offering an infrastructure that meets different types of applications with specific requirements is one of these issues. In addition, due to user mobility, the traffic generated by the mobile devices in a specific location is not constant, making it difficult to reach the optimal resource allocation. In this context, network function virtualization (NFV) can be used to deploy the telecommunication stacks as virtual functions running on commodity hardware to meet users’ requirements such as performance and availability. However, the deployment of virtual functions can be a complex task. To select the best placement strategy that reduces the resource usage, at the same time keeps the performance and availability of network functions is a complex task, already proven to be an NP-hard problem. Therefore, in this paper, we formulate the NFV placement as a multi-objective problem, where the risk associated with the placement and energy consumption are taken into consideration. We propose the usage of two optimization algorithms, NSGA-II and GDE3, to solve this problem. These algorithms were taken into consideration because both work with multi-objective problems and present good performance. We consider a triathlon circuit scenario based on real data from the Ironman route as an use case to evaluate and compare the algorithms. The results show that GDE3 is able to attend both objectives (minimize failure and minimize energy consumption), while the NSGA-II prioritizes energy consumption.

     

Modeling and assessing an intelligent system for safety in human-robot collaboration using deep and machine learning techniques

Multimedia Tools and Applications - The introduction of technological innovations is essential for accident mitigation in work environments. In a human-robot collaboration scenario, the current...     

Interaction between proton exchange membrane fuel cells and power converters for AC integration

New aspects about steady-state and transient behaviours are considered in the relationships among the model variables for fuel cell (FC) stacks that are of great interest in the scientific environment. In this way, the most important variables are voltage, current, power, heat from cooling system, membrane temperature and hydrogen pressure. The transient model aims at reproducing FC variations of its internal resistance under distinct current levels. This current effect modifies the time response during load turning on/off conditions. Results from a modified FC model are presented and comparisons with real data are made. Additionally, these results are included in an analysis about the electrical interaction between FCs and converters as a cause of great concern among power electronics designers. As the number of such converters has significantly increased in the last few years, FC generation systems are steadily calling attention for operational problems related to their efficiency, stability and durability when DC/DC converters are connected across its terminals. Therefore design proceedings of a DC/DC converter associated to 'T' filters to avoid fast current transitions caused by converter connection across the FC stack terminals are included. To deliver the energy produced by the FC system to the grid, it is presented, also, an analysis of a DC-AC converter used to improve power quality when the FC is, simultaneously, supplying load and grid.