In this paper, the problemof designingacontrol lawincase ofrotor failure inquadrotor vehiclesis addressed. First, a nonlinear mathematical model for a quadrotor vehicle is derived, which includes translational and rotational dynamics. Then a robust feedback linearization controller isdeveloped, which sacrifices the controllability ofthe yaw state due to rotor failure to linearize the closed-loop system around a working point, where roll and pitch angles are zero and the angular speed around the vertical axis is a nonzero constant. An H∞ loop shaping technique is adopted to achieve regulationofthese variables around the chosen working point. Finally,anouter loopisproposed for achieving control of the linear displacement under the assumption of small angles approximation for the pitch and roll angles. The proposed control strategy allows the vehicle to use the remaining three functional rotors to enter a constant angular speed around its vertical axis, granting stability and representing an effective way to deal with a rotor failure in quadrotor vehicles

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Both the theoretical background and the experimental results of an algorithm developed to perform human respiratory rate measurements without any physical contact are presented. Based on depth image sensing techniques, the respiratory rate is derived by measuring morphological changes of the chest wall. The algorithm identifies the human chest, computes its distance from the camera and compares this value with the instantaneous distance, discerning if it is due to the respiratory act or due to a limited movement of the person being monitored. To experimentally validate the proposed algorithm, the respiratory rate measurements coming from a spirometer were taken as a benchmark and compared with those estimated by the algorithm. Five tests were performed, with five different persons sat in front of the camera. The first test aimed to choose the suitable sampling frequency. The second test was conducted to compare the performances of the proposed system with respect to the gold standard in ideal conditions of light, orientation and clothing. The third, fourth and fifth tests evaluated the algorithm performances under different operating conditions. The experimental results showed that the system can correctly measure the respiratory rate, and it is a viable alternative to monitor the respiratory activity of a person without using invasive sensors.

The present paper deals with fatigue experimentation and with the application and improvement of predictive models; in addition, a sensitive analysis is performed on the main factors related to the shot‐peening treatment and on the efficiency of the aforementioned models. The research involved gears, made of high‐strength steel and carburised, quenched, ground, shot‐peened and superfinished. The experimental campaign initially dealt with the investigation into the influence of isotropic superfinishing; the attention was then focused on shot peening and how to optimise the fatigue limit, by a suitable choice of operative parameters. The option of duplex peening for further fatigue improvement was also considered. Results concerning component residual stress distributions and fatigue limits were then processed by investigating their sensitivity with respect to driving factors, namely the shot diameter and the Almen intensity. Two theories for fatigue prediction (the method of the relative stress gradient and the theory of critical distances) were reviewed for application to shot‐peened components, with a comparison between experimental and numerical results. A comparative analysis was then performed on the two theories, on the basis of the number of data inputs, advantages and drawbacks, while sensitivity analyses focused on how uncertainties affecting input data propagate to predictive results.

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The subject of this paper is to investigate the capability of the relative stress gradient to properly represent the beneficial effect of residual stress states on the fatigue life of Ti‐6Al‐4V specimens, with notches of different severity. The research was developed considering notched and un‐notched specimens with different geometries and different shot‐peening treatments. The results were determined by running fatigue experimentation under rotating bending and by developing a novel predictive model based on the relationship between the local fatigue limit and a generalized form of the relative stress gradient, accounting for the peening‐induced residual stresses. The proposed tool for fatigue limit estimation was completed by a stochastic analysis, which considered the variability of the involved parameters, in particular the residual stress entity. This made it possible to finally determine the component failure probability in a general, efficient and accurate way.

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