Aeromechanical Analysis of a Smart Helicopter Rotor in Forward Flight
This paper deals with a smart system integrated into a helicopter blade aimed at giving an anhedral shape to the blade tip region to alleviate the blade-vortex interaction phenomenon that may cause reduced helicopter performance in terms of noise and vibrations. The blade tip morphing is obtained through the joint action of a magneto-rheological fluid (MRF) device, a shape-memory alloy ribbons- based (SMA) device and a set of concentrated masses properly distributed spanwise. The presence of this smart actuator (particularly the concentrated masses) inside the blades modifies the aeromechanical behaviour of the rotor and may be detrimental in terms of hub vibratory loads, pitch control effectiveness and aeroelastic stability. Following a previous literature work concerning with the effectiveness of the smart actuated rotor in hovering conditions, the present paper focuses on the aeromechanical effects due to the inclusion of the smart device in a four-bladed helicopter rotor in forward flight where blade morphing is not needed. Aim of this work is to investigate on the compatibility of the smart system with the required aeromechanical performance of the rotor, highlighting the feasibility of its application on helicopters.
A feasibility study on the behaviour of a helicopter smart blade aimed at blade tip morphing
In this paper, the behaviour of a hingeless helicopter blade with a novel integrated smart morphing actuator is studied. The proposed smart device is aimed at the reduction of BVI noise through transformation of the blade tip shape into an anhedral tip type and is based on the concept of a variable-stiffness blade. In detail, the blade morphing is obtained through joint action of a magneto-rheological-fluid (MRF) device, shape-memory alloy (SMA) tie-rods and a set of concentrated masses properly distributed spanwise. In this architecture, the MRF system has to provide local bending-stiffness reduction and concentrated masses have to provide inertial moments whereas the SMA tie-rods have to mould the blade tip shape. Since the equilibrium configuration of the smart blade deeply depends on the interaction between the aeroelastic response and the actuation loads, in this work a numerical investigation examines potentiality and shortcomings of the proposed integrated smar t system to morph a realistic blade with respect to the baseline configuration.
New approach to vision-based BGA package inspection
Ball grid array (BGA) techniques have developed very fast due to the advantages of more I/O ports, small size, and so on. In this paper, a vision-based algorithm for BGA package inspection is proposed to accurately estimate center and diameters of solder-balls of BGA packages, so that defects of BGA packages, such as missing or extra balls, oversize or undersize balls, over-height or under-height balls, and pitch can be detected for ensuring the quality of BGA packages.