Development of SMA Based Actuator Mechanisms for Deployment of Control Surfaces

The research and development of SMA based actuator mechanisms are being pursued at many places. In this paper the on going research and development efforts at ACD, NAL to realize a SMA based actuator mechanism for deployment of a control surface model is discussed. The mechanism can be modified to either give a rotary or a linear output. The deployment of this control surface model was successfully demonstrated using the SMA based rotary actuator mechanism along with computerised powering devices and controls. This control surface model is deployed only during landing in order to improve the landing characteristics of the aircraft and remains retracted at all other times. The real challenge is the design and development of the SMA based mechanism, which will satisfy the weight and volume budget and more importantly consume minimum power. An innovative 3-gear relay arrangement was chosen primarily to save the power. In this type of arrangement 3 different input gears mounted on 3 independent input shafts are used to drive the same output shaft on which the control surface model is mounted. Independent banks of SMA wires drive each of the 3 input shafts. The actuation of the input shafts is done in a sequential manner and each them rotates the control surface model by different angles. At any given time only one bank of SMA is energized and therefore the power consumption reduces significantly in contrast to a case where the complete rotation of the control surface model has to be effected by a single input shaft power by a single bank of SMA. The state of art electronics and controls in order to achieve the above sequential actuation include miniaturized power devices, data acquisition, and controller of SMA actuation and health monitoring of SMA. The actuators have both hysterisis and non-linearity especially during the phase transformation when the electrical resistance changes abruptly. SMAs can be actuated by heating using external heaters or by resistive heating. For better control, high efficiency, compactness and silent operation, resistive heating is preferred. Individual miniaturized power devices (DC-DC converters) are developed to electrically isolate the SMA actuators. Adequate redundancy in terms of both mechanical actuators and powering devices is built in

Finite element analysis of plates with through cracks from higher order plate theory

A special crack tip element for plate bending is developed using general crack tip solutions derived from a continuum analysis through Reissnerls theory. It is demonstrated that using this in combination with a conventional shear flexible element, accurate results for bending stress intensity factor can be obtained over a wide range of a plate thickness parameter

Three-dimensional stress problem of a finite thick plate with a through crack under tension

The three dimensional state of stress in a finite thick rectangular plate with a through-crack under tension is investigated. It is found that the in-plane stresses and the transverse normal stress are singular while the transverse shear stresses are of the order of unity. The only type of singularity encountered is that of inverse square root all through the plate thickness including the corner points at the plate faces. The stress intensity factor which is found to vary with Z and the thickness ratio h/a drops rapidly in a thin boundary layer near the plate faces, but without actually vanishing there. The stress intensity factor reduces exactly to that for the plane strain case when h/a +a . All the three components of the displacement field are finite at the crack front

NAL's Contribution to Wind Energy Technology and its Application

A presentation given at the Three day CEP course on Wind Energy Technology organized by Energy System Engineering, Indian Institute of Technology, Bombay, under the Continuing Education and Quality Improvement Program, April 16 - 18, 2007. The presentation gives a birds eye view of NAL's activities related to Wind Turbine Technologies and its application since its establishment in 1959

Image for fusion

Images for fusion is provided. The image saras9t.jpg is a reference/ground truth image, saras91.jpg is out of focus image 1 and saras92.jpg is out of focus image 2. saras91.jpg and saras92.jpg can be used for image fusion and the resultent fused image can be compared with saras9t.jpg to evaluated the fusion algorithm

Mechanical behavior of molybdenum disilicide reinforced silicon carbide composites

Hot-pressed SiC and its composites containing 10, 20 and 30 vol.% MoSi2 were evaluated for their mechanical behavior. The addition of MoSi2, while improving the fracture toughness, was found to reduce the hardness and flexural strength of SiC. The strength of the composites was observed to decrease significantly at high temperature as compared to the strength of SiC. The composites exhibited plasticity in four-point bending in the test temperature range of 1300–1500 �C, indicating their damage-tolerant behavior

Technology Driven Programme for the Development for the Development of a Fixed wing micro Air Vehicle at NALDRIVEN

At NAL, we are developing Black Kite - a 300mm span fixed wing autonomous Micro Air Vehicle (MAV) with an endurance of 30 minutes. The first version of this indigenous MAV has been successfully flight-tested in two modes: radio-controlled, and recently, semi-autonomous. The autopilot system used in Black Kite has been developed indigenously and is state-of-the-art. During the development of such an autonomous vehicle, we accommodated for the rapidly improving technology and constantly updated our design to account for this. Especially, the disciplines of material and structural technology, navigation and control using miniature autopilot grew leaps and bounds during the design process time period. Interestingly, some of the technologies became obsolete during this time, and corrective action became necessary. Although the latest trend in technologies enabled improved engineering, the scientific input for the development remained well defined and mostly unaltered. The goal of this paper is to explain the impact of emerging technologies on the development of our modern MAV, Black Kite , at NA

Calibration of 0.2m low speed wind tunnel

This report presents the results of the calibration studies carried out in 0.2m Low Speed Wind tunnel. Measurements includes tunnel wall static pressures, free stream mean velocity and turbulence intensity profiles (in both X-Y and X-Z planes) across the tunnel for the velocity ranges of 10 to 20 m/s . A single component hotwire anemometer was used to carry out the mean and turbulence velocity in the test section and the wall static pressure were measured in a digital manometer (Furness). The mean velocity profiles show a good uniformity in the flow at the test section and the free stream turbulence levels are found to be in the range of 0.15 to 0.25 %. The boundary layer profile shows maximum thickness of about 10% of the tunnel width at 750mm from the test section entry