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On the realization of self-sensing piezoelectric MEMS actuators
No full textThree different configurations of self-sensing piezoelectric MEMS actuators are designed, fabricated, and tested with PZT as the active material. A two-port circular diaphragm resonator of radius 1000 μm, a cantilever of length 1000 μm and width-24 μm with two parallel top electrodes, and a four-legged resonator structure with a proof mass of total die size 1.6 mm × 3 mm are fabricated and characterized as self-sensing actuators without any cross-talk compensation.
A comparison among the output signals reveals that the cantilever (without etching the PZT in between the two electrodes) and the four-legged resonator perform well as self-sensing actuators,
while the two-port diaphragm resonator with large concentric top electrodes suffers from electrical cross-talk. A successful characterization of a self-sensing actuator with the common ground electrode (for cantilever) is being reported for the first time. Deflection values of as low as 1 nm could be easily resolved using the proof-mass resonator. The act of actuation is verified by directly measuring the motion with laser doppler vibrometry which cross-verifies the sensor signal produced by the piezoelectric layer
Scale estimation of monocular SLAM using direct acceleration pair measurements
No full textMonocular SLAM is increasingly being used to provide navigation solutions for autonomous systems. In this, a visual inertial solution is commonly used to get the scale factor estimate for the monocular SLAM problem where the acceleration data from IMU is integrated to get the absolute velocity and position estimates. Since the accelerometer data may have bias and inaccuracies, it may lead to accumulation of bias and noise errors resulting in drift from the true value positions. This may require an additional sensor to correct the drift. In this paper, the scale factor is estimated using the average acceleration pair data of SLAM and IMU and without any third sensor. For accounting the noise on average accelerations, the Maximum Likelihood estimator is proposed. The scale factor is therefore recovered without any integration of IMU acceleration avoiding any drift errors, improving the estimation of scale factor values. This scale estimation method is included in the ORB-SLAM algorithm in a separate thread for real-time implementation. The output of maximum likelihood estimator is compared with simple estimators namely arithmetic mean, geometric mean and median. The real time formulation developed is validated in experiments using an off the self commercial OptiTrack motion capture system. The present approach gives a robust and less complex estimate of scale factor purely from camera and IMU in the presence of noise on acceleration pairs
Compositional optimization of a commercially produced ferritic steel using microstructural heterogeneity and mechanical properties
No full textTitanium- and niobium-added medium-strength ferritic steels find widespread application in automotive industries. Carbon and nitrogen play an important role in controlling microstructure and mechanical properties of these alloys. In this study, five alloys were selected from commercial heats of the same grade. Carbon and nitrogen contents were different for them. The microstructure of steel consisted of polygonal ferrite with a small quantity of cementite. Two types of precipitates were identified. One group was coherent/semicoherent niobium carbide (NbC) of size <20 nm. Other group was incoherent titanium nitride (TiN)-NbC with size ≥20 nm. The quantity of NbC precipitates primarily contributed in strengthening the mechanism and the rate of strain hardening. The quantity of complex TiN-NbC was controlled by bulk nitrogen content of steel. These incoherent carbides were responsible for the deterioration of the mechanical properties of the alloy
Mathematical modeling of flapper nozzle valve
No full textIn this section, mathematical models for the flapper nozzle type servo valve are presented. These models are derived from the fundamental governing equations and are important in the context of understanding the dynamics of the system and realizing a virtual prototype for simulations. The various dynamic phenomenon involved in the system are represented using ordinary differential equations. These differential equations are solved using Laplace Transform technique to build single input single output system models in time domain. The transfer function model thus presented represents the spool stage and the flapper stage respectively and provides a good tool to understand system behaviour under various operating frequencies and input command of various amplitudes and patterns
Single stage axial compressor stability management with self-recirculating casing treatment
No full textA discrete self-recirculating casing treatment (RCT) with converging nozzle and Coanda jet is designed and introduced in a high speed transonic axial compressor stage. Numerical
parametric studies for various injection skew/yaw angles are carried out to quantify the effect on the performance parameters such as stall margin improvement, total-to-total pressure ratio, and stage isentropic efficiency. All the investigated cases yield sufficient stall margin improvements with no loss in pressure ratio and compressor efficiency compared to the solid casing. Stall margin improvement is higher at lower speeds. Detailed flow investigation of the role played by the jet injection at the compressor endwall region is highlighted. Flow diagnostics is carried out numerically for various flow parameters such as Mach number, static pressure, and total pressure variations. The low momentum fluid that usually builds and
occupies the adjacent blade passage at near stall condition is delayed further downstream due to the injection of the high-velocity jet
Increasing the Verification Analysis Using Tool Assessment as Per DO-254
No full textProgramming under simulation-based testing remains the essential methods for utilitarian approval for HDL (hardware description language) plans. Code coverage which ensures to utilize simulation assets and a measure of test design. In this way, more target techniques, which utilize some all around characterized practical code measurements to play out a quantitative examination of simulation fulfillment, are proposed and quickly getting a response. For this reason, numerous utilitarian code measurements are proposed to confirm the design written in HDL. Keeping in mind the end goal to screen the code variation during simulation, a committed apparatus is required other than the test system. Finally, this paper includes the proposed well-known methodologies to achieve an accuracy of a test system using Code coverage
Using Eye gaze tracker to automatically estimate pilots' cognitive load
No full textEye tracking is the process of measuring either the point of gaze (where one is looking) or the motion of an eye relative to the head. This paper investigated use of eye gaze trackers in military aviation environment to automatically estimate pilot's cognitive load from ocular parameters. We used a fixed base variable stability flight simulator with longitudinal tracking task and collected data from 14 military pilots. In another study, we undertook three test flights with a BAES Hawk Trainer aircraft doing air to ground attack training missions and constant G level turn maneuvers up to +5G. Our study found that ocular parameters like rate of fixation is significantly different in different flying conditions and pilot's control inceptor and tracking error in simulation tasks. Results from our studies can be used for real time estimation of pilots' cognitive load, providing suitable warnings and alerts to the pilot in cockpit and training of military pilots on cognitive load management during operational missions
Servo valve characteristic curves
No full textTypically, a servo valve is characterized by a series of curves which provide behavioural information of the servo valve under varying operating conditions. These curves are typically used in identifying the valve centre type, null bias, response to inputs of varying amplitudes at varying frequency and phase difference between system input and output at different operating frequencies
Progressive damage analysis of adhesively bonded patch repaired carbon fibre–reinforced polymer specimen under compression involving cohesive zone model
No full textIn this paper, the in-plane compression behaviour of open-hole carbon fibre composite specimens adhesively bonded with the external carbon fibre composite patches on the single- and double side are studied. Uniaxial compression tests are conducted on MTS machine using ASTM anti-buckling fixture. A 3D progressive damage model is developed to predict the damage initiation and failure in both unrepaired open cutout and repaired carbon fibre composite specimens under compressive load. Stress-based 3D-Hashin's failure criteria are used for predicting the fibre and matrix damage in carbon fibre composite. The cohesive zone model element is used for modelling the interlaminar delamination in carbon fibre composite specimen and also the adhesive layer between patch and specimen. Initial stiffness, damage initiation load and ultimate load of the specimen are obtained using progressive damage model based on finite element analysis, and they are compared against the experimental values. The load–deflection curve and the damage progression obtained from finite element analysis using progressive damage model is found to be in good coherence with the experimental predictions. In case of patch bonded carbon fibre composite specimens, failure mechanism starts with partial patch debonding followed by complete specimen failure
Temperature- And Angle-Dependent Emissivity and Thermal Shock Resistance of the W/WAlN/WAlON/Al2O3-Based Spectrally Selective Absorber
No full textSpectral emissivity is considered as one of the most critical thermophysical properties influencing photothermal conversion efficiency of solar selective absorbers. In addition, long-term stability at high temperature and thermal shock resistance are the performance-limiting properties of spectrally selective absorbers. In this context, this study reports the variation of emissivity with a change in emergence angles and operational temperatures for the newly developed W/WAlN/WAlON/Al2O3 absorber. An analysis of the experimental results demonstrates that hemispherical emissivity values at elevated temperature are comparable while calculated using both room temperature and high temperature reflectance data. Hence, the applicability of the room temperature measurement method is validated to evaluate high temperature emissivity. The analysis of angular measurements indicates an insignificant difference between hemispherical and near-normal emissivity values for W/WAlN/WAlON/Al2O3. The study suggests that hemispherical emissivity can be well approximated from near-normal emissivity values by avoiding complex angular measurement procedure. Importantly, one can achieve a combination of high solar absorptance (α = 0.90), low thermal emittance (ε = 0.15), and appreciable heliothermal efficiency (η = 87% at a concentration factor of 100) at 500 °C for the W/WAlN/WAlON/Al2O3 absorber. Thermal stability of this absorber was established by observing an insignificant change in the reflectance spectra while annealed at 80, 200, 300, and 400 °C. In addition, thermal cycling test for 30 times between room temperature and 450 °C in a high flux (40–60 kW/m2) solar simulator confirmed the efficacy of W/WAlN/WAlON/Al2O3 as a promising multilayer solar absorber for high temperature applications