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Jayakumar, M.
- Estimation of Extreme Rainfall over Nilgiris, South India
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Indian Forester, Vol 108, No 6 (1982), Pagination: 444-448Abstract
Extreme rainfall (also called probable maxImum precipitation-PMP) over Nilgiris, South India, has been computed by using Hershfield's statistical techniques from the daily rainfall data for the last 37 to 61 years (1918 to 1978). The enveloping value for the frequency factor Km was found to be 6.27 for this region. On the basis of this data a generalized chart of PMP was prepared for the Nilgiris for one day duration. The frequency curve obtained for Nilgiris has been compared with the similar curves prepared on the basis of North India record rainfall and world record rainfall data.
- Estimation of Extreme Rainfall over Nilgiris, South India
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Indian Forester, Vol 107, No 10 (1981), Pagination: 659-664Abstract
Extreme rainfall (also called probable maximum precipitation - PMP) over Nilgiris, South India, has been computed by using Hershfield's statistical techniques from the dailY rainfall data for the last 37 to 61 years (1918 to 1978). The enveloping value for the frequency factor km was found to be 6.27 for this region. On the basis of this data, a generalized chart of PMP was prepared for the Nilgiris for one day duration. The frequency curve obtained for Nilgiris has been compared with the similar curves prepared on the basis of North India record rainfall and world record rainfall data.- Indoor Robot Localisation using Kalman Filter
Abstract Views :181 |
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Authors
Affiliations
1 Department of Electronics and Communication Engineering, Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, Amrita University – 641112, IN
1 Department of Electronics and Communication Engineering, Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, Amrita University – 641112, IN
Source
Indian Journal of Science and Technology, Vol 9, No 38 (2016), Pagination:Abstract
Objective of this paper is to reduce the error in the estimation of the position of the robot. The localization of robot is a critical aspect in making them completely autonomous. Hence accuracy in estimating the position of the robot is of paramount importance. In order to make decisions without direct manual instructions the robot has to be aware of its position in the environment along with the situation at hand. For this effect the robots are built with sensors specifically designed to suit the need of the environment to gain feedback from the surrounding thereby obtaining data about its placement and the conditions around it. It is here that the problem of accuracy arises as there are uncertainties in both the feedback system as well as controlling system of the robot. To make a logical decision, the errors have to be minimized by optimally combining the data received from all the sources. The estimation theory provides us with a solution in the form of Kalman filter algorithm. It is an adaptive filter that combines uncertain data to obtain valid values of output required. It is seen that as SNR increases MSE in the position of the robot decreases thus accuracy increases. In this paper we concentrate on the issue of robot localization in closed space whose dimensions are previously known. We model the localization process as a linear phenomenon, as Kalman filter algorithm can only be used for linear systems. Using MATLAB Simulink we simulate our model to verify the concepts and validate the use of this filter in accurately determining the position of robot.Keywords
Adaptive Filter, In-door Navigation, Indoor Robots Kalman Filter, Robot Localization.Full Text
- Design of Cascaded Common Source Low Noise Amplifier for S-Band using Transconductance Feedback
Abstract Views :196 |
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Authors
Affiliations
1 Department of Electronics and Communication Engineering, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Amrita University,Coimbatore – 641112, Tamil Nadu, IN
1 Department of Electronics and Communication Engineering, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Amrita University,Coimbatore – 641112, Tamil Nadu, IN
Source
Indian Journal of Science and Technology, Vol 9, No 16 (2016), Pagination:Abstract
Background/Objectives: Now-a-days advancements in CMOS technology increase the demand on transceiver design in the aspect of gain, linearity, power, re-configurability and cost-effectiveness. The performance of RF frontend of transceiver system using MOS device are excellent and found to be the par of 3-5 semiconductor technology. Methods/Statistical Analysis: The first component present in transceiver design is Low Noise Amplifier (LNA) which requires high gain, low noise, better input-output matching, low power, good linearity and stability. Trade off between these performances is more complex when transistors operate at reduced supply voltage and reduced power consumption. So many researchers focus to modify the existing topology by adding active/passive feedback elements and/or using current re-use inductors 2,3. But the latter, suffer from large power consumption. Moreover LNA using cascode configuration offers good gain with low power but the circuit has the limitation of output voltage swing 4. So the proposed work focuses on the design of LNA using transconductance feedback in Common Source (CS) configuration circuits. Findings: At RF frequencies, distributed parasitic of the device dominates thus altering the input-output matching characteristics which degrades gain, noise figure and stability of Low Noise Amplifier. So design of multistage LNA with feedback techniques is necessary to increase the gain. The transconductance feedback used in the design of LNA suits well for increase of gain provided if it is properly designed to ensure stability. The proposed work involves the design of MOS based low noise amplifier using single stage and cascaded Common Source (CS) configuration in S-band. By using the transconductance feedback in CS amplifier, the voltage gain is boosted. Using the extracted small signal equivalents, single stage and cascaded CS amplifier with the transconductance feedback are designed and analyzed. Importance of device parasitic like gate to source capacitance, gate to drain capacitance and the output resistance influence the loop gain. This is brought in the design and emphasizes on the proper utilization of these parasitic in LNA design with transconductance feedback. Using a standard 90 nm CMOS process, LNAs have been demonstrated for 2-GHz frequency (S-band) applications. Operated at a supply voltage of 0.6 V, the gain and noise figure of single stage CS LNA with transconductance feedback are observed to be 17.9 dB and 2.1 dB respectively. It is noted that nearly 17% gain improvement has been achieved with excellent input reflection coefficient of -54.8 dB and low power consumption of 2.92 mW. Similarly, for a cascaded CS amplifier when operated at 0.6V, it is observed that the gain and noise figure are found to be 13.6 dB and 2.38 dB respectively. It is noted that nearly 6.25% increase in gain is achieved with appealing reverse gain of -52. 8 dB when compared to cascaded CS circuit without transconductance feedback. Higher reverse gain ensures the stability of the designed amplifier. Applications: The proposed work is needed in the design of transceivers working at S-band (2 GHz - 8 GHz). Few noticeable applications are: Communication satellites (NASA), weather radar systems, microwave ovens and optical communication which require low power modules. Improvements: This work can be further extended to reconfigure the input matching network so that UWB bandwidth is covered.Keywords
Cascaded Common Source (CS) Configuration, Low Noise Amplifier (LNA), MOS Parasitic, S-Band, Trasconductance FeedbackFull Text
- Flush Air Data Sensing System
Abstract Views :315 |
PDF Views:103
Authors
N. Shyam Mohan
1,
M. Jayakumar
1,
T. Sivamurugan
1,
K. C. Finitha
1,
S. B. Vidya
1,
Jayanta Dhoaya
1,
N. Remesh
1,
M. Prasath
1,
Shashi Krishna
1,
Aisha Sidhique
2
Affiliations
1 Vikram Sarabhai Space Centre, Thiruvananthapuram 695 022, IN
2 Liquid Propulsion Systems Centre, Indian Space Research Organisation, Bengaluru 560 008, IN
1 Vikram Sarabhai Space Centre, Thiruvananthapuram 695 022, IN
2 Liquid Propulsion Systems Centre, Indian Space Research Organisation, Bengaluru 560 008, IN
Source
Current Science, Vol 114, No 01 (2018), Pagination: 68-73Abstract
Flush air data sensing system (FADS) forms a mission-critical subsystem in re-entry vehicles. It makes use of surface pressure measurements from the nose cap of the vehicle for deriving air data parameters such as angle of attack, angle of sideslip, Mach number, etc. of the vehicle. These parameters are used by the flight control and guidance systems, and also assist in the overall mission management. The overall system engineering of FADS, including selection of pressure transducers, tubing size, port geometry, FADS algorithm and associated processing electronics along with the integration scheme is addressed in this article. Details of the qualification tests carried out in wind tunnel for end-to-end verification of the entire FADS system are covered in brief. Majority of the tests were carried out in a low-speed wind tunnel at a wind speed of 65 m/s (Mach number 0.2). The flight performance of FADS is also discussed in this article.Keywords
Angle of Attack, Flushed Air Data System, Hypersonic Flight Vehicles, Subsonic, Wind Tunnel.Full Text
References
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- Ellsworth, J. C. and Whitmore, S. A., Re-entry air data system for a suborbital spacecraft based on X-34 design. AIAA Paper 2007-1200.
- Ellsworth, J. C. and Whitmore. S. A., Simulation of a flush air data system for transatmospheric vehicles. J. Spacecraft Rockets, 2008, 45(4).
- Larson, T. J. and Siemers. P. M., Use of nose cap and fuselage pressure orifices for determination of air data for Space Shuttle Orbiter below supersonic speeds. NASA TP-1643, 1980.
- Larson, T. J., Whitmore, S. A., Ehernberger, L. J., Johnson, J. B. and Siemers, P. M., Qualitative evaluation of a flush air data system at transonic speeds and high angles of attack. NASA TP-2716, 1987.
- Rajeshkumar, G. V. et al., Calibration of air data systems using numerical simulation of supersonic flow over blunt forebody. In 20th National Convention of Aerospace Engineers, 29–30 October 2006, Trivandrum.
- Rajesh Kumar, G. V., Harish, C. S., Swaminathan, S. and Madanlal, Development of a flush air data system for a winged body re-entry vehicle. In 2nd European Conference for Aerospace Sciences (EUCASS), Belgium, France, 2007.
- Siemers, P. M., Paul, M., Henry, W. and Martin. W. H., Shuttle entry air data system (SEADS) – flight verification of an advanced air data system concept. AIAA paper 88-2104, 1988.
- Whitmore, S. A., Moes, T. R. and Larson. T. J., Preliminary results from a subsonic high angle of attack flush air data sensing (HI-FADS) system. Design, calibration and flight Test evaluation. NASA TM-101713, 1990.
- Whitmore, S. A., Davis, A. R. and Fife, M. J., Flight demonstration of a real time flush air data sensing (RT-FADS) system. AIAA Paper 94-3433, August 1995.
- Remesh, N., Jayakumar, M., Finitha, K. C., Abhay Kumar, Shyam Mohan, N. and Swaminathan, S., Pressure measurement sensitivity studies on a reusable launch vehicle (RLV) flush air data sensing system (FADS). In Proceedings of National Conference on Space Transportation Systems, Opportunites and Challenges (STS 2011).