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Prathap H.,College of Engineering, Trivandrum | Brinda V.,VSSC
Proceedings of the IEEE International Conference on Control Applications | Year: 2013

Due to the inherent nonlinearities of Reusable Launch Vehicle (RLV) dynamics, its changing properties during flight and the engineering difficulties to predict its aerodynamics with high levels of fidelity, flight control requires strategies that allow to cope up with the non-linearity of the model and assure robustness in the presence of inaccuracies and changes in configuration. This paper presents a flight control strategy based on dynamic inversion controller which is designed for the re-entry phase of Reusable Launch Vehicle. In order to solve the robustness problem of regular explicit Nonlinear Dynamic Inversion (NDI) control law, the Incremental Nonlinear Dynamic Inversion (INDI) control law is proposed. Sensitivity to model mismatch is eliminated by feeding back state acceleration in INDI approach. The improved control law design is validated for re-entry phase of RLV for nominal and aerodynamic perturbation cases. Analysis of simulation results reveal that the robustness of the control law is increased. © 2013 IEEE.

Jaison H.,Karunya University | Anas S.R.,National Institute of Technology Calicut | Gopinath A.,VSSC | Subathra M.S.P.,Karunya University
2011 International Conference on Emerging Trends in Electrical and Computer Technology, ICETECT 2011 | Year: 2011

This paper presents, an Electro-Mechanical Actuator (EMA) based position control system with redundancy technique is being presented. The servo system is composed of two chains, a prime chain and a redundant chain, which includes the position servo system of the EMA. Only one chain works at a time, probably the main chain operates during normal condition of the system. A new, simpler fault detection and isolation (FDI) technique is being developed, which will be monitoring the prime chain continuously. If any type of fault occurs in the prime chain, the FDI isolates the prime chain from the system and switches to the redundant chain. Thereafter redundant chain will be driving the system. The system model is then simulated using MATLAB/Simulink, with trapezoidal waveforms of backemf. Using the DSP controller chip, TMS320F2812 as a control core, hardware implementation has been carried out. © 2011 IEEE.

News Article | January 2, 2016
Site: www.techtimes.com

The trial for the Indian Space Research Organisation (ISRO)'s reusable launch vehicle is set to be initiated in 2016. Originally planned for Dec. 28, the launch was postponed to help reduce technical slags, the ISRO chairman said. The ISRO scientists previously experienced some technical difficulties, prompting them to move the launch date to April 2016. The launch could have been set for February but because there were other launches already planned, the ISRO decided on moving it two months later. The Reusable Launch Vehicle-Technology Demonstrator (RLV-TD) was developed by Thumba-based Vikram Sarabhai Space Centre (VSSC). The development of this vehicle will reduce the cost of access to space in the future. Though it is a single-stage rocket, it possesses a solid propellant stored in casing and it can be reused to reduce the cost of launches, which is a major hindrance in promoting space exploration by many countries. The development of a reusable launch vehicle will help many countries achieve low-cost and reliable space access. "ISRO will complete the design in 2016. The aim is to bring back the vehicle from the orbit and test if this process is economically viable. The objective is to access space with best minimum cost possible," ISRO Chairman A.S. Kiran Kumar said. "We still have a long way to go and have taken baby steps in this direction," he added. The RLV-TD is a scaled prototype of the Avatar space shuttle in India and it can return to Earth after performing its mission. If the project will be successful, this can pave the way to ISRO being the pioneer in reusing a launch vehicle. When launched, the RLV-TD will go up to around 70 kilometers or 43 miles and go back to Earth through the help of a space plane. It is expected to land on the Bay of Bengal to be retrieved. More test flights will be conducted, and when successful, a reusable launch vehicle will finally be used from 2025 onwards. The Reusable Vehicle-Technology Demonstration Program is a series of missions that will help develop a Two Stage To Orbit (TSTO) fully reusable vehicle. Test flights can help test and evaluate space technologies including hypersonic flight, powered cruise flight, hypersonic flight using air-breathing propulsion and autonomous landing. The program will include a lot of experiments including hypersonic flight experiment, landing experiment, return flight experiment and the scramjet propulsion experiment. The RLV-TD project was started in January 2012 and now, it is undergoing flight integration before it is moved to Bengaluru for acoustic testing and then to Sriharikota in preparation for the launch in April 2016. India is not far behind other countries in terms of space exploration. In fact, 2015 was a great year for ISRO for its achievements all year round. The organization launched the following: a Mars orbiter, a multi-wavelength space observatory, and a Geo-Synchronous Satellite Launch Vehicle (GSLV-D6), which carried a GSAT-6 communication satellite into orbit.

Basheer B.,VSSC | Mathew D.,Polymers and Special Chemicals Group | George B.K.,VSSC | Reghunadhan Nair C.P.,Polymers and Special Chemicals Group
Solar Energy | Year: 2014

The development of hybrid solar cells such as Dye Sensitized Solar Cell (DSSC) opens up a new generation of thin film solar cells with. high performance to cost ratio. They are expected to be one of the. most economically viable energy devices, owing to the potential for. realization of flexible and light weight, thin film photovoltaic devices. with moderate efficiencies and good processability in non-vacuum settings. Sensitizers form the heart of DSSC since they trigger and maintain the. electron transfer processes in a photo electro chemical system by absorbing. solar radiation. This review focuses on recent advances in sensitizers. developed/explored elsewhere. A comprehensive analysis of the performance. of various light absorbing sensitizers based on their chemical. structure, geometry and stereo chemistry is attempted. © 2014.

Joseph T.,Indian National Institute for Interdisciplinary Science and Technology | Sebastian M.T.,Indian National Institute for Interdisciplinary Science and Technology | Jantunen H.,University of Oulu | Jacob M.,James Cook University | Sreemoolanadhan H.,VSSC
International Journal of Applied Ceramic Technology | Year: 2011

The Sr2ZnSi2O7 ceramics sintered at 1475°C has εr=8.5, Qu× f=105,000 GHz (at 12.63 GHz), and τf=-51.5 ppm/°C. The sintering temperature of Sr2ZnSi2O7 has been lowered to 875°C by the addition of 20Li2O-20MgO-20ZnO-20B2O 3-20SiO2 (LMZBS) glass. Addition of a small amount of SrTiO3 lowered the value of τf. Tapes were cast using the composition Sr2ZnSi2O7+15 wt% LMZBS. The stacked and sintered tapes exhibited εr∼7 and tan δ∼10-3 at 290 K. The chemical compatibility of Ag with the ceramic-glass composites was also investigated. © 2010 The American Ceramic Society.

Saritha A.,Amrita University | Saritha A.,Sb College | Joseph K.,Indian Institute of Space Science and Technology | Thomas S.,Mahatma Gandhi University | Muraleekrishnan R.,VSSC
Composites Part A: Applied Science and Manufacturing | Year: 2012

The field of polymer nanocomposites has attracted attention as a method of enhancing polymer properties and extending their utility by using molecular or nanoscale reinforcements rather than conventional particulate filled nanocomposites. These materials exhibit behavior different from conventional composite materials with micro scale structure due to small size of structural unit and high surface to volume ratio. Chlorobutyl rubber nanocomposites were prepared using organically modified cloisite 15 A and characterized using XRD and TEM. The gas barrier properties of the nanocomposites were modeled using the composite theories of permeation and the tortousity factors were predicted. Analysis of mechanical properties, transport and gas barrier properties of the nanocomposites as well as the calculation of break through times show the effectiveness of the material to be utilized as potential gas as well as VOC barrier materials. © 2012 Elsevier Ltd. All rights reserved.

Joseph T.,Indian National Institute for Interdisciplinary Science and Technology | Sebastian M.T.,Indian National Institute for Interdisciplinary Science and Technology | Sreemoolanadhan H.,VSSC | Sree Nageswari V.K.,VSSC
International Journal of Applied Ceramic Technology | Year: 2010

CaMgSi2O6 (CMS) ceramics prepared by the solid-state ceramic route have a sintering temperature of 1300°C/2 h. The sintering temperature of CMS was reduced below the melting point of Ag using low-melting LBS and LMZBS glasses. In the case of CMS+15 wt% LMZBS sintered at 900°C/2 h, the dielectric properties obtained were εr=8.2, Qu × f=32,000 GHz (10.15 GHz), and τf=-48 ppm/°C. The CMS+15 wt% LBS composite, sintered at 925°C/2 h, showed εr= 8, Qu × f=15,000 GHz (10.17 GHz), and τf=-49 ppm/°C. The chemical compatibility of Ag with the ceramic-glass composites was also investigated for low-temperature co-fired ceramic applications. © 2009 The American Ceramic Society.

Anjaly P.,College of Engineering, Trivandrum | Swaminathan S.,VSSC
2016 Indian Control Conference, ICC 2016 - Proceedings | Year: 2016

An adaptive integrated guidance and control scheme is developed for the entry phase of winged RLV. The reference profiles are generated off-line using constrained optimization techniques to take care of all possible variations in initial conditions and path constraints. Lateral and longitudinal guidance commands are generated in-flight with the help of stored reference profiles to meet the boundary conditions. Non-linear dynamic inversion is used to design inner loop control. Unpredicted failures like control surface saturations, aerodynamic uncertainties, chattering of control surfaces are addressed by the bandwidth adaptation logic. The integration of the guidance and control loop is achieved by a feedback from control to guidance section, thereby making the guidance loop adaptive to changes in the control bandwidth. In this way, the guidance subsystem generates feasible trajectories that ensure safe flight of RLV despite unpredicted scenarios. The integrated scheme is simulated extensively in 6 Degrees of freedom (DOF) environment along with non-linear actuator dynamics to validate the algorithm. Robustness of the proposed method is demonstrated using Monte Carlo simulations with various failure modes and plant parameter uncertainties. © 2016 IEEE.

Skariya S.E.,College of Engineering, Trivandrum | Sebastian B.,VSSC | Namboodiripad M.N.,CECG
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2014

Reusable Launch Vehicle (RLV) is used to carry payload from earth's surface to the outer space for more than once.The digital autopilot (DAP) used to control the RLV has an actuation system as its inner loop. The actuation system deflects the control surfaces (eg. fins) to bring about the necessary control action. The actuator is a complex system with many elements which work in co-ordination to bring about the necessary action. But in the design of autopilot, actuator is usually approximated as a second order system having the same bandwidth as that of the actual one. Due to this approximation, an understanding of the entire plant cannot be achieved. During implementation, the approximation of the order of the actuator may lead to deviation of the performance of the system from its specifications. It may also lead to unnecessary control of subsystems which would have been corrected without any control in an integrated model. In this paper, an integrated design of the RLV and its actuation system is developed. The actuation system consists of an electro hydraulic actuator and the associated elements. It is designed to actuate the booster fin of an RLV for the purpose of pitch control. The Linear Quadratic Regulator (LQR) control technique is used to design DAP for the integrated system. LQR is a modern control technique which ensures optimality in the design of the integrated system. A comparison of the performance of the integrated design of RLV and the design with an approximated second order actuator is made. The advantages of LQR technique over the conventional gain design technique are also mentioned. © 2014 IFAC.

Mutyalarao M.,VSSC | Raj M.X.J.,VSSC
Proceedings of the International Astronautical Congress, IAC | Year: 2015

Optimal control of lunar soft landing trajectories in two-dimensional approach is presented in this article. The problem is complex due to the presence of system constraints and local minima. To solve the time-history of control parameters, the problem is converted into two point boundary value problem by using the maximum principle of Pontrygen. Methodology utilizes an optimization technique called Taboo Evolutionary Programming (TEP). The study explores the integration of TEP technique in solving the governing non-linear differential equations of control of a lunar soft landing trajectory problem. For the specified perilune altitude a solution of thrust profile during powered braking phase is generated. The results are compared with available results in literature and it shows that the solution of present algorithm is comparable to the counterpart. Further, sensitivity of design parameters such as terminal altitude, true anomaly, and terminal velocity over the final landing mass at the touch down is also examined. © Copyright 2015 by International Astronautical Federation. All rights reserved.

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