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Ananthkrishnan N.,KAIST | Bansal R.,Indian Institute of Technology Bombay | Jain H.,Massachusetts Institute of Technology | Gupta N.,IDeA Research and Development P Ltd.
International Journal of Control, Automation and Systems | Year: 2010

Adaptive feedback linearizing control schemes are used to suppress limit cycle oscillations in nonlinear systems where the system parameters are either unknown or uncertain. Parameter convergence is desirable in these schemes as it provides a measure of robustness of the scheme and also permits the unknown/uncertain system parameters to be estimated. In recent work, we have shown how using a persistently exciting forcing it is possible to achieve parameter convergence in nonlinear limit cycling systems. In practice, however, limits on the control input to the plant due to saturation must be considered, and the main goal of this work is to analyze the effect of input saturation on parameter convergence in an adaptive feedback linearization framework. In particular, a technique known as control hedging is incorporated and the effectiveness of this method for very severe saturation constraints has been evaluated. Results are presented for a single degree-of-freedom wing rock dynamics model and a multi degree-of-freedom combustion acoustics model showing successful parameter convergence even in the presence of input saturation. © ICROS, KIEE and Springer 2010.

Walambe R.,Coral Digital Technologies P Ltd | Gupta N.K.,IDeA Research and Development P Ltd | Bhange N.,Coral Digital Technologies P Ltd | Ananthkrishnan N.,Coral Digital Technologies P Ltd | And 4 more authors.
Defence Science Journal | Year: 2010

Failure of sensors used to provide a feedback signal in control system can cause serious deterioration in performance of system, and even instability may be observed. Based on knowledge of aircraft engine systems, the main cause of fault in such air-breathing combustion systems (ACS) with no rotating parts is due to the pressure sensors. Fast online detection of faults before the error grows very large and accommodation is critical to the success of the mission. However, at the same time, it is necessary to avoid false alarms. Hence, early detection of small magnitude faults with acceptable reliability is very challenging, especially in the presence of sensor noise, unknown engine-to-engine variation and deterioration and modeling uncertainty. This paper discusses the novel fault detection and accommodation (FDA) algorithm based on analytical redundancy based technique for ACS. © 2010, DESIDOC.

Park I.-S.,Korea Advanced Institute of Science and Technology | Ananthkrishnan N.,Korea Advanced Institute of Science and Technology | Tahk M.-J.,Korea Advanced Institute of Science and Technology | Vineeth C.R.,IDeA Research and Development P Ltd. | Gupta N.K.,IDeA Research and Development P Ltd.
Journal of Propulsion and Power | Year: 2011

A low-order model for buzz oscillations in the intake of a ramjet engine is presented. The model combines the dynamics of the intake and the subsonic combustor and the interaction between them, and accurately represents the different physics of the intake in subcritical and supercritical operation. A change in combustor pressure can be felt all the way to the cowl lip, and it affects the mass flow entering the intake duct. An increase in combustor pressure (Pc) will encourage spillage at the cowl lip, reducing the mass flow rate, whereas a decrease in Pc can draw more air mass flow into the intake, and with it perhaps also suck the shock back into the intake. The oscillations build up to constant amplitude and fixed frequency, typical of limit cycles. The model yields a nonlinear, switched dynamical system that, when simulated for a typical ramjet engine configuration, shows limit cycle oscillations of a character and frequency similar to those observed in experiments in similar systems.

Gupta N.K.,IDeA Research and Development P Ltd | Goel R.,Airbus | Ananthkrishnan N.,Korea Advanced Institute of Science and Technology
Defence Science Journal | Year: 2011

Design and development of an autonomous quadrotor micro aerial vehicle is undertaken following a systematic approach. A fairly detailed model was constructed and simulations were then carried out with the purpose of refining the baseline design, building a controller, and testing the flying qualities of the vehicle on a ground-based flight simulator. Following this, a smooth transition to rig and flight testing has been enabled in a cost-and time-effective manner, meeting all the design requirements. © 2011. DES1DOC.

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