Department Publications

This paper presents on the stability analysis for RAVAN twin boom H-Tail Medium Scale UAV which has been developed by University of Moratuwa. It is required to understand the UAV behavior for the small perturbations in high altitudes while it is flying to be invisible. Indeed, without doing a proper stability analysis in different flying conditions, there is a high risk to fail the UAV for perturbations. Not only that but also it will help to optimize aerodynamic behavior for prolonging the flight endurance and effective deployment. The proper stability analysis will facilitate to increase the control flexibility.XFLR5 computational fluid dynamic software is used to do this stability analysis.

Since recently, UAVs (Unmanned Aerial Vehicles) have increasingly been recognized as a reliable, and effective means of aerial surveillance. Deployment of UAVs in disaster management for aerial surveillance and real-time video feed, when land access is cut off, is one of the most prominent applications. The ability of small, lightweight UAVs in aerial access and gathering data, in areas that are insecure or impossible for humans to reach has significantly improved remote accessibility. In this research, a new low cost small scale UAV with fully-fledged autopilot system on board the aircraft with the capabilities of following a predefined path and returning home autonomously has been designed, built, and tested successfully. This small-scale UAV is capable of navigating through given GPS coordinates at given altitude, while providing real-time flying status back to the ground control station.

Memory Based Event Triggering (MBET) is a pragmatic approach to reduce the effective sampling rate of a control system. In MBET, periodically sampled state variables and control inputs are encoded such that data transmission takes place only when they change by a value that exceeds a predetermined threshold. This results in a significant reduction of network traffic in Networked Control Systems (NCS). Should MBET encoding result in an asymptotic cyclic behavior (limit cycle like behavior), it would result in a lower bound in the required bandwidth. In this paper, the necessary conditions for the formation of such a cycle are investigated. It is demonstrated analytically as well as through empirical simulations that the main requirement for the occurrence of asymptotic dynamic cycles is a diffeomorphism between a scalar control input and a unique equilibrium point to which the system will converge to for a constant …

Frequently, a physical plant of a control system has an optimum operating point such as the spark (or injection) time of an internal combustion engine that results in maximum torque. Extremum Seeking Control (ESC) is a method of adaptive control capable of locating and maintaining a plant at such an optimum operating point in real time. It is capable of doing so with minimal a priori knowledge of the plant and can also track slowly varying changes. Input perturbed ESC schemes that use periodic dither signals have the disadvantage of requiring a high bandwidth for sampling and correlating the plant output with the dither signal. If the feedback path was to be implemented over a packet switched communication network, the high bandwidth requirement could result in increased congestion and consequently packet delays and dropouts. As a solution encoding using sporadic (aperiodic) sampling techniques can be used in the feedback path of the ESC scheme to reduce the required bandwidth. However, in order to ensure convergence of the ESC scheme with encoding, the effect of the signal reconstruction error due to encoding on the critical correlation stage has to be investigated. The contribution of this paper is an investigation of the convergence requirements and bandwidth performance of two encoding schemes; Memory-Based Event Triggering (MBET) and Event Triggered Adaptive Differential Modulation (ETADM). The results show that MBET can fail for objective functions with plateaus. ETADM fails when the number of ETADM steps used for reconstructing the plant output per perturbation cycle is too low to allow correlation. In terms of …