Reference Governor Strategies for Vehicle Rollover Avoidance

This paper addresses the problem of vehicle rollover avoidance using reference governors (RGs) applied to modify the driver steering input in vehicles with an active steering system. Several RG designs are presented and tested with a detailed nonlinear simulation model. The vehicle dynamics are highly nonlinear for large steering angles, including the conditions where the vehicle approaches a rollover onset, which necessitates RG design changes. Simulation results show that RG designs are effective in avoiding rollover. The results also demonstrate that the controllers are not overly conservative, adjusting the driver steering input only for very high steering angles. IEE

Perpetual Dynamic Soaring in Linear Wind Shear

A study was conducted to analyze dynamic soaring in linear wind shear and discuss the necessary and sufficient conditions to enable sustainable flight with dynamic soaring. The system under analysis was defined by a wind shear model with constant vertical velocity gradient and the aircraft equations of motion, which model the aircraft behavior when subject to a wind gradient. The study defined the inequalities that characterized the sufficient and necessary conditions for dynamic soaring. The conditions were applicable to a wide variety of unmanned aerial vehicles (UAVs), allowing the determination of the suitability of an aircraft for dynamic soaring under different environmental conditions. The equations of flight dynamics based on the flight-path and the lift were also derived in the study. The investigations derived the necessary and sufficient conditions for sustainable dynamic soaring as an explicit function of several aircraft and environment parameters. The characterization of the minimum vertical wind gradient dependence on environmental and aircraft parameters was obtained by running multiple trajectory optimizations, evaluating a range of values for several parameters

Reference Governor Strategies for Vehicle Rollover Avoidance

This paper addresses the problem of vehicle rollover avoidance using reference governors (RGs) applied to modify the driver steering input in vehicles with an active steering system. Several RG designs are presented and tested with a detailed nonlinear simulation model. The vehicle dynamics are highly nonlinear for large steering angles, including the conditions where the vehicle approaches a rollover onset, which necessitates RG design changes. Simulation results show that RG designs are effective in avoiding rollover. The results also demonstrate that the controllers are not overly conservative, adjusting the driver steering input only for very high steering angles. IEE

Atmospheric flow field models applicable for aircraft endurance extension

We present a survey of atmospheric flow field phenomena models. The studied models are selected for their potential use toward extended aircraft endurance. This work describes several flow field phenomena, i.e., air flow currents and flow velocity variations. In particular, we discuss wind shear, thermal updrafts, and gusts. We study several wind shear models, such as the Surface, Layer, and Ridge Wind Shear models, comparing their characteristics. We also describe and compare thermal updraft models, such as the Chimney and the Bubble Thermal models. To close, we review different gust models. Throughout this work, we studied several existing models, but we also introduce new ones and improved versions of existing ones. The Bubble Thermal, Layer Wind Shear, and the Ridge Wind Shear models are examples of the new models presented. Furthermore, we present the Chimney Thermal model improvements, which take into account the phenomenon interaction with the prevailing winds

Homing Guidance Using Spatially Quantized Signals

This paper considers homing guidance for a vehicle with a single omnidirectional receiver traveling to a stationary, omnidirectional transmitting beacon by using spatially quantized signal strength measurements. Two homing strategies are presented, and simulations are performed for cases with signal noise and vehicle turn rate limits. The first strategy is the Oyler strategy, which adapts a sliding mode controller and observer from the previous work. The second strategy is based on constant heading changes (CHCs) each time a range increment is detected, and this strategy is shown to be sufficient for homing. This study also discusses a signal filter designed to improve the homing controllers' performance. Performance metrics are developed for strategy evaluation and parameter optimization. The performance of each guidance strategy is shown through simulations for a variety of conditions. The Oyler strategy guides the vehicle to the beacon more efficiently than the constant heading change strategy, but it comes with a slight penalty in success rate

A greedy policy for fleet-level radar resource management

A model for a phased-array radar in the context of a defensive Naval system has been developed using hierarchical finite state machines. This model is used to study resource management for a fleet of ships equipped with one radar unit each. This fleet is under attack from aerial enemy agents. A control algorithm formulated on this specific model is used to dynamically generate a greedy policy for radar operation. The defense system is evaluated in its capability to acquire and track those aerial threats, in two configurations -centralized and decentralized (independent). The performance is quantified on the basis of time taken to establish the threat trajectory, time to compute the policy and the number of threats the system fails to track. A comparison of performance in the two configurations is provided. ©2013 IEEE