1) Failure Boundary Estimation For Lateral Collision Avoidance Manoeuvres
Jan 1, 2014 IEEE - American Control Conference 2014
This paper proposes a method for predicting the point at which lateral collision avoidance manoeuvres fail. It starts by defining the kinematic failure boundary for different encounter geometries and velocities. This relies on the assumption that the ownship aircraft is able to turn instantaneously. A simple trajectory model is then developed to improve the prediction, and with the knowledge of the kinematic boundary, two optimisation algorithms are used to estimate the true failure boundary. When the intruder is travelling quickly when compared to the ownship aircraft, results have shown that the failure boundary is much larger due to the growth of the kinematic boundary. Knowledge of the failure boundary is then used to determine collision avoidance logic to ensure the correct decision is always made. Knowledge of the boundary reduces the size and complexity of the verification problem, and allows sensor resolution requirements to be formally set.
2) Estimation of time to point of closest approach for collision avoidance and separation systems
Jul 9, 2014 IEEE - UKACC 2014
This paper proposes a method for estimating the amount of time until the point of closest approach (TPCA) between two aircraft. A range of simple methods which use derivatives to estimate the time to collision are analysed. These methods are only accurate when the angle subtended between the direction of the relative velocity vector, and the bearing of the intruder aircraft is small. An extended method is developed which calculates the exact TPCA from relative distance and bearing measurements. Representative levels of Gaussian white noise are introduced to the core equation variables for both the derivative and extended methods. It is found that as we increase the value of θ, the extended method's accuracy increases beyond that of the derivative method. A fusion algorithm is developed to switch between methods and is shown to perform well for a range of conflicts. When the relative velocity between the two aircraft is small, the signal to noise ratio on the relative velocity variable reduces causing large errors to the TPCA estimation. It is therefore concluded that at a certain relative velocity threshold, Vk (dependant on sensor and filter performance) both the derivative and extended TPCA estimation methods would become undesirable as risk estimators. It is suggested that in these situations distance could be better to use since it can be measured directly.