Autonomous in-flight path planning to replace pure collision avoidance for free flight aircraft using automatic depedent surveillance broadcast

By the year 2020 the number of aircraft will have increased substantially and will be in 'Free Flight' (that is, ATC will be devolved to the aircraft rather than being ground based). As an aid to navigation a more advanced form of collision avoidance will be required. This thesis proposes a method of collision avoidance planning using Automatic Dependent Surveillance-Broadcast (ADS-B) and Dynamic Programming (DP). It in essence enables Air Traffic Control (ATC) from within the cockpit for remote or uncontrolled airspace and is a step toward Free Flight. Free Flight requires quite different strategies than those used in the present collision avoidance schemes. This thesis reviews the approaches to collision avoidance used in the Air traffic navigation and to similar problems in other industries. In particular it considers the extended problem of collision avoidance within the framework of path planning. This is a key departure from the approach to aircraft collision avoidance used in the industry to date. Path planning reflects the real goal of an aircraft, which is to reach a particular destination efficiently and safely. Dynamic Programming is one solution method used in other industries for the problem of path planning to avoid collisions with fixed obstacles. The solution proposed herein for the Aircraft case uses Dynamic Programming applied to the moving obstacle case. The problem is first simplified by assuming fixed (static) obstacles for the cost minimisation algorithms. These fixed obstacles are then moved with time and the minimisation process is repeated at each time increment. Although this method works well in most cases, situations can be constructed where this method fails, allowing a collision. A modified approach is then used, whereby the movement of obstacles is included more explicitly (by modifying the shapes of the obstacles to represent motion) in the cost minimisation algorithm and a safe manoeuvre distance for each aircraft is used (by expanding the object size), to allow space for aircraft to execute safe evasive manoeuvres in difficult cases. This modification allows solutions which are complete (with no known cases of failure - collision situations) and should be considered as an important extension to the current Aircraft and Collision Avoidance System (ACAS). The testing of these solutions is focussed on the most difficult cases, and includes aircraft movement in 'real space' (that is simulations using real aircraft dynamics together with dynamic programming algorithms running in discrete time steps)