Aircraft trajectory optimization under wind effect by using optimal control : Environmental impact assessment

Abstract

The aim of this thesis, Aircraft Trajectory Optimization Under Wind by Using Optimal Control and Environmental Impact of Aviation in terms of Aircraft Emissions, is to find the wind and weather optimized aircraft trajectories in the cruise phase by minimizing fuel consumption, time and air pollutants. Flight trajectories calculated by taking into account the wind factor are considered as a critical measure in terms of reducing fuel consumption. In addition, it is known that the models examined by including weather information give more realistic results than those that are not included. Trajectory planning calculations consist of various elements such as wind forecasts, operational constraints, amount of fuel, aircraft performance, atmospheric conditions. Temperature, pressure and air density parameters are considered standard atmospheric values. The performance model used is based on BADA. In order to achieve the aims of the thesis, first of all, the problem has been tried in 2 dimensions in terms of reducing complexity of operations. At this stage, the wind equation, which was created with a simple calculation, was added to the EoM in horizontal plane. The effect of the horizontal components of wind is clearly seen in the numerical simulation. Secondly, the problem was created according to BADA 3 and solved in a way that minimizes flight time and fuel in 3 dimensional space. Simultaneously, a wind model has been created with the wind tabular data obtained from the Global Forecast System (GFS). The GFS is a weather forecast model developed by the National Centers for Environmental Prediction (NCEP). In this study, wind factor was assumed to be stationary, wind uncertainty was not included in this study. Since there are erroneous measurements in the wind tabular data obtained from the Global Forecasting System (GFS), the data was improved by applying the interpolation method first and the error difference between the real data and the interpolated data was arranged to be the least. Then, with the smooth data, wind equations were obtained separately for seven barometric altitude levels. Thirdly, in addition to flight time and fuel consumption, an emission model was created based on the ICAO Engine Exhaust Data Bank [29] and Boeing Method 2 [30] to solve the multi-objective optimization problem. The developed new model was applied to the simulation environment created based on BADA 4. Finally, the wind equations in the horizontal plane obtained were included in the simulation environment developed on the basis of BADA 4, and the targeted model was created. Predetermined routes were filtered from the actual flight plan selected for the same day with the wind data to be examined in the case studies. The flight area was determined and a wind model was obtained for that region. All one-day flights for the selected route were examined. Wind equations are calculated by taking flight hours into account. The simulation results were obtained according to the flight information of the desired route obtained from the real flight plan. The optimized trajectories were calculated in the simulation environment by referring to the points where the aircraft started and ended the cruise phase. Thus, Turkish airspace, which has not been examined before, is presented as a case study specific to Istanbul-Ankara flights. As a second case study, European airspace is presented specific to Paris-Frankfurt flights. During these studies, it was clearly seen that cruising speed and cruising altitude are critical for fuel consumption under the wind effect. In addition, as a result of these studies, it has been shown that the proposed model gives more effective results as the flight distance increases. This study consists of five chapters describing the stages of the thesis. The first chapter is a general introduction to the thesis topic. The thesis topic is explained and its aims are mentioned, the importance of the subject and why it is needed are presented. This section consists of three sub-titles. First of all, the scope and contributions of the thesis are mentioned. Afterwards, a wide literature review was made and studies in this field were presented. Finally, the structure of the thesis is mentioned. In the second chapter, the mathematical model required for this study is explained. Wind-optimized trajectories for an aircraft in the cruise phase are generated by solving a non-linear optimal control problem. For this reason, first of all, the general representation of the optimal control problem and its solution techniques are mentioned. The suitability of these solution techniques to the problem is discussed and the method to solve the problem is explained. It is known that multi-objective optimization problems give more realistic and ideal results than single-objective optimization problems. After this part, multi-objective optimization problem and constraints are defined. In the last part, the optimal control problem solution method is mentioned. GEKKO Python optimization module was used for numerical simulation in solving the aircraft trajectory optimization problem. This algorithm was developed to analyze the environmental impact of emitted aircraft emissions such as nitrogen oxides and carbon dioxide, using real air traffic data. In the third chapter, models used in trajectory generation optimized for wind and weather conditions are introduced. First, the assumptions are mentioned. Afterwards, the atmosphere model, aircraft performance model, wind model and emission model are explained in detail. In addition, the equations of motion of the aircraft in 2D and 3D are shown in this section. In the fourth chapter, two case studies on the subject and their results are presented. First of all, it is the main contribution to the literature to analyze the flights over Turkey, which has not been focused on before as a case study. First, the problem is defined in the case analysis. Then, the wind field over the Turkish airspace was examined and a wind model was created. The wind equations of the region, which was extracted to include Istanbul and Ankara, were obtained and added to the equations of motion of an aircraft, as explained in wind model section in third chapter. In the simulation environment created in this direction, the most optimized trajectories were calculated considering the Istanbul-Ankara flights. As the second case study, Paris-Frankfurt flights over European airspace were analyzed. As in the first application, after defining the problem respectively and examining the wind field covering the flight points, the multi-objective optimization problem was solved for this route. As a result of the case studies, the actual and calculated flight time, fuel consumption, NOx and CO2 emission findings for each flight are presented comparatively. In the fifth and also the last chapter, the results and other studies that can be done in this field are mentioned. The values obtained as a result of the case analyzes are emphasized again. Within the scope of the study, it has been shown that the adverse impacts of aviation on the climate are reduced by trajectory optimization, which is resolved by evaluating wind and environmental effects. The topics that can be studied on the basis of this study in the future are mentioned.