Exploiting solar energy allows for zero-emission flying. Besides from photovoltaics, free energy is directly available in the form of thermal updrafts.
Glider pilots have been using this source of energy for a long time, covering distances up to 1000 miles. To compare sportive accomplishments, pilots use GNSS-devices to log their flights and upload the recordings to web sites. At the institute of flight mechanics and control, we are developing methods to analyze this database. Linking those records to meteorological information allows us to estimate the updraft situation given the present weather conditions.
The resultant updraft estimation is then used to compute an energy-efficient flight path. We investigate probabilistic approaches to refine the updraft estimate based on measurements taken in flight. The optimal flight path is ongoingly adjusted according to the most recent updraft estimate. Doing so requires a constant trade-off between mission objectives, exploration, and updraft exploitation.
Within the project TakEOF, we investigate and apply artificial intelligence to predict, estimate, and exploit thermal updrafts.
- P. Groß, S. Notter und W. Fichter, „Estimating Total Energy Compensated Climb Rates from Position,“ in AIAA Scitech 2019 Forum, San Diego, 2019.
- S. Notter, M. Zürn, P. Groß und W. Fichter, „Reinforced Learning to Cross-Country Soar in the Vertical Plane of Motion,“ in AIAA Scitech 2019 Forum, San Diego, 2019.
- S. Notter, P. Schrapel, P. Groß und W. Fichter, „Estimation of Multiple Thermal Updrafts Using a Particle Filter,“ in AIAA Guidance, Navigation, and Control Conference, Kissimmee, 2018.
As emissions by aircraft are deemed particularly climate-damaging and contribute a growing share to global CO2 emissions, electric propulsion receives increasing attention. Besides its potential of emitting zero emissions at high altitude, the scalability and low complexity of electric motors allow their use in new configurations as „distributed, electric propulsion“. A larger number of small, electrically driven propellers could reduce energy consumption by using propeller-wing interaction effects for higher aerodynamic efficiency. From a flight mechanics point of view distributed, electric propulsion opens up new possibilities for flight control.
The iFR develops and operates an unmanned, autopiloted, modular test platform (picture) in collaboration with the Institute of Aircraft Design (IFB) at the University of Stuttgart to investigate new configurations based on distributed, electric propulsion with respect to performance and efficiency. The test platform is a scaled (1:3) version of the record-winning e-Genius aircraft that can be equipped with additional electric motors in various configurations. Currently, the test platform is used as part of the LuFo V.3 project ELFLEAN to measure the influence of electrically driven wing-tip propellers on the induced drag. The UAV is equipped with an autopilot developed at the iFR which provides highly accurate trajectory tracking for automated flight testing, yielding a test setup with high accuracy and repeatability.
At the same time the UAV is used to develop and test algorithms for the efficient control of new, electric configurations. In order to also test this on larger, manned systems, the solar powered icaré aircraft operated by the IFB has been equipped with electrically driven wing tip propellers. Their use for yaw control has recently been demonstrated during manned flight tests.
- Pfeifle, W. Fichter, D. Bergman, J. Denzel, A. Strohmayer, M. Schollenberger and T. Lutz, „Precision Performance Measurements of Fixed-Wing Aircraft with Wing Tip Propellers" in AIAA Aviation Forum, Dallas, 2019
- Pfeifle, M. Frangenberg, S. Notter, J. Denzel, D. Bergmann, J. Schneider, W. Scholz, W. Fichter and A. Strohmayer, „Distributed Electric Propulsion for Yaw Control: Testbeds, Control Approach, and Flight Testing" in AIAA Aviation Forum, Reno, 2020 (submitted for publication)
The objective of the LUFO IV.4 FlySmart project was to fully automate the take-off and landing of a General Aviation aircraft (EASA CS-23). No ground based infrastructure (e.g., instrument landing system) was used. FlySmart was a joint project between Diamond Aircraft, Airbus Defense & Space, and the University of Stuttgart, represented by the iFR Institute for Flight Mechanics and Controls and the ILS Institute for Aeronautical Systems.
The motion planning, steering and flight control algorithms have been developed by the Institute of Flight Mechanics and Controls with the aim of ensuring the safe operation of the CS-23 aircraft in all phases of a mission. The entire flight plan has been represented as a trajectory using splines in a UTM-based Cartesian coordinate system. This allows accurate representation of landings all over the globe, even when single-precision algorithms are used. Flyability and comfort are already ensured in the planning by considering aircraft-specific parameters.
The flight controller is designed as a monolithic multivariable system (MIMO) and includes gain scheduling and anti-windup measures to ensure good system properties throughout the envelope and for various configurations.
The design and verification process includes software-in-the-loop and hardware-in-the-loop testing, including extensive Monte Carlo simulations to validate the robustness of the control system. The criteria for this are derived from the EASA CS-AWO specification for large aircraft (CS-25), which was adapted in the project to general aviation aircraft (CS-23).
A Diamond DA42 - aircraft registration OE-FMP - was used for the flight test. The flights took place in the summer of 2015 in Wiener Neustadt (A) and led to several successful automatic landings, the first of which took place on the 26th August 2015. The automatic take-off was demonstrated on the 18th September 2015.
- J. Stephan and W. Fichter, “Gain-Scheduled Multivariable Flight Control under Uncertain Trim Conditions,” in 2018 AIAA Guidance, Navigation, and Control Conference, American Institute of Aeronautics and Astronautics, 2018.
- F. Pinchetti, A. Joos, and W. Fichter, “Efficient Continuous Curvature Path Generation with Pseudo-Parameterized Algebraic Splines,” CEAS Aeronautical Journal, 2018.
- Federico Pinchetti, Johannes Stephan, Alexander Joos and Walter Fichter. 2016. FlySmart - Automatic Take-Offand Landing for an EASA CS-23 Aircraft (to be published)
- Reimund Kueke, Peter Mueller, Sebastian Polenz, Reinhard Reichel, Federico Pinchetti, Johannes Stephan, Alexander Joos and Walter Fichter. 2016. Fly-By-Wire for CS23 Aircraft - Core Technology for General Aviation and RPAS