Mobile ground control station
Flight simulation and visualization in the experimental laboratory
One main part of every unmanned aircraft system is the ground control station. During the past activities at the Institute of Flight Systems, several different concepts have been realized, beginning with a simple tablet or laptop computer and a transportable ground station box with integrated data links. For a fast and trouble-free execution of flight tests, a specially-equipped transport vehicle is used since 2006. The car includes three full workstations with hardware, data links, internal network and power supply. Further, aircraft can be transported safely with fixed mounting in the car.
Flight data is transferred to the ground control station with different data links being available close to real-time. This allows the supervision, programming, and control during the flight experiments. The ground station includes instruments, diagrams, numerical displays, simulated outside-views of the test carrier and a map view for the operator. For redundancy, a safety pilot can control the vehicles with classic manual remote control in the case of failures or an emergency.
Simulation and testing environment
Parallel to the hardware development of the aircraft systems, considerable tools for modeling, simulation and control of the flying platforms have been developed. The so-called software-in-the-loop simulation allows a fast testing of new approaches and techniques and the adjustment of parameters on every workstation computer. After successful tests, the same experiments are run in the laboratory with the so-called hardware-in-the-loop simulation under much more realistic conditions. Here, the original aircraft hardware is used with emulated sensors. A real-time simulation system is taken for the calculation of sensory data based on the assumed model behavior and the environmental conditions. The achievable results are very close to a flight test, which reduces the chance of failures within the real flights.
The simulation can be connected to a visualization environment where the tests are displayed with a 3D rendering of real environments. For that, realistic 3D models of the different real flight testing areas are available.
For a simulation of image processing experiments, a special setup is available where one or multiple cameras are recording screens where the visualization environment is running from the perspective of the simulated camera on board the flight test carrier. This setup is advantageous not only for tests of the image processing algorithms by themselves, but also for realistic tests of the interaction between image processing and flight control. Special objects like artificial obstacles can be inserted into the visualization as a prediction of flight tests like this.
Reference measuring system
For the evaluation of current and developing future navigation techniques during the flight tests, a reference localization system is used that is independent of the aircraft itself, and also independent of satellite navigation systems. For this task, a robotic total station has been established which can continuously track and measure the position of a reflector at the aircraft with a laser. The installed system allows the automatic tracking of moving targets and a sampling rate of six measurements per second, and it enables the measurement of the 3D position with an uncertainty of a centimeter at ranges of up to several hundred meters to the vehicle. Hence, reference positioning is also available for flights into areas with limited satellite navigation, for example under bridges. With that, the developed navigation algorithms being capable of compensating temporary satellite signal dropouts can be evaluated under realistic conditions.