An uncrewed, electric, autonomous aircraft travelling at 75 kilometres per hour lands gently on the roof of a moving car. For the first time, researchers at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) have successfully demonstrated a technique developed for this purpose. The system could be applied to ultralight solar-powered aircraft that complement conventional satellite systems while flying in the stratosphere. Eliminating the landing gear significantly increases the payload capability of a solar-powered aircraft – it is easier to land during crosswind conditions, making landings in unfavourable weather conditions possible.
Ultralight solar-powered aircraft can fly at altitudes in excess of 20 kilometres and stay airborne for several weeks; weight is crucial for long-duration flights. By omitting the landing gear, the weight of an Uncrewed Aerial Vehicle (UAV) can be significantly reduced; this allows increased payload, greater range and enhanced performance. Reinforcements to the aircraft structure that would usually be necessary can also be eliminated, contributing to a further reduction in weight.
Combining technologies from the fields of robotics and UAVs, researchers from the DLR Institute of Robotics and Mechatronics have developed a system that enables a fixed-wing aircraft to land autonomously on a moving ground vehicle. This system has now been successfully tested using a three-metre, 20 kilogram, electrically powered fixed-wing UAV during flight trials at Mindelheim-Mattsies airfield in Bavaria. To accomplish this, the researchers fitted a special platform equipped with a number of optical markers to the roof of a car. The aircraft is able to navigate to a position – accurate to within 50 centimetres – above the four-metre-long by five-metre-wide mobile platform. An optical multi-marker tracking system recognises the landing platform and performs a highly accurate calculation of its position relative to the ground vehicle. Using this data, the landing phase is carried out under computer control.
The major advantage of this system is that the movement of the UAV and the vehicle can be automatically synchronised in real time using the algorithms that have been developed. This means that the landing platform situated on top of the car and the fixed-wing aircraft move at exactly the same speed and the landing is more like simply setting down, making the landing phase simpler and safer. In the experiments performed to date, flight operations safety requirements mean a driver was still present in the car. The driver received calculated control commands via a graphical display, which instructed faster or slower driving. In future, in practical applications, a robotic vehicle without a driver could be used.
The work received funding from the EU project ‘EC-SAFEMOBIL’.