ARCADE, which stands for Autonomous Rendezvous Control And Docking Experiment, is a technology demonstration project carried out by a team of students of the University of Padova. The project was developed in the framework of the programme REXUS/BEXUS, which gives European students the opportunity to launch their experiment on-board sounding rockets or stratospheric balloons. ARCADE participated to the balloon launch campaign BEXUS 13 and 17. The official final result of ARCADE-R2 is 75% of success.
ARCADE is a testbed composed by three main parts:
- a 2 degree-of-freedom small vehicle called SMAV
- a fix assembly called PROXBOX
- the supporting srtucture STRUCT
The SMAV is a mockup representing a small space or aerial vehicle. It is equipped with a reaction wheel for attitude control, an infrared sensor for relative navigation and a docking probe.
The PROXBOX contains most of the electronics of the experiment, pressure and temperature sensors as well as the docking receptacle.
The STRUT features wind speed and direction probes.
The SMAV attitude is controlled by means of a custom reaction wheel. Both standard PID and state space controllers were developed and tested successfully.
Relative navigation between the SMAV and the PROXBOX is performed exploiting a custom infrared sensor, composed by a LED beacon mounted on the PROXBOX and two photodiode receivers placed on the vehicle. Thanks to an accurate model of the LED emission, the sensor logic can determine in real time the SMAV distance and attitude relative to the PROXBOX from the output voltage of the receivers.
ARCADE features a miniaturized docking system based on the drogue-probe configuration. The system is capable of both soft docking and rigid connection. Soft docking is performed exploiting an electromagnet on the PROXBOX and a magnetic tip mounted on the vehicle. Once magnetically captured, the vehicle is pulled towards the docking interface, where three latches secure the probe to the drogue, realizing the rigid connection.
ICE & COLD!
ARCADE is conceived to fly on-board a stratospheric balloon launched from the Esrange Space Centre, in northern Sweden. During the flight, the balloon is expected to reach a maximum altitude between 24 and 30 km, while temperature and pressure can drop down to -90°C and 10 mbar. Such conditions pose a severe challenge for the functionality of an experiment! To protect all the delicate devices, ARCADE was provided with heaters and special insulation materials for space applications.
During the flight, the infrared sensor outputs were constantly read and expolited to determine the SMAV rotation and linear position in real time. Here is an example of the data gathered and post-processed. The SMAV position (top) and rotation (bottom) estimated are characterized by uncertainty of 5mm and 1.5 deg, respectively.
TEMPERATURES & PRESSURE