Zero-G Laboratory floating platform
Helping explore space by building earthbound robots. In the brand new issue of Raspberry Pi Official Magazine, Rob Zwetsloot investigates the final frontier.
Zero gravity is weird. Most of us can’t really conceptualise a weightless environment like you experience on space missions, and there’s even a difference between pressurised atmospheres inside a spacecraft and a vacuum as well. Even the tiniest variable can affect things. To better understand the various effects, special equipment has to be created.
“The Zero-G Laboratory is specifically designed to emulate scenarios like spacecraft rendezvous, docking, capture, and other interactions between spacecraft,” Barış Can Yalçin of the SpaceR team tells us. “It is equipped with advanced infrastructure, including space-like lighting conditions, a motion capture system, an epoxy floor, mounted robotic rails, and the capability to integrate onboard computers and large mock-ups. These features enable researchers to conduct a wide range of experiments for unique orbital scenarios, allowing for hybrid emulations with robots that integrate hardware and pre-modelled software components. The facility can be operated in real time and can accurately emulate orbital robotics scenarios.”
Filling a need
Space is still a huge industry, and labs like this are created to make sure missions are safe and reliable.
“Orbital Servicing, Assembly, and Manufacturing (OSAM), Active Space Debris Removal (ADR), and Asteroid Mining (AM) are becoming increasingly significant in both research and commercial sectors,” Barış says. “Earth’s orbits are filling up with outdated space assets, while the number of planned missions is set to rise sharply in the coming years. Additionally, there are plans to establish multiple space stations and large structures in Earth’s orbits over the next decade, which will be partially assembled and/or manufactured in space. These activities require higher levels of autonomy and close interaction. To ensure safe, secure, and reliable in-orbit operations, it is essential to validate and verify Guidance, Navigation, and Control (GNC) algorithms on the ground before launching missions. Consequently, there is a growing need to develop effective experimental setups for testing these algorithms. Therefore, in academia and in industry, floating platforms have been developed and frequently used by many institutions to emulate orbital robotics scenarios.”
Where does Raspberry Pi come in with this scenario? Its small size, low cost, and huge support and compatibility — along with ROS (Robotics Operating System) being available to use with Raspberry Pi — allow it to perform a great many functions for a project like this. Image processing, data analysis, control algorithms, wireless connectivity, and more make Raspberry Pi ideal for prototyping, then embedding in, systems like this.
Some light construction
The system works, to put it reductively, like an air hockey table. The floating platforms have an ‘air-bearing’ that levitates them off the floor a little like a hovercraft, and they have a series of nozzles that grant 3 DoF (degrees of freedom) — they can move along the X and Y axes, and rotate around the Z axis. For this to work, the platform needs to be light.
“The floating platform is constructed using additive manufacturing with lightweight carbon-fibre material, which helps extend experiment duration, allowing for the emulation of complex scenarios in the Zero-G Lab,” Barış explains. “The lighter the floating platform, the less compressed air it consumes. Moreover, the floating platform features a modular design, allowing easy disassembly of the middle and upper plates, which can also serve to carry equipment for various emulation scenarios. Its string-like topology provides ample space for mounting multiple components. 3D-printed supports can be easily integrated into the string structure, enabling the assembly of additional equipment such as debris removal systems, debris mock-ups, refuelling or docking mock-ups, sensors, and more. Each plate has a 60 cm diameter, and the distance between them is adjustable, offering flexibility for accommodating different types of equipment, making the platform highly versatile for various applications.”
Lift-off
The good news is that the floating platform works as expected.
“From the numerical results gathered during the experiments, we confirmed that the proposed floating platform used with Raspberry Pi is suitable for emulating on-orbit scenarios,” Barış reveals. “The floating platform of Zero-G Lab is successfully performing SIL (software-in-the-loop) and HIL (hardware-in-the-loop) capabilities. Several mission-specific proof-of-concept tests — such as rendezvous and docking, on-orbit interaction, landing, etc. — that leverage the floating platforms in the Zero-G Lab have been realised.”
Maybe a Raspberry Pi–powered robot will be tested on here for a future mission? Only time will tell.
Quick facts
- Parts of the design are patented
- The platforms communicate with the rest of the lab’s robotics
- Communication is handled via ROS
- Solenoid valves manage the pressure, to a max of 10 bar
- A pressure regulator helps control the external compressed air source
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