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Unprecedented Motion Control in Satellite Communications, Connecting Equatorial Countries to the Information Age

“InMechaSol has delivered the first of its kind autonomous distributed control system and opened the door for further mechatronics innovation.”—Gary Eades, InMechaSol

The Situation

The founding mission for the company O3B Networks was digital parity—to bring the “other 3 billion” people who live in a band around the equator into the Digital Information Age. At 45 degrees above and below the equator, in areas of the Middle East and Africa, areas with much less telecommunications infrastructure, access to the Internet using terrestrial methods is challenging, geostationary satellites offer an alternative only, the service is slow. Through a never-before-tried constellation of satellites orbiting the earth in Medium Earth Orbit, a closer range (just 8,062km above earth) than geostationary satellites, O3b set out to address the communications challenge.

O3b partnered with AvL Technologies to make transportable antennas that would communicate with their satellites. Because of the complexity of the control systems required, AvL partnered with InMechaSol for their expertise in precision mechatronic systems.

InMechaSol engineers set out to address another kind of communications challenge: to create a software control system to enable the antennas on the ground to move as needed to reliably communicate with a moving satellite system. The antennas had to be precise in pointing because precision means bandwidth. The overall software solution needed to manage a sizeable number of information inputs, as well as outputs—controlling motion of the antennas in real-time.

The Summary

)3B transportable anteneaBecause they’re closer to the earth, O3b Medium Earth Orbit satellites are in constant motion. They’re not geostationary and fixed above the earth, like most other satellites in use today; but constantly revolving in and out of visibility. To enable a constant link more than one antenna is required to hand-off from the last satellite to the next visible satellite.  Timing and precision motion, these make for a complex motion control problem.  The closer the antenna track to the peak of the beam, the more it can in turn communicate.

 “We had worked with InMechaSol on previous antenna projects and always been impressed,” said Ken Westall of AvL, who project managed the collaboration. “They came on board with some knowledge of our programming and presented us with an elegant solution to a very difficult problem that fit within our tight budgetary and technical constraints.”

The design path for the software control system involved three components: the motion control solution, the antenna control solution, and the station control solution. Enabling communication between these pieces of hardware was a complex task accomplished with an understanding of natural sciences, like geophysics, together with complex computer programming skills. The software solution harmonized diverse application programming and included unique arbitration logic—functionality that allowed for automatic redundancy to ensure information accuracy.

Jim Dale, of AvL Technologies, spoke about the collaboration:” “The O3b system was a challenge that required two antennas working together in a coordinated way, handing off tracking responsibilities. Only one antenna was active at once, while the other was repositioning itself to establish a link so that there was no break in the communications. The antennas on the ground are there tracking multiple satellites. One is typically rising while one is setting. InMechaSol helped us architect that system and then helped us to implement it with software they wrote.”

The Solution

InMechaSol’s program engineers Gary Eades, Matthew von Arx, and Robert Leidy began by analyzing the functionality of the existing communication framework. To build from the original software, programmers wrote a separate piece of software to learn the language of the Application Programming Interface (API) that controlled the remote tracking antenna hardware. The existence of many component devices for the remote antenna structures (such as a signal source utility and a modem) using different APIs, multiplied the difficulty.

The component pieces would ultimately communicate using a new, shareable API. A system of advanced algorithms was also essential. For each computer involved, there was a fixed capability for processing and information gathering. Because the antennas, satellite and user interface would be operating in real-time, CPU usage translated directly into high or poor performance. This was the optimization challenge. To overcome it, engineers made domain-specific calculations for signal inputs: They wrote equations to optimize processing speed. In the end, API restrictions were solved with advanced algorithm logic.

Engineers also ran the new software on existing hardware: “Each antenna on the ground has a computer inside, which normally controls only motors,” said engineer Robert Leidy. “However, there was operating space on these computers to run software that added redundancy. One antenna assumes a master control role and the other a slave role—roles dynamically assigned based on the availability of devices on the network. If one antenna becomes inoperable, the other picks up all station managing responsibility without losing a step.”

The motion control solution allowed for improved tracking performance. The antenna control solution was based on tracking signal management and handled with a range of angle calculations—algorithms designed for moving targets. The station control solution was the most complex aspect and required “a new application,” said engineer Matthew von Arx, “with a reliable execution system managing specific device communications and scheduling actions.”

The Results

The high throughput of the O3b network—the speed and volume of information traveling between earth-bound tracking antennas and moving satellites—allows people to join the Internet Age and its global marketplace in places where fiber is impractical or unreliable. Landlocked countries without fiber-connected infrastructure like the Republic of South Sudan, or island countries like Madagascar, which depend on submarine fiber for broadband service, are African areas with clients already using the MEO satellite constellation for connectivity.

Not only are these places now connected, the satellite network is fast so they have the benefit of speed. The network doesn’t just compete with the speed of fiber—supporting video and cloud computing—it surpasses. Because it’s closer to the earth, the network offers ultra-low latency. The time delay for information to travel from earth to satellite and back is less than 150 milliseconds, compared to geostationary satellite delay of 500 milliseconds. The satellites can also point a spotbeam at a geographical target and dedicate bandwidth to a user.

The 2.4m Tactical Transportable Antenna was unveiled in March 2016. At the time of this writing, the O3b network was serving 40 clients in 31 countries and already the fastest growing satellite company in history.

Jim Dale, who has worked with InMechaSol on two projects said of the partnership: “We see InMechaSol as having a great deal of expertise in motion control. If we were to get a project where there was significant motion control design and architecture expertise needed, we would look to InMechaSol again.”

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