Blogs

A flexible mission control kit

Thanks to the abundant comments from our friends and the ever growing requirements of our clients, we've been double busy working on some new GCS models for small series and batch production. One of the new models – or rather new versions – is this little kit, which caters for a long list of customer demands collected during the earlier production cycles and in this design phase. The primary goal of this exercise was to create a new station framework that has all the following basic features without unacceptable trade-offs:

• Man portable system with an absolute total maximum package weight of 12kg
• Full ground control functions with complete direct RC, live AV and modem telemetry
• Removable Android based fast and user friendly IT hardware
• Both wearable "belly box" and seated desk mounted operation
• External RF box option for pole, tripod, tracker or vehicle mount
• Belly box no more than 2.5kg, individual transport cases no more than 6kg
• Easily adaptable control systems for the most popular FCs, primarily APM/Pixhawk/PX4, but also DJI, MicroPilot, etc.
• Fully customisable controls with dual joysticks, trims, 6+3+3 modular switch and pot locations
• Single operator basic scenario with the option for additional operators with linked control trays
• Extremely fast field set-up and disassembly
• Self contained packages, all antennas, cables and other accessories must fit within the transport cases
• Self contained field charger option
• Flexible RF link set-up, 1-3 band operation including COFDM or MIMO links
• Scalable levels of water and ingress protection, from simple dust proof to full IP (54-67)

Our previous fold-up type station had a PC tablet installed, which performed pretty well, but we weren't too happy about the Windows GUI or in fact with Mission Planner in this small 8" format. The Android based GCS software packages have come a long way since then, so the time has come to update this wearable belly box framework with a much lighter and friendlier Android tablet.

Because the Bluetooth telemetry link has also become a de facto standard, there was no need to mount the tablet permanently in its frame for a constant USB connection any more. Neither was it important to charge the tablet from the control tray, especially if we were to use a tablet with one of the longest battery endurances available. Besides, some of our customers noted the need for being able to remove the tablet during waypoint programming, settings tuning and other purposes. However, they still wanted the tablet to be an organic part of the station with its own hood and well secured in place, rather than the flimsy clip-on phone or tablet mounts of other systems. Hence the current slide-in "letterbox" frame, which holds the tablet firmly even when you are just hanging the station all the way down from its handle.

As this is a fairly long range kit, we used an external RF box to be able to separate the operator from the best antenna location, but for short ranges we can fit all the RF modules in the control tray itself. In that particular case the entire station fits into a single transport enclosure. The downside is that we still need to link the fold-up telemetry frame with the base for the antenna leads, but it's still workable through an energy chain.

The ideal RF link combination with built-in RF modules is just a TBS Crossfire and any old 5.8GHz AV. As the Crossfire will satisfy both direct RC and telemetry modem functions, we can get away with only two antennas on top of the tablet frame in the corners.

You'll notice the single system cable that links the RF box to the control tray, which is an engineering treat in itself. While it is pretty simple to link these two units when the single RF link is an IP based fully digital high-end system, we do quite a lot of signal conditioning for mixed signal versions at both ends of the cable to eliminate crosstalk. While this unit only needed 5 meters of autonomy from the RF box, we can easily go over 100m of cable without issues using the same technology.

The noble wood frame is not a flashy detail here, because we have tried and tested at least a dozen different materials for this very purpose. While we have quite the tooling and experience in composite and aluminium CNC end milling, this type of structure was a bit out of our comfort zone. We weren't too happy with the 3D printed versions, with neither their finish, nor their rigidity, and we certainly didn't want to put a boat anchor around anyone's neck by using aluminium as the body of a wearable tray. Our series production batch sizes don't warrant injection moulded parts in this format, either, so my favourite material remained the only option.

As a personal note, I was a cabinet maker/joiner apprentice before I went to college and later uni, so wood is very close to my heart as a material for anything. As with most other wooden objects or pieces of furniture I've ever made, the surface of the frame is not varnished or lacquered, but treated half a dozen times with tung oil and hard wax. We've found these frames to be lighter and stronger than ABS when made of okoumé, but walnut will be even better.

P.S.

Some readers of these log entries noted earlier that I only show rather expensive and high-end builds which are unattainable to the average DIYdroner. We started our journey at very much the same level as everybody else, with maybe even less funds living on the other side of the old iron curtain, but we've built a strong team over the years. We still don't shape our gear to fashionable forms as any self-respecting industrial designer would do. We just put the technical substance in ergonomic and practical packages while keeping basic proportions and rules of symmetry, that's all.  

While this kit is still not so much of a consumer grade piece, we are slowly moving towards numbers and new methods of production, so this wouldn't be the case for very long. Next time I'll also be discussing some very simple and practical builds that everyone can replicate or develop, but they still make a big difference in UAV operations.