Archive for October, 2009

NordStar autopilot – UAV system

Lately I’ve been working on autopilot system for UAV (unmanned arial vehicle). Main goal is to have system which backs you up during FPV flight in case video broadcast or control link is down. I’ve finished component search, almost finished with schematics and soon going to route the board. Not sure how big it will be, but I’ve tried to use small components, no redundancy and keep simple as possible. All aerial control systems are very similar, they usually have battery monitor, GPS, accelerometers/gyroscopes and some additional sensors. This is something like that but I hope superior in few ways from the ones which are available in the market. Let the specs talk for theirselves:

- 6-22V (2-5 cells supported) power supply input range
- Step-up voltage converter making 12V voltage for FPV camera
- Making 5V for video transmitter (no BEC required).
- Monitoring up to 50 A with 0.1A resolution
- 6 channel control/capture
- Receiver fault detection
- Roll & pitch gyros
- 3 axis accelerometer
- Altimeter
- Air speed sensor
- OSD (on screen display)
- Telemetry data overlay on broadcast signal (TBD)
- GSM modem port
- 2 buttons for calibration purposes
- Bidirectional alternate communication port (dedicated for ultra long range communications)
- Temperature sensor
- I2C interface for external digital device
- New generation ARM Cortex-M3 microcontoller running up to 72 MHz (1.25 DMIPS / 1MHz)

Once I have more information, I will update. I’m giving schematics overview. These are not final and will be supplemented.

Electric motors: HXT 24g 3000kv

Quick peek at the specifications:
Shaft diameter: 3 mm
Pull: 450 g
Current: 30 A
RPM/V: 3000 KV
MAX RPM: 21000
Recommended LiPo cell count: 2
Weight: 24 g.

I was learning to fly with HXT 24 gram motor from the start. I can’t even remember how many crashes it has seen. I had to repair plane ten times, I’ve changed about 6 propellers. But motor withstood almost everything. After last crash I’ve inspected how motor is, and there are very some bad damages to the wiring. Few wires was broken. It still works, but in my opinion it won’t be very reliable because it won’t be able to take max current as it was designed to. Some users has complained about weak protection for the wires, it seems they are absolutely right. This is the weakest side of the motor. Nothing could kill it, including overvoltage, glues and unmatched propellers, but small cut at the wiring made it useless for critical flights as FPV.



Radio control upgrade to 8 ch 35 Mhz WFLY (WFT08)

I’ve decided to change my 2,4 GHz radio control gear to 35 Mhz. I’ve choose WFLY radio. It’s the most expensive radio from the cheapest class :) . It still has all main functions which belongs to programmable radio.


EU launches free satellite system to fine-tune GPS

The European Union launched a free satellite navigation network on Thursday that could help pilots, drivers and blind people by fine-tuning the accuracy of the U.S. global positioning system (GPS) to around 2 meters. The EGNOS system will use three satellites and 34 ground stations to narrow the horizontal accuracy of GPS from around 7 meters previously and improve its vertical accuracy to help pilots during landings. It paves the way for the better known Galileo project, a European satellite system which will rival GPS and could be up and running in 2014.

What it means for FPV developers? We mayby finaly have GPS guidance for landing and flight altitude control , which was almost impossible due to huger vertical measurement error of GPS.