How do UNAV units interface to RC equipment? 35xx series autopilots are compatible with most RC-Rx's (5v & 3v). All UNAV autopilots are powered through the RC-Rx connectors so the RC-Rx must be powered by 6v ( 5cell NiHh). All UNAV autopilots use an auxiliary channel ( GEAR ) from the RC-Rx to ENABLE the autopilot ( AP or RC ). The 3500 autopilot uses a RS232 GPS receiver that's powered by an external 5v power supply. The 3520 includes a pre-wired 3v, TTL GPS receiver which is powered by the autopilot's 3v regulator.
How do you setup a datalink ? The 3500 autopilot system supports a full-duplex RS232 serial link ( 9600 baud ). Any "transparent" radio modem set with a throughput of 9600 baud can be used. The 3500 includes a XBeeXSC set with a max range of 6 miles. The 3520 includes a XBeePro set with a max range of 1 mile. Range can be increased by upgrading to a high power radio modem like the XTend series ( 15 miles with omni antennas ).
How long does it usually take to get a UAV fully functional? Our autopilot systems include a GPS receiver, sensors and software. To complete your UAV system, you'll also need an R/C system for manual control and a laptop computer to run the software. Selecting components for a UAV system, installing everything and getting them all to work together is commonly referred to as "System Integration". This phase of your project can represent a significant portion of the cost and time required to put together a successful UAV system. Documented procedures for testing and qualifying each component in the UAV system as well as system test procedures and checklists all contribute to an organized, step by step integration process. The system integrator should have a basic understanding of electronics, computer software, RF equipment, engines, aerodynamics and payload components ( TV equipment ).
Why don't you offer autopilots with automatic take-off and landing? ATO&L (automatic take-off and landing) may be an interesting challenge in UAV contests and fun to experiment with but it's not a very practical feature in real-world applications. Our products are optimized for real-world applications where cost, performance and reliability are the major issues. Most ATO&L systems simply add an ultra-sonic range finder to the autopilot to detect the flare altitude for an automatic landing. Automatic take-off is not really a special function at all since most autopilots will seek the assigned altitude and head towards the selected waypoint, whether in the air or starting on the ground. The main problem with ATO&L is that it requires a large field or paved parking lot to perform. Since GPS navigation error is +/- 50 ft, it's simply not accurate enough to land the plane on a road or landing strip. There's more to ATO&L than just navigating to the runway. ATO&L requires lining up with the runway and establishing a glide-slope to the threshold. Another problem is that ATO&L systems usually have no provision for obstacle avoidance, a common challenge for any human pilot during a landing. Why expose your plane to unnecessary risk with an ATO&L system which offers very little margin for error. If you think you really need an automatic landing system, a much simpler solution would be to just use an onboard parachute or perhaps the old-fashioned "pop-up horizontal stabilizer".
My computer doesn't have a DB9 serial port ? All of our WINDOWs applications (GCS software) use a COM (serial) port for communication between the LapTop and the autopilot. Most modern LapTops just have USB ports so the 35xx series autopilots include a radio modem with a USB interface. Just make sure that the COM number matches your computer's COM port # and the COM # used by the UNAV software. All of our WINDOWS programs allow you to configure the COM #. Your computer's COM # can be changed with WINDOWs' Device Manager.
When I try to run the GCS software I get a bunch of error messages about HRCHECK and WriteByteBuffer ? That message means that WINDOWS can't find the COM (RS232) port on your computer. < see preceeding paragraph >
My autopilot just circles sometimes? That sounds like poor GPS reception, the autpilot is designed to circle if it loses GPS reception. There are several things that can affect GPS reception. 1) Mounting: Make sure your GPS is mounted antenna facing up, on top of the fuselage, with a clear view of the sky. 2) Obstruction: Make sure that there isn't anything on top of the GPS, especially any conductive material, thin plastic is OK. 3) Power: Make sure that the GPS has a good stable power supply. 4) Weather: Clouds and rain will reduce GPS reception. 5) Vibration: can reduce GPS reception, provide vibration isolation for your GPS if your plane is powered by a piston engine. 6) Terrain: Mountains, buildings and other objects can reduce GPS reception. 7) Bank Angle: can reduce reception, limit your bank angle to 30 degrees. 8) Receiver: the performance of your GPS receiver will determine how well it maintains satellite lock.
What type of airframe do you recommend for a UAV? Most small UAVs are used for aerial observation. So, the airframe needs to be capable of carrying a small camera and perhaps a TV transmitter. For good pictures, the airframe needs to be stable, with low vibration levels. For most missions, you don't need high speed or long range since most on-board transmitters are limited to a few miles. You won't need high altitude capability since most camera work is done under 1000ft AGL. To keep the system cost low, the airframe should be as small as possible, just big enough to carry the payload and have the endurance needed for the mission. The airframe should be aerodynamically stable with a simple, robust construction. Fast, maneuverable airframes and piston engines are undesirable for small UAVs. Probably the most popular RTF airframe is the SeniorTelemaster because it can carry several pounds of payload and is easily controlled by our 3500 autopilot.
How accurate are these autopilots? Positional accuracy is affected by three general factors. ( 1 ) GPS is the primary means of navigation for UNAV autopilots. Civilian GPS accuracy ( CEP ) is specified by most modern receivers at: 5-25 meters ( 16ft - 82ft ) where the accuracy depends on GPS reception factors such as weather and terrain conditions, and satellite availability. ( 2 ) Programming accuracy is a function of the decimal place precision that the autopilot stores waypoint data. All UNAV autopilots use 4 decimal place precision where .0001 deg = 36 ft (at the equator) but that translates to a 18ft positional accuracy. ( 3 ) Navigation errors also effect position accuracy. All UNAV autopilots use GPS ground track for navigation so they don't need to compensate for cross-wind. Under ideal conditions, with a clear sky, calm winds and no large builds or mountains near by, the best positional accuracy you can expect would be +/-33 ft. Under poor conditions, with a thick cloud cover, gusty winds and mountains near by, you can expect positional accuracy in excess of +/-100 ft.
UNAV autopilots use a barometric ( pressure ) sensor with an altitude resolution of +/-4 ft. Altitude control also involves other factors, such as the airframe response characteristics. The 3500 autopilot typically maintains altitude (in level flight), within +/-20 ft. of the programmed altitude.
What are common problems with setting up an autopilot ?
1) Insufficient vibration isolation ( piston engines )
2) Inadequate power supply for the RC receiver and autopilot.
3) Improper or outdated calibration
4) Improper APsetup values
How do UNAV autopilots compare with other UAV autopilots ?
UAV autopilot survey
Could your equipment be used by terrorists ?
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