|
FAQs ( frequently asked questions )
How do UNAV units interface to RC equipment? PICOPILOT interfaces with most modern RC receivers and servos however some receivers ( Futaba's PCM series ) use 3v decoder logic and are not compatible with PICOPILOT. Installation of a buffer 605SB will allow PICOPILOT to work with 3v type receivers. Buffers are installed in-line between each cable to the RC receiver. PICOPILOT is powered from the RC receiver and requires 6v so the receiver must be powered from a 5 cell Rx pack. PICOPILOT uses an auxiliary channel on the RC receiver ( GEAR ) to control the ENABLE (switching from AP to MANUAL mode). The 3500 autopilot uses a 3v microprocessor so it's compatible with all RC receivers. GPS receivers are usually require 5v and can be powered from a 4 cell pack or a 5v BEC. PICOPILOT can be adapted to control Vtail planes by adding a Vmixer. Many RC Vmixers can't handle the un-synchronized RC pulses from PICOPILOT and will glitch, but the veetail works great with PICOPILOT.
How do you setup a datalink ? The 3500 autopilot system supports a full-duplex (bi-directional) RS232 serial link at 9600 baud. A "transparent" radio modem set with an RF data-rate of 9600 is recommended. The 9XStream, 100mW version has a published range of 7 miles. By connecting a radio modem to your onboard GPS output, you can add a data telemetry link to your PICOPILOT system to run a moving map on a laptop computer. The data downlink from a GPS receiver to a laptop computer running moving map programs is typically @ 4800 baud.
How can I see realtime position on a map? There are several good Moving-Map programs available that can display realtime GPS position over a digitized map. GARMIN's MAPSOURCE, FUGAWI and DeLORME all offer realtime GPS tracking. The new
PICO-GS uses JPG maps created by the operater. Google Earth and any other map service can be used for creating the JPGs. PICO-GS is an add-on software for PICOPILOT systems and can be used as a moving map and telemetry display as well as point-n-click waypoint display and creation. Data from the onboard GPS receiver can be shared by the autopilot and the on-board radio-modem using a simple 'Y' cable.
'Is there a low cost way of displaying GPS data on the ground? Yes, if you already have a TV transmitter onboard, the on-screen video display (OSD) is a good choice. The OSD is simply inserted between the TV camera and transmitter ( video cables). The OSD takes (onboard) GPS data and "prints it" over the video picture which is then transmitted to the ground station. The main advantage of this system is that it doesn't require any extra equipment at the ground station but the disadvantage is that it clutters up the video picture if you need to record a clear image.
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 ).
Can any of your flight controllers be used on a helicopter ? We don't recommend the PICOPILOT for helicopter applications because it's too slow. The 3500HL is specifically designed for helicopters and features an IMU (electronic gyro) and laser rangefinder. The rangefinder is capable of holding a hover within 2 ft and is immune to rotor turbulence that can cause interference for other autopilots (that use a BARO sensor).
Can I use GPS to navigate my RC boat ? Yes, the PICOPILOT-N works great on a boat. You'll need to limit your rudder authority for slow turns, about 20 deg/sec. The -N performs all waypoint navigation internally so any GPS receiver can be used. It will follow your waypoints in the order you entered them, up to 32.
Can I use GPS to navigate my Glider? Yes, we have several customers using PICOPILOT-RTL on gliders. The glider guys usually use it to keep their glider within visual range (return to launch), that way even if it gets caught in a killer thermal and climbs out of sight or accidentally flys into a cloud, the -RTL will always keep the plane under control and return it to the launch point. The -RTL works best on rudder-only planes but can also be used on planes with ailerons. Since the -RTL controls turn rate, no external wing leveler is required. Unlike the FMA "CO-PILOT" the -RTL wingleveler works in all weather and lighting conditions (even inside a cloud). Since the -N automatically stores the launch location every time it powers-up, no waypoint programming is required for a "return to launch" mission". The -RTL includes a GPS receiver and is powered from the RC receiver, which can be powered from the ESC-BEC(regulated 5v).
Which autopilot would you recommend? PICOPILOT was developed for electric motor-gliders ( no ailerons ) however it can be adapted to control slow, stable airframes ( with ailerons ). The 3500 autopilot offers many advanced features like an IMU (electronic gyro) which allows it to be used on a wide variety of airframes. The 3500 also features a groundstation and programmable enroute altitude and speed while PICOPILOT has no groundstation and uses a simple sample-and-hold airspeed and altitude control. PICOPILOT is recommended for stable airframes like a motor-glider or high-wing trainer with airspeeds under 50mph and weighing from 1 to 10 lbs. Because of it's slower response, PICOPILOT is not recommended for use on: Aerobatic airplanes, Flying Wings, Deltas, Jets or helicopters. The 3500, with it's more robust attitude control can handle faster, less stable airframes. Your choice of airframe will have a significant effect on the overall complexity of the flight control system and the resulting cost and weight. Product Matrix
Which version of PICOPILOT do I need? The navigation controller (NAV2A) includes a built in wingleveler and is designed for moderately stable airplanes. No external stabilization device is required The NAV2A works best on a rudder steered airplane (no ailerons). Rudder control provides the most precise control and is also the easiest to setup. The NAV2A can also be used on a plane with ailerons where we recommend connecting the RUD servo and AIL servo together (using a Y connector). The altitude controller (ALT3) is available with two different firmware options. The ALT3E (elevator) includes a pitch attitude control and is designed to control altitude with the elevator servo. The ALT3E works best on planes with moderate pitch stability and/or missions where the plane will be making turns frequently. The ALT3T controls altitude with the throttle and is better suited for planes with good pitch stability and/or missions where the plane will not be making turns frequently ( > 5 min). You can check your plane's suitability by testing it's response to throttle under manual control.
How do you enter waypoints into PICOPILOT? There are four ways to manage waypoints in PICOPILOT. 1) No programming or computer connection is required for PICOPILOT to perform a "return to launch" mission, it will automatically store the launch location as WP32 every time it's powered-up. 2) Using the WayPoint Editor, you can manually enter each waypoint data field ( longitude and latitude ) and the program will send the data to PICOPILOT ( via COM1 serial port ) which saves the data in onboard Flash memory. 3) Using the WayPoint Editor, you can 'Save' and 'Load' waypoint tables as files on your hard-drive. 4) The WayPoint Editor can import TXT files created in MAPSOURCE or KML files created in Google Earth.
Sometimes PICOPILOT glitches the servos on the ground? That's usually a symptom of RF energy getting into the circuit boards. RF interference can also cause sensor calibration errors (at power-up). A simple rule of thumb to prevent RF interference is; just keep your RC transmitter antenna collapsed (down) whenever it's within 20 feet of the plane.
PICOPILOT rocks my plane's wing ? For planes with ailerons, we recommend connecting the RUD servo and AIL servos together using a RC-Y connector. Having PICOPILOT control only the AIL servo will usually result in wing rocking. Your airframe's flight characteristics will have a significant effect on the autopilot's roll control, so you may need to reduce the (mechanical) aileron travel if you still get wing rocking. Roll oscillations are usually caused by either too much gain adjustment (NAV2) or by airframe Adverse Yaw. You can reduce Adverse Yaw by re-positioning the aileron servo arm(s) to maximize up aileron throw and minimize down aileron throw.
PICOPILOT pitches my plane up and down ? Pitch oscillations are usually caused by either too much gain adjustment (ALT3) or because the airframe does not have enough pitch stability. There are several things you can do to improve the pitch stability of your airframe; 1) reduce airspeed, 2) move the CG forward, 3) increase the tail length, 4) increase the horizontal tail area, 5) reduce the elevator travel.
PICOPILOT will only turn my plane in one direction? Slow (or no) turn in one direction is usually symptomatic of improper trim setting, especially noticeable at low gain settings (NAV2). To set the trim, fly the plane in MANUAL mode and carefully adjust the RC transmitter, AILERON trim so the wings stay level. PICOPILOT will use this position for neutral when it's ENABLED. It's also a good idea to take your thumb off the right transmitter stick when you enable PICOPILOT to prevent introducing an unwanted trim position.
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 programs use the COM1 ( RS232 ) port for serial communication. Most modern LapTops just have USB ports but you can easily create a COM port by installing a USB/Serial or PCMCIA ( PC-Card)/Serial adapter: Be sure to assign the port to COM1 using your WINDOWS Device Manager. Each of our application programs also allows you to configure the COM port it uses: QalTech SSP-100 PCMCIA/Serial Port.
Every time I try to run PICOPILOT or GPS-SIM, 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 >
I can't get the PICOPILOT program to talk to my autopilot ? It's probably because you have a "null-modem" serial cable (Tx/Rx pins reversed). If you do have the wrong type of cable, you can easily convert it to a "straight cable" by installing a NULL-MODEM adapter ( Radio Shack: 26-264 ).
My autopilot seems to get lost sometimes? That sounds like poor 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 it's self can determine how well it will maintain satellite lock. Generally, the more satellites a GPS receiver can track, the better it's sensitivity. For example, a 20 channel receiver typically has better sensitivity than a 12 channel receiver.
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 maximum endurance, the airframe needs to be aerodynamically clean (ie. no landing gear or struts). It doesn't require much speed or range since most on-board transmitters are limited to only a couple miles. It doesn't need to fly very high since most camera work is done under 1000ft AGL. For minimum cost and complexity, the airframe should be as small as possible, just big enough to carry the payload and have the performance required. Other important factors are, the airframe should be aerodynamically stable with simple, robust construction. Fast, maneuverable airframes and piston engines are undesirable for small UAVs. For PICOPILOT we recommend a simple (no ailerons), electric motor-glider that's just big enough to carry your payload and provide the performance you need. Probably the most popular RTF UAV airframe is the electric SeniorTelemaster which makes an excellent platform for the 3500. The New-Timer and the E-flite Ascent make excellent RTF airframes for PICOPILOT.
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 that use a barometric ( pressure ) sensor that have a resolution 4 ft. Altitude control also involves the autopilot and airframe response characteristics. The 3500FW typically maintains altitude +/-20 ft. of target.
My 3500 isn't working right ? Problems with the 3500 autopilot are usually caused by one of the following:
1) Insufficient vibration isolation ( especially piston engines )
2) Inadequate power supply for the RC receiver and autopilot ( do not use a regulator, use a separate 6v battery)
3) Improper or outdated calibration ( a calibration should be performed after a location or weather change )
4) Improper APsetup
|