Newbe Needs Guidance

[Daystate]

My goal is to be able to fly FPV from one of my air vehicles. If I were to lose signal, or the aircraft were to go out of range, or the video would stop broadcasting, then either I, or the failsafe, would trigger an enable to an on-board auto pilot, which would bring the aircraft back to me and then circle until I disabled the autopilot, and took control.

I have been looking at the U-NAV web site and I am unsure of what to purchase. You see, I have two aircraft that I would like to try and utilize the same autopilot in. My question is, if I were to purchase an autopilot for a Kadet Senior, could I also use the same unit in a powered parachute. I realize the altitude hold would be different.

I would like to fully test the autopilot in either airframe. Can someone explain (in laymen’s terms) the scenario involved in setting up a Pico pilot to achieve the desired goal? I am not even sure if I need a Pico pilot. Maybe, you guys know of some other system that I am not aware of.

Your help would be greatly appreciated.

[kd7ost]

Daystate,

Welcome to the UAV area. I have a setup that allows me to do exactly what you're looking for. I use it for the same thing you describe. I'll tell you what I've learned and what equipment I use.

In the simplest form that I am aware of, and featuring as much off the shelf technology as possible I suggest the following.

Putting a small handheld GPS on board your plane. The GPS needs to have a serial output port and the ability to output NMEA 0183 data. (It's hard to find a GPS that won't do that) In this example though it needs to be a handheld unit. Not an OEM. You have to let the GPS get lock where you are flying from and then put your location in as a waypoint. Then you simply tell the GPS to "goto" that way point. Serial information coming from the GPS port will be outputting information like heading, range etc.

The output port needs to be connected to a device like an AP4 or a PDC-10. These are no longer manufactured but can be found on e-bay and the like. Sometimes folks sell that gear here. Units like those use PIC chips with some ones proprietary software to decode the heading information from the GPS. It converts that information into servo pulses that are used to steer your plane to the waypoint. The devices have enable lines so can be run in a transparent mode. Both are designed primarily to connect up to a rudder servo to induce Yaw for the steering function. You connect your receiver rudder output to the rudder input. Then connect the rudder servo to the output wire. A spare (enable) servo port comes in too. Like flaps, gear whatever. As long as the unit is disabled you fly without even detecting it in place. But enable it with the spare either by Pilot control of failsafe function and the unit starts steering your plane based on the GPS information. Thats why you have to use a handheld rather than OEM gps unit for this typr of application. They don't have a way to store or manage waypoints. The GPS needs to do that for you.

Obviously that only manages steering back to you. If you have a plane set up with built in stability there isn't much more. But you have to manage roll and altitude too. A plane with a good dihedral or polyhedral will be fine. Planes with ailerons will need a roll control device. The most secure method at an entry level for this is the FMA co-pilot. In fact this might manage your roll and pitch well enough to get you back safely without an altitude lock. Here's what to consider there. How high are you flying and how far away are you going to be with a plane that isn't pitch sensitive. You have the Kadet senior and that's a good platform for this. Make sure your balance point is not tail heavy at all, and not very nose heavy. You want to try to stay pretty neutral. The servos and controls don't have to work too hard overcoming things you as a pilot normally handle. Give the components an easy job if that makes sense. Set the plane up carefully and well.

If you're up high and not very far, the co-pilot will manage roll and pitch. A co-pilot won't keep you at altitude though. Your plane will change altitudes in normal air. Lift, (Thermals) sink, wind ballooning etc. It will keep pitch flat but not altitude. In a vacuum, no problem. But the more you have a radical plane set up, fly low and far, in high winds or whatever, the more you want to consider something that will keep you at a set altitude so in the event of an emergency return you don’t have to worry about flying gracefully into terra firma.

This should answer a few questions and generate a lot more. Fire away.

Dan

[Daystate]

First of all, Thank You very much for you help!! :D I have to say that I am very impressed with this site. There is such a wealth of information but I think I seem to be keeping up so far. ;)

I hate to say that my time is precious (as is everyone else’s) and I just happen to love electronics, BUT, I have just the basic knowledge of it at this stage of the game. :(

Most likely, I will have to look for a somewhat-complete system initially. Would a system like the UNAV PP work for me?? :confused: What would actually be the cost difference (savings?) of a “component system” rather than a full system? Of course you might have to add labor in there as well.

Could I use their altitude module? Or, do you know of any other systems?

[kd7ost]

Actually the U-nav Pico Pilot system was designed with small electrics in mind although it translates easily to larger aircraft as well. They have a variety of options that would suit your needs. I would e-mail them for advice on the best way to proceed. There are two versions of the Nav system. One designed to work with an aileron ship and one for rudder steering. There are also two flavors of altitude lock. One works with the elevator and one works with the throttle. They have a tiny GPS and you don't need to put in a handheld unit then. The Nav board manages the waypoints.

Dan

[copperclad]

hi Dan
i have just become interested in UAV and wanted to say your above post is great for spelling out what is needed for a baseline , off the shelf , system :)
i have just purchased a garmin etrex and have been useing a micro controller to read out the heading info through the rs-232 port , i have built and fly coaxial platforms and planes and helis , but i thought for my first platform i would go with a groundbased vehicle , and progress to a coaxial platform from there , i am just starting on a 30 sized ( 550 main blades ) CP coaxial and plan to use it as a test bed , i will post pictures as the build progresses , just wanted to say thanks for the help , great forum , dana

i posted a few pictures of a small coaxial i built and have been flying , the pictures were taken the day i finished the machanics and show it a few days before its first flights

[kd7ost]

dana,

Wow, that is excellent work. I do have to say when it comes to hovering platforms I'm amazed but in the dark as to how to make them fly autonomously. I think it has a different range of issues requiring an uncommon skill set to resolve. My hats off to you. You should start a thread here on this project to see what else you pull in from the other rotor craft guys out there.

Keep us posted cause this is cool.

Dan

[copperclad]

hi Dan thanks :)
i have been reading everything i can find on the different UAV threads and forums and find there is a lot of good information out there , i have experiance programming a few different micro controllers and thought this would be a great new area of the hobby to get into , i have a plain vanilla RC car with a 3 channel system and thought i would set it up so i could drive a coarse and use the third channel to set waypoints as i went , and then send the car around again where the tx would just be used to disable the car if it gets into trouble , this seems like a good way to get my feet wet on GPS control before i try it in an airframe , as far as i have gotten thinking about UAV flight in a coaxial would be to use a FMA co-pilot and a micro controller to follow a coarse , and use a TX like it would be used in a flight training setup where if the machine gets into trouble i could take control back from the micro controller , i have ordered all the parts and materials i need to complete my 30 size machine and am just waiting for bearings to arrive so i can start work , i will take pictures as i go and start posting them as i complete different parts of the build , i enjoy the forums as a great place to share and exchange information , thanks again , dana