Autonomous Trex 600 Project

I came across a nice, old unwanted Trex 600 flybar helicopter on craigslist and got it cheap. It had only been flown about 2-3 hours since new. The owner had gotten to where he could hover it nose out. On his first attempt at hovering nose left and right he had a mishap and crashed it. He gave up on helicopters at that point and shelved the heli for over 5 years. He recently advertised it on craigslist for $550. I ended up getting it for $400 and the damage was actually very light to it and cost less than $40 in parts to fix.

So I decided to build an autonomous heli out of it. I got 8300mAh of 6S power in it with the stock 5A battery under the canopy (along with a 1A 2S for servo power). And another 3300 Pulse 6S stuff inside the rear of the frame. On it's first hover time test I got 22 minutes to 85% discharged running 1,850 rpm headspeed, and was pretty happy with that.

So I put a Pixhawk in it with ArduPilot/ArduCopter 3.4.6. A Neo 6M GPS/compass module, 915Mhz telemetry radio for the ground station link. Got the Pixhawk tuned to fly a flybar heli in full autonomous mode, and it works VERY well. It completed its first successful "mission" yesterday, flying a 4.7 mile GPS waypoint course at 65 feet altitude and 18 mph ground speed. I did not use autonomous takeoff and landing for the first test - that was done flying the helicopter manually. But it is capable of fully automatic takeoff and landing with the Pixhawk in it


I'm going to add a GoPro and FPV camera and transmitter to it yet, as soon as I design a suitable mount for the GoPro.

Fully autonomous flight with multi-rotor drones is fairly common. But not many people have done it with a helicopter. It's kind of neat watching the heli fly itself with absolute precision and getting the telemetry readout on the ground station (an Android 12" tablet with Tower in it connected to a MavLink radio), with aircraft attitude, ground speed, altitude, and GPS position shown in Google Maps as it flies.

In flight it would probably fly longer than 22 minutes. It draws 22 amps at hover, but once it goes into ETL in forward flight over about 12-15 mph, the amps goes down about 16-17 amps. The helicopter was so stable in 12-15 mph wind during the flight yesterday that it won't require a gimble on the GoPro to get really nice flight video.

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Very cool. I remember dreaming of such things.

It's funny because I'm in the market for a heli. I wanted FBL and forgot about all of the APM and Pixhawk stuff I have. Thanks for the reminder!
 
It works really good. Lots of autonomous stuff these days with multi-rotors, not to common to see a helicopter set up that way, especially a bigger one like this.

 

JimCR120

Got Lobstah?
Site Moderator
Yeah that was plenty cool. Autonomous flight is impressive but I have to admit, I was ooohing and aaahing just hearing the main rotor come up to speed.
 
That old Trex 600 has straight-cut 17:1 gears in it with a 600L motor. It's a screamer and it has a lot of power. The heli weighs about 9 lbs with all the extra stuff on it, and it can lift its own weight in payload pretty easy. Been having a lot of fun with it. My grandson, who's only 6, said he got his little RC truck stuck in the mud. And he wanted me to use the helicopter to air lift it out of the mud. So we rigged up a 15' piece of clothesline rope on it and I air lifted his truck out of the mud for him. I don't know if I had more fun, or if he did, but we both had fun playing with our toys :D
 

PsyBorg

Wake up! Time to fly!
Yeah that is amazing. Nice job on the set up and conversion. It still Scares me when I read Autonomous in reference to hobby grade flight. Most people do not have the experience nor the wisdom to do things like this properly as you did. They slap it all together and toss it in the air then learn as they go. Most cases end up poorly which gives the hobby a bad name and adds to the "Oh NOOOOS its a drone" mentality.

Thank you for being responsible and meticulous in what you have accomplished. Things like this can put the hobby in a good light. Keep us up to speed with the progress and what you are able to do with that set up.
 
What makes it autonomous is a GPS and gyro assisted autopilot. Full size aircraft have the same thing. The difference is that with a full size aircraft it still requires a pilot at the controls to take over if something goes wrong, but the pilot is in the aircraft. With RC, the data and parameters are fed to a ground station with a dedicated telemetry downlink. But the pilot still has to be at the controls (radio) to take over if something goes wrong. No autopilot is fool proof.

It's a considerable undertaking to get an autopilot to fly a RC helicopter. And that was one of the enjoyable challenges of doing it.

Here's another short video taken by a GoPro on a solid mount (no gimbal or damping) on the right landing gear leg. With the helicopter flying an autonomous weave pattern. It's not perfect and jello-free, but the helicopter is incredibly stable compared to multi-rotor drones, considering this is from a solid mounted camera bolted to a piece of aluminum flat stock on the gear leg.

 
Continued tests with the Trex 600 platform, testing autopilot accel limits and flying slow with the headspeed at 1,950 rpm to test flight time and autopilot accuracy for survey flights. The helicopter was not quite into ETL on this one and was drawing very close to hover amps the whole time. The flight lasted 16 minutes takeoff to landing. The batteries, after cool-down and recovery came in at 3.79 volts/cell (6S).

The helicopter is going to get another 5,000 mAh 6S battery put on as a "belly fuel tank" to get the safe flight time over 20 minutes in slow speed flight. And should get at least 25 minutes with the speed ramped up so the main rotor goes into translational lift. This course was only a half mile loop flown 7 times. So 14-15 mph was a good test speed to prevent the helicopter from slowing too much in the turns and having to accelerate back to target speed on the simulated survey passes. On a true survey flight, surveying a 1/4 section, it would be flying at 45 mph on the passes. Set the autopilot accels so it doesn't slow in the corners and instead leans into the power and collective, banking over on her blade tips to come out of the turn on the next pass right on the 45 mph target speed.

 

PsyBorg

Wake up! Time to fly!
That is coming along nicely. It amazes me that thing fly's so smooth with no one touching the sticks. I do have one suggestion for your next video though. Cut the volume on what ever you are playing the motor sounds with by at least 80% as that was brutal to listen to and try to hear you talking. I couldn't get past the 3 minute mark with that to try and hear what you might have been saying after that.
 
It's coming in over the FPV feed on the monitor. I usually leave the volume at a level that I can tell if something goes wrong on the helicopter. Usually failures in RC heli's are either drivetrain or blade related. If something goes wrong I want to know about it, shut it down and autorotate it before it crashes because the autopilot will only go to full collective and stall the rotor if the drivetrain or power is lost in flight.

At the ground station it's not loud at all when standing there. For some reason, filming with my cell phone, the phone seems to like that noise from the FPV monitor more than anything else. Didn't even know it until I watched the clips later.
 
Just because the heli has autonomous flight capability doesn't mean you can't do some manual flying and have some fun. My grandson has been having a lot of problems with his plastic trucks lately. He's become a regular customer of Grandpa's Helicopter Service :)

 
The latest improvement was to bend up a new aluminum landing gear that's taller and wider. And mount the GoPro underneath with a belly mount instead of the side mount off the gear. This puts the camera closer to the CG of the aircraft and makes for smoother video. The camera is solid-mounted, no gimbal.

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https://goo.gl/photos/uPchUxEY3QGHUtvt9

I prefer to have the blades locked down tight instead of letting them articulate on this heli. Much smoother with zero vibration when banking into turns with the blades locked tight. With the blades fore and aft it is 6 feet long from the tip of the front main rotor blade to the tail. And with the bigger gear on it it just fits under the tonneau cover by about an inch, and fits lenghwise with 6" to spare in the bed of a shortbed pickup. This helicopter has 675 main rotor blades on it, so it's only 50mm short of a 700.

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https://goo.gl/photos/Xgr2F3bvNRfyRsMs6
 
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