I tried to do something different this time: land a quad on a moving car.
After 2 unsuccessful attempts (crashes), the quadcopter finally did a smooth landing on the roof of the moving car.
The RC quad was controlled from the inside of the car using a 7" monitor (480x234 pixels) for FPV. Video was transmitted directly from the onboard GoPro2. A GoPro3 was mounted on the top of the car.
The quadcopter used a simple Multiwii controller board with acc + gyro. The PIDs weren´t tuned so the flight wasn´t very stable.
WARNING:this was recorded on a closed course without other vehicles or pedestrians.
Posted by Bernardo M. A. on September 19, 2013 at 5:30pm
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Hi, when i fly multirotors one of my main worries is to avoid it from crashing. Mechanically I've practically solved it because I usually fly an octocopter (motor, prop and ESC redundancy). My main concern right now is how to power the flight controller safely.
Initially I've connect all my 8 linear becs (in parallel) to my flight controller because I thought that if one fails, the rest would supply the required power. Later on I found out that a linear regulator may fail and may supply voltages higher than 5v and that would burn the flight controller.
A fuse is the easiest approach to solve this but I've read that sometimes it doesn't work well (fast enough). So i found the Crowbar Circuit.
So, i would use 2 linear BECs for redundancy and the crowbar circuit after each of the becs so in case it fails it will not burn the flight controller:
Another option:
I had the idea to use a switching BEC but i don't know if it's the best alternative. I've read that you cannot put 2 switching BECs in parallel because the voltage is generated in waves that may interference each other. So to solve this, one switching bec would be in use and if it fails, the backup switching BEC would take place.
The diagram for this is shown below:
If the SBEC number 1 fails, the Schottky diode would alternate to the SBEC number 2. I think that using 2 diodes would be better for the redundancy (i don't know if it's ok to do that). Could I use a relay instead of this diode?
What do you guys think? Will it work? Any idea is very welcome! ;D
Does anybody have the part list to do a crowbar circuit for the APM? I think it should supply 5v and 500mA, is that right?
Testing the octo without 1 of the top motors and then 1 of them bottom motors to check what's happens if a prop/motor/esc gets bad during flight.
Previously I've done the same test with a flat hexacopter and an Y6 but they didn't performed very well.
With a flat octocopter, if it looses 1 motor/esc/prop it's barely affected. I was flying my octo and it lost a blade of a prop but I just noticed after I landed.
2nd test with the gimbal: 2 axis, pitch and roll stabilized by a homemade mechanical gyroscope. Using a GoPro
In this second test, I added another joint so it can move freely in 2 axis as seen in the beginning of the vídeo. The performance was nice although i performed some very aggressive movements.
PS: i didn't use any bearing in joints, it's just a bolt, that's why the vídeo has some vibration. When I correct CG and replace bolts for bearings the performance will improve
Using a homemade mechanical gyroscope, i created a gimbal to stabilize my GoPro camera. In this first test, my gimbal has just one axis (pitch) so if i change the roll angle it will happen the gyro precession (it will not stabilize correctly). Precession is what happens when a spintop is desacelerating and doesn't stay in the vertical orientation anymore. In the beginning of the video I didn't pay attention to this, but later on, I could move forward and backwards, and the results were interesting! Check it out Next time i'll try with 2 axis to see what happens ;)
After an accident with the octo, i've got 2 motors shaft broken. Since there isn't a replacement shaft, i bought one of the following shaft and use it with the DT750. The steps for DT700, DT900 and DT1000 are similar:
I wanted to carry my GoPro (with housing) in a plane but without expending too much, so I built it by myself, using foam, depron and barbecue sticks.
The fuselage was done with EPS foam 12g/dm3 (isopor P0, comum de papelaria). Wings, ailerons, elevator and rudder with depron 4mm. I used some barbecue sticks to strengthen wings and tail. To assemble everything i used hot glue and packing tape.
Even though it had some crashes during this video, the plane is intact! Nothing happened to it. It's very resistant!
It is not flying very well because the wing angle of attack is 0 and the wing was not attached very well. I've already done these improvements but i still have not done a new flight.
Wingspan: 1200mm Lenght: 1000mm Chord: 250mm Wing area: 30dm2 Wing weight: 252g Fuselage thickness: 70mm Fuselage weight (with motor, ESC, RX and servos): 468g Battery weight: 200g GoPro (with housing): 200g Total weight: 1120g Wing loading: 37,3g/dm2 (should use a bigger wing to have a slower flight)
This is the 2nd flight I've done with my homemade plane for carrying a GoPro. I advanced the CG a little bit and now it's flying much better, very smooth!
I still need to balance motor and prop.
Beautiful dusk, filmed with the homemade plane.
Some flybys, landings, panoramics ...
Changed the 2200kv motor + 6x4 prop to a 750kv motor + triblade 9x4.5: a little bit slower but prompt response when I add throttle and much better efficiency, almost double flight time (10min).
I was getting lots of vibrations from my Hextronik DT750 even after balancing it and using balanced props. I replaced the bearings and now the motors are like new!
The steps for DT700 and DT850 are similar
To remove the C-Clip, it would be easier if you use a snap-ring plier (unfortunatelly i don't have one hhehehe)
A multirotor flight is very critical: if it happens an ESC, motor, propeller, RX failure or even if you get a lot of vibrations in the flight controller, the multirotor will crash. That's why I created a parachute and attached it to the quadcopter. This was the first test I've done with a parachute for quadcopter:
It had a stick so it kept the parachute away from the propellers. The problem is that the CG is difficult to keep in the center of the quadcopter and also because if the quadcopter hits the stick on the ground when it lands it's going to break the stick.
Therefore, I positioned the parachute on the back of the quadcopter without a stick. I've done a "wind tunnel" test (lol ;D) to check if the parachute would open:
As you can see, it seems to work, so I tried it in field:
Although it didn't land well, nothing was broken because the quadcopter arms are foldable and the ground was soft (grass).
The parachute is activated with a receiver channel and a servo. So when I get in trouble I press a button in my transmitter and it will release the parachute.
Currently i'm projecting a parachute launcher with springs, so it will be launch vertically and thus it will open faster. Another option would be using a small rocket/gunpowder to pull the parachute, but i'm still thinking on the positioning to avoid unwanted burn to the parachute and the multirotor
With a brushless motor and a TRex tail rotor mechanism I could assemble a simple variable pitch system. I measured and it generates 700g with the TRex 500 tail rotor blades.
I tried the Trex 250 blades from the main rotor but although they are longer the thrust is smaller, just 400g. This is probably because the motor doesn't have enough torque.
This could be used for a variable pitch quadcopter or with an airplane.
Specs: Motor: Hextronik DT750 ESC: Plush 25A Battery: Turnigy 2200mah 25C Tail rotor: HK-500GT Wood to support the tail mechanism: 38mm tall
I tested the Return to Home function of the Multiwii board using the default parameters. I didn't change the P, I or D of the gyros, acc, mag or any other sensor.
As you can see, the flight is not perfect since it's not tuned and it was windy but the tricopter returns to the inital position indeed. Usually RTH is activated when the signal from the TX is lost (multirotor out of control), it's a great funcionality.
Flight controller used: Crius AIO Pro GPS: CN-06 v2
Very stable vídeo with the octocopter, even without a gimbal! I've got a little bit of wobbles at some moments but this happened because the GoPro wasn't very well attached to the frame, I have some unbalanced motors and I'm using Hobbyking cheap propellers.
Can't wait to test it with good ones (APC, Graupner ....)
I've been using Multiwii but i wanted to test MegaPirate, so i uploaded the code and probably i'll never come back to Multiwii :D
Very stable flight with a homemade Octo with Crius AIO Pro. Testing Altitude Hold, Loiter (AltHold and Position Hold) and Return to Launch, great performance! I tuned the PIDs for Rate Roll, Rate Pitch and Stabilize Pitch, all other PIDs are default.
No software stabilization used in the vídeo.
I carried a GoPro and the video recorded by the octo was very stable! :)
If you have a Crius AIO Pro, I highly recommend MegaPirate!
