H-bridge tutorial for motor control

http://www.pyroelectro.com/tutorials/h_bridge_4_transistor/

Tricopter Success!

I'll re-post my settings- I believe they've changed from the last setting summary I posted. Anyway, I'm very close to having the tricopter ready to fly some arial photography.

It is fairly close to stable flight. It still isn't as steady as I'd like, and I need to put in a lot of "up" elevator trim to keep it from putting the nose down and accelerating away, even with the CG set to the exact midpoint of the three rotors. One puzzeling obervation is that the craft seems exhibit the pitch problem less with the CG "behind" the centerpoint of the three prop booms. I'd expect the opposite to occur.

I've also had to do quite a bit of reading on RCgroups to try and understand the tricopter setup, in particular gyro gain setup. (and don't hesitate to correct me if my observations below are incorrect!)

First of all, there are several gyro adjustments available:

1) gyro max travel (screw adjustment)

2) gyro time delay (screw adjustment)
3) gain control (electronic adjustment through separate rx channel)

You adjust the gain by modifying the output of a channel of your RX. Basically, it uses the same PWM signal as servos and ESCs. If you send the gyro a 0% signal, that's max gain. A 100% signal is minimum gain. However, if you send the gyro a signal of 50% or more, it'll be in heading hold mode rather than rate mode. You want the tail servo on heading hold mode and the other three gyros on rate mode. Heading hold mode will try and move the aircraft back to the origional orientation, and rate will simply react to counteract an input acceleration.

Since the tricopter uses two "blocks" of gyros- one three gyro block for the rotors and one block for the tail, you need two RX outputs to control them. I attached the rotor gyro gains to the standard gain channel on the RX (thereby using the heli gyro menu item), then I used the throttle channel for the tail rotor gyro. All confusing as heck and not at all intuitive.

I'm thinking that the following changes will help with flyability:

• Changing from a 10x5 prop to a lower pitch- this should give the gyros more control as the ESC's will have a smaller output change in pitch inches per prop revolution per ESC step
• Adding a rear skid so the tail rotor yaw servo doesn't smack the ground on each hard landing
• Try moving the battery even farther back
• I'd also like to add more of a visual reference as to which end of the craft is the "front"

DIY Sunrise alarm clock

Nice implimentation of a do it yourself sunrise alarm clock. It's a little more from the ground build than I'd do, but it's nicely done.

http://sunrisealarm.sourceforge.net/

Yet another attempt

The gyro reversing and replacing the servo helped. However, it still doesn't behave quite right. I think there is still some changes to be done on the radio setup and perhaps gyro settings.



I tried several flights like this and each was the same. Time to figure out what was going on... I'm also going to do the "hot glue" modification to the gyros to see if that improves the flight performance.

Tricopter - 3rd & 4th flight attempt

Changes since last flight:

1. Reversed gyro on right arm
2. swapped gyro gain channels on receiver

These changes seemed to help. The tricopter would take off without immediately flipping over. However, it wasn't stable on the yaw axis, and would start spinning and translating sideways. I was able to lower it to the ground each time. However, the HXT900 servo I used for the tail rotor wasn't quite robust enough, and stripped out.

I'm going to replace the HXT900 with a parkzone DSV1300M- I believe this is a metal gear servo so it should be more robust.

TriCopter- 1st two flight attempts

No damage- but I think either the left or right rotor motor gyro is reversed.

Tri-Copter Final Pre-Flight- DX6i & AR6110 setup

NOTE- These were my origional settings, I've since updated the settings and they are posted HERE. These settings listed here may work but I highly recommend using my newer ones as they worked better for me.


The tricopter is finally ready for its maiden flight. I was origionally working from the setup guide on RCexplorer.se's website. His setup was for Futaba radio systems, and since I am using a Spektrum DX6i and a Spektrum AR6110 receiver my setup turned out to the slightly different. Bear in mind I haven't flow this setup yet, but it passes RCexplorer's recommended setup procedure. The gyro gain controls may not be 100% correct. We'll find out soon....

AR6110 Receiver Connections:
(note gyros are in-line with connections between receiver and ESC or servos)

Channel	Receiver Label	Servo / ESC
1	Throttle	Tail rotor ESC
2	Aileron	Left rotor ESC
3	Elevator	rotor gyro gain (split 3 ways)
4	Rudder	Tail rotor servo
5	Gear	Tail rotor gyro gain
6	Aux	Right rotor ESC

DX6i Initial Setup
(all based upon recommendations from various users on RCgroups)

Adjust List

Dual Rate & Expo

Function	Mix
Aileron	80%+40%
Elevator	60%+20%
Rudder	100%+inh

Swash Mix

Function	Mix
Aileron	+40%
Elevator	-40%
Pitch	+100%

Setup List

Reverse

Function	Reverse?
Throttle	N
Elevator	N
Gyro	N
Aileron	R
Rudder	R
Pitch	R

Swash Type
CCPM 120 degrees

 

Final Picture before 1st Flight

Also before the first flight I purchased a Du-Bro Tru-Spin prop balancer, #499. I initially hesitated paying the money for this tool, but after bringing it home it was obvious it was money well spent. It is a very nice tool, and made in the USA to boot. I'll be balancing all my props and spinners from now on. During some initial tests I was getting a lot of prop / motor vibration so I thought balancing the props would be necessary to keep the gyros happy. It was also vibrating badly enough so the nuts and bolts holding the motor beams in place were vibrating loose.