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Jul 28, 2008, 04:07 AM
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Pulverised by pulses


So after 4 days, got the PWM moved over to interrupts & it worked as designed. Jitter from the software is gone. Everything is running faster, from radio to IMU. Radio is going about as fast as possible, 5500 bits/sec because of the packet flushing delays. 2 way communication may be practical again.

Interrupt driven PWM on a PIC is a waste of time & really hard, 2 B sure. It's the largest routine of them all.

Note, U need to create an interrupt table from the servo PWM & read off the table in the interrupt handler. There's not enough time to recalculate each delay from scratch.

Be sure to use RETFIE FAST when returning from interrupts, otherwise you'll get stable results on the bench but crash in flight. Also, a permanent lockout occurs if the PWM goes out of range, so U need to clamp that.

Found a bug in log cyclic damping but it still was too unstable.

Min throttle had to be stepped higher yet again. The jitter must have been pushing it into the minimum range. Chinese ESC's keep going if PWM is below minimum or signal is lost, making for exciting tests.

Running throttle at 0.6 is sucking huge amounts of flight time. It's at least 2 minutes lower than it was at 0.55.

Now the bad news. Flybarless doesn't work anymore & the tail is wagging again. With the best gain & bandwidth she's real loose. Any wind or descent with power & she's out of control, killing engine, autorotating & crashing with pride. Jitter actually dampened the angular rates.

Now some options:

Put the flybar on.

Add noise to the interrupt PWM generator.

Revert to polling PWM like nothing ever happened & lose radio speed.

As sweet as Henrik Copter is, he still uses a flybar.

Have some extreme motion tracking from a past flight.

moff closeup (0 min 31 sec)
Last edited by Jack Crossfire; Jul 28, 2008 at 05:15 AM.
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