Andy knows the system so well already and has described it really well. Thanks Andy, I'm almsot ready and packed for Bulgaria but still trying to finish some timers to take with me. The differential gain works a lot like Igor's first active regulation where he used a current detector that adds a higher throttle reference to the Jeti Spin esc's governor. My system detects a drop in rpm but adds gain to the governor feedback loop. It does not add a higher reference rpm, just governor gain and only accelleration not decelleration. The only way to get close to the old 2/4 break that can actually slow down the rpm on the downhills, is to use position sensors like accellerometers and gyros. All systems including and especially engine systems have their own funnies that make them less than ideal in turbulence so they are all a trade-off. Holding the rpm absolutely fixed is a good way to fly but then the model slows down in the hard corners. Having a fixed airspeed is not easy to achieve.......ask Igor! It's also very hard to define exactly what we want in fact, but a good constant rpm with a little extra kick when you need it is a good compromise, and does not cost much either.
Keith R
Exactly, may be I should write about that my old solution which I had in Landres WCh 2008 ... I had a current sensor which can "see" power input to prop. It is enough to measure current, because voltage is almost constant. On base on current I did simply positive feedback to prop.
The theory behind is, that if the prop keeps constant rpm, then any extra drag (in corner, or effect of gravity) will slow down the model and it leads to prop slippage and slippage make induced drag on prop tips, so it means motor current is after all function of that speed difference. Since such regulator knows prop slippage, then it is easy to maintain rpm, so that the original rpm + regulation - slippage still equal to wanted speed. Regulator simply compensates slippage by rpm change. It is positive feedback system, so it should theoretically oscillate, but id does not to the point when the gain is less than slippage, so that the system has still some slowing under load. Exceeded gain will do oscillations.
But this system does just opposite we want in wind - for example if wind is comes from back of the prop (when model turns down from hour glass, or upper corner in squares), it will load the motor and regulator will add power just when I do not want it. That was reason why I needed to switch it off in final flights in Landres in that terrible turbulence day. Now I use accelerometer which can add uphill and brake downhill independently of wind outside so it works even better than 4-2-4 and all those problem with stability are solved (it does not mean that it does not create new problems :- PPP )
I heard Keith is already in Sofia, so I am packing also and see you then, I will show my system to Keith and I will see his in action and we will see what makes what in which conditions :- )))
Topic: KR version 2 timer (Read 5056 times)