N1 limiter ...

[Guest]

Hi again,Most modern aircraft have some type of N1 limiter built into the AutoThrottle.I've been trying to create such a thing all week-end (spent about 8 hours testing all kind of algorithms to simulate this) but I just didn't succeed !Basically I want to do 2 things: a) make sure the N1 value never exceeds the limit calculated by the N1 computer (e.g. Max N1=110%):( add an "N1" autothrottle button which moves the throttles forward so the maximum N1 is reached and maintained (e.g. during take-off).The main problem off course is that the throttle setting is not directly related to the N1 reading of the engine in that the engine takes time to stabilise at a certain setting, which takes much longer than it takes the throttle handle to move.Any ideas ?Thanks for the help,Bj

[Guest IanK]

>Hi again, >>Most modern aircraft have some type of N1 limiter built into >the AutoThrottle. >>I've been trying to create such a thing all week-end (spent >about 8 hours testing all kind of algorithms to simulate >this) but I just didn't succeed ! >>Basically I want to do 2 things: >>a) make sure the N1 value never exceeds the limit calculated >by the N1 computer (e.g. Max N1=110%) >>:( add an "N1" autothrottle button which moves the throttles >forward so the maximum N1 is reached and maintained (e.g. >during take-off). >>The main problem off course is that the throttle setting is >not directly related to the N1 reading of the engine in that >the engine takes time to stabilise at a certain setting, >which takes much longer than it takes the throttle handle to >move. >>Any ideas ? >>Thanks for the help, >Bj

[Guest Fabio Miguez]

Hey Ian.Never heard of the decode forum, but sounds interesting! Is it in the other site?

[Guest IanK]

>Hey Ian. >>Never heard of the decode forum, but sounds interesting! Is >it in the other site? Yes it's on a link from there. Maybe it is not very obvious.AirFile Decoding and Research Board athttp://www.avhistory.org/cgi-bin/boards/Cf...ebbbs_config.plHave a good weekend,Ian

[Guest Fabio Miguez]

Hey Ian.Great forum, thanks for the link!Have a good weekend too.

[Guest Ron Freimuth]

>Hi again, >>Most modern aircraft have some type of N1 limiter built into >the AutoThrottle. >>I've been trying to create such a thing all week-end (spent >Basically I want to do 2 things: >>a) make sure the N1 value never exceeds the limit calculated >by the N1 computer (e.g. Max N1=110%) >>:( add an "N1" autothrottle button which moves the throttles >forward so the maximum N1 is reached and maintained (e.g. >during take-off). >Thanks for the help, >Bj

[Guest]

Hi Bj

[pacosancas 0]

Hi,One way to do this is:if ((desired_n1 - actual_n1)<0)new_throttle = old_throttle + constant1*(desired_n1 - actual_n1) + constant2*(actual_n1 - old_n1);N1 is to be read at regular intervals, Old_N1 and old_throttle are the values read at the previous interval, Actual_N1 is the one currently read.Playing with Constant1 and constant2, you can achieve a stable N1 variationPacoStultorum numerus infinitus est.

[pacosancas 0]

Hi again, There is a variation that can give better results in some cases:if ((desired_n1 - actual_n1)<0)new_throttle = old_throttle + constant1*(desired_n1 - actual_n1) + constant2*(actual_n1 - old_n1)*(actual_n1 - old_n1); // or even ^3In some cases it might be necessary to introduce another correction factor taking into consideration other variables influenced by the throttle, such as n2 in your case. For example:if ((desired_n1 - actual_n1)<0)new_throttle = old_throttle + constant1*(desired_n1 - actual_n1) + constant2*(actual_n1 - old_n1) + constant3*(actual_n2 - old_n2); //each of these two factors can be ^2 or ^3 as abovethat was the case of the Power managenet gauge in my atr's, as they adjust the power levers to keep a constant torque on the propellers, but the torque variation is very delayed with respect to the power lever variation.PacoStultorum numerus infinitus est.