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Re: [Paparazzi-devel] stabilization parameters

From: Gautier Hattenberger
Subject: Re: [Paparazzi-devel] stabilization parameters
Date: Wed, 28 Nov 2012 14:24:52 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.10) Gecko/20121027 Icedove/10.0.10

The reference model used to filter to (auto/human)pilot inputs is a second order equation like this:
angular_acceleration + 2*damp*freq*angular_speed + freq*freq*angle = angle_input
So, for each new input, we compute the angular_acceleration and integrate it twice to get the reference angle and angular speed. Moreover, the acceleration and speed are bounded.

Now, to change the behavior of the model:
SP_MAX: bound for angle input
REF_OMEGA: natural frequency of the second order
REF_ZETA: damping factor (should not be less than 0.8-0.7, maximum is 1)
REF_MAX_X: bound on angular speed
REF_MAX_XDOT: bound on angular acceleration

The response time (95% of the final value when doing a step input): ~ 3/(freq*damp)

To increase response time, you can increase the frequency, and the bounds. But if the tracking of the reference model (with the feedback gains PGAIN, DGAIN and IGAIN) is not good, it will not change that much the way it works.
Also, if the sensitivity of your IMU is wrong, the estimated angles will not be correct, and the control will be either too fast or too slow.


Le 28/11/2012 02:31, Eduardo lavratti a écrit :
Anyone can explain this parameter from STABILIZATION_ATTITUDE ?
i like to make the YAW with fast response.

I think the YAW response of paparazzi is too slow with default parameter.
I fly acrobatic heli and when i fly the ppz its very artificial yaw reaction.

Some time i do yaw command and when i release the stick the rotorcraft continue yawing some degrees .. 10 ~ 30deg
Is about this problem i prefer the yaw more like ACRO mode.

In my own code i do this for YAW axis.

when i do some RC YAW command the yaw work like RATE then when i release the command ATTITUDE lock the yaw.
Is like the RC act only in gyro not in ATTITUDE.

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