Trimming simulink models using findop/linear analysis tool

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Hi all,
I'm having some issues using the findop function/linear analysis tool that Simulink provides. I've built a Simulink model of a quadcopter using simmechanics and now need to analyse its dynamics in the hover, but to do that I first need to trim it there. I've defined the model such that it has 4 inputs: Collective/throttle, pitch, roll and yaw commands.
When I try to trim the model, I set the states I wish to drive to steady-state or a known value (angular/linear velocities of the 6DoF joint that connects the quadcopter to the world to 0) and the trim 'completes' without issue, ie it seems to drive all these states to a steady state. However, the input states remain at their initial zero values so if I initialise the model with these trims, the quadcopter immediately drops out the sky due to having no commanded throttle.
It may be that I'm misunderstanding what this tool is trying to do, but I assumed that it would vary these input parameters to drive the required states to steady state. It definitely doesn't seem to be doing this as the inputs are not being changed at all even though multiple iterations are occurring through the trim process.
Am I using the right tool for the job? And if so, does anyone have any idea what I'm doing wrong?
Many thanks, Chris

Answers (1)

Drew Davis
Drew Davis on 12 Jun 2015
To determine the steady-state control input, you must ensure that your root level model has an input port feeding as an input into your plant when you trim the model.

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