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HKUST-Aerial-Robotics / Teach-Repeat-Replan

Teach-Repeat-Replan: A Complete and Robust System for Aggressive Flight in Complex Environments
GNU General Public License v3.0
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About estimating hover thrust online. #22

Closed tlb9551 closed 5 years ago

tlb9551 commented 5 years ago

When using the THRUST command to control the N3 flight control to achieve the desired FORCE (always oriented toward the +z-axis of the body frame), there is always a problem that how to find the mapping between the thrust and the force. I noticed that in your code, you try to use a class HovThrKF to estimate hover thrust online. HovThrKF::update() use the Kalman filter, but this function is never used. https://github.com/HKUST-Aerial-Robotics/Teach-Repeat-Replan/blob/7900aa660831b5b766eb7898c0dbcc30a7bee009/onboard_computer/controller/n3ctrl/src/N3CtrlFSM_control.cpp#L95 HovThrKF::simple_update() use a simple filter, and the relationship between thrust and force is considered to be proportional. Means: F = c * thrust. Is this based on some facts? I have ever worked on PX4 (Pixhawk), and I used to think that thrust is proportional to rotor speed w, and force is proportional to w^2, so the thrust is proportional to sqrt(force).

bigsuperZZZX commented 5 years ago

Yes we consider force is proportional to thrust. If you read the code in function Controller::update in Teach-Repeat-Replan/onboard_computer/controller/n3ctrl/src/controller.cpp, you will notice that we use a simple proportional model as well.

tlb9551 commented 5 years ago

@bigsuperZZZX Thank you for your reply, I understand now. All is well.