Hi, dear colleges. My name is Robin and I am doing my PhD on UAVs in France. I build my drones with raspberry Pi and pixhawks. In terms of control a drone in the perspective of dynamics, the control inputs should be thrust force and torques, or angular velocity velocity of each motor (as there is …

@robin-ecn Yes. I think that is how the control group 0 is defined

Yes, I agree with this as the fight control group 0. As the mixing/actuator says 0: roll (-1…1) 1: pitch (-1…1) 2: yaw (-1…1) 3: throttle (0…1 normal range, -1…1 for variable pitch / thrust reversers) However I am not sure they are roll, pitch and yaw torques.:sweat_smile: (I am reading the …

@robin-ecn So you simply need to scale it to a reasonable amount. Why not just try it in SITL? I suspect that you are using ordinary ESCs which don’t have feedback. This means that you don’t know how much thrust the motors are going to generate exactly anyway. You can have a feel for example thrust…

@Jaeyoung-Lim Thanks for your help. I am trying with a certain scale mapping for this.:grin:

Perhaps someone that is more familiar with the PX4 control scheme can correct me, but if you are running your own controller, you can calculate the forces and torques through PID or whatever other controller you may be using and then treat the mapping to the body as a different problem. This is what…

@Jonathan_Wittmer Thanks for your reply. So in your previous work, what you did was just map the required force and torques to the four values between 0 and 1? All the mapping for your force and torques are linear? Then you publish them to the /actuator_control? Have your tried this in simulation o…

@robin-ecn Sorry for the delayed response. Yes that it what I did, I know that in reality, the relationship between force/torque and the ESC value is not linear (I think it is quadratic by the lift/drag equation), but a linear approximation worked pretty well. I use this on a real vehicle in practic…

@Jonathan_Wittmer thanks for your information:grinning. May I ask how you did your linear approximation ?

output = thrust/max_thrust. You can get max thrust by testing your motor/prop/ESC combination.

@Jonathan_Wittmer , But for the torques?

PX4: dynamic control need for a drone

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