In gazebo_motor_model.cpp , what is the unit for the motor_constant and where is the moment calculated?
mariam0amin opened this issue · comments
in this line of code -----> ignition::math::Vector3d drag_torque(0, 0, -turning_direction_ * force * moment_constant_);
is this the calculation for the moment? and if it is, how is it force* moment constant? does this mean moment constant unit is meters??
Thanks in advance
Based on these notes which try to explain the gazebo parameters for the motor model, you might actually be right.
The units of ω is [Time^-2], there is no radians involved
Motor constant is in (kg)(m).
Moment constant is in (m)
According to the code for motor constant and force:
Motor Constant = Thrust / (Angular_rate^2)
Units of motor constant = [Mass][Length][Time^2] / [Time^2] = [Mass][Length]
According to the code for moment constant and torque:
Moment Constant = (Torque about z axis) / (Thrust along z axis)
Units of Moment constant = [Mass][Length^2][Time^2] / [Mass][Length][Time^2] = [Length]
@JohnTGZ Thanks, I appreciate your help; but, do you know how I may obtain the motor constant in this case? I used to conduct an experimental analysis in which I measured the thrust and the rotor velocity in rpm or rad/sec that corresponded to this thrust. After fitting the data, I obtained the motor constant. However, now that you are saying that it is angular rate, how can I obtain the motor constant in that case? or simply that radians are dimensionless?