High Thrust Calculation in Motor Model Plugin

[Kametor]

Environment

• OS Version: Ubuntu 22.04
• Gazebo Harmonic

Description

• There may be a misunderstanding or misuse of the Gazebo motor model plugin parameters. Specifically, the “maxRotVelocity” parameter, which is described as the “Maximum rotational velocity command in units of rad/s”, seems to be leading to unintended results in the thrust calculation.
  The thrust force is computed using the following equation:

thrust = realMotorVelocity * realMotorVelocity * this->motorConstant;
Here, the variable realMotorVelocity is defined as:

double realMotorVelocity = motorRotVel * this->rotorVelocitySlowdownSim;
Consequently, at full throttle, the resulting force calculation is:

(maxRotVelocity * 10)^2 * motorConstant.
Based on my calculations, the resulting force in Gazebo appears significantly higher than expected. I am uncertain if I am misinterpreting a specific aspect of the model or if there is an issue with the parameter setup. In my calculation the thrust force is very high. Also drone climbs very fast. I think there is a problem. Any guidance or insight into this discrepancy would be greatly appreciated.

[Kametor]

As observed, the ESC PWM values are approximately 250, while the joystick input remains below the halfway mark. Despite this moderate input, the drone exhibits rapid ascent behavior. The custom parameters currently in use are as follows:

<plugin filename="gz-sim-multicopter-motor-model-system" name="gz::sim::systems::MulticopterMotorModel">
  <jointName>rotor_0_joint</jointName>
  <linkName>rotor_0</linkName>
  <turningDirection>ccw</turningDirection>
  <timeConstantUp>0.0125</timeConstantUp>
  <timeConstantDown>0.025</timeConstantDown>
  <maxRotVelocity>313.0</maxRotVelocity>
  <motorConstant>830.0e-06</motorConstant>
  <momentConstant>0.03</momentConstant>
  <commandSubTopic>command/motor_speed</commandSubTopic>
  <motorNumber>0</motorNumber>
  <rotorDragCoefficient>0.001</rotorDragCoefficient>
  <rollingMomentCoefficient>0.001</rollingMomentCoefficient>
  <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
  <motorType>velocity</motorType>
</plugin>

Additionally, the drone has a total weight of 45 kg.