actuators not doing anything #2389

shogan50 · 2025-01-27T13:38:33Z

shogan50
Jan 27, 2025

Intro

Hi!
I'm a principal mechanical engineer working on a wind energy project.

My setup

Python, Windows

My question

Lift and drag actuators don't do anything in this XML. Why is that?
The forces aren't reflected in the thrust or tension sensors.

Minimal model and/or code that explain my question


<mujoco>
  <default>
    <joint type="hinge" axis="0 -1 0"/>
    <geom type="capsule" size=".02"/>
  </default>

  <option timestep="0.001">
    <flag 
      contact="disable" 
      energy="enable" 
      passive="enable"
    />
  </option>

  <asset>
    <texture name="texplane" type="2d" builtin="checker" rgb1="0.2 0.3 0.4" rgb2="0.1 0.2 0.3" width="100" height="100"/>
    <material name="matplane" texture="texplane" texrepeat="1 1" texuniform="true"/>
    <mesh name="wind_sock" file="wind_sock.stl" scale="3 3 3"/>
  </asset>

  <worldbody>
    <camera name="fixed" pos="0 -25 12" xyaxes="1 0 0 0 1 2"/>
    <camera name="closeup" pos="0 -.1 .07" xyaxes="1 0 0 0 1 2"/>
    <light diffuse=".5 .5 .5" pos="0 0 3" dir="0 0 -1"/>
    <light pos="0 -.4 1"/>
    <geom type="plane" size="5 5 0.1" rgba=".9 .9 .9 1"/>

    <body name="mast" pos="0 0 0">
      <joint name="mast_joint" type="hinge" armature="8000" axis="0 0 1"/>
      <geom name="mast_geom" type="cylinder" size=".1" fromto="0 0 0 0 0 3.0" rgba="1 0 0 1"/>
      <site name="mast" pos="0 0 0" size="0.1"/>
      
      <body name="arm" pos="0 0 3">
        <!-- <joint name="torque" type="hinge" axis="0 0 1" springdamper=".005 1"/> -->
        <geom name="arm_geom" type="cylinder" fromto="0 0 0 1 0 0" size=".05" rgba="1 0 0 1"/>
        <site name="arm_site" pos="0 0 0" size=".1"/>
        
        <body name="tether" pos="1 0 0">
          <!-- <joint name="tether_joint" type="hinge" axis="0 0 1"/> -->
          <geom name="tether_geom" type="cylinder" mass=".1" fromto="0 0 0 10 0 0" size=".025" rgba="0 1 1 1"/>
          <site name="tether" pos="0 0 0" size="0.1"/>
          
          <body name="foil" pos="10 0 0">
            <geom name="foil_top" type="cylinder" mass="1.5" size="0.0625 .6" rgba="0 0.8 0 1"/>
            <site name="foil_cg" pos="0 0 0" size="0.1"/>
            
            <body name="wind_vane" pos="0 0 0">
              <joint name="wind_joint" type="hinge" damping=".01" axis="0 0 1"/>
              <geom name="wind_geom" type="cylinder" mass="0.01" fromto="0 0 0 0 3 0" size=".05" rgba="0 1 0 1"/>
              <site name="alpha_center" pos="0 0 0" size="1.0"/>
              
              <body name="alpha_vane" pos="0 0 0">
                <joint name="alpha_joint" type="hinge" damping=".10" axis="0 0 1"/>
                <geom name="alpha_geom" type="cylinder" mass="0.01" fromto="0 0 0 0 3 0" size=".05" rgba="1 1 0 1"/>
              </body>
            </body>
          </body>
        </body>
      </body>
    </body>

    <body name="wind_sock" pos="0 0 .5">
      <joint name="wind_sock_joint" type="hinge" axis="0 0 1" damping=".01"/>
      <geom name="wind_sock_geom" type="mesh" mesh="wind_sock"/>
      <site name="wind_sock" pos="0 0 0" size="0.1"/>
    </body>
  </worldbody>

  <actuator>
    <velocity name="mast_motor" joint="mast_joint" kv="10000000"/>
    <!-- <general name="mast_motor" site="mast" gear="0 0 0 0 0 1"/> remember body is contact. use site -->
    <position name="wind_vane" joint="wind_joint" kp="1000" kv="10"/>
    <position name="alpha_vane" joint="alpha_joint" kp="1000"/>
    <general name="lift" site="alpha_center" gaintype="fixed" gear="1 0 0 0 0 0"/>
    <general name="drag" site="alpha_center" gaintype="fixed" gear="0 1 0 0 0 0"/>
    <position name="wind_sock" joint="wind_sock_joint" kp="10000" kv="1000"/>
  </actuator>

  <sensor>
    <framelinvel name="foil_vel" objtype="body" objname="foil"/>
    <torque name="arm_torque" site="arm_site"/>
    <force name="thrust" site="foil_cg"/>
    <force name="tension" site="tether"/>
  </sensor>

  <custom>
    <numeric name="alpha" size="1" data="0"/>
    <numeric name="energy" size="1" data="0"/><!-- [cumulative energy: This tag stores the total energy accumulated over time during the simulation] -->
  </custom>
</mujoco>

Confirmations

I searched the latest documentation thoroughly before posting.
I searched previous Issues and Discussions, I am certain this has not been raised before.

yuvaltassa · 2025-02-03T10:20:55Z

yuvaltassa
Feb 3, 2025
Maintainer

I increased the the gear values from 1 to 1e6 and there is quite a bit of movement.

I don't really understand your model to comment further, but the kv value of 1e7 looks sus.

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actuators not doing anything #2389

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actuators not doing anything #2389

shogan50 Jan 27, 2025

Intro

My setup

My question

Minimal model and/or code that explain my question

Confirmations

Replies: 1 comment

yuvaltassa Feb 3, 2025 Maintainer

shogan50
Jan 27, 2025

yuvaltassa
Feb 3, 2025
Maintainer