Files
Mujoco_WASM/plugin/actuator
Sam Haves f2461f9ce6 Modify mj_PLUGIN_LIB_INIT to support multiple plugins in the same compilation unit.
Previously on MSVC we used DllMain to register plugins, you cannot have multiple definitions of DllMain in a single unit so you would get errors if you tried to register two plugins. This modifies the implementation to insert a function pointer into the C runtime initialization instead.

PiperOrigin-RevId: 896612678
Change-Id: I07732147b955d741c836acff6da986db0e9b9eff
2026-04-08 11:35:16 -07:00
..
2024-07-25 13:31:13 -07:00

Actuator plugins

PID

The mujoco.pid actuator plugin implements a configurable PID controller:

f(t) = K_\text{p} e(t) + K_\text{i} \int_0^t e(\tau) \mathrm{d}\tau + K_\text{d} \frac{\mathrm{d}e(t)}{\mathrm{d}t},

where e(t) = u(t) - \ell(t) is the difference between the control u and the actuator length \ell.

You can use it like:

<mujoco>
  <extension>
    <plugin plugin="mujoco.pid">
      <instance name="pid">
        <config key="kp" value="40.0"/>
        <config key="ki" value="40"/>
        <config key="kd" value="4"/>
        <config key="slewmax" value="3" />
        <config key="imax" value="1"/>
      </instance>
    </plugin>
  </extension>

  <worldbody>
    <body>
      <joint name="j" type="slide" axis="0 0 1" />
      <geom size="0.01" mass="1"/>
    </body>
  </worldbody>

  <actuator>
    <plugin joint="j" plugin="mujoco.pid" instance="pid" />
  </actuator>
</mujoco>

The available options are:

Attribute Default Meaning
kp 0 P gain for the controller.
ki 0 I gain for the controller.

If nonzero, one activation variable will be added to mjData.act, containing the current I term (in units of force).

kd 0 D gain for the controller.
imax Optional If specified, the force produced by the I term will be clipped to the range [-imax, imax].
slewmax Optional The maximum rate at which the setpoint for the PID controller can change.

If a bigger change is requested between two timesteps, it will be clipped to the range [ctrl - slewmax * dt, ctrl + slewmax * dt]

If specified, one activation variable will be added to mjData.act containing the previous value of ctrl.