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Nimrod Gileadi 002b427a32 PID Controller as an actuator plugin.

Implement a configurable PID controller.

PiperOrigin-RevId: 585282014
Change-Id: I2d884554629101a0a25b5e0979ffb1ff8ed9cab4

2023-11-25 08:41:01 -08:00

3.3 KiB

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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`. One state variable will :

:        :be added to `mjData.plugin_state`, to indicate whether the previous value of `ctrl` should be used (0 on first step, 1           :

:        :otherwise).                                                                                                                          :

3.3 KiB Raw Blame History

Actuator plugins

PID

3.3 KiB

Raw Blame History