How to create a plugin for several actuators?

[pucciland95]

Intro

Hi!

I am a Robotics Engineer at Hiro Robotics in Italy; I use MuJoCo for my research on Reinforcement Learning and Imitation Learning.

My setup

Mujoco version: 3.2.6, API: C, OS: Linux Ubuntu 22.04 Linux

My question

I am trying to develop a Ros2 Control package for Mujoco so that it is possible to make the robot move from ROS2 and load it as a Mujoco Plugin to use it in combination with other plugins.

As of now, I have managed to make the plugin work, and the robot is controllable from ROS2. However, the robot moves because I set the joint state (aka qvel in mj_data). This is not consistent since when I make my robot collide with the objects in the workspace, it passes through them since it is not a 'real' control input.

This is how I am currently doing to 'control' the robot in mujoco:

if (joint_state.is_velocity_control_enabled)
  mj_data_->qvel[joint_state.mj_vel_adr] = joint_state.velocity_command;

Therefore, since the ur10e model exposes some actuators:

<actuator>
  <general class="size4" name="shoulder_pan" joint="shoulder_pan_joint"/>
  <general class="size4" name="shoulder_lift" joint="shoulder_lift_joint"/>
  <general class="size3_limited" name="elbow" joint="elbow_joint"/>
  <general class="size2" name="wrist_1" joint="wrist_1_joint"/>
  <general class="size2" name="wrist_2" joint="wrist_2_joint"/>
  <general class="size2" name="wrist_3" joint="wrist_3_joint"/>
</actuator>

I wanted to get them in my plugin and control them. However, I do not understand why my plugin cannot find them.
Here how I look for the actuators:

std::string act_name = acturator_names[joint_index];
int mujoco_actuator_id = mj_name2id(mj_model_, mjtObj::mjOBJ_ACTUATOR, act_name.c_str());

if(mujoco_actuator_id = -1)
{
   RCLCPP_ERROR_STREAM(logger_, "Failed to find actuator in mujoco model, actuator name: " << act_name);
   continue;
}

Probably the reason is that my plugin has only the following capability:

plugin.capabilityflags |= mjPLUGIN_PASSIVE;

Setting the mjPLUGIN_ACTUATOR requires specifying the transmission associated with the plugin; however, I have several transmissions to associate with the plugin since the robot has 6 degrees of freedom.
Is it possible to achieve this? Is there some other way I am not considering here?

Here is the repo as a reference.

Minimal model and/or code that explain my question

No response

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• I searched previous Issues and Discussions, I am certain this has not been raised before.