How to implement a series elastic actuator and a parallel elastic actuator #2140

haru425 · 2024-10-15T10:26:13Z

haru425
Oct 15, 2024

Intro

Hi!

I am a graduate student at Tokyo Institue of Technology. I use MuJoCo for my research on soft robotics.

My setup

mujoco version is 3.2.3.

And I have written the following xml.

<mujoco model="simple_robot">
    <compiler coordinate="local" angle="degree" />
    <option timestep="0.01" />
    <asset>
        <texture type="skybox" builtin="gradient" rgb1="0.3 0.5 0.7" rgb2="0 0 0" width="512" height="3072"/>
        <texture type="2d" name="groundplane" builtin="checker" mark="edge" rgb1="0.2 0.3 0.4" rgb2="0.1 0.2 0.3"
            markrgb="0.8 0.8 0.8" width="300" height="300"/>
        <material name="groundplane" texture="groundplane" texuniform="true" texrepeat="5 5" reflectance="0.2"/>
    </asset>

    <worldbody>
        <light mode="targetbodycom" target="base" pos="0 0 10" diffuse="50 50 50" specular="100 100 100"/>
        <geom name="floor" size="0 0 0.01" type="plane" material="groundplane"/>

        <body name="base" pos="0 0 0.1">
            <geom type="box" size="0.5 0.5 0.1" rgba="1 0 0 0.5" mass="5"/>
            <joint type="free" name="base_joint"/>
            <body name="arm1" pos="0.39 0 0.40" euler="0 45 0">
                <geom type="capsule" size="0.05 0.50" rgba="0 1 0 0.5"/>
                <body name="arm2" pos="0 0 1" euler="0 0 0">
                    <geom type="capsule" size="0.05 0.50" rgba="0 0 1 0.5"/>
                    <joint type="hinge" name="joint1" axis="0 1 0" pos="0 0 -0.5" range="-180 180"/>
                </body>
            </body>
        </body>
    </worldbody>

    <actuator>
        <motor joint="joint1" gear="10" />
    </actuator>

</mujoco>

My question

I am considering implementing a series elastic actuator and a parallel elastic actuator for joint1 in the above XML file. How can I implement each of these?

Does modifying it as shown below represent a parallel elastic actuator?

<joint type="hinge" name="joint1" axis="0 1 0" pos="0 0 -0.5" range="-180 180" stiffness="50"/>

Also, I referred to #226, does modifying it as shown below represent a series elastic actuator? is this modification is enough?

<joint type="hinge" name="joint1" axis="0 1 0" pos="0 0 -0.5" range="-180 180" armature="1"/>

I am a beginner with MuJoCo, so I don't understand it well.
Thank you.

Minimal model and/or code that explain my question

No response

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 · 2024-10-30T14:34:14Z

yuvaltassa
Oct 30, 2024
Maintainer

What is a series elastic actuator?
What is a parallel elastic actuator

0 replies

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

How to implement a series elastic actuator and a parallel elastic actuator #2140

{{title}}

Replies: 1 comment

{{title}}

Select a reply

How to implement a series elastic actuator and a parallel elastic actuator #2140

haru425 Oct 15, 2024

Intro

My setup

My question

Minimal model and/or code that explain my question

Confirmations

Replies: 1 comment

yuvaltassa Oct 30, 2024 Maintainer

haru425
Oct 15, 2024

yuvaltassa
Oct 30, 2024
Maintainer