model set to be fixed to world keeps jittering

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Background: I want to set one of the box object to be fixed to the world.

What I have tried:

if an object set to be fixed to the world, it will keeps jittering. According to my search, some say it could be inertia problem. Though I change it according to formula of uniform 3d object, and it still doesn't work

Source code:

Here is the wall.xacro // script I show has commented the below code

Code below used to make box object fixed to world.

<!-- wall fixed to the world-->
    <link name="world"/>

    <joint name="base_link_fixed" type="fixed">
      <parent link="world"/>
      <child link="wall_link"/>
    </joint>

Problem:

However, the box turns out to be jittering all the time like dancing!!

Solution Found

Thank WarwickWagon's answer. The first solution works well.