Yuval Tassa
3d77eb1ef4
- Adhesion actuators using contact normals as force transmission mechanism. - Related video: https://youtu.be/HdBue4MUZys Closes #229 PiperOrigin-RevId: 464389367 Change-Id: I9f69b3cd152d957e8f65870d208788463c036a6d
139 lines
5.2 KiB
XML
139 lines
5.2 KiB
XML
<mujoco model="Active adhesion example">
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<size nconmax="500" njmax="1000"/>
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<visual>
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<headlight diffuse=".2 .2 .2"/>
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</visual>
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<default>
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<joint damping=".3" axis="0 1 0"/>
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<!--
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By adding 3mm of margin yet making solimp barely apply any force until 3mm penetration, we get
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3mm of "action at a distance". This is important so that small changes in distance don't lead
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to loss of adhesion
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-->
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<geom type="box" friction=".5" margin=".003" solimp="0 .99 .003 .9 6"/>
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<default class="wall">
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<geom rgba=".5 .5 .5 .4"/>
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</default>
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<default class="mechanical">
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<geom rgba=".5 .5 .8 1"/>
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<tendon rgba=".5 .5 .8 1"/>
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</default>
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<default class="active_adhesion">
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<geom rgba=".8 .5 .5 1"/>
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</default>
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<default class="object">
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<geom rgba=".5 .8 .5 1" density="100"/>
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</default>
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</default>
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<worldbody>
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<light pos="0.4 -.15 .6" dir="-1 .5 -1" diffuse=".7 .7 .7"/>
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<light pos="-.4 -.15 .6" dir="1 .5 -1" diffuse=".7 .7 .7"/>
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<body name="two crates">
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<joint name="conveyor" type="slide" damping="100" axis="1 0 0"/>
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<geom size=".2 .1 .01" pos="0 0 -.01"/>
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<geom size=".01 .08 .031" pos="-.19 0 .03" class="wall"/>
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<geom size=".01 .08 .031" pos="0 0 .03" class="wall"/>
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<geom size=".01 .08 .031" pos="0.19 0 .03" class="wall"/>
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<geom size="0.2 .01 .031" pos="0 -.09 .03" class="wall"/>
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<geom size="0.2 .01 .031" pos="0 0.09 .03" class="wall"/>
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</body>
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<body name="arm1" pos="-.1 0 .3" childclass="mechanical">
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<joint name="arm1"/>
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<geom type="cylinder" size=".015 .01" zaxis="0 1 0"/>
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<geom type="capsule" size=".01" fromto="0 0 0 -.12 0 -.07"/>
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<body name="arm2" pos="-.12 0 -.07">
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<joint name="arm2"/>
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<geom type="cylinder" size=".015 .01" zaxis="0 1 0"/>
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<geom type="capsule" size=".01" fromto="0 0 0 .12 0 -.07"/>
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<body name="4boxes" pos=".12 0 -.08" childclass="active_adhesion">
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<site name="force_sensor" group="3"/>
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<joint name="arm3" damping=".01" pos="0 -.03 0"/>
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<geom size=".015 .015 .01" pos="0.015 0.015 0"/>
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<geom size=".015 .015 .01" pos="0.015 -.015 0"/>
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<geom size=".015 .015 .01" pos="-.015 0.015 0"/>
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<geom size=".015 .015 .01" pos="-.015 -.015 0"/>
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</body>
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</body>
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</body>
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<body name="box" pos="-.1 0 .05">
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<freejoint/>
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<geom size=".05 .05 .05" class="object"/>
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</body>
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<body name="winch" pos="-.01 0 .35" childclass="mechanical">
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<joint name="winch" damping="1"/>
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<geom type="cylinder" size=".015 .01" zaxis="0 1 0"/>
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<geom type="capsule" size=".01" fromto="0 0 0 .1 0 .05"/>
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<site name="anchor" pos=".1 0 .04"/>
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</body>
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<site name="pulley" pos=".1 0 .32"/>
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<site name="hook_left" pos=".08 0 .3"/>
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<site name="hook_right" pos=".12 0 .3"/>
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<body name="sphere" pos=".1 0 .2" childclass="active_adhesion">
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<!--
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Note we are adding damping to a free joint. This is an easy yet unphysical way to prevent
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the sphere from jiggling too much on the winch tendons. An alternative would be to add fluid
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density or viscosity.
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-->
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<joint type="free" damping=".1"/>
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<!--
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The composite balls in the crate have only 3 linear DoFs with condim=1, effectively
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frictionless point particles. In order to make them stick to the sphere we give the sphere
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priority 2, to force condim=3.
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-->
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<geom type="sphere" size=".03" priority="2"/>
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<site name="pin_left" pos="-.025 0 .025"/>
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<site name="pin_right" pos=".025 0 .025"/>
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</body>
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<composite type="particle" count="4 4 4" spacing="0.025" offset=".11 .01 .1">
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<geom size=".012" rgba=".5 .8 .5 1" solref=".005 1"/>
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</composite>
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</worldbody>
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<equality>
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<joint joint1="arm1" joint2="arm2" polycoef="0 -.5 0 0 0"/>
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<joint joint1="arm3" joint2="arm1"/>
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</equality>
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<!--
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By using divisor=3 in the pullies we increase the distance by which the hanging sphere moves
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relative to the motion of the winch arm. One should imagine a double spindle with two radii that
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creates a ratio of 1.5 between the motion of tendon before the pullies and after the pullies.
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(1.5 rather than 3 because the tendon has 2 branches and the length is split between them)
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-->
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<tendon>
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<spatial range="0 .19" limited="true" solreflimit=".01 2" class="mechanical">
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<site site="anchor"/>
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<site site="pulley"/>
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<pulley divisor="3"/>
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<site site="pulley"/>
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<site site="hook_left"/>
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<site site="pin_left"/>
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<pulley divisor="3"/>
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<site site="pulley"/>
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<site site="hook_right"/>
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<site site="pin_right"/>
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</spatial>
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</tendon>
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<actuator>
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<position name="conveyor" joint="conveyor" ctrlrange="-.2 .2" ctrllimited="true" kp="400"/>
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<position name="arm" joint="arm2" ctrlrange="-.8 1" ctrllimited="true" kp="10"/>
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<adhesion name="adhere_arm" body="4boxes" ctrlrange="0 1" gain="20"/>
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<position name="winch" joint="winch" ctrlrange="-.7 .5" ctrllimited="true" kp="10"/>
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<adhesion name="adhere_winch" body="sphere" ctrlrange="0 1" gain="20"/>
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</actuator>
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<sensor>
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<force site="force_sensor"/>
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</sensor>
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</mujoco>
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