Yuval Tassa
a264d0bc8b
https://youtu.be/GioWwB36XHI The new geom attribute adhesion (units of force, signed; pair-level override) translates the contact friction cone along its normal so that the force origin lies strictly inside it. Consequences: each contact can pull with up to the given force before breaking, and the tangential friction budget becomes mu*(f_N + adhesion) -- the Mohr-Coulomb yield condition with cohesion c = mu*adhesion -- so lightly-squeezed grasps retain a guaranteed friction floor. A translated cone factors exactly into {constant attractive force} + {original cone}, so no solver kernels change. The implementation is this factorization: a constant attraction along contact normals accumulated into the new mjData.qfrc_adhesion (summed into qfrc_passive), plus a bias of adhesive contact rows' reference acceleration (aref += R*adhesion), which makes resting penetration exactly independent of adhesion. Contacts of adhesive pairs remain active throughout the gap zone, producing rows with positive violation whose reference acceleration pulls: a tether that resists pull-off smoothly, captures objects released within the band into steady contact, and detaches at the specified force. Adhesion values of the two geoms combine by sum; explicit pairs override. mj_contactForce reports the net interface force (cone force minus the adhesive pull), whose normal component can now be negative. Negative adhesion is allowed and produces a repulsive offset (air hockey). PiperOrigin-RevId: 950858148 Change-Id: I879c08eba7ae501e5c0f8c2f807167344da4c2bc
55 lines
2.6 KiB
XML
55 lines
2.6 KiB
XML
<mujoco model="Magnetic fridge door">
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<!-- The two dark strips are magnets, modeled with adhesion: within the gap band
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(the magnet's range) they attract with the summed adhesion of the pair, so a
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nearly-closed door snaps shut on its own and stays latched; pulling harder
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than the pull-off force pops it open cleanly. Drag the door with Ctrl+drag
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after double-clicking it. -->
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<option cone="elliptic"/>
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<statistic center="0 0 .4" extent="1.4" meansize="0.03"/>
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<visual>
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<headlight diffuse=".8 .8 .8" ambient=".3 .3 .3"/>
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<map stiffness="30"/>
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</visual>
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<asset>
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<texture type="skybox" builtin="gradient" rgb1=".5 .6 .7" rgb2=".9 .9 .95" width="32" height="512"/>
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<material name="body" rgba=".92 .92 .94 1" reflectance=".3"/>
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<material name="inside" rgba=".8 .8 .82 1"/>
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<material name="magnet" rgba=".2 .2 .22 1"/>
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</asset>
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<worldbody>
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<light pos="1.5 -.5 2" dir="-.6 .2 -.75" diffuse=".7 .7 .7" intensity="200000"/>
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<geom name="floor" type="plane" size="2 2 .01" rgba=".7 .75 .7 1"/>
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<!-- cabinet: interior x [-.35 0], y [-.25 .25], z [0 .8] -->
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<geom name="left" type="box" size=".175 .015 .4" pos="-.175 -.235 .4" material="body"/>
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<geom name="right" type="box" size=".175 .015 .4" pos="-.175 .235 .4" material="body"/>
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<geom name="top" type="box" size=".175 .25 .015" pos="-.175 0 .785" material="body"/>
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<geom name="bottom" type="box" size=".175 .25 .015" pos="-.175 0 .03" material="body"/>
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<geom name="back" type="box" size=".015 .25 .4" pos="-.335 0 .4" material="body"/>
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<geom name="shelf" type="box" size=".155 .21 .008" pos="-.18 0 .4" material="inside"/>
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<!-- frame magnet strip, just inside the right wall's front edge -->
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<geom name="magnet1" type="box" size=".005 .01 .3" pos="-.015 .19 .4" material="magnet" adhesion="1.5" gap=".003"/>
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<body name="door" pos="0 -.25 .42">
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<joint name="hinge" pos="0 0 0" axis="0 0 -1" range="0 135" damping=".08" stiffness="0.05"/>
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<geom name="hinge" type="cylinder" size=".007" fromto="0 0 -.37 0 0 .37" rgba=".4 .4 .42 1" contype="0" conaffinity="0"/>
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<geom name="panel" type="box" size=".015 .24 .37" pos=".015 .25 0" material="body" mass="1.5"/>
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<body name="handle">
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<geom name="handle" type="capsule" size=".012" fromto=".06 .46 -.12 .06 .46 .12" rgba=".4 .4 .42 1" mass=".1"/>
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</body>
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<geom name="magnet2" type="box" size=".005 .01 .3" pos="-.005 .44 0" material="magnet" adhesion="1.5" gap=".003" mass=".05"/>
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</body>
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</worldbody>
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<keyframe>
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<key name="open" qpos="1.6"/>
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<key name="ajar" qpos=".006"/>
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</keyframe>
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</mujoco>
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