Add geom adhesion: contacts that pull, via translated friction cones.
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
This commit is contained in:
Yuval Tassa
committed by
Copybara-Service
Copybara-Service
parent
b942c9f922
commit
a264d0bc8b
@@ -46,6 +46,7 @@ typedef struct mjContact_ { // result of collision detection functions
|
||||
mjtNum solref[mjNREF]; // constraint solver reference, normal direction
|
||||
mjtNum solreffriction[mjNREF]; // constraint solver reference, friction directions
|
||||
mjtNum solimp[mjNIMP]; // constraint solver impedance
|
||||
mjtNum adhesion; // adhesive force along the contact normal
|
||||
|
||||
// internal storage used by solver
|
||||
mjtNum mu; // friction of regularized cone, set by mj_makeConstraint
|
||||
@@ -287,6 +288,7 @@ typedef struct mjData_ {
|
||||
mjtNum* qfrc_damper; // passive damper force (nv x 1)
|
||||
mjtNum* qfrc_gravcomp; // passive gravity compensation force (nv x 1)
|
||||
mjtNum* qfrc_fluid; // passive fluid force (nv x 1)
|
||||
mjtNum* qfrc_adhesion; // passive contact adhesion force (nv x 1)
|
||||
mjtNum* qfrc_passive; // total passive force (nv x 1)
|
||||
|
||||
// computed by mj_sensorVel/mj_subtreeVel if needed
|
||||
|
||||
@@ -350,6 +350,7 @@ typedef struct mjModel_ {
|
||||
|
||||
mjtBool flg_gravcomp; // whether any body has nonzero gravcomp
|
||||
mjtBool flg_surfacevel; // whether any geom has nonzero surfacevel
|
||||
mjtBool flg_adhesion; // whether any geom or pair has nonzero adhesion
|
||||
|
||||
// ------------------------------- options and statistics
|
||||
|
||||
@@ -478,6 +479,7 @@ typedef struct mjModel_ {
|
||||
mjtNum* geom_margin; // geometric inflation for contact (ngeom x 1)
|
||||
mjtNum* geom_gap; // additional contact detection buffer (ngeom x 1)
|
||||
mjtNum* geom_surfacevel; // surface velocity in local frame: lin,ang (ngeom x 6)
|
||||
mjtNum* geom_adhesion; // adhesive force of contacts (ngeom x 1)
|
||||
mjtNum* geom_fluid; // fluid interaction parameters (ngeom x mjNFLUID)
|
||||
mjtNum* geom_user; // user data (ngeom x nuser_geom)
|
||||
float* geom_rgba; // rgba when material is omitted (ngeom x 4)
|
||||
@@ -721,6 +723,7 @@ typedef struct mjModel_ {
|
||||
mjtNum* pair_solimp; // solver impedance: contact (npair x mjNIMP)
|
||||
mjtNum* pair_margin; // geometric inflation for contact (npair x 1)
|
||||
mjtNum* pair_gap; // additional contact detection buffer (npair x 1)
|
||||
mjtNum* pair_adhesion; // adhesive force of contacts (npair x 1)
|
||||
mjtNum* pair_friction; // tangent1, 2, spin, roll1, 2 (npair x 5)
|
||||
|
||||
// excluded body pairs for collision detection
|
||||
|
||||
@@ -359,6 +359,7 @@ typedef struct mjsGeom_ { // geom specification
|
||||
double margin; // margin for contact detection
|
||||
double gap; // additional contact detection buffer
|
||||
double surfacevel[6]; // surface velocity in local frame: linear, angular
|
||||
double adhesion; // adhesive force of contacts
|
||||
|
||||
// inertia inference
|
||||
double mass; // used to compute density
|
||||
@@ -642,6 +643,7 @@ typedef struct mjsPair_ { // pair specification
|
||||
mjtNum solimp[mjNIMP]; // solver impedance
|
||||
double margin; // margin for contact detection
|
||||
double gap; // additional contact detection buffer
|
||||
double adhesion; // adhesive force of contacts
|
||||
double friction[5]; // full contact friction
|
||||
mjString* info; // message appended to errors
|
||||
} mjsPair;
|
||||
|
||||
@@ -183,6 +183,7 @@
|
||||
X ( double, margin, 1 ) \
|
||||
X ( double, gap, 1 ) \
|
||||
XVEC( double, surfacevel, 6 ) \
|
||||
X ( double, adhesion, 1 ) \
|
||||
X ( double, mass, 1 ) \
|
||||
X ( double, density, 1 ) \
|
||||
X ( mjtGeomInertia, typeinertia, 1 ) \
|
||||
@@ -421,6 +422,7 @@
|
||||
XVEC( mjtNum, solimp, mjNIMP ) \
|
||||
X ( double, margin, 1 ) \
|
||||
X ( double, gap, 1 ) \
|
||||
X ( double, adhesion, 1 ) \
|
||||
XVEC( double, friction, 5 ) \
|
||||
X ( mjString*, info, 1 )
|
||||
|
||||
|
||||
@@ -386,6 +386,7 @@
|
||||
X ( mjtNum, geom_margin, ngeom, 1 ) \
|
||||
X ( mjtNum, geom_gap, ngeom, 1 ) \
|
||||
X ( mjtNum, geom_surfacevel, ngeom, 6 ) \
|
||||
X ( mjtNum, geom_adhesion, ngeom, 1 ) \
|
||||
XNV ( mjtNum, geom_fluid, ngeom, mjNFLUID ) \
|
||||
X ( mjtNum, geom_user, ngeom, MJ_M(nuser_geom) ) \
|
||||
X ( float, geom_rgba, ngeom, 4 )
|
||||
@@ -627,6 +628,7 @@
|
||||
X ( mjtNum, pair_solimp, npair, mjNIMP ) \
|
||||
X ( mjtNum, pair_margin, npair, 1 ) \
|
||||
X ( mjtNum, pair_gap, npair, 1 ) \
|
||||
X ( mjtNum, pair_adhesion, npair, 1 ) \
|
||||
X ( mjtNum, pair_friction, npair, 5 )
|
||||
|
||||
#define MJMODEL_POINTERS_EXCLUDE \
|
||||
@@ -911,6 +913,7 @@
|
||||
X ( mjtNum, qfrc_damper, nv, 1 ) \
|
||||
X ( mjtNum, qfrc_gravcomp, nv, 1 ) \
|
||||
X ( mjtNum, qfrc_fluid, nv, 1 ) \
|
||||
X ( mjtNum, qfrc_adhesion, nv, 1 ) \
|
||||
X ( mjtNum, qfrc_passive, nv, 1 ) \
|
||||
X ( mjtNum, subtree_linvel, nbody, 3 ) \
|
||||
X ( mjtNum, subtree_angmom, nbody, 3 ) \
|
||||
|
||||
Reference in New Issue
Block a user