The physics tag specifies the type and properties of the dynamics engine. The type of the dynamics engine. Current options are ode, bullet, simbody and rtql8. Defaults to ode if left unspecified. Maximum time step size at which every system in simulation can interact with the states of the world. (was physics.sdf's dt). target simulation speedup factor, defined by ratio of simulation time to real-time. Rate at which to update the physics engine (UpdatePhysics calls per real-time second). (was physics.sdf's update_rate). Maximum number of contacts allowed between two entities. This value can be over ridden by a max_contacts element in a collision element. The gravity vector Simbody specific physics properties (Currently not used in simbody) The time duration which advances with each iteration of the dynamics engine, this has to be no bigger than max_step_size under physics block. If left unspecified, min_step_size defaults to max_step_size. Roughly the relative error of the system. -LOG(accuracy) is roughly the number of significant digits. Tolerable "slip" velocity allowed by the solver when static friction is supposed to hold object in place. vc Assume real COR=1 when v=0. e_min = given minimum COR, at v >= vp (a.k.a. plastic_coef_restitution) d = slope = (1-e_min)/vp OR, e_min = 1 - d*vp e_max = maximum COR = 1-d*vc, reached at v=vc e = 0, v <= vc = 1 - d*v, vc < v < vp = e_min, v >= vp dissipation factor = d*min(v,vp) [compliant] cor = e [rigid] Combining rule e = 0, e1==e2==0 = 2*e1*e2/(e1+e2), otherwise]]> Default contact material stiffness (force/dist or torque/radian). dissipation coefficient to be used in compliant contact; if not given it is (1-min_cor)/plastic_impact_velocity this is the COR to be used at high velocities for rigid impacts; if not given it is 1 - dissipation*plastic_impact_velocity smallest impact velocity at which min COR is reached; set to zero if you want the min COR always to be used static friction (mu_s) as described by this plot: http://gazebosim.org/wiki/File:Stribeck_friction.png dynamic friction (mu_d) as described by this plot: http://gazebosim.org/wiki/File:Stribeck_friction.png viscous friction (mu_v) with units of (1/velocity) as described by this plot: http://gazebosim.org/wiki/File:Stribeck_friction.png for rigid impacts only, impact velocity at which COR is set to zero; normally inherited from global default but can be overridden here. Combining rule: use larger velocity This is the largest slip velocity at which we'll consider a transition to stiction. Normally inherited from a global default setting. For a continuous friction model this is the velocity at which the max static friction force is reached. Combining rule: use larger velocity Bullet specific physics properties One of the following types: sequential_impulse only. The time duration which advances with each iteration of the dynamics engine, this has to be no bigger than max_step_size under physics block. If left unspecified, min_step_size defaults to max_step_size. Number of iterations for each step. A higher number produces greater accuracy at a performance cost. Set the successive over-relaxation parameter. Bullet constraint parameters. Constraint force mixing parameter. See the ODE page for more information. Error reduction parameter. See the ODE page for more information. The depth of the surface layer around all geometry objects. Contacts are allowed to sink into the surface layer up to the given depth before coming to rest. The default value is zero. Increasing this to some small value (e.g. 0.001) can help prevent jittering problems due to contacts being repeatedly made and broken. Similar to ODE's max_vel implementation. See http://web.archive.org/web/20120430155635/http://bulletphysics.org/mediawiki-1.5.8/index.php/BtContactSolverInfo#Split_Impulse for more information. Similar to ODE's max_vel implementation. See http://web.archive.org/web/20120430155635/http://bulletphysics.org/mediawiki-1.5.8/index.php/BtContactSolverInfo#Split_Impulse for more information. ODE specific physics properties One of the following types: world, quick The time duration which advances with each iteration of the dynamics engine, this has to be no bigger than max_step_size under physics block. If left unspecified, min_step_size defaults to max_step_size. Number of iterations for each step. A higher number produces greater accuracy at a performance cost. Experimental parameter. Set the successive over-relaxation parameter. Flag to enable dynamic rescaling of moment of inertia in constrained directions. See gazebo pull request 1114 for the implementation of this feature. https://bitbucket.org/osrf/gazebo/pull-request/1114 ODE constraint parameters. Constraint force mixing parameter. See the ODE page for more information. Error reduction parameter. See the ODE page for more information. The maximum correcting velocities allowed when resolving contacts. The depth of the surface layer around all geometry objects. Contacts are allowed to sink into the surface layer up to the given depth before coming to rest. The default value is zero. Increasing this to some small value (e.g. 0.001) can help prevent jittering problems due to contacts being repeatedly made and broken.