Source code for elastica.modules.forcing

__doc__ = """

Provides the forcing interface to apply forces and torques to rod-like objects
(external point force, muscle torques, etc).
from elastica.interaction import AnisotropicFrictionalPlane

[docs]class Forcing: """ The Forcing class is a module for applying boundary conditions that consist of applied external forces. To apply forcing on rod-like objects, the simulator class must be derived from the Forcing class. Attributes ---------- _ext_forces_torques: list List of forcing class defined for rod-like objects. """ def __init__(self): self._ext_forces_torques = [] super(Forcing, self).__init__() self._feature_group_synchronize.append(self._call_ext_forces_torques) self._feature_group_finalize.append(self._finalize_forcing)
[docs] def add_forcing_to(self, system): """ This method applies external forces and torques on the relevant user-defined system or rod-like object. You must input the system or rod-like object that you want to apply external forces and torques on. Parameters ---------- system: object System is a rod-like object. Returns ------- """ sys_idx = self._get_sys_idx_if_valid(system) # Create _Constraint object, cache it and return to user _ext_force_torque = _ExtForceTorque(sys_idx) self._ext_forces_torques.append(_ext_force_torque) return _ext_force_torque
def _finalize_forcing(self): # From stored _ExtForceTorque objects, and instantiate a Force # inplace : # dev : the first index stores the rod index to apply the boundary condition # to. Technically we can use another array but it its one more book-keeping # step. Being lazy, I put them both in the same array self._ext_forces_torques[:] = [ (, ext_force_torque()) for ext_force_torque in self._ext_forces_torques ] # Sort from lowest id to highest id for potentially better memory access # _ext_forces_torques contains list of tuples. First element of tuple is # rod number and following elements are the type of boundary condition such as # [(0, NoForces, GravityForces), (1, UniformTorques), ... ] # Thus using lambda we iterate over the list of tuples and use rod number (x[0]) # to sort _ext_forces_torques. self._ext_forces_torques.sort(key=lambda x: x[0]) # Find if there are any friction plane forcing, if add them to the end of the list, # since friction planes uses external forces. friction_plane_index = [] for idx, ext_force_torque in enumerate(self._ext_forces_torques): if isinstance(ext_force_torque[1], AnisotropicFrictionalPlane): friction_plane_index.append(idx) # Move to the friction forces to the end of the external force and torques list. for index in friction_plane_index: self._ext_forces_torques.append(self._ext_forces_torques.pop(index)) def _call_ext_forces_torques(self, time, *args, **kwargs): for sys_id, ext_force_torque in self._ext_forces_torques: ext_force_torque.apply_forces(self._systems[sys_id], time, *args, **kwargs) ext_force_torque.apply_torques(self._systems[sys_id], time, *args, **kwargs)
# TODO Apply torque, see if necessary class _ExtForceTorque: """ Forcing module private class Attributes ---------- _sys_idx: int _forcing_cls: list *args Variable length argument list. **kwargs Arbitrary keyword arguments. """ def __init__(self, sys_idx: int): """ Parameters ---------- sys_idx: int """ self._sys_idx = sys_idx self._forcing_cls = None self._args = () self._kwargs = {} def using(self, forcing_cls, *args, **kwargs): """ This method is a module to set which forcing class is used to apply forcing to user defined rod-like objects. Parameters ---------- forcing_cls: object User defined forcing class. *args Variable length argument list **kwargs Arbitrary keyword arguments. Returns ------- """ from elastica.external_forces import NoForces assert issubclass( forcing_cls, NoForces ), "{} is not a valid forcing. Did you forget to derive from NoForces?".format( forcing_cls ) self._forcing_cls = forcing_cls self._args = args self._kwargs = kwargs return self def id(self): return self._sys_idx def __call__(self, *args, **kwargs): """Constructs a constraint after checks Parameters ---------- *args Variable length argument list. **kwargs Arbitrary keyword arguments. Returns ------- """ if not self._forcing_cls: raise RuntimeError( "No forcing provided to act on rod id {0}" "but a force was registered. Did you forget to call" "the `using` method".format( ) try: return self._forcing_cls(*self._args, **self._kwargs) except (TypeError, IndexError): raise TypeError( r"Unable to construct forcing class.\n" r"Did you provide all necessary force properties?" )