Connections / Contact / Joints#

Module containing joint classes to connect multiple rods together.

Description#

Available Connection/Contact/Joints

FreeJoint

This free joint class is the base class for all joints.

ExternalContact

Assumes that the second entity is a rigid body for now, can be changed at a later time

FixedJoint

The fixed joint class restricts the relative movement and rotation between two nodes and elements by applying restoring forces and torques.

HingeJoint

This hinge joint class constrains the relative movement and rotation (only one axis defined by the user) between two nodes and elements (chosen by the user) by applying restoring forces and torques.

SelfContact

This class is modeling self contact of rod.

Compatibility#

Connection / Contact / Joints

Rod

Rigid Body

FreeJoint

✅

✅

ExternalContact

✅

❌

FixedJoint

✅

✅

HingeJoint

✅

❌

SelfContact

✅

❌

Built-in Connection / Contact / Joint#

class elastica.joint.FreeJoint(k, nu)[source]#

This free joint class is the base class for all joints. Free or spherical joints constrains the relative movement between two nodes (chosen by the user) by applying restoring forces. For implementation details, refer to Zhang et al. Nature Communications (2019).

Notes

Every new joint class must be derived from the FreeJoint class.

Attributes
k: float

Stiffness coefficient of the joint.

nu: float

Damping coefficient of the joint.

__init__(k, nu)[source]#
Parameters
k: float

Stiffness coefficient of the joint.

nu: float

Damping coefficient of the joint.

class elastica.joint.ExternalContact(k, nu)[source]#

Assumes that the second entity is a rigid body for now, can be changed at a later time

Most of the cylinder-cylinder contact SHOULD be implemented as given in this paper.

but, it isn’t (the elastica-cpp kernels are implented)! This is maybe to speed-up the kernel, but it’s potentially dangerous as it does not deal with “end” conditions correctly.

__init__(k, nu)[source]#
Parameters
k: float

Stiffness coefficient of the joint.

nu: float

Damping coefficient of the joint.

class elastica.joint.FixedJoint(k, nu, kt)[source]#

The fixed joint class restricts the relative movement and rotation between two nodes and elements by applying restoring forces and torques. For implementation details, refer to Zhang et al. Nature Communications (2019).

Attributes
k: float

Stiffness coefficient of the joint.

nu: float

Damping coefficient of the joint.

kt: float

Rotational stiffness coefficient of the joint.

__init__(k, nu, kt)[source]#
Parameters
k: float

Stiffness coefficient of the joint.

nu: float

Damping coefficient of the joint.

kt: float

Rotational stiffness coefficient of the joint.

class elastica.joint.HingeJoint(k, nu, kt, normal_direction)[source]#

This hinge joint class constrains the relative movement and rotation (only one axis defined by the user) between two nodes and elements (chosen by the user) by applying restoring forces and torques. For implementation details, refer to Zhang et. al. Nature Communications (2019).

Attributes
k: float

Stiffness coefficient of the joint.

nu: float

Damping coefficient of the joint.

kt: float

Rotational stiffness coefficient of the joint.

normal_direction: numpy.ndarray

2D (dim, 1) array containing data with ‘float’ type. Constraint rotation direction.

__init__(k, nu, kt, normal_direction)[source]#
Parameters
k: float

Stiffness coefficient of the joint.

nu: float

Damping coefficient of the joint.

kt: float

Rotational stiffness coefficient of the joint.

normal_direction: numpy.ndarray

2D (dim, 1) array containing data with ‘float’ type. Constraint rotation direction.

class elastica.joint.SelfContact(k, nu)[source]#

This class is modeling self contact of rod.

__init__(k, nu)[source]#
Parameters
k: float

Stiffness coefficient of the joint.

nu: float

Damping coefficient of the joint.