modelWeakSpherical
Extends from Modelica.Mechanics.MultiBody.Interfaces.PartialTwoFrames (Base model for components providing two frame connectors + outer world + assert to guarantee that the component is connected).
Information
Attribution Notice
This model is a modification of the Spherical block in the Mechanics.MultiBody.Joints package
of the Modelica Standard Library
Copyright © 1998-2016, Modelica Association and DLR.
Block for modeling a spherical joint with a weak constraint. Most Modelica joints introduce strong constraints, i.e. the position of the two frames must be exactly equal. In reality, such strong constraints can cause binding in systems with multiple joints and cause systems to have kinematic loops. This joint overcomes these problems by using a weak formulation of the joint constraints.
Rotational springs can be connected to add torsional stiffness to the joint.
One needs to pay attention and be careful with angle definitions when used in conjunction with rotational springs because phi is determined as a function of R_rel, therefore angle branching occurs at phi = pi and -pi.
Copyright © 2018
ATA ENGINEERING, INC.
ALL RIGHTS RESERVED
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | useAxisFlangeX | false | = true, if axis flange X is enabled |
| Boolean | useAxisFlangeY | false | = true, if axis flange Y is enabled |
| Boolean | useAxisFlangeZ | false | = true, if axis flange Z is enabled |
| SI.TranslationalSpringConstant | c_constraint | 1.0e7 | Spring constant |
| SI.TranslationalDampingConstant | d_constraint | 1.0 | Damping constant |
| Boolean | animation | false | = true, if animation shall be enabled (show sphere) |
| if animation = true | |||
| SI.Distance | sphereDiameter | world.defaultJointLength | Diameter of sphere representing the spherical joint |
| Advanced | |||
| Types.RotationSequence | sequence_angles | {1, 2, 3} | Sequence of rotations to rotate frame_a into frame_b around the 3 angles used as states |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Interfaces.Frame_a | frame_a (from PartialTwoFrames) | Coordinate system a fixed to the component with one cut-force and cut-torque | |
| Interfaces.Frame_b | frame_b (from PartialTwoFrames) | Coordinate system b fixed to the component with one cut-force and cut-torque | |
| Modelica.Mechanics.Rotational.Interfaces.Flange_a | axisX | 1-dim. rotational flange that drives the joint | |
| Modelica.Mechanics.Rotational.Interfaces.Flange_b | supportX | 1-dim. rotational flange of the drive support (assumed to be fixed in the world frame, NOT in the joint) | |
| Modelica.Mechanics.Rotational.Interfaces.Flange_b | supportZ | 1-dim. rotational flange of the drive support (assumed to be fixed in the world frame, NOT in the joint) | |
| Modelica.Mechanics.Rotational.Interfaces.Flange_a | axisZ | 1-dim. rotational flange that drives the joint | |
| Modelica.Mechanics.Rotational.Interfaces.Flange_a | axisY | 1-dim. rotational flange that drives the joint | |
| Modelica.Mechanics.Rotational.Interfaces.Flange_b | supportY | 1-dim. rotational flange of the drive support (assumed to be fixed in the world frame, NOT in the joint) |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Types.Color | sphereColor | Modelica.Mechanics.MultiBody.Types.Defaults.JointColor | Color of sphere representing the spherical joint |
| Types.SpecularCoefficient | specularCoefficient | world.defaultSpecularCoefficient | Reflection of ambient light (= 0: light is completely absorbed) |
| SI.Position | r_rel_a | Position vector from frame_a to frame_b resolved in world frame | |
| SI.Position | v_rel_a | ||
| SI.Angle | phi | Three angles to rotate frame_a into frame_b | |
| Frames.Orientation | R_rel | Relative orientation object to rotate from frame_a to frame_b | |
| SI.Torque | tau | Driving torque in direction of axis of rotation |