modelPartialLineForce
Base model for massless line force elements
Extends from LineForceBase (Base model for line force elements).
Information
All massless line force elements should be based on this base model. This model defines frame_a and frame_b, computes the (guarded) relative distance s and provides the force and torque balance of the cut-forces and cut-torques at frame_a and frame_b, respectively. In sub-models, only the line force f, acting at frame_b on the line from frame_a to frame_b, as a function of the relative distance s and its derivative der(s) has to be defined. Example:
model Spring parameter Real c "spring constant", parameter Real s_unstretched "unstretched spring length"; extends Modelica.Mechanics.MultiBody.Interfaces.PartialLineForce; equation f = c*(s-s_unstretched); end Spring;
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Advanced | |||
| SI.Distance | s_small (from LineForceBase) | 1e-10 | Prevent zero-division if distance between frame_a and frame_b is zero |
| Advanced › If enabled, can give wrong results, see MultiBody.UsersGuide.Tutorial.ConnectionOfLineForces | |||
| Boolean | fixedRotationAtFrame_a (from LineForceBase) | false | = true, if rotation frame_a.R is fixed (to directly connect line forces) |
| Boolean | fixedRotationAtFrame_b (from LineForceBase) | false | = true, if rotation frame_b.R is fixed (to directly connect line forces) |
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 |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| SI.Distance | length (from LineForceBase) | Distance between the origin of frame_a and the origin of frame_b | |
| SI.Position | s (from LineForceBase) | (Guarded) distance between the origin of frame_a and the origin of frame_b (>= s_small)) | |
| SI.Position[3] | r_rel_0 (from LineForceBase) | Position vector from frame_a to frame_b resolved in world frame | |
| Real[3] | e_rel_0 (from LineForceBase) | Unit vector in direction from frame_a to frame_b, resolved in world frame | |
| SI.Position[3] | r_rel_a | Position vector from origin of frame_a to origin of frame_b, resolved in frame_a | |
| Real[3] | e_a | Unit vector on the line connecting the origin of frame_a with the origin of frame_b resolved in frame_a (directed from frame_a to frame_b) | |
| SI.Force | f | Line force acting on frame_a and on frame_b (positive, if acting on frame_b and directed from frame_a to frame_b) |