Spring FB

Use a Spring FB to apply a force between two Points. The term we use for those Points is Anchor-Points.


See also:

Add Spring FB

Machine Settings > Engineering Units

Configure Power Source


Spring-Force dialog-box

Spring-Foce FB dialog-box

Spring Parameters 

Dialog-FB-SpringForce-SprPara

 

Check-box to enable the Spring FB.

Spring-Rate:

Spring-Force / linear unit difference [SI: N/mm] that the Anchor-Points deviate from the Free-Length. [see Force Units and Linear Units].


Free-Length:

Is the natural-length of the Spring, as it would be if it were not joined to the Anchor-Points.

If the distance between Anchor-Points > Free-Length, then the Force-Vector [due to the Spring-Rate only] will Pull Anchor-Points together [o>>>|<<<o]

If the distance between Anchor-Points < Free-Length, then the Force-Vector [due to the Spring-Rate only] will Push Anchor-Points apart [o<<<|>>>o]

If the distance between Anchor-Points = Free-Length, then the Force-Vector [due to the Spring-Rate only] = 0


Constant-Force:

A positive force will PULL Anchor-Points together [o>>> + <<<o]

A negative force will PUSH Anchor-Points apart [o<<< — >>>o]

Velocity Parameters 

Dialog-FB-SpringForce-VelPara

 

Coulomb Friction Force: [Ff = μ.Fn ]
A Constant Force that is opposite to the direction of the motion.

This parameter is intended to be similar to a Friction Force. However, it is NOT exactly Friction Force, because this force is not a function of the 'Normal Force'.

Note: Friction Force is not a Kinetostatic Force.


Viscous Coefficient: [Fv α V [ N/(mm/s) ]

A Force that is proportional to the relative velocity between the Points.
The Force is opposite to the direction of motion.

E.g.: If the Damping Coefficient = 4 and the Velocity is +100mm/s, [anchor points moving away from each other’], then force pulling the points together is a force of 400N.


Drag Factor: [Fd α V2] [ N/((mm/s)2 ) ]

A Force that is proportional to square of the relative velocity between the Points. For example, air resistance.

The Force is opposite to the direction of motion.

E.g. If the Drag Factor = 4, and the Velocity = +100mm/s [anchor-points moving away from each other’], then force pulling the points together is a force of 40000N.


Input-Connector and Output-Connectors

Note:

It is not necessary to connect a wire to the input-connector or from its output-connectors. The connectors provide extra functionality and extra information.

Input-Connector

Use the input-connector to apply a bespoke force-function between the Spring's Anchor-Points. The force-function might be designed as a 'motion', for example. The data at the output of a Motion FB has dimensional units, typically mm or degrees. The data at the input-connector of the Spring FB must have units of Force units [N].

You must use a Maths FB to convert any data-type to units of Force, so that you can connect it to the input-connector of the Spring FB.

Note 1:

Units inside the Maths FB become SI units. To convert 100mm at the input to a Maths FB to 100N, you must:

1.Change the Output Data Type to Force [N]

AND

2.Multiply the input-value by 1000 to convert 0.1m to 100N

Note: To be consistent with the 'Constant-Force' Parameter

A positive force at the input will tend to PULL Anchor-Points together [o>>> + <<<o]

A negative force at the input will tend to PUSH Anchor-Points apart [o<<< — >>>o]


TOP output-connector

Dimension, Velocity and Acceleration relating to the distance between the Spring's anchor-points.


Bottom output-connector

Total Applied-Force between the Spring's anchor-points.

oTotal Applied-Force = Force at the Input-connector + Force that results from the parameters as set in the Spring FB dialog-box

or

oDriving-Force = Linear Motive Force, if you configure the Spring FB as a Linear Motor - see Configure Power Source

Tutorials and Reference Help Files for MechDesigner and MotionDesigner 14.2 + © Machine, Cam, Mechanism, and Motion Design Software by PSMotion Ltd