Internal Force

General force acting reciprocally between two frame origins


Forces and Torques


This block represents a general force pair acting reciprocally between base and follower frame origins. The two forces in the pair have equal magnitude but opposite directions. One force acts on the base frame origin, along the vector connecting follower to base frame origins. The other force acts on the follower frame origin, along the vector connecting base to follower frame origins.

To specify the internal force, the block provides physical signal port fm. A positive input signal represents a repulsive force, which pushes base and follower frame origins apart. A negative input signal represents an attractive force, which pulls base and follower frame origins together. If at any time the two frame origins are coincident, the internal force direction becomes undefined and Simscape™ Multibody™ might stop with an error.

C/C++ Code Generation

This block supports code generation for real-time simulation tasks. Certain blocks and block settings may be more suitable for simulation on a real-time device. For suggestions on how to improve real-time simulation performance, use the Simulink® Performance Advisor (Simulink). Suggestions include ways to reduce model complexity where helpful and to decrease numerical stiffness.

Select Analysis > Performance Tools > Performance Advisor in the Simulink menu bar to open the Performance Advisor. Set the Activity parameter to Execute real-time application to view suggestions specific to real-time simulation performance. Expand the Real-Time node in the tree view pane to select performance checks specific to Simscape products.


This block contains frame ports B and F, representing base and follower port frames, respectively. A physical signal port, fm, provides the means to specify the internal force acting between the two port frames.

Introduced in R2013a

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