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 SimMechanics™ might stop with an error.

Dialog Box and Parameters


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.

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