How do I have a time based function be the input for revolute joint position in Simulink

I am trying to model a motion in which I take data from the real world, regress it into a function and then use this function to drive a simulink model revolute joint for position. I then intend to use the model to do an inverse dynamics calculation of the joint torques that would be needed to create the specified motion.

What block do I use to just specify an input function to the joint as a function of time? I would like to be able to enter a polynomial equation with the regression coefficients.

Answer 1

[Fangjun Jiang]

The Clock block provides the time line that the simulation runs on. You can use that for your function.

[Dieter]

This is the error I get when I use a Matlab function and the clock block feeding it the simulation time:

C Caller block 'RightArm90ByPositionInputUserDefinedFunctionAddedRE/Right Elbow Joint/User-Defined Functions/C Caller' requires model to have associated importable custom code. There is no custom code specified, or 'Import custom code' is disabled.

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You may add custom code dependency to model 'simulink'Open

Enable 'Import custom code' for model 'simulink'

[Fangjun Jiang]

The error comes from a "C Caller" block, not a "MATLAB Function" block. For your need, I would think a "MATLAB Function" block is sufficient. Why use a "C Caller" block?

[Dieter]

Thanks. I did not know there was a difference. The blocks look identical when I search for Matlab function. Must have had the wrong one. Now its on to a different error about input derivatives, but at least I am past that sticking point.