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How can I use a constant time step for certain subsystems inside a variable time step simulation

Asked by Jeff Hough on 10 Jan 2019
Latest activity Answered by Steve Miller on 2 Apr 2019
Hello!
I am simulating a controlled robot arm with several degrees of freedom. The arm appears to behave as a stiff differential equation, so I want to use ODE 15s as the solver for the simulation. However, since the control law being tested will eventually be implemented on a microcomputer with a fixed timestep, I would like to still be able to run the control block at a fixed frequency (say, at 100Hz).
Is this possible to do? Thanks in advance!
Jeff

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1 Answer

Answer by Steve Miller on 2 Apr 2019

You can configure the model such that the portion of your model representing the algorithm on the microcontroller is evaluated at 100Hz if you use discrete blocks (and/or Rate Transition blocks) and set the sample time accordingly. Your Simscape Multibody model will be evaluated using ode15s. It will update at a minimum rate of 100Hz (max step size of 0.01), as it cannot take steps larger than the sample time of your controller.
--Steve

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