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The Solver: Zero-Crossing Options
A variable-step solver dynamically
adjusts the time step
size, causing it to increase when a variable is changing
slowly and to decrease when the variable changes rapidly.
This behaviour causes the solver to take many
small steps
in near a discontinuity because the variable is rapidly
changing in this region. This improves accuracy but can
lead to excessive simulation times.
Simulink uses a technique known as zero-crossing
detection to accurately locate a discontinuity without
resorting to tiny time steps. Usually this technique
improves simulation
run time, but it can cause some
simulations to halt before the intended completion time. Understanding how Simulink’s zero-
crossing detection
algorithms, adaptive and non-adaptive, work is beyond the scope of the course.
The table below should help you overcome some errors associated with zero-crossing, particularly
a halting model. Implementing most of the changes, involves using the
Model Configuration Parameters dialog (MCP) box, accessed via the Cog symbol.
Possible Change...
How to make this change...
Rationale for making this change...
Increase the number
of allowed zero
crossings
Increase the
Number of consecutive
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