Time tolerance

Definition of consecutive zero crossings

Model Configuration Pane: Solver

Description

The software defines zero crossings as consecutive if the time between events is smaller than an interval defined by the time tolerance. Consider a simulation in which the software detects zero crossings ZC₁ and ZC₂, bracketed at successive time steps t₁ and t₂.

The software considers the zero crossings consecutive when the interval dt between t₁ and t₂ is less than the product of the specified time tolerance timetol and the larger time t₂.

dt < timetol * t₂

The software counts the number of consecutive zero crossings detected and issues a diagnostic when the count exceeds the amount specified by the Number of consecutive zero crossings parameter. You can specify whether the diagnostic is a warning or an error using the Consecutive zero-crossings violation parameter. The counter resets when the simulation progresses without detecting another zero crossing long enough for the next zero crossing to be considered nonconsecutive.

Dependencies

To enable this parameter, set the solver Type to Variable-step and set Zero-crossing control to either Use local settings or Enable all.

Settings

10*128*eps | positive scalar number

Decreasing the time tolerance specifies a stricter definition for consecutive. A lower time tolerance can provide more flexibility for a model to recover from behaviors and conditions that result in many discontinuities.

Tips

For models that experience excessive zero crossings, consider increasing the value for the Number of consecutive zero crossings parameter to relax the condition for when the software issues a diagnostic about the number of detected zero crossings.

Recommended Settings

The table summarizes recommended values for this parameter based on considerations related to code generation.

Application	Setting
Debugging	No impact
Traceability	No impact
Efficiency	No impact
Safety precaution	No impact

Programmatic Use

Parameter: ConsecutiveZCsStepRelTol

Type: string | character vector

Value: positive scalar number

Default: '10*128*eps'

Version History

Introduced before R2006a