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chgTimeUnit - Change time units of dynamic system

Syntax

sys_new = chgTimeUnit(sys,newtimeunits)

Description

sys_new = chgTimeUnit(sys,newtimeunits) changes the time units of sys to newtimeunits. The time- and frequency-domain characteristics of sys and sys_new match.

Tips

Input Arguments

sys

Dynamic system model

newtimeunits

New time units, specified as one of the following strings:

  • 'nanoseconds'

  • 'microseconds'

  • 'milliseconds'

  • 'seconds'

  • 'minutes'

  • 'hours'

  • 'days'

  • 'weeks'

  • 'months'

  • 'years'

Default: 'seconds'

Output Arguments

sys_new

Dynamic system model of the same type as sys with new time units. The time response of sys_new is same as sys.

If sys is an identified linear model, both the model parameters as and their minimum and maximum bounds are scaled to the new time units.

Examples

This example shows how to change the time units of a transfer function model.

  1. Create a transfer function model.

    num = [4 2];
den = [1 3 10];
sys = tf(num,den);

    The default time units of sys is seconds.

  2. Change the time units.

    sys1 = chgTimeUnit(sys,'minutes');

    The TimeUnit property of sys1 is milliseconds.

  3. Compare the step responses of sys and sys1.

    step(sys,'r',sys1,'y--');
legend('sys','sys1');

    The step responses of sys and sys1 match.

  4. (Optional) Change the TimeUnit property of sys, and compare the step response with the original system.

    sys2=sys;
sys2.TimeUnit = 'minutes';
step(sys,'r', sys2,'gx'); 
legend('sys','sys2');

    Changing the TimeUnit property changes the original system. Therefore, the step responses of sys and sys2 do not match. For example, the original rise time of 0.04 seconds changes to 0.04 minutes.

See Also

chgFreqUnit | frd | pid | ss | tf | zpk

Tutorials

  

 

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