Specify the reference system for the desired step response as a dynamic system
model, such as a tf, zpk, or ss model.Enter the name of the reference model in the MATLAB workspace in the LTI model to
match text field. Alternatively, enter a command to create a suitable reference model,
such as tf(1,[1 1.414 1]).The reference model must be stable and must have DC gain of 1 (zero steady-state
error). The model can be continuous or discrete. If the model is discrete, it can include
time delays which are treated as poles at z = 0.The reference model can be MIMO, provided that it is square and that its DC singular
value (sigma) is 1. Then number of inputs and outputs of the reference model must
match the dimensions of the inputs and outputs specified for the step response goal.For best results, the reference model should also include intrinsic system
characteristics such as non-minimum-phase zeros (undershoot).If your selected inputs and outputs define a MIMO system and you apply a SISO reference
system, the software attempts to match the diagonal channels of the MIMO system. In
that case, cross-couplings tend to be minimized.
Options
Use this section of the dialog box to specify additional characteristics of the step response
goal.
- Keep % mismatch below
Specify the relative matching error between the actual (tuned) step response and the
target step response. Increase this value to loosen the matching tolerance. The
relative matching error, erel, is defined as:erel=yt−yreft 2
1 −yreft 2.
y(t) – yref(t) is the response mismatch, and 1 – yref(t) is the step-tracking error of the
target model. ⋅ 2 denotes the signal energy (2-norm).- Adjust for step amplitude
For a MIMO tuning goal, when the choice of units results in a mix of small and large
signals in different channels of the response, this option allows you to specify theStep Tracking Goal