User`s guide

LQG Regulation
9-35
Start with the -axis. First specify the model components as transfer function
objects .
% Hydraulic actuator (with input "u-x")
Hx = tf(2.4e8,[1 72 90^2],'inputname','u-x')
% Input thickness/hardness disturbance model
Fix = tf(1e4,[1 0.05],'inputn','w-ix')
% Rolling eccentricity model
Fex = tf([3e4 0],[1 0.125 6^2],'inputn','w-ex')
% Gain from force to thickness gap
gx = 1e–6;
Next build the open-loop model shown in Figure 9-1 above. You could use the
function
connect for this purpose, but it is easier to build this model by
elementary
append and series connections.
% I/O map from inputs to forces f1 and f2
Px = append([ss(Hx) Fex],Fix)
% Add static gain from f1,f2 to outputs ”x-gap” and ”x-force”
Px = [–gx gx;1 1] * Px
% Give names to the outputs:
set(Px,'outputn',{'x-gap' 'x-force'})
Note: To obtain minimal state-space realizations, always convert transfer
function models to state space before connecting them. Combining transfer
functions and then converting to state space may produce nonminimal
state-space models.
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