Simulink Control Design™ - MathWorks

(^1) Respond to step changes in boost pressure and EGR massflow in about 5 seconds
with minimum cross-coupling
(^2) Be insensitive to (small) variations in speed and fuel mass.
Use a tracking requirement for the first objective. Specify the amplitudes of the step
changes to ensure that cross-couplings are small relative to these changes.
% 5-second response time, steady-state error less than 5%
TR = TuningGoal.Tracking({'BOOST REF';'EGRMF REF'},{'BOOST';'EGRMF'},5,0.05);
TR.Name = 'Setpoint tracking';
TR.InputScaling = [10 3];
For the second objective, treat the speed and fuel mass variations as step disturbances
and specify the peak amplitude and settling time of the resulting variations in boost
pressure and EGR massflow. Also specify the signal amplitudes to properly reflect the
relative contribution of each disturbance.
% Peak<0.5, settling time<5
DR = TuningGoal.StepRejection({'FUELMASS';'SPEED'},{'BOOST';'EGRMF'},0.5,5);
DR.Name = 'Disturbance rejection';
DR.InputScaling = [5 200];
DR.OutputScaling = [10 3];
To provide adequate robustness to unmodeled dynamics and aliasing, limit the control
bandwidth and impose sufficient stability margins at both the plant inputs and outputs.
Because we are dealing with a 2-by-2 MIMO feedback loops, these stability margins are
interpreted as disk margins (see diskmargin and TuningGoal.Margins for details).
% Roll off of -20 dB/dec past 1 rad/s
RO = TuningGoal.MaxLoopGain({'EGRLIFT','VGTPOS'},1,1);
RO.LoopScaling = 'off';
RO.Name = 'Roll-off';
% 7 dB of gain margin and 45 degrees of phase margin
M1 = TuningGoal.Margins({'EGRLIFT','VGTPOS'},7,45);
M1.Name = 'Plant input';
M2 = TuningGoal.Margins('DIESEL ENGINE',7,45);
M2.Name = 'Plant output';
Tuning of Blackbox MIMO Controller
Without a-priori knowledge of a suitable control structure, first try "blackbox" state-space
controllers of various orders. The plant model has four states, so try a controller of order
13 Control System Tuning Examples