Simulink Control Design™ - MathWorks

Refining The Design

To improve the Bicep response for this specific arm maneuver, we must keep the cross-

couplings effects small relative to the final angular displacements in each joint. To do this,

scale the cross-coupling terms in the step tracking requirement by the reference angle

amplitudes.

JointDisp = [60 10 60 90 90 60]; % commanded angular displacements, in degrees

TR.InputScaling = JointDisp;

To reduce saturation of the actuators, limit the gain from reference signals to control

signals.

UR = TuningGoal.Gain(RefSignals,Controls,6);

Retune the controller with these refined tuning goals.

ST3 = looptune(ST0,Controls,Measurements,TR,UR);

Final: Peak gain = 1.14, Iterations = 200

Compare the scaled responses with the previous design. Notice the significant reduction

of the coupling between Wrist and Bicep motion, both in peak value and total energy.

T2s = diag(1./JointDisp) * T2 * diag(JointDisp);

T3s = diag(1./JointDisp) * getIOTransfer(ST3,RefSignals,Measurements) * diag(JointDisp);

stepplot(T2s,'g--',T3s,'m',4,opt)

legend('Initial 2-DOF','Refined 2-DOF','location','SouthEast')

13 Control System Tuning Examples