Globally stable control of linear systems with input saturation subject to
L-2 disturbances is analysed. The well known results on disturbance-free sy
stems are that nonlinear controls can ensure global stability, while linear
time-invariant controls can only achieve semiglobal stabilisation. A linea
r control with a tuning parameter is proposed to achieve global stability o
f the systems even when they are subject to arbitrary L-2 disturbances. The
parameter is automatically tuned using a switch rule based on state measur
ement. The advantage over the existing algorithms is that no online solutio
n of algebraic Riccati equations is needed. Control design of an armature-c
ontrolled DC servomotor is used to demonstrate the proposed algorithm, and
simulation results are shown.