TITLE:
Anti-Windup Digital Control Design for Time-Delayed Analog Nonlinear Systems Using Approximated Scalar Sign Function
AUTHORS:
Warsame H. Ali, Yongpeng Zhang, Jian Zhang, John H. Fuller, Leang-San Shieh
KEYWORDS:
Anti-Windup Control; Scalar Sign Function; Sampled-Data System; Time-Delayed System
JOURNAL NAME:
Circuits and Systems,
Vol.5 No.1,
January
16,
2014
ABSTRACT: This paper describes an
approximated-scalar-sign-function-based anti-windup digital control design for
analog nonlinear systems subject to input constraints. As input saturation
occurs, the non-smooth saturation constraint is modeled with the approximated
scalar sign function which is a smooth nonlinear function. The resulting nonlinear
model is further linearized at any operating point with the optimal
linearization technique, and Linear Quadratic Regulator (LQR) is then applied
for a state-feedback controller optimal for each operating point. As input
saturation is encountered, an iterative procedure is developed to adjust
control gains by systematically updating LQR weighting matrices until the inputs
lie within the saturation limits. Through global digital redesign,
the analog LQR controller is converted to an equivalent digital one for keeping
the essential control performance, and moreover, delay compensation is
taken into account during digital redesign for compensating the potential time
delays in a control loop. The swing-up and stabilization control of single
rotary inverted pendulum system is used to illustrate and verify the proposed
method.