Composite Nonlinear Feedback Control Law Research Articles

A Hard-Disk-Drive Servo System Design Using Composite Nonlinear-Feedback Control With Optimal Nonlinear Gain Tuning Methods

This paper investigates the design of composite nonlinear-feedback (CNF) control law for a hard-disk-drive (HDD) servo system. First, a scaled nonlinear function is introduced for the CNF control law, in which a parameter is scaled by the error between the amplitude of the target reference and the initial value of the system controlled output. The closed-loop system under the scaled function has robust transient performance to the variation of the amplitude of the target reference. Then, the parameters of the selected nonlinear function are tuned by optimal tuning methods. More specifically, the parameter-tuning problem is formulated as an optimization problem, which can be solved efficiently via numerical methods. The simulation and experimental results show that the control law designed using the new approach yields excellent performance for both track seeking and track following in the HDD servo system.

Improving Transient Performance in Tracking General References Using Composite Nonlinear Feedback Control and Its Application to High-Speed $XY$-Table Positioning Mechanism

We adopt in this paper the newly developed composite nonlinear feedback (CNF) control method to track general target references for systems with input saturation. The original formulation of the CNF control technique is only applicable to set-point tracking, in which the target reference is set to be a constant. In this paper, a reference generator, which is able to produce more general reference signals such as sinusoidal and other waves, will be proposed to supplement the CNF control technique to yield a good performance. The resulting control law comprises the reference generator and a modified CNF control law, which is proven to be capable of tracking a target reference with fast settling time and minimal overshoot. Simulation and experimental results on an XY-table show that the proposed technique gives a very satisfactory performance

Improving transient performance in tracking control for linear multivariable discrete-time systems with input saturation

In this paper, we present a composite nonlinear feedback (CNF) control technique for linear discrete-time multivariable systems with actuator saturation. The CNF control law serves to improve the transient performance of the closed-loop system by adding an additional nonlinear feedback. The linear feedback can be designed to yield a quick response at the initial stage, then the nonlinear feedback is introduced to smooth out overshoots when the system output approaches the target reference. As such, the resulting closed-loop system typically has very fast transient response and small overshoots. The goal of this work is to complete the theory for general discrete-time systems. The technique is applied to a magnetic-tape-drive servo system design and yields a huge improvement in settling time compared to that of a purely linear controller.

On improvement of transient performance in tracking control for a class of nonlinear systems with input saturation

This paper studies the technique of the composite nonlinear feedback (CNF) control for a class of cascade nonlinear systems with input saturation. The objective of this paper is to improve the transient performance of the closed-loop system by designing a CNF control law such that the output of the system tracks a step input rapidly with small overshoot and at the same time maintains the stability of the whole cascade system. The CNF control law consists of a linear feedback control law and a nonlinear feedback control law. The linear feedback law is designed to yield a closed-loop system with a small damping ratio for a quick response, while the nonlinear feedback law is used to increase the damping ratio of the closed-loop system when the system output approaches the target reference to reduce the overshoot. The result has been successfully demonstrated by numerical and application examples including a flight control system for a fighter aircraft.

COMPOSITE NONLINEAR FEEDBACK CONTROL FOR A CLASS OF NONLINEAR SYSTEMS WITH INPUT SATURATION

This paper studies the technique of the composite nonlinear feedback (CNF) control for a class of cascade nonlinear systems with input saturation. In particular, the class of systems under consideration consists of two parts, a linear portion and a nonlinear portion with the output of the linear part connecting to the input of the nonlinear part and with the input of the given system being saturated. The objective of this paper is to design a composite nonlinear feedback control law based on the linear portion such that the output of the system tracks a step input rapidly with small overshoot and at the same time maintains the stability of the whole cascade system. The result has been successfully demonstrated by a numerical example.