Composite Nonlinear Feedback Control Toolkit

Guoyang Cheng, Ben M. Chen, Kemao Peng, Tong H. Lee

The CNF Control Toolkit is developed under MATLAB (6.5 and above) with SIMULINK. It fully utilizes the GUI resources of MATLAB and provides a user-friendly graphical interface. It can be utilized to design a fast and smooth tracking controller for a class of linear and nonlinear systems with actuator and other nonlinearities as well as with external disturbances. The composite nonlinear feedback control for general SISO linear systems without disturbances and with disturbances introduced recently in the literature consists of a linear feedback law and a nonlinear feedback law. A more complete treatment of the subject can be found in the 2nd Edition of a Springer monograph, Hard Disk Drive Servo Systems. The linear feedback part is designed to yield a closed-loop system with a small damping ratio for a quick response, while the nonlinear feedback part is used to increase the damping ratio of the closed-loop system as the system output approaches the target reference to reduce the overshoot caused by the linear part. A nonlinearity pre-compensation will be implemented if there are plant nonlinearities that can be canceled using certain output feedback. If the given plant is noisy and/or has high frequency resonance modes, a low-pass or a notch filter can also be added to yield a good performance. An integrator can also be added to the overall controller design if there are external disturbances. The toolkit is capable of displaying both time-domain and frequency-domain responses on its main panel, and generating three different types of control laws, namely, the state feedback, the full order measurement feedback and the reduced order measurement feedback controllers.

The main interface of the toolkit consists of three panels:

The detailed description on the usage of the toolkit together with few sample design examples including two benchmark problems (one on an RTAC nonlinear system and the other on an HDD servo system). Interested readers might register your contact information below:

Interested readers please send us an email with (1) your name; (2) email address; (3) institution; and (4) country. A zipped file,, containing all the m-functions of the toolkit will be sent to your email address. Please note that we might verify your information first before sending out the package to you. Once again, note that your information will be added to our database for distribution of future versions.

The toolkit is free for use in research work only. Any commercial utilization of the package without the owners' permission is strictly prohibited.