Biomedical subjects

KK Tan

Publications and source records attributed to KK Tan.

3 recordsLinked to original sources

PubMed2000

Simultaneous online automatic tuning of cascade control for open loop stable processes

In this paper, we present a new simultaneous online automatic tuning method for cascade control using a relay feedback approach. Departing from the traditional approach towards tuning of cascade control systems where the secondary and primary loops are tuned in strict sequence, the proposed approach is to carry out the entire tuning process in one experiment. For ease of practical applications, the entire procedure of controller design may be automated and carried out online. A direct controller tuning approach to tune the controllers is proposed here. Robustness analysis of the new cascade control design is further carried out in the paper by drawing on existing results for SISO feedback systems. Simulations are provided to illustrate the applicability and effectiveness of both the online autotuning approach and the new cascade control design.

Journal Article↗

PubMed2000

Development of a GPC-based PID controller for unstable systems with deadtime

Till now, traditional low-order control schemes have never been applicable to unstable systems with deadtime. In this paper, we present the first application of a PID controller with time-scheduled gains to unstable systems with deadtime, consisting of a single unstable pole. The control gains are designed based on a generalised predictive control (GPC) approach. The only user specifications required are simple and classical desired properties as in the natural frequency and the damping ratio of the closed-loop system. An approach is further developed to subsequent on-line self-tuning of control weights so that the overall control system remains applicable and effective in the face of disturbances and slowly varying dynamics. A detailed analysis of the closed-loop stability of the thus designed control system is further provided in the paper. Based on stability conditions developed, the prediction horizon for the GPC-based controller may be effectively computed. Finally, simulation examples illustrate the performance of the control system.

Journal Article↗

PubMed2000

Robust on-line relay automatic tuning of PID control systems

In this paper, a robust on-line relay automatic tuning method for PID control systems is developed which expand on the application domain of Astrom's renowned relay autotuning method. In the proposed configuration, a relay is applied to an inner loop of a controller-stabilised process in the usual manner. Using the induced limit cycle oscillations from the closed-loop system, the controller settings may be re-tuned non-iteratively to achieve enhanced performance without disrupting closed-loop control. Two control tuning methodologies are developed -- a direct and an indirect method based on an explicit process model. Simulation examples and a real-time experiment are provided to illustrate the practical appeal and potential advantages of the proposed method over the basic one.

Journal Article↗