Predictor-Based Output Feedback Control of Tumour Growth With Positive Input: Application to Antiangiogenic Therapy.

Controlling tumour growth systems presents significant challenges due to the inherent restriction of positive input in biological systems, along with delays in system output and input measurements. Traditional control methods struggle to address these issues effectively, as they rely heavily on real-time feedback from system outputs. The delays in output measurements can lead to instability in closed-loop systems, whereas the inability of conventional approaches to manage the positive input constraint often results in ineffective control. In this study, the authors propose a novel control system designed to overcome these challenges. First, a system state prediction observer that utilises delayed output measurements was developed. Next, a backstepping technique was utilized to develop a feedback controller that ensures the control input stays positive, thereby guaranteeing the system's asymptotic stability. Furthermore, numerical comparisons with previous research validate the effectiveness of the proposed strategy. Overall, the approach offers a promising solution to the issues of delays and positive input constraints in tumour growth control systems.