Design and Experimental Implementation of an Adaptive Feedback Linearization Controller Based on Extended State Observer for a Flexible-joint Arm

This study deals with the design and experimental implementation of an adaptive feedback linearization controller for a flexible joint lever-arm (FJLA) in the presence of uncertainties and external disturbances. An extended state observer is proposed to upgrade the reduced-order model to an accurate and reliable model with the same order. In the proposed method, the uncertainties and external disturbances are assumed as an extended state and the link position information is used to estimate this state in combination with the angular velocity of the link states. The control system designed based on the proposed observer can adapt itself to real conditions, and use enough information about uncertainties and disturbances. The proposed controller with and without using the observer is examined on a fabricated flexible-joint lever arm. The results indicate that the uncertainties and disturbances are well estimated online for being used in the controller. Therefore, the proposed adaptive controller using just one sensor has a higher accuracy in controlling the position of the FJLA under different trajectories. Also, the proposed control method is fast and suitable for online implementation.