Integrated nonlinear suboptimal control‐and‐estimator based on the state‐dependent differential Riccati equation approach

Abstract

This paper is devoted to the theory and application of a combined nonlinear suboptimal control and estimator based on the state‐dependent differential Riccati equation (SDDRE), aiming finite‐time tracking of manipulators that possess flexible joints. Though measuring the angular positions of links is possible for flexible joint manipulators (FJMs), it is not feasible to measure the changes in the position angles of actuators. In addition, the existence of measurement noise and the influence of unknown workspace disturbance are always unavoidable. Therefore, combining an estimator with a controller could result in full‐state feedback for the system. Designing the proposed integrated estimator algorithm includes two parts: The first part is the theoretical extension of the SDDRE approach expressed with nonlinear state variables and inputs of the system in a finite‐time horizon. In the second part, enhancing and upgrading software and hardware interface, the proposed procedure for FJMs is modeled and simulated. Then, the experimental implementation is applied in the online closed‐loop form.