Browsing by Subject "Controller parametrization"

Now showing 1 - 3 of 3

Open Access
Adaptive friction compensations for mechanical systems with measurement delay
(SAGE Publications, 2021) Odabaş, Caner; Morgül, Ömer
Application performance of mechanical positioning systems might not coincide with the theory, mainly due to nonlinearities or imperfections of system models. Although it is sometimes possible to ignore these mismatches, systems generally suffer from performance degradation or even instability eventually. Especially, friction force and time delay are two major factors of these undesired effects. Hence, in this paper, Smith predictor-based controllers and an adaptive Coulomb friction observer are designed to enhance position tracking performance of a mechanical system including time delay. In fact, implemented hierarchical control scheme provides two-degree of freedom to control both velocity and position separately. The proposed observer structure is mainly motivated by the Friedland-Park observer but could be considered as an extension of it which characterizes a general class of nonlinear functions for friction estimation. To assure its functionality with delayed measurements, different velocity predictor schemes are designed and their performances are compared. As a guideline for observer design, some conditions for exponential stability and robustness analysis are presented. Simulation results demonstrate that the proposed control system enhances the tracking performance even when the actual friction is a compound of various static and dynamic terms.
Open Access
Observer based friction cancellation in mechanical systems
(IEEE, 2014-10) Odabaş, Caner; Morgül, Ömer
An adaptive nonlinear observer based friction compensation for a special time delayed system is presented in this paper. Considering existing delay, an available Coulomb observer is modified and closed loop system is formed by using a Smith predictor based controller as if the process is delay free. Implemented hierarchical feedback system structure provides two-degree of freedom and controls both velocity and position separately. For this purpose, controller parametrization method is used to extend Smith predictor structure to the position control loop for different types of inputs and disturbance attenuation. Simulation results demonstrate that without requiring much information about friction force, the method can significantly improve the performance of a control system in which it is applied. © 2014 Institute of Control, Robotics and Systems (ICROS).
Open Access
On Smith predictor-based controller design for systems with integral action and time delay
(IEEE, 2013-06) Taşdelen, Uğur; Özbay, Hitay
A new Smith predictor based controller is proposed for systems with integral action and flexible modes under input-output time-delay. The design uses controller parametrization and aims to achieve a set of performance and robustness objectives. Compared to existing Smith predictor based designs, disturbance attenuation property is improved, with respect to periodic disturbances at a known frequency. A two-degree of freedom controller structure is shown to be helpful in shaping the transient response under constant reference inputs. Stability robustness properties of this system are also investigated. Simulation results demonstrate the effectiveness of the proposed controller. © 2013 IEEE.