Transactions on Machine Intelligence

Transactions on Machine Intelligence

Designing a Fuzzy Controller Based on Disturbance Observer and Smith Predictor for Linear Uncertain Time-Delay Systems

Document Type : Original Article

Authors
H. Asmae 1
A. Karami 2
1 M.Sc. Student of Electrical Engineering, Control, K. N. Toosi University of Technology, Tehran, Iran
2 Ph.D. Student of Electrical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
10.47176/TMI.2018.191
Abstract
In control systems, conventional disturbance observer (DOB) structures often fail to perform optimally when the system involves delays, leading to inefficiencies in disturbance rejection. This paper addresses this limitation by first employing the conventional Smith predictor method to compensate for the negative effects of delay within the control loop. Following this, a conventional disturbance observer is implemented to estimate external disturbances. However, this approach has certain constraints, particularly in handling unpredictable or complex disturbances. To overcome these challenges, this study explores an alternative approach: the Composite Disturbance Observer (CDOB), which is based on the concept of Network Disturbance (ND). In this framework, system delay is treated as an external disturbance, and since the transformed system becomes delay-free, the conventional DOB structure can be applied effectively. A key advantage of the proposed CDOB method is its ability to estimate and compensate for disturbances without requiring prior knowledge of the delay or assuming specific conditions such as periodic disturbances, which are often considered in related studies. Furthermore, a fuzzy PID controller is utilized for process control, offering adaptive tuning capabilities to enhance performance. The proposed approach is validated through comprehensive simulations, which demonstrate the superior performance of the CDOB in mitigating the adverse effects of delay while ensuring robust disturbance rejection. The results highlight the effectiveness of this method in improving system stability and response under various operating conditions.
Keywords
Conventional Disturbance Observer
Smith Predictor
Network Disturbance
Fuzzy Controller
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Transactions on Machine Intelligence
Volume 1, Issue 4
Autumn 2018
Pages 191-203

  • Receive Date 02 June 2018
  • Revise Date 09 October 2018
  • Accept Date 11 December 2018