Citation: Bhaskarwar, T.; Hawari,
H.F.; Nor, N.B.M.; Chile, R.H.;
Waghmare, D.; Aole, S. Sliding Mode
Controller with Generalized
Extended State Observer for Single
Link Flexible Manipulator. Appl. Sci.
2022, 12, 3079. https://doi.org/
10.3390/app12063079
Academic Editors: Giovanni
Boschetti and João Miguel
da Costa Sousa
Received: 11 February 2022
Accepted: 8 March 2022
Published: 17 March 2022
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Article
Sliding Mode Controller with Generalized Extended State
Observer for Single Link Flexible Manipulator
Tushar Bhaskarwar
1
, Huzein Fahmi Hawari
2,
* , Nursyarizal B. M. Nor
2
, Rajan Hari Chile
1
,
Dhammaratna Waghmare
3
and Sumit Aole
1
1
Department of Instrumentation Engineering, Shri Guru Gobind Singhji Institute of Engineering and
Technology, Nanded 431606, India; bhaskar.tushar90@gmail.com or 2017pin604@sggs.ac.in (T.B.);
rhchile@yahoo.com (R.H.C.); sumit.aole@gmail.com (S.A.)
2
Department of Electrical & Electronic Engineering, Universiti Teknologi PETRONAS,
Seri Iskandar 32610, Malaysia; nursyarizal_mnor@utp.edu.my
3
Model Based Design, Department of Research and Development in Punch Powertrain, Pune 410506, India;
dhammasunny22@gmail.com
* Correspondence: huzeinfahmi.hawari@utp.edu.my
Abstract:
This paper presents an enhanced generalized extended state observer (EGESO) based
sliding mode control (SMC) technique for dealing with the disturbance attenuation problem for a
class of non-integral chain systems with mismatched uncertainty. In the proposed control law, the
robust SMC with reaching phase elimination is applied in the proposed control law, which uses the
estimated states of a system. The stability analysis is thoroughly examined for both EGESO and SMC.
The efficacy of the proposed controller is verified using specific examples, and later it is applied on a
single-link flexible manipulator. Through simulation and experimentation analysis, it is observed
that the proposed controller is giving a robust transient response as compared to existing GESO
based controllers.
Keywords:
generalized extended state observer (GESO); mismatched system; sliding mode controller;
non-integral chain form; real time experimentation
1. Introduction
One of the eminent problems in modern control theory is the precise modeling of
systems for robust control design. The second major challenge in robust control design
is tackling unmodeled internal nonlinearities or unmeasurable external disturbances that
may reduce the efficiency of the closed-loop system [
1
–
4
]. Implementing disturbance
estimation techniques, which can eliminate these uncertainties and modeling errors, is
always helpful in controller design due to the increase in the importance of precise control.
Various disturbance observer-based control (DOBC) techniques [
5
–
11
] have been developed
in the past few years. The survey paper [
10
] will provide a complete overview of the DOBC
study. As per [
10
], disturbance observer (DOB) [
5
], unknown input observer (UIO) [
11
],
and extended state observer (ESO) [
8
] are the most widely researched and applied among
these disturbance estimation approaches.
Although many researchers have utilized DOBC on various systems, satisfying match-
ing conditions, very few studies addressed systems with mismatched uncertainties [
12
–
15
].
ESO based control (ESOBC) only requires the relative order of system and approximate
model information [
16
–
18
]. Originally ESOBC design was in the form of a typical chain of
integrators with a matching condition considered [
19
], which restricts the ESOBC appli-
cability to the mismatched system with non-integral chain form of systems [
16
]. Recent
studies [
13
,
14
] suggested the use of GESO for such systems. The above survey motivates
us to augment states observer quality of EGESO [
14
] with robust sliding mode controller
to improve the performance of systems with mismatched uncertainty. This technique
Appl. Sci. 2022, 12, 3079. https://doi.org/10.3390/app12063079 https://www.mdpi.com/journal/applsci
