Research Article Efficient Sensorless Speed Estimation of Electrical Servo Drives Using a Full-Order Nonsingular Terminal Sliding Mode Observer Tan-No Nguyen, 1,2 Thanh-Binh Pham, 1,2 Van-Trong Hoang, 1,2 Tan-Tien Nguyen, 3 Viet-Long Nguyen, 1,4 and Nguyen-Vu Truong 1 1 Institute of Applied Mechanics and Informatics, Vietnam Academy of Science and Technology, Hanoi, Vietnam 2 Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Hanoi, Vietnam 3 HCMC University of Technology, Vietnam National University HCMC, Hochiminh City, Vietnam 4 Becamex IDC Corp, Binh Duong, Vietnam Correspondence should be addressed to Nguyen-Vu Truong; nvtruong0427@gmail.com Received 31 July 2020; Revised 30 November 2020; Accepted 29 December 2020; Published 13 January 2021 Academic Editor: Alessandro Lo Schiavo Copyright © 2021 Tan-No Nguyen et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ispaperproposesanefficientsensorlessspeedestimationapproachforelectricservodrivesbasedonthefull-ordernonsingular terminalslidingmodeobserver(FONTSM)withtheapplicationofDCmotordrives.Inthismethod,aspecificfull-orderterminal sliding mode manifold is utilised for the observer design which results in the elimination of the chattering and avoiding the singularity phenomenon of conventional and terminal sliding modes. Here, speed and armature back emf can be directly es- timated from the relevant observer’s inputs which are continuous instead of being discontinuous high-frequency “switching” signals. e efficiencies and advantages of this approach have been proven and validated in both simulation and experimental results. 1. Introduction Electrical drives play vital importance in many industrial applications, household appliances, factory automation, precision machine and robotics, automotives, and so on. Typically, a precision servo drive requires an efficient control strategy and relevant sensors to measure both motor’s mechanical speed and position such as encoders and revolvers as well as its electrical quantities such as current sensors and voltage sensors. Nevertheless, in the past decades, the open literature has reported a substantial amountofresearchinsensorlesscontrolofelectricaldrives without the need of these mechanical sensors (i.e., [1–9]). is requires an efficient technique to estimate these servo mechanical quantities, i.e., rotor position via direct mea- surement of stator’s current and voltage. Numerousmethodshavebeenproposedtodealwiththis estimation problem such as [1, 5, 8–12], including the most recent sliding mode-based techniques which possess attractive advantages due to outstanding robustness to both disturbances and the system’s uncertainties (i.e., [1, 8–10, 12–14]). Conventional sliding mode-based methods (which adopt linear sliding manifolds), however, suffer serious drawback due to the chattering phenomenon which makes the observed results not suitable to be used for controlpurposes.Toovercomethis,variousapproacheshave been proposed, ranging from low-pass filter with phase compensation [3] and boundary layer approximation [4] to higher-orderslidingmodemethod[12–15]and,particularly, terminal sliding mode methods [10–12, 16–25]. Conventional sliding mode control with low-pass filter or with boundary layer approximation would significantly reduce chattering but suffers loss of system’s robustness and introductionofsignificantphaseshiftandsteady-stateerrors of the estimation. Higher-order sliding mode (HOSM) methods work with the discontinuous control in its higher- order derivatives [13–15]. Here, the switching function (discontinuous control) is at the higher-order derivatives to Hindawi Mathematical Problems in Engineering Volume 2021, Article ID 8175848, 8 pages https://doi.org/10.1155/2021/8175848