Prof. Nariman Sepehri
Department of Mechanical Engineering, University of Manitoba, Winnipeg, MB R3T 5V6, Canada
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Academic Career Length
28Years (1999-Present)
(Calculated once Scilit publication data is synced: current year − year of first publication + 1)
Representative Publications
View All Publications1 January 2005 in International Journal of Fluid Power
Journal Article
LALiang An
Liang AnNariman SepehriThis paper presents the application of extended Kalman filter (EKF) in order to identify leakage faults in hydraulically powered actuators. A hydraulic actuator can suffer from two types of leakages: internal or cross-port leakage at the piston seal and, external leakage at the shaft seal or the connecting pipes. An EKF-based estimator is constructed that includes complete nonlinear models of hydraulic functions as well as inevitable stick-slip friction in the actuator. It is shown that, firstly, under normal (no-fault) operating condition, the developed estimator closely predicts the states of the system, using only a few basic measurements. Secondly, in the presence of leakage faults, the level of residual errors between the estimated and the measured line pressures, increase significantly indicating the occurrence of faults. Thirdly, different leakage types can be identified by mapping the residual errors changes. Experiments are performed on a laboratory-based hydraulic actuator circuit. The results demonstrate the efficacy of the proposed EKF-based fault detection scheme to promptly and reliably respond to actuator's external and internal leakage faults.
Journal Article
SASamira Ahmadi
Samira AhmadiNariman SepehriCWChristine Wu
Christine Wu
Tony Joseph SztSzturmurmSample entropy (SampEn) has been used to quantify the regularity or predictability of human gait signals. There are studies on the appropriate use of this measure for inter-stride spatio-temporal gait variables. However, the sensitivity of this measure to preprocessing of the signal and to variant values of template size (m), tolerance size (r), and sampling rate has not been studied when applied to “whole” gait signals. Whole gait signals are the entire time series data obtained from force or inertial sensors. This study systematically investigates the sensitivity of SampEn of the center of pressure displacement in the mediolateral direction (ML COP-D) to variant parameter values and two pre-processing methods. These two methods are filtering the high-frequency components and resampling the signals to have the same average number of data points per stride. The discriminatory ability of SampEn is studied by comparing treadmill walk only (WO) to dual-task (DT) condition. The results suggest that SampEn maintains the directional difference between two walking conditions across variant parameter values, showing a significant increase from WO to DT condition, especially when signals are low-pass filtered. Moreover, when gait speed is different between test conditions, signals should be low-pass filtered and resampled to have the same average number of data points per stride.
1 January 2008 in Journal of Dynamic Systems, Measurement, and Control
Journal Article
HZHairong Zeng
Hairong Zeng
Nariman SepehriThis paper addresses the tracking control of hydraulic actuators commonly used in many hydraulically actuated robotic systems. Dynamic model of the entire actuator incorporating highly nonlinear hydraulic functions and the LuGre dynamic friction model is used to arrive at a suitable controller. The controller is augmented with adaptation laws to compensate for parametric uncertainties in the actuator dynamics, hydraulic functions as well as friction with nonuniform force variations. Furthermore, an adaptive observer is used in the controller to avoid the use of acceleration measurement. Therefore, only measurements of displacement, velocity, and hydraulic line pressures are required for the implementation of the proposed controller. Stability and convergence of the control system are theoretically studied. Experimental results are presented verifying the effectiveness of the developed controller.
18 January 2019 in IEEE/ASME Transactions on Mechatronics
Journal Article
This paper presents a model-free design procedure for the position control of hydraulic actuators. A fractional-order PID (FOPID) controller is designed by employing the Oustaloup recursive method. The controller parameters are tuned experimentally based on the Iterative Feedback Tuning (IFT) technique. The IFT optimizes an objective function using the experimental data taken from an instrumented valve-controlled hydraulic actuator test rig. The objective function, to be minimized, includes both tracking and robust stability criteria. The efficacy of the proposed controller is examined by comparing the experimental results with those from a Quantitative Feedback Theory (QFT)-based controller. Although the QFT controller gives rise to good tracking responses, the comparisons show that the FOPID controller results in better settling time in tracking the desired response than the QFT controller. Moreover, it is much less sensitive to the effect of the hunting phenomenon, originating from the dry friction, than the QFT controller. The robustness of the FOPID controller against system uncertainties including the external load, the inertia and friction is also demonstrated.
30 May 2019 in International Journal of Control, Automation, and Systems
Journal Article
About Me
Nariman Sepehri is a Distinguished Professor of
Mechanical Engineering at the University of Manitoba, Canada. He received his
PhD degree from the University of British Columbia, Canada. He served as the
Department Associate Head (Graduate Studies) of Mechanical Engineering,
Associate Dean of Engineering (Undergraduate Programs), and Acting Dean of
Engineering at the University of Manitoba. He received the Dean of
Engineering’s Award for Superior Academic Performance and the University of
Manitoba Rh Award for outstanding contributions to scholarships and research in
Applied Sciences. He is a Senior Member of IEEE, Fellow of ASME, Fellow CSME,
Fellow CAE, and the Past-Chair ASME Fluid Power Systems and Technology Division; is a Co-founder and Chair of the IEEE Winnipeg Robotics, Control, Instrumentation and
Measurement (RobConIM) Chapter; and has been an Associate Editor or Editorial
Board Member of several journals, including the ASME Journal of Dynamics Systems,
Measurement and Control, the International Journal of Control, and IFAC Control
Engineering Practice. His research and development activities are
primarily centred on fluid power-related aspects of systems, manipulation,
diagnosis, and control, covering a wide range of applications, including robotics
(mining/underwater hydraulic manipulators), manufacturing (injection molding),
aerospace (flight control actuators), off-highway (excavator machines),
processes, and healthcare (rehabilitation devices).