312 Int. J. Vehicle Design, Vol. 62, No. 2/3/4, 2013 Condition monitoring of gasoline engine air intake system using second order sliding modes Qadeer Ahmed*, Aamer Iqbal Bhatti, Qudrat Khan and Mohsin Raza Control and Signal Processing Research Group, Muhammad Ali Jinnah University, Islamabad, Pakistan E-mail: qadeer62@ieee.org E-mail: aamer987@gmail.com E-mail: qudratullahqau@gmail.com E-mail: mohsin_rn@yahoo.com *Corresponding author Abstract: This paper presents a novel strategy for the condition monitoring of Air Intake System (AIS) of a gasoline engine. The aim is to detect and identify manifold leakages and throttle valve fault. These two faults directly affect AIS performance that results in poor engine efficiency. Two critical and immeasurable engine parameters i.e., Throttle Discharge Coefficient (CD) and Volumetric Efficiency (η vol ) are employed to monitor aforementioned faults. These parameters are estimated using Mean Value Engine Model (MVEM) and super twisting algorithm based Second Order Sliding Mode Observers (SOSMOs). Nominal values of the estimated parameters are used to generate residuals. These residuals are then evaluated to classify system health. A successful validation of the proposed scheme is conducted to diagnose and classify the health status of On Board Diagnostics version-II compliant commercial vehicle engine. The presented scheme is computationally cheap for online implementation and is readily applicable to cater for production line spread of single make. Keywords: automotive engine; manifold leakages; throttle valve faults; second order sliding mode observer and fault diagnosis. Reference to this paper should be made as follows: Ahmed, Q., Bhatti, A.I., Khan, Q. and Raza, M. (2013) ‘Condition monitoring of gasoline engine Air Intake System using second order sliding modes, Int. J. Vehicle Design, Vol. 62, Nos. 2/3/4, pp.312–332. Biographical notes: Qadeer Ahmed is PhD student at Mohammad Ali Jinnah University, Islamabad, Pakistan. He received his BS Degree in Mechatronics and Control Engineering from the University of Engineering and Technology, Lahore, Pakistan, in 2007 and the MS Degree in Control Systems from Mohammad Ali Jinnah University, Islamabad, Pakistan, in 2009. His research interests include robust control, estimation and condition monitoring of engineering systems. Aamer Iqbal Bhatti received the BS Degree in Electrical Engineering from the University of Engineering and Technology, Lahore, Pakistan, in 1993, Copyright © 2013 Inderscience Enterprises Ltd.