Automotive Science and Engineering

---

In spark ignition (SI) engines, the accurate control of air fuel ratio (AFR) in the stoichiometric value is required to reduce emission and fuel consumption. The wide operating range, the inherent nonlinearities and the modeling uncertainties of the engine system are the main difficulties arising in the design of AFR controller. In this paper, an optimization-based nonlinear control law is analytically developed for the injected fuel mass flow using the prediction of air fuel ratio response from a mean value engine model. The controller accuracy is more increased without chattering by appending the integral feedback technique to the design method. The simulation studies are carried out by applying severe changes in the throttle body angle to evaluate the performance of the proposed controller with and without integral feedback. The results show that the proposed controller is more effective than the conventional sliding mode controller in regulating the AFR without chattering.

---

Due to the increasing development in various branches of the automotive industry, the need for a comfort climate in the cabin is more sensible. However, to achieve climate comfort, HVAC system consumes a considerable amount of engine power. Hence, improving HVAC system performance leads to more energy saving of the vehicle which is a critical factor for nowadays automotive. Besides, one crucial task of HVAC system is defrosting/defogging of windshield which is considered as a mandatory requirement in most countries. In the current study, the defrosting/defogging performance of HVAC system in the main product of national vehicle platform is numerically evaluated based on the ECE-78-715 legal requirement. For this purpose, after validation and mesh independency study, the transient air flow in three-dimensional cabin geometry is simulated by SSTk-ω turbulence model via ANSYS Fluent software and the windshield thermal condition is reported during defrosting/defogging. Besides, two national HVAC standards of AERC-10-01 and AERC-10-02 are also checked. The results demonstrate that HVAC system of the main product of the national vehicle platform can satisfactorily fulfill ECE-78-715, AERC-10-01 and AERC-10-02.

---

Vertical dynamics modeling and simulation of a six-wheel unmanned military vehicle (MULE) studied in this paper. The Common Mobility Platform (CMP) chassis provided mobility, built around an advanced propulsion and articulated suspension system gave the vehicle ability to negotiate complex terrain, obstacles, and gaps that a dismounted squad would encounter. Aiming at modeling of vehicle vertical dynamics, basic and geometrical parameters defined and degrees-of-freedom specified on a compromise between accuracy and complexity of two models. Equations of motion provided on two linear and nonlinear 5-degree-of-freedom models using two different modeling methods. There is good agreement between time responses of two presented models. The main differences of two models observed in articulated suspension degrees-of-freedom while the vehicle subjected to high frequency maneuvers that cause severe oscillations on wheels and arms in comparison to vehicle body due to lower mass and inertia properties. The linear model can be used to design a controller and the nonlinear to predict vehicle motion more accurately. Sensitivity analysis of the influential parameters is also presented to specify effects of different parameters. Results of this study may be used to design articulated suspension and making next frequency analyses.