Browsing by Author "Ozkan, Basar"

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Citation Count: 4
Disturbance Observer Based Active Independent Front Steering Control for Improving Vehicle Yaw Stability and Tire Utilization
(Korean Soc Automotive Engineers-ksae, 2022) Gozu, Murat; Ozkan, Basar; Emirler, Mumin Tolga
In the currently used steering systems, the front tires are steered dependently during turning maneuvers. During these maneuvers, the weight transfer causes the inner tire to have less vertical force compared to the outer tire. Therefore, it generates less lateral tire force and can be saturated easily in some extreme conditions. On the other hand, the outer tire can provide more lateral force due to the higher vertical force, but its potential may not be utilized because the steering of the inner and outer tires is dependent. Thus, an independent steering capability can provide potential benefits by eliminating the saturation of the inner tire and getting more lateral force from the outer tire. Therefore, an active independent front steering system is proposed by combining a yaw-rate PI controller with disturbance observers on tire forces to improve the yaw stability at the acceptable limits. The coefficients of the PI controller are calculated analytically. The cut-off frequency in the disturbance observer is determined by the robust stability analysis considering the variance in the vehicle dynamic parameters. Finally, by taking into account the tire utilization coefficient (TUC), the performance of the proposed system is compared to conventional active steering systems in CarSim simulation environment.
Estimation of the tire-road friction coefficient andstability control of the vehicle by steering right and theleft tires independently
(2021) Gözü, Murat; Ozkan, Basar
ESTIMATION OF THE TIRE-ROAD FRICTION COEFFICIENT AND STABILITY CONTROL OF THE VEHICLE BY STEERING RIGHT AND THE LEFT TIRES INDEPENDENTLY Over the last two decades, the automotive industries have been aiming to develop more advanced driving assisting systems (ADAS) such as anti-lock braking system (ABS), electronic stability control system (ESC), and lane keeping assist system (LKA) to improve safety of the ground vehicles for saving lives and preventing injuries. Most of the ADAS systems are utilizing longitudinal and lateral tire forces to realize the desired handling characteristics and improve the stability of the vehicle. The utilized tire forces are dependent on the surface friction and the tire loads. The surface friction is the most important mechanism for generating the tire forces. The saturation limits of the forces vary on di erent road surfaces which have di erent coe cients of surface friction, and it has a negative impact on the performance of the active safety systems which have a control structure assuming a constant coe cient of surface friction. For example, these systems can not provide enough tire forces to stabilize the vehicle on icy roads because of the reduced saturation limits. Therefore, it is crucial to know or estimate the coe cients of the friction of the road surfaces to improve the performance of the active safety system. In the rst part of the thesis, the estimation methods for the coe cients of the surface friction are investigated and a new estimation technique based on the active independent steering control system (AISCS) that has independent front tire steering capability was proposed. The second part of this thesis focuses on enhancing the performance of the in troduced AISCS system. After investigating the bene ts of the AISCS, two new control structures were proposed to improve its yaw-rate performance. The rst one is based on the inverse Pacejka tire model to determine the required steering angles for both tires. The second one uses tire forces as feedback and combines a conventional yaw controller with disturbance observers to calculate required steering angles. Keywords: Estimation of tire-road friction coe cient, tire model, simulation, Control system, Vehicle yaw stability, Active steering control, Independent steering, Disturbance observer
Citation Count: 2
Lateral Stability Control of Articulated Heavy Vehicles Based on Active Steering System
(Engineering & Technology Publishing, 2022) Emheisen, Mustafa A.; Emirler, Mumin Tolga; Ozkan, Basar
The main purpose of this paper is to design a controller for improving the lateral stability of long heavy vehicle combinations based on active steering system. An augmented optimal linear quadratic control system design is implemented. The controller is developed and evaluated with step and lane change maneuvers for a truck and trailer combination. The uncertainties masses of the truck and trailer are taken into account for analysis purpose. The nonlinear and linear model of the truck and trailer are presented. The simulation results show a decrease in yaw rate rearward amplification and sideslip angles significantly with successful desired yaw rate tracking for the trailer.
Citation Count: 3
Optimisation of tractor semi-trailer command steering mechanism using a genetic algorithm
(inderscience Enterprises Ltd, 2016) Ozkan, Basar; Aptoula, Erchan; Heren, A. Tayfun; Mandaci, Hasan
Steering the rear wheels of semi-trailers has become common to improve the manoeuvrability of the vehicle. Command steering is one of the methods of steering semi-trailers. Depending on the articulation angle, a mechanism steers the rear wheels accordingly. In this paper, this mechanism is optimised to meet three goals. The first goal is staying within the boundaries of the road for specific tests. The second goal is to decrease tyre wear. The third goal is to minimise the difference between the trailer hub angles caused by the left and right hydraulic pistons of the steering system. All of these goals are achieved using a genetic algorithm by searching the parameter space. The hydraulic and mechanical command steer system is also modelled and used in the optimisation process. The complete system is optimised so that the semi-trailer wheels approximate the Ackerman condition as closely as possible.