No abstract

Recent researches on advanced driver-assistance systems indicate great advances in terms of safety and comfort in automated driving. Advanced driver-assistance systems use control systems to perform most of the maneuvers as performed by the driver in the past. One of the useful advanced driver-assistance systems is automatic lane change system in order to avoid accidents. This study designs the controller of an automatic lane change system for an autonomous vehicle. The control law in this study is adaptive sliding mode control. To avoid chattering in adaptive sliding mode control, fuzzy boundary layer is used. Also, adaptive law is used for sliding-based switching gain. This adaptive controlling law is used to avoid the calculation of upper bound of system uncertainties. In this study, based on the boundary conditions, the vehicle lane change path planning and different maneuver periods are evaluated. To simulate the designed controller, CarSim-Simulink joint simulation model is used. This linkage leads to a full non-linear vehicle model. The results of simulation show excellent tracking for dry road conditions and acceptable tracking in icy and wet roads in some maneuvers of above 4-s long.

In articulated vehicles, one of the main driver's intentions is that the trailer unit closely follows the path of the tractor unit. However, this expectation is not satisfied even at low speeds. Therefore, it is necessary to develop an appropriate method to reduce or even to eliminate the path tracking error. This article proposes a new desired articulation angle for directional control of the articulated vehicles. The proposed reference value tracking ensures that the rear end of the trailer unit closely follows the trajectory of the fifth wheel. Achieving this goal, a tracking error based on the kinematics of the planar motion of the articulated vehicle is defined. Eliminating the tracking error provides a proper determination of the desired articulation angle between the tractor and trailer unit. A controller designed based on the fuzzy logic theory tracks the proposed reference articulation angle by steering the trailer wheels. To evaluate the effectiveness of the proposed method on both low-speed and high-speed maneuvers, simulations of two maneuvers including low-speed 90 turn and high-speed lane change maneuvers are carried out. The simulation results prove the significant effects of the proposed method on enhancing path following performance.

Stability and the string stability of a platoon of adaptive cruise control (ACC) vehicles using a constant spacing are investigated. Due to realistic design and execution, negative effect of tracking lag parameter on the stability is examined. An efficient analytical approach is presented in order to obtain a sufficient stability condition in the domain of the control parameters. The stability criterion is examined using a partial differential equation (PDE) approximation using large number of vehicles subjected to the time lags in vehicle dynamics and heterogeneity in the control laws, which allows asymmetry in the use of front and back information. The string stability analysis is performed to evaluate the disturbance attenuation. Finally, an example of multiple vehicle platoon control is presented, which demonstrates the effectiveness and the robustness of the proposed method.

Direct yaw moment control (DYC) is a recent active safety method introduced to control vehicle handling dynamics in non-linear regimes. The external yaw moment is considered as an important control input for DYC, which should be kept as low as possible. In the current paper, to achieve this aim, an optimal yaw rate tracking law is developed for DYC by the response prediction of a continuous non-linear vehicle dynamics model. A linear yaw rate model limited by tyre/road conditions is proposed as a desired model to be tracked by the controller. The derived control law is evaluated and its main features are discussed. The performed analysis gives an insight into the regulation of free parameters of the control law to make a compromise between tracking accuracy and control energy. The effectiveness of the designed controller is compared with a sliding mode controller, reported in literature, through simulations of various manoeuvres using a developed non-linear full vehicle dynamics model. The simulation results indicate that a satisfactory handling performance through a reduced external yaw moment can be achieved when the proposed optimal controller is engaged with the model.