Behrooz Mashadi

Dual-Mode Power-Split Transmission for Hybrid Electric Vehicles

In this paper, an innovative power-split device (PSD) is introduced, and its application in a hybrid powertrain system is studied. The new PSD is a mechanism that allows operation in two different power-split modes through locking/unlocking of two clutches. In one mode, the PSD operates similar to a standard planetary gear unit, and in the other mode, it works the same as a compound planetary set. A well-known analogous system is the Toyota Hybrid System (THS) and is used for comparison purposes. It is demonstrated that by the new system, the transmission losses are reduced by a considerable extent, and thus, the efficiency is improved. A controller is designed based on fuzzy logic, which receives the battery state of charge (SOC), the vehicle speed, and the power that is requested at the wheels to coordinate each component in such a way as to optimize the entire system efficiency. A numerical optimization algorithm is applied to sustain the SOC in high regions and shift engine operating points to higher efficiency regions. Simulation results demonstrate notable improvements in fuel economy and performance characteristics.

Vehicle path following control in the presence of driver inputs

The main contribution of this article is the development of a controller for tracking of the driver intended path of an integrated driver/vehicle system. The controller receives heading and lateral deviation errors as well as the driver input and determines a corrective steering angle and a direct yaw moment to be applied to the vehicle so that a desired path is achieved. A genetic algorithm procedure is utilized in order to adapt a set of optimized controller parameters suitable for various driving styles, road conditions and the initial errors of vehicle position and orientation. The sensitivity of driver/vehicle system response to the driver model, road and vehicle initial conditions is investigated. Computer simulations are performed to study the effectiveness of the proposed controller in different driving conditions, namely single- and double-lane changes, J-turn and other desired tracks. Simulation results demonstrated that the proposed controller was able to effectively keep the vehicle path very close to the desired path even in the presence of the driver commands.

A path-following driver/vehicle model with optimized lateral dynamic controller

Reduction in traffic congestion and overall number of accidents, especially within the last decade, can be attributed to the enormous progress in active safety. Vehicle path following control with the presence of driver commands can be regarded as one of the important issues in vehicle active safety systems development and more realistic explanation of vehicle path tracking problem. In this paper, an integrated driver/DYC control system is presented that regulates the steering angle and yaw moment, considering driver previewed path. Thus, the driver previewed distance, the heading error and the lateral deviation between the vehicle and desired path are used as inputs. Then, the controller determines and applies a corrective steering angle and a direct yaw moment to make the vehicle follow the desired path. A PID controller with optimized gains is used for the control of integrated driver/DYC system. Genetic Algorithm as an intelligent optimization method is utilized to adapt PID controller gains for various working situations. Proposed integrated driver/DYC controller is examined on lane change manuvers andthe sensitivity of the control system is investigated through the changes in the driver model and vehicle parameters. Simulation results show the pronounced effectiveness of the controller in vehicle path following and stability.

Effects of the triggering of circular aluminum tubes on crashworthiness

Axial crash of thin-walled circular aluminum tubes is investigated in this study. These kinds of tubes usually are used in automobile and train structures to absorb the impact energy. An explicit finite element method (FEM) is used to model and analyse the behaviour. Formulation of the energy absorption and the mean crash force in the range of variables is presented using design of experiments (DOE) and response surface method (RSM). Comparison with experimental tests has been accomplished in some results for validation. Also, comparison with the analytical aspect of this problem has been done. Mean crash force has been considered as a constraint as its value is directly related to the crash severity and occupant injury. The results show that the triggering causes a decrease in the maximum force level during crash.

Integrated AFS/DYC sliding mode controller for a hybrid electric vehicle

A multi-layer integrated controller of active front steering and direct yaw moment is developed in this study. In the upper layer, the corrective steering angle and yaw moment are obtained using Sliding Mode Control (SMC) with combined sliding surface. The corrective yaw moments are applied by electric motors embedded in rear wheels. The desired value for yaw rate and sideslip angle are obtained from a Four-Degrees of Freedom (DOF) non-linear vehicle model. In the lower layer, wheel slip and electric motor torque controllers are designed. A 9-DOF non-linear vehicle model is used for simulations and their results illustrate considerable improvements in vehicle handling.

Optimal vehicle dynamics controller design using a four-degrees-of-freedom model

Abstract A yaw moment control system is developed for a front-wheel-drive vehicle utilizing two brushless d.c. electric motors embedded in the rear wheels. An optimal linear quadratic regulator (LQR) controller is employed by using a four-degrees-of-freedom (4DOF) linear vehicle model. The objective is to include important effects of roll and steering into the controller design. A two-degrees-of-freedom (2DOF) optimal LQR model is also used for comparison purposes. For the simulation of system at different conditions, a non-linear eight-degrees-of-freedom vehicle model is used. The performances of the controlled vehicle have been compared with those of the uncontrolled vehicle in order to investigate the effectiveness of the proposed controllers. Simulation results indicate that, in normal situations where the uncontrolled vehicle becomes unstable, the controlled vehicles with both 2DOF and 4DOF controllers show stable responses. In severe conditions, however, even the 2DOF controller fails to stabilize the vehicle, whereas the 4DOF controller is successful in maintaining the stability of vehicle.

GLOBAL OPTIMAL PATH PLANNING OF AN AUTONOMOUS VEHICLE FOR OVERTAKING A MOVING OBSTACLE

In this paper, the global optimal path planning of an autonomous vehicle for overtaking a moving obstacle is proposed. In this study, the autonomous vehicle overtakes a moving vehicle by performing a double lane-change maneuver after detecting it in a proper distance ahead. The optimal path of vehicle for performing the lane-change maneuver is generated by a path planning program in which the sum of lateral deviation of the vehicle from a reference path and the rate of steering angle become minimum while the lateral acceleration of vehicle does not exceed a safe limit value. A nonlinear optimal control theory with the lateral vehicle dynamics equations and inequality constraint of lateral acceleration are used to generate the path. The indirect approach for solving the optimal control problem is used by applying the calculus of variation and the Pontryagins Minimum Principle to obtain first-order necessary conditions for optimality. The optimal path is generated as a global optimal solution and can be used as the benchmark of the path generated by the local motion planning of autonomous vehicles. A full nonlinear vehicle model in CarSim software is used for path following simulation by importing path data from the MATLAB code. The simulation results show that the generated path for the autonomous vehicle satisfies all vehicle dynamics constraints and hence is a suitable overtaking path for the following vehicle.

Two-phase optimal path planning of autonomous ground vehicles using pseudo-spectral method

In this paper, an optimal path-planning method is proposed for autonomous ground vehicles in case of overtaking a moving obstacle by the application of a two-phase optimal-control problem. When the autonomous vehicle detects a moving vehicle in a proper speed and distance ahead, it decides to overtake the obstacle by executing a double-lane change manoeuvre. The path for the overtaking manoeuvre is generated by a two-phase optimal path-planning problem. The cost function of the first phase is defined in such a way that the vehicle approaches the obstacle as close as possible. In the second phase, the cost function is defined as sum of the vehicle lateral deviation from the reference path and the rate of steering angle. At the same time, the lateral acceleration of the vehicle must not exceed a specified limit. The radio pseudo-spectral method, which is a method for direct trajectory optimization using global collocation at Legendre–Gauss–Radau points, is applied for solving the two-phase nonlinear optimal-control problem. A full nonlinear vehicle model in CarSim software is used for path-tracking simulation by importing path data from a MATLAB code. The simulation results show that the generated path for the autonomous vehicle satisfies all vehicle-dynamics constraints and hence is applicable for a real autonomous vehicle.

Vehicle lift-off modelling and a new rollover detection criterion

ABSTRACT The modelling and development of a general criterion for the prediction of rollover threshold is the main purpose of this work. Vehicle dynamics models after the wheels lift-off and when the vehicle moves on the two wheels are derived and the governing equations are used to develop the rollover threshold. These models include the properties of the suspension and steering systems. In order to study the stability of motion, the steady-state solutions of the equations of motion are carried out. Based on the stability analyses, a new relation is obtained for the rollover threshold in terms of measurable response parameters. The presented criterion predicts the best time for the prevention of the vehicle rollover by applying a correcting moment. It is shown that the introduced threshold of vehicle rollover is a proper state of vehicle motion that is best for stabilising the vehicle with a low energy requirement.

Active vehicle rollover control using a gyroscopic device

A gyroscopic system is designed and utilized as an actuator for the prevention of vehicle rollover. The vehicle motion before rollover and during rollover is considered in two phases: before lift-off of the wheels and after lift-off of the wheels. The lateral load transfer ratio is used to identify the time when the wheels lift off the ground. Based on the equations of motion for the vehicle on two wheels, an imminent rollover algorithm is designed to specify the rollover risk. A fuzzy controller that determines the required roll moment to stabilize the vehicle is designed. A gyroscopic package is designed to apply the corrective roll torque directly on the rolling mass of the vehicle in the opposite direction to the rollover moments. The performance of the proposed system is investigated by simulating some severe manoeuvres, and the results show that the system is able to stabilize the vehicle successfully.