Bilin Aksun Güvenç

Robust Yaw Stability Controller Design and Hardware-in-the-Loop Testing for a Road Vehicle

Unsymmetrical loading on a car like mu-split braking, side wind forces, or unilateral loss of tire pressure results in unexpected yaw disturbances that require yaw stabilization either by the driver or by an automatic driver-assist system. The use of two-degrees-of-freedom control architecture known as the model regulator is investigated here as a robust steering controller for such yaw stabilization tasks in a driver-assist system. The yaw stability-enhancing steering controller is designed in the parameter space to satisfy a frequency-domain mixed sensitivity constraint. To evaluate the resulting controller design, a real-time hardware-in-the-loop simulator is developed. Steering tests with and without the controller in this hardware-in-the-loop setup allow the driver to see the effect of the proposed controller to improve vehicle-handling quality. The hardware-in-the-loop simulation setup can also be used for real-time driver-in-the-loop simulation of other vehicle control systems.

Coordination of steering and individual wheel braking actuated vehicle yaw stability control

Active safety of road transport requires, among other things, the improvement of road vehicle yaw stability by active control. One approach for yaw dynamics improvement is to use differential braking, thereby creating the moment that is necessary to counteract the undesired yaw motion. An alternative approach is to command additional steering angles to create the counteracting moment. The maximum benefit, of course, can be gained through coordinated and combined use of both methods of corrective yaw motion generation in a control strategy. This problem has been approached by using a revised model regulator here as the main controller that utilizes coordinated steering and individual wheel braking actuation, with the aim of achieving better vehicle yaw stability control. Independent use of the individual means of actuation are treated first. Possible strategies for combined and coordinated use of steering and individual wheel braking action in a vehicle yaw dynamics controller are then presented. Simulation results on a nonlinear two track vehicle model are used to illustrate the effectiveness of the coordinated approach.

Robust two degree-of-freedom add-on controller design for automatic steering

A robust 2-DOF add-on controller design based on the disturbance observer is presented in this paper for improved performance in vehicle automatic steering. The application example is the benchmark problem on automatic steering of a city bus with large variations in mass and speed and for which the reference maneuvers and specifications are available in the literature. The analytical formulation of the compensator is presented, followed by evaluation and demonstration of the enhanced model regulation and disturbance rejection properties achieved by its use. Improved steering dynamics can be achieved using yaw rate feedback without the need for a yaw rate sensor. Noting that the steering angle rate actuator saturation forms a major limitation of performance, especially in the presence of the integrating actuator used in the city bus example, the performance enhancement due to the disturbance observer-based add-on compensator is investigated in the presence of actuator saturation. Finally, a disturbance feedforward-based add-on compensator is also presented for well-defined reference trajectories like the entering a bus stop bay maneuver, enabling preview.

Extremum-Seeking Control of ABS Braking in Road Vehicles With Lateral Force Improvement

An ABS control algorithm based on extremum seeking is presented in this brief. The optimum slip ratio between the tire patch and the road is searched online without having to estimate road friction conditions. This is achieved by adapting the extremum-seeking algorithm as a self-optimization routine that seeks the peak point of the tire force-slip curve. As an additional novelty, the proposed algorithm incorporates driver steering input into the optimization procedure to determine the operating region of the tires on the “tire force”-“slip ratio” characteristic-curve. The algorithm operates the tires near the peak point of the force-slip curve during straight line braking. When the driver demands lateral motion in addition to braking, the operating regions of the tires are modified automatically, for improving the lateral stability of the vehicle by increasing the tire lateral forces. A validated, full vehicle model is presented and used in a simulation study to demonstrate the effectiveness of the proposed approach. Simulation results show the benefits of the proposed ABS controller.

Robustness of disturbance observers in the presence of structured real parametric uncertainty

The disturbance observer is a widely used form of a two degree of freedom control architecture which reduces sensitivity to modeling error while enhancing disturbance rejection properties. While standard robust stability analysis of the disturbance observer in the presence of unstructured modeling error is well known and results in a simple design guideline, similar results are lacking for the case of structured, real parametric uncertainty in the plant. Considering the case in which the plant has real parametric uncertainty, the real structured singular value method is applied to stability and performance robustness analysis, resulting in less conservative results. The model of an electrohydraulic positioning system with large parametric variation especially in its damping ratio is used to illustrate the concept. The results are extended to the case in which the plant under disturbance observer regulation is also under feedback control, as is usually the case in applications.

A control strategy for parallel hybrid electric vehicles based on extremum seeking

An energy management control strategy for a parallel hybrid electric vehicle based on the extremum-seeking method for splitting torque between the internal combustion engine and electric motor is proposed in this paper. The control strategy has two levels of operation: the upper and lower levels. The upper level decision-making controller chooses the vehicle operation mode such as the simultaneous use of the internal combustion engine and electric motor, use of only the electric motor, use of only the internal combustion engine, or regenerative braking. In the simultaneous use of the internal combustion engine and electric motor, the optimum energy distribution between these two sources of energy is determined via the extremum-seeking algorithm that searches for maximum drivetrain efficiency. A dynamic programming solution is also obtained and used to form a benchmark for performance evaluation of the proposed method based on extremum seeking. Detailed simulations using a realistic model are presented to illustrate the effectiveness of the methodology.

Robust steer-by-wire control based on the model regulator

Unsymmetrical loading on a car (like /spl mu/-split braking, side wind forces or unilateral loss of tire pressure) result in unexpected yaw disturbances that require yaw stabilization either by the driver or by an automatic driver assist system. The use of the two degree of freedom control architecture known as the model regulator is investigated here as a robust steering controller for such yaw stabilization tasks in a driver-assist system. Robust controller design for satisfying a mixed sensitivity constraint is presented. The technique of mapping frequency domain bounds to parameter space is used in the design calculations and explicit formulas for the point condition solution are obtained for the steering model regulator. Design and subsequent simulation studies are conducted at six exemplary operating conditions. While linear simulation results based on the linearized single track model are given, the nonlinear single track model based simulation results are also given to demonstrate the fulfillment of the desired control tasks of yaw moment disturbance rejection and model regulation. The nonlinear single track model simulations are also used to demonstrate the effectiveness of the gain scheduled implementation of the steering model regulator used.

Model regulator based individual wheel braking control

Yaw stability control systems are important components of active safety systems for road transport. A model regulator based yaw stability control system that was previously implemented and tested very successfully as a steering controller is adapted to work as an individual wheel braking controller in this paper. A two track nonlinear vehicle model is used to test the individual wheel braking actuated model regulator developed here. Simulation results are used to demonstrate the achievement of good yaw disturbance moment rejection by the proposed controller.

Model Predictive Adaptive Cruise Control

In this paper, the Model Predictive Control (MPC) structure is used to solve the ACC problem and the performance of the design is tested using a realistic nonlinear vehicle model. A hierarchical control structure is used where MPC is placed on top of the hierarchy while the actuators are controlled by simpler linear controllers. The real-time optimization needed for MPC is solved using Quadratic Programming (QP). The performance of the MPC is tested under different traffic scenarios. The control system is able to determine the ongoing scenarios autonomously, using available measurements.

Automated Robust Path Following Control Based on Calculation of Lateral Deviation and Yaw Angle Error

Automated driving vehicles are expected to be ready for series production by 2020. An important component of automated driving technologies is controlled path following under longitudinal speed control. In this paper, a robust path following controller design based on lateral deviation and yaw angle error determination of the vehicle is proposed. The constrained least square method is used for obtaining continuity and smoothness of the segment boundaries of the digital trajectory map to be followed. The lateral deviation and yaw angle error are calculated by comparing the generated digital map trajectory and the vehicle position. The parameter space approach is used in the design stage of the controller considering D-stability requirements. The solution regions of the controller are plotted in three dimensional parameter space. The designed controller is tested with simulations on a path chosen from the Ohio State University campus.Copyright