The Anti-lock Braking System (ABS) is an important component of a complex steering system for the modern car. In the latest generation of brake-by-wire systems, the performance requirements on the ABS have changed. The controllers have to be able to maintain a specified tire slip for each wheel during braking. This thesis proposes a design model and based on that a hybrid controller that regulates the tire-slip. Simulation and test results are presented.A design method for robust PID controllers is presented. Robustness is ensured with respect to a cone bounded static nonlinearity acting on the plant. Additional constraints on maximum sensitivity are also considered. The design procedure has been successfully applied in the synthesis of the proposed hybrid ABS controller.Trajectory convergence for a class of nonlinear systems is analyzed. The servo problem for piecewise linear systems is treated. Convex optimization is used to describe the behavior of system trajectories of a piecewise linear system with respect to some input signals.
The notion of vehicles moving in platoons is of considerable interest when seeking to decrease traffic congestion and gas consumption. This usually means automated operation in longitudinal and possibly lateral direction. This report focuses on the lateral dynamics and control of a vehicle platoon following a leader in the lateral direction. A thorough system modelling and analysis is conducted and different classical control approaches discussed. It is noted that overshoot cannot be avoided in the system when using reasonable feedback controllers, due to the inherent characteristics of the plant. The concept of string stability (i.e damping the propagation of errors in the platoon) is covered along with different communication topologies, which under certain assumptions will guarantee stability. It is noted that solely communicating the preceding vehicle's lateral error will not result in string stability. A novel compensation is introduced taking into account information from several vehicles, which is proven to give a string stable system.
The capability of over-actuated vehicles to maintain stability during limit handling is studied in this paper. A number of important differently actuated vehicles, equipped with hydraulic brakes toward more advanced chassis solutions, are presented. A virtual evaluation environment has specifically been developed to cover the complex interaction between the driver and the vehicle under control. In order to fully exploit the different actuators setup, and the hard nonconvex constraints they possess, the principle of control allocation by nonlinear optimization is successfully employed. The final evaluation is made by exposing the driver and the over-actuated vehicles to a safety-critical double lane change. Thereby, the differently actuated vehicles are ranked by a quantitative indicator of stability.
One of the major benefits of driving vehicles in controlled, close formations such as platoons is that of reduced air drag. However, this will set hard performance requirements on the system actuators, sensors and controllers of each vehicle. This paper analyzes the effects of fundamental limitations on the longitudinal and lateral control performance of a platoon and the effects on following distance, perceived safety and fuel economy. The trade-off between minimizing fuel consumption and maintaining a safe following distance is analyzed and described. The analysis is based on fundamental properties of linear systems such as Bode's phase area relation. Design guidelines are proposed and results from vehicle testing are presented.
One of the major benefits of driving vehicles in controlled, close formations such as platoons is that of reduced air drag. However, this will set hard performance requirements on the system actuators, sensors and controllers of each vehicle. This paper analyzes the effects of fundamental limitations on the longitudinal and lateral control performance of a platoon and the effects on following distance, perceived safety and fuel economy. The trade-off between minimizing fuel consumption and maintaining a safe following distance is analyzed and described. The analysis is based on fundamental properties of linear systems such as Bode's phase area relation. Design guidelines are proposed and results from vehicle testing are presented.
PID controller design is considered where optimal controller parameters are found with constraint on maximum sensitivity and robustness with regard to a cone bounded static nonlinearity acting in feedback with part of the plant. The design procedure has been successfully applied in the synthesis of a controller for an Anti‐lock Braking System (ABS).
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