Control of Systems with Limited Capacity

Virtually all real life systems are such that they present some kind of limitation on one or many of its variables, physical quantities. These systems are designated in this thesis as systems with limited capacity. This work is treating control related problems of a subclass of such systems, where the limitation is a critical factor. The thesis is composed of four parts. The first part is treating the control of tire slip in a braking car. 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 controllers have 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 results from drive tests are presented. In the second part, a design method for robust PID controllers is presented for a class of systems with limited capacity. 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 ABS controller. The third part studies the trajectory convergence for a general class of nonlinear systems. The servo problem for piecewise linear systems is presented. Convex optimization is used to describe the behavior of system trajectories of a piecewise linear system with respect to some input signals. The obtained results are then applied for the study of anti-windup compensators. The last part of the thesis is treating the problem of voltage stability in power systems. Voltage at the load end of a power system has to be controlled within prescribed tolerances. In case of emergencies such as sudden line failures, this task ca n be very challenging. The main contribution of this chapter is a method for improving the stability properties of the power system by dynamic compensation of the reference load voltage. Moreover, a complete compensation scheme is proposed where load shedding is the secondary control variable. This control scheme is shown to stabilize different power system models

A Synthesis Method for Static Anti-Windup Compensators

Synthesis of static anti-windup compensators is considered. LMIconditions are established for stability and performance analysis of the closedloop system. The performance criterion describes the servo problem forthe resulting closed-loop piecewise linear system. The synthesisof the anti-windup compensators will be given by some bilinear matrix inequalities

ABS and Anti-skid on a LEGO car : A project in Embedded Systems

This work is the result of a course project in Embedded Systems. The goal was to implement a whee-slip control system on a LEGO car using a microcontroller. The car allows front-wheel or back-wheel driven configuration. Experimental results are presented for dry and wet surfaces

Synthesis of a Model-based Tire Slip Controller

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

A synthesis method for robust PID controllers for a class of uncertain systems

PID controller design is considered where optimal controllerparametersare found with constraint on maximum sensitivity and robustness withregard to a cone bounded static nonlinearity acting in feedback withpart of the plant. Thedesign procedure has been successfully applied in the synthesis of acontroller for an Anti-lock Braking System (ABS)

Performance Limitations in Vehicle Platoon Control

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 analyses 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

Performance limitations in vehicle platoon control

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\u27s phase area relation. Design guidelines are proposed and results from vehicle testing are presented

ABS control - A design model and control structure

The Anti-lock Braking System is an important component of acomplex steering system for the modern car. Most of ABS controllersavailable on the market are table and relay-feedback based.In the latest generation of “brake by wire” systems, the performancerequirements on the ABS are much higher. Control objective shiftsto maintain a specified tire slip during braking. The authors propose a design model and based on that a gain-scheduled controller that regulates the tire-slip. Simulation and test results are presented

All Aboard the Robotic Road Train

Public transportation has its own drawbacks: Buses and trains don\u27t start at your home and don\u27t end at your destination, nor do they leave just when you\u27d like or even guarantee you a seat. To get the best of both worlds, we could teach our cars to work together, as closely grouped cyclists do in a peloton. The lead car could be entrusted to a professional driver to whom the other drivers would of course each pay a small fee; all the other cars would follow it automatically. The cars would all use networked communications coupled with the optical or electromagnetic sensors already installed in some luxury cars to avoid head-on collision, stay in the proper lane, and brake in case of emergency. These systems have been developed at great expense to provide active safety, as distinguished from the passive kind afforded by seat belts. But this investment, having been made, can now be exploited for other things-like allowing you to relax and read the paper. If only we\u27d let them. Active systems are improving at a splendid rate. Adaptive cruise control, for example, maintains a car\u27s speed while using radar or lidar to keep a safe distance from the car in front of it, thus automating much of the braking and accelerating. The latest generation of this system can follow a lead car from highway speed to a stop and then resume automatically when that car drives away. Soon the system will get additional data from vision sensors and digitized maps and additional support for the steering, allowing it to slow down on curves