Richard T. O'Brien

Vehicle lateral control for automated highway systems

This paper addresses the modeling and control of the lateral motion of a highway vehicle. In particular, a steering controller is designed that tracks the center of the present lane on both curved and straight highway sections without knowledge of the radius of curvature of the road. Also, it is shown that a lane change maneuver can be completed on a curved road section using this controller. The controller is designed using an H/sub /spl infin//-based loop shaping design procedure due to McFarlane and Glover. It is shown that this controller achieves the required performance as well as exhibiting excellent robustness. In particular, the controllers robustness due to varying speeds, icy road conditions, and wind gusts are examined.

On the poles and zeros of linear, time-varying systems

Definition of poles and zeros are presented for continuous-time, linear, time-varying systems. For a linear, time-varying state equation, a set of time-varying poles defines a stability-preserving variable change relating the original state equation to an upper triangular state equation. A zero is a function of time corresponding to an exponential input whose transmission to the output is blocked. Both definitions are shown to be generalizations of existing definitions of poles and zeros for linear, time-varying systems and are consistent with the definitions for linear, time-invariant systems. A computation procedure is presented using a QR decomposition of the transition matrix for the state equation. A numerical example is given to illustrate this procedure.

A Unified Procedure for Continuous-Time and Discrete-time Root-Locus and Bode Design

As an alternative to the numerous distinct controller design algorithms in continuous-time and discrete-time classical control textbooks, a simple, unified design approach is presented for all standard continuous-time and discrete-time, classical compensators that is independent of the form of the linear system information. This approach is based on a simple root locus design procedure for a proportional-derivative (PD) compensator. From this procedure, design procedures for unified notation lead, proportional-integral (PI), proportional-integral-derivative (PID), and Pi-lead compensator are developed. The delta operator, which serves as a link between the continuous-time and discrete-time procedures, offers improved numerical properties to the traditional discrete - time shift operator. With this proposed approach, designers can concentrate on the larger control system design issues, such as compensator selection and closed-loop performance, rather than the intricacies of a particular design procedure.

Scale-model vehicle analysis for the design of a steering controller

A scale-model vehicle is developed that is dynamically similar to a full-size vehicle through application of the Buckingham-Pi theorem. Specifically, the vehicle is modified to match the corresponding Pi groups of the scale-model vehicle and the average of a number of full-size vehicles. The modifications require the mass of the vehicle and its distribution to be changed. Furthermore, an experimental apparatus is designed and built to measure the cornering stiffness of scale-model tires. Experimental data for the vehicle is compared to data for a number of full-size vehicles.

/spl Hscr//sub /spl infin// active noise control of fan noise in an acoustic duct

In this paper, the problem of reducing fan related noise in an acoustic duct is considered. By installing magnetic bearings on the noise producing machinery, it is possible to collocate the anti-noise source with the disturbance noise source. This approach allows for global noise reduction through out the duct system. Using /spl Hscr//sub /spl infin// control theory, an active noise controller is designed that attains broadband as well as tonal noise reduction at all points along the duct. The controller design is based on a state space model identified from an infinite dimensional physical model. Simulation results demonstrate the global nature of this novel active noise control approach.

A unified procedure for discrete-time root locus and Bode design

As an alternative to the numerous distinct controller design algorithms in discrete-time textbooks, a simple, unified design approach is presented for all standard discrete-time, classical compensators independent of the form of the system information. This approach is based on a simple root locus design procedure for a proportional-derivative (PD) compensator. From this procedure, design procedures for discrete-time lead, proportional-integral (PI), lag, proportional-integral-derivative (PID), and PI-lead compensators are developed. With this proposed approach, students can concentrate on the larger control system design issues, such as compensator selection and closed-loop performance, rather than the intricacies of a particular design procedure. To demonstrate this approach, an example of a lead design from a digital control system laboratory is presented.

Vehicle lateral control using a double integrator control strategy

In this paper, a bang-bang control algorithm developed for double integrator systems is applied to the problem of automated vehicle steering control. This research is part of an on-going project on vehicle control using scale-model vehicle simulator. The controller uses pre-determined, piecewise constant control signals to shape the lateral position and yaw angle responses. Simulation results demonstrate that the proposed control algorithm maintains acceptable performance despite the unmodeled dynamics.

Steering controller design using scale-model vehicles

A scale-model, experimental apparatus is developed to design and evaluate steering controller designs. The controller is designed using linear quadratic optimal control methods on a standard four-state vehicle model. The apparatus simulates the human driver using a scale-model vehicle, a treadmill, and a vision system.

Bang-bang control for type-2 systems

A sampled-data, bang-bang control algorithm developed for a double integrator plant is extended to higher-order plants with two integrators. In the case where nonintegrator dynamics are considered unmodeled, the robustness of the control algorithm is analyzed. In the case where nonintegrator dynamics are modeled, the control algorithm design procedure is generalized to incorporate the additional dynamics. Both approaches are examined through the design and simulation of a steering controller for an autonomous ground vehicle

Optimal PID controller design using standard optimal control techniques

An optimal PID controller design procedure is formulated for 2nd order systems where the computation of the PID gains is equivalent to a state feedback design problem. As a result, any optimal state feedback control design method can be used. Furthermore, this method can be extended to higher order systems using model reduction techniques. The procedure is verified experimentally using a ball and beam apparatus.