Andrew W. Osburn

Designing Robust Repetitive Controllers

A method for designing repetitive feedback controllers using nonparametric frequency response plant models is developed. In comparison to the zero-phase-error (ZPE) controller (ASME J. Dyn. Syst. Meas. Control, 111, pp. 353-358), this method has the added benefit of providing improved transient performance when the plant inverse is unstable. In this controller design process, a connection is made between model uncertainty and the desired frequency response of the so-called q filter. Also, it will be shown that an optimal equiripple filter is useful when designing high-order q filters. The entire process was experimentally verified on an engine control application. A repetitive controller was used to determine the dynamic fueling requirements of a fuel injected, spark-ignition engine subjected to periodic changes in the throttle position. This fueling information is necessary when designing feedforward fueling algorithms.

Transient Air/Fuel Ratio Controller Identification Using Repetitive Control

Presented in this paper is a feedforward controller identification process for the transient fueling control of spark ignition (SI) engines. The objective of an SI fueling control system is to guarantee a prespecified air-fuel (A/F) ratio, despite changing driver demands commanded through the throttle. The controller identification process is based on standard system identification tools and is comprised of three steps. The first step involves the design and implementation of a repetitive feedback controller. Next, the engine is subjected to a prespecified periodic throttle motion for which the repetitive controller achieves precise A/F control as t→∞. Finally, using the engine speed, the mass air flow, and the fuel pulsewidth information during precise fueling conditions, the feedforward fueling controller is identified using standard parametric system identification tools. This identification process can be performed during engine warm-up, thereby enabling a rapid determination of the fueling requirements as a function of temperature. Experimental validation is provided on a 1999 Ford 4.6L V-8 fuel injected engine with sequential port injection.

Reducing engine idle speed deviations using the internal model principle

Presented in this paper is a multivariable linear feedback controller design methodology for idle speed control of spark-ignition engines. The engine is modeled as a multi-input, single-output system. The proposed feedback control system employs both throttle and ignition timing to control engine speed and engine roughness. Throttle is used to attenuate low frequency components of the speed error and reject mean speed errors. Spark advance is used to reduce cylinder-to-cylinder differences in torque production by limiting high frequency speed deviations. The algorithm is executed in the crank-angle domain, and the internal model principle serves as the basis for cylinder torque balancing. The nonlinear relationship between ignition timing and torque production is explicitly incorporated into the design process using a sector bound. A loop shaping approach is proposed to design the feedback controller, and absolute stability of the nonlinear closed-loop system is guaranteed through the Tsypkin Criterion. Experimental results from implementation on a Ford 4.6L V-8 engine are provided.

Data Driven Feedforward Transient Fueling Controller Identification for Spark Ignition Engines

Presented in this paper is a feedforward fueling controller identification methodology for the transient fueling control of spark ignition (SI) engines. The proposed transient feedforward controller is identified and executed in the crank angle domain, and operates in tandem with a steady state fueling controller. The hypothesis is that the feedforward fueling control of SI engines can be separated into steady state and transient phenomena, and that the majority of the nonlinear behavior associated with engine fueling can be captured with nonlinear steady state compensation. The proposed transient controller identification process is built from standard nonparametric identification techniques using spectral density functions where crank angle serves as the independent variable. Two separate system identification problems are solved to identify the air path dynamics and the fuel path dynamics. The transient feedforward controller is then calculated as the ratio of the air path-over-the fuel path dynamics so that the fuel path dynamics match the air path dynamics. Consequently fueling is coordinated with the fresh air charge during transient conditions. It will be shown that a linear transient feedforward-fueling controller operating in tandem with a nonlinear steady state fueling controller can achieve air-fuel ratio (AFR) regulation comparable to a production controller without the extensive controller calibration process. The engine used in this investigation is a 1999 Ford 4.6L V-8 fuel injected engine.Copyright