Greg Stewart

Hybrid decentralized control of large scale systems

Motivated by three applications which are under investigation at the Honeywell Research Laboratory in Minneapolis, we introduce a class of large scale control problems. In particular we show that a formation flight problem, a paper machine control problem and the coordination of cameras in a monitoring network can be cast into this class. In the second part of the paper we propose a decentralized control scheme to tackle the complexity of the problem. The scheme makes use of logic rules which improve stability and feasibility of the decentralized method by enforcing coordination. The decentralized control laws which respect the rules are computed using hybrid control design.

Brief paper: On the computation of linear model predictive control laws

Finite-time optimal control problems with quadratic performance index for linear systems with linear constraints can be transformed into Quadratic Programs (QPs). Model Predictive Control requires the on-line solution of such QPs. This can be obtained by using a QP solver or evaluating the associated explicit solution. The objective of this note is twofold. First, we shed some light on the computational complexity and storage demand of the two approaches when an active set QP solver is used. Second, we show the existence of alternative algorithms with a different tradeoff between memory and computational time. In particular, we present an algorithm which, for a certain class of systems, outperforms standard explicit solvers both in terms of memory and worst case computational time.

Toward a Systematic Design for Turbocharged Engine Control

The efficient development of high performance control is becoming more important and more challenging with ever tightening emissions legislation and increasingly complex engines. Many traditional industrial control design techniques have difficulty in addressing multivariable interactions among subsystems and are becoming a bottleneck in terms of development time. In this article we explore the requirements imposed on control design from a variety of sources: the physics of the engine, the embedded software limitations, the existing software hierarchy, and standard industrial control development processes. Decisions regarding the introduction of any new control paradigm must consider balancing this diverse set of requirements. In this context we then provide an overview of our work in developing a systematic approach to the design of optimal multivariable control for air handling in turbocharged engines.

Identification Techniques for Control Oriented Models of Internal Combustion Engines

The use of mathematical models is widespread in the design process of modern internal combustion engines. A driving factor for this trend is the rising complexity of engine systems due to tightening emission limits and increasing demands on fuel efficiency. This chapter focuses on control oriented models for turbocharged diesel engines which were specifically developed for use in an advanced model based control design process. A number of challenges had to be overcome to guarantee stability of these models both in simulation and during identification. The solutions for these issues are presented in this chapter together with an innovative identification approach which performs the calibration of the overall engine model on top of the previously executed identification of individual engine components. Example modeling results are included for a six cylinder commercial diesel engine with EGR and dual stage turbocharging.

On the Computation of Linear Model Predictive Control Laws

Finite-time optimal control problems with quadratic performance index for linear systems with linear constraints can be transformed into Quadratic Programs (QPs). Model Predictive Control requires the online solution of such QPs. This can be obtained by using a QP solver or evaluating the associated explicit solution. Objective of this note is to present alternative algorithms which trade off memory versus computational time differently than explicit solutions and active sets QP solvers.

Editorial To Tame the Wind: Advanced Control Applications in Wind Energy

The aim of this special section is to illustrate the potential of advanced control methods to improve wind power technologies, through a collection of contributions concerned with several aspects including mitigation of tower vibration and fatigue loads, wind preview control, estimation of rotor effective wind speed, identification of rotor dynamics, fault tolerant control, wind farm control, and airborne wind energy. A significant number of contributions in the section are concerned with mitigation of vibrations and load reduction of wind turbines, in different frameworks and with different actuators and control approaches.

How can we improve the outreach and impact of control science and engineering

The field of control has a long and distinguished history of achievements on intellectual and practical fronts. Prospects for the future of control are bright too, provided we can direct our skills and energies appropriately. Some traditionally strong application areas have become commoditized, but others provide new terrain where our expertise can help make a mark. Gaining recognition outside our core community has also been a constant challenge for control scientists and engineers. Whether it is because control is a “hidden technology” or because we are not good enough at marketing ourselves and our field (or, more likely, both), many of our contributions go unheralded. This session, co-sponsored by the IEEE CSS Task Force on Outreach, will discuss issues related to the outreach and impact of control. Past successes, the current state, and future prospects will be covered. Panelists will be asked to give brief remarks at the beginning of the session and we will engage the audience in an open discussion for the remaining time. This session will help provide input and direction to other activities (e.g., workshops) that are being planned to drive the “outreach and impact of controls” agenda forward. We anticipate a stimulating and provocative session and we invite all ACC attendees to observe and contribute. Box lunches will be provided (quantities are not unlimited, so come early!)