Bonnie S. Heck

Software technology for implementing reusable, distributed control systems

A tutorial overview of software innovations for implementing, and facilitating the reuse of, complex control systems. The article focuses on distributed control with multiple processors.

Sliding-mode control for singularly perturbed systems

This paper addresses the design of sliding-mode controllers for singularly perturbed systems. The full-order system is separated into slow and fast subsystems and a sliding-mode controller is designed for each subsystem. A composite of these controls is then implemented on the full-order system. It is shown that if specific reaching conditions are satisfied for the reduced-order models and an additional condition is met, then the reaching conditions are also satisfied for the full-order model. Furthermore, sufficient conditions are derived which guarantee that the approximation error between the controlled reduced-order response and the controlled full-order model response is small. A numerical example is given which successfully demonstrates the techniques developed in this paper.

Numerical methods to design the reaching phase of output feedback variable structure control

Abstract Two numerical methods are developed to design a variable structure control that satisfies the reaching condition using static output feedback. The design is formulated as a nonsmooth convex optimization problem for which existing algorithms are available. It is shown how the resulting control law can be modified to be robust in the presence of parameter uncertainty or a disturbance. Numerical examples successfully demonstrate the developed techniques.

Bilinear discrete-time modeling for enhanced stability prediction and digital control design

This paper presents a new bilinear discrete-time modeling method for switching power converter circuits. The method utilizes a new approximation of the matrix exponential involved in the exact discrete-time models. Compared to the conventional bilinear discrete-time models or to the continuous-time averaged models, the new bilinear models provide a means for more reliable and accurate stability and transient response prediction. They also lend themselves better to digital control design than do the exact discrete-time models due to their simplicity. The modeling method is validated by several example converters, for which traditional averaged models and conventional bilinear discrete-time models fail to predict the stability characteristics correctly.

Distributed unique global ID assignment for sensor networks

A sensor network consists of a set of battery-powered nodes, which collaborate to perform sensing tasks in a given environment. It may contain one or more base stations to collect sensed data and possibly relay it to a central processing and storage system. These networks are characterized by scarcity of resources, in particular the available energy. We present a distributed algorithm to solve the unique ID assignment problem. The proposed solution starts by assigning long unique IDs and organizing nodes in a tree structure. This tree structure is used to compute the size of the network. Then, unique IDs are assigned using the minimum number of bytes. Globally unique IDs are useful in providing many network functions, e.g. configuration, monitoring of individual nodes, and various security mechanisms. Theoretical and simulation analysis of the proposed solution have been preformed. The results demonstrate that a high percentage of nodes (more than 99%) are assigned globally unique IDs at the termination of the algorithm when the algorithm parameters are set properly. Furthermore, the algorithm terminates in a relatively short time that scales well with the network size. For example, the algorithm terminates in about 5 minutes for a network of 1,000 nodes

Transition management for reconfigurable hybrid control systems

This article presents a framework for managing transitions between discrete states in hybrid control systems. Based on a study of how hybrid controls are designed and implemented, the authors have identified generic software patterns that are customizable yet can transparently handle common needs for component integration and reconfiguration.

Simulation of large-scale sensor networks using GTSNetS

We present a sensor network simulation environment that allows users to evaluate the effects of different architectural choices and strategies on the lifetime and performance of a sensor network. Our tool can also be used to evaluate new approaches (routing protocols, cooperation algorithms), and compare them with the ones already in place. This simulator is an extension of the Georgia Tech Network Simulator (GTNetS) and leverages its design choices for maximum performance. It incorporates models for the different functional units composing a sensor node and characterizes the energy consumption of each. It also has a model for a network base station and its interactions with the rest of the network. We report our results from a set of tests that demonstrate some of the capabilities of our simulator. In particular, we were able to simulate sensor networks of several hundred thousand nodes while using less than 2 GB of memory, which exceeds the capabilities of existing simulators by an order of magnitude. The simulator is also used to study the performance of an algorithm that assigns globally unique IDs to nodes in a sensor network.

An open software infrastructure for reconfigurable control systems

Recent advances in software technology have the potential to revolutionize control system design. This paper describes a new software infrastructure for complex control systems, which exploits new and emerging software technologies. It presents an open control platform (OCP) for complex systems, including those that must be reconfigured or customized in real-time for extreme-performance applications. An application of the OCP to the control system design of an autonomous aerial vehicle is described.

Enhancing classical controls education via interactive GUI design

This column presents a graphical and somewhat automated tool for performing the iteration when using classical control design methods. The graphical user interface is an easy way for students to see the effect of the gain and the compensator pole-zero locations on the closed loop step response. Thus, the tool presented extends the capabilities of classical control design methods as they are currently presented in textbooks. Three examples are given that demonstrate the use and effectiveness of this tool. Furthermore, the Bode plot and the root locus windows are tied together in such a way that students can see how changes to the root locus affect the open loop Bode plot and vice versa.

A LEGO experiment for embedded control system design

This article describes a simple, portable, yet effective experimental setup for use in courses that do not have dedicated laboratory facilities. Since the setup is based on LEGO parts and equipment, the experiment can be developed easily and relatively inexpensively. When combined with NQC freeware, students are exposed to programming embedded processors. Students also gain experience with the implementation of dynamic controllers and with non-ideal and nonlinear features present in real-world mechatronic systems. The experiment is especially effective when used for projects in introductory signals, systems, and controls courses.