Understanding robust control theory via stick balancing

Robust control theory studies the effect of noise, disturbances, and other uncertainty on system performance. Despite growing recognition across science and engineering that robustness and efficiency tradeoffs dominate the evolution and design of complex systems, the use of robust control theory remains limited, partly because the mathematics involved is relatively inaccessible to nonexperts, and the important concepts have been inexplicable without a fairly rich mathematics background. This paper aims to begin changing that by presenting the most essential concepts in robust control using human stick balancing, a simple case study popular in both the sensorimotor control literature and extremely familiar to engineers. With minimal and familiar models and mathematics, we can explore the impact of unstable poles and zeros, delays, and noise, which can then be easily verified with simple experiments using a standard extensible pointer. Despite its simplicity, this case study has extremes of robustness and fragility that are initially counter-intuitive but for which simple mathematics and experiments are clear and compelling. The theory used here has been well-known for many decades, and the cart-pendulum example is a standard in undergrad controls courses, yet a careful reconsidering of both leads to striking new insights that we argue are of great pedagogical value

Network Centric Operations and the Brigade Unit of Action: A System Dynamics Perspective

In the midst of fighting a global War on Terror, the U.S. Army is concurrently attempting to transform to a more agile and deployable organization, which is centered largely on the integration of new information technologies into its command posts. While most Army leaders are reporting that many of these new information “tools” such as the Army Battle Command System (ABCS) give them an unprecedented level of situational awareness and are beginning to enable a new style of war labeled by some as Network Centric Warfare, other leaders are reporting that the integration of this new digital technology comes with some unintended consequences that in some cases actually slows and decreases the quality of information flow by orders of magnitude. We studied the “Brigade Unit of Action” concept with specific emphasis on the Brigade’s ability to disseminate and process information within and between command posts, using System Dynamics as a modeling tool to help better understand the impact of various policy decisions made by the U.S. Army. Our study concentrated on some of the possible strengths and pitfalls of NCW theory, and led to the formulation of five heuristics that Army leaders should consider when developing the future command and control architecture for the Brigade Unit of Action

The Impact of GSS on an Organization\u27s Information Accessibility

In recent years, there has been a resurgence of interest in groups in business and other organizations. Concepts such as interactive meetings, empowered work teams, participative management, and total quality management have altered the dynamics and significance of group work within organizations (Finley 1992; Hunt 1993). Most managers agree that both formal and ad hoc groups significantly influence the behavior of individuals in larger organizations in which they work. The impactof groups on the organization is so pervasive that rarely will managers spend an entire day without attending at least one group meeting (White and Bednar 1991). Drucker (1988) suggested that the new organization would consist of groups of knowledge specialists and that the traditional command and control organization was on the way out. According to Finley (1992), the new ethic for success in business is that every person has to contribute to team decisions. This focus on teams has provided a challenge to information system (IS) specialists as far as providing necessary facilitative technology to fulfill the needs of companies focusing on groups and group work. George, Nunamaker, and Valacich (1992) suggested that one of the most promising trends for the IS field was this focus on groups and group work. The technology that supports the group decision making process has been referred to as group support systems. Most of the research in the GSS area has focused on decision room technology and most of this research has focused on theoretical, conceptual, and empirical research concerned with the design, implementation, and impact on the group process and outcomes (cf, Jelassi and Beauclair 1987, Gray 1987, DeSanctis and Gallupe 1985, Gallupe and McKeen 1990). Little research has been conducted concerning the impact of decision room use on the organization; specifically how the use of decision room use impacts the organization\u27s design, its nature, and its decision making process. In 1993, Huber, Valacich,and Jessup, proposed a theory for the impact of GSS on an organization. Their theory consisted of four concepts: a) availability of GSS leads to use of GSS;b) use of GSS leads to increased information accessibility;c) increased information accessibility leads to changes in organizational design;d) increased information accessibility and changes in organizational design lead to improvements in the effectiveness of intelligence development and decision makin

Supply function equilibrium analysis for electricity markets

The research presented in this Thesis investigates the strategic behaviour of generating firms in bid-based electricity pool markets and the effects of control methods and network features on the electricity market outcome by utilising the AC network model to represent the electric grid. A market equilibrium algorithm has been implemented to represent the bi-level market problem for social welfare maximization from the system operator and utility assets optimisation from the strategic market participants, based on the primal-dual interior point method. The strategic interactions in the market are modelled using supply function equilibrium theory and the optimum strategies are determined by parameterization of the marginal cost functions of the generating units. The AC power network model explicitly represents the active and reactive power flows and various network components and control functions. The market analysis examines the relation between market power and AC networks, while the different parameterization methods for the supply function bids are also investigated. The first part of the market analysis focuses on the effects of particular characteristics of the AC network on the interactions between the strategic generating firms, which directly affect the electricity market outcome. In particular, the examined topics include the impact of transformer tap-ratio control, reactive power control, different locations for a new entry’s generating unit in the system, and introduction of photovoltaic solar power production in the pool market by considering its dependencyon the applied solar irradiance. The observations on the numerical results have shown that their impact on the market is significant and the employment of AC network representation is required for reliable market outcome predictions and for a better understanding of the strategic behaviour as it depends on the topology of the system. The analysis that examines the supply function parameterizations has shown that the resulting market solutions from the different parameterization methods can be very similar or differ substantially, depending on the presence and level of network congestion and on the size and complexity of the examined system. Furthermore, the convergence performance of the implemented market algorithm has been examined and proven to exhibit superior computational efficiency, being able to provide market solutions for large complex AC systems with multiple asymmetric firms, providing the opportunity for applications on practical electricity markets