Design of feedback control systems for stable plants with saturating actuators

A systematic control design methodology is introduced for multi-input/multi-output stable open loop plants with multiple saturations. This new methodology is a substantial improvement over previous heuristic single-input/single-output approaches. The idea is to introduce a supervisor loop so that when the references and/or disturbances are sufficiently small, the control system operates linearly as designed. For signals large enough to cause saturations, the control law is modified in such a way as to ensure stability and to preserve, to the extent possible, the behavior of the linear control design. Key benefits of the methodology are: the modified compensator never produces saturating control signals, integrators and/or slow dynamics in the compensator never windup, the directional properties of the controls are maintained, and the closed loop system has certain guaranteed stability properties. The advantages of the new design methodology are illustrated in the simulation of an academic example and the simulation of the multivariable longitudinal control of a modified model of the F-8 aircraft

Design of feedback control systems for unstable plants with saturating actuators

Cover title.Includes bibliographical references.Support provided by the General Electric Corporate Research and Development Center. Support provided by the NASA Ames and Langley Research Centers. NAS/NAG 2-297by Petros Kapasouris, Michael Athans, Gunter Stein

Design of feedback control systems for stable plants with saturating actuators

Caption title.Bibliography: p. 37-38.Supported in part by the General Electric Corporate Research and Develoment Center. Supported in part by a grant from the NASA Ames and Langley Research Centers. NASA/NAG 2-297by Petros Kapasouris, Michael Athans, Gunter Stein

Multiplex PI-Control for Consensus in Networks of Heterogeneous Linear Agents

In this paper, we propose a multiplex proportional-integral approach, for solving consensus problems in networks of heterogeneous nodes dynamics affected by constant disturbances. The proportional and integral actions are deployed on two different layers across the network, each with its own topology. Sufficient conditions for convergence are derived that depend upon the structure of the network, the parameters characterizing the control layers and the node dynamics. The effectiveness of the theoretical results is illustrated using a power network model as a representative example.Comment: 13 pages, 6 Figures, Preprint submitted to Automatic

An Optimization approach to plant-controller co-design

Improving the behavior of a controlled mechanical device is traditionally accomplished by manipulating the parameters of the control system in isolation. If permitted, a better solution can be achieved by including the physical attributes of the mechanical structure as optimization variables. However, this expansion of the search space increases the importance of properly formulating the optimization problem to avoid undesirable behavior. Some modern (e.g. H∞) methods can be used to simultaneously optimize dynamic performance and robustness, but they require high levels of understanding and do not handle nonlinearities and arbitrary optimization constraints without additional augmentation. This work proposes and applies a method to add robustness to an optimized stabilizing controller and plant combination using constrained performance index optimization of chirp signal tracking. Using a chirp reference helps to improve the generality of the system response and ensures that resonant modes lay outside the useful range of input frequencies. Moreover, applying constraints on physical optimization parameters and their sensitivities helps to limit the solution space of a potentially high-dimensional problem while ensuring that the resultant system is both realizable and robust. An experimental platform for studying the process of toner ink fusion was modeled to demonstrate the effectiveness of the proposed method. For this system, combined optimization resulted in a performance index over 45% better than the result of optimizing the controller alone. Meanwhile, a worst-case robustness floor was maintained on several critical and uncertain system qualities

A feasibility study for reset control of an industrial batch reactor

Includes abstract.Includes bibliographical references (leaves 128-133).A feasibility study for the application of reset control to the temperature control loop of a pressurized exothermic batch leach reactor in the hydrometallurgical Precious Group Metals (PGM) industry is carried out. Keywords: Reset control; Clegg integrator; initial states; industrial batch reactor; temperature control; exothermic reactions; multiple reactions; dissolve; leach; hydrometallurgy; platinum; Precious Group Metals (PGMs)

Time-delay based output feedback control of fourth-order oscillatory systems

We consider robust stabilization of the fourth-order oscillatory systems with non-collocated output sensing. A novel yet simple control method is introduced based on the time-delayed output feedback. The delayed output feedback requires only the oscillation frequency to be known and allows for a robust control design with cancelation of the resonance peak. We use the stability margins to justify the transfer characteristics and robustness of the time-delay control in frequency domain. The main advantage of the proposed method, over the other possible lead-based loop shaping strategies, is that neither time derivatives of the noisy output nor implementation of any transfer functions are required for deploying the controller, that comes in favor of applications. An otherwise inherently instable proportional-integral (PI) feedback of the non-collocated output is shown to be stabilized by the proposed method. The control developed and associated analysis are also confirmed by the experimental results shown for the low damped two-mass oscillator system with uncertainties.Comment: 6 pages, 8 figure

Implications of laws of software evolution on continuing successful use of COTS software

However completely specified, integration of COTS software into real world systems makes it of type E even though, were it to be fully and absolutely specified, it would satisfy the definition of an S-type system. Thus, the laws of software evolution that apply to E-type systems are also relevant in the COTS context. This paper examines the wider implications of this fact and, in particular, that such systems must undergo continuing evolution. Managerial implications of the laws of software evolution in the context of COTS are also briefly highlighted

Robust output stabilization: improving performance via supervisory control

We analyze robust stability, in an input-output sense, of switched stable systems. The primary goal (and contribution) of this paper is to design switching strategies to guarantee that input-output stable systems remain so under switching. We propose two types of {\em supervisors}: dwell-time and hysteresis based. While our results are stated as tools of analysis they serve a clear purpose in design: to improve performance. In that respect, we illustrate the utility of our findings by concisely addressing a problem of observer design for Lur'e-type systems; in particular, we design a hybrid observer that ensures ``fast'' convergence with ``low'' overshoots. As a second application of our main results we use hybrid control in the context of synchronization of chaotic oscillators with the goal of reducing control effort; an originality of the hybrid control in this context with respect to other contributions in the area is that it exploits the structure and chaotic behavior (boundedness of solutions) of Lorenz oscillators.Comment: Short version submitted to IEEE TA