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This paper demonstrates a process by which multi-core processor thermal dynamics are modeled using a combination of commercially available high fidelity numerical simulators and system identification techniques. The process produces reduced order models suitable for Dynamic Thermal Management (DTM) controller designs. An example microprocessor package is provided to illustrate the technique. A simple DTM controller is developed and applied to the modeled system.

In this paper we consider the design and control of an airbreathing hypersonic vehicle. Such vehicles are characterized by non-minimum phase characteristics, instability, actuator saturation constraints, and lightly damped flexible modes. While traditional vehicle design has followed an iterative sequential procedure (with the controller design following an aero-centric vehicle design phase), an integrated vehicle-control design process (based on bilinear matrix inequalities) is considered in this paper. We consider several example problems to illustrate the advantages of such an approach.

This chapter contains sections titled: Introduction Direct Heuristic Dynamic Programming A Control Theoretic View on the Direct HDP Direct HDP Design with Improved Performance Case 1��-��Design Guided by a Priori LQR Information Direct HDP Design with Improved Performance Case 2��-��Direct HDP for Coorindated Damping Control of Low-Frequency Oscillation Summary References ]]>

Two robust controller designs are presented for a twin lift helicopter system (TLHS). The TLHS configuration consists of two UH-60A Sikorsky Blackhawk helicopters jointly lifting a heavy payload. The first design presented considers the case in which the tethers connecting each helicopter to the load are equal in length, and the second considers the case in which the tether lengths are unequal. Both designs are based on a seven degree of freedom model linearized about hover. The primary objective of each controller is to minimize the control action and pitching motion required to stabilize the helicopters as they perform elementary manuevers. Initial controllers developed by solving a mixed sensitivity H ∞ problem are analyzed for robustness to model uncertainty using the structured singular value μ and new controllers are developed which are more robust with respect to the uncertainty.

In this paper, three methods are presented to enhance the performance of an unstable missile system in the presence of multiple saturating actuators. Each method involves the design of a saturation detection system, which modifies a nominal autopilot via online optimization and maintains, to the extent possible, the multivariable properties of the nominal design. To prevent saturation due to exogenous signals, disturbances and noises, in particular, an error governor is proposed. This system processes the error signals within the feedback loop and the state of the compensator, so that appropriately co-ordinated control surface deflections may be generated. Traditionally, such a system has been applied only to stable plants. In this paper, it is shown how to design such a system for unstable plants. To prevent saturation due to reference (acceleration) commands from the guidance system, a reference governor is proposed. Such a system has traditionally required access to the entire state of the plant as wel...

In this paper we consider limits of achievable performance for a class of scramjet-powered hypersonic aircraft. A simple 3-DOF model is used to illustrate the main ideas. The vehicle is characterized by unstable and non-minimum phase dynamics. The limitations introduced by the right-half plane zero and actuator saturation on achievable trajectories has been examined. In addition, we examine several vehicle configurations and consider fundamental limitations for the plant and closed loop performance. An optimization methodology that explicitly incorporates performance specifications into the design of vehicle is explored. The advantages of such an approach is illustrated with examples.

This paper examines the issues involved in controlling an air-breathing hypersonic vehicle (characterized by their unstable, non-minimum phase dynamics) in the presence of significant modeling uncertainty and nonlinearities (control saturations). Modeling of the vehicle exhaust (plume) is complicated, often requiring computational fluid dynamic (CFD) simulations to capture all relevant effects. The focus of this paper is on obtaining a control law that maintains the vehicle trajectory within an acceptable tube while enforcing control constraints in the presence of modeling uncertainty. A robust domain of attraction based approach is used to generate/validate a feasible tube. The computational aspects of such an approach is examined, and the benefits of a decentralized control technique is considered. This approach is compared with other techniques such as linear matrix inequalities based controller design. These approaches are applied to a command following scenario in order to illustrate the performance of the proposed approach.

In this paper, two methods are presented to enhance the performance of unstable missile system in the presence of saturating actuators. Each method involves the design of a saturation detection system which modifies a nominal autopilot via on-line optimization and maintains, to the extent possible, the multivariable properties of the nominal design. Each method is applied to the problem of controlling an unstable bank-to-turn (BTT) missile.

In this paper, an overview is provided of control efforts implemented using the scramjetpowered hypersonic vehicle model developed by Bolender, Doman, et.al. (2005-2009). The nonlinear model is characterized by unstable non-minimum phase dynamics with aeroelastic-propulsion coupling and nonlinear propulsion constraints. The viability of simple inner-outer loop single-input single-output (SISO) control structures is examined and quantified. Reference command and control amplitude and bandwidth tradeoffs are addressed. A simple (non-scheduled ) inner-outer loop control law is shown to yield excellent tracking of a constant (q = 2076 psf) dynamic pressure guidance command profile from Mach 5.7 to Mach 12. Robustness, gain scheduling as well as multivariable control issues are also addressed.

Scramjet powered hypersonic vehicles represent the next critical step toward achieving NASA's vision for Highly Reliable Reusable Launch Systems (HRRLS), affordable space access, planetary re-entry systems, and global reach vehicles. The design of such vehicles is a very interdisciplinary and highly complex problem. As such, the development of varying fidelity mathematical models for assessing overall stability and performance during the design process is very important. In particular, developing “low-order” models with “sufficient fidelity” to capture control-centric phenomena becomes vital in early stages of vehicle design. Historically, the early stage vehicle design process never incorporated control related considerations. The design obtained by such practice is not optimal and can often lead to poor design from a stability and performance view point. This paper presents control-relevant modeling efforts which will facilitate quick iterative control analysis and design during early stages of vehicle design. The paper is intended to be of an introductory nature and presents the high level modeling framework and associated challenges. An example linear 6 DOF model with some representative analysis is also given to demonstrate the applicability of the tool suite.

In many applications, it is essential to limit control signals. This paper presents methods that process accessible system signals (e.g., plant and compensator states, reference commands) to limit control signals. In contrast to "classical techniques" which limit variables by unnecessarily reducing control system bandwidth, the proposed methods limit variables in a nonconservative manner, reducing bandwidth only when necessary. A fundamental contribution of this work is that the methods presented are applicable to linear parameter varying (LPV) and quasi-LPV plants and controllers. The methods presented rely on appropriately "scaling back" key signals. The methods are conservative in that they are applicable to "slowly varying" LPV systems. Although the methods require access to all internal closed loop system state variables, one could use an appropriately designed LPV state estimator, if necessary. The Error Governer (EG) methods are applied to an LPV missile autopilot example.

In this paper, a method is presented for enhancing the performance of a stable EMRAAT bank-to-turn (BTT) missile in the presence of multiple saturating actuators. The method involves the design of a saturation detection system, called an error governor which maintains, to the extent possible, the multivariable properties of the original autopilot design. The system prevents saturation, ensures finite-gain L/sup /spl infin// stability, and maintains, to the extent possible, the directionality properties of the original autopilot.

In this paper, a method is presented for enhancing the performance of an unstable missile system in the presence of multiple saturating actuators. The method involves the design of it saturation detection system which modifies a nominal autopilot via online optimization and maintains, to the extent possible, the multivariable properties of the nominal design. The method relies on missile state estimates.

environments which revolutionize systems and controls analysis, design, research, and education. The This paper describes the application of the Model- authors have exploited these technologies to develop ing, Simulation, Animation, and Real-Time Control several system-specific environments for a variety of (MoSART) Flezible Inverted Pendulum Environment systems [l], (31, [4], [5], [61. to the study of rigid link approximations to the flexible invcrted pendulum. The MoSART environment ,-.ontributions of work, ~h~~ paper denionstrates is used to visualize the system dynamics of different how inexpensive state-of-the-art pc may rigid link models and to evaluate the performance of be combined to develop high quality M~SA~T control systems. Controller designs for simpler rigid vironnlents which are useful for enhancing the rependulums o' fewer Hexible modes be applied t' search and education process. Specifically, this paper pendulum models including additional Heaible modes describes a pc/windows 95/98/~~/2000/~~ / viin order to investigate the limitation of controller sual C++/MATLAB, Simulink.based M~SART plezdesign. Additionally, these rigid link models allow ibk Inverted Pendulum E~~~~~~~~~~ comparison to approximation techniques for infinite ment Dermits control svstem researcher and students dimensional system models of flexible inverted pen- to analyae, design, and visualize the performance of dulums. The inverted electromechanical systems under control via real-time Pendulum Envaronnient is a valuable tool for enhanc- faster-than-real.time animation, ing both research and education. Through a user-friendly graphical interface, users

The design of a decoupling compensator for the Apache helicopter is presented. The design is based on linear quadratic regulation with implicit model following. A decoupling compensator is designed for a reduced-order linear model of vehicle dynamics at hover using eigenstructure assignment. The resulting closed-loop system is used as a reference model in the design of a compensator for the full-order system, resulting in a constant state feedback matrix. A feedforward matrix (command mixer) is then designed to diagonalize the system at low frequencies. The design is evaluated with both the full-order linear model and a nonlinear simulation, ARMCOP. It is found to provide desired bandwidth and good decoupling properties with the linear model. The nonlinear simulation shows increased coupling due to the nonlinearities.

In this paper, a method is presented for governing the release of wafers (starts) into a re-entrant semiconductor fabrication line. A flow model for a five-machine six-step re-entrant mini-fab is used to present all developments. Stabilizing clear-a-fraction (CAF) state feedback policies are developed for the mini-fab. A systematic procedure is presented for regulating the flow of starts so that critical system constraints (e.g. machine availability and buffer level constraints, etc.) are never violated, however aggressive the release policy. The regulation is achieved via nonlinear optimization based on state information from the flow model. The resulting algorithm, called a release policy governor (RPG), is shown to produce a closed loop stable system.

The motivation for the work is aircraft guidance in a time controlled air traffic management system (ATM). This paper discusses two forms of optimal dynamic interpolation guidance (ODIG) and the effects of turbulence on its performance. The first form of ODIG is based on a cost functional that penalizes acceleration. The second form of ODIG penalizes both acceleration and velocaty excursion. Both have been applied to the L1011-100 vertical guidance problem in the presence of turbulence (the Dryden turbulence model was used). A flight management system's (FMS) vertical flight plan is used to obtain waypoints which serve as inputs to the ODIG algorithm. The algorithm produces reference commands which are issued to a certified FAA L1011-100 model and an autopilot. The resulting dynamic behavior is compared to the results obtained from reference commands produced by an L1011-like commercial aircaft's flight management system model (FMSM) under the same turbulence.

In this paper, dynamic interpolation is applied to an L1011-100 vertical guidance problem. A flight management system's (FMS) optimized vertical flight plan is used to obtain way points which serve as inputs to the dynamic interpolation algorithm. The algorithm produces reference commands which are issued to a model obtained from a certified FAA L1011-100 and autopilot. The resulting dynamic behavior is compared to the results obtained from reference commands produced by an L1011-like commercial aircraft FMS. Quadratic and cubic spline solutions to the dynamic interpolation problem are presented. Performance degradation with respect to weight uncertainty is examined for both the FMS and the Dynamic Interpolation commands.

This paper presents guidelines for developing a multivariable centralized automatic flight control system (AFCS) for a twin lift helicopter system (TLHS). Singular value ideas are used to formulate performarce and stability robustness specifications. A Linear-Quadratic-Gaussian with Loop Transfer Recovery (LQG/LTR) design is obtained and evaluated.