The Experts below are selected from a list of 141 Experts worldwide ranked by ideXlab platform

Asok Ray - One of the best experts on this subject based on the ideXlab platform.

  • Integrated decision and Control of human-engineered complex systems
    International Journal of General Systems, 2006
    Co-Authors: D.k. Tolani, Asok Ray, Joseph F. Horn
    Abstract:

    This paper presents a comprehensive decision and Control strategy for human-engineered complex systems to achieve simultaneously the following objectives: (i) high-performance with quality assurance; (ii) reliability and structural durability with extended service life and (iii) operability over a wide range. Results from several systems-theoretic disciplines, such as probabilistic robust Control (PRC), damage Mitigating Control (DMC), health and usage monitoring (HUM) and discrete event supervisory (DES) decision and Control have been synergistically combined to achieve the above goal. The proposed decision and Control system is hierarchically structured with two-tier architecture. The lower tier incorporates continuously-varying Control that is designed using a combination of PRC and DMC, and the upper tier is designed to provide information and intelligence through DES decision and Control that monitors the system response for detection and mitigation of anomalous behaviour, performance degradation and...

  • Hierarchical Control of Rotorcraft for Enhanced Performance and Structural Durability
    AIAA Guidance Navigation and Control Conference and Exhibit, 2005
    Co-Authors: D.k. Tolani, Joseph F. Horn, Murat Yasar, Asok Ray
    Abstract:

    This paper presents a hierarchical Control law architecture for future generation rotorcraft for enhanced performance (i.e., handling qualities) and structural durability. The proposed Control system has a two-tier hierarchical architecture. The lower-tier is designed using a combination of probabilistic robust Control and damage Mitigating Control methodologies. By allowing different levels of risk under different flight conditions, probabilistic robust Control achieves the desired trade off between stability, robustness and nominal performance. Minimization of damage rate is achieved via damage Mitigating Control, improving health management and durability of the rotorcraft. The upper-tier is designed using discrete-event supervisory Control methodology, which monitors the system response for any anomalous behavior, performance degradation and/or potential loss of structural durability. Based on the observed data, the upper-tier supervisor may decide to switch between different modes to satisfy the specified requirements. The system is demonstrated using a high fidelity simulation of the UH-60A helicopter.

  • Fuzzy damage-Mitigating Control of a fossil power plant
    IEEE Transactions on Control Systems Technology, 2001
    Co-Authors: M. Holmes, Asok Ray
    Abstract:

    Presents the architecture and synthesis of a damage-Mitigating Control system where the objective is to achieve high performance with increased reliability, availability, component durability, and maintainability. The proposed Control system has a two-tier structure. In the lower tier, a linear robust sampled-data Controller tracks a reference trajectory vector while the upper tier contains a fuzzy-logic-based damage Controller that makes a tradeoff between system dynamic performance and structural durability in critical component(s). The synthesis procedure is demonstrated on the model of a commercial-scale fossil-fueled power plant under load-following operation. Simulation experiments are designed to explore the feasibility of real-time fuzzy damage-Mitigating Control in fossil power plants, and the results show that substantial gain in structural durability of a critical component can be achieved with no significant loss of performance.

  • Damage-Mitigating Control of aircraft for enhanced structural durability
    IEEE Transactions on Aerospace and Electronic Systems, 2001
    Co-Authors: J. Caplin, Asok Ray, Suresh M. Joshi
    Abstract:

    The concept and a design methodology for robust damage-Mitigating Control (DMC) of aircraft is presented. The goal of DMC is to simultaneously achieve high performance and structural durability and the design procedure is based on damage mitigation at critical structures and retention of the flight performance. An aeroelastic model of the wings has been formulated and is incorporated into a nonlinear rigid-body model of aircraft flight-dynamics. Robust damage-Mitigating Controllers are then designed using the H/sub /spl infin//-based structured singular value (/spl mu/) synthesis method based on a linearized model of the aircraft. In addition to penalizing the error between the ideal performance and the actual performance of the aircraft, frequency-dependent weights are placed on the strain amplitude at the root of each wing, Using each Controller in turn, the Control system is put through an identical sequence of maneuvers, and the resulting (varying amplitude cyclic) stress profiles are analyzed using a fatigue crack growth model that incorporates the effects of varying-amplitude cyclic loading. Comparisons are made to determine the impact of different strain-amplitude weights on the resulting flight performance and fatigue crack damage in the wings. The results of simulation experiments show significant savings in fatigue life of the wings while retaining the dynamic performance of the aircraft.

  • Damage Mitigating Controller design for structural durability
    IEEE Transactions on Control Systems Technology, 1999
    Co-Authors: Ravindra Patankar, Asok Ray
    Abstract:

    Synthesis of a damage-Mitigating Control law requires additional information on damage states beyond what is needed for the design of a conventional output feedback Controller. In this context, the paper establishes the necessity of a fatigue damage model that must account for the impact of variable-amplitude stress excitation on crack growth rate (e.g., crack retardation and sequence effects). It is shown that predicted structural durability and the damage-Mitigating Controller design could be grossly inaccurate if the fatigue crack damage model does not represent the effects of variable-amplitude cyclic stress. A specific example is given based on the design of output-feedback damage-Mitigating Controllers for a reusable rocket engine that was reported in an earlier publication. Simulation results are presented to compare the predicted structural durability and closed-loop performance of the rocket engine under the same Controllers for two different damage models, with and without consideration of the effects of variable-amplitude stress.

Marc Carpino - One of the best experts on this subject based on the ideXlab platform.

  • Damage-Mitigating Control of mechanical structures: experimental verification of the concept
    Smart Materials and Structures, 1995
    Co-Authors: S. Tangirala, Asok Ray, Marc Carpino
    Abstract:

    The concept of damage-Mitigating Control is built upon the two disciplines of systems science and the mechanics of materials, and its goal is to achieve an optimized trade-off between the dynamic performance and structural durability of the plant under Control. Simulation studies reported in recent publications show a substantial reduction of damage accumulation in the critical components of a rocket engine with no significant loss of performance. This paper reports an experimental verification of the damage-Mitigating Control concept on a laboratory testbed, which is a two-degree-of-freedom mechanical system excited by a computer-Controlled shaker table. Test results demonstrate: (i) the important feature of optimized damage-Mitigating Control by extending the fatigue life up to 3 1/2 times with no significant performance degradation; and (ii) close agreement between the analytical prediction of damage and the experimental observations.

  • Damage-Mitigating Control of Mechanical Systems: Part II—Formulation of an Optimal Policy and Simulation
    Journal of Dynamic Systems Measurement and Control, 1994
    Co-Authors: Asok Ray, Marc Carpino, Carl F Lorenzo
    Abstract:

    The objective of damage-Mitigating Control introduced in the first part of this two-part paper is to achieve high performance without overstraining the mechanical structures. The major benefits its an increase in the functional life of critical plant components along with enhanced safety, operational reliability, and availability. Specifically, a methodology for modeling fatigue damage has been developed as an augmentation to Control and diagnostics of complex dynamic processes such as advanced aircraft, spacecraft, and power plants

  • Damage-Mitigating Control of Mechanical Systems: Part I—Conceptual Development and Model Formulation
    Journal of Dynamic Systems Measurement and Control, 1994
    Co-Authors: Asok Ray, Marc Carpino, Carl F Lorenzo
    Abstract:

    A major goal in the Control of complex mechanical systems such as advanced aircraft, spacecraft, and power plants is to achieve high performance with increased reliability, availability, component durability, and maintainability. The current state-of-the-art of Control systems synthesis focuses on improving performance and diagnostic capabilities under constraints that often do not adequately represent the dynamic properties of the materials. The reason is that the traditional design is based upon the assumption of conventional materials with invariant characteristics. In view of high performance requirements and availability of improved materials, the lack of appropriate knowledge about the properties of these materials will lead to either less than achievable performance due to overly conservative design, or over-straining of the structure leading to unexpected failures and drastic reduction of the service life. The key idea of the research reported in this paper is that a significant improvement in service life can be achieved by a small reduction in the system dynamic performance. This requires augmentation of the current system-theoretic techniques for synthesis of decision and Control laws with governing equations and inequality constraints that would model the properties of the materials for the purpose of damage representation and failure prognosis. The major challenge in this research is to characterize the damage generation process in a continuous-time setting, and then utilize this information for synthesizing algorithms of robust Control, diagnostics, and risk assessment in complex mechanical systems. Damage mitigation for Control of mechanical systems is reported in the two-part paper. The concept of damage mitigation is introduced and a continuous-time model of fatigue damage dynamics is formulated in this paper which is the first part. The second part which is a companion paper presents the synthesis of the open-loop Control policy and the results of simulation experiments for transient operations of a reusable rocket engine.

  • damage Mitigating Control of mechanical systems part i conceptual development and model formulation
    Journal of Dynamic Systems Measurement and Control-transactions of The Asme, 1994
    Co-Authors: Asok Ray, Marc Carpino, Carl F Lorenzo
    Abstract:

    A major goal in the Control of complex mechanical systems such as advanced aircraft, spacecraft, and power plants is to achieve high performance with increased reliability, availability, component durability, and maintainability. The current state-of-the-art of Control systems synthesis focuses on improving performance and diagnostic capabilities under constraints that often do not adequately represent the dynamic properties of the materials. The reason is that the traditional design is based upon the assumption of conventional materials with invariant characteristics. In view of high performance requirements and availability of improved materials, the lack of appropriate knowledge about the properties of these materials will lead to either less than achievable performance due to overly conservative design, or over-straining of the structure leading to unexpected failures and drastic reduction of the service life. The key idea of the research reported in this paper is that a significant improvement in service life can be achieved by a small reduction in the system dynamic performance. This requires augmentation of the current system-theoretic techniques for synthesis of decision and Control laws with governing equations and inequality constraints that would model the properties of the materials for the purpose of damage representation and failure prognosis. The major challenge in this research is to characterize the damage generation process in a continuous-time setting, and then utilize this information for synthesizing algorithms of robust Control, diagnostics, and risk assessment in complex mechanical systems. Damage mitigation for Control of mechanical systems is reported in the two-part paper. The concept of damage mitigation is introduced and a continuous-time model of fatigue damage dynamics is formulated in this paper which is the first part. The second part which is a companion paper presents the synthesis of the open-loop Control policy and the results of simulation experiments for transient operations of a reusable rocket engine.

  • damage Mitigating Control of mechanical systems part ii formulation of an optimal policy and simulation
    American Control Conference, 1993
    Co-Authors: Asok Ray, Marc Carpino, Carl F Lorenzo
    Abstract:

    The objective of damage-Mitigating Control introduced in the first part of this two-part paper is to achieve high performance without overstraining the mechanical structures. The major benefit is an increase in the functional life of critical plant components along with enhanced safety, operational reliability, and availability. Specifically, a methodology for modeling fatigue damage has been developed as an augmentation to Control and diagnostics of complex dynamic processes such as advanced aircraft, spacecraft, and power plants. In this paper which is the second part, an optimal Control policy is formulated via nonlinear programming under specified constraints of the damage rate and accumulated damage. The results of simulation experiments for upthrust transient operations of a reusable rocket engine are presented to demonstrate efficacy of the damage-Mitigating Control concept.

John L. Schroeder - One of the best experts on this subject based on the ideXlab platform.

  • Exploring the complexities associated with full-scale wind plant wake mitigation Control experiments
    Wind Energy Science, 2020
    Co-Authors: James B. Duncan, Brian D. Hirth, John L. Schroeder
    Abstract:

    Abstract. Recent research promotes implementing next-generation wind plant Control methods to mitigate turbine-to-turbine wake effects. Numerical simulation and wind tunnel experiments have previously demonstrated the potential benefit of wind plant Control for wind plant optimization, but full-scale validation of the wake-Mitigating Control strategies remains limited. As part of this study, the yaw and blade pitch of a utility-scale wind turbine were strategically modified for a limited time period to examine wind turbine wake response to first-order turbine Control changes. Wind turbine wake response was measured using Texas Tech University's Ka-band Doppler radars and dual-Doppler scanning strategies. Results highlight some of the complexities associated with executing and analyzing wind plant Control at full scale using brief experimental Control periods. Some difficulties include (1) the ability to accurately implement the desired Control changes, (2) identifying reliable data sources and methods to allow these Control changes to be accurately quantified, and (3) attributing variations in wake structure to turbine Control changes rather than a response to the underlying atmospheric conditions (e.g., boundary layer streak orientation, atmospheric stability). To better understand wake sensitivity to the underlying atmospheric conditions, wake evolution within the early-evening transition was also examined using a single-Doppler data collection approach. Analysis of both wake length and meandering during this period of transitioning atmospheric stability indicates the potential benefit and feasibility of wind plant Control should be enhanced when the atmosphere is stable.

  • Exploring the complexities associated with full-scale wind plant wake mitigation Control experiments
    2019
    Co-Authors: James B. Duncan Jr., Brian D. Hirth, John L. Schroeder
    Abstract:

    Abstract. Recent research promotes implementing next-generation wind plant Control methods to mitigate turbine-to-turbine wake effects. Numerical simulation and wind tunnel experiments have previously demonstrated the potential benefit of wind plant Control for wind plant optimization, but full-scale validation of the wake-Mitigating Control strategies remains limited. As part of this study, the yaw and blade pitch of a utility-scale wind turbine were strategically modified for a limited time period to examine wind turbine wake response to first-order turbine Control changes. Wind turbine wake response was measured using Texas Tech University's Ka-band Doppler radars and dual-Doppler scanning strategies. Results highlight some of the complexities associated with executing and analysing wind plant Control at full-scale using brief experimental Control periods. Some difficulties include (1) the ability to accurately implement the desired Control changes, (2) identifying reliable data sources and methods to allow these Control changes to be accurately quantified, and (3) attributing variations in wake structure to turbine Control changes rather than a response to the underlying atmospheric conditions (e.g. boundary layer streak orientation, atmospheric stability). To better understand wake sensitivity to the underlying atmospheric conditions, wake evolution within the early-evening transition was also examined using a single-Doppler data collection approach. Analysis of both wake length and meandering during this period of transitioning atmospheric stability indicate the potential benefit and feasibility of wind plant Control should be enhanced when the atmosphere is stable.

Carl F Lorenzo - One of the best experts on this subject based on the ideXlab platform.

  • Damage-Mitigating Control of Mechanical Systems: Part II—Formulation of an Optimal Policy and Simulation
    Journal of Dynamic Systems Measurement and Control, 1994
    Co-Authors: Asok Ray, Marc Carpino, Carl F Lorenzo
    Abstract:

    The objective of damage-Mitigating Control introduced in the first part of this two-part paper is to achieve high performance without overstraining the mechanical structures. The major benefits its an increase in the functional life of critical plant components along with enhanced safety, operational reliability, and availability. Specifically, a methodology for modeling fatigue damage has been developed as an augmentation to Control and diagnostics of complex dynamic processes such as advanced aircraft, spacecraft, and power plants

  • Damage-Mitigating Control of Mechanical Systems: Part I—Conceptual Development and Model Formulation
    Journal of Dynamic Systems Measurement and Control, 1994
    Co-Authors: Asok Ray, Marc Carpino, Carl F Lorenzo
    Abstract:

    A major goal in the Control of complex mechanical systems such as advanced aircraft, spacecraft, and power plants is to achieve high performance with increased reliability, availability, component durability, and maintainability. The current state-of-the-art of Control systems synthesis focuses on improving performance and diagnostic capabilities under constraints that often do not adequately represent the dynamic properties of the materials. The reason is that the traditional design is based upon the assumption of conventional materials with invariant characteristics. In view of high performance requirements and availability of improved materials, the lack of appropriate knowledge about the properties of these materials will lead to either less than achievable performance due to overly conservative design, or over-straining of the structure leading to unexpected failures and drastic reduction of the service life. The key idea of the research reported in this paper is that a significant improvement in service life can be achieved by a small reduction in the system dynamic performance. This requires augmentation of the current system-theoretic techniques for synthesis of decision and Control laws with governing equations and inequality constraints that would model the properties of the materials for the purpose of damage representation and failure prognosis. The major challenge in this research is to characterize the damage generation process in a continuous-time setting, and then utilize this information for synthesizing algorithms of robust Control, diagnostics, and risk assessment in complex mechanical systems. Damage mitigation for Control of mechanical systems is reported in the two-part paper. The concept of damage mitigation is introduced and a continuous-time model of fatigue damage dynamics is formulated in this paper which is the first part. The second part which is a companion paper presents the synthesis of the open-loop Control policy and the results of simulation experiments for transient operations of a reusable rocket engine.

  • damage Mitigating Control of mechanical systems part i conceptual development and model formulation
    Journal of Dynamic Systems Measurement and Control-transactions of The Asme, 1994
    Co-Authors: Asok Ray, Marc Carpino, Carl F Lorenzo
    Abstract:

    A major goal in the Control of complex mechanical systems such as advanced aircraft, spacecraft, and power plants is to achieve high performance with increased reliability, availability, component durability, and maintainability. The current state-of-the-art of Control systems synthesis focuses on improving performance and diagnostic capabilities under constraints that often do not adequately represent the dynamic properties of the materials. The reason is that the traditional design is based upon the assumption of conventional materials with invariant characteristics. In view of high performance requirements and availability of improved materials, the lack of appropriate knowledge about the properties of these materials will lead to either less than achievable performance due to overly conservative design, or over-straining of the structure leading to unexpected failures and drastic reduction of the service life. The key idea of the research reported in this paper is that a significant improvement in service life can be achieved by a small reduction in the system dynamic performance. This requires augmentation of the current system-theoretic techniques for synthesis of decision and Control laws with governing equations and inequality constraints that would model the properties of the materials for the purpose of damage representation and failure prognosis. The major challenge in this research is to characterize the damage generation process in a continuous-time setting, and then utilize this information for synthesizing algorithms of robust Control, diagnostics, and risk assessment in complex mechanical systems. Damage mitigation for Control of mechanical systems is reported in the two-part paper. The concept of damage mitigation is introduced and a continuous-time model of fatigue damage dynamics is formulated in this paper which is the first part. The second part which is a companion paper presents the synthesis of the open-loop Control policy and the results of simulation experiments for transient operations of a reusable rocket engine.

  • damage Mitigating Control of mechanical systems part ii formulation of an optimal policy and simulation
    American Control Conference, 1993
    Co-Authors: Asok Ray, Marc Carpino, Carl F Lorenzo
    Abstract:

    The objective of damage-Mitigating Control introduced in the first part of this two-part paper is to achieve high performance without overstraining the mechanical structures. The major benefit is an increase in the functional life of critical plant components along with enhanced safety, operational reliability, and availability. Specifically, a methodology for modeling fatigue damage has been developed as an augmentation to Control and diagnostics of complex dynamic processes such as advanced aircraft, spacecraft, and power plants. In this paper which is the second part, an optimal Control policy is formulated via nonlinear programming under specified constraints of the damage rate and accumulated damage. The results of simulation experiments for upthrust transient operations of a reusable rocket engine are presented to demonstrate efficacy of the damage-Mitigating Control concept.

  • Damage-Mitigating Control of Mechanical Systems: Part I -- Conceptual Development and Model Formulation
    1993 American Control Conference, 1993
    Co-Authors: Asok Ray, Marc Carpino, Carl F Lorenzo
    Abstract:

    A major goal in the Control of complex mechanical systems such as advanced aircraft, spacecraft, and power plants is to achieve high performance with increased reliability, availability, component durability, and maintainability. The current state-of-the-art in Control systems synthesis focuses on improving performance and diagnostic capabilities under constraints that often do not adequately represent the dynamic properties of the materials. The reason is that the traditional design is based upon the assumption of conventional materials with invariant characteristics. In view of high performance requirements and availability of improved materials, the lack of appropriate knowledge about the properties of these materials will lead to either less than achievable performance due to overly conservative design, or over-straining of the structure leading to unexpected failures and drastic reduction of the service life. The key idea of the research reported in this paper is that a significant improvement in service life could be achieved by a small reduction in the system dynamic performance. The concept of damage mitigation is introduced and a continuous-time model of fatigue damage dynamics is formulated in this paper which is the first part of a two-part paper. The second part which is a companion paper presents synthesis of an open loop Control policy and the results of simulation experiments for transient operations of a reusable rocket engine.

S. Tangirala - One of the best experts on this subject based on the ideXlab platform.

  • Damage-Mitigating Control of mechanical structures: experimental verification of the concept
    Smart Materials and Structures, 1995
    Co-Authors: S. Tangirala, Asok Ray, Marc Carpino
    Abstract:

    The concept of damage-Mitigating Control is built upon the two disciplines of systems science and the mechanics of materials, and its goal is to achieve an optimized trade-off between the dynamic performance and structural durability of the plant under Control. Simulation studies reported in recent publications show a substantial reduction of damage accumulation in the critical components of a rocket engine with no significant loss of performance. This paper reports an experimental verification of the damage-Mitigating Control concept on a laboratory testbed, which is a two-degree-of-freedom mechanical system excited by a computer-Controlled shaker table. Test results demonstrate: (i) the important feature of optimized damage-Mitigating Control by extending the fatigue life up to 3 1/2 times with no significant performance degradation; and (ii) close agreement between the analytical prediction of damage and the experimental observations.

  • Damage-Mitigating Control of mechanical structures: experimental verification of the concept
    Proceedings of 1995 American Control Conference - ACC'95, 1
    Co-Authors: S. Tangirala, Asok Ray, Marc Carpino
    Abstract:

    The concept of damage-Mitigating Control is built upon the two disciplines of Control systems and mechanics of materials, and its goal is to achieve optimized trade-off between the system performance and structural durability of the plant under Control. Simulation studies have shown a substantial reduction in the damage accumulation in the critical components of a rocket engine with no significant loss of performance. This paper reports experimental verification of the damage-Mitigating Control concept on a laboratory testbed which is a two-degree-of-freedom mechanical system excited by a computer-Controlled shaker table. Test results demonstrate: (i) the important feature of optimized damage-Mitigating Control by extending fatigue life up to three and one half times with no significant performance degradation; and (ii) close agreement between the analytical prediction of damage and experimental observations.