The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform

Ronald W Yeung - One of the best experts on this subject based on the ideXlab platform.

  • Power-to-load balancing for asymmetric heave wave energy converters with nonideal power take-off
    Renewable Energy, 2017
    Co-Authors: Nathan Tom, Farshad Madhi, Ronald W Yeung
    Abstract:

    Abstract The aim of this paper is to maximize the power-to-load ratio for asymmetric wave energy converters undergoing heave motion. Linear hydrodynamic theory is used to calculate bounds of the expected time-averaged power (TAP) and corresponding surge-Restraining Force, pitch-Restraining torque, and power take-off (PTO) control Force with the assumption of sinusoidal displacement. This paper formulates an optimal control problem to handle an objective function with competing terms in an attempt to maximize power capture while minimizing structural and actuator loads in regular and irregular waves. Penalty weights are placed on the surge-Restraining Force, pitch-Restraining torque, and PTO actuation Force, thereby allowing the control focus to concentrate on either power absorption or load mitigation. The penalty weights are used to control peak structural and actuator loads that were found to curb the additional losses in power absorption associated with a nonideal PTO. Thus, in achieving these goals, a per-unit gain in TAP would not lead to a greater per-unit demand in structural strength, hence yielding a favorable benefit-to-cost ratio. Demonstrative results for “The Berkeley Wedge” in the form of output TAP, reactive TAP needed to drive WEC motion, and the amplitudes of the surge-Restraining Force, pitch-Restraining torque, and PTO control Force are shown.

  • balancing power absorption and structural loading for an asymmetric heave wave energy converter in regular waves
    ASME 2016 35th International Conference on Ocean Offshore and Arctic Engineering, 2016
    Co-Authors: Farshad Madhi, Ronald W Yeung
    Abstract:

    The aim of this paper is to maximize the power-to-load ratio of the Berkeley Wedge: a one-degree-of-freedom, asymmetrical, energy-capturing, floating breakwater of high performance that is relatively free of viscosity effects. Linear hydrodynamic theory was used to calculate bounds on the expected time-averaged power (TAP) and corresponding surge Restraining Force, pitch Restraining torque, and power take-off (PTO) control Force when assuming that the heave motion of the wave energy converter remains sinusoidal. This particular device was documented to be an almost-perfect absorber if one-degree-of-freedom motion is maintained. The success of such or similar future wave energy converter technologies would require the development of control strategies that can adapt device performance to maximize energy generation in operational conditions while mitigating hydrodynamic loads in extreme waves to reduce the structural mass and overall cost. This paper formulates the optimal control problem to incorporate metrics that provide a measure of the surge Restraining Force, pitch Restraining torque, and PTO control Force. The optimizer must now handle an objective function with competing terms in an attempt to maximize power capture while minimizing structural and actuator loads. A penalty weight is placed on the surge Restraining Force, pitch Restraining torque, and PTO actuation Force, therebymore » allowing the control focus to be placed either on power absorption or load mitigation. Thus, in achieving these goals, a per-unit gain in TAP would not lead to a greater per-unit demand in structural strength, hence yielding a favorable benefit-to-cost ratio. Demonstrative results in the form of TAP, reactive TAP, and the amplitudes of the surge Restraining Force, pitch Restraining torque, and PTO control Force are shown for the Berkeley Wedge example.« less

Farshad Madhi - One of the best experts on this subject based on the ideXlab platform.

  • Power-to-load balancing for asymmetric heave wave energy converters with nonideal power take-off
    Renewable Energy, 2017
    Co-Authors: Nathan Tom, Farshad Madhi, Ronald W Yeung
    Abstract:

    Abstract The aim of this paper is to maximize the power-to-load ratio for asymmetric wave energy converters undergoing heave motion. Linear hydrodynamic theory is used to calculate bounds of the expected time-averaged power (TAP) and corresponding surge-Restraining Force, pitch-Restraining torque, and power take-off (PTO) control Force with the assumption of sinusoidal displacement. This paper formulates an optimal control problem to handle an objective function with competing terms in an attempt to maximize power capture while minimizing structural and actuator loads in regular and irregular waves. Penalty weights are placed on the surge-Restraining Force, pitch-Restraining torque, and PTO actuation Force, thereby allowing the control focus to concentrate on either power absorption or load mitigation. The penalty weights are used to control peak structural and actuator loads that were found to curb the additional losses in power absorption associated with a nonideal PTO. Thus, in achieving these goals, a per-unit gain in TAP would not lead to a greater per-unit demand in structural strength, hence yielding a favorable benefit-to-cost ratio. Demonstrative results for “The Berkeley Wedge” in the form of output TAP, reactive TAP needed to drive WEC motion, and the amplitudes of the surge-Restraining Force, pitch-Restraining torque, and PTO control Force are shown.

  • balancing power absorption and structural loading for an asymmetric heave wave energy converter in regular waves
    ASME 2016 35th International Conference on Ocean Offshore and Arctic Engineering, 2016
    Co-Authors: Farshad Madhi, Ronald W Yeung
    Abstract:

    The aim of this paper is to maximize the power-to-load ratio of the Berkeley Wedge: a one-degree-of-freedom, asymmetrical, energy-capturing, floating breakwater of high performance that is relatively free of viscosity effects. Linear hydrodynamic theory was used to calculate bounds on the expected time-averaged power (TAP) and corresponding surge Restraining Force, pitch Restraining torque, and power take-off (PTO) control Force when assuming that the heave motion of the wave energy converter remains sinusoidal. This particular device was documented to be an almost-perfect absorber if one-degree-of-freedom motion is maintained. The success of such or similar future wave energy converter technologies would require the development of control strategies that can adapt device performance to maximize energy generation in operational conditions while mitigating hydrodynamic loads in extreme waves to reduce the structural mass and overall cost. This paper formulates the optimal control problem to incorporate metrics that provide a measure of the surge Restraining Force, pitch Restraining torque, and PTO control Force. The optimizer must now handle an objective function with competing terms in an attempt to maximize power capture while minimizing structural and actuator loads. A penalty weight is placed on the surge Restraining Force, pitch Restraining torque, and PTO actuation Force, therebymore » allowing the control focus to be placed either on power absorption or load mitigation. Thus, in achieving these goals, a per-unit gain in TAP would not lead to a greater per-unit demand in structural strength, hence yielding a favorable benefit-to-cost ratio. Demonstrative results in the form of TAP, reactive TAP, and the amplitudes of the surge Restraining Force, pitch Restraining torque, and PTO control Force are shown for the Berkeley Wedge example.« less

J X Zhang - One of the best experts on this subject based on the ideXlab platform.

  • investigation of external Restraining Force effects on welding residual stresses using three dimensional thermal elastic plastic multi body coupling finite element model
    Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2009
    Co-Authors: C Liu, J X Zhang
    Abstract:

    AbstractA three-dimensional multi-body coupling thermal elastic—plastic finite element (FE) model — in which clamp, clamping strip, worktable, and welding plate are included — is developed to simulate the external Restraining Force effects on welding residual stresses. Welding experiments are also carried out to measure the Restraining Forces and transient distortions to validate the model. Simulated results from the multi-body model and the displacement constraints model are compared, the effect of restraints release on welding residual stresses is also analysed. The analysis results show that the simulated transverse residual stresses with the displacement constraints model are larger than those of the multi-body coupling model; the transverse welding residual stress at the welding centre-line clearly varies with increasing Restraining Force: it decreases on the top surface and increases on the bottom surface after restraints release as the Restraining Force is small, and will not be released after rest...

  • Investigation of external Restraining Force effects on welding residual stresses using three-dimensional thermal elastic—plastic multi-body coupling finite element model
    Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2009
    Co-Authors: C Liu, J X Zhang
    Abstract:

    AbstractA three-dimensional multi-body coupling thermal elastic—plastic finite element (FE) model — in which clamp, clamping strip, worktable, and welding plate are included — is developed to simulate the external Restraining Force effects on welding residual stresses. Welding experiments are also carried out to measure the Restraining Forces and transient distortions to validate the model. Simulated results from the multi-body model and the displacement constraints model are compared, the effect of restraints release on welding residual stresses is also analysed. The analysis results show that the simulated transverse residual stresses with the displacement constraints model are larger than those of the multi-body coupling model; the transverse welding residual stress at the welding centre-line clearly varies with increasing Restraining Force: it decreases on the top surface and increases on the bottom surface after restraints release as the Restraining Force is small, and will not be released after rest...

C Liu - One of the best experts on this subject based on the ideXlab platform.

  • investigation of external Restraining Force effects on welding residual stresses using three dimensional thermal elastic plastic multi body coupling finite element model
    Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2009
    Co-Authors: C Liu, J X Zhang
    Abstract:

    AbstractA three-dimensional multi-body coupling thermal elastic—plastic finite element (FE) model — in which clamp, clamping strip, worktable, and welding plate are included — is developed to simulate the external Restraining Force effects on welding residual stresses. Welding experiments are also carried out to measure the Restraining Forces and transient distortions to validate the model. Simulated results from the multi-body model and the displacement constraints model are compared, the effect of restraints release on welding residual stresses is also analysed. The analysis results show that the simulated transverse residual stresses with the displacement constraints model are larger than those of the multi-body coupling model; the transverse welding residual stress at the welding centre-line clearly varies with increasing Restraining Force: it decreases on the top surface and increases on the bottom surface after restraints release as the Restraining Force is small, and will not be released after rest...

  • Investigation of external Restraining Force effects on welding residual stresses using three-dimensional thermal elastic—plastic multi-body coupling finite element model
    Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2009
    Co-Authors: C Liu, J X Zhang
    Abstract:

    AbstractA three-dimensional multi-body coupling thermal elastic—plastic finite element (FE) model — in which clamp, clamping strip, worktable, and welding plate are included — is developed to simulate the external Restraining Force effects on welding residual stresses. Welding experiments are also carried out to measure the Restraining Forces and transient distortions to validate the model. Simulated results from the multi-body model and the displacement constraints model are compared, the effect of restraints release on welding residual stresses is also analysed. The analysis results show that the simulated transverse residual stresses with the displacement constraints model are larger than those of the multi-body coupling model; the transverse welding residual stress at the welding centre-line clearly varies with increasing Restraining Force: it decreases on the top surface and increases on the bottom surface after restraints release as the Restraining Force is small, and will not be released after rest...

Sung Ho Park - One of the best experts on this subject based on the ideXlab platform.

  • simulation based prediction model of the draw bead Restraining Force and its application to sheet metal forming process
    Journal of Materials Processing Technology, 2007
    Co-Authors: Jung Han Song, Sung Ho Park
    Abstract:

    Abstract Draw-bead is applied to control the material flow in a stamping process and improve the product quality by controlling the draw-bead Restraining Force (DBRF). Actual die design depends mostly on the trial-and-error method without calculating the optimum DBRF. Die design with the predicted value of DBRF can be utilized at the tryout stage effectively reducing the cost of the product development. For the prediction of DBRF, a simulation-based prediction model of the circular draw-bead is developed using the Box-Behnken design with selected shape parameters such as the bead height, the shoulder radius and the sheet thickness. The value of DBRF obtained from each design case by analysis is approximated by a second order regression equation. This equation can be utilized to the calculation of the Restraining Force and the determination of the draw-bead shape as a prediction model. For the evaluation of the prediction model, the optimum design of DBRF in sheet metal forming is carried out using response surface methodology. The suitable type of the draw-bead is suggested based on the optimum values of DBRF. The prediction model of the circular draw-bead proposes the design method of the draw-bead shape. The present procedure provides a guideline in the tool design stage for sheet metal forming to reduce the cost of the product development.