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Ashok Joshi – One of the best experts on this subject based on the ideXlab platform.

  • Active Control of Vibration Modes of a Wing Box by Piezoelectric Stack Actuators
    51st AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference<BR> 18th AIAA ASME AHS Adaptive Structures Conference<BR&, 2010
    Co-Authors: Mandar D. Kulkarni, P M Mujumdar, Gulshan Kumar, Ashok Joshi
    Abstract:

    The paper presents a numerical and experimental study of active control of the coupled bendingtorsion vibration modes of a typical aircraft Wing box structure with a tip store, using piezoelectric ceramic stack actuators. Efforts are driven toward design of a control law and its implementation using a suitable data acquisition hardware and software, to determine the efficacy of stack actuators for such control and understand modeling related issues. The design and fabrication of the scaled Wing box model, reported in an earlier paper, was such that the first three natural frequencies of an Actual Wing box and the corresponding mode shapes were replicated closely in the model. In the finite element analysis of the structure, the piezoelectric stack is modeled as a beam element and a thermal analogy concept has been used to simulate the electro-mechanical coupling in the stack actuator. The closed loop model is formulated in state space using experimentally validated modal model for the system characteristics as well as the modal generalized piezoelectric actuation forces. The closed loop implementation is aimed at achieving maximum damping of the three modes of interest. Accelerometers are used for response sensing. To begin with, feedback is taken from one sensor (accelerometer) and only one stack is used for control action. First, simulations and experiments are done using negative velocity feedback for controlling vibration of the structure under harmonic loading. This method results in significant increase in damping of the structure for excitation of the first three modes individually. In some cases, the amplitude of closed loop vibration decreased to 1/5th the value of open loop vibration. However, both, the simulation and experiments, show a significant control spillover to the other two modes, in each case. To avoid spillover, a new method called ‘three gain SISO velocity feedback system’ is designed, wherein, the response signal (obtained from the accelerometer) is split into three components using band-pass filters. Each of these components represent contribution from one of the three modes. These split signals are multiplied by separate gains and combined to form the final control signal. Thus the control spillover problem is partially solved. However, the system becomes unstable much before the complete control power of the stack can be used thereby suggesting that the control method is sub-optimal. The Linear Quadratic Regulator (LQR) method is also tested. A simple choice of coefficients of the Q and R matrices leads to a satisfactory result for vibration control for an impulse input. Simulation and subsequent experiments confirmed that the LQR method can be used to control impulse disturbance effectively. Further studies explore the idea of “minimization of total (kinetic and strain) energy of the structure to arrive at an appropriate Q matrix. The strategy is to establish a suitable weighting configuration for the various elements of the Q matrix depending upon the sensor-actuator combination being used for closed loop control and to validate it using analytical tools like Bode plots, root locus, simulations with SIMULINK and experimental studies. The closed loop damping so obtained shows a substantial improvement over the other techniques studied.

  • Active Vibration Control of Scaled Wing Box Model Using Piezoelectric Stack Actuators
    49th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference <br> 16th AIAA ASME AHS Adaptive Structures Conference<br, 2008
    Co-Authors: Abhijit Joshi, Arun Shourie, P M Mujumdar, Ashok Joshi
    Abstract:

    The paper presents a numerical and experimental study aimed at investigating the potential of pre-stressed piezoelectric stack actuators for vibration control of a typical aircraft Wing box structure with a tip store. The focus of the study is to assess, through simulation, the control authority of the stack actuators for effectively controlling specific modes of interest and experimentally verify the same. Towards this, a geometrically similar, 1:1.6 scaled model of a typical Wing box structure has been designed from data available for a Actual aircraft Wing box with attached tip store. The model is designed and fabricated such that the first three natural frequencies of the Actual Wing box and the corresponding mode shapes were replicated closely in the model. Finite element analyses of the actuated structure are performed using ANSYS®. The piezoelectric stack is modeled as a beam element and a thermal analogy concept has been used to simulate the electro-mechanical coupling in the stack actuator. A finite element model is created for the fabricated scaled model along with its mounting rig to include the effects of the rig flexibility. Experimental modal testing results show a good match with numerical computations. Sensitivity studies carried out to study the effectiveness of a single stack actuator at different locations on the front and rear spar of the Wing box suggest the different locations where the stack has highest actuation authority over the individual bending and torsion modes. This was verified by the open loop experiments. Comparison between open loop dynamic response simulations and corresponding experimental results establish the validity of the simplified modeling of the stack actuator fairly well within experimental uncertainties. The closed loop model is formulated in state space using experimentally validated modal model for the system characteristics as well as the modal generalized piezoelectric actuation forces. Accelerometers are used for response sensing. The closed loop implementation is aimed at achieving maximum damping of the controlled modes, through a negative velocity feedback control law. The acceleration output is integrated once to obtain the combined velocity signal from all the modes that are sensed. However, the rate gain is designed assuming only first three vibration modes to be significant. Simulations are carried out in SIMULINK® to characterize the effect of control gains on the overall response of the close loop control to a disturbance input, with the constraint on the stack actuator voltage to be within 0-150V. The results show significant improvement in the damping of the first three modes. Closed loop experiments are being implemented.

Hoon Cheol Park – One of the best experts on this subject based on the ideXlab platform.

  • design and evaluation of a deformable Wing configuration for economical hovering flight of an insect like tailless flying robot
    Bioinspiration & Biomimetics, 2018
    Co-Authors: Hoang Vu Phan, Hoon Cheol Park
    Abstract:

    Studies on Wing kinematics indicate that flapping insect Wings operate at higher angles of attack (AoAs) than conventional rotary Wings. Thus, effectively flying an insect-like flapping-Wing micro air vehicle (FW-MAV) requires appropriate Wing design for achieving low powepower consumption and high force generation. Even though theoretical studies can be performed to identify appropriate geometric AoAs for a Wing for achieving efficient hovering flight, designing an Actual Wing by implementing these angles into a real flying robot is challenging. In this work, we investigated the Wing morphology of an insect-like tailless FW-MAV, which was named KUBeetle, for obtaining high vertical force/power ratio or power loading. Several deformable Wing configurations with various vein structures were designed, and their characteristics of vertical force generation and power requirement were theoretically and experimentally investigated. The results of the theoretical study based on the unsteady blade element theory (UBET) were validated with reference data to prove the accuracy of power estimation. A good agreement between estimated and measured results indicated that the proposed UBET model can be used to effectively estimate the power requirement and force generation of an FW-MAV. Among the investigated Wing configurations operating at flapping frequencies of 23 Hz to 29 Hz, estimated results showed that the Wing with a suitable vein placed outboard exhibited an increase of approximately 23.7%  ±  0.5% in vertical force and approximately 10.2%  ±  1.0% in force/power ratio. The estimation was supported by experimental results, which showed that the suggested Wing enhanced vertical force by approximately 21.8%  ±  3.6% and force/power ratio by 6.8%  ±  1.6%. In addition, Wing kinematics during flapping motion was analyzed to determine the reason for the observed improvement.

David Rohlmann – One of the best experts on this subject based on the ideXlab platform.

  • Advanced Design Approach for a High-Lift Wind Tunnel Model Based on Flight Test Data
    Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 2015
    Co-Authors: Niko Bier, Stefan Keye, David Rohlmann
    Abstract:

    The objective of the joint research project HINVA (High-Lift In-Flight Validation) funded by the German Federal Ministry of Economics and Technology within the fourth Aeronautical Research Program LuFo IV is to significantly enhance the accuracy and reliability of both numerical and experimental simulation methods with respect to the aerodynamic performance prediction of civil transport aircraft with deployed high-lift devices. To achieve this goal, the most advanced computational fluifluid dynamics (CFD) and wind tunnel simulation methods currently in industrial use are to be validated against flight test data. DLR’s Airbus A320-200 Advanced Technology Research Aircraft (ATRA) serves as a common configurative basis for the three fields of methodology 1) flight test, 2) high Reynolds-number testing in the European Transonic Wind Tunnel (ETW), and 3) numerical simulation using DLR’s TAU code. To meet the demanding accuracy specified in HINVA, the wind tunnel model Wing must be geometrically similar to the ATRA Wing in flight, i.e. have the same spanwise twist distribution, when subjected to the aerodynamic loads existing at maximum lift flow conditions in ETW. The inverse design approach of defining the corresponding model jig shape is based on a combined use of measured flow conditions and Wing deformations from a selected reference test flight and fluid-structure coupled simulations using a model scale CFD grid, wind tunnel flow conditions equivalent to the reference flight state, and a wind tunnel structural model. When exposed to the aerodynamic loads under ETW flow conditions, the designed model jig shape leads to a final Wing shape which closely resembles ATRA’s Actual Wing shape at maximum lift.

  • Design of a Wind Tunnel Model for Maximum Lift Predictions Based on Flight Test Data
    31st AIAA Applied Aerodynamics Conference, 2013
    Co-Authors: Niko Bier, Stefan Keye, David Rohlmann
    Abstract:

    The objective of the joint research project HINVA (High-Lift In-Flight Validation) funded by the German Federal Ministry of Economics and Technology within the fourth Aeronautical Research Program LuFo IV is to significantly enhance the accuracy and reliability of both numerical and experimental simulation methods with respect to the aerodynamic performance prediction of civil transport aircraft with deployed high-lift devices. To achieve this goal, the most advanced computational fluifluid dynamics (CFD) and wind tunnel simulation methods currently in industrial use are to be validated against flight test data. DLR’s Airbus A320-200 Advanced Technology Research Aircraft (ATRA) serves as a common configurative basis for the three fields of methodology 1) flight test, 2) high Reynolds-number testing in the European Transonic Wind Tunnel (ETW), and 3) numerical simulation using DLR’s TAU code. A core project task is to generate a dedicated, fully harmonized validation database consisting of experimental data from both wind tunnel and flight test. To meet the demanding accuracy specified in HINVA, the wind tunnel model Wing must be geometrically similar to the ATRA Wing in flight, i.e. have the same spanwise twist distribution, when subjected to the aerodynamic loads existing at maximum lift flow conditions in ETW. The inverse design approach of defining the corresponding Wing predeformation, or model jig shape, is based on a combined use of measured flow conditions and Wing deformations from a selected reference test flight and fluid-structure coupled simulations using a model scale CFD grid, wind tunnel flow conditions equivalent to the reference flight state, and a wind tunnel structural model. When exposed to the aerodynamic loads under ETW flow conditions, the designed model jig shape should lead to a final Wing shape which closely resembles ATRA’s Actual Wing shape at maximum lift.

Hoang Vu Phan – One of the best experts on this subject based on the ideXlab platform.

  • design and evaluation of a deformable Wing configuration for economical hovering flight of an insect like tailless flying robot
    Bioinspiration & Biomimetics, 2018
    Co-Authors: Hoang Vu Phan, Hoon Cheol Park
    Abstract:

    Studies on Wing kinematics indicate that flapping insect Wings operate at higher angles of attack (AoAs) than conventional rotary Wings. Thus, effectively flying an insect-like flapping-Wing micro air vehicle (FW-MAV) requires appropriate Wing design for achieving low power consumption and high force generation. Even though theoretical studies can be performed to identify appropriate geometric AoAs for a Wing for achieving efficient hovering flight, designing an Actual Wing by implementing these angles into a real flying robot is challenging. In this work, we investigated the Wing morphology of an insect-like tailless FW-MAV, which was named KUBeetle, for obtaining high vertical force/power ratio or power loading. Several deformable Wing configurations with various vein structures were designed, and their characteristics of vertical force generation and power requirement were theoretically and experimentally investigated. The results of the theoretical study based on the unsteady blade element theory (UBET) were validated with reference data to prove the accuracy of power estimation. A good agreement between estimated and measured results indicated that the proposed UBET model can be used to effectively estimate the power requirement and force generation of an FW-MAV. Among the investigated Wing configurations operating at flapping frequencies of 23 Hz to 29 Hz, estimated results showed that the Wing with a suitable vein placed outboard exhibited an increase of approximately 23.7%  ±  0.5% in vertical force and approximately 10.2%  ±  1.0% in force/power ratio. The estimation was supported by experimental results, which showed that the suggested Wing enhanced vertical force by approximately 21.8%  ±  3.6% and force/power ratio by 6.8%  ±  1.6%. In addition, Wing kinematics during flapping motion was analyzed to determine the reason for the observed improvement.

Niko Bier – One of the best experts on this subject based on the ideXlab platform.

  • Advanced Design Approach for a High-Lift Wind Tunnel Model Based on Flight Test Data
    Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 2015
    Co-Authors: Niko Bier, Stefan Keye, David Rohlmann
    Abstract:

    The objective of the joint research project HINVA (High-Lift In-Flight Validation) funded by the German Federal Ministry of Economics and Technology within the fourth Aeronautical Research Program LuFo IV is to significantly enhance the accuracy and reliability of both numerical and experimental simulation methods with respect to the aerodynamic performance prediction of civil transport aircraft with deployed high-lift devices. To achieve this goal, the most advanced computational fluid dynamics (CFD) and wind tunnel simulation methods currently in industrial use are to be validated against flight test data. DLR’s Airbus A320-200 Advanced Technology Research Aircraft (ATRA) serves as a common configurative basis for the three fields of methodology 1) flight test, 2) high Reynolds-number testing in the European Transonic Wind Tunnel (ETW), and 3) numerical simulation using DLR’s TAU code. To meet the demanding accuracy specified in HINVA, the wind tunnel model Wing must be geometrically similar to the ATRA Wing in flight, i.e. have the same spanwise twist distribution, when subjected to the aerodynamic loads existing at maximum lift flow conditions in ETW. The inverse design approach of defining the corresponding model jig shape is based on a combined use of measured flow conditions and Wing deformations from a selected reference test flight and fluid-structure coupled simulations using a model scale CFD grid, wind tunnel flow conditions equivalent to the reference flight state, and a wind tunnel structural model. When exposed to the aerodynamic loads under ETW flow conditions, the designed model jig shape leads to a final Wing shape which closely resembles ATRA’s Actual Wing shape at maximum lift.

  • Design of a Wind Tunnel Model for Maximum Lift Predictions Based on Flight Test Data
    31st AIAA Applied Aerodynamics Conference, 2013
    Co-Authors: Niko Bier, Stefan Keye, David Rohlmann
    Abstract:

    The objective of the joint research project HINVA (High-Lift In-Flight Validation) funded by the German Federal Ministry of Economics and Technology within the fourth Aeronautical Research Program LuFo IV is to significantly enhance the accuracy and reliability of both numerical and experimental simulation methods with respect to the aerodynamic performance prediction of civil transport aircraft with deployed high-lift devices. To achieve this goal, the most advanced computational fluid dynamics (CFD) and wind tunnel simulation methods currently in industrial use are to be validated against flight test data. DLR’s Airbus A320-200 Advanced Technology Research Aircraft (ATRA) serves as a common configurative basis for the three fields of methodology 1) flight test, 2) high Reynolds-number testing in the European Transonic Wind Tunnel (ETW), and 3) numerical simulation using DLR’s TAU code. A core project task is to generate a dedicated, fully harmonized validation database consisting of experimental data from both wind tunnel and flight test. To meet the demanding accuracy specified in HINVA, the wind tunnel model Wing must be geometrically similar to the ATRA Wing in flight, i.e. have the same spanwise twist distribution, when subjected to the aerodynamic loads existing at maximum lift flow conditions in ETW. The inverse design approach of defining the corresponding Wing predeformation, or model jig shape, is based on a combined use of measured flow conditions and Wing deformations from a selected reference test flight and fluid-structure coupled simulations using a model scale CFD grid, wind tunnel flow conditions equivalent to the reference flight state, and a wind tunnel structural model. When exposed to the aerodynamic loads under ETW flow conditions, the designed model jig shape should lead to a final Wing shape which closely resembles ATRA’s Actual Wing shape at maximum lift.