Gian Luca Ghiringhelli | Politecnico di Milano (original) (raw)
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Papers by Gian Luca Ghiringhelli
Journal of Sound and Vibration
Meccanica, 1990
Sommario Si prende in considerazione il problema connesso con l'esistenza di sing... more Sommario Si prende in considerazione il problema connesso con l'esistenza di singolarità nel campo di sforzo presente ai bordi liberi di laminati piani in materialxe composito, in presenza di uno strato di resina interlaminare.
This paper deals with the simulation of landing gear semi-active control for a small trainer airc... more This paper deals with the simulation of landing gear semi-active control for a small trainer aircraft in a multibody framework. The behavior of single passive landing gear drop test simulation models and of a complete aircraft landing simulation model, developed and implemented in the commercial multibody code ADAMS in previous works, is compared to the that of analogous models equipped with semiactive shock absorber controllers. The control strategy and the controller tuning and sensitivity tests are briefly outlined and the results of its application to the landing gears is presented. The reduction in peak vertical attachment load values for the landing gear drop tests ranges from 5% to 35%, depending on the test conditions, and in the complete aircraft landing simulation, it is in the order of 5% to 20%, once again depending on the particular landing configuration. Comparisons between the drop tests and complete landing simulations in corresponding conditions are made, and the significant sensitivity tests are repeated on the complete aircraft model.
The structure of the control matrix of a direct strain rate feedback, based on collocated piezoel... more The structure of the control matrix of a direct strain rate feedback, based on collocated piezoelectric patches operated in surface mode, is analytically obtained in the elementary case of a simply supported beam. This kind of control, often improperly called "velocity feedback" because of a formal analogy with the equation of a classical velocity controlled system, has been exploited by several authors with contradictory results. The study of the measurement and actuation matrices, together with the parametric eigenvalue analysis of the control matrix, allowed the identification of an instability mechanism that could justify experimental evidences. The most critical parameter seems to be the error in collocation, that can reduce the stability as much as wider is the frequency range of interest.
The paper describes the aeroelastic analysis of a tiltrotor con guration. The 1/5 scale wind tunn... more The paper describes the aeroelastic analysis of a tiltrotor con guration. The 1/5 scale wind tunnel semispan model of the V-22 tiltrotor aircraft is considered. The analysis is performed by means of a multi-body code, based on an original formulation. The di erential equilibrium problem is stated in terms of rst order di erential equations. The equilibrium equations of every rigid body are written, together with the de nitions of the momenta. The bodies are connected by kinematic constraints, applied in form of Lagrangian multipliers. Deformable components are mainly modelled by means of beam elements, based on an original nite volume formulation. Multidisciplinar problems can be solved by adding user-de ned di erential equations. In the presented analysis the equations related to the control of the swash-plate of the model are considered. Advantages of a multi-body aeroelastic code over existing comprehensive rotorcraft codes include the exact modelling of the kinematics of the hub, the detailed modelling of the exibility of critical hub components, and the possibility to simulate steady ight conditions as well as wind-up and maneuvers. The simulations described in the paper include: 1) the analysis of the aeroelastic stability, with particular regard to the proprotor/pylon instability that is peculiar to tiltrotors, 2) the determination of the dynamic behavior of the system and of the loads due to typical maneuvers, with particular regard to the conversion from helicopter to airplane mode, and 3) the stress evaluation in critical components, such as the pitch links and the conversion downstop spring.
The aim of this paper is to present a consistent theory for the deformation of a naturally curved... more The aim of this paper is to present a consistent theory for the deformation of a naturally curved and twisted anisotropic beam. The proposed formulation naturally extends the classical Saint-Venant approach to the case of curved, twisted anisotropic beams. The mathematical model developed under the assumption of span-wise uniform cross-section, curvature and twist, can take into account any kind of elastic coupling due to the material properties and the curved geometry. The consistency of the math-model presented and its generality about the crosssectional shape make it a useful tool in a preliminary design optimization context such as, for example, the aeroelastic tailoring of helicopter rotor blades. Obviously one of the main problems remains the identification of the elastic properties needed when modeling composite beams. Some simple examples are given in order to determine the feasibility of the method.
The paper presents a procedure and the integrated tools for the aeroelastic analysis of an active... more The paper presents a procedure and the integrated tools for the aeroelastic analysis of an active twist helicopter rotor (ATR). The active twisting of rotor blades is carried out by induced-strain actuators distributed into the structure of the blade. Active fiber composites (AFC), made of piezoelectric fibers actuated by interdigitated electrodes (IDE), are used to obtain anisotropic induced-strain actuation capable of twisting the blade. The elastic, inertial and piezoelectric properties of the blade section are determined by a dedicated semianalytical formulation that accounts for the non-homogeneity and the anisotropy of the elastic and piezoelectric materials. A three-dimensional Finite Element Analysis of the piezoelectric fiber with interdigitated electrodes is used to estimate the equivalent homogeneous material properties required for the blade section characterization. A four-blade, articulated rotor is analyzed in hover and forward flight conditions. The system is modeled by an original multibody formulation, implemented in a code named MBDyn (Multi-Body Dynamics). The equilibrium equations and the momenta are written for each body, together with the constraint equations, as a redundant coordinate set formulation. The blades are modeled as beam elements, by an original finite volume formulation for the analysis of nonlinear, initially curved and twisted beams subject to large displacements and rotations. The formulation is extended to include the effects of embedded piezoelectric devices as actuators. Electric and control-related degrees of freedom and elements have been added to MBDyn. Preliminary results related to the actuation authority of the active blade are presented
The experiences on multibody multidisciplinary analysis of rotorcraft made over the years by a re... more The experiences on multibody multidisciplinary analysis of rotorcraft made over the years by a research group at the Department of Aerospace Engineering of the University Politecnico di Milano" are presented. The original formulation that has been developed and implemented is briey presented; dierent applications are discussed, emphasizing the multidisciplinary aspects of the work.
1 An adaptive vibration control system based on Diagonal Recurrent Neural Networks has been devel... more 1 An adaptive vibration control system based on Diagonal Recurrent Neural Networks has been developed and experimentally verified on a rectangular flat aluminum panel with piezoelectric sensors and actuators applied on both surfaces. The objective was to reduce the structural vibrations induced by an electromechanical harmonic disturbance excitation in correspondence of the resonance frequencies of the panel. An electrostructural model has been implemented by means of an integrated Finite Element approach, to design and test the regulation systems. The Neural Network control system has been compared to a sub-optimal regulator in terms of performance and computational requirements during the real test session. To support the real-time control system in the experimental activity, a dedicated variant of RT-Linux operative system, has been developed, that allows a maximum control frequency up to 20 kHz depending on the complexity of the control law. INTRODUCTION In recent years there ha...
Journal of Sound and Vibration
Meccanica, 1990
Sommario Si prende in considerazione il problema connesso con l'esistenza di sing... more Sommario Si prende in considerazione il problema connesso con l'esistenza di singolarità nel campo di sforzo presente ai bordi liberi di laminati piani in materialxe composito, in presenza di uno strato di resina interlaminare.
This paper deals with the simulation of landing gear semi-active control for a small trainer airc... more This paper deals with the simulation of landing gear semi-active control for a small trainer aircraft in a multibody framework. The behavior of single passive landing gear drop test simulation models and of a complete aircraft landing simulation model, developed and implemented in the commercial multibody code ADAMS in previous works, is compared to the that of analogous models equipped with semiactive shock absorber controllers. The control strategy and the controller tuning and sensitivity tests are briefly outlined and the results of its application to the landing gears is presented. The reduction in peak vertical attachment load values for the landing gear drop tests ranges from 5% to 35%, depending on the test conditions, and in the complete aircraft landing simulation, it is in the order of 5% to 20%, once again depending on the particular landing configuration. Comparisons between the drop tests and complete landing simulations in corresponding conditions are made, and the significant sensitivity tests are repeated on the complete aircraft model.
The structure of the control matrix of a direct strain rate feedback, based on collocated piezoel... more The structure of the control matrix of a direct strain rate feedback, based on collocated piezoelectric patches operated in surface mode, is analytically obtained in the elementary case of a simply supported beam. This kind of control, often improperly called "velocity feedback" because of a formal analogy with the equation of a classical velocity controlled system, has been exploited by several authors with contradictory results. The study of the measurement and actuation matrices, together with the parametric eigenvalue analysis of the control matrix, allowed the identification of an instability mechanism that could justify experimental evidences. The most critical parameter seems to be the error in collocation, that can reduce the stability as much as wider is the frequency range of interest.
The paper describes the aeroelastic analysis of a tiltrotor con guration. The 1/5 scale wind tunn... more The paper describes the aeroelastic analysis of a tiltrotor con guration. The 1/5 scale wind tunnel semispan model of the V-22 tiltrotor aircraft is considered. The analysis is performed by means of a multi-body code, based on an original formulation. The di erential equilibrium problem is stated in terms of rst order di erential equations. The equilibrium equations of every rigid body are written, together with the de nitions of the momenta. The bodies are connected by kinematic constraints, applied in form of Lagrangian multipliers. Deformable components are mainly modelled by means of beam elements, based on an original nite volume formulation. Multidisciplinar problems can be solved by adding user-de ned di erential equations. In the presented analysis the equations related to the control of the swash-plate of the model are considered. Advantages of a multi-body aeroelastic code over existing comprehensive rotorcraft codes include the exact modelling of the kinematics of the hub, the detailed modelling of the exibility of critical hub components, and the possibility to simulate steady ight conditions as well as wind-up and maneuvers. The simulations described in the paper include: 1) the analysis of the aeroelastic stability, with particular regard to the proprotor/pylon instability that is peculiar to tiltrotors, 2) the determination of the dynamic behavior of the system and of the loads due to typical maneuvers, with particular regard to the conversion from helicopter to airplane mode, and 3) the stress evaluation in critical components, such as the pitch links and the conversion downstop spring.
The aim of this paper is to present a consistent theory for the deformation of a naturally curved... more The aim of this paper is to present a consistent theory for the deformation of a naturally curved and twisted anisotropic beam. The proposed formulation naturally extends the classical Saint-Venant approach to the case of curved, twisted anisotropic beams. The mathematical model developed under the assumption of span-wise uniform cross-section, curvature and twist, can take into account any kind of elastic coupling due to the material properties and the curved geometry. The consistency of the math-model presented and its generality about the crosssectional shape make it a useful tool in a preliminary design optimization context such as, for example, the aeroelastic tailoring of helicopter rotor blades. Obviously one of the main problems remains the identification of the elastic properties needed when modeling composite beams. Some simple examples are given in order to determine the feasibility of the method.
The paper presents a procedure and the integrated tools for the aeroelastic analysis of an active... more The paper presents a procedure and the integrated tools for the aeroelastic analysis of an active twist helicopter rotor (ATR). The active twisting of rotor blades is carried out by induced-strain actuators distributed into the structure of the blade. Active fiber composites (AFC), made of piezoelectric fibers actuated by interdigitated electrodes (IDE), are used to obtain anisotropic induced-strain actuation capable of twisting the blade. The elastic, inertial and piezoelectric properties of the blade section are determined by a dedicated semianalytical formulation that accounts for the non-homogeneity and the anisotropy of the elastic and piezoelectric materials. A three-dimensional Finite Element Analysis of the piezoelectric fiber with interdigitated electrodes is used to estimate the equivalent homogeneous material properties required for the blade section characterization. A four-blade, articulated rotor is analyzed in hover and forward flight conditions. The system is modeled by an original multibody formulation, implemented in a code named MBDyn (Multi-Body Dynamics). The equilibrium equations and the momenta are written for each body, together with the constraint equations, as a redundant coordinate set formulation. The blades are modeled as beam elements, by an original finite volume formulation for the analysis of nonlinear, initially curved and twisted beams subject to large displacements and rotations. The formulation is extended to include the effects of embedded piezoelectric devices as actuators. Electric and control-related degrees of freedom and elements have been added to MBDyn. Preliminary results related to the actuation authority of the active blade are presented
The experiences on multibody multidisciplinary analysis of rotorcraft made over the years by a re... more The experiences on multibody multidisciplinary analysis of rotorcraft made over the years by a research group at the Department of Aerospace Engineering of the University Politecnico di Milano" are presented. The original formulation that has been developed and implemented is briey presented; dierent applications are discussed, emphasizing the multidisciplinary aspects of the work.
1 An adaptive vibration control system based on Diagonal Recurrent Neural Networks has been devel... more 1 An adaptive vibration control system based on Diagonal Recurrent Neural Networks has been developed and experimentally verified on a rectangular flat aluminum panel with piezoelectric sensors and actuators applied on both surfaces. The objective was to reduce the structural vibrations induced by an electromechanical harmonic disturbance excitation in correspondence of the resonance frequencies of the panel. An electrostructural model has been implemented by means of an integrated Finite Element approach, to design and test the regulation systems. The Neural Network control system has been compared to a sub-optimal regulator in terms of performance and computational requirements during the real test session. To support the real-time control system in the experimental activity, a dedicated variant of RT-Linux operative system, has been developed, that allows a maximum control frequency up to 20 kHz depending on the complexity of the control law. INTRODUCTION In recent years there ha...