Umberto Saetti

University of Maryland

This study presents the integration of a flight simulation code (PSUHeloSim), a high fidelity rotor aeromechanics model with free wake (CHARM Rotor Module), and an industry standard noise prediction tool (PSU-WOPWOP) into a comprehensive noise prediction system. The flight simulation uses a Dynamic Inversion autonomous controller to follow a prescr...

This study presents the integration of the Fast Multipole Method (FMM) into a coupled panel and vortex particle method (VPM), formulated in state-variable form, to enhance computational efficiency and scalability for aerodynamic simulations. Panels are utilized to model the surface of the wings or blades and the near wake, while vortex particles ar...

The versatility of unmanned aerial vehicles (UAVs) has resulted in a large recent demand for their development, these aircraft can be useful in a variety of fields such as package delivery, search and rescue, agriculture, recreation and others. In particular, quadrotor biplane tailsitter configurations have the potential to become increasingly popu...

This article describes the implementation and analytical linearization of a dynamic rotor simulation with a coupled panel and vortex particle method in state-variable form. Panels are used to model the wing/blade surface as well as the near wake, whereas vortex particles are used to model the far wake. The coupled panel and vortex particle dynamics...

This article describes the development, implementation, and demonstration of dynamic inversion (DI) flight control laws for autonomous transition of tilt-rotor aircraft from hover (helicopter mode) to cruise flight (air-plane mode). The DI control laws are based on a multi-loop architecture and do not require gain scheduling, although they still ne...

This paper presents a novel step in the extension of subspace identification toward the direct identification of harmonic decomposition linear time-invariant models from nonlinear time-periodic system responses. The proposed methodology is demonstrated through examples involving the nonlinear time-periodic dynamics of a flapping-wing micro aerial v...

Early-stage vehicle design processes are typically subject to significant uncertainty in aerodynamic loads and control responses. In many cases, it may be necessary to consider this uncertainty in preliminary evaluations of stability, handling qualities, and performance metrics. This article introduces a novel methodology for computing these quanti...

This study examines the aeromechanics of tiltrotor conversion maneuvers using a coupled simulation approach, integrating the multibody dynamics code MBDyn with the mid-fidelity aerodynamic code DUST. The analytical model is based on the XV-15 tiltrotor with advanced technology blades. The hover and cruise performances of the model are validated aga...

This paper focuses on the integration of a generalized rotor-on-rotor interactional aerodynamics model in state-variable form within a flight dynamics simulation and on its subsequent linearization and linear model analysis. The aircraft chosen for this investigation is a generic lift-offset compound coaxial rotorcraft. Upon trimming the flight dyn...

This paper describes a combined visual and haptic localization experiment that addresses the area of multi-modal cueing. The aim of the present investigation is to characterize accuracy and precision of tactile cue-ing in the peri-personal space (PPS), the space around the body in which sensory information is perceived as meaningful (Ref. 1). Outco...

This paper investigates the relationship between variations in physiological signals, pilot performance, and mental workload during the execution of a roll-attitude compensatory tracking task. In this task, the pilot acts on the displayed error between a desired input and the comparable vehicle output motion to produce a control action. The error i...

This paper describes the implementation and linearization of a coupled panel and vortex particle method in a state-variable form. More specifically, the coupled panel and vortex particle dynamics are formulated as a nonlinear system of ordinary differential equations in first-order form to be self-contained and inherently linearizable. Linearizatio...

This paper presents the development and application of analytical linearization of a State-Space Free Vortex Wake Model. Previous work developed a state-space free wake model that could be numerically linearized via finite differences into a Linear Time Periodic (LTP) system, but the numerical linearization process was computationally expensive. An...

This paper describes the implementation and linearization of a state-space free-vortex wake model with a near-wake vortex lattice model as applied to a helicopter rotor. Following a detailed mathematical description, the wake model is implemented for a blade element model of a utility helicopter rotor and tested in multiple flight conditions includ...

This paper illustrates the development, implementation, and testing of full-body haptic and spatial audio cueing algorithms for augmented pilot perception. Cueing algorithms are developed for roll-axis compensatory tracking tasks where the pilot acts on the displayed error between a desired input and the comparable vehicle output motion to produce...

This article presents the development and implementation of active noise abatement flight control laws utilizing redundant control allocation in rotorcraft. The study starts by finding a periodic equilibrium of coupled rotorcraft flight dynamics and acoustics using a modified harmonic balance trim solution method. Next, the rotorcraft nonlinear tim...

This article demonstrates the linearization of the coupled rotorcraft flight dynamics and aeroacoustics to provide real-time acoustic predictions in generalized maneuvering flight. To demonstrate the methodology, the study makes use of a nonlinear simulation model of a generic utility helicopter (PSUHeloSim) that is coupled with an aeroacoustic sol...

This article describes the implementation, linearization, and model-order reduction of a free-vortex wake model in state-variable form and its use in the real-time prediction of complex aerodynamic interactions during shipboard launch and recovery operations. Following a detailed mathematical description, the wake model is implemented for a UH-60 r...

This article investigates vibrational stabilization effects in rotorcraft flight dynamics. This study is motivated by recent results in flapping-wing flight, which showed that the time-varying aerodynamic and inertial loads due to the insect wing periodic motion induce a vibrational stabilization mechanism in hover. The dynamics of flapping-wing fl...

This paper focuses on the integration of generalized rotor-on-rotor interactional aerodynamics models in state-variable form within flight dynamics simulations of multi-rotor unmanned aircraft systems (UAS), and on their subsequent linearization. The aircraft chosen for this investigation is a resupply coaxial quadcopter. Upon trimming the flight d...

This paper describes the implementation of a coupled panel and vortex particle method in state-variable form for rotary wings. More specifically, the coupled panel and vortex particle dynamics are formulated as a nonlinear system of time-periodic, ordinary differential equations in first-order form with the specific objective for it to be self-cont...

This paper describes the implementation and linearization of a coupled panel and vortex particle method in a state-variable form. More specifically, the coupled panel and vortex particle dynamics are formulated as a system of ordinary differential equations in the first-order form to be self-contained and inherently linearizable. Linearization of t...

This article describes the development, implementation, and validation of a generic tilt-rotor simulation model with coupled flight dynamics, state-variable aeromechanics, and aeroacoustics. A major novelty of this work lies in the integration of the flight dynamics with a state-space free-vortex wake code that adopts a near-wake vortex-lattice mod...

A novel trajectory generation and control architecture for fully autonomous autorotative flare that combines rapid path generation with model-based control is proposed. The trajectory generation component uses optical Tau theory to compute flare trajectories for both longitudinal and vertical speed. These flare trajectories are tracked using a nonl...

This article describes the implementation and linearization of free-vortex wake models in state-variable form as applied to rotary- and flapping-wing vehicles. More specifically, the wake models are implemented and tested for a UH-60 rotor in forward flight and for a hovering insect representative of a hawk moth. A periodic solution to each wake mo...

This paper demonstrates the development, implementation, and testing of spatial audio cueing algorithms for augmented pilot perception. Cueing algorithms are developed for roll-axis compensatory tracking tasks where the pilot acts on the displayed error between a desired input and the comparable vehicle output motion to produce a control action. Th...

This paper investigates vibrational stabilization effects in rotorcraft flight dynamics. This study is motivated by the fact that eigenvalues of the rotorcraft flight dynamics identified from flight test often differ from those computed with physics-based simulations, and that some commonly observed mismatches may be ascribed to vibrational stabili...

This paper demonstrates the development and implementation of active noise abatement flight control laws that make use of redundant control allocation. A periodic equilibrium of the coupled rotorcraft flight dynamics and acoustics is first found at a desired flight condition using a modified harmonic balance trim solution method. Next, the nonlinea...

This paper demonstrates the development, implementation, and testing of full-body haptic cueing algorithms for augmented pilot perception. Full-body haptics is in the form of localized electrical muscle stimulation (EMS) is achieved via a commercial, off-the-shelf product called TESLASUIT. Cueing algorithms are developed for roll-axis compensatory...

This paper describes the development, implementation, and validation of a generic tilt-rotor simulation model with coupled flight dynamics, state-variable aeromechanics, and aeroacoustic. A major novelty of this work lies in the integration of the flight dynamics with a state-space free-vortex wake code that adopts a near-wake vortex-lattice model....

This paper discusses the development of a numerical method for the approximation of the nonlinear time-periodic rotorcraft flight dynamics with higher order linear time-invariant (LTI) models. The method relies on a per-rotor revolution perturbation scheme, which is of particular importance for the linearization of simulation models that do not all...

This paper demonstrates the extension of the harmonic decomposition methodology, originally developed for rotorcraft applications, to the study of periodically-forced fluid flows. Starting from a dynamic systems approach to fluid flows, application of the harmonic decomposition method is demonstrated through two examples involving an oscillating cy...

This paper describes the implementation and linearization of a free-vortex wake model in state-variable form and its use in the prediction of complex aerodynamic interactions during shipboard launch and recovery operations. Following a detailed mathematical description, the wake model is implemented for a UH-60 rotor and tested in different flight...

This paper describes the extension of a free-vortex wake method in state-variable form originally developed for rotary-wing applications to flapping-wing flight. Following a detailed mathematical description, the wake model is implemented for a hovering insect representative of a hawk moth. A periodic solution to the wake model is found at hover us...

This paper describes the implementation and linearization of a free-vortex wake model in state-variable form as applied to a helicopter rotor. Following a detailed mathematical description, the wake model is implemented for a UH-60 rotor and tested in forward flight and for simple control inputs. A periodic solution to the wake model is found by ti...

The objective of this investigation is threefold. First, to assess the flight dynamics of an electric vertical take-off and landing (eVTOL) concept aircraft with a propeller-driven rotor. Second, to develop an automatic flight control system (AFCS) for this concept aircraft. Third, to verify the potential safety benefits of the concept aircraft by...

This paper demonstrates the extension of the harmonic decomposition methodology, originally developed for rotorcraft applications, to the study of the nonlinear time-periodic dynamics of flapping-wing flight. A harmonic balance algorithm based on harmonic decomposition is applied to find the periodic equilibrium and approximate linear time-invarian...

This paper presents a first step in the extension of subspace identification toward the direct identification of harmonic decomposition linear time-invariant (LTI) models from nonlinear time-periodic (NLTP) system responses. The proposed methodology is demonstrated through examples involving the NLTP dynamics of a flapping-wing micro aerial vehicle...

A novel trajectory generation and control architecture for fully autonomous autorotative flare is proposed that combines rapid path generation with model-based control. The trajectory generation component uses optical Tau theory to compute flare trajectories for both longitudinal and vertical vertical speed. These flare trajectories are tracked by...

The objective of this paper is to demonstrate the use of the Julia language for developing complex flight simulation models and performing flight control design. Three simulation models are developed: a simple helicopter model (J-SimpleHel), a higher-fidelity helicopter model (J-GenHel), and a fighter jet model (J-F16). These models are validated a...

The objective of this paper is to summarize the relevant published research studies on the extraction of linear time-periodic (LTP) systems and their higher order linear time-invariant (LTI) reformulations from rotorcraft physics-based models and on the identification of LTP systems from rotorcraft experimental data. The paper begins with an introd...

This paper describes a novel approach to regime recognition based on the notion of motion primitives. Originally developed for path planning, motion primitives decompose a vehicle trajectory into maneuver and trim segments. In a regime recognition context, this decomposition can be used to improve component life tracking through separate classifica...

Condition-based maintenance programs for modern helicopters rely on algorithmic techniques to estimate the useful life remaining for life-limited components. Regime-recognition-based condition-based maintenance programs involve a regime recognition step and a damage estimation step in which damage is calculated based on the identified regimes. Rece...

The paper discusses the development of a novel linearization algorithm to obtain high-order linear time-invariant (LTI) models of the coupled rotorcraft flight dynamics, vibrations, and acoustics. To demonstrate the methodology, the study makes use a nonlinear simulation model of a generic utility helicopter (PSU-HeloSim) that is coupled with an ae...

This paper demonstrates the extension of the harmonic decomposition methodology, originally developed for rotor-craft applications, to the study of the nonlinear time-periodic dynamics of flapping-wing flight. A harmonic balance algorithm based on harmonic decomposition is successfully applied to find the periodic equilibrium and approximate linear...

This paper addresses the use of dynamic inversion with direct load feedback to provide combined load alleviation and flight control of rotorocraft. The method is applied to a compound utility rotorcraft with similar airframe properties as a UH-60A along with a lifting wing. The controller makes use of flaperons and horizontal stabilizer in addition...

In this paper, a numerical method is proposed for determining the periodic state and control solutions of nonlinear time-periodic systems. Starting from an initial guess at the solution, the algorithm uses a harmonic balance technique to refine the solution through a gradient-based optimization approach. The algorithm introduces three major innovat...

An alternative approach to regime recognition that is based on the notion of motion primitives is developed. The algorithm developed is non-causal and leverages the ideas of maneuvers and trims as defined in a motion primitive context. The algorithm functions in three major steps. Given a state and control input time history obtained from flight da...

Modern flight vehicle development typically involves significant uncertainty in aerodynamic loads and vehicle control responses. In many cases, it may be necessary to consider this uncertainty in preliminary evaluations of stability, handling qualities (HQ), and performance. This paper introduces a novel methodology for computing these quantities i...

The objective of this research effort is to assess the impact of load alleviation control on the quantitative handling qualities specifications (also known as predicted handling qualities) of both conventional helicopters and compound rotorcraft in forward flight. First, an overview on how the harmonic decomposition methodology is used toward load...

The objective of this investigation is three-fold. First, to assess the flight dynamics of an electric Vertical Take-Off and Landing (eVTOL) concept aircraft with a propeller-driven rotor. Second, to develop a Stability and Control Augmentation System (SCAS) for this concept aircraft. Third, to verify the potential safety benefits of the concept ai...

The objectives of this paper are to advance dynamic inversion (DI) and explicit model following (EMF) flight control laws for quadrotor unmanned aerial systems (UAS) and to develop an efficient strategy to compute the stability and performance robustness statistics of such control laws given parametric model uncertainty. For this purpose, a paramet...

The present study considers two notional rotorcraft models: a conventional utility helicopter, representative of an H-60, and a wing-only compound utility rotorcraft, representative of an H-60 with a wing similar to the X-49A wing. An explicit model following (EMF) control scheme is designed to achieve stability and desired rate command / attitude...

This paper proposes a novel mathematical methodology for probabilistic handling qualities evaluation using the Koopman operator. The Koopman operator is used to quantify the impact of parametric uncertainty in a pilot model to specific pilot-vehicle system performance specifications and to perceived vehicle handling qualities. The considered specif...

The objective of this research effort is to develop rotorcraft flight control laws that minimize unsteady rotor loads by acting solely through the primary flight controls (first harmonic swashplate control). As opposed to Higher-Harmonic Control, this strategy does not affect stationary (periodic trim) loads, and is therefore effective only in mane...

The objective of the paper is to study the F-Helix eVTOL concept. This concept modifies the SH-4 Silvercraft light helicopter to use electric propulsion and a tip driven rotor. It is intended to compete with rotorcraft in the lightweight class and address future urban air mobility needs. The elimination of shaft driven propulsion is intended to red...

The objective of this paper is to develop helicopter flight control laws that minimize unsteady rotor loads while meeting desired handling qualities. These control laws are meant to act solely through the primary flight controls. First, an overview on how the harmonic decomposition methodology is used towards load alleviation control is presented....

A quadrotor was assembled with commercial off-the-shelf (COTS) components readily available on the market as a platform for future research at Penn State. As a first step in this research, a model of the quadrotor is identified from flight data. Given the largely decoupled dynamics at low speed, frequency sweeps in different channels are performed...

The present study considers two notional rotorcraft models: a conventional utility helicopter, representative of an H-60, and a wing-only compound utility rotorcraft, representative of an H-60 with with a wing similar to the X-49A wing. An Explicit Model Following (EMF) control scheme is designed to achieve stability and desired Rate Command / Atti...

An Explicit Model Following (EMF) control scheme is designed to achieve stability and desired Rate Command / Attitude Hold (RCAH) response around the roll, pitch and yaw axes, while alleviating vibratory loads through both feed-forward and feedback compensation. First, the effect of command model tailoring is explored to understand the effect of fe...

This study presents the integration of a flight simulation code (PSUHeloSim), a high fidelity rotor aeromechanics model with free wake (CHARM Rotor Module), and an industry standard noise prediction tool (PSU-WOPWOP) into a comprehensive noise prediction system. The flight simulation uses an autonomous controller to follow a prescribed trajectory f...

This paper is focused on gaining a deeper understanding on how different flight procedures relate to noise generation and how helicopter rotor noise may be abated. The paper describes a noise prediction system composed of a flight simulation model, a rotor airloads and airwake model, and a rotor noise prediction code which can be used to predict th...