Florian Holzapfel

• Prof. Dr.-Ing.
• Institute Director at Technical University of Munich

Pseudoinverse-based control allocation (CA) methods like redistributed scaled pseudoinverse are popular options for control allocation of safety-critical systems with limited computational power, such as aircraft, unmanned aerial vehicles, and spacecraft. Those methods may require the online computation of the pseudoinverse of the control effective...

The edm aerotec CoAX 600 rotorcraft was converted to an uncrewed aerial vehicle at the Technical University of Munich. In this work, a higher-order physics-based model of the system was identified based on flight test data and blade element momentum theory (BEMT). The paper describes the higher-order model structure and the system identification te...

Background: Robotic autonomous systems (RAS) are currently being used successfully on land, air and sea to carry out a wide range of military tasks. Integrating RAS into the military rescue chain can bring numerous advantages. For example, it allows the evacuation of patients from contaminated areas without putting additional personnel at risk. Fu...

A model for the dynamic pressure loss in standard oleo-pneumatic shock absorbers without gas-oil separator for avionics applications is introduced. The dynamics of such a device under load variations are primarily determined by the throttle between the oil chamber and the gas chamber. During operation, gas is absorbed by the oil upon compression an...

Dynamic soaring is a technique employed by some kinds of birds to extract energy by intelligently flying in shear wind. The combination of trajectory optimization and path following is currently the most used duo in real-world application of dynamic soaring. However, the separate design of the trajectory and the controller inherently introduces a f...

Aerodynamic parameters of high-fidelity nonlinear flight dynamic models are usually formulated as a Taylor expansion of each non-dimensional force and moment coefficient as a function of several explanatory variables, e.g., aerodynamic angles, rigid body rates and control deflections. This paper presents a generic formulation of the aerodynamic mod...

A nonlinear global dynamic model is presented for a general aviation aircraft. The model is estimated from flight data using output-error in the time domain. Orthogonal phase-optimized multisines, frequency sweeps, and conventional handbook maneuvers are prepared and injected open-loop at several flight conditions. The maneuvers are injected automa...

Aircraft flight mechanics clearance requires extensive computer simulation to verify compliance with safety-relevant system requirements. To identify critical regions within the flight envelope, the clearance problem can be formulated as an optimization problem, concerned with identifying worst-case scenarios. This paper demonstrates the capability...

Programmed test inputs were injected open-loop on a general aviation aircraft for system identification and parameter estimation. The flight test campaign included in total 9 flights with approximately 250 carefully designed maneuvers, including conventional multisteps, frequency sweeps, phase-optimized orthogonal multisines, and optimal inputs. To...

This paper presents a straightforward, practical synchronization method for distributed flight control computers (FCCs): the Event-sync Protocol for Flight Computer Networks (EPFCN). As physically dispersed processors do not have a common knowledge of time, this causes asynchronous behavior among the FCCs. All processors can read and vote input val...

Applications of unmanned aerial vehicles are on the rise. Particularly within the healthcare sector, the potential is huge as it is cited as the most accepted application. This paper introduces an agent-based simulation to evaluate the network performance of UAV-based logistics networks in healthcare. The simulation is applied to a hypothetical rea...

Rapid developments in aerospace technologies demand reliable procedures to plan robust missions with high safety. To increase safety under uncertainties in model parameters or environmental conditions, multi-objective robust optimization methods via sensitivity minimization can be used. An acceptable trade-off between a nominal operational cost (e....

Assessing handling qualities is crucial for ensuring the safety and operational efficiency of aircraft control characteristics. The growing interest in Urban Air Mobility (UAM) has increased the focus on electric Vertical Takeoff and Landing (eVTOL) aircraft; however, a comprehensive assessment of eVTOL handling qualities remains a challenge. This...

Solid organ transplantation continues to be the only or most efficient therapeutic solution for several end-stage diseases. The success of such transplantation is largely dependent on the swift transportation of organs from donors to recipients, as Cold Ischemia Time (CIT) plays a critical role in determining the recipient’s medical outcome. This s...

In this paper, we present a method to optimize the attainable moment set (AMS) to increase the control authority for electrical vertical take-off and landing vehicles (eVTOLs). As opposed to 3D AMSs for conventional airplanes, the hover control of eVTOLs requires vertical thrust produced by the powered lift system in addition to three moments. The...

In this paper, we present a method to optimize the attainable moment set (AMS) to increase control authority for electrical vertical-take-off-landing vehicles (eVTOLs). As opposed to 3D AMS for conventional airplanes, hover control of eVTOLs requires vertical thrust produced by the powered lift system in addition to three moments. The limits of the...

Many control allocation algorithms require the calculation of (pseudo)inverses of control effectiveness matrices, also referred to as a [Formula: see text] matrix, which for nonlinear systems might change over time. Such cases would require an online calculation of the respective inverses. Storage of all possible, offline precalculated inverses mig...

Assessing handling qualities is crucial for ensuring the safety and operational efficiency of aircraft control characteristics. The growing interest in Urban Air Mobility (UAM) has increased the focus on electric Vertical Take-Off and Landing (eVTOL) aircraft; however, a comprehensive assessment of eVTOL handling qualities remains a challenge. This...

Zusammenfassung Das deutsche Gesundheitswesen steht vor einem großen Umbruch. In der Politik werden weitreichende und wegweisende Reformen für die mittel- bis langfristige Entwicklung diskutiert. In der aktuellen Zeit besteht die Chance und das Potenzial, Dinge neu zu denken und Türen für neue Technologien zu öffnen. Eine transformative Technologie...

This paper presents an onboard optimization approach used to generate trajectories for Radius to Fix (RF) turns within an integrated flight guidance and control system. An Optimal Control Problem (OCP) is formulated such that it accounts for the geometric constraints of the RF leg as well as the dynamics and limitations of the closed-loop controlle...

Introduction: In large scale combat scenarios, it is very challenging to adhere to the tight timelines for optimal casualty care. This becomes even more difficult if areas are difficult to access or contaminated. Autonomous systems have emerged as a disruptive technology in current conflicts, offering new opportunities in the context of care for...

A coaxial helicopter with a maximum take-off weight of 600 kg was converted to an unmanned aerial vehicle. A minimally invasive robotic actuator system was developed, which can be retrofitted onto the copilot seat of the rotorcraft in a short period of time to enable automatic flight. The automatic flight control robot includes electromechanical ac...

This paper presents a method to assess a novel procedure for Air Traffic Controllers, enabled by predictions of a machine learning-based go-around prediction model, regarding the operational risk of separation infringements and traffic alarms. In a previous work, potentially novel procedures were elaborated in human-in-the-loop simulations with Air...

Machine learning-based go-around predictions have been discussed in the research community for some years. Much work has been done developing algorithms and testing their accuracy, motivated by the assumption that time-in-advance information on the go-around likelihood of arrival aircraft will benefit air traffic controllers. The question of how to...

Trajectory optimization is an essential tool for the high-fidelity planning of missions in aerospace engineering in order to increase their safety. Robust optimal control methods are utilized in the present study to address environmental or system uncertainties. To improve robustness, holistic approaches for robust trajectory optimization using sen...

An aircraft configuration-agnostic strategy for unified trajectory control of a VTOL transition or a VTOL aircraft was introduced in this paper. Translation jerk dynamics, expressed in the 𝐶-frame, are derived from the rigid-body kinematics to determine the position jerk error dynamics and establish the necessary terms for generating the feedforwar...

Accurate trajectory-following control using dynamic inversion controllers requires suitable parameterizations of reference trajectories, such as energy-minimal flight paths generated with optimal control methods. These trajectory representations must enable efficient onboard storage and real-time evaluation while ensuring sufficient accuracy and sm...

Optimal control methods are widely used to generate flight trajectories for aerial vehicles. These optimal control problems are generally non-convex due to nonlinear flight dynamics and constraints. This study integrates a collocation framework with successive linear programming to address non-convex trajectory generation problems. A linear progra...

In recent years, various approaches for adaptive control allocation have been published with the goal to enable fault tolerance and improve flight performance of overactuated vehicles. Most of the presented methods are based on Model Reference Adaptive Control (MRAC) techniques and/or recursive least squares. In this study, we present a novel strat...

The potential future of personal transportation and taxi services may be in some sectors beneficially amended with electric vertical take-off and landing (eVTOL) aircraft. Currently, dozens of companies are actively engaged in the development of eVTOLs, with the imminent commercialization of several vehicles. This article delves into the requiremen...

This paper introduces an approach for evaluating and quantifying the controllability of vertical takeoff and landing (VTOL) aircraft across various flight states. By employing the controllability theory for linear systems subject to bounded control, this study derives sufficient conditions for the local controllability of the nonlinear VTOL system....

Applications of Unmanned Aerial Vehicles (UAVs) are on the rise. Particularly within the healthcare sector the potential is huge as its cited as the most accepted application. This paper introduces an agent-based simulation to evaluate the network performance of UAV-based logistics networks in healthcare. The simulation is applied to a hypothetical...

This paper proposes a model of the diffusion and electrical dynamics of lithium-polymer batteries through a lumped parameter approach. Discharge experiments were performed on a set of three battery cells using a programmable DC load. The resulting data sets were used to obtain several model parameters using different optimization approaches. A comp...

An incremental differential proportional integral (iDPI) control law using eigenstructure assignment gain design is tested in flight on a subscale platform to validate its suitability for fixed-wing flight control. A kinematic relation for the aerodynamic side-slip angle rate is developed to apply a pseudo full state feedback. In order to perform t...

The development of flight software for Unmanned Aerial Systems (UAS) is challenging due to the absence of an established development process defined by aerospace certification authorities. This research paper outlines our methods and tools for analyzing flight-critical UAS control software on the target hardware. We present our toolchain and method...

A model for the dynamic pressure loss in standard oleo-pneumatic shock absorbers without gas-oil separator for avionics applications is introduced. The dynamics of such a device under load variations is primarily determined by the throttle between the oil chamber and the gas chamber. During operation, gas is absorbed by the oil upon compression and...

The emergence of eVTOL (electrical Vertical Takeoff and Landing) aircraft necessitates the development of safe and efficient systems to meet stringent certification and operational requirements. The primary state-of-the-art technology for flight control actuation in eVTOL aircraft is electro-mechanical actuators (EMAs), which heavily rely on multip...

Urban Air Mobility (UAM) has emerged in response to increasing traffic demands. As UAM involves commercial flights in complex urban areas, well-established automation technologies are critical to ensure a safe, accessible, and reliable flight. However, the current level of acceptance of automation is insufficient. Therefore, this study sought to ob...

The use of non-piloted eVTOL aircraft in non-segregated airspace requires reliable and deterministic automatic flight guidance systems for the aircraft to remain predictable to all the users of the airspace and maintain a high level of safety. In this paper we present a 3D trajectory generation module based on clothoid transition segments in the ho...

Fuel efficient coordination of aircraft operations in the Terminal Maneuvering Area of large airports can contribute to the reduction of the environmental impact of air traffic. To exploit the full potential of the air traffic system, coordinated routing in the Terminal Maneuvering Area, runway assignment and scheduling need to be optimized conside...

This paper presents a mission data-handling algorithm that provides a data link interface between a flight control computer (FCC) and a ground control station (GCS) using the protocol standard STANAG 4586, AEP-84 Volume II. A subset of defined messages is used for the transmission of mission and area definition data. Functions for decoding uplink m...

This paper presents a holistic safety-critical software development process according to DO-178C/DO-331 standards, which is being used at the Institute of Aeronautical Engineering at the University of the Bundeswehr Munich. A software development process for embedded systems is comprised of several steps, including requirements gathering and analys...

In Europe, there are no adequate training programs or requirements for rotary wing UAVs over 25 kg. This does not reflect the fact, that there are increasing numbers of developed systems with higher maximum takeoff mass. As such systems are evaluated to be much more hazardous for their environment in case of malfunctions or pilot mistakes, the trai...

A comprehensive understanding of electromagnet behavior is crucial for advancing levitation system development, particularly in high-speed transportation. This paper presents a non-linear magnetic circuit model for analyzing static and dynamic behavior of a magnetic levitation system. The model accommodates iron saturation and the impact of eddy cu...

The advancement of electric vertical take-off and landing (eVTOL) aircraft has expanded the horizon of urban air mobility. However, the challenge of generating precise vertical take-off and landing (VTOL) trajectories that comply with airworthiness requirements remains. This paper presents an approach for optimizing VTOL trajectories considering si...

div>This work introduces a practical approach to external synchronization for flight control computers (FCCs) deployed in a decentralized fashion. The internal synchronization among the FCCs in distributed flight control systems needs to be extended for specific applications, necessitating an urgent need for an external synchronization mechanism. F...

This paper discusses a possible solution to allow rapid prototyping of augmented reality content for evaluating user assistance systems. Building upon current approaches from the automotive context, it presents options to transfer these to the aerospace context, focusing on upcoming electric Vertical Take-Off and Landing aircraft. By showing issues...

System identification methods have played an essential role in the research and industry projects at the Institute of Flight System Dynamics of the Technical University of Munich. Besides the application of the established system identification approaches to multiple aircraft, novel methods have been developed at the institute to deal with the chal...

This study presents a Recursive Least Squares (RLS) based approach for adaptive control allocation. The algorithm is premised on the least squares based modification for adaptive control and guarantees convergence under the condition of linear independent data. We modified the adaptation law for control allocation to adapt the control effectiveness...

Sowohl zivile Großschadenslagen wie z. B. die Starkregenkatastrophe 2021 in Rheinland-Pfalz und Nordrhein-Westfalen als auch der Angriffskrieg in der Ukraine machen deutlich, dass in der zivilen wie in der militärischen Notfall- und Rettungsmedizin immer wieder die Herausforderung bestehen wird, eine größere Anzahl an Opfern lokalisieren, stabilisi...

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