Institute of Fundamental Technological Research

In this paper, the authors propose, investigate, and discuss a concept of novel type of deployable helium-filled aerostat as a low-cost mean of transport. Internal construction of the aerostat is based on ultra-light tensegrity structure equipped with prestressed tensioned elements of controllable lengths. Such tensegrity structure allows for adaptive morphing of the aerostat understood as simultaneous controllable modifications of aerostat volume and shape during the flight. The controlled volume changes enable influencing buoyancy force and obtaining desired vertical motion during the ascending and descending process. In turn, external shape changes allow for lowering the aerodynamic drag and energy usage needed to uphold stable horizontal position or maintain the desired flight path. Moreover, such internal structure allows for convenient storage, transportation and deployment of the aerostat construction on the ground or in required point at the atmosphere. The article presents an analysis of the exemplary operational mission of the aerostat. The authors introduce the mechanical model capturing interaction of the internal tensegrity structure and aerostat envelope based on the finite-element method, as well as dynamic model allowing for simulation of the aerostat’s vertical and horizontal motion influenced by buoyancy and drag forces. Both these models are used to positively verify the feasibility of the proposed concept of deployable tensegrity-based aerostat with adaptive morphing and its efficiency in realization of the assumed flight mission.

tensegrity structure, internal construction, shape modification, helium-filled aerostat, vertical mobility, horizontal mobility

In this article, the authors propose and investigate a new concept of HAPS aerostat design in a modular form, which allows for sequential increasing or decreasing of the total volume, up to the desired size. In its initial form, the aerostat has relatively small dimensions but its central cylindrical part is multi-segmented and can be easily extended. The application of controllable construction couplings enables precise control of the aerostat expansion process and significantly improves its vertical mobility. The paper describes details of telescopic aerostat construction, presents a mathematical model of its vertical motion and investigates numerically two volume control strategies aimed at maximization of operation efficiency and minimization of operation cost. The results obtained reveal the main problems that have to be addressed and the factors that play a key role in design of such telescopic aerostats and control of their vertical mobility.

helium airship, control of vertical mobility, reduced energy consumption, optimum ascending and descending path

This paper introduces and discusses a new concept of impact absorption by means of impact energy management and storage in dedicated rotating inertial discs. The effectiveness of the concept is demonstrated in a selected case-study involving spinning management, a recently developed novel impact-absorber. A specific control technique performed on this device is demonstrated to be the main source of significant improvement in the overall efficiency of impact damping process. The influence of various parameters on the performance of the shock-absorber is investigated. Design and manufacturing challenges and directions of further research are formulated.

adaptive impact absorption, adaptive inerter, semi-active control, shock-absorber

The main objective of this paper is to investigate the possibility of local structural vibration uppression via introducing initial prestressing. In order to evaluate the effectiveness of the proposed method, a two-step approach has been used. Firstly, a prestressed modal analysis has been conducted to measure the influence of the prestressing on changes of eigenfrequencies and eigenmodes. In the second step, a steady dynamic analysis has been performed to harmonic excitation to demonstrate the reduction of local amplitudes. Numerical experiments have been conducted on the model of a small rotorcraft. Our results indicate that introduction of initial prestressing may be used to affect natural structure frequancies and to lower amplitude of vibrations of the structure exposed to external extortions.

Prestressing, vibration suppression.

The contribution describes three innovative external airbag systems developed by the
authors for the protection of flying objects during emergency landings. The first one is the
AdBag system dedicated for small drones, which is designed to protect the carried equipment
and prevent damages to objects or injuries to people at the crash location. The second system
is external airbag designed for ultralight aircraft Skyleader 600, which provides significant
reduction of touchdown velocity and deceleration levels during emergency landings, thereby
improving protection of the pilot and the passengers. Finally, the last presented solution is the
Spring-Drop system with specialized airbag deployment technique, which is dedicated for
specialised airdrop operations where the touchdown conditions can be extremely harsh and
unexpected, while protection of transported cargo is of crucial importance. Both conceptual
studies, numerical simulations and experimental tests of the three proposed systems are
presented and discussed.

External airbags, adaptive system, emergency landing, human safety

This contribution introduces the concept of sky sailing, which combines the
advantages of airships and standard fixed-wing aircraft, albeit in a vertical plane alignment.
The proposed vehicle is equipped with rigid aerodynamic sails and auxiliary engines, enabling
navigation and control with minimal power consumption along the desired trajectory. The
proper orientation of the airship relative to the wind direction is achieved through the
adjustment of the sails' angle of attack and the use of auxiliary lateral engines. Consequently,
the system enables efficient maneuvering, particularly in windy conditions, while requiring low
energy input. In the current stage of our research, we focus on 2D sky sailing in a horizontal
plane. This study formulates mathematical model which employs a combined approach of
analytical methods and numerical simulations based on finite volume method. Then, the
corresponding control problem aimed at following the desired fly path with the lowest possible
energetic cost. The motivation behind this work stems from the potential applications of aerial
monitoring, such as crop or forest surveillance.

Airship, flight control, optimization, aerospace

In this contribution, the authors propose a concept of novel type of an ultra-light helium-filled aerostat. The internal construction of the proposed aerostat is based on a self-deployable tensegrity structure equipped with prestressed tensioned elements of controllable lengths. Such construction enables convenient transportation of the aerostat and its fast deployment at the required operational point at the atmosphere. The controllable tensegrity structure can be used for simultaneous changes of the aerostat volume and external shape during the flight. This enables modification of buoyancy and drag forces and obtaining a desired vertical and horizontal motion as well as a desired flight path. The authors propose a method of numerical modelling of self-deployable helium-filled aerostats based on the finite element method as well as CFD and FSI models presenting behaviour of aerostat during typical operational conditions. The presented results show the interaction of the internal tensegrity structure and aerostat envelope and positively verify the feasibility of the proposed concept of tensegrity-based aerostats.

tensegrity structure, internal construction, helium-filled aerostat, numerical modelling

In this contribution the authors propose and investigate the concept of adaptive morphing for recently introduced tensegrity-based helium-filled aerostats. The proposed aerostat is based on an ultra-light tensegrity structure equipped with prestressed ensioned elements of controllable lengths. Such internal structure allows for adaptive morphing of the aerostat defined as simultaneous controllable modifications of aerostat volume and external shape during the flight. The controlled volume changes enable influencing buoyancy forces acting on the envelope and obtaining desired vertical motion of the aerostat during the ascending and descending process (“vertical mobility”). In turn, the controlled changes of external shape of the aerostat can be used either for lowering the aerodynamic drag forces and reducing energy usage needed to maintain stable horizontal position or to follow the desired path of aerostat horizontal motion (“horizontal stability”). The authors effectively apply the previously introduced mechanical FEM model of the tensegrity-based aerostat and dynamic model of the aerostat’s vertical and horizontal motion to conduct simulations of the process of adaptive morphing and maintain a proper position in the atmosphere. The obtained results positively verify the idea of adaptive morphing and its efficiency in controlling vertical and horizontal motion of the aerostat.

tensegrity structure, helium-filled aerostat, adaptive morphing, vertical mobility, horizontal stability

In this article we propose a new concept of adaptive telescopic high-altitude aerostat designed in a modular form which allows for sequential changes of volume during the flight. The proposed telescopic aerostat can be easily enlarged or contracted due to application of multi-segmented construction, controllable segments’ couplings and precise adjustment of internal pressure obtained using additional gas tank, valve and compressor. Conducted changes of aerostat volume allow to precisely control generated lift force and to obtain desired paths of ascending and descending. The paper briefly presents development of control strategies aimed at: i) reaching the subsequent altitudes in the shortest period of time, ii) reaching these altitudes at the smallest cost defined as total work done by the compressor. The obtained results show high potential of the proposed innovative concept of the aerostat.

helium airship, control of vertical mobility, reduced energy consumption, optimal ascending and descending paths

Adaptive structures, equipped with so-called structural fuses (based on fast responding piezo-devices), able to connect/disconnect instantly selected structural interface, allows effective protection against resonance induction via externally forced vibrations. The presented case study demonstrates haw forced vibrations with modifiable frequencies can be smoothly received, if structural fuses are properly activated/deactivated when the external excitation approaches the structural eigen frequencies.

Adaptive structures, forced vibrations, avoiding resonance, structural fuses

Pneumatic dampers are still an attractive subject of research in both modelling and experimental testing. Progress in the field of sensors and actuators allows to construct more and more efficient absorbers and dampers based on active or semi-active control algorithms. However, passive and semi-passive solutions are also developed because of their lower costs and simplicity. This paper presents adaptable pneumatic shock-absorber that allows to obtain optimal impact absorption and energy dissipation by a single reconfiguration performed at the beginning of the process. The absorber is composed of two cylinders including at least one narrow rectangular slot and adequate number of outflow vents precisely shaped for certain impact scenarios. During operation of the device the air is released through overlapping slots and selected vents, which provides constant value of the generated force. As a result, the shock-absorber works as a passive device but provides minimal value of the reaction force in similar manner as semi-active system equipped with fully controllable mechanical valve. The paper presents the results of numerical simulations of adaptable shock-absorber operation and attempts of demonstrator construction aimed at conducting experimental verification of the concept.

Adaptable, Semi-passive, Impact Absorption, Pneumatic Shock-absorber

The problem of dynamic response stabilization is a crucial issue in many engineering applications or structures subjected to an external source of excitation or dynamic load. At present, owing predominantly to advances in measurement technology, microprocessor control and development of smart materials it is possible to solve many of these problems. Semi-active or active damping systems, which are used to improving structure response, requires additional dampers or absorbers. Contrary, in the article we present approach of suppressing local vibration via introducing initial prestressing into the chosen element or elements of the structure. In that way it is possible to change properties of the structure and its modes of vibrations. We present the results of numerical simulations of the mechanical structure subjected to external excitations. Our results show that by introducing prestressing it is possible to significantly influence on eigenfrequances and eigenmodes. Also effectiveness of vibration amplitudes reduction can be significantly larger, at least one order of magnitude larger.

local suppresion of forced vibrations, prestressing, sensitivity analysis and prestress optimization

Air-drop Capsule, Impact Mitigation, Adaptable Airbag, Discharge Valve

The problem of safe, impact loads absorption is present in a wide class of applications, and particularly where direction of the object's movement is well-defined, for example: precise docking systems, rail car buffers or landing gear shock absorbers. In those applications the objective is to absorb gradually impact energy, minimizing the deceleration peak. For safety reasons, the class of drop-caps (eg. in delivery business) or bigger airdrops from airplanes or from stratospheric airships (space debris) becomes a challenge for next decades. However, knowing the dropping mass and estimating the touchdown velocity, our SAI shock-absorbers (cf. [1]) made of multi-layered, "delaminable" panels, can be adapted to the expected impact. Therefore, let us concentrate on the SAI concept based on the following steps: -- design a multi-layer structure capable of semi-active "delamination" control along the contact infrastructure (slipping lines). -- apply an actuator realizing the on/off type of semi-active control for slipping lines' activation, playing the role of structural clutch (cf. the actuator in the so-called PAR vibration suppression technique, [2-3]), -- apply various characteristics for the contact interfaces (friction coefficient), -- apply various control strategies for the slipping lines activation (and releasing of the pre-stress effect), depend on the case study and identified on-line impact parameters. The effectiveness of the proposed, adaptive approach to impact absorption (so-called Depress Dampers) will be compared versus traditional shock-absorbers, based on passive honeycomb panels (cf. also adaptive pneumatic shock-absorber concept).

Pneumatic dampers are still an attractive subject of research in both modelling and experimental testing. Progress in the field of sensors and actuators allows to construct more and more efficient absorbers and dampers based on active or semi-active control algorithms. However, passive and semi-passive solutions are also developed because of their lower costs and simplicity. This paper presents adaptable pneumatic shock-absorber that allows to obtain optimal impact absorption and energy dissipation by a single reconfiguration performed at the beginning of the process. The absorber is composed of two cylinders including at least one narrow rectangular slot and adequate number of outflow vents precisely shaped for certain impact scenarios. During operation of the device the air is released through overlapping slots and selected vents, which provides constant value of the generated force. As a result, the shock-absorber works as a passive device but provides minimal value of the reaction force in similar manner as semi-active system equipped with fully controllable mechanical valve. The paper presents the results of numerical simulations of adaptable shock-absorber operation and attempts of demonstrator construction aimed at conducting experimental verification of the concept.

Adaptable, Semi-passive, Impact Absorption, Pneumatic Shock-absorber.

The goal of this paper is to present further development of the inertial shock-absorber called SPINMAN. Application of the device in mitigation of structures response is investigated and selected case study is discussed. The specific construction and operation of the device is introduced and explained. In reference to the impact absorption problems, the SPIN-MAN is a concept of adaptive inerter device with two phases of operation. The first of them includes energy absorption and accumulation. External energy of the load is converted to kinetic energy of rotational motion of the mass. During the second phase, accumulated energy is dissipated by inverse spinning of the second mass powered by the remaining part of the impact energy. To obtain this type of operation, special switchable actuators are used. Applicability of the device in mitigation of impact-born structure response, especially in case of space systems, is investigated. General concept of the device construction and operation is adjusted to meet the requirements for space systems. This results in a fluidless, passive-like solution but adaptable to the load conditions. Tuning of the shock-absorber may be realized by manual or easily automated mechanical adjustments. Effectiveness of the solution is based on the specific on/off type of control, which is responsible for the optimal energy flow in the system and efficient dissipation of impact energy inside the SPIN-MAN. Results of numerical simulations confirmed quick and effective operation of this device.

structure response mitigation, adaptive impact absorption, adaptive inerter, semi-active control, shock-absorber