Vibration Dampening for UAVs

Mounting system for attaching mission equipment like cameras and sensors to drones that allows flexible configuration of the drone and equipment. It uses a specialized mount apparatus that connects to the drone body and provides a separate mount for the equipment. This allows swapping and upgrading mission equipment without replacing the drone. The mount apparatus has a unique frame shape with dampers between connected frames to absorb vibrations.

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Modular integration kit for positioning systems on vehicles, comprising a configurable foundation plate, a dampened bolting structure, and a modular vibration isolation assembly. The foundation plate attaches to the positioning system, while the dampened bolting structure secures payloads. The vibration isolation assembly, comprising bayonet-style shock absorbers, connects the foundation plate and bolting structure to dampen vibrations. The kit is adaptable to various turret configurations and sizes, and can be used with sensitive payloads such as optics and weapons systems.

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Vibration isolator strut for spacecraft components like reaction wheels that provides isolation during launch and stable control afterward. The strut has a shaft with stops at each end that engage cavities to limit overload. Springs between the shaft ends isolate vibrations. A damper between the springs further dampens vibrations. The strut design allows high force launch loads to stop at the stops, then flex and damp after launch.

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Unmanned aerial vehicle (UAV) with soft arm propulsion vectoring that enables safe navigation around obstacles and minimizes damage. The UAV features flexible arms that bend upon collision, cushioning impacts while actively decelerating the contact. The arms are integrated into a propeller housing that houses a ducted fan, enhancing thrust efficiency while maintaining safety against environmental collisions. This innovative design enables the UAV to safely operate in environments where traditional hard-point protection would compromise maneuverability.

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Abstract Vibration is a very common phenomenon in helicopter flight, and its main source is the combined excitation force on the paddles as they rotate. In order to attenuate this harmful phenomenon, helicopter paddles are usually fitted with vibration absorbers. The helicopter rotor blade root single pendulum vibration absorber is a typical passive control type dynamic vibration absorber, which has a better vibration absorbing function, but also has certain difficulties in dynamics analysis. In this paper, a linearized dynamics analysis of the single pendulum vibration absorber is carried out, and a dynamics model of the paddle root single pendulum vibration absorber coupled with the paddle blade is established; a typical helicopter rotor system model is constructed by using Matlab, and further modeling and simulation comparisons are carried out by using ADAMS. According to the results of simulation and analysis, the unidirectional vibration level of the rotor hub can be reduced by 85% after the paddle root single pendulum absorber is installed, and the error with the theoretical an... Read More

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Abstract The delivery of medical products by drone is potentially game-changing and promises increased speed, particularly when trying to service hard to reach rural areas, and reduced carbon emissions. However, this raises a number of questions, including the effects of flight on the stability of medical products and how this can be mitigated through the design of appropriate packaging. The aim of this study was to design and experimentally evaluate a medical goods package capable of mitigating the vibration experienced during transportation by drone. Two proposed designs have been developed that feature coil spring and wire rope isolators. Transmission of vibration by these prototype packages, together with an industry-standard product, was measured both in the laboratory and in transportation trials. The prototype packages reduced transmitted vibration by a factor of six during drone flight tests but performed slightly worse when transported by car since road inputs occur at characteristically lower frequencies. The prototypes are significantly heavier than the standard product wh... Read More

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The advancement of sensor, actuator, and flight control technologies has increasingly expanded the possibilities for drone utilization. Among the technologies related to drone applications, the vibration isolator technology for payload has a significant impact on the precision of optical equipment in missions such as detection, reconnaissance, and tracking. However, despite ongoing efforts to develop vibration isolators to mitigate the impact of vibrations transmitted to optical equipment, research on drone-specific natural frequencies and payloads has been lacking. Consequently, there is a need for research on vibration isolators tailored to specific drone types and optical equipment payloads. This study focuses on exploring the correlation between the natural frequencies of drones and the weight of the payload, and proposes methods for developing and testing vibration isolators that consider both factors. To achieve this, the study measured the stiffness of vibration isolator rubbers and conducted cross-validation between random vibration tests and finite element method (FEM) analy... Read More

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Rotorcraft experience significant vibrations due to periodic aerodynamic forces and moments on the rotor blades and wings. Rotor torque damping is a novel vibration damping method which uses small torque perturbations from the main electric motor to reduce vibrations. The large inertial and aerodynamic rotor loading and relatively high frequency torque perturbations mean that the rotor speed changes are small, so the rotor thrust and flight control performance are not significantly affected. This paper investigates the application of electric motor torque control for damping structural vibrations of an aircraft. The structural dynamics of the aircraft are represented using a finite element model of a quad tiltrotor eVTOL. Using collocated angular rate feedback on all four rotors provides more than 10% damping in controllable modes. The RMS value of flap-wise angular rate can be reduced by 91% with less than 1.2 RPM rotor speed change in response to a 20% vertical step gust in airplane mode. For N/rev disturbance cancellation, an optimal controller is designed assuming known disturban... Read More

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Relevance. Mechanical vibrations are a common and technically important process that has a negative acoustic effect on human health and in some cases is a harmful production factor. In devices, the presence of vibration is caused by exciting influences of various physical nature: mechanical, electromagnetic, aerodynamic. The reason for their occurrence are defects in parts and assemblies, the technical principle of the ball bearing device, as well as the coincidence of the operating frequency of the device with natural frequency of the structural elements. Since it is technically impossible to completely eliminate the vibration activity of an electromechanical device, the actual topic of scientific research is the technical task of developing a damping device with determining its effectiveness to reduce the vibration activity of an electromechanical device, thereby minimizing the effects of concomitant harmful production factors on humans. To study this problem, a 3D model of the construction of a solid-state damper based on aluminum foam has been developed, according to which two la... Read More

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A vibration damping assembly for optical elements, comprising a base layer, a constraining layer, and a viscoelastic damping layer, wherein the constraining layer is positioned between the base layer and the damping layer, and the damping layer is positioned between the constraining layer and the optical element, to effectively reduce and/or eliminate ambient vibrations from transferring to the optical element.

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Vibration damping in aerospace structures can decrease the likelihood of failures and instabilities and improve passenger comfort. This paper introduces the novel idea of damping vibration using the electric proprotors on aircraft without compromising flight control. The equations of motion of a cantilevered beam with a propeller at the tip driven by an electric motor are obtained using Hamiltons principle, solved analytically in the frequency domain, and approximately in the time domain. Feeding back the beam tip angular rate to the motor torque is shown to asymptotically stabilize all transverse beam vibration modes. The overall vibration control consists of the inner rate feedback damping loop with an outer rotor speed control loop. Experimental frequency response and step response validate the models and show that the closed-loop damping in the first mode is three times higher than open loop with less than 1% rotor speed change for a 3% initial tip displacement. Theoretical results give good agreement with experiments. Parametric studies based on a 12 kg quadcopter indicate that... Read More

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An active vibration control system for rotor hubs of rotary-wing aircraft that reduces rotor-induced vibrations transmitted to the airframe. The system comprises a force generating device attached to the rotor hub, which rotates at the rotor speed and generates vibratory shear forces through high-speed unbalanced weights. The system uses feedback from vibration sensors to control the amplitude and phase of the generated forces, minimizing vibrations transmitted to the airframe.

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Vibration control techniques are various methods and devices designed to suppress unwanted vibrations, ultimately enhancing system performance and mitigating potential adverse effects. These techniques are widely applied in modern engineering, deducting the detrimental consequences of excessive vibrations, such as structural damage, noise generation, energy waste, and compromised functionality. The general classification of vibration control techniques includes passive, active, and semi-active control. Specifically, passive techniques like Tuned Mass Dampers (TMDs), active techniques like inertia mass actuators, and semi-active control devices such as magnetorheological dampers (MR dampers) are examined in this paper. Meanwhile, structural characteristics, mathematical models using formulas, and applications across diverse fields are analysed for each category. Moreover, efficiency analysis of all the discussed devices for vibration control is conducted through comparative analysis and detailed evaluation. In this case, valuable insights are gained regarding the overall effectiveness... Read More

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A rotor for a hover-capable aircraft, such as a helicopter, that reduces transmission of vibrations to the fuselage. The rotor includes a hub, a mast, and a vibration attenuation system comprising a mass suspended from the mast by an elastic system. The mass is connected to an electrical winding that interacts with a magnetic field generated by a permanent magnet, creating a Lorentz force that counteracts the vibrational forces. The system is designed to attenuate vibrations at multiple rotational speeds, including the first and second nominal speeds, while maintaining simplicity and cost-effectiveness.

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<title>Abstract</title> When the helicopter tail transmission shafting is over-critical, the shafting vibration intensifies, which restricts the overall performance of the helicopter. Smart spring support is an active damping device, which can effectively suppress the vibration of multi-span shafting. In this paper, the configuration and structure design of the smart spring support for multi-span shafting are studied, and its vibration-damping performance is verified by experiments. Firstly, based on the vibration reduction principle of the smart spring support, the vibration characteristics of the smart spring are analyzed. The motion equation of the smart spring support was established, the influence of configuration parameters on its vibration characteristics was analyzed, and the configuration parameters of the smart spring support were determined. On this basis, three configuration schemes of the smart spring support are proposed, the structural design of the smart spring support is carried out, and the structural parameters are determined. The shafting vibration reduction test ... Read More

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Vibration dampening is a term used in ergonomic, industrial, and electrical applications to minimize the system's kinetic energy. When vibration is attenuated, energy is delivered to the proper routes and noise propagation is diminished. The moment of the propeller and engine causes a drone to vibrate, with added complexity for drones because they are designed to have constant and carry fragile electronics. Investigating the uses of vibrational dampers and shock absorbers in UAVs utilizing several case studies based on material analysis, and different approaches. This report will assist us in reviewing previous research in this topic. In addition, the material properties of composite materials and shape memory alloys are being compared. Shape memory alloys have elastic characteristics and can restore their original shape.

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In order to reduce vibration from the source of the vibration of the helicopter and improve the efficiency of the damping of vibration, a propeller hub top mounted vibration damping actuator system and its position loop decoupling control strategy are proposed in this paper. By decoupling the position difference and average value of permanent magnet synchronous motors (PMSMs), high-precision servo control of the amplitude and phase of output force is achieved. The parameters of position loop are designed by small-signal modeling and root-locus stability analysis, and the effect of the vibration damping of the system is verified by simulation.

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Rotor for a hover-capable aircraft, comprising a hub with a plurality of blades, a mast, and a vibration attenuation system. The system includes a plurality of mass units, each comprising two masses connected by a belt and pulley system, which rotate about the mast axis. The masses generate centrifugal forces that counteract vibratory loads transmitted to the mast, thereby reducing transmission of vibrations to the fuselage.

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Vibration isolation system for concentric cylindrical structures, comprising at least three coaxially adjacent toroidal elements: an inwardly contiguous non-resilient element, an outwardly contiguous non-resilient element, and a noncontiguous resilient element. The resilient element is interposed between the non-resilient elements and attached to both, providing vibration isolation and damping along two axes while allowing axial movement.

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A real-time vibration monitoring system for unmanned aerial vehicles (UAVs) that detects and responds to abnormal vibration conditions. The system comprises vibration sensors installed at critical points on the UAV, a data acquisition module, a strategy determination module, and an operation execution module. The system continuously monitors vibration data, compares it against predefined thresholds, and implements protective actions based on the severity and location of the vibration anomalies.

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The main focus of this study revolves around the problem of vibrations in unmanned aerial vehicles and aims to propose solutions using different designs of vibration dampers. Specifically, the study identifies the sources of vibrations in a Single Rotor Rotary Wing (Monocopter) type UAV. To assess the damping performance of the designed dampers, vibration tests were conducted in a controlled setup. Based on the measurement results obtained at three different speed stages, a particular damper, referred to as G2S2, exhibited the highest damping performance. At the first speed stage, it achieved damping percentages of 66% for the X-axis, 77% for the Y-axis, and 84% for the Z-axis. At the second speed stage, the percentages increased to 81% for the X-axis, 84% for the Y-axis, and 97% for the Z-axis. Finally, at the third speed stage, the damper demonstrated damping percentages of 85% for the X-axis, 84% for the Y-axis, and 98% for the Z-axis. This study successfully developed an experimental setup for measuring vibrations during UAV flight, particularly focusing on unmanned aerial vehicl... Read More

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Abstract Dynamic antiresonance vibration isolation technology is widely used in the vibration reduction system of helicopters, because its simple structure and high vibration isolation efficiency. In this study, a dual-frequency vibration isolation system with two anti-resonant frequencies has been established, which can adapt to the vibration characteristics of two main vibration frequencies caused by the variable speed of the new high-speed helicopter. The theoretical equation and transmissibility of the dual-frequency vibration isolation system are derived, and the variation law of the weight and other relevant parameters on the vibration isolation performance is explored. The accuracy of the theoretical results is verified by model tests. According to the installation form of the helicopter reducer, the structure of the dual-frequency vibration isolation system is preliminarily optimized, which provides technical support for the design of the vibration isolator of the helicopter with variable speed.

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A vibration isolator that decouples axial and lateral structural modes to minimize vibration transmission between external structures. The isolator comprises an axial flexural support and a lateral elastomeric support, each independently tunable to control structural modes in their respective directions. The axial support provides stiffness and compliance parallel to the central axis, while the lateral support provides compliance relative to the central axis. This decoupled design enables independent optimization of axial and lateral structural modes, allowing for improved vibration isolation performance.

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An isolator assembly for mechanically-lowered sensors in aircraft that provides consistent damping of air-load oscillations. The assembly includes a structural pin that is driven into a vibration-isolating mount when the sensor is deployed, transferring compressive loads in multiple axes to the mount. This design eliminates the need for precise rigging and provides a reliable damping response to oscillating air loads.

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A crossbar system for isolating a sensor assembly from external vibrations in a vehicle-mounted payload system. The system comprises two crossbar assemblies, each with a structure interface, payload mount interface, isolator, and damper. The isolators partially decouple the structure and payload interfaces, while the dampers attenuate vibrations transmitted through the crossbars. The system enables precise sensor operation despite vehicle-induced vibrations and shocks.

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Vibration damping in rotorcraft structures can reduce failures and instabilities and improve the ride comfort for passengers. This paper introduces the novel idea of damping vibration using electric proprotors on eVTOL aircraft without compromising the rotors ability to provide thrust. Feeding back the beam tip angular rate to the motor voltage is shown to stabilize all transverse beam vibration modes. The experimental results show that the closed loop damping in the first mode is three times higher than open loop. The torque bandwidth of the electric motor exceeds 100 Hz so the damping performance on the first mode (5.6 Hz) is very good. Damping on the second mode, however, is not improved due to the 40 Hz bandwidth of the angular rate sensor. The rotor speed frequency response rolls off at 20 dB/dec, indicating smaller vibration induced rotor speed variations at high frequency. Experimental step response results match the frequency domain damping predictions and show only 0.8% rotor speed variation for a 3% initial tip displacement.

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A vibration isolation system for sensors in a vehicle, comprising a crossbar assembly with a structure interface, a payload mount interface, and an isolator. The isolator includes a wire rope assembly with longitudinal and circumferential wires that decouple the structure interface from the payload mount interface, reducing vibrations transmitted to the sensor. The crossbar assembly is designed to isolate the sensor from external vibrations while maintaining structural integrity.

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In order to solve the structural damage problem of the first generation of large multi-rotor manned drones, the present work has designed to study the structural vibration problems of multi-rotor drones. On a small multi-rotor drone, the laser vibration meter verified the reliability of acceleration sensor measurement of vibration and found that circular shape carbon fiber arms have strong damping abilities, with the strongest vibration in the Z-axis direction. To improve the design of the second generation of large multi-rotor manned drones, elliptical shape carbon fiber arms were employed instead of circular arms. Experiments showed that the main vibrations of the large multi-rotor manned drones arm are low-frequency vibrations below 200Hz, producing mainly torsional and bending modes, and the elliptical carbon fiber arms significantly reduce vibrations in the Z-axis direction. This study provides experimental data support for multi-rotor manned drones and further presents an improvement strategy for suppressing the vibrations of the multi-rotor manned drones.

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In order to effectively reduce the vibration of the helicopter rotor transmitted from the main reducer to the fuselage, a semi-active vibration isolation system (SAVIS) with a magnetorheological (MR) damper was proposed and effective control strategies were designed. Firstly, the structural scheme and working principle of helicopter main reducer SAVIS were proposed. Secondly, the mechanical properties of the MR damper were tested, and the dynamic model of the MR damper was established based on the hyperbolic tangent model. In addition, the model errors of MR damper were analyzed and quantified. Thirdly, according to the design requirements and parameters of a helicopter, the structural parameters of SAVIS were designed. Then, the virtual prototype of helicopter main reducer SAVIS was established by using 3D drawing software and ADAMS software, and the vibration characteristics of three directions were analyzed. Finally, two controllers of equivalent skyhook and continuous skyhook were designed. The numerical analysis results indicate that compared with passive vibration isolation and... Read More

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Abstract An experimental study was conducted to investigate the phenomenon of UAV attitude instability caused by large vibrations affecting singlerotor UAV airborne equipment. Appropriate measurement points were selected to collect vibration signals from the unmanned aerial platform during takeoff and flight of the drone. The timedomain response and power spectral density of the unmanned aerial platform were then obtained. Establish a dynamic model of the vibration reduction system for an unmanned aerial platform and design a twostage vibration reduction structure for the unmanned aerial platform. Through field flight tests of unmanned aerial vehicles, it has been demonstrated that the maximum time domain response of the platform after vibration reduction is 8.75 g (less than 50 g), and the maximum root mean square value of the power spectral density (PSD) is 1.82 g (less than 3 g). The designed secondary vibration reduction structure can serve as a reference for the design of vibration reduction in unmanned aerial vehicles.

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This article aims to popularize the methods for determining the vibratory damping ratio, to explain the various mathematical and physical theorems related to the establishment of literal expressions. Vibration damping is an essential parameter to reduce the dynamic responses of structures. The study aimed at its determination is necessary and essential for the safeguard of buildings and human lives during the earthquake. Among the main methods studied in this article, the free vibration attenuation method seems to be easy to implement but requires a state-of-the-art device to capture the responses. In addition to this device, the other methods require other equipment for the vibration of the system and the transformation of the responses in the frequency domain.

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A vibration isolation system for sensors in a vehicle-mounted payload system, comprising a crossbar assembly with a slip plate damper that constrains lateral motion while allowing longitudinal movement. The crossbar assembly connects the payload mount to a support structure, with the slip plate damper positioned around the crossbar to isolate the sensor assembly from external vibrations. The system enables precise sensor operation while minimizing the impact of vehicle accelerations and vibrations.

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A thrust link for connecting an engine to an aircraft that reduces engine noise transmission to the cabin. The link includes a load transferring member and a tuned absorber that is coupled to the load transferring member and tuned to absorb specific engine noise frequencies. The tuned absorber can be a single unit or multiple units with different tuning frequencies, and can be implemented using various damping mechanisms such as viscoelastic layers, viscous fluids, or movable damping members.

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A damping assembly for unmanned vehicles, particularly multi-copters, comprising a positioning structure supporting vibration-sensitive components, and a dual-damping system with deformable units that compress and extend simultaneously in response to forces, thereby reducing vibration transmission.

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A vibration isolation system for sensors in a vehicle, comprising a crossbar assembly with an elastomeric isolator that decouples the sensor from the vehicle structure, and a payload mount that connects the sensor to the crossbar assembly. The isolator is supported by the crossbar assembly and elastically deforms in response to relative movement between the crossbar segments, partially decoupling the sensor from the vehicle structure and damping vibrations.

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A helicopter vibration damping kit comprising a tubular body with a central internal rod and a pair of end masses, the tubular body being mounted between the helicopter fuselage and main rotor mast, and the end masses being connected to the fuselage and mast respectively, to provide inertial damping of rotor-induced vibrations.

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A sensor support structure attached to a multi-rotor aircraft that provides a vibration-dampened, unobstructed, and complete spherical field of view for capturing video, photos, or 3D data of environments. The structure consists of an open framework built around the aircraft body with sensors attached to hubs and tensioned elastic members connecting to the aircraft. The sensors face outward to avoid capturing the aircraft itself. The elastic members dampen vibrations and allow center of mass adjustment. The aircraft can fly with the rotors outside the sensors' field of view, providing a complete spherical perspective.

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Abstract The twin rotor damper (TRD) is a device which primarily utilizes centrifugal forces for active vibration control. In its basic form, the TRD consists of two eccentric control masses rotating about two parallel axes. In a preferred mode of operation, the continuous rotation mode (CRM), the control masses rotate in opposite directions with a constant and equal angular velocity. This rotational motion results in a harmonic control force. In previous research, it has been shown that, in the CRM, the TRD can effectively damp vibrations while requiring little to no power from its actuators. However, this holds only for lateral vibrations, vibration perpendicular to gravitational forces, ergo gravity has no influence on the motion of the control masses. In this paper, the influence of gravity on the CRM is investigated analytically for the first time. It is shown that the TRD requires substantially greater power in the CRM to periodically lift the control masses against gravity. Subsequently, the CRM is augmented with an auxiliary function in the form of a Fourier series. This func... Read More

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Inertia measurement module for unmanned aircraft with improved vibration damping and reduced size. The module comprises a housing assembly with a sensing assembly and vibration damper. The sensing assembly includes a first circuit board, a second circuit board, and a flexible signal line connecting them. An inertia sensor is fixed to the second circuit board, which is bonded to a weight block and a vibration damper. The vibration damper is integrated into the housing assembly, eliminating the need for external vibration attenuation cushions.

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Arm assembly for UAVs that allows adjusting the natural frequency of the vehicle during flight to prevent resonance. The arm assembly has an adjustable mechanism that can change the length of the arms. By moving this mechanism, the natural frequency of the UAV can be shifted away from the excitation frequency of the propellers. This prevents resonance when the propeller frequency is close to the natural frequency. The frequency adjustment is controlled based on the target propeller frequency.

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Vibration damping system for drones to reduce vibrations transmitted from the rotor blades to the drone body and connectors, which can improve reliability and reduce failure risk. The system uses sensors, processors, actuators, and mass dampers to actively cancel out drone vibrations. The sensor detects vibrations, the processor processes the signal, and the actuator applies force to the mass damper to generate opposite vibrations that partially cancel the drone vibrations. This reduces overall drone vibrations to lower stress on critical components and connections.

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Passively damped mechanical structures for aerospace applications that combine vibration damping and isolation in a single component. The structures feature viscoelastic material (VEM) embedded within a lattice structure or flexure mount, which is integrated into the mechanical components themselves, such as strut end fittings or support legs. This design enables adaptive tuning of damping characteristics during system assembly and testing, while also reducing weight compared to traditional passive damping solutions.

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A carrier platform with a suspension mechanism that actively dampens and passively attenuates vibrations in multiple degrees of freedom to protect vibration-sensitive loads. The suspension mechanism includes a set of linkage elements with vibration isolators that attenuate horizontal vibrations, a set of springs for vertical biasing, and an active damping device for translational motion damping. The isolators are mechanically tuned to attenuate high-frequency vibrations, and a passive isolator can be used to further attenuate small amplitude vibrations.

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Damping device for reducing vibration in hollow structural components, comprising a tube member disposed within the component and at least one damping element attached to the tube member. The damping element is configured to flex against the component's inner wall to dissipate energy and reduce bending due to modal characteristics excited by vibration. The device can be attached to the component via a retention ring, clamp, adhesive, brazing, or welding, and can be positioned to contact the component at three discrete locations or less.

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Flight safety system for drones that can balance loading and prevent crashes during flight. The system continuously detects in-flight unbalancing loading using sensors. When unbalancing is detected, the system compensates by individually controlling drone motors to balance the load. It can also proactively compensate for planned operations like cargo release or shooting by adjusting motor thrust. This prevents crashes caused by unbalancing forces. The system can also trigger a parachute deployment with horizontal thrust from an auxiliary motor to divert a drone with malfunctioning motors.

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Abstract: Vibration has always been a major disturbance for helicopter. Vibrations, thus, a threat to components of helicopter. The vibration created by a helicopter draws a great contribution to the reduction in life of the components. Reducing the vibration that creates from helicopter rotor blades, tail rotors is a one step closer to this crisis. Helicopter Vibration control is a topic of research into designing helicopter rotor blade which can be operated more efficiently. The major source of the vibration come from the rotor blade rotation. By trying to upgrade new design in the helicopter main rotor blades and tail rotors reduce the vibration and make the operation more efficient. This paper addresses simulation and analysis of vibration level of rotor blades. Keywords: drag, rotor, vibration, air foil, blade profile.

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A vibration damping member for acoustic devices, comprising a first member, a second member, and a third member connected in series, where the third member has a lower elastic modulus than the first and second members, and is positioned between them to absorb and dissipate vibrations.

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Tuned vibration absorber that reduces vibrations at two frequencies (e.g., at the Blade Pass Frequency (BPF) and at one harmonic frequency of the BPF) for propeller-driven aircraft. The absorber includes a beam arranged lengthwise in a longitudinal direction, the beam has an attachment mechanism adapted for mechanically coupling the first beam to a structure, a second beam is arranged lengthwise in a transverse direction, perpendicular to the longitudinal direction, the second beam is mechanically coupled to a first end of the first beam via a first connector, a third beam is arranged lengthwise in the transverse direction, and a third beam is mechanically coupled to a second end of the first beam, opposite the first end, via a second connector.

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View Video Presentation: https://doi.org/10.2514/6.2022-1042.vid Unmanned Aerial Vehicles (UAVs) have the ability to carry different payloads, and sensors. However, in the presence of any onboard component or attachment load, the UAV dynamics is changed, and its performance can be negatively impacted due to excessive vibrations. The mathematical model of the UAV with a vibrating payload attached to its body is here obtained and presented. The physical connection between the UAV and its payload is assumed to be elastic, and the SMA spring is used for its representation. This SMA spring has the ability to vary its stiffness and damping, by enabling to decrease the undesired vibration (mainly provoked by external disturbances) transmitted to the payload. Numerical simulations are presented, and their results show that this type of configuration considers an interesting strategy for vibration suppression during the flight.

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A helicopter tailrotor driveline is equipped with dampers to suppress the resonance of transmission shafts. A dry friction damper and a slender shaft form an assembly The comprehensive understanding of different responses of the assembly provides the basis for a more reasonable parameter configuration of the damper. To this end, the assembly is modeled as a dynamic system with rub impact between a rotor with continuous parameter distribution and a suspended elastic stator. Boundaries of rub impact and condition of Hopf bifurcation are derived. Pinned natural frequencies and backward whirl frequencies are solved by analytical deduction. The critical speed for triggering a backward whirl with consideration of eccentric excitation is obtained by the multiple scale perturbation method. Then, all-round responses and boundaries are solved by both analytical and numerical approaches based on the parameters of a helicopter. The effects of friction coefficient, internal damping, suspension stiffness, variable impact stiffness, etc. on the boundaries are presented in detail with the discussion... Read More

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