Foldable robots have been an active area of robotics research due to their high volume-to-mass ratio, easy packability, and shape adaptability. For locomotion, previously developed foldable robots have either embedded linear actuators in, or attached non-folding rotary motors to, their structure. Further, those actuators directly embedded in the structure of the folding medium all contributed to linear or folding motion, not to continuous rotary motion. On the macro-scale there has not yet been a folding continuous rotary actuator. This paper details the development and testing of the first macro-scale origami rotary motor that can be folded flat, and then unfurled to operate. Using corona discharge for torque production, the prototype motor achieved an expansion ratio of 2.5:1, reached a top speed of 1440 rpm when driven at -29 kV, and exhibited a maximum output torque over 0.15 mN m with an active component torque density of 0.04 Nm/kg.
Corrosion is one of the main causes of aircraft structural damage. The deepening of the corrosion depth will greatly endanger the safety of the crew. The Lamb wave array signal processing method can be used to estimate the direction of arrival (DOA) of the signal source. As a form of the Lamb wave array signal processing method, multiple-signal classification (MUSIC) has been gradually applied to the corrosion monitoring of aluminum plates. However, when MUSIC is used for Lamb wave DOA estimation, it has a low resolution and poor anti-interference ability. To improve it, the Lamb wave near-field source location (LWNFL) method is proposed in this paper. The new method adopts a double-sensor array arrangement. Firstly, the compressed sensing (CS) theory is combined with the Lamb wave near-field array model to obtain a DOA estimation of the corrosion. Here, the corrosion angle can be obtained using a CS reconstruction algorithm, and the noise interference can be suppressed by limiting a minimization of the l2 norm. Then, the corrosion distance is calculated according to the Lamb wave arrival time difference between different sensors. Finally, the average of the positioning results from multiple excitation sensors is used as the final location of the corrosion. The proposed LWNFL method is verified on an aluminum plate. The experimental results show that the new method can accurately obtain the location of corrosion and has good resolution and strong anti-interference ability.
Micro-vibration mitigation is critical for spacecraft conducting precision-oriented space missions. In this paper, a novel Stewart platform incorporating a phase-change low-melting-point alloy (LMPA) is developed to achieve temperature-dependent stiffness modulation and broadband vibration isolation. First, based on the theory that variable stiffness alters the natural frequency of the structure, the feasibility of using the Stewart platform to achieve vibration isolation by changing the stiffness is obtained. Subsequently, a new Stewart composite structure was engineered by integrating LMPA and composite materials. Finally, compression and vibration tests were carried out on these platforms at temperatures of 25 °C and 60 °C. The results show that these Stewart platform composite structures have the response characteristics of variable stiffness, a variable natural frequency and widened frequency at different temperatures. The response properties of the platform are attributed to the phase change of the low-melting-point alloy at different temperatures. The effective vibration isolation frequency range of the composite Stewart platform can be widened to 31.6 Hz, and the vibration attenuation can reach up to 10 dB. This investigation establishes a novel methodology for developing adaptive vibration isolation systems using phase-change alloys, which are particularly suitable for spacecraft applications requiring precision motion control.
The fault diagnosis of aero-engines is confronted with a data skew issue，where the number of fault sam ples is significantly fewer than normal samples，and the fault samples can't adequately represent the entire operating conditions，resulting in poor generalization ability of conventional classification models. To overcome this issue，an improved deep support vector data description-based time series anomaly detection model is proposed. The long short-term memory（LSTM）network is employed to map the inputs and outputs of samples，forming temporal anomaly vectors with actual collected outputs. The deep support vector data description（SVDD）incorporating variational auto-encoder（VAE）is utilized to achieve anomaly detection for aero-engine time series data. The experimental verification is performed with a certain type of aero-engine ground test platform，and the model is com pared to with isolation forest（IF），transformer-based anomaly detection（TranAD）model，and GANomaly. The results show that the curve value calculated with the proposed model can reach to 0.987 8，has superior anomaly detection performance. The proposed model can effectively be applied to various anomaly detection and fault diagnosis tasks in aero-engine systems.
The estimation of Above-Ground Biomass (AGB) in Amorphophallus konjac (Konjac) is essential for field management and yield prediction. While previous research has demonstrated the efficacy of Unmanned Aerial Vehicle (UAV) RGB imagery in estimating AGB for monoculture crops, the applicability of these methods to AGB estimation in Konjac remains uncertain due to its distinct morphological traits and prevalent intercropping practices with maize. Additionally, the Vegetation Indices (VIs) and Texture Features (TFs) obtained from UAV-based RGB imagery exhibit significant redundancy, raising concerns about whether the selected optimal variables can maintain estimation accuracy. Therefore, this study assessed the effectiveness of Variable Selection Using Random Forests (VSURF) and Principal Component Analysis (PCA) in variable selection and compared the performance of Stepwise Multiple Linear Regression (SMLR) with four Machine Learning (ML) regression techniques: Random Forest Regression (RFR), Extreme Gradient Boosting Regression (XGBR), Partial Least Squares Regression (PLSR), and Support Vector Regression (SVR), as well as Deep Learning (DL), in estimating the AGB of Konjac based on the selected features. The results indicate that the integration (PCA_(PCA_VIs+PCA_TFs)) of PCA-based VIs and PCA-based TFs using PCA achieved the best prediction accuracy (R<sup>2</sup> = 0.96, RMSE = 0.08 t/hm<sup>2</sup>, MAE = 0.06 t/hm<sup>2</sup>) with SVR. In contrast, the DL model derived from AlexNet, combined with RGB imagery, yielded moderate predictive accuracy (R<sup>2</sup> = 0.72, RMSE = 0.21 t/hm<sup>2</sup>, MAE = 0.17 t/hm<sup>2</sup>) compared with the optimal ML model. Our findings suggest that ML regression techniques, combined with appropriate variable-selected approaches, outperformed DL techniques in estimating the AGB of Konjac. This study not only provides new insights into AGB estimation in Konjac but also offers valuable guidance for estimating AGB in other crops, thereby advancing the application of UAV technology in crop biomass estimation.
Seham Helmi, Erik Benson, Jan Christoph Thiele
et al.
Synthetic molecular motors are an appealing means to control motion at the nanoscale, but understanding their behaviour as single-molecule actuators and integrating them into larger, functional systems remain technical challenges. Translating molecular actuation into coordinated device-level behaviour requires precise placement and orientation of the motors: DNA origami provides a powerful platform for positioning molecules with nanometre precision. Here, we demonstrate integration of a light-driven, rotary molecular motor into a DNA-based nanoscale actuator through site-specific, four-point conjugation. The motor is labelled with four distinct oligonucleotides, two on each side, using DNA-templated chemistry. This modular approach enables stable, oriented incorporation of the motor into a DNA assembly through DNA hybridization. Upon photoactivation with UV light, the motor transduces photon energy into rotary motion. By coupling the motor to a fluorescently labelled DNA rotor arm we amplify its movement and enable real-time observation using total internal reflection fluorescence microscopy. A subset of assembled devices exhibits light-induced conformational transitions and directional motion consistent with the expected photochemical mechanism. These results establish a programmable framework for integration of light-driven molecular motors into synthetic nanomachines and tools for the study of their behaviour.
When solving complex time-variant reliability analysis（TRA）problems，the traditional TRA methods have the problem of low solving efficiency. Based on the approximating most-probable-points trajectory （AMPPT）method，the efficient approximating the most-probable-point trajectory（EAMPPT）method for TRA is proposed. According to the characteristics that the reliability of weakest part of the system determines the reliability of the system，EAMPPT takes full account of prediction values and their errors in the process of approximating the most-probable-point trajectory. The mathematical example is used to verify the effectiveness of the adaptive sampling method. EAMPPT is applied to solve TRA problems involving hydrokinetic turbine blades and the wing of the reusable aerospace during reenter. The results show that the calculation accuracy of the proposed EAMPPT and time-discretization based TRA method is similar，but the number of performance function evaluations of EAMPPT is less than 3% of traditional TDTRA.
Enrique Rafael García-Sánchez, Héctor Simón Vargas-Martínez, Filiberto Candia-García
et al.
Life cycle stages are very important for the aerospace industry. Many models have emerged for handling the processes within and across the development of new products. Developing CubeSat-based missions has shortened the required time and has reduced expenses. However, the lack of strategic planning in the design, integration, and testing of product development models has been highlighted as one of the key issues contributing to failures. The objective of this study is to propose a new hybrid model for the physical development of a product using an Agile Stage-Gate methodology focused on a 1U CubeSat (AztechSat-1). This study aims to explain the full process throughout the project timeline from conceptualization to execution. The benefits of such a model include ensuring adaptive responses to not only improve technical integration but also allow the successful validation and verification of a nanosatellite. Our theoretical approach articulates an in-depth understanding of Agile Stage-Gate methodology through experience obtained from experts and team members. Our analysis supports the expected benefits of the iterative process at every stage. Through this approach, product development could benefit from reduced times and better innovations. Nevertheless, there are also drawbacks to this method. The requirements of greater human effort, more frequent demonstrations, and a constant review process have negative impacts. Additionally, particular modifications must be made for each area of research. For educational purposes, the initial results seem to be encouraging.
The biomimetic turbine has an excellent flow drag reduction ability and wide incidence adaptability, so it has the potential to achieve high efficiency within a wide working range of high-performance variable cycle engines. A biomimetic cascade that can broaden the effective working incidence angles was designed based on a high-loading low-pressure turbine cascade, and its flow mechanism and aerodynamic performance were studied using experimental and numerical methods under the incidences angle (i) of 0° to 15° and Reynolds number of 1.0 × 10<sup>5</sup>. A series of counter rotating vortex pairs induced by the biomimetic cascade bring additional dissipation losses, but it accelerates the energy exchange between the boundary layer and mainstream, enhancing the dissipation of the pressure side leg of horseshoe vortex, and thus suppressing the flow separation and passage vortices. The undulating surface of biomimetic cascades can suppress the expansion of secondary flow in a spanwise direction in the end region, especially for large-scale separation under high incidence conditions. When i < 5°, the loss of biomimetic cascades is slightly higher than that of the original cascades, but the increase is only 0.5%; when i > 5°, the losses of biomimetic cascades are significantly reduced, with a maximum reduction of 70% at i = 15°.
This paper proposes a new range equation for hybrid-electric aircraft. The paper revisits the theory of the range equation for a hybrid-electric aircraft with constant power split published earlier in the literature and proposes a new efficiency-based definition of the degree of hybridization (<i>φ</i>), one which includes the efficiencies of the electric or fuel-powered drivetrain. The paper shows that the efficiencies of the respective drivetrains play a significant role in the range estimation of the hybrid-electric aircraft. The paper makes use of a case study to show the relationship between battery energy density, powertrain efficiency and modification in the definition of the degree of hybridization <i>φ</i> with aircraft range. We show that for every aircraft design, there is a battery energy density threshold, for which the aircraft range becomes independent of the degree of hybridization. Below this threshold, the range decreases with an increase in the degree of hybridization. Conversely, beyond this threshold, the aircraft range increases with the degree of hybridization. Our study finds that the new definition of <i>φ</i> has shifted this threshold significantly upwards compared to earlier publications in the literature. This makes the design of an aircraft with a high degree of hybridization less optimistic.
In order to study the optimal sweepback angle when a variant unmanned aerial vehicle (UAV) exhibits a low radar cross-section (RCS) indicator during phase flight, an auto sweep scheme based on electromagnetic scattering evaluation and an improved particle swarm optimization algorithm was presented in this article. An aircraft model with variable swept wings was built, and high-precision grids were used to discretize the target surface. The results showed that the optimal sweep angle did not change with the increase in the initial azimuth angle when the observation field was horizontal and the ending azimuth was 90°. While the increase in the elevation angle affected the optimal sweepback angle of the aircraft under the given conditions, when the observation initial azimuth angle was 90°, the auto sweep scheme could reduce the mean and some minima of the RCS indicator curve of the aircraft and could provide the aircraft with an optimal sweep angle under different observation conditions. The presented method was effective in learning the optimal sweep angle of the aircraft when low scattering characteristics were required during the phase flight.
At present, there is no publicly published research on the unsteady interference effect in the start-up process of the lateral jet control of the spinning missile. The variation of aerodynamic characteristics during the jet start-up process of the spinning missile is still unclear. Therefore, the unsteady numerical method based on the three-dimensional unsteady compressible Navier–Stokes equations and the sliding mesh method is used to study the unsteady jet interference characteristics of the spinning missile during the starting process of the lateral jet. Based on the verification of the numerical simulation method in this paper, the jet interference flow field under the conditions of non-rotation and rotation is simulated, and the variation of the aerodynamic characteristics of the missile under the two conditions is given. The influence of rotation on the unsteady aerodynamic characteristics of the lateral-jet-controlled spinning missile is analyzed. The flow mechanism resulting in the change of the jet control characteristics and the lateral aerodynamic characteristics of the missile is analyzed through the interference flow field structure at different moments after the jet starts. The results indicate that in the start-up process of pulse jet control, the jet interference characteristics on the fins have a delay effect compared with the projectile body. The duration of the unsteady effect caused by the high-pressure region upstream of the nozzle is shorter than that caused by the low-pressure region downstream of the nozzle. The flow separation and reattachment near the nozzle have strong unsteady characteristics. The jet wake has the most obvious interference effect on Fin1. The pressure on the side of the rotation direction of Fin1 increases, while the opposite side is in contrast.
UAS-based commercial services such as urban parcel delivery are expected to grow in the upcoming years and may lead to a large volume of UAS operations in urban areas. These flights may pose safety risks to persons and property on the ground, which are referred to as third-party risks. Path-planning methods have been developed to generate a nominal flight path for each UAS flight that poses relative low third-party risks by passing over less risky areas, e.g., areas with low-density unsheltered populations. However, it is not clear if risk minimization per flight works well in a commercial UAS operation that involves a large number of annual flights in an urban area. Recently, it has been shown that when using shortest flight path planning, a UAS-based parcel delivery service in an urban area can lead to society-critical third-party risk levels. The aim of this paper is to evaluate the mitigating effect of state-of-the-art risk-aware path planning on these society-critical third-party risk levels. To accomplish this, a third-party risk simulation using the shortest paths is extended with a state-of-the-art risk-aware path-planning method, and the societal effects on third-party risk levels have been assessed and compared to those obtained using shortest paths. The results show that state-of-the-art risk-aware path planning can reduce the total number of fatalities in an area, but at the cost of a critical increase in safety risks for persons living in areas that are favored by a state-of-the-art risk-aware path-planning method.
The surface of Mars is bombarded by energetic charged particles of solar and cosmic origin with little shielding compared to Earth. As space agencies are planning for crewed missions to the red planet, a major concern is the impact of ionizing radiation on astronaut health. Keeping exposure below acceptable radiation dose levels is crucial for the health of the crew. In this study, our goal is to understand the radiation environment of Mars and describe the main strategies to be adopted to protect astronauts from the harmful impacts of cosmic radiation. Specifically, we investigate the shielding properties of various materials in the Martian radiation field using the Geant4 numerical model, after validating its accuracy with in-situ instrument measurements by MSL RAD. Our results indicate that composite materials such as types of plastic, rubber or synthetic fibers, have a similar response against cosmic rays and are the best shields. Martian regolith has an intermediate behavior and therefore could be used as an additional practical option. We show that the most widely used aluminum could be helpful when combined with other low atomic number materials.
The vehicle for the safety of traffic on the highways Turkey braking sys-tems, the use of tested and approved by the authorities of parts is a legal re-quirement. For this purpose, it is necessary to check whether the system is working properly with various tests. In our country, a periodic inspection of approximately one million heavy vehicles is carried out annually. Generally, heavy vehicles have air braking system. In the air brake system; In order to determine the amount of air leakage in the system, tests such as leak test, load adjustment valve (Alb) test, four-way safety valve test, check valve test, yellow and red coupling break test, which adjust the brake forces ac-cording to the load condition of the heavy vehicle, are performed. In this study, it is aimed to carry out “Leak Testing”, which is one of the air brake system tests of heavy vehicles, with computer support, increase the reliability of the test and minimize the time the operator spends for the test. For this purpose, a tester and test software have been developed. As a result of the study, instead of the current manual test, this test device and software devel-oped increased test reliability and saved 4 minutes of test time.
Kuang Liu, Alison E. Patteson, Edward J. Banigan
et al.
The cell nucleus houses the chromosomes, which are linked to a soft shell of lamin filaments. Experiments indicate that correlated chromosome dynamics and nuclear shape fluctuations arise from motor activity. To identify the physical mechanisms, we develop a model of an active, crosslinked Rouse chain bound to a polymeric shell. System-sized correlated motions occur but require both motor activity {\it and} crosslinks. Contractile motors, in particular, enhance chromosome dynamics by driving anomalous density fluctuations. Nuclear shape fluctuations depend on motor strength, crosslinking, and chromosome-lamina binding. Therefore, complex chromatin dynamics and nuclear shape emerge from a minimal, active chromosome-lamina system.
In this article, we apply the Free-Energy Principle to the question of motor primitives learning. An echo-state network is used to generate motor trajectories. We combine this network with a perception module and a controller that can influence its dynamics. This new compound network permits the autonomous learning of a repertoire of motor trajectories. To evaluate the repertoires built with our method, we exploit them in a handwriting task where primitives are chained to produce long-range sequences.