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This article studies synchronization control of a novel devised treadmill-based testing apparatus for wheeled planetary rover roaming at low speed. To offer satisfactory tracking performance and to ameliorate internal conflicts amongst individual treadmills during rover-treadmill interaction, a decentralized synchronization control strategy integrating an adaptive friction compensation scheme is proposed. To overcome the nonlinear friction effect at low-velocity scenarios, the LuGre model based friction compensation scheme is constructed with a dual-observer structure that can handle parametric uncertainties without recourse to the high-resolution encoder-required parameter identification. With the proposed control design, asymptotic stability of the closed-loop system is guaranteed with the tracking error and synchronization error converging to zero in presence of parametric uncertainties. Experimental results demonstrate the effectiveness of the proposed control strategy, which significantly improves the tracking performance in comparison with the existing proportional differential (PD)-type controller and synchronization controller without friction compensation.

Insulin-mTOR signaling drives anabolic growth during organismal development, while its late-life antagonistic pleiotropy affects aging and compromises lifespan across animal phylogeny. Here we identify LPD-3 as a megaprotein that orchestrates the tempo of insulin-mTOR signaling duringC. elegansaging. We find that an agonist insulin INS-7 is drastically over-produced and shortens lifespan inlpd-3mutants, aC. elegansmodel of human Alkuraya-Kučinskas syndrome. LPD-3 forms a bridge-like tunnel megaprotein to facilitate phospholipid trafficking to plasma membranes. Lipidomic profiling reveals increased abundance of hexaceramide species inlpd-3mutants, accompanied by up-regulation of hexaceramide biosynthetic enzymes, including HYL-1 (Homolog of Yeast Longevity). Reducing HYL-1 activity decreases INS-7 levels and rescues the shortened lifespan oflpd-3mutants through insulin receptor/DAF-2 and mTOR/LET-363. LPD-3 antagonizes SINH-1, a key mTORC2 component, and decreases expression with age in wild type animals. We propose that LPD-3 acts as a megaprotein brake for aging and its age-dependent decline restricts lifespan through the sphingolipid-hexaceramide and insulin-mTOR pathways.

Most insects and hummingbirds can generate lift during both upstroke and downstroke with a nearly horizontal flapping stroke plane, and perform precise hovering flight. Further, most birds can utilize tails and muscles in wings to actively control the flight performance, while insects control their flight with muscles based on wing root along with wing’s passive deformation. Based on the above flight principles of birds and insects, Flapping Wing Micro Air Vehicles (FWMAVs) are classified as either bird-inspired or insect-inspired FWMAVs. In this review, the research achievements on mechanisms of insect-inspired, hoverable FWMAVs over the last ten years (2011–2020) are provided. We also provide the definition, function, research status and development prospect of hoverable FWMAVs. Then discuss it from three aspects: bio-inspiration, motor-driving mechanisms and intelligent actuator-driving mechanisms. Following this, research groups involved in insect-inspired, hoverable FWMAV research and their major achievements are summarized and classified in tables. Problems, trends and challenges about the mechanism are compiled and presented. Finally, this paper presents conclusions about research on mechanical structure, and the future is discussed to enable further research interests.

In this paper, a multi-propeller aerial robot with a passive manipulator for aerial manipulation is presented. In order to deal with the collision, external disturbance, changing inertia, and underactuated characteristic during the aerial manipulation, an adaptive trajectory linearization control (ATLC) scheme is presented to stabilize the multi-propeller aerial robot during the whole process. The ATLC controller is developed based on trajectory linearization control (TLC) method and model reference adaptive control (MRAC) method. The stability of the proposed system is analyzed by common Lyapunov function. Numerical simulations are carried out to compare the ATLC with TLC controller facing collision, external disturbance and changing inertia during an aerial manipulation. Experimental results prove that the developed robot can achieve aerial manipulation in the outdoor environment.

Cells adapt to cold by increasing levels of unsaturated phospholipids and membrane fluidity through homeostatic mechanisms conserved in nearly all forms of life. As most eukaryotic enzymes for lipid synthesis and desaturation localize on endoplasmic reticulum (ER) membranes, it remains unknown how ER-resident lipids rapidly distribute to plasma membranes (PM). Here we report an exceptionally large and evolutionarily conserved protein LPD-3 in C. elegans that plays critical roles in lipid trafficking and cold resilience. We identified lpd-3 mutants in a mutagenesis screen for genetic suppressors of the lipid desaturase FAT-7, and found that the 452 kDa megaprotein LPD-3 bridges ER and PM, consisting of a structurally predicted hydrophobic tunnel for lipid trafficking. Loss of LPD-3 caused abnormal cellular distribution of phospholipids, diminished FAT-7 abundance, and organismic vulnerability to cold. These phenotypic defects of lpd-3 mutants were rescued by Lecithin comprising unsaturated phospholipids. Importantly, we found that deficient lpd-3 homologues in Zebrafish and mammalian cells led to defects similar to those observed in C. elegans. As mutations in KIAA1109/BLTP1, the human orthologue of lpd-3, cause Alkuraya-Kucinskas syndrome, we propose that the LPD-3 family proteins may serve as evolutionarily conserved “highway bridges” critical for ER-associated non-vesicular trafficking of lipids and resilience to cold stress in eukaryotic cells.

Resistance coefficient ( RC ) is an important measure when designing wheel-driving mechanisms and accurate dynamic models for real-time mobility control of wheeled mobile robots (WMRs). This measure is typically formulated as a constant that depends on the wheel load, wheel dimensions, and soil that the WMR is designed for. This article proposes a novel variable RC that responds to terrain deformation. This variable RC is then applied to controllers for WMRs that estimate driving torques and slip ratios on deformable terrain. Simple yet accurate models of RC are developed from both experimental results and theoretical analysis, and these models are then compared with other methods. The proposed RC models give more accurate and more computationally efficient estimations of driving torques and slip ratios for WMRs, with average estimation errors less than 6% and the shortest computation time in experiments. The two proposed estimators are then applied to the design of the tracking-control systems for a WMR running on deformable terrain. Experiments with simulated sandy terrain demonstrate that both proposed control systems are feasible, and the slip estimation effectively decreases velocity tracking errors from more than 20% to less than 10%.

The trace element zinc is essential for many aspects of physiology. The mitochondrion is a major Zn(2+) store, and excessive mitochondrial Zn(2+) is linked to neurodegeneration. How mitochondria maintain their Zn(2+) homeostasis is unknown. Here, we find that the SLC-30A9 transporter localizes on mitochondria and is required for export of Zn(2+) from mitochondria in both Caenorhabditis elegans and human cells. Loss of slc-30a9 leads to elevated Zn(2+) levels in mitochondria, a severely swollen mitochondrial matrix in many tissues, compromised mitochondrial metabolic function, reductive stress, and induction of the mitochondrial stress response. SLC-30A9 is also essential for organismal fertility and sperm activation in C. elegans, during which Zn(2+) exits from mitochondria and acts as an activation signal. In slc-30a9–deficient neurons, misshapen mitochondria show reduced distribution in axons and dendrites, providing a potential mechanism for the Birk–Landau–Perez cerebrorenal syndrome where an SLC30A9 mutation was found.

Significance Zinc plays important roles in numerous cellular processes. Deficiency or excess of Zn 2+ leads to many diseases. Zn 2+ concentration at various cellular compartments is regulated. Imbalance of Zn 2+ in mitochondria has been linked to neurodegeneration. However, little is known about how mitochondrial Zn 2+ is regulated. We find that SLC-30A9 is required for Zn 2+ export from mitochondria in both Caenorhabditis elegans and human cells. Loss of slc-30a9 leads to excessive Zn 2+ accumulation in mitochondria, severe mitochondrial swelling, compromised mitochondrial metabolic function, reductive stress, and induction of the mitochondrial stress response. SLC-30A9 is also essential for organismal fertility and sperm activation. In neurons, slc-30a9 mutations cause dramatically reduced mitochondria in neurites, providing a potential mechanism for the Birk–Landau–Perez cerebrorenal syndrome.

Hoverable Flapping Wing Micro Air Vehicle (FWMAV) is a new concept aircraft which imitates the flight mode of hummingbirds or insects. It has excellent mobility, flexibility, concealment, and can demonstrate hovering, forward flight and other maneuvers, which has attracted wide attention. In this research, a prototype of hoverable FWMAVs is designed and built for the research of control method, and the research on flight attitude estimation and attitude control algorithm are carried out. The hardware devices such as flight control board and remote control are designed and developed independently, also we devised the software control system to realize the communication between software and hardware, then the algorithm is verified on the experimental platform. The prototype of the aircraft weighs 27.24g, and can take off under the flapping frequency of 20Hz. On the experimental platform, relying on the hardware control circuit and software control algorithm, it can realize the attitude control of roll and pitch, and demonstrate hovering flight for two minutes.

The design of the anode flow field is critical for yielding better performance of micro direct methanol fuel cells (µDMFCs). In this work, the effect of different flow fields on cell performance was investigated by the simulation method. Compared with grid, parallel and double-serpentine flow fields, a single-serpentine flow field can better improve the mass transfer efficiency of methanol and the emission efficiency of the carbon dioxide by-product. The opening ratio and channel length also have important effects on the cell performance. The cells were manufactured using silicon-based micro-electro-mechanical system (MEMS) technologies and tested to verify the simulation results. The experimental results show that the single-serpentine flow field represents a higher peak power density (16.83 mWcm−2) than other flow fields. Moreover, the results show that an open ratio of 47.3% and a channel length of 63.5 mm are the optimal parameters for the single-serpentine flow field.

Although the hybrid power system that combines a photovoltaic cell and a lithium-ion battery is increasingly mature and practical, long-lifetime auxiliary power will be still needed in severe weather conditions. A small-volume hydrogen–oxygen fuel cell system based on the hydrolysis of NaBH4 is designed. The fuel cell system contains a tiny hydrogen generator, a hydrogen cleaner, and a small fuel cell stack consisting of three units in series. The relationship between the amount of catalyst and output performance is discussed. The long-time discharging results indicate that the fuel cell system has high power capacity. The compact design allows the fuel cell system to integrate the structure with a photovoltaic cell and lithium-ion cell and forms a hybrid power system with a small package. The power management circuit for these power sources without logic devices is designed and tested. The control strategy selects the photovoltaic–battery subsystem as the primary power source, and the fuel cell subsystem works as the backup power source to handle the circumstance when the energy stored in the battery is exhausted. The test results show that the power management system could switch the power supply automatically and timely under various emergency conditions, and the output voltage remains stable all the time.

Allomyrina dichotoma has a natural ultra-high flying ability and maneuverability. Especially its ability to fly flexibly in the air, makes it more adaptable to the harsh ecological environment. In this study, a bionic flapping-wing micro air vehicle (FMAV) is designed and fabricated by mimicking the flight mode of A. dichotoma. Parametric design was employed for combining the airframe structure and flight characteristics analysis. To improve the transmission efficiency and compactness of the FMAV mechanisms, this study first analyses the body structure of A. dichotoma, and then proposes a novel mechanism of FMAV based on its biological motion characteristics, the flight motion characteristics, and its musculoskeletal system. By optimizing the flapping-wing mechanism and mimicking the flying mechanism of A. dichotoma, the large angle amplitude and the high-frequency flapping motion can be achieved to generate more aerodynamic force. Meanwhile, to improve the bionic effect and the wing performance of FMAV, the flexible deformation of A. dichotoma wings for each flapping period was observed by a high-speed camera. Furthermore, the bionic design of wings the prototype was carried out, therefore the wings can generate a high lift force in the flapping process. The experiment demonstrated that the aircraft can achieve a flapping angle of 160 degrees and 30 Hz flapping frequency. The attitude change of FMAV is realized by mimicking the movement for the change of attitude of the A. dichotoma, by changing the angle of attack of the wing, and executing the flight action of multiple degrees of freedom including pitch, roll and yaw. Finally, the aerodynamic experiment demonstrated that the prototype can offer 27.8 g lift and enough torque for altitude adjustment.

Endoplasmic reticulum (ER) morphology is dynamic and key to its function during different cellular processes. Dong et al. now show in convergent studies in human cells and Caenorhabditis elegans neurons that a phosphoinositide phosphatase (INPP5K) is localized on the surface of the ER network and helps control the shape of the ER., INPP5K (SKIP) is an inositol 5-phosphatase that localizes in part to the endoplasmic reticulum (ER). We show that recruitment of INPP5K to the ER is mediated by ARL6IP1, which shares features of ER-shaping proteins. Like ARL6IP1, INPP5K is preferentially localized in ER tubules and enriched, relative to other ER resident proteins (Sec61β, VAPB, and Sac1), in newly formed tubules that grow along microtubule tracks. Depletion of either INPP5K or ARL6IP1 results in the increase of ER sheets. In a convergent but independent study, a screen for mutations affecting the distribution of the ER network in dendrites of the PVD neurons of Caenorhabditis elegans led to the isolation of mutants in CIL-1, which encodes the INPP5K worm orthologue. The mutant phenotype was rescued by expression of wild type, but not of catalytically inactive CIL-1. Our results reveal an unexpected role of an ER localized polyphosphoinositide phosphatase in the fine control of ER network organization.

Rigid origami provides great theoretical potentials for designing metamaterials with programmable mechanical properties. In this paper, a novel family of cellular mechanical metamaterials is developed based on rigid-foldable square-twist origami. Kinematics and rigid-foldability of the four types of square-twist origami patterns are investigated. A square-twist origami, which has specific kinematic characteristics, is selected to construct novel metamaterial cells in the x-y plane. During deployment, the tunable Poisson's ratios of proposed metamaterial cells are guaranteed by their rigid-foldability and no self-intersection. Two combination schemes, literally linear and plane-symmetrical combination, are proposed to stack the metamaterial cells in the z-direction for building cellular metamaterials. Influences of geometries, number of layers, assemble mode, and combination scheme on the in-plane and out-plane Poisson's ratios of the square-twist origami are then evaluated. The Poisson's ratios of the constructed mechanical metamaterials are further analyzed. Following the mapping relationship between design factors and Poisson's ratio, cellular mechanical metamaterials with tunable Poisson's ratios could be designed for engineering applications.

The interest in flapping-wing Micro Air Vehicles (MAVs) has been rising progressively in the past years, as they can combine high agility manoeuvres with precision hovering flight and can be applied in complex spaces for reconnaissance missions. In this study, we propose a double flapping-wing MAV, which has four wings comprised by two pairs, each pair is driven by one brush motor and one linear servo. The flapping mechanism is composed of a crank-rocker and double rocker mechanism, which can amplify the output angle of wings and used for lift increasing. We take the Rhinoceros beetle as a bionic object and the Weis-Fogh mechanism as the high lift generation principle. The vehicle can actively control 4 degrees of freedom (DOFs), namely, roll, pitch, yaw, and thrust. Compare to the single pair counterpart, our vehicle possess a high thrust-to-weight ratio, which make it possible for more onboard load and beneficial to attitude control, additionally, the 3 rotational DOFs (roll, pitch, and yaw) is completely uncoupled and controlled independently, which is useful for control system design. The currently vehicle weighting 32.8 g (without the battery) and can generate 0.34N thrust at the maximum flapping frequency of approximately 23 Hz.

In view of the shortcomings of the previous mechanism design for the flapping wing micro air vehicle(FMAV),such as small flapping angle and low transmission efficiency, a new type mechanism of FMAV is designed in this paper. Large aerodynamic force is generated by the large amplitude flapping angle and high frequency flapping. By combining the new control mechanism, the maneuverability of the aircraft and the load demand during the mission are improved. Meanwhile, this new type mechanism meets the design requirements of the miniaturization and flexibility, and provide the theoretical basis and application value for the mission of the aircraft to carry out the border patrol, the disaster rescue and the reconnaissance missions.

With the development of low-power technology in electronic devices, the wireless sensor network shows great potential in applications in health tracing and ocean monitoring. These scenarios usually contain abundant low-frequency vibration energy, which can be collected through appropriate energy conversion architecture, thus, the common issue of limited battery life in wireless sensor devices could be solved. Traditional energy-converting structures such as the cantilever-beam type or spring-mass type have the problem of high working frequency. In this work, an eccentric pendulum-based electromagnetic vibration energy harvester is designed, analyzed, and verified with the finite element analysis method. The pendulum that contains alternative distributed magnets in the outer side works as a rotor and has the advantages of a simple structure and low center frequency. The structure size is well scalable, and the optimal output performance can be obtained by optimizing the coil thickness and width for a given diameter of the energy harvester. The simulation results show that the energy harvester could work in ultra-low frequencies of 0.2&ndash, 3.0 Hz. A full-scale prototype of the energy harvester is manufactured and tested. The center working frequency is 2.0 Hz with an average output power of 8.37 mW, which has potential for application in driving low-power wireless sensor nodes.

With the development of gas sensor technology, higher requirements are put forward for element sensitivity and controllable gas adsorption strength. Here, the adjustment effect of uniaxial or biaxial strains on 1T’ WS2 is discussed to achieve the controllable adsorption performance of NO2. Results suggested that the adsorption strength can be controlled by the applied tensile strain when the strain was between 1% and 10%, and it increases with the increase of strain. The biaxial strain was more conducive to generate the orbital mixing between NO2 and 1T’ WS2. The mechanism of strain affecting gas adsorption strength is clarified.

Superior gas capture and detection performance play an important role in gas sensing materials. Effects of atomic vacancy defects on intrinsic properties of material are also not negligible. Here we firstly discuss gas adsorption behavior of defective 1T’ WS2 monolayer. We take toxic NO2 gas as an example to compare adsorption effects between defective and perfect 1T'WS2 monolayer. First-principles study based on density functional theory(DFT) is carried out to act as the theoretical basis. These results demonstrate vacancy defects could enhance adsorption stability of 1T’ WS2 monolayer, which provide lower adsorption energy, more charge transfer and more overlaps of density of states. Therefore, vacancy defects make 1T’ WS2 monolayer possess more outstanding surface activity and adsorption performance. This can also offer theoretical support for the improvement of nanomaterials applied in those high performance gas sensing devices.

This paper designs a specific planar mechanism with variable topology (MVT) for automated fiber placement which has ability to change its topological structure for accomplishing the clamping, cutting and restarting motion. Firstly, the functional requirements and moving sequence are proposed to build the foundation of design, and a MVT is developed to fill the demand. Then, the topological structures and the mobility of this mechanism in different states are analyzed to prove that the mechanism manipulates in accordance with moving sequence through transformation. Thirdly, kinematics model is established with vector equation and the corresponding simulation is carried out. Results from simulation demonstrate that the proposed mechanism can effectively realize a stable operation.

Leg of robots predominantly adopts two types of configurations, insect-like configuration and mammal-like configuration. This paper presents a metamorphic quadruped robot whose leg possesses 4 degrees of freedom and can transfer to insect-like configuration and mammal-like configuration. The robot has 4 types of configurations, insect-like, reptile-like, mammal-like I and mammal-like II configurations. It skillfully combines two types of traditional configurations by well-founded mechanical structure design. Furthermore, gait transformation strategy between these four configurations on the basis of minimum torque and maximum stability was studied. And the workspace of the leg under different configurations is analyzed. The metamorphic quadruped robot possesses the advantage of controllably choosing optimal configuration to walk according to different terrain environment and mission requirement.

This paper aims to provide a novel substrate for the fabrication of micro passive direct methanol fuel cells. Aluminum alloy treated by plasma electrolytic oxidation (PEO) is electrically non-conductive and corrosion resistant, and thus it can act as the substrate materials of fuel cells. For this application, the corrosion problem of PEO coating in DMFC electrolytic environment that mainly contains H+ and F− must be seriously handled for that the corrosive products can poison catalyst and decrease proton conductivity. In this paper, PEO coating was prepared on aluminum alloy LY12 by an AC power supply in sodium silicate, and its corrosion resistance in the simulated DMFC environment was evaluated by potentiodynamic scan and EIS. The results indicate that the PEO coating shows excellent corrosion resistance in the simulated DMFC environment.

A novel MEA (membrane electrode assembly) structure of passive μ-DMFC (micro-direct methanol fuel cell) controls water management and decreases methanol crossover. The CNT (carbon nanotube) paper replacing CP (carbon paper) as GDL (gas diffusion paper) enhances water back diffusion which passively prevents flooding in the cathode and promotes low methanol crossover. Moreover, the unique structure of CNT paper can also enhance efficiency of oxygen mass transport and catalyst utilization. The passive μ-DMFC with CNT-MEA exhibits significantly higher performance than passive μ-DMFC with CP-MEA and can operate in high methanol concentration, showing the peak power density of 23.2 mW cm −2 . The energy efficiency and fuel utilization efficiency are obviously improved from 11.54% to 22.7% and 36.61%–49.34%, respectively, and the water transport coefficient is 0.47 which is lower than previously reported passive μ-DMFC with CP.

In this paper, a μDMFC (micro direct methanol fuel cell) with high performance was fabricated by adopting aluminum alloys as a substrate for the first time. PEO (plasma electrolytic oxidation) was adopted to prepare an oxide coating on the substrate to make it electrically non-conductive and corrosion resistant. The PEO-treated substrate shows excellent corrosion resistance in the simulated DMFC environment. Based on the substrate, a μDMFC was fabricated by using stainless steel fiber felt as a cathode current collector that was supported by a perforate flow field on the end plate to reduce the contact resistance. The results show that the cell can provide a peak power density as high as 40.90 mW cm −2 at room temperature of ca. 298 K. The research work presented in this paper provides another way for the design and fabrication of μDMFC.

Different anode flow fields of air-breathing micro direct methanol fuel cells (@mDMFCs) are investigated to improve the cell performances. The single-serpentine flow field can effectively improve the methanol mass transport efficiency and exhibit higher exhaust resultant (CO"2) rates than other flow fields such as gird, parallel and double-serpentine. Additionally, the effects of open ratios and channel lengths on the cell performance are evaluated to determine the optimal anode flow field structures. The @mDMFCs with different anode flow fields are fabricated using silicon-based micro-electro-mechanical systems (MEMS) technologies and are tested at room temperature. The experimental results show that the single-serpentine flow field exhibits a significantly higher performance than those of other flow fields, demonstrating 16.83mWcm^-^2 in peak power density and a substantial increase in mass transport coefficients. Moreover, for optimum single-serpentine flow field, it is appropriate for the flow channel dimensions to be in the ratio of 2:3:254 for channel width: ridge width: channel length.