Motion Mechanism Research Articles

A hybrid energy harvester with dual-frequency-up-conversion mechanism for ultra-low frequency rotational motion under 1.5 Hz

This paper proposes a hybrid energy harvester (HEH) based on dual-frequency-up-conversion mechanism, which is suitable for ultra-low frequency rotation. This mechanism takes full advantage of the periodic excitation provided by gravity to achieve two harvesting responses in one cycle. HEH consists of the piezoelectric energy harvester (PEH) and electromagnetic energy harvester. The magnet component achieves frequency up-conversion of PEH by impact, and also induces electrical energy from the coil, thus coupling two parts together to form continuous energy harvesting. The electromechanical coupling model of HEH is established, and the characteristics are in-depth analyzed via experiments and simulations. PEH can attain a bandwidth of 1.4 Hz with an open-circuit output voltage above 5.6 V, which indicates the frequency up-conversion helps the piezoelectric cantilevers to break through the resonance limit and obtain the higher output. HEH can combine the advantages of two energy harvesting parts, obtaining the maximum power of 6.598 mW under 1.5 Hz. The results show that the dual-frequency-up-conversion mechanism greatly improves the efficiency of energy conversion and HEH has the ability to power low-power sensors at ultra-low frequencies.

Simple Electroosmotic Pump and Active Microfluidics with Asymmetrically Coated Microelectrodes

Electroosmotic pumps can deliver liquid without moving parts, making them suitable for microfluidic and lab‐on‐chip systems. Previously, alternating current electroosmotic pumps were constructed using pairs of coplanar asymmetrical interdigitated microelectrodes on the same substrate. In this work, a simpler micropumping system is developed, separating the electrodes on two substrates and breaking the symmetry by half‐depositing electrodes with 3D microstructures. Numerical simulation models of the pumping system and experimental velocity profiles are used to explain the fluid motion mechanism and structure‐dependent pumping performance. In addition to its efficiency and simplicity, this new pumping system also allows for the creation of a microvortex device and an active microfluidics device. This scalable micropumping system provides a way to pump liquids at microscopic or macroscopical scale in complex microfluidics systems.

Mechanism analysis of internal solitary waves breaking encountering submarine ridges based on laboratory experiments

Internal solitary waves are commonly present in global oceans, and these waves encounter submarine ridges during their propagation, resulting in breaking. In this study, a two-layer fluid model and the gravity collapsing method were used to simulate the breaking process of internal solitary waves encountering submarine ridges in the laboratory, and particle image velocimetry was used to monitor the flow field. Based on the different roles of motion mechanisms in the wave-breaking process, the breaking types were classified. Moreover, the relationship between the topography, the initial parameters of internal solitary waves, and the breaking types was studied, and the movement parameters during the wave-breaking process were analyzed. The experiments showed that the Iribarren number and Bisw parameter proposed based on the gentle slope breaking process could not effectively classify the breaking types when internal solitary waves encountered submarine ridges because the permeability of the submarine ridges was different from that of gentle slopes, which significantly affected the motion mechanism during the breaking process. The movement parameter γ clearly reflected the roles of different motion mechanisms during the wave-breaking process. Another parameter δ established the relationship between the motion mechanisms and the topography and initial wave parameters.

Modeling the Pedestrian Flow Before Bottleneck Through Learning-Based Method

This paper proposes a learning-based approach for modeling microscopic pedestrian movement behavior before bottleneck which contains two sub models – velocity direction model and velocity magnitude model. Datasets extracted from fifteen controlled experiments were trained through CART algorithm in this approach. Fifteen original scenarios are adopted to evaluate the performance of the proposed approach from both macroscopic and microscopic aspects. Simulation results show that the trajectories and density, velocity, flow <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vs</i> . time curves and fundamental diagrams are basically consistent with those from corresponding experiments. Four evaluation metrics, final displacement error ( FDE), duration error ( DE), mean trajectory error ( MTE) and relative distance error ( RDE) are applied to quantitatively verify the precision of simulation. The mean of FDE, DE, and MTE are calculated to be 0.144 m, 0.112 s and 0.095 m respectively. With time intervals of 0.5 s, 1 s and 2 s, the mean RDE of all scenarios are respectively 0.7089, 0.4073 and 0.2515. Data from additional experiments of bottleneck scenarios and publicly available data of corridor scenarios are also introduced to prove the potential of general application of this approach. Comparisons and analysis indicate that the proposed approach has a good capability and reliability in simulating the pedestrian motion before the bottleneck. The models presented will be useful for passenger flow management and architectural design, also beneficial to understand the pedestrian movement mechanism in collective motion.

Design, Control, and Experiments of A Novel Robotic Uterine Manipulator with the Motorized 3-DoF Manipulation Rod.

To address the issue of declining performance over time with manual uterine manipulation during minimally invasive gynecologic surgery, we propose a novel uterine manipulation robot that offers tireless, stable, and safer manipulation. This proposed robot consists of a 3-DoF remote center of motion (RCM) mechanism and a 3-DoF manipulation rod. The RCM mechanism uses a single-motor bilinear-guided design that allows for a wide range of pitch motion (-50 to 34 degrees) while maintaining a compact structure. The manipulation rod has a tip diameter of only 6 mm, allowing it to accommodate almost any patient's cervix. The 30-degree distal pitch motion and ± 45-degree distal roll motion of the instrument further improve uterine visualization. The tip of the rod can be opened into a T-shape to minimize damage to the uterus. Laboratory tests have revealed that our device has a highly precise mechanical RCM accuracy of 0.373mm and is capable of handling a maximum load of 500g. Furthermore, through clinical testing, the robot has been proven to offer improved manipulation and visualization of the uterus, making it a valuable addition to the surgical tools available to gynecologists.

Synthesis on cardioid crank rocker mechanism with approximate uniform motion

The cardioid crank is a planetary mechanism that generates a cardioid line. It is a crank with varying length and speed that moves along the cardioid line. The cardioid crank is used to replace the crank of the crank rocker mechanism, and its rocker mechanism with approximate uniform motion is obtained. The kinematic analysis method of the cardioid crank rocker mechanism is studied in this paper. The calculating method for the limit position and oscillating angle and the time ratio of the guide bar are given. Finally, the approximate uniform motion conditions of the rocker are obtained. The synthesis method of the approximate uniform motion mechanism is put forward in accordance with the time ratio or rocker oscillate angle, the minimum length of the guide bar is calculated, and the influence of center distance on the kinematic performance of the mechanism is discussed.

Inspired by the Black Ghost Knifefish: Bionic Design of Undulatory Fin with 2-DOF Rays and Its Propulsion Performance

The demand for high-performance underwater thrusters in marine engineering is increasing. The concealed, mobile, and efficient underwater ability of fish provides many directions for research. The black ghost knifefish uses only wavy ventral fins to swim and can hover and roll in the water. Based on the physiological and morphological characteristics of the black ghost knifefish, we explored the structure and movement mode of the ventral fin, so as to establish a two-degree of freedom (2-DOF) structural model and kinematic model. We reveal the motion mechanism of the undulating fin propulsion through the constructed model and computational fluid dynamics. It is found that when the fin surface fluctuates, a pair of vortices with opposite directions will be formed on the concave side of the fin surface. These vortices will produce a central jet on the fin surface, provide a reverse impulse for the ventral fin, and make the fin obtain power. In addition, we found that the propulsive force of the ribbon fin along the body direction is positively correlated with the swing amplitude and frequency of the fin movement, and the propulsive torque of the ribbon fin to realize the maneuvering movement increases first and then decreases with the increase of the torsion angle. The research on the structure and motion mechanism of the ribbon fin of the black ghost knifefish provides a basis for the development of a bionic prototype of multi-DOF motion and the control strategy of high-mobility motion.

Leidenfrost droplet jet engine by bubble ejection

HypothesisDespite the flourishing studies of Leidenfrost droplet motion in its boiling regime, the droplet motion across different boiling regimes has rarely been focused on, where bubbles are generated at the solid–liquid interface. These bubbles are probable to dramatically alter the dynamics of Leidenfrost droplets, creating some intriguing phenomena of droplet motion. ExperimentsHydrophilic, hydrophobic, and superhydrophobic substrates with a temperature gradient are designed, and Leidenfrost droplets with diverse fluid types, volumes, and velocities travel from the hot end to the cold end of the substrate. The behaviors of droplet motion across different boiling regimes are recorded and depicted in a phase diagram. FindingsA special phenomenon of Leidenfrost droplets that resembles a jet engine is witnessed on a hydrophilic substrate with a temperature gradient: the droplet traveling across boiling regimes repulsing itself backward. The mechanism of repulsive motion is the reverse thrust from fierce bubble ejection when droplets meet nucleate boiling regime, which cannot take place on hydrophobic and superhydrophobic substrates. We further demonstrate that conflicting droplet motions can occur in similar conditions, and a model is developed to predict the occurring criteria of this phenomenon for droplets in diverse working conditions, which agrees well with the experimental data.

Design, Dimensional Synthesis and Evaluation of a Novel Two-Degrees-of-Freedom Spherical Remote Center of Motion Mechanism for Minimally Invasive Surgery

Abstract With the development of minimally invasive surgery (MIS) technology, higher requirements are put forward for the performance of remote center of motion (RCM) manipulator. This paper presents the conceptual design of a novel two-degrees-of-freedom (2-DOF) spherical RCM mechanism, whose axes of all revote joints share the same RCM. Compared with the existing design, the proposed mechanism indicates a compact design and high structure stability, and the same scissor-like linkage makes it easy to realize modular design. It also has the advantages of singularity-free and motion decoupling in its workspace, which simplifies the implementation and control of the manipulator. In addition, compared with the traditional spherical scissor linkage mechanism, the proposed mechanism adds a rotation constraint on the output shaft to provide better operating performance. In this paper, the kinematics and singularities of different cases are deduced and compared, and the kinematic model of the best case is established. According to the workspace and constraints in MIS, the optimal structural parameters of the mechanism are determined by dimensional synthesis with the goal of optimal global operation performance. Furthermore, a prototype is assembled to verify the performance of the proposed mechanism. The experimental results show that the two-degrees-of-freedom prototype can provide a reliable RCM point. The compact design makes the manipulator have potential application prospects in MIS.

Design and test of a pneumatic type of high-speed maize precision seed metering device

This study proposed a pneumatic type of high-speed maize precision seed metering device and analysed the motion mechanism of maize seeds during the filling, cleaning, and seed dropping processes of the device. Single-factor test methods were used to explore the influence of forward velocity, negative pressure of the seed metering device, and positive pressure of the seed guide tube on seeding performance separately. Additionally, based on high-speed camera technology, trajectory analysis was performed on continuously dropping maize seeds under different positive pressures of the seed guide tube. Results showed that an increase in positive pressure of the seed guide tube shortened the seed dropping time of maize seeds and made the time interval between adjacent maize seeds leaving the seed guide tube more uniform. Furthermore, a three-factor five-level orthogonal rotation combination test was used to explore the optimal working parameters of the pneumatic type of high-speed maize precision seed metering device. The results indicated that the optimal parameters were a forward velocity of 10 km/h, negative pressure of the seed metering device of 4.5 kPa, and positive pressure of the seed guide tube of 3 kPa. Verification tests demonstrated that the qualified index was 98.31% and the coefficient variation was 9.26%.

Comparison of Dynamic Knee Contact Mechanics with T2 Imaging in Different Ages of Healthy Participants.

Aging is a known risk factor for Osteoarthritis (OA), however, relations between cartilage composition and aging remain largely unknown in understanding human OA. T2 imaging provides an approach to assess cartilage composition. Whether these T2 relaxation times in the joint contact region change with time during gait remain unexplored. The study purpose was to demonstrate a methodology for linking dynamic joint contact mechanics to cartilage composition as measured by T2 relaxometry. T2 relaxation times for unloaded cartilage were measured in a 3T General Electric magnetic resonance (MR) scanner in this preliminary study. High-speed biplanar video-radiography (HSBV) was captured for five 20-30-year-old and five 50-60-year-old participants with asymptomatic knees. By mapping the T2 cartilages to the dynamic contact regions, T2 values were averaged over the contact area at each measurement within the gait cycle. T2 values demonstrated a functional relationship across the gait cycle. There were no statistically significant differences between 20- and 30-year-old and 50-60-year-old participant T2 values at first force peak of the gait cycle in the medial femur (p = 1.00, U = 12) or in the medial tibia (p = 0.31, U = 7). In the medial and lateral femur in swing phase, the joint moved from a region of high T2 values at 75% of gait to a minimum at 85-95% of swing. The lateral femur and tibia demonstrated similar patterns to the medial compartments but were less pronounced. This research advances understanding of the linkage between cartilage contact and cartilage composition. The change from a high T2 value at ~ 75% of gait to a lower value near the initiation of terminal swing (90% gait) indicates that there are changes to T2 averages corresponding to changes in the contact region across the gait cycle. No differences were found between age groups for healthy participants. These preliminary findings provide interesting insights into the cartilage composition corresponding to dynamic cyclic motion and inform mechanisms of osteoarthritis.

Experimental study of a universal high-speed ac collector motor

AC collector motors with power from tens to hundreds of watts are widely used in electric drives of flexible production systems, industrial robots, automation systems and vehicles. The most common is the use of universal alternating current collector electric motors. They are called universal because they can work from both an alternating current and a direct current network. They have the ability to smoothly change the speed of rotation of the drive - its shaft, which sets the executive mechanism in motion. An actual direction is conducting experimental studies of universal alternating current collector motors, which are used as a drive for hand-held power tools. This is done through the use of a specially developed experimental stand that takes into account the peculiarities of the operation of such electric motors. The purpose of the work is an experimental study of a universal AC collector motor to evaluate its parameters and characteristics. To evaluate the parameters and characteristics of such a motor for the drive of a hand-held electric tool, an experimental stand was developed, which takes into account the high speed of rotation of the output shaft of the device and allows smoothly changing the load to obtain operating characteristics. The hand-held electric tool of the world-famous manufacturer Makita, model GA5030, is used as the research object. Structurally, the drive motor is a collector machine of variable voltage with series excitation. The speed of rotation of such motors is regulated by changing the power supply voltage supplied to the motor. The structure of the experimental stand for the study of high-speed universal collector machines was developed, all components were selected and the stand was correctly assembled, according to the developed basic electrical and assembly diagram. Using the developed stand, the operating characteristics of the engine under study P1, Ia, η, cosϕ, n, M= f(P2) were recorded. The engine under study meets the stated characteristics. The value of the nominal efficiency is within 36% with a rather large value of the power factor cosϕ≈0.98.

Analytical model of optical force on supercavitating plasmonic nanoparticles.

Optical manipulation of nanoparticles (NPs) in liquid has garnered increasing interest for various applications, ranging from biological systems to nanofabrication. A plane wave as an optical source has recently been shown to be capable of pushing or pulling an NP when the NP is encapsulated by a nanobubble (NB) in water. However, the lack of an accurate model to describe the optical force on NP-in-NB systems hinders a comprehensive understanding of NP motion mechanisms. In this study, we present an analytical model using vector spherical harmonics to accurately capture the optical force and the resultant trajectory of an NP in an NB. We test the developed model using a solid Au NP as an example. By visualizing the vector field line of the optical force, we reveal the possible moving paths of the NP in the NB. This study can provide valuable insights for designing experiments to manipulate supercaviting NPs using plane waves.

Analysis of the Distribution and Influencing Factors of Diffusion Coefficient Model Parameters Based on Molecular Dynamics Simulations.

The establishment of mathematical models to predict the diffusion coefficients of gas and liquid systems have important theoretical significance and practical value. In this work, based on the previously proposed diffusion coefficient model DLV, the distribution and influencing factors of the model parameters characteristic length (L) and diffusion velocity (V) were further investigated using molecular dynamics simulations. The statistical analysis of L and V for 10 gas systems and 10 liquid systems was presented in the paper. New distribution functions were established to describe the probability distributions of molecular motion L and V. The mean values of the correlation coefficients were 0.98 and 0.99, respectively. Meanwhile, the effects of molecular molar mass and system temperature on the molecular diffusion coefficients were discussed. The results show that the effect of molecular molar mass on the diffusion coefficient mainly affects the molecular motion L, and the effect of system temperature on the diffusion coefficient mainly affects V. For the gas system, the average relative deviation of DLV and DMSD is 10.73% and that of DLV and experimental value is 12.63%; for the solution system, the average relative deviation of DLV and DMSD is 12.93% and that of DLV and experimental value is 18.86%, which indicates the accuracy of the new model results. The new model reveals the potential mechanism of molecular motion and provides a theoretical basis for further study of the diffusion process.

Arc-to-sheet printer for high-precision patterning with positional errors below 6 ppm at 3σ level: Trochoidal trajectory mechanism for rotary motion of arc

Pattern registration accuracy is a key property in printing processes, especially for miniaturized printed electronic devices that require the overlay of multiple layers. Except for inkjet and screen printing, various printing methods such as gravure offset, flexographic, and reverse offset printing typically use a roll-to-sheet type printer; however, registration has been limited, especially in the machine direction because of the speed variation in rotary motion of a cylindrical roll. We developed an arc-to-sheet type printer in which the rotary motion of an arc was realized by a trochoidal trajectory because such a mechanism can only be constructed using the translational motions of high-precision linear actuators. A prediction model for the behavior of the contact point of the arc during printing was also developed, along with a method for compensating for mechanical and assembly errors, which was verified by laser displacement measurements and torque exerted on the linear motor of table. Cu patterns reverse offset printed by the developed arc-to-sheet printer had positional errors of less than 3σ < 6 ppm with an optimized processing condition, achieving an unprecedented level of accuracy in printed electronics.

Slip and convective flow of Williamson nanofluid influenced by Brownian motion and thermophoresis mechanism in a horizontal microchannel

The current work is an attempt to explicate the repercussions caused by the transmission of heat as well as mass along with the enhancement of heat transmission for a steady MHD Williamson nano-substance flowing through the microchannel with slip and convective boundary conditions. The consequence of magnetic field and viscous dissipation on the flow is recorded. The simultaneous impact of the two well-known slip-mechanisms Brownian movement and thermophoresis is elaborated explicitly. The governed non-linear systems obtained were illustrated numerically via Runge-Kutta Fehlberg 4–5th order method based on shooting scheme. The pertinent features of assorted parameters have been scrutinized with the aid of graphs. Results reveal that magnetic parameter along with buoyancy ratio parameter was observed to decline the velocity whereas Weissenberg number displays both rising and depleting conduct on velocity. Temperature was reported to boost with Brownian motion and thermophoresis parameter whereas concentration profile declines with the same. Also drag across the enclosures of the microchannel with wall heat flux are computed and studied through graphs.

The nut-and-bolt motion of a bacteriophage sliding along a bacterial flagellum: a complete hydrodynamics model

The ‘nut-and-bolt’ mechanism of a bacteriophage-bacteria flagellum translocation motion is modelled by numerically integrating the 3D Stokes equations using a Finite-Element Method (FEM). Following the works by Katsamba and Lauga (Phys Rev Fluids 4(1): 013101, 2019), two mechanical models of the flagellum-phage complex are considered. In the first model, the phage fiber wraps around the smooth flagellum surface separated by some distance. In the second model, the phage fiber is partly immersed in the flagellum volume via a helical groove imprinted in the flagellum and replicating the fiber shape. In both cases, the results of the Stokes solution for the translocation speed are compared with the Resistive Force Theory (RFT) solutions (obtained in Katsamba and Lauga Phys Rev Fluids 4(1): 013101, 2019) and the asymptotic theory in a limiting case. The previous RFT solutions of the same mechanical models of the flagellum-phage complex showed opposite trends for how the phage translocation speed depends on the phage tail length. The current work uses complete hydrodynamics solutions, which are free from the RFT assumptions to understand the divergence of the two mechanical models of the same biological system. A parametric investigation is performed by changing pertinent geometrical parameters of the flagellum-phage complex and computing the resulting phage translocation speed. The FEM solutions are compared with the RFT results using insights provided from the velocity field visualisation in the fluid domain.

Theory of continental drift – causes of the motion. Historical review and observations

The theory of continental drift was published as early as 1912, but the mechanism and energy source of this motion has not yet been elucidated. In many cases, the generally accepted model of convection currents in the mantle contradicts observations such as the spreading of the ocean floor, the extension of rifts from triple points to all sides, the more or less unilateral movement of the lithosphere relative to the mantle, and others. In the first part of the double article, the evolution of views on this issue is shown, as well as measured data that document the important role of extraterrestrial energy sources for the movement of lithospheric plates in daily, annual and long-term climate cycles. In the second part of the two-part article, the entire theory of the mechanism of lithospheric plate motion will be outlined, based on the accumulation of incoming energy from the Sun in crustal rocks, the ratcheting mechanism, and the thermoelastic wave penetrating from the Earth's surface through the entire crust.

A Bionic Type Piezoelectric Actuator Based on Walking Motion and Asymmetrical L-Shaped Flexure Mechanisms

A bionic type piezoelectric actuator based on the walking motion of L-shaped flexure mechanisms has been proposed. By mimicking the walking motion of “human legs,” the proposed actuator is able to not only eliminate the backward motion to improve the motion efficiency, but also achieve the large working stroke with high output load easily. The special L-shaped flexure mechanism is employed as the “leg,” and the bionic walking motion is realized by applying two L-shaped flexure mechanisms alternately. The driving principle of the proposed piezoelectric actuator is discussed in detail, and the simulation is carried out to study the feasibility. An experimental system has been set up to investigate the actual working performance. According to the experimental results, the suitable phase difference between the two L-shaped flexure mechanisms to eliminate the backward motion is around <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</i> = 5°, the maximum speed is <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> = 1887.3 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m/s, the minimum stepping distance is 0.084 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m, and the maximum load is more than <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F_v</i> = 1100 g. The motion speed and the maximum load under the proposed bionic walking motion (two flexure mechanisms work together as “legs”) could be improved greatly for almost 3.7 and 1.7 times, respectively, compared with that of the traditional friction–inertial motion (only one flexure mechanism works). By eliminating the backward motion, the motion efficiency is improved about 52.9% under the condition of 120 V and 1 Hz. This article shows the feasibility of applying the bionic motion to improve the performance of piezoelectric actuators, which may be instructive for the design of piezoelectric actuators with large working stroke. In the future, it may be helpful for the real application of piezoelectric actuators in the fields of ultraprecision machining, optical engineering, and aerospace technology.

Design and implementation of electrical system morphing wing flight control on prototype light aircraft

This journal discusses the implementation and testing of the electrical morphing wing system on light aircraft prototypes, namely technology on the wing to increase the value of aerodynamic efficiency on the wing surface with experimental methods based on knowledge obtained from various literature sources. Using a configuration of eight servo actuators arranged in parallel for the aileron and flap functions as well as setting and control with a six-channel Flysky-FSi6 remote to control the movement of the master and slave aileron actuators as well as the flap function on the morphing wing. The design includes the layout of the actuator, setting commands on the remote and wiring system electrical components. Other aspects such as rib design, mechanism and material selection affect the overall distribution of motion produced by the servo actuator. Through the design of the electrical system morphing wing design on the prototype aircraft, it is proven to be able to support the needs of the morphing wing motion mechanism with the concept of an arrangement of eight actuators in parallel on the rib morphing wing. It is hoped that the concept of the morphing wing can be implemented and further developed so that it can be used on full-scale aircraft.