Motion State Research Articles

Multifunctional Human-Computer Interaction System Based on Deep Learning-Assisted Strain Sensing Array.

Continuous and reliable monitoring of gait is crucial for health monitoring, such as postoperative recovery of bone joint surgery and early diagnosis of disease. However, existing gait analysis systems often suffer from large volumes and the requirement of special space for setting motion capture systems, limiting their application in daily life. Here, we develop an intelligent gait monitoring and analysis prediction system based on flexible piezoelectric sensors and deep learning neural networks with high sensitivity (241.29 mV/N), quick response (66 ms loading, 87 ms recovery), and excellent stability (R2 = 0.9946). The theoretical simulations and experiments confirm that the sensor provides exceptional signal feedback, which can easily acquire accurate gait data when fitted to shoe soles. By integrating high-quality gait data with a custom-built deep learning model, the system can detect and infer human motion states in real time (the recognition accuracy reaches 94.7%). To further validate the sensor's application in real life, we constructed a flexible wearable recognition system with human-computer interaction interface and a simple operation process for long-term and continuous tracking of athletes' gait, potentially aiding personalized health management, early detection of disease, and remote medical care.

Research on Stay Cable Tension Estimation Based on Vision-Based Monitoring System

The cables in cable-stayed bridges are the primary load-bearing components, making the accurate monitoring of cable tension crucial for assessing the service reliability of the cables and the overall safety of the bridge. This study presents the development of a non-contact, vision-based monitoring system utilizing computer vision technology for monitoring cable tension in cable-stayed bridges. The monitoring system comprises an industrial camera equipped with an infrared filter and an infrared target lamp, employing a sub-pixel template matching algorithm to achieve high-precision cable tension measurement under long-distance and multi-frequency motion conditions. Model experiments were conducted to validate the accuracy and stability of the vision-based monitoring system. Results from long-distance model experiments indicate that the system can accurately measure frequencies across various distances, with a maximum frequency error of only 0.05%. Additionally, results from multi-frequency model experiments demonstrate that the system can accurately measure multiple vibration frequencies, with a maximum frequency error of just 0.4%.

Synchronization phenomenon in a vibrating system driven by four eccentric rotors mounted in the orthogonal plane

The engineering application of vibration synchronization of multiple eccentric rotors (ERs) with the same rotational plane in far resonance is limited due to the constraints of motion characteristics and resultant force cancellation. Therefore, a dynamic model of four ERs distributed in two orthogonal planes is proposed in this paper, which is designed to increase the excitation force and drive the vibrating body to achieve the motion in a straight line. Based on the governing equation corresponding to the dynamic model firstly, the synchronous condition of four ERs and its stability condition are deduced. Then, the phase relationship of four ERs is obtained by numerical analysis, and the resultant force of four ERs in each phase difference is further studied to determine the motion trajectory of the vibrating body. Lastly, theoretical results are verified by four sets of experiments, which show that there are two stable motion states of the system. In each motion state, the resultant force of four ERs is increased compared to two ERs, and the system also moves in a straight line. Therefore, the model presented in this paper can provide a theoretical basis for designing large vibration machinery.

Optimization study of tail-lateral occupant injury and restraint system for an off-road vehicle ramp rollover

The process of rollover accidents involving specialized vehicles is characterized by intense motion and long duration. Although these accidents are infrequent, they often lead to a high fatality rate. In this study, we utilized LS-Dyna software to simulate the rollover of a vehicle on a side ramp. This simulation aimed to verify the reliability of our model establishment by comparing the vehicle’s motion attitude and center-of-mass acceleration with experimental results. Additionally, we sought to investigate the lateral occupant injuries that occur in the tail section of a certain type of specialized vehicle during a rollover. Initially, we obtained the vehicle’s motion trajectory and the dummy’s motion state through simulation. Subsequently, we extracted the injury response of each part of the dummy. We then simplified the entire vehicle model and made improvements to the occupant restraint system, ultimately designing an enhanced system. Finally, we approximated and replaced the entire vehicle model by establishing an approximation model. We combined this with an optimization algorithm to optimize the occupant restraint system. The simulation results demonstrate that the improved occupant restraint system significantly reduces the axial force on the neck of the occupant and the comprehensive evaluation index of injury. Furthermore, the simulation results for each component fall below the injury limit value specified in the FMVSS208 crash occupant protection standard. Therefore, the improved occupant restraint system proposed in this study effectively mitigates lateral occupant injury during rollover accidents.

On the feasibility of detecting quantum delocalization effects on relativistic time dilation in optical clocks

Abstract We derive the predicted time dilation of delocalized atomic clocks in an optical lattice setup in the presence of a gravitational field to leading order in quantum relativistic corrections. We investigate exotic quantum states of motion whose relativistic time dilation is outside of the realm of classical general relativity, finding a regime where 24 Mg optical lattice clocks currently in development would comfortably be able to detect the special-relativistic contribution to the quantum effect (if the technical challenge of generating the necessary states can be met and the expected accuracy of such clocks can be attained). We find that the gravitational contribution, on the other hand, is negligible in this setup. We provide a detailed experimental protocol and analyse the effects of noise on our predictions. We also show that the magnitude of our predicted quantum time dilation effect remains just out of detectable reach for the current generation of 87 Sr optical lattice clocks. Our calculations agree with the predicted time dilation of classical general relativity when restricting to Gaussian states.

MmSTCT: spatial–temporal convolution transformer network considering driving intention for multimodal vehicle trajectory prediction of highway

Due to the dynamic nature of traffic flow and the uncertainty of drivers' maneuvers, multimodal trajectory prediction remains challenging. In this paper, a multimodal vehicle trajectory prediction model is proposed based on the encoder-decoder structure, utilizing a spatial-temporal dilated causal convolutional transformer network for the hierarchical extraction of driving intention and spatial interaction features. Specifically, temporal information is extracted from the initial motion states by utilizing a bi-directional long short-term memory network. Subsequently, the social interaction module and spatial-temporal dependency module are introduced to model the interactive influences among surrounding vehicles and the target vehicle at the same timestamp as well as at different timestamps. Then adaptive fusion of driving intention is performed to generate multiple queries for accommodating the output of multimodal trajectory prediction module in a non-autoregressive manner. The effectiveness of the proposed model is demonstrated through experimental evaluations on the NGSIM, HighD and CitySim datasets.

Non-smooth self-excited vibration of a novel dynamical model for a disc brake

This paper proposes a new dynamic model for the study of friction-induced self-excited vibration of a disc brake system, where the pad’s motions in both radial and circumferential/tangential directions are included, which is in stark contrast to the previous studies that normally consider the pad’s motion in the tangential/circumferential direction only. The non-smooth dynamics of the system including three different states of motion, i.e., stick, slip and separation, is investigated. Both the linear stability analysis and the transient dynamic analysis are performed. The numerical results in the linear stability analysis indicate that the inclusion of pad’s radial motion in the present brake model significantly expands the ranges of operating parameters for dynamic instability than the brake model with only circumferential/tangential motion for the pad. For the transient dynamic analysis, two different methods, i.e., the time integration method and the shooting method, are employed for the calculation of steady-state response. The accuracy and efficiency of the shooting method are subsequently examined. The numerical results show rich bifurcation behaviours of the steady-state response in the present brake model with the variations of brake pressure and disc speed , and (the stiffness of the inclined spring in the radial direction) is a key parameter for controlling the occurrence of chaotic vibration in the system. Conflict of Interest Statement The authors declare no conflicts of interest.

Thermal modeling and analysis of multi-mover motors considering mover quantity and dynamic states

—Multi-mover motors are widely used in logistics transportation systems. However, the unique number of movers and variations in motion states complicate the distribution of loss and thermal characteristics, thereby increasing the difficulty of calculating temperature rise. In this paper, a winding loss calculation method that considers the multi-condition and dynamic characteristics of multi-mover motors is proposed. The convective heat transfer coefficient (CHTC) is calculated using computational fluid dynamics (CFD) and response surface methodology (RSM), with a detailed analysis of velocity distribution characteristics. The interactive effects of mover speed, acceleration, mover quantity, and the distance between adjacent movers on the CHTC are investigated. A simplified yet accurate thermal modeling is developed, reducing the required time for a single operating condition from 4 h to 0.5 h, with an error of only 4 %. Through both single variable and multivariable analyses, the thermal characteristics of multi-mover motors under different conditions are revealed. Finally, a prototype is created and tested under various operating conditions. The discrepancies between the experimental and calculated values are within 5 %, validating the accuracy of the proposed model and analysis.

Vehicle motion state estimation based on WOA-SVR

Vehicle motion state estimation based on WOA-SVR

Microstimulation-based path tracking control of pigeon robots through parameter adaptive strategy

Research on animal robots utilizing neural electrical stimulation is a significant focus within the field of neuro-control, though precise behavior control remains challenging. This study proposes a parameter-adaptive strategy to achieve accurate path tracking. First, the mapping relationship between neural electrical stimulation parameters and corresponding behavioral responses is comprehensively quantified. Next, adjustment rules related to the parameter-adaptive control strategy are established to dynamically generate different stimulation patterns. A parameter-adaptive path tracking control strategy (PAPTCS), based on fuzzy control principles, is designed for the precise path tracking tasks of pigeon robots in open environments. The results indicate that altering stimulation parameter levels significantly affects turning angles, with higher UPN and PTN inducing changes in the pigeons' motion state. In experimental scenarios, the average control efficiency of this system was 82.165%. This study provides a reference method for the precise control of pigeon robot behavior, contributing to research on accurate target path tracking.

Experimental Investigation of the Heaving Motion Effect on Critical Heat Flux Phenomena and Wall Temperature Fluctuation Using R134a for Floating Nuclear Applications

This study experimentally investigated the flow boiling critical heat flux (CHF) under heaving conditions pertinent to floating nuclear power plants (FNPPs). Experiments were conducted using R134a to simulate the operational pressure of pressurized water reactors, extending the CHF database to a pressure range of 5 to 18 MPa. The tested heaving motion reached up to 0.6 g of maximum acceleration, with a period that varied from 3 to 5.3 s. A parametric trend involving mass flux, critical quality, and motion conditions was analyzed through extensive tests encompassing static and heaving conditions. The results showed that CHF reduction was observed due to the effect of heaving acceleration, even in the absence of oscillations in other thermal-hydraulic factors. The CHF reduction was up to 9% in the present experimental conditions. The heaving motion effect was prominent under two specific thermal-hydraulic conditions: when the critical quality was close to zero and when it exceeded the value of 0.6. Furthermore, an examination of wall temperature responses suggested that a longer period of heaving motion can lead to an earlier occurrence of CHF. This fundamental effort was conducted to enhance the understanding of the CHF mechanism under motion conditions, with the aim of contributing to the safe and efficient design of FNPPs.

Modelling of 2-D seismic wave propagation in heterogeneous porous media: a frequency-domain finite-element method formulated by variational principles

SUMMARY We propose a frequency-domain finite-element (FDFE) method to model the 2-D P–SV waves propagating in porous media. This specific finite-element method (FEM) is based on the framework of variational principles, which differs from previously widely used FEMs that rely on the weak formulations of the governing equations. By applying the calculus of variations, we establish the equivalence between solving the stress–strain relations, equations of motion and boundary conditions that govern the propagation of P–SV waves, and determining the extremum or stationarity of a properly defined functional. The structured rectangular element is utilized to partition the entire computational region. We validate the FDFE method by conducting a comparison with an analytically-based method for models of a horizontal planar contact of two poroelastic half-spaces, and a poroelastic half-space with a free surface. The excellent agreements between the analytically-based solutions and the FDFE solutions indicate the effectiveness of the FDFE method in modelling the poroelastic waves. Modelling results manifest that both propagative and diffusive natures of the Biot slow P wave can be effectively modelled. The proposed FDFE method simulates wavefields in the frequency domain, allowing for easy incorporation of frequency-dependent parameters and enabling parallel computational capabilities at each frequency point (sample). We further employ the developed FDFE method to model two simplified poroelastic reservoirs, one with gas-saturated sandstone and the other with oil-saturated sandstone. The results suggest that changing the fluid phase of the sandstone reservoir from gas to oil can substantially impact the recorded solid and relative fluid–solid displacements. The modelling suggests that the proposed FDFE algorithm is a useful tool for studying the propagation of poroelastic waves.

Advancing particle forces and motion dynamics in centrifugal concentrator based on flow field simulation

ABSTRACT The forces and motion state of particles within the fluid domain of the Knelson concentrator have long been a focal point for researchers. Presently, Stokes’ flow laws are commonly employed as the basis for theoretical calculations. However, this approach somewhat deviates from reality due to challenges in determining the Reynolds number of particles in the centrifugal force field during practical work. Additionally, the relationship between the Reynolds number and the drag coefficient remains undetermined in certain ranges. This study presents a high predictive relationship curve, obtained using fitting software, to supplement and rectify the limitations in the existing relationship. Leveraging fluid simulation software, this research determines the Reynolds number of particles of different sizes and densities within the fluid, offering a methodological reference for similar flow field problems. A new drag coefficient function is proposed and validated for the Reynolds number range of 1 to 20, addressing a gap in existing theoretical models. The simulation results indicate that under the suitable separation conditions of −0.074 + 0.02 mm particles, the concentrate particles overcome the flushing effect of the reverse washing water and move in the opposite direction to the fluid. This advancement not only improves the theoretical framework but also offers significant academic and practical value by enhancing the efficiency of particle separation in the Knelson concentrator.

Effect of turning conditions on the indirect liquid-cooled battery thermal management in the electric vehicle

There exist many kinds of turning situations for driving, and the turns would lead to additional forces on the liquid in the channel, which can affect the liquid-cooled battery pack thermal management of electric vehicles. However, few studies have investigated the cooling effect in battery packs during turns in electric vehicles. In view of this, the purpose of this paper is to study how the cooling effect of the battery pack varies under turning conditions and explain the mechanisms behind it. Based on an indirect liquid-cooled battery pack model and by applying turning conditions to the battery pack under different C-rate discharges, the cooling effect of the battery pack is investigated. It is found that the maximum temperature of the battery pack increases significantly under the turning motion condition and increases with vehicle speed. In addition, the temperature uniformity of the battery pack is also greatly deteriorated by the turning motion. Turning results in an increase of the inertial force, which acts on the cooling fluid and decreases the fluid mass flow, ultimately reducing the cooling effect of the battery pack.

Flexible Tactile Sensors with Gradient Conformal Dome Structures.

The trade-off between high sensitivity and wide detection range remains a challenge for flexible capacitive pressure sensors. Gradient structure can provide continuous deformation and lead to a wide sensing range. However, it simultaneously augments the distance between two electrodes, which diminishes the variation in the relative distance and results in a decreased sensitivity. Herein, a conformal design is introduced into the gradient structure to construct a flexible capacitive pressure sensor. The gradient conformal dome structure is fabricated by a simple reverse dome adsorption process. Taking advantage of the progressive deformation behavior of the gradient dielectric, and the significant improvement of relative distance variation between two electrodes from the conformal design, the sensor achieves a sensitivity of 0.214 kPa-1 in an ultrabroad linear range up to 200 kPa. It maintains high-pressure resolution under the preload of 10 and 100 kPa. Benefiting from the rapid response and excellent repeatability, the sensor can be used for physiological monitor and human motion detection, including arterial pulse, joint bending, and motion state. The gradient conformal design strategy may pave a promising avenue to develop pressure sensors with high sensitivity and wide linear range.

Slowing Down a Coherent Superposition of Circular Rydberg States of Strontium.

Rydberg alkaline earth atoms are promising tools for quantum simulation and metrology. When one of the two valence electrons is promoted to long-lived circular states, the second valence electron can be optically manipulated without significant autoionization. We harness this feature to demonstrate laser slowing of a thermal atomic beam of circular strontium atoms. By driving the main ion core 422nm wavelength resonance, we observe a velocity reduction of 50 m/s without significant autoionization. We also show that a superposition of circular states undergoes very weak decoherence during the cooling process, up to the scattering of more than 1000 photons. This robustness opens new perspectives for quantum simulations over long timescales with circular atoms, while simultaneously cooling their motional state. It makes it possible to mitigate the harmful effects of unavoidable heating due to spin-motion coupling during a quantum simulation.

Design Optimization and Experimentation of Triple-Head Gradually Reducing Spiral Precision Fertilizer Apparatus

In order to solve the problems of existing spiral fertilizer apparatuses, such as the variation in cavity filling rate with rotational speed, fluctuation of fertilizer discharge flow, and inability to discharge fertilizer precisely, a triple-head gradually reducing spiral fertilizer apparatus is designed, which gradually compresses fertilizer particles through the triple-head reducing fertilizer spiral structure to achieve complete cavity filling and uniform fertilizer discharge. The main factors that affect the particle motion state and the structural size of the spiral fertilizer through theoretical analysis are determined, and its theoretical fertilizer discharge amount and rotational speed are calculated. Using EDEM (Discrete Element Method Software 2022) to establish a simulation model of a single-head gradually reducing fertilizer apparatus, the spiral lead reduction percentage x1, spiral diameter reduction percentage x2, and rotational speed x3 are determined as experimental factors, and the filling rate μ and spiral torque Yaverage are used as experimental indicators to conduct a simulation study on the secondary universal rotation combination design experiment. The results show that when the rotational speed is 95 r/min, the spiral lead reduction percentage is 60.00~73.21%, the spiral diameter reduction percentage is 86.55~97.05%, the filling rate μ is greater than 95%, and the spiral torque Yaverage is less than 16 N·m. In order to further improve the uniformity of fertilizer discharge and ensure the controllable accuracy of fertilizer discharge, comparative verification experiments are conducted on single-, double-, and triple-head gradually reducing spiral fertilizer discharge devices and ordinary spiral fertilizer discharge devices. The results show that the precision of the gradually reducing spiral fertilizer apparatus is better than that of the ordinary spiral fertilizer apparatus. Moreover, it is determined that the three-head style performed best. The triple-head gradually reducing spiral fertilizer apparatus is also validated by randomly adjusting six rotational speeds. The experiment results show that the average deviation of the fertilizer discharge flow rate of the fertilizer apparatus from the preset value is 3.16%. The two have a minor deviation, and the fertilizer precision is high. Precise control of the amount of fertilizer discharged can be achieved by adjusting the rotational speed, and the research can provide a specific reference for the improved design and precise control of the spiral fertilizer apparatus.

Vertical vibration analysis of rolling interface based on dynamic rolling force with variable friction characteristics

This study investigates the impact of variable friction characteristics at the rolling interface on the vertical vibration of plate and strip rolling mills. Based on the optimized Karman equilibrium theory, a dynamic rolling force model considering the front and back tension, elastic stretching, and rolling speed was established. The amplitude-frequency response equation of rolling mill system is solved by multi-scale method, and the influence of main parameters on vertical vibration of rolling mill system is analyzed. The results show that the increase of the first stiffness coefficient of dynamic rolling force leads to the decrease of the principal common amplitude of the system. On the contrary, when the third stiffness coefficient increases, the system exhibits a jump phenomenon. When the third stiffness coefficient of dynamic rolling force is reduced within a certain range, a stable and unique solution is obtained without jumping phenomenon. Moreover, the smaller the damping coefficient of the upper and lower roller system is, the larger the vibration amplitude is and the jump phenomenon occurs. Decreasing the external disturbance force can effectively reduce the system’s vertical vibration amplitude and suppress the resonance. In addition, with the change of external disturbance force, the roll system of the rolling mill shows a variety of complex motion states, such as periodic motion, double-periodic motion, and chaotic motion. The research results provide an effective theoretical reference for the suppression of vertical vibration of rolling mill.

DIO-SLAM: A Dynamic RGB-D SLAM Method Combining Instance Segmentation and Optical Flow.

Feature points from moving objects can negatively impact the accuracy of Visual Simultaneous Localization and Mapping (VSLAM) algorithms, while detection or semantic segmentation-based VSLAM approaches often fail to accurately determine the true motion state of objects. To address this challenge, this paper introduces DIO-SLAM: Dynamic Instance Optical Flow SLAM, a VSLAM system specifically designed for dynamic environments. Initially, the detection thread employs YOLACT (You Only Look At CoefficienTs) to distinguish between rigid and non-rigid objects within the scene. Subsequently, the optical flow thread estimates optical flow and introduces a novel approach to capture the optical flow of moving objects by leveraging optical flow residuals. Following this, an optical flow consistency method is implemented to assess the dynamic nature of rigid object mask regions, classifying them as either moving or stationary rigid objects. To mitigate errors caused by missed detections or motion blur, a motion frame propagation method is employed. Lastly, a dense mapping thread is incorporated to filter out non-rigid objects using semantic information, track the point clouds of rigid objects, reconstruct the static background, and store the resulting map in an octree format. Experimental results demonstrate that the proposed method surpasses current mainstream dynamic VSLAM techniques in both localization accuracy and real-time performance.

Experimental-based hydrodynamic simulation of submarine glider for wave gliders

The wave glider is an unmanned surface vehicle propelled by wave energy, consisting of three main components: a surface float, a submarine glider, and a tether. The submarine glider serves as the primary propulsion mechanism, converting the wave-induced motions of the float into forward thrust, which is crucial for the wave glider’s energy absorption efficiency. However, predicting the motion performance of the submarine glider presents a significant challenge due to its complex and unique structure. In this study, we establish a kinematic and dynamic model of the submarine glider’s hydrofoils, considering the elastic effects such as spring stiffness, spring preload, and spring attachment positions. To support this model, wind tunnel tests were conducted to determine the lift and drag coefficients of the submarine glider under various motion states. Utilizing the elastic hydrofoil model and the experimentally obtained lift and drag coefficients, we developed a comprehensive kinematic and dynamic simulation model of the submarine glider under heave excitation forces. To validate the accuracy of this model, performance tests for the submarine glider were designed under different vertical excitation forces , with results compared to simulation outcomes. The findings indicate that the deviation between simulated and experimental outcomes is less than 5%, demonstrating the model’s precision. This accurate simulation capability allows for detailed analysis of the effects of various design parameters on the glider’s performance and lays a solid foundation for high-accuracy motion simulation of the entire wave glider.