Curvature Of Trajectory Research Articles

Improving the method of controlling the search for surface and underwater objects by a hybrid robotic complex

One of the important scientific tasks of organising the control of searching for surface and underwater objects is to ensure the efficiency and trouble-free movement of a hybrid robotic complex in the modes of transition and search operation. An analysis of modern methods of controlling the search for surface and underwater objects by robotic vehicles in search operations, scientific and environmental research, monitoring, inspection and military underwater operations shows the need to use hybrid robotic systems. As part of the intellectualisation of the route planning process, it is relevant to solve the problem of synthesising an optimal trajectory to ensure that the search is carried out in all designated areas of the operation. The paper solves the problem of organising the management of searching for surface and underwater objects by a hybrid robotic complex, namely, building a route in the area of interest as an optimal spline trajectory of a moving object. The possibility of constructing a navigation function through the effective use of the curvature of the spline trajectory as a reproductive template for constructing an axonometric projection is determined. To accomplish this task, the paper improves the method of controlling the search for surface and underwater objects by a hybrid robotic complex by formalising the processes of planning the route of the hybrid robotic complex and the processes of information processing, forecasting the navigation situation and choosing a strategy for preventing dangerous situations by combining intelligent and numerical methods. The developed algorithm for constructing a search route for a hybrid robotic complex allows automated formation of spline trajectories in real time with synchronous submission of information about the parameters of the route to the control system of the hybrid robotic complex. This approach makes it possible to automate the search operation process and apply it in the CoCoRo and e-Navigation concepts

Automatic parking trajectory planning based on random sampling and nonlinear optimization

The current parking trajectory planning algorithms based on geometric connections or formulation of optimization problems in automatic parking systems have strict requirements on the starting position, lower planning efficiency and discontinuous curvature of the reference trajectory. In order to solve these problems, a hierarchical planning algorithm which is combined with nonlinear optimization and the improved RRT* algorithm (Rapidly-exploring Random Tree Star) with Reeds-Shepp curve is proposed in this paper. First, the improved RRT*RS algorithm with the rapid repulsion-straddle experiment is designed for enhancing the efficiency of path planning. Second, because of the shortcomings of the Reeds-Shepp curve that can meet the minimum turning radius but not realize the continuous curvature of the path, a nonlinear optimization problem based on convex-set obstacle constraints is formulated and solved. Finally, simulation results show that the proposed parking trajectory planning algorithm in this paper can plan an effective parking trajectory with continuous curvature in different starting positions and multiple parking scenarios.

Target-Distractor Competition Modulates Saccade Trajectories in Space and Object Space.

Saccade planning and execution can be affected by a multitude of factors present in a target selection task. Recent studies have shown that the similarity between a target and nearby distractors affects the curvature of saccade trajectories, because of target-distractor competition. To further understand the nature of this competition, we varied the distance between and the similarity of complex target and distractor objects in a delayed match-to-sample task to examine their effects on human saccade trajectories and better understand the underlying neural circuitry. For trials with short saccadic reaction times (SRTs) when target-distractor competition is still active, the distractor is attractive and saccade trajectories are deviated toward the distractor. We found a robust effect of distance consistent with saccade vector averaging, whereas the effect of similarity suggested the existence of an object-based suppressive surround. At longer SRTs, there was sufficient time for competition between the objects to complete and the distractor to be repulsive, which resulted in saccade trajectory deviations away from the distractor exhibiting the effects of a spatial suppressive surround. In terms of similarity, as the target-distractor similarity decreased, the initial saccade angle shifted toward the target, reflecting stronger distractor inhibition. There were no interactions between distance and similarity at any point in the time course of target-distractor competition. Together, saccade trajectories reflect target-distractor competition that is affected independently by both spatial and object space suppressive surrounds. The differences in saccade trajectories at short and long SRTs distinguish between active and completed decision-making processes.

Bubble detection and identification based on the vibration response for the sodium water reaction

Real-time bubble behavior characterization and localization are critical in the chemical industry, especially for leakage of sodium-water reactions. This research investigates the properties of bubble signals under different gas injection rates and sodium-water reactions by employing a vibration-based approach. Specifically, the time-frequency and energy characteristics of bubble signals were studied by vibration response. The bubble signals excited by the two kinds of experiments have the same characteristic frequency band of 200–400 Hz, and the maximum energy is obtained at 250 Hz. The bubble signal from the sodium-water reaction can be effectively recognized by identifying the differences in the characteristics of multiple parameters when the gas injection rate is 0.07 m3/h with a signal-to-noise ratio of 11.8–17.1 dB. On the basis of energy analysis of the bubble signal, a bubble signal source location method based on time domain statistics was proposed, and the trajectory curve of the bubble signal excited by the sodium water reaction in the initial 600 ms was successfully obtained with a position error rate less than 5%. Comparative analysis indicates that kurtosis was more sensitive for bubble signal recognition, while the Root Mean Square (RMS) and Standard Deviation (SD) values were more suitable for bubble positioning. Thus, this study complemented the present techniques and knowledge for bubble identification and localization in multiphase flow engineering.

Dynamic response analysis for the eastern North Pacific gray whale population: an alternative approach

Gerrodette and DeMaster (1990) conclude that dynamic response analysis indicates that the gray whale population passed through its maximum net productivity level (MNPL, approximately equivalent to MSY level) between 1967 and 1980. Their conclusion is examined using models for population trends which permit a point of inflection; these are fitted globally to the time series of census estimates available up to 1987-88. A cubic and a logistic model are used. The cubic model results indicate with almost 100% confidence that the population passed through MNPL within two years of 1973-74. However, both this conclusion and that of Gerrodette and DeMaster are considered to be unreliable. This is because the curves fitted by both analyses correspond to markedly decreasing population sizes over parts of the periods to which they apply. This is inconsistent with plausible population dynamics behaviour, which is itself an underlying pre-requisite for dynamic response analysis methodology. A suggestion is made as to how applications of dynamic response analysis methodology such as that of Boveng et al. (1988) could be adapted to ensure the necessary respect of such constraints. Results of a parametric bootstrap procedure for confidence interval estimation applied to the logistic model indicate that the probability that the population passed through MNPL during the period of the censuses is not large. The census data are scarcely adequate to allow for reliable estimates of the curvature of the population trajectory to be made. The logistic model dynamic response analysis indicates that there is a somewhat greater likelihood that the gray whale population was below rather than above its MNPL in 1990, given the data available at the time.

Design and research of single leg walking mechanism of quadruped robot

A new single-degree-of-freedom quadruped robot leg walking mechanism is proposed to solve the problems of more drive elements, more complex structure and control system in existing single-leg walking mechanism. The principle scheme and structure design of the leg walking mechanism of the quadruped robot are completed according to the requirements of the foot end trajectory curve and the actual motion characteristics. The dimensions of each rod of the single-leg crank rocker mechanism to meet the “inverted D-type” motion law at the E point on the linkage are solved by using the Burmester four-rod mechanism integrated graphical method. The kinematic equations at the P point of the foot end of the proposed scheme are derived by using the kinematic analysis. By ADAMS simulation, the displacement and velocity curves at the P point of the foot end can well meet the requirements of the foot end movement law. The present methodology can not only achieve the goal of less driving elements and more simple design in single-leg walking mechanism, and can well meet the requirements of walking stability and smoothness of motion.

Quantification of retinal vein and artery trajectories using second-order polynomial equation in eyes with vitreomacular traction

BackgroundsTo measure the degree of curvature of the retinal artery trajectory (RAT) and retinal vein trajectory (RVT) in the eyes of patients with vitreomacular traction (VMT) and compare them with their healthy fellow eyes. MethodsThis was a retrospective, cross-sectional, case-control study of 58 eyes of 29 patients with unilateral VMT. The participants were divided into two groups. Group 1 VMT was defined as having only morphological changes, while group 2 VMT was defined as morphological changes accompanied by the presence of a cyst or hole to quantify the severity of the disease. The RATs and RVTs were assessed from the color fundus photographs using the ImageJ program. The fundus photographs were rotated 90°. The course of the retinal arteries and veins were marked on a color fundus photograph and fitted to a second-degree polynomial curve (axe[x]/100+bx+c). The coefficient ‘‘a’’ was the width and steepness of the trajectories. The comparison between the RAT and RVT of VMT and healthy fellow eyes was investigated and the association between the RAT and RVT and the severity of disease were determined using the Image J program. ResultsEleven subjects were male, and 18 subjects were female. The mean ± SD age was 70.6 ± 7.6 years. Eighteen of the eyes had VMT in the right and 11 of the eyes had VMT in the left eye. Eleven eyes were in group 1 and 18 eyes were in group 2. Axial length (AL) was similar between the two groups (22.63 ± 1.20 mm vs 22.45 ± 1.45 mm p = 0.83) (Table 1). The mean RAT was 0.60 ± 0.18 in eyes with VMT and 0.51 ± 0.17in healthy eyes (p = 0.063). The mean RVT was 0.74 ± 0.24 in eyes with VMT and 0.62 ± 0.25 in healthy eyes for the whole group (p = 0.02). In group 1, the mean RVT of the eyes with VMT was statistically significantly higher than the healthy eyes (p = 0.014). There was not any statistically significant difference for the other parameters evaluated between eyes with VMT and healthy eyes according to the groups and the whole group. (Tables 2–4) ConclusionUnlike other vitreoretinal interface diseases such as epiretinal membrane and macular hole, VMT may be characterized by a narrower RVT, which is characterized by a larger “a” value.

Optimization Design and Performance Analysis of a Bionic Knee Joint Based on the Geared Five-Bar Mechanism.

Animal joint motion is a combination of rotation and translational motion, which brings high stability, high energy utilization, and other advantages. At present, the hinge joint is widely used in the legged robot. The simple motion characteristic of the hinge joint rotating around the fixed axis limits the improvement of the robot's motion performance. In this paper, by imitating the knee joint of a kangaroo, we propose a new bionic geared five-bar knee joint mechanism to improve the energy utilization rate of the legged robot and reduce the required driving power. Firstly, based on image processing technology, the trajectory curve of the instantaneous center of rotation (ICR) of the kangaroo knee joint was quickly obtained. Then, the bionic knee joint was designed by the single-degree-of-freedom geared five-bar mechanism and the parameters for each part of the mechanism were optimized. Finally, based on the inverted pendulum model and the Newton-Euler recursive method, the dynamics model of the single leg of the robot in the landing stage was established, and the influence of the designed bionic knee joint and hinge joint on the robot's motion performance was compared and analyzed. The proposed bionic geared five-bar knee joint mechanism can more closely track the given trajectory of the total center of mass motion, has abundant motion characteristics, and can effectively reduce the power demand and energy consumption of the robot knee actuators under the high-speed running and jumping gait.

Gestational weight gain growth charts adapted to Japanese pregnancies using a Bayesian approach in a longitudinal study: The Japan Environment and Children's Study.

Background Tracking gestational weight gain (GWG) during pregnancy makes it possible to optimize pregnancy outcomes and GWG growth curves are well suitable for this purpose. The GWG guidelines for Japanese were revised in 2021. However, currently, there are no GWG growth curves to guide women on how to gain weight to meet these guidelines.Methods Using data on 96,631 live births from the Japan Environment and Children's Study (JECS), we created descriptive GWG percentile curves estimated the trajectory of GWG required to meet the GWG guidelines stratified by pre-pregnancy body mass index (BMI) For both analyses, Bayesian mixed models with restricted cubic splines adjusted for maternal characteristics were used.Results GWG curves substantially differed by pre-pregnancy BMI, and were higher among multiparas and those with lower maternal age and with no previous disease. We estimated that underweight, normal weight, overweight and obese women who gain 8.4 to 11.1 kg, 6.4 to 9.1 kg, 3.8 to 6.5 kg, and <1.9 kg at 30 weeks of gestation are on the trajectory to reach the new guidelines at 40 weeks of gestation.Conclusions We provide GWG percentiles curves for Japanese women as well as GWG trajectory curves to meet the new GWG recommendations. These results may help pregnant women monitor weight during their pregnancy.

The temporal development of memory processes in source monitoring: An investigation with mouse tracking

The present study investigated whether we first remember an item (e.g., a word itself) and then its source (e.g., position on the screen) or whether the retrieval of item and source information can (partially) overlap. Participants were tested on the source either in immediate sequence to item recognition (as standard in source-monitoring research) or following as a separate block after full completion of the item recognition test to separate these processes in time, providing a baseline. Using the mouse-tracking procedure during the item and source tests, we analyzed how item and source decisions unfolded qualitatively over time. Despite no significant difference in the aggregated trajectory curvatures, more thorough analyses based on the individual trajectories revealed differences across the test formats. In the standard format, trajectories were less curved in the source than in the item test. In contrast, in the blocked format, this difference was in the other direction with source showing more curved trajectories than item. Alternative interpretations of mouse-trajectory curvatures on the source-monitoring paradigm and what their difference may imply for item and source processing are discussed.

Kinematic Modelling Analysis and Simulation of 6-DOF Manipulator

To test the rationality of the structure design of the six-degree-of-freedom manipulator, kinematics modelling and simulation were carried out. Firstly, the manipulator’s 3D model is created using SW platform. Secondly, the mathematical model of the manipulator is created according to the DH parameter method to complete the forward kinematics theoretical analysis. Finally, the reachable space of the end effector is simulated and an arc trajectory Simulation results indicate that the reachable space of the manipulator has no obvious cavity and the set trajectory curve is smooth without jumping points, the structure of the 6-DOF manipulator meets the design requirements.

花生荚果收获分离输送装置运动分析与试验研究

A peanut harvest separation and conveying device was designed considering the shortage of peanut harvest machinery and poor harvesting effect in China. The interaction between mechanism and pod-soil mixture was analysed to obtain the motion state of peanut relative separation conveyor. ADAMS simulation was applied to obtain the spatial curve of peanut trajectory in the separation process. The study determined that the optimum operating parameters of the separation conveyor were a drum speed of 280 r/min and an inclination angle of 19°. This study provides a theoretical basis for the further design of efficient peanut harvesting device.

ВЛИЯНИЕ ЖЕСТКОСТИ НАВЕСНОЙ СИСТЕМЫ НА УСТОЙЧИВОСТЬ КРИВОЛИНЕЙНОГО ДВИЖЕНИЯ МАШИННО-ТРАКТОРНОГО АГРЕГАТА

The search for constructive solutions to reduce the influence of inertial forces on the process of curved movement of a machine-tractor unit during curved movement is an urgent problem associated not only with reducing dynamic loads on the tractor and equipment aggregated with it, but with maintaining the stability of movement. A circular loop-free turn was chosen as the object of research. An experimental hinged system is designed to solve the tasks set in the work. It differs from the basic one in that between the hinged frame of the Belarus-1221.2 tractor and the hinged frame of the STV-12 seeder, an elastic element made of polyurethane is installed, which has the most suitable physical and mechanical properties. Nonlinear approximation of the array of abscissas and ordinates of the turn entry trajectory curve, calculated using the parametric form of equations for a circle of constant radius of the steady turn section, made it possible to describe the two considered stages of the theoretical turn trajectory by explicit non-linear functions. Analysis of arrays of theoretical and experimental values of the coordinates of the curves of the trajectories gave a constant value of the shift coefficient of the theoretical trajectory for the studied operating conditions of the unit 1.12, multiplying by which the explicit theoretical function obtained a parametric function of the actual trajectory of rotation. The comparison of trajectories showed the expediency of using elastic elements at the points of articulation of the tractor with the equipment, the use of polyurethane leads to the preservation of the trajectory, since the deviation of the actual trajectory from the theoretical one with the basic configuration in the height of the turning strip is 1.6... 2.25 m, and with the experimental one – 0.6 ... 1.13 m, the length of the theoretical curves is 8.21...10.82 m, and valid: with a base hitch of 11,223...12,792 m, with an experimental one – 9,652 ...11,854 m. A comparison of the results of theoretical studies with experimental data showed that their greatest difference does not exceed 4%, which allows us to conclude that they are correct.

Profilometry by zero-order interference fringe identification in the Commission Internationale de l’Eclairage system

In this study, a numerical procedure is proposed to determine the optical contact (peak of the coherence function) in a scanning white light interferential microscope. The Red, Green and Blue image of the correlogram is transformed to the Commission Internationale de l’Eclairage chromatic system with coordinates. The key element is to track the orientation of the curve (trajectory) which exhibits changes as it passes through the optical contact. The path described by the interferogram in this chromatic space makes it possible to localize, without ambiguity, the zero-order fringe and from this information to reconstruct the topography of an object of the order of a few tens of nanometres.

Molecular dynamics models of tapping mode atomic force microscopy

Macro-mechanical simulation software cannot easily simulate the atomic resolution of the tapping mode atomic force microscope (TM-AFM), so the accuracy of the corresponding mechanical model is questioned. In this paper, a TM-AFM simulation model is established using classical molecular dynamics (MD). The model simulated the tapping of gold (Au) and aluminum (Al) by probes with various amplitudes. The simulation yielded the z-direction force curves, trajectory curves and indentation curves of the probe. The amplitude change and the phase shift of the probe at various amplitudes were calculated from the direct measurement results. A contact jump and detachment jump become evident and are significant to energy and force results. The recovery ability of Al after indenting is smaller than that of Au. The energy calculations can be fitted to a high goodness of fit, reaching 0.99 and better; hence, the amplitude and phase shift variations of the probe can be used to fit the stored and dissipated energies, the sample energies when the sample is tapped. In this way, the TM-AFM is able to calculate the mechanical properties of the sample, and thus characterize the sample.

Design of a trajectory contour controller for a dual‐axis precision motion stage based on improved iterative learning

AbstractTo solve the problem of contour error (CE) arising from the dual‐axis coupling of the X–Y coordinate planar motor stage under reciprocating motion conditions in integrated circuit (IC) manufacturing, the following two perspectives are considered: indirect intervention from a single‐axis servo tracking error (TE) control and direct intervention from a dual‐axis cross‐coupling control (CCC). An improved motion controller is designed using the iterative learning control (ILC) principle in conjunction with the motion characteristics of the dual‐axis mechanism. Specifically, the variable gain iterative learning controller with a variable forgetting factor (VFF‐VGILC) is designed to address the characteristics of single‐axis trajectory repetition and variable velocity planning in dual‐axis coupling. The significance of the VFF‐VGILC is to increase the servo control bandwidth of a single axis. On the other hand, the cross‐coupled iterative learning controller (CCILC) is designed on the dual‐axis cross‐coupling, while a pre‐compensation strategy is introduced in the CCC structure to form the pre‐CCILC. After experimental designing and testing are performed, the X–Y coordinate planar motor stage can effectively reduce the CE under various trajectory movements compared with the traditional controller. The trajectory curves drawn can meet the motion control requirements better and effectively enhance the motion control capability of the mechanism.

The magnitude and pace of photosynthetic recovery after wildfire in California ecosystems

Wildfire modifies the short- and long-term exchange of carbon between terrestrial ecosystems and the atmosphere, with impacts on ecosystem services such as carbon uptake. Dry western US forests historically experienced low-intensity, frequent fires, with patches across the landscape occupying different points in the fire-recovery trajectory. Contemporary perturbations, such as recent severe fires in California, could shift the historic stand-age distribution and impact the legacy of carbon uptake on the landscape. Here, we combine flux measurements of gross primary production (GPP) and chronosequence analysis using satellite remote sensing to investigate how the last century of fires in California impacted the dynamics of ecosystem carbon uptake on the fire-affected landscape. A GPP recovery trajectory curve of more than five thousand fires in forest ecosystems since 1919 indicated that fire reduced GPP by [Formula: see text] g C m[Formula: see text] y[Formula: see text]([Formula: see text]) in the first year after fire, with average recovery to prefire conditions after [Formula: see text] y. The largest fires in forested ecosystems reduced GPP by [Formula: see text] g C m[Formula: see text] y[Formula: see text] (n = 401) and took more than two decades to recover. Recent increases in fire severity and recovery time have led to nearly [Formula: see text] MMT CO[Formula: see text] (3-y rolling mean) in cumulative forgone carbon uptake due to the legacy of fires on the landscape, complicating the challenge of maintaining California's natural and working lands as a net carbon sink. Understanding these changes is paramount to weighing the costs and benefits associated with fuels management and ecosystem management for climate change mitigation.

Trajectory Optimization of High-Speed Robotic Positioning with Suppressed Motion Jerk via Improved Chicken Swarm Algorithm

For the trajectory optimization of the time–jerk of robotic arms with a chicken swarm optimization algorithm, using five-order B-spline interpolation can ensure smooth and continuous acceleration, but, due to the performance problems of the algorithm, the low solution accuracy and the slow convergence speed, the ideal trajectory curve cannot be obtained. To address these problems, an improved chicken swarm algorithm based on a parallel strategy and dynamic constraints (PDCSO) is proposed, where the rooster update method is employed with a parallel strategy using X-best guidance and a Levy flight step. Dynamic constraints for the rooster are given, followed by the hens, and the optimal rooster position that improved the convergence accuracy while preventing the local optimum was determined. Simulation experiments using 18 classical test functions showed that the PDCSO algorithm outperformed other comparative algorithms in terms of convergence speed, solution accuracy and solution stability. Simulation validation in ADAMS and real machine tests proved that PDCSO can effectively reduce the running time and motion shock for robotic arms and improve the execution efficiency of such arms.

Imaging-based 3D particle tracking system for field characterization of particle dynamics in atmospheric flows

A particle tracking velocimetry apparatus is presented that is capable of measuring three-dimensional particle trajectories across large volumes, of the order of several meters, during natural snowfall events. Field experiments, aimed at understanding snow settling kinematics in atmospheric flows, were conducted during the 2021/2022 winter season using this apparatus, from which we show preliminary results. An overview of the methodology, wherein we use a UAV-based calibration method, is provided, and analysis is conducted of a select dataset to demonstrate the capabilities of the system for studying inertial particle dynamics in atmospheric flows. A modular camera array is used, designed specifically for handling the challenges of field deployment during snowfall. This imaging system is calibrated using synchronized imaging of a UAV-carried target to enable measurements centered 10 m above the ground within approximately a 4 m $$\times$$ 4 m $$\times$$ 6 m volume. Using the measured Lagrangian particle tracks, we present data concerning 3D trajectory curvature and acceleration statistics, as well as clustering behavior using Voronoï analysis. The limitations, as well as potential future developments, of such a system are discussed in the context of applications with other inertial particles.

The trajectories of physical growth in 4 months postnatal corrected age among preterm infants discharged from neonatal intensive care units and associated factors: A prospective study

ObjectivesGrowth retardation is a risk for premature infants. In addition to demographic and perinatal factors, preterm infants’ physical growth may be affected by neonatal intensive care unit (NICU) stress, maternal postpartum depression, and mother-infant interaction. This study aimed to investigate the trajectories of physical growth in 4 months corrected age among preterm infants discharged from the NICU and the impactors on these trajectories. MethodsA prospective study was conducted among 318 preterm infants from September 2019 to April 2021 in Shanghai, China. Latent growth modeling was applied to identify the weight, length, and head circumference growth trajectories in 4 months corrected age and explore the effects of demographic and medical characteristics, infant stress during NICU stay, maternal postpartum depression, and mother-infant interaction on each trajectory. ResultsUnconditional latent growth models showed curve trajectories with increasingly slower growth in weight, length, and head circumference until 4 months of corrected age. Conditional latent growth models showed that a longer length of stay in the NICU and more skin punctures were negatively associated with weight at 40 weeks corrected gestational age (β = −0.43 and −0.19, respectively, P < 0.05). The maternal postpartum depression between 40 weeks corrected gestational age and 1 month corrected postnatal age was associated with a lower growth rate of length (β = −0.17, P = 0.040), while between 2 and 3 months corrected postnatal age, there were lower growth rates of weight and head circumference (β = −0.15 and −0.19, respectively, P < 0.05). The mother-infant interaction scores between 40 weeks corrected gestational age and 1 month corrected postnatal age negatively predicted the growth rate of weight (β = −0.19, P = 0.020). ConclusionThe physical growth trajectories of preterm infants discharged from the NICU were influenced by infant stress during the NICU stay, maternal postpartum depression and mother-infant interaction.