Trajectory Method Research Articles

A review of dynamic parameters identification for manipulator control

Due to the important role of the manipulator dynamic model in manipulation control, the identification of the dynamic parameters of manipulators has become a research hotspot once again. In this paper, we present an overview of the modeling of manipulator dynamics, the optimization methods of excitation trajectory, the identification methods for dynamic parameters, and the identification of friction model parameters. First, the process and basic methods of identification of manipulation dynamic parameters are summarized, and the optimization methods for excitation trajectory are analyzed in detail. Further, friction model parameter identification and the physical feasibility of dynamic parameters are discussed. These are research hotspots associated with the identification of dynamic parameters of manipulators. The backgrounds and solutions of the problems of physical feasibility and identification of friction parameters are reviewed in this paper. Finally, neural networks and deep learning methods are discussed. The neural networks and deep learning methods have been used to improve the accuracy of identification. However, deep learning methods and neural networks need more in-depth analysis and experiments. At present, the instrumental variable method with complete physical feasibility constraints is an optimal choice for dynamic parameter identification. Moreover, this review aims to present the important theoretical foundations and research hotspots for the identification of manipulation dynamic parameters and help researchers determine future research areas.

Controlling Chemical Reactivity with Optimally Oriented Electric Fields: A Generalization of the Newton Trajectory Method.

The use of oriented external electric fields (OEEF) as a tool to accelerate chemical reactions has recently attracted much interest. A new model to calculate the optimal OEEF of the least intensity to induce a barrierless chemical reaction path is presented. A suitable ansatz is provided by defining an effective potential energy surface (PES), which considers the unperturbed or original PES of the molecular reactive system and the action of a constant OEEF on the overall dipole moment of system. Based on a generalization of the Newton Trajectories (NT) method, it is demonstrated that the optimal OEEF can be determined upon locating a special point of the potential energy surface (PES), the so-called "optimal bond-breaking point" (optimal BBP), for which two different algorithms are proposed. At this point, the gradient of the original or unperturbed PES is an eigenvector of zero eigenvalue of the Hessian matrix of the effective PES. A thorough discussion of the geometrical aspects of the optimal BBP and the optimal OEEF is provided using a two-dimensional model, and numerical calculations of the optimal OEEF for a SN2 reaction and the 1,3-dipolar retrocycloaddition of isoxazole to fulminic acid plus acetylene reaction serve as a proof of concept. The knowledge of the orientation of optimal OEEF provides a practical way to reduce the effective barrier of a given chemical process.

Stability and Free Radical Production for CO2 and H2 in Air Nanobubbles in Ethanol Aqueous Solution.

In this study, 8% hydrogen (H2) in argon (Ar) and carbon dioxide (CO2) gas nanobubbles was produced at 10, 30, and 50 vol.% of ethanol aqueous solution by the high-speed agitation method with gas. They became stable for a long period (for instance, 20 days), having a high negative zeta potential (−40 to −50 mV) at alkaline near pH 9, especially for 10 vol.% of ethanol aqueous solution. The extended Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory was used to evaluate the nanobubble stability. When the nanobubble in ethanol alkaline aqueous solution changed to an acidic pH of around 5, the zeta potential of nanobubbles was almost zero and the decrease in the number of nanobubbles was identified by the particle trajectory method (Nano site). The collapsed nanobubbles at zero charge were detected thanks to the presence of few free radicals using G-CYPMPO spin trap reagent in electron spin resonance (ESR) spectroscopy. The free radicals produced were superoxide anions at collapsed 8%H2 in Ar nanobubbles and hydroxyl radicals at collapsed CO2 nanobubbles. On the other hand, the collapse of mixed CO2 and H2 in Ar nanobubble showed no free radicals. The possible presence of long-term stable nanobubbles and the absence of free radicals for mixed H2 and CO2 nanobubble would be useful to understand the beverage quality.

Stable Isotopes of Precipitation in the Eastern Tarim River Basin and Water Vapor Sources

The in-situ monitoring of stable hydrogen and oxygen isotopes (δ18O and δ2H) in precipitation is helpful to understand the processes of water phase change, mixing, and transportation. Due to the arid climate in the eastern Tarim River basin, water resources are the key factor affecting the regional sustainable development. However, the understanding of stable hydrogen and oxygen isotopes in precipitation is still limited for this region. Based on the isotope data of 103 precipitation samples collected at four stations in the eastern Tarim River basin from June 2019 to September 2020, the spatial and temporal characteristics of stable hydrogen and oxygen isotopes in precipitation were analyzed, and the connections between stable isotopes and moisture sources were discussed. The findings provide a reference for the application of environmental isotope tracers in arid areas. The results show that, ① the four sampling stations generally presented an increasing trend in precipitation stable isotopic values from north to south, and the isotopic values were higher in summer and lower in winter. The d-excess value in the study region was smaller than the national average, and the slope of the local meteoric water line exhibited a significant arid characteristic. ② There was a positive correlation between precipitation stable isotopes and air temperature in the study region, whereas a weak negative relationship was seen between d-excess and air temperature. The negative correlation occurred between δ18O and relative humidity, and the d-excess value exhibited a positive correlation with relative humidity. ③ The backward trajectory showed that the eastern Tarim River basin is mainly controlled by the westerlies paths. The proportion of air mass that comes from the middle and short distance is relatively large. The concentration weighted trajectory method showed that the farther from the precipitation sampling site, the more stable the d-excess value was. The closer to the sampling site, the more frequently the concentration changed, indicating that the d-excess value was greatly affected by the local water vapor recycling.

Automatic Planning Method of Reduction Trajectory for Parallel Fracture Surgery Robot

Automatic Planning Method of Reduction Trajectory for Parallel Fracture Surgery Robot

Application of the method of parallel trajectories on modeling the dynamics of COVID-19 third wave.

In this paper, we present a new method for successfully simulating the dynamics of COVID-19, experimentally focusing on the third wave. This method, namely, the Method of Parallel Trajectories (MPT), is based on the recently introduced self-organized diffusion model. According to this method, accurate simulation of the dynamics of the COVID-19 infected population evolution is accomplished by considering not the total data for the infected population, but successive segments of it. By changing the initial conditions with which each segment of the simulation is produced, we achieve close and detailed monitoring of the evolution of the pandemic, providing a tool for evaluating the overall situation and the fine-tuning of the restrictive measures. Finally, the application of the proposed MPT on simulating the pandemic's third wave dynamics in Greece and Italy is presented, verifying the method's effectiveness.

Research on QPSO algorithm for trajectory planning of FFSR general kinematics modeling

Aiming at the optimal trajectory planning problem faced by free floating space robot (FFSR) in capturing non cooperative target (NCT) with unknown dynamic parameters, firstly, based on the unique intrinsic characteristics of FFSR in microgravity environment, a general FFSR kinematic model based on generalized velocity variables and an NCT dynamic model based on quaternion method are established. Secondly, the optimal criterion of FFSR trajectory planning and the parametric modeling method of FFSR manipulator joint trajectory based on sinusoidal function are studied; Finally, a QPSO algorithm for FFSR trajectory planning based on the optimal comprehensive index is proposed

Multiobjective Optimization and Weight Selection Method for Heavy Haul Trains Trajectory

Energy-saving, punctuality and smoothness are difficult to achieve in the operation of heavy haul train. This paper proposes a multi-objective method for speed curve optimization. Firstly, a quadratic programming optimization model is established, using train kinetic energy and train force as independent variables and several goals of energy conservation, smoothness, and target speed tracking. Under the supplied weight vector, the model can realize the ideal speed curve under unbounded time. Secondly, in order to address the demand for punctuality, this paper develops a weight selection algorithm to optimal weight vector for any given trip time. Finally, a time-bounded multi-objective speed curve optimization model is proposed, which achieves energy conservation, punctuality and smoothness train operation. The simulation indicates that the proposed algorithm outperforms human driving in multi-objectives. And the designed time bounded weight selection algorithm is more efficient than the conventional linear approaching weight search method.

Automatic planning method of seawater navigation trajectory based on AIS big data

Automatic planning method of seawater navigation trajectory based on AIS big data

Method of movement control of unmanned vehicles according to specified trajectory of movement and safety considetations

Abstract: The article is aimed to the possible trajectory of unmanned aerial vehicles in built- up agglomerations. It points out problems relating to safety, selection of flight corridors and description of the method of movement control of unmanned aerial vehicle according to specified trajectory of its movement. Design proposal of UAV reference trajectory memory block and methods of solving safety and reliability in built-up agglomerations are presented in the article Keywords: Aviation unmanned system; Built-up agglomerations; Safety; Pilot operator; Flight route; Control method; Established trajectory

An accurate full-dimensional H4O potential energy surface and dynamics of an exchange reaction.

H2O and H2 are ubiquitous in the universe and their collisions play a crucial role in astrophysical processes. The reaction between the two also provides a prototype for understanding dynamics through four-center transition states. In this work, we adopted a strategy of combing two ab initio methods, CCSD(T)-F12a/AVTZ and MRCI-F12 + Qrot/AVTZ, to provide a balanced description for all regions of the configuration space, including one hydrogen exchange channel and two dissociation channels, namely H2 + H2O, H + H + H2O, and H + OH + H2. About 40 500 points were sampled to cover all dynamically relevant space, and the permutation invariant polynomial-neural network (PIP-NN) method was employed to develop a high-precision full-dimensional potential energy surface (PES), with a total fitting error of 0.055 kcal mol-1. Using a quasi-classical trajectory (QCT) method, the reaction dynamics and mode specificity of the hydrogen exchange channel were studied on the PES. It has been found that the stretching mode of H2, the bending, the symmetric stretching, the asymmetric stretching mode of H2O, and the translational mode can all promote reactivity. The strongest promotion effect comes from the H-H stretching mode. The Sudden Vector Projection (SVP) model was applied to predict mode specificity effects and rationalize the product energy partitioning. In both cases, the QCT and SVP results are generally consistent with each other. Furthermore, the hydrogen exchange channel was found to be dominated by sideways scattering.

Sequential Error Disentanglement of Three-Phase Current Sensor for AC Machine in Standstill Conditions

This article proposes a compensation method for gain and offset errors in the current sensing of three-phase AC machine drives with three current sensor measurements during exact or close to standstill conditions. Errors are treated sequentially based on the elliptical trajectory method, a mathematical manipulation by demodulating faulted time-varying <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d, q</i> currents using the machine position. As three current sensors are used, a correction factor through measured neutral current is proposed such that the impact of machine resistance deviation and inverter non-idealities are minimized. The method does not incorporate any additional hardware, making it low-cost and straightforward in its implementation. It is proposed as a tool for initial commissioning before the machine runs. It is robust to rotor position perturbations and does not need a mechanical lock for compensation in standstill conditions. The effectiveness of the suggested approach is shown by analysis, modelling, and experimental findings acquired from a hardware prototype by mimicking the actual use of high-precision mechatronics.

Dynamics of C&lt;sup&gt;+&lt;/sup&gt; + H&lt;sub&gt;2&lt;/sub&gt; reaction based on a new potential energy surface

The multi-reference interaction method is explicitly dependent on the electron-electron distance, and ACVQZ basis set is used in the &lt;i&gt;ab initio&lt;/i&gt; calculation. The potential energy surface (PES) is fitted by using the permutation invariant polynomial neural network method based on 18222 &lt;i&gt;ab initio&lt;/i&gt; points. In addition, the topographical features of the PES are compared with available theoretical and experimental data. The results indicate that the present PES is more accurate and can be applied to any type of dynamic study. In order to validate the PES, the dynamic study of the C&lt;sup&gt;+&lt;/sup&gt; + H&lt;sub&gt;2&lt;/sub&gt; → H + CH&lt;sup&gt;+&lt;/sup&gt; reaction is carried out by using the quasi-classical trajectory method in a collision energy range of 0.4–1.0 eV. The integral cross sections and differential cross sections are calculated and compared with previous theoretical studies. For the integral cross section, the present results are, in general, in good agreement with previous theoretical studies, both of which increase with collision energy increasing. The forward and backward symmetric differential cross sections indicate that the “complex-forming” mechanism plays a dominant role in the reaction.

Broadening and shifting of the carbon monoxide rotational lines in a wide temperature range: calculations in the framework of the classical impact theory for CO-He

The classical impact theory of Gordon is used to calculate half-widths and shifts of spectral lines of the pure rotational band of 12C16O isotopologue broadened by He. Two rotational transitions are examined: J=0-&amp;gt; J=1 and J=1-&amp;gt; J=2 in the wide temperature range from 1.3 to 600 K. The main purpose of this work is the study of the validity limits of classical impact theory at low temperatures. Dynamical calculations were performed on the accurate CO-He ab initio potential energy surface. The results of calculations are in good agreement with experimental data with the exception of very low temperatures. The contributions of collisions of different types (elastic, inelastic, quasibound complexes) are clearly examined in the classical picture frame. It is shown that the mismatches between classical theory and measurements are caused by the too high contribution of elastic collisions into broadening and shift in the present variant of theoretical model. The idea in the spirit of the Weisskopf theory is applied to try to diminish this contribution. The classical results are also compared with the results of fully quantum close coupling calculations made with using four CO-He interaction potentials. The roots of discrepancies at low temperatures as well as the virtues and the shortcomings of a classical approach are discussed. Keywords: collisional line broadening and shift, intermolecular interactions, classical impact theory, classical trajectory method, quasibound complexes.

Multivariate Combined Collision Detection for Multi-Unmanned Aircraft Systems

To mitigate the problem of multiple unmanned aircraft systems (MUAS) conflicts at low altitude and ensure the operational safety, this paper proposes a Multivariate Combined Conflict Detection (MCCD) method for MUAS by combining the characteristics of nominal and probabilistic trajectory method. Firstly, the structural framework of the MCCD method is established based on the concept of potential conflict pool, and a detection pattern is derived for MUAS. Secondly, a three-dimensional conflict fast detection model is constructed by velocity obstacle methods, which can rapidly detect potential conflict risks. Thirdly, a trajectory prediction model is constructed by using bidirectional long-short term memory (Bi-LSTM) network, and then a probability-based conflict detection model can be obtained by the expected value and error distribution of trajectory prediction, which can accurately calculate the collision probability of UAS pair. By fully integrating the above models, the fast and accurate detection of MUAS conflicts is achieved. Finally, multiple conflicting trajectories are constructed to analyze the effectiveness of MCCD method, the tests indicate that the average detection time of the proposed method is less than 15ms, the false positive rate is less than 0.01 and the false negative rate is less than 0.0035. The results show that the MCCD has the accuracy advantage and better real-time performance for MUAS conflict detection compared to the method of velocity trend extrapolation, single probabilistic conflict detection and probabilistic neural network.

Rate constants and molecular recombination pathways of oxygen from quasi-classical trajectory simulations of theO3system

• Investigation of recombination mechanisms using quasi-classical trajectory method. • Direct collisions are more effective for recombination. • Indirect recombinations proceed through orbiting pairs. • Recombination products result in strong non-Boltzmann internal energy distributions. • Recombination products exhibit large vibrational and low rotational quantum numbers. A lack of understanding of the dynamics of molecular recombination has led to the development of a large number of recombination models and methods to quantify recombination rate constants, each with their own set of assumptions and ranges of applicability. This work aims to unravel the complex dynamics behind the recombination of atomic oxygen to molecular oxygen using the quasi-classical trajectory method for the O 3 system. Recombination pathways considered include a single-step “direct” reaction, and a two-step mechanism that involves the formation of a long-lived intermediate which is stabilized through collision with a third body. The latter is further classified as Lindemann or Chaperon recombination pathways depending on the identity of the intermediate and the final product. The classical versions of all three mechanisms are explored in detail for the O 3 system. A time-lag parameter is introduced to quantify the time interval between the intermediate formation and third-body stabilization steps, and the direct collisions are treated as a limiting case when the time lag is zero. It is found that the recombination probabilities reduce as the time-lag is increased. Direct recombination events are dominated by head-on collisions, while the two step recombination events are characterized by a combination of glancing and head-on collisions. The resulting recombination products follow a strongly non-Boltzmann distribution. Recombination rate coefficients are computed through a novel rate coefficient formula that takes into consideration the Poisson distribution in time of third body stabilizing collisions with the orbiting pair characterized by finite lifetimes (on the order of picoseconds) that lead to recombination. Good agreement is obtained with recombination rates computed from detailed balance based on known dissociation rate coefficients. This approach thus enables the direct calculation of recombination rate coefficients at low temperatures, without the need for dissociation rate coefficients and detailed balance.

Product vibrational state distributions of F+CH3OH reaction on full-dimensional accurate potential energy surface

The hydrogen abstraction reaction of methanol with fluorine atoms can produce HF and CH3O or CH2OH radicals, which are important in the environment, combustion, radiation, and interstellar chemistry. In this work, the dynamics of this typical reaction is investigated by the quasi-classical trajectory method based on a recently developed globally accurate full-dimensional potential energy surface. Particularly, the vibrational state distributions of the polyatomic products CH3O and CH2OH are determined by using the normal mode analysis method. It is found that CH3O and CH2OH are dominantly populated in the ground state when the reactants are at the ground ro-vibrational state. The OH stretching mode, torsional mode, H2CO out-of-plane bending mode and their combination bands in the CH2OH product can be effectively excited once the OH stretching mode of the reactant CH3OH is excited to the first vibrationally excited state. Most of the available energy flows into the HF vibrational energy and the translational energy in both channels, while the radical products, CH3O or CH2OH, receive a small amount of energy, consistent with experiment, which is an indication of its spectator nature.

An accurate NH2(X2A'') CHIPR potential energy surface via extrapolation to the complete basis set limit and dynamics of the N(2D) + H2(X1Σ+g) reaction.

The amidogen radical (NH2) and its associated N(2D) + H2(X1Σ+g) → H(2S) + NH(X3Σ-) reaction have great significance in interstellar chemistry and the accurate potential energy surface (PES) is the basis for studying them. We report a new and accurate PES for the ground state NH2(X2A'') using the combined-hyperbolic-inverse-power-representation methodology based on 7970 ab initio energy points computed at the Davidson-corrected internally contracted multireference configuration interaction level of theory. Both aug-cc-pVTZ and aug-cc-pVQZ basis sets have been employed to extrapolate the energies to the complete basis set limit. The analytical PES reproduces well with the ab initio energy points with a root mean square deviation of 55.7 cm-1. The topographical features of the analytical PES are examined in detail and agree well with the previous theoretical results. The integral cross sections and rate constants of the N(2D) + H2(X1Σ+g) → H(2S) + NH(X3Σ-) reaction are obtained using the quasi-classical trajectory method and the time-dependent wave packet method and then compared with the available theoretical and experimental values.

Effect of Reactant's Rotational Excitation on Stereodynamic Properties of C+Sh(V=0, J=0-40)→Cs+H Reaction Investigated with Quasi Classical Trajectory Method

Effect of Reactant's Rotational Excitation on Stereodynamic Properties of C+Sh(V=0, J=0-40)→Cs+H Reaction Investigated with Quasi Classical Trajectory Method

Chemical Composition Characteristics and Source Apportionment of PM2.5 in Ceramic Industrial Base during Winter

The national architectural ceramic industrial center in east China is suffering from serious ambient fine particle pollution. The study reported herein describes an effort to ascertain the degree and sources of the PM2.5 collected in a ceramic industrial base during winter. The major chemical components in PM2.5 were analyzed, including carbonaceous aerosols, water-soluble ions, and inorganic elements. The chemical mass balance (CMB) model, backward trajectory method and potential source contribution function model, etc. were used to track and identify possible sources and contributions in the formation of the PM2.5. The results showed that the average PM2.5 concentration during sampling period was 134 ± 74.7 µg m–3, which exceeding World Health Organization (WHO) Air Quality Guidelines levels. The dominant components in the PM2.5 at this sampling site were found to be secondary ions (sulfate and nitrate) and carbon fractions. Water-soluble ions and total carbon contributed about 48.7% and 13.9% of the PM2.5 mass, respectively. In addition, the SO42–/NO3– ratio in the ambient PM2.5 during the sampling period was 1.16, indicating that it was the result of primarily emissions from stationary sources. Furthermore, source apportionment using the CMB model indicated that a ceramic industry source was the main contributor to the PM2.5 mass, which accounted for about 27.9%, and this was followed by secondary formation dust sources, and gasoline/diesel vehicle exhaust emissions and motor vehicle non-exhaust emissions. Based on the backward trajectory analysis and potential source apportionment, it was found that PM2.5 regional transmission existed, but it originated primarily from local sources and surrounding areas. Hence, this study provided a scientific basis for identifying the sources of PM2.5 pollution during a typical pollution period and provided important input for PM2.5 control strategies in a typical industrial area.