Trajectory Simulation Results Research Articles

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.

Surface Charging Affecting Metal Particle Lifting Behaviors Around Epoxy Spacer of HVDC GIL/GIS

In this article, the mechanisms of surface charging and surface modification of epoxy spacer affecting the lifting voltage and the motion trajectory of spherical metal particles in a downsized dc gas insulated transmission line (GIL) are investigated by simulations and experiments. Results show that the lifting voltage can be predicted with much accuracy by calculating the electric field distribution under the capacitive condition. Prestressing leads to a 27% decrease of lifting voltage, which is traceable to that surface charging making a major contribution to the enhancement of electric field force. Direct fluorination is proven as an effective modification method to improve the insulation performance of epoxy spacer again. The lifting inclination is significantly inhibited after treatment because of less surface charge accumulation and more rationalized electric field distribution. The trajectory simulation results indicate that more serious surface charging can activate more metal particles to lift up and drive them to more collisions. The lifting probability and velocity of metal particles around the epoxy spacer are markedly decreased by fluorination, which is a promising treatment for dc GIL/gas insulated switchgear (GIS) application.

A strategy on generating structured plateau surface by the sinusoidal oscillatory lapping of the grinding wheel with the phyllotactic pattern of abrasive grains

The structured plateau surface can reduce the contact friction force on workpiece surfaces based on the kinematics principle of superfinishing considering the phyllotaxis theory of biology. In this paper, the strategy on lapping structured platform surface over cyclindrical component has been proposed with the help of the sinusoidal movement of ordered grinding wheel. In order to achieve this strategy, the lapping device has been first designed and manufactured, and the design theory of ordered grinding wheel is given. The ordered grinding wheel is manufactured, and then the equation of the lapping trajectory of abrasive particles is established while considering processing parameters. The kinematic conditions of generating structured plateau surface is discussed, and the geometric generating mechanism of the plateau surface is analyzed by means of the trajectory simulation results. Finally the problems related to the lapping process and the generating mechanism of the plateau surface are analyzed and discussed based on the experimental investigation results. The research results show that the sinusoidal oscillation lapping of the order grinding wheels which are arranged according to whorls, staggered whorls and spiral pattern, can generate different structured plateau surface. The geometry shape of the plateau surface and its consistency depend on the configuration form and parameters of the grinding wheel.

New Cadanav Methodology for Rock Fall Hazard Zoning Based on 3D Trajectory Modelling

Most rock fall hazard zoning methodologies are currently based on trajectory modelling, usually performed along 2D slope profiles. For many topographic configurations, this approach cannot provide a realistic description of the way rock fall trajectories and, ultimately, hazard are spatially distributed all over a slope. This paper presents a new methodology for rock fall hazard zoning, directly applicable to 3D topographies, starting from 3D trajectory simulation results. The procedure is an extension of the Cadanav methodology introduced for hazard zoning along 2D slope profiles. As such, it is fully quantitative and attempts at reducing as much as possible uncertainties and subjective elements affecting current methods for rock fall hazard analysis and zoning. It is also among the first to introduce a “fully-coupled” rock fall intensity-frequency approach. Hazard is estimated by means of “hazard curves”, described at each point of the slope by rock fall intensity-return period couples. These curves may be superimposed on any intensity-return period diagram prescribed in national or regional land use planning regulations, in order to determine which hazardous condition prevails at each point of the slope. The application of the new Cadanav methodology is illustrated for both a theoretical case of simple topography underlying a linear cliff and a real configuration involving a complex topography, characterised by strong three-dimensional features affecting the paths of the blocks. For all topographic models, results obtained for several scenarios involving either localised or diffuse source areas proved that the methodology performs extremely well, providing objective and reproducible results based on a rigorous combination of rock fall energy and return period. Additional tests and real case studies are currently under investigation, for strengthening even further the validation of the approach and extend its applicability to even more complex rock fall scenarios.

Design, Analysis, and Control of a Two-Dimensional Vibration Device for Vibration-Assisted Micromilling

In this article, a new two-dimensional piezoelectric actuator driven vibration stage is proposed and prototyped. A double parallel four-bar linkage structure with double-layer flexible hinges is designed to guide the motion and reduce the displacement coupling effect between the two directions. The compliance modeling and dynamic analysis are carried out based on the matrix method and Lagrangian principle, and the results are verified by the finite-element analysis. A closed-loop control system is developed and proposed based on the LabVIEW program consisting of a data acquisition device and capacitive sensors. Machining experiments have been carried out to evaluate the performance of the vibration stage and the results show good agreement with the tooltip trajectory simulation results, which demonstrates the feasibility and effectiveness of the vibration stage for vibration-assisted micromilling.

A multi-objective trajectory planning method based on the improved immune clonal selection algorithm

In this paper, a multi-objective trajectory planning method based on an improved immune clonal selection algorithm is proposed. On the basis of the inverse kinematic analysis and dynamic model of the 6-UPU parallel assembly platform (PAP), the motion trajectory of the mobile platform is planned in Cartesian space with a quintic B-spline curve. Three important technical indexes, i.e. assembly efficiency, production cost and motion stationarity, are selected to evaluate the performance of planned trajectory. Correspondingly, three ideal objective functions which can represent the aforementioned technical indicators, namely the functions respectively of the total motion time, of the energy consumed in the process of motion and of the maximum absolute value of actuator's jerk, are defined to establish the multi-objective model for trajectory optimization. Then an improved immune clonal selection algorithm (IICSA) is developed to solve the optimization problem. Results of trajectory simulation confirm that the demands of assembly task can be met. Thus, the proposed method is effective and universal and it has the potential to be referenced or applied directly to other types of manipulators.

Influence of the Earth Rotation on Trajectory of a Returnable Hypersonic Cruise Vehicle

It is of high difficulty for a hypersonic vehicle to implement a hypersonic cruise flight and return to a scheduled airport without power. Accuracy of mission simulation and analysis is more crucial at this time. Under this circumstance, it is meaningful to discuss whether the earth rotation should be considered in the dynamic model and trajectory design. In this research, the dynamic equations in which the earth rotation is taken into consideration are derived for a hypersonic cruise vehicle. The direct shooting method is utilized for parameterization and discretization of the trajectory, so that the trajectory can be analyzed and simulated through numerical integration. Then, two groups of trajectory simulation results are presented. In each group, the only difference between the two trajectories is that whether the earth rotation is involved, and the two trajectories are compared with each other. For a returnable hypersonic cruise vehicle which returns to the ground without power, whether to involve the earth rotation in the dynamic model is discussed on the basis of the numerical results, and relevant suggestions are given for reference.

Low-voltage SEM contrasts of steel surface studied by observations and electron trajectory simulations for GEMINI lens system.

Scanning electron microscopy (SEM) is a powerful tool for observing the surface of materials. Modern SEM systems have multiple detectors with different geometries. Consequently, the SEM image contrast depends on the instrument and experimental conditions even for the same sample. Understanding the SEM imaging mechanism is necessary to clarify SEM contrast. In this paper, low-voltage (LV)-SEM image contrast is investigated by comparing LV-SEM images and electron trajectory simulation results. Surface observations of oxides on a steel surface, positive charging contrast and topographic contrast in the image systematically changed with the working distance (WD). The electron trajectory simulation revealed the sharing of emitted electrons by the in-lens and Everhart-Thornley detectors, and systematic changes in the electron sharing caused by changes in WD. The image contrast was reasonably explained by the kinetic energy and take-off angle (acceptance plots) of the detected electrons derived by the electron trajectory simulations. This approach is essential to understanding the SEM image contrast obtained by SEM systems with multiple detectors. Thorough image simulations based on acceptance plots are required in future work.

6DOF Missile Trajectory Simulation Using Reusable Frame and Models

A reusable frame and appropriate models are designed for six degree of freedom (6DOF) missile trajectory simulation. The importance of establishing trajectory simulation model in missile design and experiment is described at first. Guidance Navigation and Control (GNC) loop as the core component in missile is discussed with emphasis on performance limitations. Design Patterns (DP) in software engineering are utilized to accomplish module partition. Reusable design is conducted in a two-step process: frame design and models design. This method can improve design productivity and shorten design circle as its reusable frame and relevant models can applied to many kinds of missiles without major revisions. An air defense scenario is designed to validate the proposed model frame. The 6DOF trajectory simulation results are obtained. Results show that the method offers an effective and practical way to design parameters and evaluate performance of missile.

Experimental study on fabricating spirals microelectrode and micro-cutting tools by low speed wire electrical discharge turning

This study is focused on the fabrication of spirals microelectrode and spirals micro-cutting tools by using low speed wire electrical discharge turning (LS-WEDT). Firstly, the concept, movement relationship and machining principle of LS-WEDT process are analyzed, respectively. Then, the effects of new parameter of rotating speed on surface roughness, surface microstructure, elements change and material removal rate in LS-WEDT are evaluated in detail. Experimental results demonstrate that LS-WEDTed surface is significantly improved, micro-voids become more and smaller but foreign element contents increase with the increasing of rotating speed. More importantly, the space flexibility, negligible electrode wear and multiple cutting strategy of the LS-WEDT make it competent in fabricating micro tools with complex structure and high accuracy. Consequently, spirals microelectrode with high accuracy can be obtained for spiral pitch standard deviation of 2.57 and thread angle standard deviation of 0.96, and pitch length and thread numbers can be flexibly controlled in LS-WEDT. Additionally, the three spirals taper micro-cutting tool is fabricated by LS- WEDT based on the shape and cutting edge trajectory simulation results. Furthermore, the three spirals micro-cutting tool with average diameter of 175.77 μm and length of 1300 μm is firstly and successfully manufactured by LS-WEDT method.

Aerothermochemical Nonequilibrium Modeling for Oxygen Flows

The results from a set of vibrational nonequilibrium models with a range of fidelity are compared to the recent experimental data for several postnormal shock test cases. The present work focuses solely on oxygen flows with an emphasis on implementing a new set of accurate state-specific rate coefficients for collisions. The two-temperature model is presented as the computationally efficient, lower-fidelity approach in this work. The two-temperature model is driven by the relaxation parameters based on the Millikan–White empirical equation as well as on the parameters resulting from a master equation simulation that employs the database of state-resolved rate coefficients. The full state-to-state master equation approach is presented as the higher-fidelity modeling approach. The system uses recently available results of trajectory simulations for state-specific transition rate coefficients The system uses transition rates from the forced harmonic oscillator model. The test case comparison shows that the state-resolved modeling approach is more suitable for describing the vibrational temperature and chemically nonequilibrium zone behind the shock wave. It is shown that the capability of the state-resolved model to capture non-Boltzmann distribution is critical for accurately modeling the vibrational relaxation and dissociation phase.

Characterization of Chemical Composition in PM2.5 in Beijing before, during, and after a Large-Scale International Event

ABSTRACTTo commemorate the 70th anniversary of the victory of the Chinese people's Anti-Japanese War and the World Anti-Fascist War, an international parade was held in Beijing in September 2015. In order to ensure satisfactory air quality during this event, a phased emission control measures were taken in Beijing and its surrounding provinces. The 24-h PM2.5 samples were collected in Beijing from August 1 to September 15, 2015 covering the period before, during and after this large-scale event. The observed PM2.5 data, meteorological data, emission reduction measures, and air mass trajectory simulation results were systematically analyzed to understand the pollution characteristics and chemical compositions of PM2.5 in Beijing. The results indicated that PM2.5 concentration during the two emission control phases was reduced by 61.7% comparing to the non-control period, but the regional transport of pollutants and meteorological conditions had a more prominent impact on PM2.5 than emission reduction during phase 2. The secondary water-soluble ions including SO42–, NO3–, and NH4+ were found as the main ions present in PM2.5. During the entire emission control period, organic carbon (OC) and elemental carbon (EC) mass concentrations were decreased by 53.1% and 57.9%. A PM2.5 mass balance was analyzed, and it was found that the organic matter accounted for 29.3, 37.6 and 28.5% of the PM2.5 mass before, during and after the emission control, while the contribution of mobile sources to PM2.5 was relatively outstanding after a series of emission control measures.

Robust gain-scheduled autopilot design for spin-stabilized projectiles with a course-correction fuze

This article explores the design of a pitch/yaw axis load factor autopilot for a class of 155-mm spin-stabilized ammunition which incorporates a novel nose-positioned course correction fuze system used for trajectory correction. The projectile full nonlinear model is discussed and a procedure for obtaining the system q-LPV model necessary for control synthesis is exposed. Important properties relevant to axis cross-coupling, internal modes and stability properties specific to this kind of system are also highlighted. A comparison of full- and reduced-order mixed-sensitivity H∞ linear compensators with an additional model following constraint for the design of the projectile autopilot is presented. Robust stability with respect to aerodynamic and actuator/sensor modeling uncertainties is verified via standard μ-analysis tools throughout the projectile flight envelope. Nonlinear 7-DoF trajectory simulation results are finally presented for a single or dual control surface actuator configuration.

패러포일 투하 시스템의 궤적 추종 제어기의 설계

본 논문은 패러포일 투하 시스템을 설계하고 분석하는데 있다. 패러포일 시스템의 6-자유도(6-DOF) 모델을 새우고, 비선형 모델 예측 제어와 PID 제어 방법이 펄럭 편 요각을 제어하기 위해 각각 적용되었다. 펄럭 편 요각의 오버슈트 시간 및 세팅 시간의 결과를 비교하면서 PID제어 방법을 사용하는 것으로부터 펄럭 편 요각이 좀 더 안정화 되는 것을 확인하였다. 그런 다음 MATLAB에 의해 수행된 궤적 추종 효과의 시뮬레이션 결과에 의해 궤적 추종 제어기가 설계되었다. 패러포일 궤적의 측 방향 오차가 그것의 측 방향 편차 제어 방법에 의해 제거 될 수 있었다. 참고로 측 방향 편차는 현재 경로계획의 보간법에 의해 얻어졌다. 그리고 설계된 궤적을 사용하면서, 풍 외란을 추가하는 것으로부터 궤적 추종 시스템이 시뮬레이션 되었다. 시뮬레이션 결과는 풍외란이 PID로 제어되는 펄럭 편 요각 변화에 의해 제거됨으로써 설계된 궤적에 아주 만족하였다. In this paper, parafoil airdrop system has been designed and analyzed. 6-degrees of freedom (6-DOF) model of the parafoil system is set up. Nonlinear model predictive control (NMPC) and Proportion integration differentiation (PID) methods were separately applied to adjust the flap yaw angle. Compared the results of setting time and overshoot time of yaw angle, it is found that the of yaw angle is more stable by using PID method. Then, trajectory following controller was designed based on the simulation results of trajectory following effects, which was carried out by using MATLAB. The lateral offset error of parafoil trajectory can be eliminated by its lateral deviation control. The later offset deviation reference was obtained by the interpolation of the current planning path. Moreover, using the designed trajectory, the trajectory following system was simulated by adding the wind disturbances. It is found that the simulation result is highly agreed with the designed trajectory, which means that wind disturbances have been eliminated with the change of yaw angle controlled by PID method.

New Cadanav methodology for quantitative rock fall hazard assessment and zoning at the local scale

Rock fall hazard zoning is a challenging yet necessary task to be accomplished for planning an appropriate land use in mountainous areas. Methodologies currently adopted for elaborating zoning maps do not provide satisfactory results though, due to uncertainties and related assumptions characterising hazard assessment. The new Cadanav methodology, presented in this paper, aims at improving quantitative hazard assessment and zoning at the local scale, by reducing uncertainties mainly related to the technique for combining rock fall intensity and frequency of occurrence. Starting from available information on rock fall failure frequency and trajectory simulation results, the procedure merges in a strict way temporal frequency, probability of reach and energy data and evaluates the hazard degree by means of “hazard curves”. These curves are described at each point of the slope by a series of energy–return period couples representing the hazardous conditions which may possibly affect that location. The new Cadanav methodology is here detailed and compared to its original version. Hazard zoning results are illustrated along two different 2D slope profiles, for linear homogeneous cliff configurations, and according to the Swiss intensity–frequency diagram for rock fall hazard zoning. However, the procedure can be easily used with any other intensity–frequency diagram prescribed in national guidelines and, additionally, extended to problems involving 3D topographies.

Robust optimal trajectory design by integrating genetic algorithm with min-max method

A robust optimal trajectory design method is proposed in this paper. Genetic Algorithm (GA) is employed to optimize the whole trajectory to improve the terminal attack performance. To enhance the robustness of the trajectory to disturbances, the min-max method is integrated into the GA optimization process. The proposed approach is carefully illustrated with the robust optimization design of the trajectory for a portable short-range top-attack (PSRTA) missile. The H∞ robust gain-scheduled technique is used to design the attitude tracking autopilot to facilitate the trajectory design. The damp feedback loop of the weakly-damped missile body is innovatively treated as the Linear Parameter Varying system (the controlled plant), which is good for practical use. The proposed robust optimal trajectory design method and the H∞ robust gain-scheduled attitude tracking autopilot are demonstrated to be effective from the whole trajectory simulation results of the PSRTA missile, which also exhibit high applicability for practical engineering problems.

Trajectory Prediction of Spin-Stabilized Projectiles with a Liquid Payload

Abstract : Payloads that behave like a liquid are carried on board some projectile configurations, and it is well established that the internal motion of a liquid payload can induce destabilizing moments on the projectile. This report creates a method to include the effect of a liquid payload in the flight dynamic equations of motion, enabling trajectory simulations of projectiles with liquid payloads. To include this effect, liquid payload moments are added to the applied loads on the projectile. These loads are computed by solving the linearized Navier-Stokes equations for a projectile undergoing coning motion. To highlight the methodology, trajectory simulation results are provided for an example projectile with different liquid payload configurations possessing stable behavior while one exhibits catastrophic flight instability.

Computer simulation of electron and ion trajectories in electron-impact ion sources of a quadrupole mass spectrometer

Electron and ion trajectories have been simulated in electron-impact ion sources of a quadrupole mass spectrometer. The ion trajectories in the conventional Nier-type ion source show poor extraction efficiency of the generated ions into the quadrupole. Based on the electron and ion trajectory simulation results, the Nier-type ion source has been modified to improve the ion extraction efficiency. The modified ion source exhibits much better ion extraction efficiency and smaller kinetic energy spread than the Nier-type ion source.

전투기 외부 연료 탱크의 종방향 정안정성 및 투하 궤적 해석

The present work is to analyze the longitudinal static stability and the drop trajectory of fighter aircraft's external fuel tank, of which horizontal fin is modified as the 20% scale down size compared with the original one. The analytical results to the pitching stability of external fuel tank using a thin airfoil's aerodynamic force data show the corresponding tendency to results of wind tunnel experiment. Results of trajectory simulation by the 6 degree of freedom equations of motion, comparing with drop trajectories of wind tunnel experiment, are shown that aircraft's attitude affects strongly on horizontal movement but not on the vertical movement. Those results give the reliability to aircraft safety when the external fuel tank with the 20% reduced horizontal fins is released from aircraft based on the flight manual.

An Assessment of Meteorological Effects on Air Quality in Windsor, Ontario, Canada ― Sensitivity to Temporal Modeling Resolution

The HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model was used to study air quality in the City of Windsor (42.16° N, 82.58° W), Ontario, Canada. Two-day back trajectory simulations were conducted for the year of 2003 to investigate the regional transport of air pollutants. Trajectories were then characterized by air mass path direction and regions traversed as dominant factors in regional transport of air pollutants, to assess meteorological effects on air quality in Windsor and provide initial identification of potential upwind pollution source regions. Statistical analysis was conducted to study whether the trajectory simulation results are sensitive to temporal modeling resolution of one, two, three and six simulations per week. It was found that HYSPLIT backward trajectory modeling can provide good quality and consistent results with a temporal resolution of two or three runs per week, comparable to a resolution of six runs per week. The HYSPLIT backward trajectory modeling and analysis methods presented can identify potential source regions of transboundary pollutants at practical temporal modeling resolutions. This is useful to communities and policy-makers developing public health policy.