scholarly journals Modeling and Analysis of a Generic Internal Cargo Airdrop System for a Tandem Helicopter

2021 ◽  
Vol 11 (11) ◽  
pp. 5109
Author(s):  
Guozhi Li ◽  
Yihua Cao ◽  
Maosheng Wang
Keyword(s):  
Nonlinear Dynamics ◽  
Flight Dynamics ◽  
Simulation Method ◽  
Rotational Dynamics ◽  
Discretization Method ◽  
Modeling And Analysis ◽  
Flight Velocity ◽  
Vector Mechanics ◽  
Good Attitude

This article describes the results of modeling and analysis of a generic internal cargo system using a discretization method of the vector mechanics. The model can be easily incorporated into a tandem helicopter model and is intended for use of simulation and investigating the problems of flight dynamics, control, etc., both in flight operation loading a cargo and flight operation in the process of airdrops. The model is derived by considering the main descriptions of the cargo, including the linear and rotational dynamics, the kinematics, and the forces and moments acting on the helicopter. A simulation method embedded with a numerical trim algorithm is developed for the complete coupling helicopter/cargo nonlinear dynamics system. The simulation application of the model is illustrated, including the case of flight operation loading a cargo by considering three mass configurations of 3000, 4500, and 6000 kg, and the case of flight operation in the process of airdrops at velocities of 0, 40, 80, 120, and 160 knots. Stabilities of the helicopter in the process of airdrops are also analyzed. The major conclusions drawn are: (i) the tandem helicopter has a good attitude maintaining ability in the whole flight velocity envelope when it conducts a flight operation loading a cargo; (ii) in the process of airdrops, the increase in flight velocity will constantly decrease the helicopter pitching attitude and increases the total airdrop time and decreases the backward moving velocity of the cargo, and helicopter flying at a velocity between 80 and 120 knots might be acceptable; (iii) the stabilities of both the longitudinal and lateral periodic modes are continuing to decrease during the backward movement of the cargo.

Effects of the Gear Tooth Modification on the Nonlinear Dynamics of Gear Transmission System

2010 ◽  
Vol 97-101 ◽  
pp. 2764-2769
Author(s):  
Si Yu Chen ◽  
Jin Yuan Tang ◽  
C.W. Luo
Keyword(s):  
Nonlinear Dynamics ◽  
Gear Tooth ◽  
Simulation Method ◽  
Transmission Error ◽  
Dynamic Responses ◽  
Meshing Stiffness ◽  
Gear Transmission System ◽  
Tooth Modification ◽  
Static Transmission Error ◽  
Misalignment Error

The effects of tooth modification on the nonlinear dynamic behaviors are studied in this paper. Firstly, the static transmission error under load combined with misalignment error and modification are deduced. These effects can be introduced directly in the meshing stiffness and static transmission error models. Then the effect of two different type of tooth modification combined with misalignment error on the dynamic responses are investigated by using numerical simulation method. The numerical results show that the misalignment error has a significant effect on the static transmission error. The tooth crowning modification is generally preferred for absorbing the misalignment error by comparing with the tip and root relief. The tip and root relief can not resolve the vibration problem induced by misalignment error but the crowning modification can reduce the vibration significantly.

scholarly journals Tolerance Modeling and Analysis Considering Form Defects for Spaceborne Array Antenna

2020 ◽  
Vol 10 (8) ◽  
pp. 2840
Author(s):  
Guodong Sa ◽  
Zhenyu Liu ◽  
Chan Qiu ◽  
Jianrong Tan
Keyword(s):  
Tolerance Analysis ◽  
Simulation Method ◽  
Geometric Error ◽  
Array Antenna ◽  
Analysis Method ◽  
Phased Array Antenna ◽  
Modeling And Analysis ◽  
Form Errors ◽  
Assembly Simulation ◽  
Tolerance Modeling

Tolerance analysis is becoming increasingly important for tolerance design and optimization. When dealing with electromechanical products such as the array antenna, the form errors of the assembly must be considered. Traditional tolerance analysis with form errors relies on a double loop process, which is computationally expensive. A new tolerance analysis method is proposed in this paper, which can be achieved by a single loop process. First, a new tolerance modeling method considering form errors was proposed, it can represent the geometric error of a surface feature precisely. Then an effective sampling method was developed by introducing the variance separation method. An assembly simulation method was proposed to determine the final state of the whole assembly. Finally, the tolerance analysis was achieved based on the sufficient sample. The proposed analysis method was applied to an X-band spaceborne active-phased array antenna, numerical simulation results show the effectiveness of the method.

scholarly journals Electric field modeling and analysis of EHV power line using improved calculation method

2018 ◽  
Vol 31 (3) ◽  
pp. 425-445 ◽  
Author(s):  
Rabah Djekidel ◽  
Ahmed Bessedik ◽  
Abdechafik Hadjadj
Keyword(s):  
Electric Field ◽  
Transmission Line ◽  
Power Transmission ◽  
Ground Level ◽  
Simulation Method ◽  
Power Line ◽  
Optimal Position ◽  
Modeling And Analysis ◽  
Maximum Value ◽  
Maximum Electric Field

This paper aims is devoted to modeling and simulation of electric field created by EHV power transmission line of 275 kV using an efficient hybrid methodology, the charge simulation method (CSM) with the Simplex Simulated Annealing (SIMPSA) algorithm in order to find the optimal position and number of fictitious charges used in CSM for an accurate calculation. Various factors that affect the electric field intensity were analyzed; it is found that the influence of the conductor sagging is clearly remarked, the maximum electric field strength at 1 m above the ground level recorded at mid-span point of the power line is 3.09 kV/m, in the proximity of the pylon, the maximum value is significantly reduced to 1.28 kV/m. The configuration type of the transmission line (single or double circuit) and the arrangements of phase conductors on double circuit pylons have a significant effect on the levels of electric field around the transmission line. For a single circuit, the triangular configuration provides the lowest maximum value of electric field. For a double circuit, the inverse phase arrangement (abc-cba) or low-reactance phasing produces the lowest maximum value of electric field. The resulting maximum electric field levels were found below the exposure values set by the ICNIRP and IRPA standards for both occupational and general public. The simulation results of electric field are compared with those obtained from the COMSOL 4.3b Multiphysics software, a fairly good agreement is found.

Software Maintenance of Process Modeling Line Model

2011 ◽  
pp. 272-294
Author(s):  
Zeljka Car
Keyword(s):  
Process Modeling ◽  
Software Maintenance ◽  
Simulation Method ◽  
Process Data ◽  
Modeling And Analysis ◽  
System Maintenance ◽  
Systems Maintenance ◽  
Maintenance Process ◽  
Insight Into

The chapter provides the insight into software maintenance process, its features, actors, activities and results, with the emphasis on the importance and complexity of systems maintenance. The issues related to maintenance modeling, maintenance process evaluation and improvement are addressed. The chapter proposes a method for system maintenance modeling and analysis. Software maintenance process is modeled in terms of queuing network with applied simulation. Method implementation is described by a case study of telecommunication maintenance with the field process data. The case study and the related maintenance activities with data are described in detail. The results of the method application show how the process bottlenecks are formally identified and how new proposals for the improved process design should be analyzed. The chapter emphasizes the importance of a well-defined and balanced process indispensable for efficient maintenance of the large telecommunication software.

scholarly journals Time-Dependent Reliability Modeling and Analysis Method for Mechanics Based on Convex Process

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Lei Wang ◽  
Xiaojun Wang ◽  
Ruixing Wang ◽  
Xiao Chen
Keyword(s):  
Monte Carlo ◽  
Product Life Cycle ◽  
Process Model ◽  
Limit State ◽  
Simulation Method ◽  
Time Dependent ◽  
Structural Safety ◽  
Time Varying ◽  
Modeling And Analysis ◽  
Convex Process

The objective of the present study is to evaluate the time-dependent reliability for dynamic mechanics with insufficient time-varying uncertainty information. In this paper, the nonprobabilistic convex process model, which contains autocorrelation and cross-correlation, is firstly employed for the quantitative assessment of the time-variant uncertainty in structural performance characteristics. By combination of the set-theory method and the regularization treatment, the time-varying properties of structural limit state are determined and a standard convex process with autocorrelation for describing the limit state is formulated. By virtue of the classical first-passage method in random process theory, a new nonprobabilistic measure index of time-dependent reliability is proposed and its solution strategy is mathematically conducted. Furthermore, the Monte-Carlo simulation method is also discussed to illustrate the feasibility and accuracy of the developed approach. Three engineering cases clearly demonstrate that the proposed method may provide a reasonable and more efficient way to estimate structural safety than Monte-Carlo simulations throughout a product life-cycle.

Sign in / Sign up

Export Citation Format

Share Document