scholarly journals Description of a Dynamical Framework to Analyse the Helicopter Tail Rotor

Dynamics ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 171-180
Author(s):  
Salvador Castillo-Rivera ◽  
Maria Tomas-Rodriguez
Keyword(s):  
Software Package ◽  
Degrees Of Freedom ◽  
Dynamic Behaviour ◽  
Mechanical Systems ◽  
Rotor Dynamics ◽  
Rigid Bodies ◽  
External Link ◽  
Complex Behaviour ◽  
Theoretical Approaches ◽  
Ann Arbor

In this work, a tail rotor is modelled with the aid of a multibody software to provide an alternative tool in the field of helicopter research. This advanced application captures the complex behaviour of tail rotor dynamics. The model has been built by using VehicleSim software (Version 1.0, Mechanical Simulation Corporation, Ann Arbor, MI, USA) specialized in modelling mechanical systems composed of rigid bodies. The dynamic behaviour and the control action are embedded in the code. Thereby, VehicleSim does not need an external link to another software package. The rotors are articulated, the tail rotor considers flap and feather degrees of freedom for each of the equispaced blades and their dynamic couplings. Details on the model’s implementation are derived, emphasising the modelling aspects that contribute to the coupled dynamics. The obtained results are contrasted with theoretical approaches and these have displayed to agree with the expected behaviour. This rotorcraft model helps to study the performance of a tail rotor under certain dynamic conditions.

Rigid body refinements in GSAS/EXPGUI

2011 ◽  
Vol 26 (S1) ◽  
pp. S13-S21 ◽  
Author(s):  
Charles H. Lake ◽  
Brian H. Toby
Keyword(s):  
Rigid Body ◽  
Software Package ◽  
Degrees Of Freedom ◽  
Rigid Bodies ◽  
Atomic Motion ◽  
Bond Lengths

Rigid bodies provide a way to simplify the model used in a crystallographic refinement by removing parameters that describe degrees of freedom that are unlikely to change based on chemical experience. The GSAS software package provides a powerful implementation of rigid bodies that allows for refinement of classes of bond lengths, grouping of bodies to further reduce parameterization and where atomic motion can be described from group displacement parameters (TLS) representation. However, use of rigid bodies in GSAS is complex to learn and time-consuming to perform. This paper describes how the rigid body definition process has been simplified and extended through implementation in the EXPGUI interface to GSAS.

scholarly journals Application of software tools for symbolic description and modeling of mechanical systems

2020 ◽  
Author(s):  
A. Banshchikov ◽  
A. Vetrov
Keyword(s):  
Mechanical System ◽  
Software Package ◽  
Equations Of Motion ◽  
Relative Equilibrium ◽  
Mechanical Systems ◽  
Software Tools ◽  
Rigid Bodies ◽  
Symbolic Form ◽  
The Stability ◽  
Lagrange Formalism

The paper presents two software tools (graphical editor and software package). The editor is designed for the formation of a symbolic description of a mechanical system using the Lagrange formalism. A system of the absolutely rigid bodies connected by joints is considered as a mechanical system. The editor is a user interface by which one sets the structure of the interconnection of bodies (system configuration) as well as the geometric and kinematic characteristics for each body of the system. The created structure and the entered data are automatically presented in the form of a text file, which is used as an input file for the software package for modeling mechanical systems in a symbolic form with a computer. The use of these software tools is shown in detail in the example of the analysis of the dynamics of a satellite with a gravitational stabilizer in a circular orbit. For this system, the kinetic energy and force function of an approximate Newtonian gravitational field were obtained, nonlinear and linearized equations of motion were constructed, and the question of the stability of the relative equilibrium position was considered.

scholarly journals Observer-based robust integral of the sign of the error control of class I of underactuated mechanical systems: Theory and real-time experiments

2021 ◽  
pp. 014233122110313
Author(s):  
Afef Hfaiedh ◽  
Ahmed Chemori ◽  
Afef Abdelkrim
Keyword(s):  
Real Time ◽  
Error Control ◽  
Degrees Of Freedom ◽  
Sliding Mode ◽  
Mechanical Systems ◽  
Class I ◽  
Control Input ◽  
Underactuated Mechanical Systems ◽  
Control Scheme ◽  
And Performance

In this paper, the control problem of a class I of underactuated mechanical systems (UMSs) is addressed. The considered class includes nonlinear UMSs with two degrees of freedom and one control input. Firstly, we propose the design of a robust integral of the sign of the error (RISE) control law, adequate for this special class. Based on a change of coordinates, the dynamics is transformed into a strict-feedback (SF) form. A Lyapunov-based technique is then employed to prove the asymptotic stability of the resulting closed-loop system. Numerical simulation results show the robustness and performance of the original RISE toward parametric uncertainties and disturbance rejection. A comparative study with a conventional sliding mode control reveals a significant robustness improvement with the proposed original RISE controller. However, in real-time experiments, the amplification of the measurement noise is a major problem. It has an impact on the behaviour of the motor and reduces the performance of the system. To deal with this issue, we propose to estimate the velocity using the robust Levant differentiator instead of the numerical derivative. Real-time experiments were performed on the testbed of the inertia wheel inverted pendulum to demonstrate the relevance of the proposed observer-based RISE control scheme. The obtained real-time experimental results and the obtained evaluation indices show clearly a better performance of the proposed observer-based RISE approach compared to the sliding mode and the original RISE controllers.

Modeling of Mechanical Systems Using Rigid Bodies and Transmission Line Joints

1999 ◽  
Vol 121 (4) ◽  
pp. 606-611 ◽  
Author(s):  
Petter Krus
Keyword(s):  
Transmission Line ◽  
Hydraulic System ◽  
Large Scale ◽  
Mechanical Systems ◽  
Rigid Bodies ◽  
Large Scale Systems ◽  
Distributed Parameters ◽  
Transmission Line Modeling ◽  
Integration Algorithms ◽  
Transmission Line Models

Dynamic simulation of systems, where the differential equations of the system are solved numerically, is a very important tool for analysis of the detailed behavior of a system. The main problem when dealing with large complex systems is that most simulation packages rely on centralized integration algorithms. For large scale systems, however, it is an advantage if the system can be partitioned in such a way that the parts can be evaluated with only a minimum of interaction. Using transmission line models, with distributed parameters, physically motivated pure time delays are introduced in the communication between components. These models can be used to represent both lines in a hydraulic system and springs in mechanical systems. As a result, components and subsystems can be simulated more independently of each other. In this paper it is shown how flexible joints based on transmission line modeling (TLM) with distributed parameters can be used to simplify modeling of large mechanical link systems interconnected with other physical domains. Furthermore, it provides a straightforward formulation for parallel processing.

EVALUATION OF POSSIBILITIES TO IMPROVE RIGID BODIES

2020 ◽  
Vol 69 (1) ◽  
pp. 392-395
Author(s):  
N.M. Nurullayev ◽  
◽  
D.A. Turgunboyev ◽  
Ye.N. Zholdassov ◽  
◽  
...  
Keyword(s):  
Literature Review ◽  
Software Package ◽  
Scientific Research ◽  
Rigid Bodies ◽  
Robotic Arm ◽  
Electromechanical Devices ◽  
End Effectors ◽  
External Characteristics

Manipulators are used for various purposes in order to simplify tasks or reduce the risk of tasks that are considered impossible, dangerous or difficult for humans. The robotic arm can be equipped with various types of end effectors to perform a variety of tasks. Grips are one of the most commonly used tools for manipulators. This article discusses the analysis of modeling new robotic gripping fingers, based on models of gripping gross rigid bodies of manipulators. A literature review was conducted in the relevant branches of scientific research. The ability to minimize dimensions and masses, as well as the final cost of the product, using available materials and electromechanical devices, various sensors, is evaluated. The external characteristics that make the previously developed analogues ineffective are analyzed. Modeling was released using the SolidWorks software package.

scholarly journals An Efficient Contact Model for the Simulation of Cargo Airdrop Extraction Phase

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Leiming Ning ◽  
Jichang Chen ◽  
Mingbo Tong
Keyword(s):  
Degrees Of Freedom ◽  
Friction Model ◽  
Rigid Bodies ◽  
Contact Dynamics ◽  
Moving Frame ◽  
Contact Friction ◽  
Practical Implementation ◽  
Contact Formulation ◽  
Efficient Code ◽  
Extraction Phase

A high-fidelity cargo airdrop simulation requires the accurate modeling of the contact dynamics between an aircraft and its cargo. This paper presents a general and efficient contact-friction model for the simulation of aircraft-cargo coupling dynamics during an airdrop extraction phase. The proposed approach has the same essence as the finite element node-to-segment contact formulation, which leads to a flexible, straightforward, and efficient code implementation. The formulation is developed under an arbitrary moving frame with both aircraft and cargo treated as general six degrees-of-freedom rigid bodies, thus eliminating the restrictions of lateral symmetric assumptions in most existing methods. Moreover, the aircraft-cargo coupling algorithm is discussed in detail, and some practical implementation details are presented. The accuracy and capability of the present method are demonstrated through four numerical examples with increasing complexity and fidelity.

scholarly journals An Asymptotically Optimal NMPC Core for Multi Degrees of Freedom Rigid Bodies

2012 ◽  
Vol 45 (17) ◽  
pp. 207-212
Author(s):  
Chyon Hae Kim ◽  
Shimon Sugawara ◽  
Shigeki Sugano
Keyword(s):  
Degrees Of Freedom ◽  
Rigid Bodies ◽  
Asymptotically Optimal

Effect of a Planetary Gearbox on the Dynamics of a Rotor System

2018 ◽  
Author(s):  
Ali Tatar ◽  
Christoph W. Schwingshackl
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Behaviour ◽  
Rotor System ◽  
Mode Shapes ◽  
Rotating System ◽  
Planetary Gearbox ◽  
Finite Element Software ◽  
Gyroscopic Effects ◽  
The Masses ◽  
Parameter Values

The dynamic analysis of rotors with bladed disks has been investigated in detail over many decades and is reasonably well understood today. In contrast, the dynamic behaviour of two rotors that are coupled via a planetary gearbox is much less well understood. The planetary gearbox adds inertia, mass, stiffness, damping and gyroscopic moments to the system and can strongly affect the modal properties and the dynamic behaviour of the global rotating system. The main objective of this paper is to create a six degrees of freedom numerical model of a rotor system with a planetary gearbox and to investigate its effect on the coupled rotor system. The analysis is based on the newly developed finite element software “GEAROT” which provides axial, torsional and lateral deflections of the two shafts at different speeds via Timoshenko beam elements and also takes gyroscopic effects into account. The disks are currently considered as rigid and the bearings are modelled with isotropic stiffness elements in the translational and rotational directions. A novel planetary gearbox model has been developed, which takes the translational and rotational stiffness and the damping of the gearbox, as well as the masses and inertias of the sun gear, ring gear, planet gears and carrier into account. A rotating system with a planetary gearbox has been investigated with GEAROT. The gearbox mass and stiffness parameters are identified as having a significant effect on the modal behaviour of the rotor system, affecting its natural frequencies and mode shapes. The higher frequency modes are found to be more sensitive to the parameter changes as well as the modes which have a higher deflection at the location of the gearbox on the rotor system. Compared with a single shaft system, the presence of a gearbox introduces new global modes to the rotor system and decouples the mode shapes of the two shafts. The introduction of a planetary gearbox may also lead to an increase or a reduction of the frequency response of the rotor system based on gear parameter values.

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