Damaged-aircraft trailer dynamics simulation and vibration optimization

2019 ◽  
Vol 234 (1) ◽  
pp. 110-121
Author(s):  
Zhenyu Hong ◽  
Xiaoli Yu ◽  
Dongsheng Zhang ◽  
Zhenpeng He
Keyword(s):  
Hydraulic System ◽  
Degrees Of Freedom ◽  
Dynamic Performance ◽  
Dynamics Simulation ◽  
Physical Parameters ◽  
Vertical Acceleration ◽  
Damping Force ◽  
Maximum Acceleration ◽  
Secondary Damage ◽  
Stiffness And Damping

As a rescue vehicle, damaged-aircraft trailer is used to move damaged aircraft quickly to restore the normal order of the airport. Several damaged-aircraft trailer parameters such as tire stiffness and damping of the suspension hydraulic system influence the dynamic performance significantly. In this article, a simplified 9 degrees of freedom model of damaged-aircraft trailer is established considering the physical parameters of suspension and tires. The relationships among the parameters of the suspension hydraulic components, the elastic force and damping force are established, and then the optimization model of the whole vehicle is obtained. In order to reduce the secondary damage to the aircraft, the multi-island genetic algorithm is used to optimize the suspension system and tire. During the calculation, the maximum vertical acceleration of damaged-aircraft trailer is taken as objective function for variable parameters of the suspension hydraulic system and the tire. As a result, the performance of the vehicle is greatly improved with the maximum acceleration of 0.2 m/s2 after optimization.

Development of the Humanoid Robot LOLA

2006 ◽  
Vol 5-6 ◽  
pp. 529-540 ◽  
Author(s):  
Heinz Ulbrich ◽  
T. Buschmann ◽  
S. Lohmeier
Keyword(s):  
Degrees Of Freedom ◽  
Humanoid Robot ◽  
Dynamic Performance ◽  
Hardware Design ◽  
Dynamics Simulation ◽  
Sensor Data ◽  
Knee Joints ◽  
Lightweight Construction ◽  
Walking Motion ◽  
And Control

This paper presents the performance enhanced humanoid robot LOLA which is currently being manufactured. Hardware design, controllers and simulation are based on ex- perience gained during the development of the robot JOHNNIE. The objective of the current research project is to realize a fast, human-like and autonomous walking motion. To enable an optimal design of the robot with respect to lightweight construction, motor and drive sizing, an appropriate simulation model is required. Dynamics simulation is a key tool to develop the hardware and control design properly. For hardware design and detailed dynamic analysis a comprehensive model including motor and gear dynamics is required, while for controller de- sign and stability analysis a simplified model for global system dynamics is sufficient. Both robots are characterized by a lightweight construction. In comparison to JOHNNIE, the new robot LOLA has a modular, multi-sensory joint design with brushless motors. Moreover, the previously purely central electronics architecture is replaced by a network of decentral joint controllers, sensor data acquisition and filtering units and a central PC. The fusion of motor, gear and sensors into a highly integrated mechatronic joint module has several advantages for the whole system, including high power density, good dynamic performance and reliability. Ad- ditional degrees of freedom are introduced in elbow, waist and toes. Linear actuators are used for the knee joints to achieve a better mass distribution in the legs.

scholarly journals Research on Switching Interconnection Modes and Game Control of Interconnected Air Suspension

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3218 ◽  
Author(s):  
Sun ◽  
Lin ◽  
Geng ◽  
Li ◽  
Jiang
Keyword(s):  
Ride Comfort ◽  
Dynamic Performance ◽  
Bench Test ◽  
Vertical Acceleration ◽  
Infinite Time ◽  
Damping Force ◽  
Air Suspension ◽  
Optimal Damping ◽  
Time Differential ◽  
Switching Controller

To solve the contradiction between handling stability and ride comfort of vehicles with interconnected air suspension system (IASS) and reduce the energy consumption of air suspension with adjustable spring stiffness, a coordinated control for dynamic performance was designed based on the logic of switching interconnection modes and game control for the damper. The control system consists of a switching controller for air suspension interconnection modes and a distribution controller for the damping force. The switching controller determines the optimal air suspension interconnection mode by calculating the vehicle dynamic performance index in real-time. The distribution controller achieves a distribution for optimal damping force based on an infinite time differential game. veDYNA software that is a vehicle dynamics analysis software based on MATLAB/Simulink was used to verify the algorithm, and the accuracy was verified by a bench test. Finally, the results show this coordinated system can significantly improve the ride comfort and restrain the pitching motion. Compared with traditional suspension, the vertical acceleration decreases by 18.32% and the dynamic stroke decreases by more than 10% under the straight condition; the vertical acceleration decreases by 12.24% and the roll angle decreases by 1.26% under the steering condition.

Reversibly Sampling Conformations and Binding Modes Using Molecular Darting

2020 ◽  
Author(s):  
Samuel C. Gill ◽  
David Mobley
Keyword(s):  
Monte Carlo ◽  
Ligand Binding ◽  
Binding Sites ◽  
Degrees Of Freedom ◽  
Dynamics Simulation ◽  
Hiv Integrase ◽  
Binding Modes ◽  
System A ◽  
Multiple Binding ◽  
Internal Degrees Of Freedom

<div>Sampling multiple binding modes of a ligand in a single molecular dynamics simulation is difficult. A given ligand may have many internal degrees of freedom, along with many different ways it might orient itself a binding site or across several binding sites, all of which might be separated by large energy barriers. We have developed a novel Monte Carlo move called Molecular Darting (MolDarting) to reversibly sample between predefined binding modes of a ligand. Here, we couple this with nonequilibrium candidate Monte Carlo (NCMC) to improve acceptance of moves.</div><div>We apply this technique to a simple dipeptide system, a ligand binding to T4 Lysozyme L99A, and ligand binding to HIV integrase in order to test this new method. We observe significant increases in acceptance compared to uniformly sampling the internal, and rotational/translational degrees of freedom in these systems.</div>

scholarly journals A Dynamical Study of Fusion Hindrance with Nakajima-Zwanzig Projection Method

2021 ◽  
Author(s):  
Yasuhisa Abe ◽  
David Boilley ◽  
Quentin Hourdillé ◽  
Caiwan Shen
Keyword(s):  
Cross Sections ◽  
Degrees Of Freedom ◽  
Operator Method ◽  
Initial Distribution ◽  
Physical Parameters ◽  
Relaxation Processes ◽  
Fast Variable ◽  
Dynamical Study ◽  
Injection Point ◽  
Slow Variables

Abstract A new framework is proposed for the study of collisions between very heavy ions which lead to the synthesis of Super-Heavy Elements (SHE), to address the fusion hindrance phenomenon. The dynamics of the reaction is studied in terms of collective degrees of freedom undergoing relaxation processes with different time scales. The Nakajima-Zwanzig projection operator method is employed to eliminate fast variable and derive a dynamical equation for the reduced system with only slow variables. There, the time evolution operator is renormalised and an inhomogeneous term appears, which represents a propagation of the given initial distribution. The term results in a slip to the initial values of the slow variables. We expect that gives a dynamical origin of the so-called “injection point s” introduced by Swiatecki et al in order to reproduce absolute values of measured cross sections for SHE. A formula for the slip is given in terms of physical parameters of the system, which confirms the results recently obtained with a Langevin equation, and permits us to compare various incident channels.

Experimental and Analytical Investigations of a Low Pressure Model Turbine During Forced Response Excitation

2010 ◽  
Author(s):  
Christoph Heinz ◽  
Markus Schatz ◽  
Michael V. Casey ◽  
Heinrich Stu¨er
Keyword(s):  
Degrees Of Freedom ◽  
Timing Analysis ◽  
Dynamic Performance ◽  
Amplitude Distribution ◽  
Low Pressure ◽  
Forced Response ◽  
Operating Conditions ◽  
Linear Regression Method ◽  
Rotor Shaft ◽  
Aerodynamic Damping

To guarantee a faultless operation of a turbine it is necessary to know the dynamic performance of the machine especially during start-up and shut-down. In this paper the vibration behaviour of a low pressure model steam turbine which has been intentionally mistuned is investigated at the resonance point of an eigenfrequency crossing an engine order. Strain gauge measurements as well as tip timing analysis have been used, whereby a very good agreement is found between the methods. To enhance the interpretation of the data measured, an analytical mass-spring-model, which incorporates degrees of freedom for the blades as well as for the rotor shaft, is presented. The vibration amplitude varies strongly from blade to blade. This is caused by the mistuning parameters and the coupling through the rotor shaft. This circumferential blade amplitude distribution is investigated at different operating conditions. The results show an increasing aerodynamic coupling with increasing fluid density, which becomes visible in a changing circumferential blade amplitude distribution. Furthermore the blade amplitudes rise non-linearly with increasing flow velocity, while the amplitude distribution is almost independent. Additionally, the mechanical and aerodynamic damping parameters are calculated by means of a non-linear regression method. Based on measurements at different density conditions, it is possible to extrapolate the damping parameters down to vacuum conditions, where aerodynamic damping is absent. Hence the material damping parameter can be determined.

Tilting Pad Journal Bearings: A Discussion on Stability Calculation, Frequency Dependence, and Pad and Pivot Flexibility

2012 ◽  
Author(s):  
Jason C. Wilkes ◽  
Dara W. Childs
Keyword(s):  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Operating Temperature ◽  
Excitation Frequency ◽  
Full Model ◽  
Stability Calculation ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearing

For several years, researchers have presented predictions showing that using a full tilting-pad journal bearing (TPJB) model (retaining all of the pad degrees of freedom) is necessary to accurately perform stability calculations for a shaft operating on TPJBs. This paper will discuss this issue, discuss the importance of pad and pivot flexibility in predicting impedance coefficients for the tilting-pad journal bearing, present measured changes in bearing clearance with operating temperature, and summarize the differences between measured and predicted frequency dependence of dynamic impedance coefficients. The current work presents recent test data for a 100 mm (4 in) five-pad TPJB tested in load on pad (LOP) configuration. Measured results include bearing clearance as a function of operating temperature, pad clearance and radial displacement of the loaded pad (the pad having the static load vector directed through its pivot), and frequency dependent stiffness and damping. Measured hot bearing clearances are approximately 30% smaller than measured cold bearing clearances and are inversely proportional to pad surface temperature; predicting bearing impedances with a rigid pad and pivot model using these reduced clearances results in overpredicted stiffness and damping coefficients that are several times larger than previous comparisons. The effect of employing a full bearing model versus a reduced bearing model (where only journal degrees of freedom are retained) in a stability calculation for a realistic rotor-bearing system is assessed. For the bearing tested, the bearing coefficients reduced at the frequency of the unstable eigenvalue (subsynchronously reduced) predicted a destabilizing cross-coupled stiffness coefficient at the onset of instability within 1% of the full model, while synchronously reduced coefficients for the lightly loaded bearing required 25% more destabilizing cross-coupled stiffness than the full model to cause system instability. The same stability calculation was performed using measured stiffness and damping coefficients at synchronous and subsynchronous frequencies. These predictions showed that both the synchronously measured stiffness and damping and predictions using the full bearing model were more conservative than the model using subsynchronously measured stiffness and damping, an outcome that is completely opposite from conclusions reached by comparing different prediction models. This contrasting outcome results from a predicted increase in damping with increasing excitation frequency at all speeds and loads; however, this increase in damping with increasing excitation frequency was only measured at the most heavily loaded conditions.

The Surface Roughness Effect on the Dynamic Stiffness and Damping Characteristics of the Hydrostatic Thrust Spherical Bearings: Part 5 of 5 — Clearance Type of Bearings

2007 ◽  
Author(s):  
Ahmad W. Yacout
Keyword(s):  
Surface Roughness ◽  
Capillary Tube ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Major Effect ◽  
Design Parameters ◽  
Compressibility Effect ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Fluid Compressibility

This study has theoretically analyzed the surface roughness, centripetal inertia and recess volume fluid compressibility effects on the dynamic behavior of a restrictor compensated hydrostatic thrust spherical clearance type of bearing. The stochastic Reynolds equation, with centripetal inertia effect, and the recess flow continuity equation with recess volume fluid compressibility effect have been derived to take into account the presence of roughness on the bearing surfaces. On the basis of a small perturbations method, the dynamic stiffness and damping coefficients have been evaluated. In addition to the usual bearing design parameters the results for the dynamic stiffness and damping coefficients have been calculated for various frequencies of vibrations or squeeze parameter (frequency parameter) and recess volume fluid compressibility parameter. The study shows that both of the surface roughness and the centripetal inertia have slight effects on the stiffness coefficient and remarkable effects on the damping coefficient while the recess volume fluid compressibility parameter has the major effect on the bearing dynamic characteristics. The cross dynamic stiffness showed the bearing self-aligning property and the ability to oppose whirl movements. The orifice restrictor showed better dynamic performance than that of the capillary tube.

Dynamic Characterization of an Integral Squeeze Film Bearing Support Damper for a Supercritical CO2 Expander

2017 ◽  
Author(s):  
Bugra Ertas ◽  
Adolfo Delgado ◽  
Jeffrey Moore
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Mechanical Impedance ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Damping Behavior ◽  
Impedance Testing ◽  
Stiffness And Damping ◽  
Onset Of Cavitation

The present work advances experimental results and analytical predictions on the dynamic performance of an integral squeeze film damper (ISFD) for application in a high-speed super-critical CO2 (sCO2) expander. The test campaign focused on conducting controlled orbital motion mechanical impedance testing aimed at extracting stiffness and damping coefficients for varying end seal clearances, excitation frequencies, and vibration amplitudes. In addition to the measurement of stiffness and damping; the testing revealed the onset of cavitation for the ISFD. Results show damping behavior that is constant with vibratory velocity for each end seal clearance case until the onset of cavitation/air ingestion, while the direct stiffness measurement was shown to be linear. Measurable added inertia coefficients were also identified. The predictive model uses an isothermal finite element method to solve for dynamic pressures for an incompressible fluid using a modified Reynolds equation accounting for fluid inertia effects. The predictions revealed good correlation for experimentally measured direct damping, but resulted in grossly overpredicted inertia coefficients when compared to experiments.

Application of Semi-Active Oil Damper System to Base Isolation Systems

2002 ◽  
Author(s):  
Takashi Kawai ◽  
Yasuo Tsuyuki ◽  
Yutaka Inoue ◽  
Osamu Takahashi ◽  
Koji Oka
Keyword(s):  
Base Isolation ◽  
Shaking Table ◽  
The Other ◽  
Damping Coefficient ◽  
Damping Force ◽  
Mass Model ◽  
Maximum Acceleration ◽  
Rubber Bearing ◽  
Single Mass ◽  
Isolation Systems

This paper deals with one of the applications of the Semi-Active Oil Damper system, which applies base isolation systems reducing the maximum acceleration. The theory of the Semi-Active Oil Damper system is based on Karnopp Theory. The theory has been actually now in use for a Semi-active suspension system of the latest Shinkansen (New trunk lines) trains to improve passenger’s comfortable riding. Various experiments have been conducted using a single mass model whose weight is 15 ton on the shaking table. This model is supported by the rubber bearing. The natural frequency is 0.33Hz of this system. Two Semi-Active Oil Damper were installed in the model and excited the table for one horizontal direction. The maximum damping force of each Semi-Active Oil Damper used for the model is 4.21 kN. The damper can change the damping coefficient by utilizing two solenoid valves. Therefore, the dynamic characteristic of the damping force has two modes. One is a hard damping coefficient and the other is a soft one. It was confirmed that the maximum acceleration of the Semi-Active Oil Damper system can be reduced more than 20% in comparison with the passive Oil Damper system in our tests.

Electromagnetic Shock Absorbers for Automotive Suspensions: Electromechanical Design

2006 ◽  
Author(s):  
Nicola Amati ◽  
Aldo Canova ◽  
Fabio Cavalli ◽  
Stefano Carabelli ◽  
Andrea Festini ◽  
...  
Keyword(s):  
Shock Absorber ◽  
Dynamic Performance ◽  
Integrated Design ◽  
Design Procedure ◽  
Resistive Load ◽  
Added Resistance ◽  
Damping Force ◽  
Quarter Car Model ◽  
Car Model ◽  
Shock Absorbers

This article illustrates the modeling and design of electromechanical shock absorbers for automotive applications. Relative to the commonly used hydraulic shock absorbers, electromechanical ones are based on the use of linear or rotative electric motors. If electric motor is of the DC-brushless type, the shock absorber can be devised by shunting its electric terminals with a resistive load. The damping force can be modified by acting on the added resistance. An integrated design procedure of the electrical and mechanical parameters is presented in the article. The dynamic performance that can be obtained by a vehicle with electromechanical dampers is verified on a quarter car model.

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