Equivalent Moment Of Inertia Research Articles

Research of dynamic phenomena in a model engine stand

Abstract The highest loads on the elements of the crank–piston system of the internal combustion engine occur during the combustion phase which takes place successively in individual cylinders. Smaller, but also significant, loads occur beyond this phase when dynamic forces begin to play a dominant role. The latter depends on the degree of wear of the engine components. The aim of this article was to analyze the stresses in a model stand for testing dynamic phenomena in an internal combustion engine operating without the combustion process. A stand has been developed which includes a combustion engine driven by an electric motor placed on a mobile frame. The coast-down method was used to estimate the average values of the equivalent moment of inertia of the engine for various cylinder configurations with a lack of compression process due to a significant weakening of the valve springs or significant wear of the valve seats. This lack of compression was simulated on a bench by partially loosening the spark plug mounting. The article presents the values of the determined mean values of the equivalent moment of inertia of the engine and the stress values in the stand frame obtained from its model developed with the use of the finite element method. The obtained values were important from the point of view of the engine dynamics simulation process outside the combustion area and the safe foundation and operation of the stand frame during the experimental tests.

OBJECTIVE FUNCTION OF PARAMETRIC OPTIMIZATION OF THE SPEED OF A CLOSED PLANETARY MECHANISM FORMED BY TWO SIMPLE JAMES PLANETARY MECHANISMS

The results of building а mathematical model of estimation the speed of the designed construction of the closed planetary mechanism formed from two simple planetary mechanisms of James are presented. The speed of the designed construction of the mechanism is estimated by the value of the equivalent moment of inertia of the mechanism links reduced to its input shaft. A model is a dimensionless function (analogue the equivalent moment of inertia) of two variables - transmission relations of simple planetary mechanisms, and set of numerical parameters. The parameters take into account the values of the coefficients that characterize the mass inertia models of gears and planet carriers, the design and strength limitations of external gears of simple planetary mechanisms of James, as well as the structure of these mechanisms. Set of values of parameters and range of varying of possible values of transmission relations of simple planetary mechanisms influence on position of a minimum of the analogue the equivalent moment of inertia. The influence of the number of planetary gears of simple planetary mechanisms and the moment of inertia of the planet carrier of the differential mechanism on the positions of the minima of the analogues of the reduced moment of inertia of a closed planetary gear was analyzed in calculations for contact strength and bending strength. Based on the function of the analogue of the equivalent moment of inertia, the objective function of parametric optimization of the project fast-acting of the design of a closed planetary mechanism is built. Keywords: simple James planetary mechanism (mechanisms type ); closed planetary mechanism; moment of inertia of gear-wheel; moment of inertia of the planet carrier; moment of inertia of the planetary mechanism; contact strength of the gearing; bending strength of the gearing; parametric optimization; parametric optimization of the equivalent moment of inertia of the planetary mechanism

Buildings, Causalities, and Injuries Innovative Fuzzy Damage Model during Earthquakes

One of the human concerns has always been to estimate the damage caused before the earthquake and predict the extent of injuries and causalities. An effective model should be developed based on the field survey data for appropriate prediction. In this study, the degree of damage to the structure is first determined and the potential damage is then predicted using field data and fuzzy logic (FL). Effective parameters in the model include the structure height, building age, shear wave velocity in the soil, the plan equivalent moment of inertia, distance to the fault, earthquake factor, the number of inhabitants in the building, and the building height-to-width ratio (HWR). The parameters are fuzzily divided into five classifications: bad, relatively bad, medium, relatively good, and good. The model output parameter, which is the degree of damage to the building, is fuzzy and is divided into five classifications: complete damage, extensive damage, moderate damage, slight damage, and no damage. It should be noted that buildings with steel and concrete structures and moment frames, in the night, day, and traffic time scenarios, have very limited type 3 and 4 injuries with 32, 24, and 16 people, respectively, but type 1 and 2 injuries are significant. During the earthquake at night, the number of people with type 1 and 2 injuries is 975607 and 58757, in the event of the earthquake during the day, the number of people with type 1 and 2 injuries is 739096 and 44513, and during the earthquake at traffic time, the number of people with type 1 and 2 injuries is 492731 and 29675, respectively.

Application of fuzzy modelling to predict the earthquake damage degree of buildings based on field data

Prediction of structural damage prior to earthquake occurrence provides an early warning for stakeholders of building such as owners and urban managers and can lead to necessary decisions for retrofitting of structures before a disaster occurs, legislating urban provisions of execution of building particularly in earthquake prone areas and also management of critical situations and managing of relief and rescue. For proper prediction, an effective model should be produced according to field data that can predict damage degree of local buildings. In this paper in accordance with field data and Fuzzy logic, damage degree of building is evaluated. Effective parameters of this model as an input data of model consist of height and age of the building, shear wave velocity of soil, plan equivalent moment of inertia, fault distance, earthquake acceleration, the number of residents, the width of the street for 527 buildings in the city. The output parameter of the model, which was the damage degree of the buildings, was also classified as five groups of no damage, slight damage, moderate damage, extensive damage, and complete damage. The ranges of input and output classification were obtained based on the supervised center classification (SCC-FCM) method in accordance with field data.

Stiffness amplification coefficient for composite frame beams considering slab spatial composite effect

The slab spatial composite effect arises due to compatible deformation of the reinforced concrete slab with the steel beam in composite frames. This effect can significantly amplify the stiffness of composite frame beams. Current Chinese design code adopts the stiffness amplification coefficient method for the design of composite frame beams, and the equivalent moment of inertia of the composite frame beam can be calculated to conduct the global analysis. However, the current formulae are only suitable for lateral load cases and symmetric I-shaped steel section. Therefore, this study aims to propose unified design equations of the stiffness amplification coefficient considering both vertical and lateral load cases and both symmetric and asymmetric I-shaped steel sections to address the aforementioned limitations. A series of parametric finite element analyses using the beam-shell mixed element model are conducted to derive the unified design equations. The reasonability of the proposed equations is verified by comparing the critical structural indices, such as the natural vibration period, inter-storey shear, lateral displacement, bending moment, and deflection distribution of numerical examples of multi-storey composite frames. Good accuracy is obtained through the comparison between the linear beam element model modified by the proposed equations and the beam-shell mixed element model.

Obstacle avoidance dynamic control of manipulator based on space operator algebra

The traditional manipulator obstacle avoidance dynamics control method ignores the acceleration constraints and speed constraints of the joint obstacle avoidance, and judges the equivalent moment of inertia inaccurately, which leads to large fluctuations in the driving torque of the manipulator motor, and high maximum driving torque and acceleration peaks. Therefore, a dynamic control method of manipulator avoiding obstacles based on space operator algebra is proposed. Using the space recursion method, according to the dynamic space operator algebra system, the manipulator dynamics model is obtained, PID parameters are adjusted, and the model is controlled by three-loop closed-loop PID control to obtain the joint torque under different obstacle avoidance states, and calculate the torque feedforward. The channel transfer function enables the moment to act on the joints of the manipulator to achieve the equivalent moment of inertia control target, to identify and finely control the moment parameters, and to plan the obstacle avoidance trajectory of the manipulator. A parallel manipulator was selected for comparison experiments. The results show that the design method reduces the motor torque ripple, the maximum driving torque, and the acceleration peak in the motion trajectory plane, so that the manipulator has better motion smoothness, reduces motor energy loss, and improves dynamic performance.

The simplified analysis method of nonlinear buckling and displacement of latticed structure

In order to simplify the modeling process of building complex lattice structures by finite element analysis software, a simplified method for nonlinear buckling and deformation analysis of lattice structures based on equivalent inertia moment method is proposed. By comparison with the displacements, the latticed structure is equivalent to a solid structure, and the expression of the equivalent inertia moment of a typical latticed structure is given. The finite element analysis software ANSYS is used to analyze the buckling problem and the deformation of latticed structure and the equivalent solid structure, furthermore, the load-displacement curves of the actual structure and equivalent model are obtained. The results show that the simplified analysis method of nonlinear buckling and deformation of latticed structure is feasible and can satisfy the needs of engineering design.

Simulation diagnostics of power train mechanical drives

Mechanical drives have become the most widely used in design of agricultural machinery. In comparison to drives of machinery applied in other sectors of national economy, they are distinguished by their design features, performance, and cost-performance ratio. In this regard, diagnostics of mechanically driven parts of agricultural machinery is a key to the overall harvester diagnostics. In practice, health of drives is tested with subjective assessment methods, as a rule. The authors suggest application of a kinematic method for diagnostics of agricultural machinery drive trains during their operation; this method implies analysis of position changes and movement of mating parts: wear of parts and backlash of mating drive parts may be assessed by establishment of geometric parameters of diagnostics (linear and angular movements). The total transmission backlash may be established by dynamic torque appearing in transient states of mechanism operation; such total backlash characterizes dynamic errors in movement of an outlet member, which is a result of dependence of equivalent moment of inertia and drag torque from the velocity transmission error. Such diagnostics of potato harvester transmission allows checking of backlashes in separate sections of the chain, as well as assessment of quality of its components adjustment and maintenance. The research data were used for evaluation of overall engineering state of the harvester and determination of dynamic parameters of its components drives.

Instantaneous Gearshift Model Based on Gear-dependent Angular Momentum

The paper presents a new gearbox dynamic model for the effective simulation of simultaneous multi-clutches lock/unlock, by exploiting the Power-Oriented Graphs (POG) modeling technique. The generalized structure of the proposed model allows to simulate various gearbox configurations, which may foresee a change in terms of equivalent moment of inertia on the primary or secondary shaft, depending on the internal clutches configuration being function of the currently engaged gear. The peculiarity of the model lies in the instantaneous engagement of the new gear by skipping the slipping transient related to change of the internal clutches configuration, while preserving the natural loss of energy associated to it. The effectiveness of the presented gearbox model is finally tested and compared with classical gearbox modeling solutions with the aid of some simulation results.

Design of the Transmission Device of the Some Type of the Manipulator

The transmission part of a manipulator is presented in the paper. The part of manipulator transmission device is analysed and the part of manipulator transmission device is designed. Design and calculation of suction hand is represented. The driving motor is checked, the calculation of the equivalent moment of inertia of the transmission system is gained, the motor moment frequency characteristic is presented, and the starting torque of the stepping motor is determined. And the schematic diagram of the overall structure and the schematic diagram of the motor connection plate is presented. The theoretical support and design reference for the design of the transmission device of the manipulator is presented in the paper.

Finite element analysis for engine crankshaft torsional stiffness

Accurate crankshaft torsional stiffness is important to build the lumped parameter model (LPM) for crankshaft torsional vibration analysis. For the crankshaft system of a four-cylinder in-line gasoline engine, a procedure to build the finite element model (FEM) is presented. And the applicability of two ways to set the equivalent mass or equivalent moment of inertia for piston-rod in FEM is declared. When building a lumped parameter model, the concept of rigid-rotation of the crank pin central section around the central line of the crankshaft is proposed, and a method to obtain the torsional angle of the central section is declared. What is more, three post-processing methods are presented to obtain the torsional stiffness coefficients. According to three load cases of no-load, half load and full load, the tests are carried out. The simulation results of FEM and LPM, and the test results have good agreement with each other.

Finite element analysis for engine crankshaft torsional stiffness

Accurate crankshaft torsional stiffness is important to build the lumped parameter model (LPM) for crankshaft torsional vibration analysis. For the crankshaft system of a four-cylinder in-line gasoline engine, a procedure to build the finite element model (FEM) is presented. And the applicability of two ways to set the equivalent mass or equivalent moment of inertia for piston-rod in FEM is declared. When building a lumped parameter model, the concept of rigid-rotation of the crank pin central section around the central line of the crankshaft is proposed, and a method to obtain the torsional angle of the central section is declared. What is more, three post-processing methods are presented to obtain the torsional stiffness coefficients. According to three load cases of no-load, half load and full load, the tests are carried out. The simulation results of FEM and LPM, and the test results have good agreement with each other.

Universal technique of elimination of power parametric excitation in general mechanical systems

A universal technique to transform general mechanical systems in rotative ones with a constant equivalent inertial characteristic is proposed. The technique is based on attaching of a kinematic chain with a program change of inertial characteristic to a reduction link. The inertial characteristic in addition to the main one forms the reduction link with a constant equivalent moment of inertia. Such modification of a mechanical drive eliminates parametric power drive excitation, reduces the level of dynamic load in links and drive joints, that results in reliability and system resource improvement.

Work of a railway sleeper as a structure with variable cross-section - the issue of an equivalent cross-section

Abstract: The article presents an analysis of the work of a sleeper as a construction with variable section, and of the method of determining an equivalent section, constant throughout the length, the utilisation of which would have similar shapes of deflection and bending stress lines in relation to the real, variable cross section. Using an analytical and a numerical model, vertical displacements and stresses for two types of sleepers – PS-94 and PS-08 – were determined. The comparison of the methods allows for calculating an equivalent moment of inertia for analytical calculations, specifically the dynamic ones.

Dynamic analysis for vertical soft landing of reusable launch vehicle with landing strut flexibility

Based on oleo-honeycomb dampers, a 6-DOF vertical soft landing dynamic model for reusable launch vehicle considering landing strut flexibility is constructed. In order to better analyze the lateral deflection and friction force of the “cantilever beam” type landing strut, a new model for strut is incorporated. Static analysis is first performed based on the rotation angle compatibility equations to attain the equivalent inertia moment. Then the strut lateral vibration model and friction force model are obtained by simplifying it as viscoelastic beam with a tip mass. After that, the ADAMS models are established to perform the comparison and verification analysis of the 6-DOF dynamic model. The results show that the results of 6-DOF dynamic model can approximately approach to the results of rigid-flex coupling model established in ADAMS. Furthermore, the research of the influence of assembly gap between cylinders and bearings, bearing’s elastic modulus, friction coefficient and initial overlapping length on the vehicle landing performance is carried out. The results show that each parameter has different influence on the landing performance, and a reasonable selection of these parameters accordingly enables a higher landing performance.

Robust steering-assist torque control of electric-power-assisted-steering systems for target steering wheel torque tracking

This paper describes robust steering assist torque control of electric-power-assisted-steering (EPAS) systems for a target steering wheel torque tracking. The steering assist torque control algorithm has been developed to overcome the major disadvantage of the conventional method of time-consuming tuning to achieve the desired steering feel. A reference steering wheel torque map was designed by post-processing data obtained from target performance vehicle tests with a highly-rated steering feel for both sinusoidal and transition steering inputs. Adaptive sliding-mode control was adopted to ensure robustness against uncertainty in the steering system, and the equivalent moment of inertia damping coefficient and effective compliance were adapted to improve tracking performance. Effective compliance played a role in compensating the error between the nominal rack force and the actual rack force. The performance of the proposed controller was evaluated by conducting computer simulations and a hardware-in-the-loop simulation (HILS) under various steering conditions. Optimal steering wheel torque tracking performances were successfully achieved by the proposed EPAS control algorithm.

굴삭기 선회시스템의 관성 내구 시험을 위한 플라이휠의 등가관성 모멘트 결정

This study determined the equivalent moment of inertia of the upper rotating body of an excavator, for the inertial endurance test of an excavator slewing system. The input speed and torque of the slewing reducer were measured by an excavator slewing test, and the equivalent moment of inertia of the upper rotating body of the excavator was calculated using iterative calculation. We developed a dynamic simulation model of the excavator slewing system, and validated the model by comparing it with the slewing test results. Using the validated model, we further developed a simulation model for the inertial endurance test, that considers the moment of inertia of the upper rotating body of an excavator. We concluded that the new dynamic model for the inertial endurance test of an excavator slewing system well exemplified the actual slewing test results.

Synthesis, optimization and experimental validation of reactionless two-DOF parallel mechanisms using counter-mechanisms

The synthesis of reactionless mechanisms generally involves the force balancing of a mechanism using countermasses followed by the dynamic balancing of the inertia using counter-rotations. This approach requires that the force balanced mechanism have a constant equivalent moment of inertia for any configuration. Two of the main drawbacks of reactionless mechanisms are a significant increase in mass and actuation inertia. In this paper, a counter-mechanism is introduced in order to dynamically balance a force balanced two-DOF mechanism with variable inertia, which is expected to reduce the aforementioned drawbacks. The conditions for which the counter-mechanism matches the moment of inertia of the main mechanism for any configuration are derived. Then, in order to fairly compare the use of a counter-mechanism instead of counter-rotations, the balancing strategies are optimized regarding the addition of mass and actuation inertia using Lagrange multipliers. The results are optimal rules for the design of reactionless mechanisms and optimal mass-inertia curves which are akin to Pareto curves. These results allow to demonstrate the advantages of counter-mechanisms over counter-rotations, especially regarding added actuation inertia and compactness. Also, the significant influence of the radius of gyration of the counter-inertias on the optimal mass-inertia curves is revealed. Finally, examples of reactionless mechanisms are presented and prototypes are tested in order to validate the concepts.

Application features of fuzzy controllers on example of DC motor speed control

A prerequisite for the use of intelligent control methods, including algorithms of fuzzy logic, is increasing complexity in all industries, especially when parameters of technical systems while in operation vary in wide range. The paper provides comparative analysis of the basic types of common fuzzy direct action controllers on the example of speed control system in the DC motor drive. Design features of these types of fuzzy controllers are shown. Their comparison with traditional PI controller is carried out through the use of simulation, including the conditions of uncertainty expressed in changing of equivalent moment of inertia of the motor shaft. As a result, the conclusion about the feasibility of fuzzy PID-type controller application is made. The features of fuzzy controllers outlined in the paper can be summarized to more complex motor drive systems and to other non-linear systems that require the maintenance of any parameter within a given range.

Equivalent computational models and deflection calculation methods of box girders with corrugated steel webs

This study found that it is improper to use equivalent concrete webs (ECWs) to replace corrugated steel webs (CSWs) in the MIDAS Civil. To reflect the mechanical performance difference of CSWs in different directions, a more precise theoretical model, the assimilated orthotropic plate (AOP), is presented to simulate CSWs. 3D Finite element analysis demonstrates that the AOP model can yield a more precise description of CSWs compared with the ECW model in MIDAS. In addition, this paper presents a unified calculation method for bending deformation suitable for the analysis of beams with equal-area or variable-area cross-sections, in which the non-prismatic beam is made equivalent to the prismatic beam by introducing the concept of equivalent inertia moment. Additionally, the formula of shear deformation in a non-prismatic box girder with CSWs is also derived with Timoshenko beam theory. These derived formulas for non-prismatic box girder with CSWs agree well with the numerical and measured data.