Center Of Gravity Position Research Articles

Changes of body balance before and after total knee arthroplasty in patients who suffered from bilateral knee osteoarthritis

PurposeIt is still controversial whether simultaneous or staged total knee arthroplasty (TKA) is most desirable for patients with bilateral knee osteoarthritis. We retrospectively evaluated changes in balance among patients with bilateral osteoarthritis who underwent staged TKA using a gravicorder. MethodsPatients were stratified into two groups: the unilateral group (UG) (22 patients) consisted of patients who did not undergo a second TKA within 24months of the first TKA, and the bilateral group (BG) (20 patients) were those who had a second TKA within 12months after initial TKA. ResultsThe mean gravity center position (GCP), which indicates the translation of GCP in the mediolateral direction between pre- and post-TKA shifted to the operative side in both groups after initial surgery. While the GCP was maintained on the same side in UG over 2 years follow-up, in BG it moved to the opposite side and approached a central position after the second TKA. Locus length of GCP (LG), which indicates postural control function by proprioceptive reflex showed significant improvement after initial TKA in UG, while BG showed significant improvement after the second TKA. ConclusionsThe degree of LG improvement after initial TKA may indicate the necessity of a second TKA for patients with bilateral osteoarthritis. The current study suggests that simultaneous bilateral TKA is not always necessary for patients with bilateral knee arthritis, and that properly performed rehabilitation such as improving postural sway after initial TKA might attenuate the timing for the second TKA.

Fuel burn prediction algorithm for cruise, constant speed and level flight segments

AbstractThis paper presents a new algorithm that predicts the quantity of fuel burned by an aircraft flying at a constant speed and altitude. It considers the continuous fuel burn rate variation with time caused by the gross weight (and centre of gravity position) modification due to the fuel burn process itself. The algorithm was developed for use by the Flight Management System (FMS) and employs the same aircraft performance data as the existing FMS fuel burn prediction algorithms. The new fuel burn method was developed for aircraft models that use the centre of gravity position as well as for models that do not consider the centre of gravity position. This algorithm was developed for normal flight conditions. Algorithm performances were evaluated for two aircraft models: one for models that use an aircraft’s centre of gravity position – a more complex and computing intensive method, and one for those that do not use the centre of gravity position. The validation data were generated based on the information produced on a CMC Electronics – Esterline FMS platform that used identical aircraft models and performance data for identical flight conditions.

Some Approaches to the Rolling Wheels’ Dynamics Modelling in the Weight-in-Motion Problem

Abstract Some possibilities of fibre-optic sensors (FOS) application for measuring the weight of moving vehicles realized in weightin- motion (WIM) systems are discussed. As the first, the model of small-buried seismic sensor transient response excited by a car tyre interaction with asphalt-concrete road pavement is proposed. It is supposed that a seismic wave received by the sensor is the vertical component of surface Raleigh wave. The model is based on supposition that a tyre footprint is acceptable to consider as some array of point sources of these waves. The proper algorithms permit to vary different parameters of the array excitation, as to footprint dimensions, load distribution, car velocities and others. The set of Matlab codes is worked out for seismic pulses modelling and processing. The second way considered is to simulate the FOS signal in the basis of differential equations describing a deformable wheel behaviour, or wheel oscillations, in order to identify relations with optoelectronic mechanical parameters. An attempt to find the mass of the vehicle is based on minimizing the discrepancy between the actual FOS signal and the solution of the differential equation. The accuracy of the evaluated weight depends on many external factors, the mathematical modelling of them are expressed in the numerical values of the coefficients and external stimuli. The influence of these factors are analysed and tested by simulations and field experiments. One of ideas in dynamic weighing problem solution should consist in evaluation of position of virtual gravity centre of the vehicle in time. The processing algorithm of the data received from the FOS is proposed based on conception of database retaining in some reference system memory. Certain requirements concerning the elements and blocks of the algorithm are defined as well. The reference system is realized as the digital filter with the finite impulse response. The method to estimate the filter coefficients is worked out. Several experiments with this algorithm have been carried out for the vehicle identification with the reference loads adopted from real data. The different factors have an influence on the measurement accuracy of FOS. The roadbed features, temperature, nonlinearities and delay effects in FOS are among them. The results of laboratory and field measurements with FOS responses to different axle’s loadings are presented. Charging and inertial characteristics of FOS under the impact of various external factors (protective cover, temperature, contact area, and installation mode especially) as well as their approximations are investigated. It is found that the final calibration of the FOS has to be done individually and only after it has been installed in the pavement. Certain methods and algorithms of linearization, as well temperature and dynamic errors compensation of FOS data are discussed.

슬라이딩 메커니즘을 이용한 서비스 로봇의 밸런싱 자세의 안정화에 대한 실험연구

This paper presents the analysis and control of the position of the COG (Center of Gravity) for a two-wheel balancing robot. The two-wheel balancing robot is required to maintain balance by driving two wheels only. Since the robot is not exactly symmetrical and its dynamics is changing with respect to moving parts, robust balancing control is difficult. Balancing performance becomes difficult when two arms hold a heavy object since the center of gravity is shifted out of the wheel axis. Novel design of a sliding waist mechanism allows the robot to react against the shift of the COG by moving the whole upper body to compensate for the imbalance of the mass as a counter balancer. To relocate the COG position accurately, the COG is analyzed by force data measured from two force sensors. Then the sliding COG mechanism is utilized to control the sliding waist position. Experimental studies are conducted to confirm the proposed design and method.

Analysis of the Stress State in Brake Caliper Mounts of Front Motorbike Suspensions

The aim of this work is to analyze the stress and the strain fields in the brake caliper mounts of front motorbike suspensions produced by the braking action. First of all, some formulae useful to evaluate the maximum braking force in function of the vehicle features (e.g., total mass, centre of gravity position, tyre dimension, and brake disk diameter) have been developed. A mathematical model useful to calculate the axial, the bending, and the torque stresses on the braking caliper mounts has been then defined. The model has been developed by comparing the theoretical results with those obtained by some numerical analyses, based on the finite element method. An ad hoc test equipment has been, finally, designed and manufactured in order to define and analyze experimentally the strength of different types of brake caliper mounts and, at the same time, to verify the proposed model.

An Easy Platform for Postural Balance Analysis by the Evaluation of Instantaneous Center of Gravity

The aim of this paper is to present an easy instrument and method for postural balance analysis based on evaluation of instantaneous center of gravity (COG) were the subject is stand on innovative force platform. The instrument is realized with three identical composite sensor supporting a feet plate were used to measure the ground reaction force applied by subject during postural balance analysis. A Microsystems based on microcontroller was built in order to drive the instrumentation and a graphical user interface was realized. The signals acquisitions are displayed on the PC screen when the COG moves in the xy plan. After the calculation and programming of the COG coordinates point, the plot of the XG and YG time series of the COG position during a postural balance analysis is easily obtained and recording. The effect of visual input is studied by performing the test with eyes open and then closed. The dynamic parameters show clear indicator of the postural balance. Objective method of diagnosis is to access to postural stability for identifying persons at risk of falling.

Calculation of Tilting Torque for Converter Based on Solidworks

One 150 ton converter of an iron and steel group occurred nodded phenomenon in the production process, the dynamic characteristics is poor. Initially be suspected that the converter exist “negative” torque steel. In order to clarify the changes of tilting torque in the steel process. apply Solidworks software ,create 3D model of converter, then determine the Center of gravity position and calculate the tilting torque of the converter with the tilting angle changes. Solidworks software is parameterized 3D design software, can calculate quickly and accurately, has strong analytical processing capabilities. This paper made to calculate provide a simple method of calculation for converter equipment design and maintenance.

Rear Axle Layout for the Speede Research Vehicle

The foundation of a dynamic as well as safe driving behaviour is, even in combination with modern vehicle control systems, based on the passive set-up of the suspension. Considering the constraints of a powerful rear wheel drive with torque vectoring functionality and centre of gravity position towards the rear of the car, special attention has to be paid to the rear axle layout. Regarding the kinematics the toe and camber curves are defined after choosing the position of roll and pitch centres. A linear increase of toe-in during bump motion reduces the general tendency towards oversteering of the vehicle. At the same time, toe angle changes during wheel travel must be limited to ensure sufficient directional stability on uneven tracks. To maximise the forces transmitted by the tyre in longitudinal and lateral directions, the tyre contact patch area must be as large as possible at all times. Thus a progressive increase of negative camber angle in bump motion is desirable to partly compensate the reduction of the contact patch area induced by the roll motion of the vehicle body during cornering. Here, as well, a compromise needs to be found regarding directional stability requirements. Besides the wheel trajectories the elasto-kinematics, that means the change of wheel alignment due to longitudinal and lateral forces, play an important role while designing the vehicle dynamic characteristics. A tendency towards toe-in at the outer rear wheel in a turn will reduce the oversteering tendency of the vehicle. Under longitudinal braking and propulsion forces only small changes of toe angle are desirable.

Energy production and consumption prediction and their response to environment based on coupling model in China

The paper presents the prediction of total energy production and consumption in all provinces and autonomous regions as well as determination of the variation of gravity center of the energy production, consumption and total discharge of industrial waste water, gas and residue of China via the energy and environmental quality data from 1978 to 2009 in China by use of GM(1,1) model and gravity center model, based on which the paper also analyzes the dynamic variation in regional difference in energy production, consumption and environmental quality and their relationship. The results are shown as follows. 1) The gravity center of energy production is gradually moving southwestward and the entire movement track approximates to linear variation, indicating that the difference of energy production between the east and west, south and north is narrowing to a certain extent, with the difference between the east and the west narrowing faster than that between the south and the north. 2) The gravity center of energy consumption is moving southwestward with perceptible fluctuation, of which the gravity center position from 2000 to 2005 was relatively stable, with slight annual position variation, indicating that the growth rates of all provinces and autonomous regions are basically the same. 3) The gravity center of the total discharge of industrial waste water, gas and residue is characterized by fluctuation in longitude and latitude to a certain degree. But, it shows a southwestward trend on the whole. 4) There are common ground and discrepancy in the variation track of the gravity center of the energy production & consumption of China, and the comparative analysis of the gravity center of them and that of total discharge of industrial waste water, gas and residue shows that the environmental quality level is closely associated with the energy production and consumption (especially the energy consumption), indicating that the environment cost in economy of energy is higher in China.

Vibrational spectroscopic, optical and thermal properties of a deuterated ferroic crystal, [(CH2OD)3CND3]2SiF6—An experimental and theoretical study

[(CH2OD)3CND3]2SiF6 ferroic crystal, abbreviated as D-(TRIS)2SiF6 crystal was investigated. Optical (linear birefringence) and thermal (differential scanning calorimetry, DSC) measurements indicated a solid–solid phase transition (PT) of the first order at 185K. The vibrational infrared spectra of powdered D-(TRIS)2SiF6 crystal in Nujol and Fluorolube mulls were studied in the wide range of temperature, from 308K to 133K. The temperature changes of wavenumber, width, centre of gravity position and intensity of the bands were analyzed to clarify the molecular mechanism of the phase transition and the contribution of SiF62− and CH2OD groups to the PT. A wide range (4000–400cm−1) of internal vibrations of the DTRIS+ and SiF62− ions was investigated and the assignment of the observed infrared absorption bands was discussed. Raman spectra of the crystal at room temperature (RT) were recorded and discussed in relation to the structure of isostructural (TRIS)2SiF6 crystal in the range (4000–400cm−1). Theoretical calculations were made based on density functional theory (DFT). The calculated normal vibrational modes of the molecules, their intensities and frequencies were compared with those obtained from experimental data.

203 低重心型平行二輪ビークルの搭乗者を含む重心位置制御システムの構築(トレーニング・制御)

In this paper, structure design and modeling of novel seating-type two wheel vehicle with lower position of gravity center is proposed. The vehicle's gravity center is assigned at the lower position than that of the wheel axis, whose vehicle has the structure of the pendulum. Therefore, it enables the passenger to always keep the stable posture, even if the vehicle is in the power-off or control-off state. Then, the gravity center position's adjustment system is installed inside the vehicle body. Swing of the vehicle body generated by the bias of the passenger's gravity center position is controlled by the proposed seat positioning system. As a result, alignment of pitch angle of the vehicle body is possible by a seat positioning system that has been proposed.

Performance analysis of EV for different mass distributions to ensure safe handling

Centre of gravity (CG) is one of the significant parameters of vehicle mass property related to vehicle handling. Position of CG in each direction (longitudinal, lateral and vertical) affects stability of the vehicle eventually. Change in CG position depends on different architectural arrangements of drive train and sub-systems which affect mass distribution of the vehicle. Being zero-emission technology, rapid commercialization of electric vehicle (EV) requires more emphasis on production of new automobiles and retrofitting as well. In case of retrofitting, placement of all EV drive train and other sub-systems requires both static and dynamic analysis for change in CG position due to different mass distributions. In this paper, analysis has been conducted by MATLAB SIMULINK based vehicle model to demonstrate effect of CG in vehicle maneuvering. Outcome of this investigation indicates the evaluation of different retrofitted EV architectures considering different mass distributions under the constraint of vehicle mass and dimension. This study evaluates vehicle performance with different architectures to ensure safe handling and stability in both normal and sudden maneuvering conditions of the vehicle.

331 ゴルフクラブヘッドの重心位置がシャフト挙動に及ぼす影響(スポーツにおける打撃(2))

331 ゴルフクラブヘッドの重心位置がシャフト挙動に及ぼす影響(スポーツにおける打撃(2))

Study of Railway Freight Vehicle Body's Dynamic Model Based on Goods Loading Technical Standards

The gravity center position of the loaded car-body is always constant during the dynamic analysis currently. To enhance vehicle dynamic analysis for goods transportation, multi-body system dynamics and vehicle-track coupling dynamics are the basic theories for the study. The car-body which includes goods model is called loaded car-body, and its gravity center calculation formulas are put forward based on Chinas railway goods loading technical standards. After that, the vertical, lateral, rolling, pitching and yawing vibration modes dynamic equations are established for loaded car-body. The C70 open top vehicle is an example for the calculation of different height of gravity center of loaded vehicle, and the railway line condition is grade in China. The derailment coefficient and wheel unloading rate peak value under the loading and running conditions are all going up with the height rising of gravity center of loaded vehicle. This paper gives a feasible method for the further study on vehicle dynamic characteristics in railway goods transportation.

Vibration Simulation of Articulated Dump Truck with the Variation of Longitudinal Center of Gravity Position of Rear Sprung Mass and Rear Suspension Stiffness

The paper is concerned with the vibration for the articulated dump truck (ADT) which is multi-axle vehicle and different from rigid dump truck. The balanced suspension was employed as the rear suspension in the 60t ADT which the paper takes as the research object. A vibration model of 6 dof for the truck was proposed. The impact of the variation of longitudinal center of gravity position of rear sprung mass and rear suspension stiffness on vibration was investigated in stochastic excitation of the truck in the frequency domain. It is found that it is beneficial to the comfort of the truck when the center of gravity of the sprung mass moves forward and the impact of rear sprung stiffness on vibration is not too great. The results of the vibration for the truck are provided for the design of the 60t ADT.

Global aircraft aero-propulsive linear parameter-varying model using design of experiments

In this paper, applicability of modeling global aircraft aerodynamic-propulsive coefficients using a design of experiments technique based on a linear parameter-varying model is investigated. The proposed technique consists of a local estimation phase and a global identification phase. For the local estimation phase, a set of multiple orthogonal phase-optimized multi-sine inputs (elevator, aileron, rudder, and throttle) is executed at different locations over the operational flight envelope. The resultant aircraft responses are used to estimate the equivalent stability and control derivatives at each flight condition. Design of experiments is then employed to globally identify the stability and control derivative variations with velocity, altitude, aircraft mass, and center of gravity position. A sequential experiment using a factorial design and augmented face central axial points was employed to model the variation. For demonstrating technique feasibility, a nonlinear simulator for an F-16 was used to assess the proposed approach. The validity of the proposed method was evaluated by comparing the aircraft response based on the proposed aerodynamic-propulsive model with the actual model. The proposed technique has the capability to deliver a model for a computationally complex and large envelope aerodynamic-propulsive airframe system.

Predictions of porpoising inception for planing vessels

The inception of porpoising is theoretically predicted for planing vessels. Two different approaches are presented. First, a linear stability analysis is applied to find the porpoising limits while the hydrodynamic coefficients, i.e. added mass and damping coefficients, are determined by either a simplified method or a numerical method. Another approach is to seek the porpoising limits by performing nonlinear time domain simulations. Either the simplified method or the numerical method is used in the simulations. In the numerical method, a 2D+t theory together with a boundary element method is employed. The trim angle limits for porpoising are determined by changing the longitudinal position of the centre of gravity (COG) of the vessel and keeping the forward speed constant. The predicted porpoising limits are compared with Day and Haag’s (Planing boat porpoising, Thesis, Webb Institute of Naval Architecture, 1952) experimental results. The influences of parameters such as the load coefficient, the vertical position of COG and the radius of gyration of the ship are investigated by varying those parameters in the linear stability analysis. In the nonlinear time-domain simulations, by trying different longitudinal position of COG, one can find the critical trim angle when the porpoising commences. The obtained trim limits agree generally with those predicted by the linear stability analysis. Bounded oscillations for the unstable cases near the critical trim angle can be seen in the time-domain simulations due to the nonlinear effects.

New helicopter model identification method based on flight test data

AbstractA helicopter model has been identified and validated for flight conditions defined by altitudes, speeds, loadings and centre of gravity positions. To identify the helicopter models, 2-3-1-1 multistep control inputs were performed by the pilot to excite all helicopter modes. Then, each estimated signal has to remain in tolerance margins defined by the Federal Aviation Administration. Three methods were used to observe the system outputs from its states: a fuzzy logic method, a linear method optimised with a neural network algorithm and a classical method. Because of random effects when gathering data, classical method did not give good enough results. The fuzzy logic method was not robust enough so that output plots showed peaks that could be felt by the pilot. Then, because the model could be implemented in a simulator for the pilot training, the pilot feedback is very useful in order to compare the reality with the results of the mathematical model. When the outputs are obtained from the measured state variables, the linear method gave the best results.

Online Estimation of Vehicle Inertial Parameters for Improving Chassis Control Systems

AbstractVehicle chassis control systems aim at increasing vehicle safety and performance, while ensuring superior passenger comfort. Nearly all control algorithms are sensitive to the inertial parameters of a vehicle. As the vehicle mass, the moments of inertia, and the centre of gravity (COG) position can change significantly during operation, an accurate online estimation of these properties could substantially improve the performance of an active system. This paper presents an innovative algorithm for the online estimation of the inertial parameters of a road-vehicle. Using low-frequent suspension displacement signals and suspension stiffness characteristics, the vehicle mass and horizontal COG position are estimated. A Monte Carlo method determines the most probable mass distribution. Based on the assigned passenger weight, anthropometric data sets allow to calculate the inertial properties of every passenger, eventually resulting in the inertial parameters of the complete, loaded vehicle. The accuracy of the proposed algorithm is validated by means of a test campaign on an accurate kinematics and compliance testrig.

Golf Clubs and Golf Club Heads Having Feel Altering Systems

Golf club heads include: (a) a body having a ball-striking face and a rear face, the body defining a cavity; (b) a bridge member extending across the cavity, wherein the bridge member is provided to affect, at least in part, a position of a center of gravity of the club head; and (c) a feel altering element provided between the bridge member and the rear face. The feel altering element may affect a wide variety of parameters that relate to the “feel” of the golf club head when it strikes a golf ball, such as the sound produced by the club head during the strike, the vibrational response of the club head during the strike, the swing characteristics of the club head (e.g., weight, center of gravity position, etc.), and the like.