Load Moment Research Articles

토크 및 모멘트부하의 영향을 고려한 로봇 관절의 마찰 모델

로봇 관절에서 발생하는 마찰은 제어시스템에 외란으로 작용하여 제어성능을 악화시키는 요인으로 작용한다. 따라서 대부분의 로봇에서는 마찰 모델을 기반으로 추정한 마찰토크를 제어입력에 반영하여 마찰을 보상하며, 마찰 모델이 정확할수록 로봇의 제어성능을 향상시킬 수 있다. 본 연구에서는 로봇링크의 하중에 의해서 발생하는 토크부하와 모멘트부하의 영향으로 다르게 발생하는 마찰 거동을 파악한다. 이를 통해 기존의 쿨롱마찰과 점성마찰로 구성된 마찰 모델에 토크부하와 모멘트부하의 영향을 고려한 항을 추가하여 보다 정확한 마찰 모델을 제안한다. 제안한 마찰 모델은 7자유도 협동로봇에 적용하여 실험을 통해 성능을 검증하였다.

Biomechanical comparison of semirigid junctional fixation techniques to prevent proximal junctional failure after thoracolumbar adult spinal deformity correction

BACKGROUND CONTEXTAdult spinal deformity patients treated operatively by long-segment instrumented spinal fusion are prone to develop proximal junctional kyphosis (PJK) and failure (PJF). A gradual transition in range of motion (ROM) at the proximal end of spinal instrumentation may reduce the incidence of PJK and PJF, however, previously evaluated techniques have not directly been compared. PURPOSETo determine the biomechanical characteristics of five different posterior spinal instrumentation techniques to achieve semirigid junctional fixation, or “topping-off,” between the rigid pedicle screw fixation (PSF) and the proximal uninstrumented spine. STUDY DESIGNBiomechanical cadaveric study. METHODSSeven fresh-frozen human cadaveric spine segments (T8–L3) were subjected to ex vivo pure moment loading in flexion-extension, lateral bending and axial rotation up to 5 Nm. The native condition, three-level PSF (T11–L2), PSF with supplemental transverse process hooks at T10 (TPH), and two sublaminar taping techniques (knotted and clamped) as one- (T10) or two-level (T9, T10) semirigid junctional fixation techniques were compared. The ROM and neutral zone (NZ) of the segments were normalized to the native condition. The linearity of the transition zones over three or four segments was determined through linear regression analysis. RESULTSAll techniques achieved a significantly reduced ROM at T10-T11 in flexion-extension and axial rotation relative to the PSF condition. Additionally, both two-level sublaminar taping techniques (CT2, KT2) had a significantly reduced ROM at T9-T10. One-level clamped sublaminar tape (CT1) had a significantly lower ROM and NZ compared with one-level knotted sublaminar tape (KT1) at T10-T11. Linear regression analysis showed the highest linear correlation between ROM and vertebral level for TPH and the lowest linear correlation for CT2. CONCLUSIONSAll studied semirigid junctional fixation techniques significantly reduced the ROM at the junctional levels and thus provide a more gradual transition than pedicle screws. TPH achieves the most linear transition over three vertebrae, whereas KT2 achieves that over four vertebrae. In contrast, CT2 effectively is a one-level semirigid junctional fixation technique with a shift in the upper rigid fixation level. Clamped sublaminar tape reduces the NZ greatly, whereas knotted sublaminar tape and TPH maintain a more physiologic NZ. Clinical validation is ultimately required to translate the biomechanics of various semirigid junctional fixation techniques into the clinical goal of reducing the incidence of proximal junctional kyphosis and failure. CLINICAL SIGNIFICANCEThe direct biomechanical comparison of multiple instrumentation techniques that aim to reduce the incidence of PJK after thoracolumbar spinal fusion surgery provides a basis upon which clinical studies could be designed. Furthermore, the data provided in this study can be used to further analyze the biomechanical effects of the studied techniques using finite element models to better predict their post-operative effectiveness.

Flexural behaviour of cover plated CFS built-up beams composed of lipped channels: Comparison of test and design strengths

Built-up members are efficient in developing adequate resistance against large load demands, and their efficiency largely depends on how adequately the built-up sections are designed. This paper discusses the flexural behaviour of cover plated cold-formed steel (CFS) built-up beams made up of lipped channels. Lipped channels were placed at an adequate distance in the back-to-back arrangement and were connected at the flanges with self-drilling screws by means of cover plates, on both the tension as well as the compression faces. Simply supported end conditions were adopted in all the specimens. Both three-point loading as well as four-point loading was considered to study the influence of moment gradient and constant moment loading of theses built-up beam specimens. The sectional compactness of the channel section and the aspect ratio of the built-up section were varied to assess the behavioural effect in the specimens with respect to the variations incorporated. This study deals with the tests conducted to generate the test data. Prior to the testing of the specimens, tensile coupon tests were carried out as per the relevant standards to acquire the actual material properties of the steel used for the specimen fabrication. Both the European code as well as the North American Standards were used for developing the theoretical strengths and were compared with the test results.

Effects of shear reduction shoes on joint loading, ground reaction force and free moment across different cutting angles

ABSTRACT This study examined the effects of shear reduction shoes on braking and propulsion ground reaction forces (GRFs), free moments, and joint moments when cutting towards different directions. Fifteen male university basketball players performed sidestep cutting towards 45°, 90° and 135° directions with maximum-effort in shear reduction and control shoes. Two-way (angle x shoe) ANOVAs with repeated measures were performed to determine the interaction and main effects of cutting angle and shoe for all tested variables. Results showed that cutting angles had significant influence on most of the variables, except for the peak-free moment, peak ankle eversion moment and maximum loading rate of resultant shear GRF. The shear reduction shoes significantly delayed the timing to the first peaks of vertical and resultant shear GRFs compared with the control shoes. During propulsion, the shear reduction shoes generated smaller peak propulsion resultant shear and vertical ground reaction forces. Additionally, the shear reduction shoes did not induce distinct frontal and transverse moments at the ankle and knee joints compared with the control shoes. These results suggest that the application of shear reduction structure could be beneficial to attenuate vertical and shear impact peaks, offering additional insights to reduce shear-related injuries.

Numerical and experimental analysis of the effect of elastic membrane on liquid sloshing in partially filled tank vehicles

A numerical analysis for fluid-membrane interaction is conducted to investigate fluid slosh within a partially filled horizontal cylindrical tank with an elastic membrane restraining the free surface. The fluid-membrane interaction analysis is performed to investigate the effect of membrane on liquid slosh responses in terms of liquid load shifts, slosh forces, moments and slosh frequency. A series of experiments were conducted on a scaled horizontal cylindrical tank with an elastic membrane-like restraint under harmonic acceleration excitations in longitudinal or lateral direction. The validity of the numerical model is demonstrated using the laboratory-measured data. The validated model is subsequently formulated for a full scale tank and analysis are performed under excitations idealizing the straight-line braking or turning maneuvers to investigate the antislosh effectiveness of membrane. It is shown that the addition of membrane can yield substantial reduction in slosh amplitude and thus the pitch and roll moment; the slosh frequency can be substantially shifted to higher values to avoid resonance in partly filled tanks.

Combining LIDAR and LADRC for intelligent pitch control of wind turbines

At present, most of the pitch control methods are based on PI controller, the pitch control system has poor disturbance resistance, and the research of variable parameter feedforward based on Light detection and ranging (LIDAR) and the Linear Active Disturbance Rejection controller (LADRC) composite control is rarely studied to reduce the blade root load, so this paper conceives a hybrid intelligent and adaptive pitch control approach to reduce a wind turbine generator speed fluctuation and its blade root load. Specifically, we combine the Radial Basis Neural Network and Finite Impulse Response filter (RBFNNFIR) based on LIDAR wind measurement. We then use a variable bandwidth of LADRC controller. Overall the approach enables and facilitates self-adaption and self-adjustment. We use Matlab s-function to call the multi-freedom mathematical wind turbine model based on FAST code, the composite intelligent control algorithm is established in Simulink. Initial results from the statistical analysis of the experiments under different turbulent wind conditions shows that the hybrid intelligent pitch control approach can reduce the generator speed fluctuation by about 40.8%, and the blade root max value of load moment by about 13.1%, compared with the baseline values of the traditional variable gain PI control algorithm.

Characterization and nonlinear models of bending extensile/contractile pneumatic artificial muscles

Pneumatic artificial muscles (PAMs) are compliant fluidic actuators, usually consisting of a tubular bladder, a braided sleeve and end fittings. PAMs have been studied extensively by researchers; however, most previous researches are focused on the axial PAMs. Herein, a pair of nonlinear models were developed based on the principle of virtual work and the force balance analysis. And the two models are applicable to both bending extensile PAMs (BE-PAMs) and bending contractile PAMs (BC-PAMs). In this study, a cyclic bending moment loading experimental method were proposed and conducted with BE-PAMs and BC-PAMs to characterize their deformation and actuation performance and draw their overall relationships of actuation moment to bending curvature and inner pressure. With the experimental results, the validation analysis was carried out to demonstrate the validity of the two models. The energy model can get higher accuracy, while the force balance model could provide more details of the interior and interaction stress conditions. The combination of both can promote the comprehension of non-axial bending PAMs. Moreover, two three-finger soft grippers and a humanoid hand based on BE-PAMs and BC-PAMs were built and tested to investigate their performance on gripping objects. The BE-PAM gripper showed more accommodative gripping performance, whereas, the BC-PAM gripper owned higher gripping force. The humanoid hand combining the merits of both showed excellent flexibility, adaptability and decent load capability in gripping object with various sizes, shapes and materials.

A comprehensive study on the off-diagonal coupling elements in the stiffness matrix of the angular contact ball bearing and their influence on the dynamic characteristics of the rotor system

This paper not only presents the details of the composition form and classification method of the elements in bearing stiffness matrix, but also reveals the effects of the off-diagonal stiffness items in bearing stiffness matrix on the rotor dynamic characteristics. First, the complete expression of bearing stiffness matrix is derived based on the improved model of ball bearing, and the change rules of the different categories of the stiffness elements with the rotating speeds and loads are given. Then, both the quantitative and qualitative analysis methods for the rotor-bearing systems supported by a pair of the angular contact ball bearings are presented, and the effects of the off-diagonal bearing stiffness elements on the rotor supporting stiffness and natural frequencies are given and discussed. The results show that, when the rotor system is subjected to a radial load or moment load, the additional loads from ball bearings are generated due to the off-diagonal stiffness elements in bearing stiffness matrix, and the rotor with the O-configuration has higher supporting stiffness and resonance frequencies than the rotor with the X-configuration.

Seismic behaviour of RC jacketed columns under different axial loads

This study examines the flexural performance of reinforced concrete (RC) columns strengthened through a seismic jacket technique developed using a prefabricated steel bar unit that forms peripheral closed hoops and supplementary V ties, satisfying the design requirements of the ACI 318-14 seismic provisions. Three RC jacketed columns were prepared with a parameter of axial load levels and tested under a constant concentric axial load and cyclic lateral loads. Analytical approaches were also applied to examine the axial load–moment interaction of the RC jacketed columns when considering the confinement effect provided by the jacket section and to investigate the applicability of the previous performance-based design models proposed for virgin seismic columns. The test results show that the developed jacket technique possesses a good potential in enhancing the flexural stiffness, strength and ductility of deficient columns, even under a high axial load. Reinforced concrete jacketed columns possess a higher ductility than that estimated using the ductility parameter model, regardless of the axial load level. Thus, the jacket section including the seismic details of a transverse reinforcement can be conservatively designed, based on the axial load–moment interaction and ductility parameter model for the moment and ductility enhancements required by deficient columns.

Three-Dimensional Modeling of Monopiles in Sand Subjected to Lateral Loading under Static and Cyclic Conditions

Here, the results of a three-dimensional finite element study of the complex interaction of horizontal and moment loads (HM) on offshore monopiles as failure envelope, are reported. A new design criterion is described which is based on critical length, ultimate limit states, load characteristics and Eigen-frequency to ensure stable behavior of laterally loaded monopiles. Numerical analyses were performed to examine nonlinear interaction of a soil-pile system for 10,000 load cycles. The resulting framework can predict angular rotation due to cyclic loading. According to the loading level and duration of a load, elastic strains accumulate in the vicinity of a pile. Fairly intermediate two-way cyclic loading induced the largest rotations irrespective of the analysis performed (i.e., drained versus partially drained). Based on the regression coefficients of the non-dimensional frameworks used, accumulating rocking deformations of a pile at seabed level appear to be dependent on cyclic load ratio, drainage condition, and duration of loading. For safe design, sensitivity of the natural frequency of offshore wind turbine (OWT) at a monopile critical length as well as shorter lengths were also examined. The analytical model proposed here for determining the natural frequency of an OWT considers that soil-structure interaction (SSI) can be represented by monopile head springs characterized by lateral stiffness, KL, rotational stiffness, KR, cross-coupling stiffness, KLR, and parabolic soil stiffness variation with depth.

Shear strength evaluation in the existance of axial compressive loads for reinforced concrete beams

ABSTRACT Response-2000 is a program developed to calculate the shear capacities of beams and columns under any combinations of shear, moment, and axial loads. It is based on the modified compression field theory. The capabilities of the program Response-2000 to obtain shear strength capacities in the existence of axial compressive loads are demonstrated. The comparison with the experimental tests proved that the program gives good estimate for the failure shear in this case. The shear provisions of the Egyptian reinforced concrete code (ECP203-2017) are also evaluated against the experimental results. It is found that the accuracy of the obtained results using Rseponse-2000 is better than those obtained using the shear equations of the Egyptian reinforced concrete code (ECP203-2017). The program Response-2000 is then used to generate 336 results for 7 different cross-sections considering different concrete compressive strengths, transverse reinforcement, and values of axial loads. These generated results along with 33 experimental results for other 7 cross-sections are used to develop a new formula for the shear strength capacity in the existence of axial compressive loads. This formula is found to give better results when verified against experimental data.

Multidisciplinary design of the wing for aircraft preliminary design purposes

In this paper, an aerodynamic and wing structure is investigated by low-fidelity methods. Bell-shaped lift distribution was rediscovered in the last decade as a perspective alternative to traditional wing design. This leads to lower aerodynamic drag than elliptical lift distribution for a given lift force and root bending moment. Root bending moment is used as a surrogate model of wing structure weight. It is relatively raw simplification introduced by Prandtl to estimate the weight of the spar as a main part of the wing structure. For a more accurate wing weight estimation, the main parts of the wing are dimensioned under CS-23 regulation in this work. The design procedure starts with defining the elementary parameters of the wing shape (chord/twist distribution, wingspan). After geometry generating a non-linear lifting line is used to calculate aerodynamic characteristics for all regime, determined from the flight envelope. The dimensions of a spar, ribs and skin are calculated in the next step of the procedure for given bending moment, load and torque moment distribution. The structure of the wing is assumed as a two-spar, manufactured by aluminum. A target of design is to find out the shape of the wing for given weight. The solution is verified by CFD calculation.

FLEXURAL CAPACITY OF CONCRETE BEAMS REINFORCED WITH HIGH-STRENGTH STEEL BARS UNDER MONOTONIC LOADING

This paper presents the flexural capacity of reinforced concrete beams designed with high-strength steel bars. Reinforced concrete beams with steel bars fy = 550 MPa are designed to have flexuralstrength like beams with steel bar fy 420 MPa. According to ACI 318M-19, the high-strength steel bars (fy =550 MPa) are allowed to use as the reinforcing steel, which previously unpermitted. This study was conductedto represent the possibility of using high-strength steel bars as reinforcement. There are five sample beams thatdesign with various diameters (13 and 19 mm) and strength (fy 420 and 550 MPa) of longitudinal reinforcement.These beams were placed on two simple supported and undergo monotonic loads at two points-load. It isreviewed the flexural capacity of beams with high-strength steel bars involve load capacity, moment, and beamdeflection. Also, the behavior of beams when receiving loads in terms of the relationship between load anddeflection. Based on the research, beams with a high-strength steel bar can accept higher loads than normalbeams by a difference of about 16-18%. While at the same deflection condition, which is 100 mm, beams withhigh strength reinforcement can achieve a higher load of around 18 percent. Beam with high-strength steel barsshowed flexural behavior that was not much different from the normal-strength steel bars because it did notshow brittle collapse. It proves that high-strength steel bars can be used on reinforced concrete structuralelements if it satisfies the requirements specified in the code.

Lateral bearing capacity analysis of pile foundation using a spring modelling system

Pile foundations are often required to resist lateral loads and moments in addition to their primary use as axially loaded members. The interaction between material strength of axial, moment and shear against load capacity and soil interaction is the most important factors in the pile analysis. This study aims to obtain the lateral bearing capacity of pile foundation using a spring modelling system which will be calculated manually for the Kv spring constant in the vertical direction and the kh coefficient in the horizontal direction using the Nakazawa method and SAP 2000 v14.2.5 program. The result shows that the maximum shear load and the maximum axial tensile load received by the pile is still within the allowable shear load and allowable axial tensile load capacity resulting from the manual calculation. However, the maximum axial compression load and maximum moment is exceeded its each allowable capacity. Hence, it is necessary to re-modelling by adding the depth or number of piles.

A CSM-CFD methodology applied to the design of a cryogenic WT model

The Aero-structural coupled analysis presented in this work represents an important part of the PRODIGE project, whose main purpose is the prediction of aerodynamics and hinge moment loads of the aileron of a scale model of business jet at transonic Mach numbers and flight Reynolds number. More in details, this methodology supports the design activities of the cryogenic wind-tunnel (WT) model to be tested in the European Transonic Wind tunnel (ETW). The need to implement such a kind of analysis comes from the requirement to take into account the “pure aeroelastic effect” during experimental tests and need to understand the effect of the WT model flexibility on the control surface load prediction, prior to and in parallel with the balance design. CFD evaluations are performed on the whole model, while a static Fluid-Structure-Interface (FSI) procedure is set up and, only, applied to the wing and aileron of the model. The FSI cycle is made of two blocks: a CFD evaluation part and a CSM evaluation part. Both modules are coupled within an iterative loop, where information are exchanged between them. Two angles of incidence are taken into account, i.e. the lowest value (α=-3°) and the highest one (α=6°). Results will be compared in terms of global aerodynamic forces and pressure coefficient distributions. Moreover the new deformed shapes derived from the application of both approaches will be compared with the original one.

Task Planning of Manipulator Based on Dynamic Space Constraint and Torque Sensor

It is a main direction of industrial application that manipulator performs grasping task in task space and combines obstacle avoidance planning. This paper presents an improved RRTConnect path planning algorithm IRRTC based on dynamic constrained space and admittance control. The sliding constraints on the Cartesian position space is used to search for the reachable path of the traction robot by the algorithm. For orientation control, a priori path is formed by artificially given constraint interval, and then the dynamic admittance control is modified by using the end grasping load moment estimated by the joint torque sensor of the manipulator as the constraint. At the same time, the algorithm designs a local escape algorithm based on the current state and target state of the robotic arm, which overcomes the problem that the traditional RRTConnect and RRT cannot escape the local minimum. The simulation and experimental results of the Xmate3 redundant manipulator show that a feasible path can be quickly searched based on constraints and local escape strategies, and a relatively optimal trajectory can be planned based on the original path by the optimized path and also meet the constraints. Within 3S, the average planning success rate is increased to over 90%, and without time constraint, the success rate is 100%, the efficiency is higher than other algorithms. Because the admittance control is used in conjunction with the joint torque feedback to maintain the dynamic correction of the end orientation, which improves the stability of the manipulator. The algorithm can be artificially designed to solve the obstacle avoidance and task constraints in disorderly grasping.

ЖИВУЧЕСТЬ РАМНО-СТЕРЖНЕВОГО ЖЕЛЕЗОБЕТОННОГО КАРКАСА ЗДАНИЯ В ЗАПРЕДЕЛЬНЫХ СОСТОЯНИЯХ

A methodology and an algorithm for calculating the survivability parameters of a long-term deformable reinforced concrete building frame in extreme states are presented. Analytical dependencies for determining the value of the creep measure are taken in accordance with the use of approximate dependencies from the recommendations of the NIIZHB. On this basis, a method is proposed for determining the cross-section bending stiffness of the frame elements. The deformation criterion of a special limiting state is formulated taking into account the nonequilibrium processes of prolonged deformation of the structural system elements. The numerical analysis results of the long-term deformable reinforced concrete frame survivability potential with a sudden removal of the one structural element, taking into account the long-term deformation prehistory of the considered building frame under an operating load, are presented. The exposure of the structural system survivability from the its loading moment to its transformation into a kinematically variable system has been determined.

Numerical-Experimental Analysis of Polyethylene Pipe Deformation at Different Load Values.

Polymer pipes are used in the construction of underground gas, water, and sewage networks. During exploitation, various external forces work on the pipeline, which cause its deformation. In the paper, numerical analysis and experimental investigations of polyethylene pipe deformation at different external load values (500, 1000, 1500, and 2000 N) were performed. The authors measured strains of the lower and upper surface of the pipe during its loading moment using resistance strain gauges, which were located on the pipe at equal intervals. The results obtained from computer simulation and experimental studies were comparable. An innovative element of the research presented in the article is recognition of the impact of the proposed values of the load of polyethylene pipe on the change in its deformation.

Structural Analysis of Yoke Part in Design of Driveshaft

Driveshaft used for transmitting torque and rotation, is one of the most important components in motor vehicles. It is required to connect the other components of the drivetrain such as transmission and differential to each other. Basically, comprises of one or more universal joints, yoke parts, splined parts and sometime center support bearing. Each compo-nent on it performs different functions such as angular and axial move-ment. Every component on driveshaft are subjected to torsion and shear stress. Thus, in the design and analysis processes each component should be sufficiently strong against to these all. In this study, numerical and an-alytical methods to design the weld yoke, were investigated and com-pared with each other. In the numerical studies finite element analysis (FEA) implemented by using two different loading conditions, force cou-ple and moment. And the strength formulas were used in the scope of an-alytical method. As a result of the study, the stress on critical section ob-tained from FEA, supports the results from analytical method. Thus, ana-lytical method can be used for the weld yoke design and the FEA can be implemented by using any of force couple or moment as loading type.

Estimation of mechanical parameters for orthodontic retraction loops using finite element analysis

Abstract Forces and moments are the main parameters deciding the safety of many of the engineering as well as biomaterials. Since every material has certain yield or ultimate strength, it is always desirable to work in the safe limits to maintain the integrity of the systems. In the present analysis, five standard loops used in the orthodontic applications (T-Loop, Vertical Loop, Opus70, Mushroom and Helix) were analysed using finite element analysis for a fixed horizontal length of 14 mm and a vertical height of 10 mm. Analysis is carried out using 3D beam elements with an element size of 0.25 mm as the accuracy of finite elements are mainly based on element size. For all the analysis, the load deflection rate, vertical force generation and moment values are recorded with carried out in the nonlinear domain to capture the results better. The results shows that minimum force and moment development when the loop is positioned at centre. It is positioned near any bracket, maximum forces and moments are create near the activation bracket. Higher the elastic modulus, the wire is inducing higher moments and forces which are key to the stability of the orthodontic structure. Finite element analysis is effectively used to estimate the load deflection rate, force and moment generation based on different types of loops, positions and materials.