Modeling and simulation of revolute joint with clearance in planar multi-body systems

Xupeng Wang,Geng Liu 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.10

An improved nonlinear elastic-damping contact force model, based on accounting for the axial dimension of bearing and journal, energydissipation during contact process and the nonlinear power exponent from material, is established to evaluate the contact force ofrevolute joint with clearance. The friction effect was also determined using the modified Coulomb friction model. Numerical simulationwas carried out to discuss the influence of clearance size on the kinematic and dynamic characteristics of the planar slider-crank mechanism,which has a clearance joint between the connecting rod and slider. The numerical results point out that the existence of joint clearancecauses high peaks on the kinematic and dynamic system’s characteristics. Even if the clearance size is small, it also causes obvioushigh frequency shaking of the slider acceleration, joint reaction force and the crank moment.

Effects of restitution coefficient and material characteristics on dynamic response of planar multi-body systems with revolute clearance joint

Xupeng Wang,Geng Liu,Shangjun Ma,Ruiting Tong 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2

To study the effects of restitution coefficient and material parameters on the dynamic characteristics of planar multi-body systems with revolute clearance joints, a comprehensive methodology for clearance revolute joints in a planar multibody system is presented and analyzed. A new nonlinear contact force model, which accounts for the axial length of bearing and has a wide suitable range of impact situation, is presented to evaluate the contact force between journal and bearing. Furthermore, a modified Coulomb friction force model also presented to consider the effect of friction in clearance joint. Then, a typical journal-bearing model and a planar slider-crank mechanism has revolute clearance joint are used as examples. From the main numerical results under the different restitution coefficient and material parameters, it can be concluded that coefficient of restitution has significant effects on dynamic response of multi-body systems with revolute clearance joint. Additionally, materials of journal and bearing with smaller Young’s modulus will cause obvious delay on dynamic response of multi-body systems.

Dynamic analysis of planar mechanical systems with clearance joints using a new nonlinear contact force model

Xupeng Wang,Geng Liu,Shangjun Ma 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.4

We investigated the dynamic behavior of planar mechanical systems with clearance joints. First, the contact effect in clearance joint was studied using a new nonlinear contact force model, and the rationality of this model was verified by the results of numerical simulations, which are based on a journal and bearing contact model. Then, the dynamic characteristics of a planar slider-crank mechanism with clearance were analyzed based on the new nonlinear contact force model, and the friction effect of clearance joint was also considered using modified Coulomb friction model. Finally, the numerical results of the influence of clearance size on the acceleration of slider are presented, and compared with the published experimental results. The numerical and experimental results show that the new nonlinear contact force model presented in this paper is an effective method to predict the dynamic behavior of planar mechanical system with clearance joints, and appears to be suitable for a wide range of impact situations, especially with low coefficient of restitution.

Dynamic and motion consistency analysis for a planar parallel mechanism with revolute dry clearance joints

Bicai Xu,Xupeng Wang,Xiaomin Ji,Ruiting Tong,Yanmin Xue 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.7

The aim of the research was to introduce a methodology for dynamic response and motion consistency research on multibody system with multiple revolute clearance joints. An improved impact force model and a modified friction force model were introduced to evaluate the effects of impact and friction in clearance joints. A planar parallel mechanism which has two clearance joints in the left wing and the right wing was also used as an example. From the results based on different conditions, clearance has slight influence on the angular displacement and angular velocity, but obvious effect on angular acceleration. And with same clearance values of left wing and right wing, the motion consistency of the parallel mechanism is very good, which means the dynamic response of two wings is almost symmetrical. When the two clearance joints have different clearance values, the motion consistency and relative error between two wings are much obvious, especially the angular acceleration.

CenterNet Based on Diagonal Half-length and Center Angle Regression for Object Detection

Yuantian Xia,XuPeng Kou,Weie Jia,Shuhan Lu,Longhe Wang,Lin Li 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.7

CenterNet, a novel object detection algorithm without anchor based on key points, regards the object as a single center point for prediction and directly regresses the object’s height and width. However, because the objects have different sizes, directly regressing their height and width will make the model difficult to converge and lose the intrinsic relationship between object’s width and height, thereby reducing the stability of the model and the consistency of prediction accuracy. For this problem, we proposed an algorithm based on the regression of the diagonal half-length and the center angle, which significantly compresses the solution space of the regression components and enhances the intrinsic relationship between the decoded components. First, encode the object’s width and height into the diagonal half-length and the center angle, where the center angle is the angle between the diagonal and the vertical centreline. Secondly, the predicted diagonal half-length and center angle are decoded into two length components. Finally, the position of the object bounding box can be accurately obtained by combining the corresponding center point coordinates. Experiments show that, when using CenterNet as the improved baseline and resnet50 as the Backbone, the improved model achieved 81.6% and 79.7% mAP on the VOC 2007 and 2012 test sets, respectively. When using Hourglass-104 as the Backbone, the improved model achieved 43.3% mAP on the COCO 2017 test sets. Compared with CenterNet, the improved model has a faster convergence rate and significantly improved the stability and prediction accuracy.

Analysis and research on dynamic characteristics of 3D braided composite two-stage reducer case

Weiliang Zhang,Xupeng Wang,Xiaomin Ji,Xinyao Tang,Fengfeng Liu,Shuwei Liu,Mingjun Liu,Xiao-Long Gao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

Based on the analysis of the movement rule of 3D five-way braided yarn, the 3D five-way braided case model is divided into three parts: base, case bottom plate and case wall. According to the characteristics of each part, the braiding and forming principle of a 3D five-way composite case was analyzed. Under the assumption of ignoring the influence of friction, bearing and other factors on the system, the differential equations of motion of the two-stage gear transmission system with case were established. The two-stage gear transmission system was numerically analyzed by Euler method, and the influence of dimensionless meshing frequency, clearance, case mass and damping on the dynamic characteristics of the transmission system was studied. After that, high and low frequency disturbance was applied to the input case. The research shows that the damping ratio of the composite case increases and the low frequency attenuation is accelerated due to the decrease of the case mass, so the composite case has better shock resistance to low frequency interference.