Multiple Clearance Joints Research Articles

Rigid-flexible coupling dynamic modelling and dynamic accuracy analysis of planar cam four-bar mechanism with multiple clearance joints

Combination mechanism of conjugate cam and four-bar is a complex type of multi-body system, in which the coupling problems such as cam profile law, flexible deformation of connecting rods, and multiple joint clearance collision make it difficult to model and optimise its dynamics. Just as the beating-up mechanism of high-speed rapier looms for multi-layer weaving is a representative conjugate cam four-bar mechanism. In response to the current development of textile machinery in the direction of high-speed and precision, and in order to improve the work efficiency and operational accuracy of the conjugate cam four-bar beating-up mechanism, the following work is done for the purpose of taking into account the multi-joint clearance and the flexible rod based on the mechanism. Firstly, based on Kane's equation, a multi-body dynamic model with multiple clearances is established combined with clearance collision theory. Secondly, a dynamic model of a rigid-flexible coupling system with multiple revolute clearances is established using finite element method combined with modal synthesis technology. Subsequently, the variables separation method and mode superposition method are used to solve the dynamic equations of the coupled system. Finally, numerical examples are used to analyse the effects of clearance quantity, clearance size, mode truncation order, cam speed, and component material properties on the dynamic response and accuracy of the system. The results show that, in the rotational speed range of 600–800 rpm, the dynamic performance of the system is little affected by the speed; Through comparative analysis of multiple materials, it is found that selecting carbon fibre composite materials has the smallest impact on the motion accuracy of the system. In this paper, the clearance collision model, finite element model and rigid-flexible coupling dynamic model are integrated, which are applied to the cam-linkage combined multi-body mechanism, and the dynamic problems of the actual machine are analysed and solved.

Dynamics Optimization Research and Dynamics Accuracy and Reliability Analysis of a Multi-Link Mechanism with Clearances

With the development of high-speed and lightweight mechanisms, and the continuous improvement of manufacturing accuracy requirements in industrial production, clearance joints have increasingly become one of the key factors affecting dynamics performance. Poor clearance will seriously compromise stability, accuracy, and dynamics performance. Based on a genetic algorithm, an efficient modeling methodology for the dynamics optimization of a planar complex multi-link mechanism containing multiple clearance joints is put forward. The model comprises a 2-degree of freedom (DOF) nine-bar mechanism that can be used as the main transmission mechanism of a hybrid drive multi-link press, which is taken as the research object. The optimization objective is to minimize the maximum acceleration of the slider and minimize the difference between the actual central trajectory and the ideal trajectory. By optimizing the quality parameters of key components, an optimal solution for the design parameters is obtained, and the effects of the different optimizations of the objective functions on dynamics response are compared and analyzed. At the same time, a new modeling and calculation methodology of the dynamics accuracy and reliability of a complex multi-link mechanism in terms of multiple clearances is proposed, and the effect of optimization on dynamics accuracy and the reliability of the mechanism is analyzed. Based on the optimization results obtained by taking the minimum difference between the actual center trajectory and the ideal trajectory as an optimization objective, the nonlinear characteristics before and after optimization are analyzed through a phase diagram and Poincaré map. A test platform was built to study the dynamics of the mechanism with clearances. Research not only provides a basis for the dynamics optimization of a multi-link mechanism containing clearances but also provides reference significance for the reliability analysis of a multi-link mechanism containing clearances.

A nonlinear dynamic characteristic modeling method of shift manipulator for robot driver with multiple clearance joints

A nonlinear dynamic characteristic modeling method of shift manipulator for robot driver with multiple clearance joints

Modeling and simulation for wear prediction in planar mechanical systems with multiple clearance joints

The main goal of this work is to develop a comprehensive methodology for predicting wear in planar mechanical systems with multiple clearance joints and investigating the interaction between the joint clearance, driving condition, and wear. In the process, an effective contact surface discretization method together with the Lagrangian method are used to establish the dynamic equation of the multibody system. Considering the change of the contact surface, an improved nonlinear contact force model suitable for the complicated contact conditions is utilized to evaluate the intrajoint forces, and the friction effects between the interconnecting bodies are discussed using the LuGre model. Next, the contact forces developed are integrated into the Archard model to compute the wear depth caused by the relative sliding and the geometry of the bearing is updated. Then, a crank slider mechanism with multiple clearance joints is employed to perform numerical simulations in order to demonstrate the efficiency of the dynamic procedures adopted throughout this work. The correctness of the proposed method is verified by comparing with other literature and simulation results. The results show that the wear is sensitive to different initial conditions, and the evolving contact boundary makes the dynamics of mechanical system and the joint wear prediction more complex. This study is helpful for predicting joint wear of mechanical systems with clearance and optimizing the mechanism’s design.

Dynamic Response and Chaotic Characteristics Analysis of Spatial Parallel Mechanisms with Multiple Spherical Clearance Joints

Dynamic Response and Chaotic Characteristics Analysis of Spatial Parallel Mechanisms with Multiple Spherical Clearance Joints

Parameter optimization for torsion spring of deployable solar array system with multiple clearance joints considering rigid–flexible coupling dynamics

In this paper, four novel evaluation indices and corresponding hierarchical optimization strategies are proposed for a deployable solar array system considering panel flexibility and joint clearance. The deployable solar array model consists of a rigid main-body, two panels and four key mechanisms, containing torsion spring mechanism, closed cable loop mechanism, latch mechanism and attitude adjustment mechanism. Rigid and flexible components are established by Nodal Coordinate Formulation and Absolute Nodal Coordinate Formulation, respectively. The clearance joint model is described by nonlinear contact force model and amendatory Coulomb friction model. The latch time, stabilization time, maximum contact force and impulse sum of the contact force of the solar array system are selected as the four novel evaluation indices to represent the complex dynamic responses of a deployable solar array with clearance joints instead of the lock torque widely used in conventional works. To eliminate the gross errors caused by the nonlinear and nonsmooth mechanical properties, a hierarchical optimization strategy based on an adaptive simulated annealing algorithm and a nondominated sorting genetic algorithm is adopted for the solar array system with clearance joints. Results indicate that the effects of panel flexibility on the evaluation index responses and design optimization of the solar array system cannot be neglected. Besides, increasing the weight factor of the stabilization time index of the rigid system may compensate for the differences in optimal results of the rigid–flexible coupling system. That may provide some references for optimization design of deployable space mechanisms considering clearance joints.

Kinematic accuracy and nonlinear dynamics of a flexible slider-crank mechanism with multiple clearance joints

Clearance joint appears in the multibody system and it could cause the uncertainty of motion. A general method for dynamic modelling and analysis of slider-crank mechanism with multiple clearance joints is presented and discussed in this work. The contact-impact characteristics of clearance joint are described by the nonlinear continuous contact force model. With flexible link taken into account, the dynamic characteristics of slider-crank mechanism with multiple clearance joints are analyzed based on the presented model. Then, the dynamic response of a flexible slider-crank mechanism is measured to clarify how to clearance joints can cause the vibration phenomenon of multibody system. Moreover, the stability and chaos analysis are conducted with the purpose of performing a parametric study, which quantifies the effects of clearance size and rotational speed on dynamic behavior of multibody system with multiple clearance joints. The numerical results indicate that the dynamic behavior of a flexible slider-crank mechanism depends on the characteristics of clearance joints.

Correlation dimension and bifurcation analysis for the planar slider-crank mechanism with multiple clearance joints

Joint clearance serves as a crucial element of nonlinearity in multibody systems. The quantization of the system chaos is conducive to not only the understanding of the nonlinear nature but the rationalization of system controlled parameters. In the present work, the system dynamics for the planar slider-crank mechanism with multiple clearance joints is depicted by the correlation dimension and bifurcation actions. Considering the obliqueness of the slider, the general configuration of the planar joint is proposed. Generalized coordinates and the Lagrangian approach are adopted to derive the dynamic motion equations. The effects of clearance size and driving speed on the bifurcations of the dynamic response are investigated. Furthermore, the fractal dimension of the strange attractor is identified by the correlation dimension from time series. Based on the Cao method, the Mutual Information (MI) function, and the Grassberger-Procaccia (G-P) algorithm, the controlled factors in the evaluation of correlation dimension are cautiously determined. Ultimately, the compound effect of translational and revolute clearance joints on the mechanism dynamics is featured. The numerical results testify that the correlation dimension of the slider displacement approximately saturates beyond a specific translational clearance value. Moreover, with the parameters used in this work, the complexity of system response seems to be more sensitive to the variation of translational clearance size than with the revolute joint.

Nonlinear dynamics analysis of shift manipulator for robot driver considering multiple revolute clearance joints and variable load

Clearance joints and variable load have a great influence on the dynamic performance of shift manipulator for robot driver. In this article, a dynamics model of clearance joint and a simulation method of variable load are proposed to analyze the influence of clearance joint and variable load on the dynamic performance of shift manipulator. Firstly, a hybrid nonlinear contact force model is established to describe the normal contact force of revolute clearance joint, and a modified Coulomb friction model is used to describe the tangential contact force of revolute clearance joint. On this basis, a virtual prototype dynamics model of shift manipulator with multiple revolute clearance joints is established. Then a power transmission model of shift manipulator including the variable load model at the end of shift manipulator is established. The time-varying and nonlinear characteristics of the load in gear engaging direction are simulated by neural network. Finally, the influences of different clearance dimension and variable load on the dynamic performance of shift manipulator are analyzed. Experiment and simulation results show the validity of the presented analysis, which provides a basis for further structure optimization of shift manipulator.

Research on Dynamic Characteristic of Rudder Transmission System with Multiple Clearance Joints

In order to meet the characteristics including small clearance, heavy load and large contact area of joints existed in rudder transmission system, a new normal contact force model is established, which is suitable for the large-area contact process and considers the coefficient of nonlinear variable stiffness as well as the axial length of bearing. The applicability of this model is verified by simulations under some conditions with different clearance size, restitution coefficient, initial collision speed and bearing's axial length. Furthermore, through the user-defined subroutine interface in ADAMS software, this modified contact force model is compiled and linked into the dynamic model of the rudder transmission system. The simulation results show that the dynamic response of the system with multiple clearance joints is not a simple superposition of that with one single clearance, and the dynamic interaction between these joints intensifies the oscillation and nonlinear characteristics of the system. This study provides a theoretical reference for the structural optimization and control strategy design of aircraft with clearance joints.

Study on the dynamic interaction of multiple clearance joints for flap actuation system with a modified contact force model

To analyze the effects of clearance joint number and dynamic interaction on responses of the flap actuation system, a dynamic analysis model is proposed based on a modified contact force model. The modified contact force model can take contact properties with small clearance, heavy load, large contact area and variable contact stiffness coefficient into consideration for the flap actuation system. Numerical results show that the actuation system presents violent fluctuation due to the dynamic interaction between multiple clearance joints, and the clearance joint closest to the input part suffers more serious contact effects. Furthermore, the combination motion modes between the multiple clearance joints are helpful to judge and analyze the motion state and dynamic behaviors of actuation systems. These simulation findings can provide a theoretical foundation for the optimization design, control strategy and engineering experiments of the actuation systems with multiple clearances.

Dynamics analysis of planar linear array deployable structures with multiple clearance joints

The purpose of this paper is to investigate the dynamic characteristic of the scissor linear array deployable structure under the coupling action of clearance joints, where the kinematic model of the deployable structure with clearance is established according to the principle of the motion between joint elements. The normal and tangential contact forces between contact components are respectively described using the Flores contact force model and modified Column friction model. In the sequel of this process, the impact forces between the connected components are converted to the mass centers of links connected by this clearance joint, and the converted contact force and additional torque were integrated to the generalized force in motion equations of the deployable structure, and then the effect of joint clearance is introduced to deployable syetem. The simulation results show that the dynamic characteristics of the mechanism are very sensitive to the clearance position, and the movement of a joint clearance will affect the movement of the other joint clearance, which shows that clearance joints in deployable structure have a strong dynamic interaction and all the joints should be modeled as real joints.

Dynamics Analysis of Spatial Mechanisms with Dry Spherical Joints with Clearance Using Finite Particle Method

The presence of clearance in a spherical joint makes the ball of the joint easy to collide with the socket, which causes additional dynamic effects on the motion of spatial mechanisms. The complexity of interaction between different clearance joints and that between a clearance joint and connected component requires an effective analysis method. In this paper, a practical method is proposed for evaluating the dynamic effects of spatial flexible mechanisms with multiple spherical clearance joints using finite particle method (FPM) combined with a clearance contact model. First, the equations of motion of the particles and internal force formulas of spatial beam elements in the discretized FPM model are derived, and the explicit generalized-[Formula: see text] method is adopted for time integration. Then, the contact state is detected based on the penetration depth, using the Lankanani–Nikravesh model to calculate the contact force and the Threlfall model to calculate the friction force during collision in the clearance joint. Specifically, a method considering the particle rotations is utilized to better evaluate the direction of the friction force. A spatial four-bar mechanism with spherical clearance joints is used to demonstrate the feasibilities of the proposed method. The effects of four parameters (i.e. clearance size, friction coefficient, multiple clearance joints, and bending stiffness) on the dynamic responses of the mechanism are fully investigated.

Investigation on Dynamic Interaction of Multiple Clearance Joints for Flap Actuation System

A dynamic simulation model of the flap actuation system is developed in this paper to analyze the dynamic interaction behaviours of multiple clearance joints. The nonlinear contact force model and modified Coulomb friction model are adopted in the four clearance joints to capture their motion modes, including free flight mode, impact mode and continuous mode. The results show that there exists a strong dynamic interaction between different clearance joints and one impact motion mode in a joint will immediately affect other joints. And when the system reaches a stable state, the four clearance joints almost appears the similar tendency due to the rigid connection. Therefore, in order to accurately predict the dynamic responses of multibody system, it is essential for all joints to be modelled as imperfect ones.

Dynamic analysis of a simplified flexible manipulator with interval joint clearances and random material properties

Flexible manipulator is an emerging technique in aerospace engineering, especially in the assembly, testing and maintenance of space stations. Dynamic analysis of a flexible manipulator with multiple clearance joints and hybrid uncertainties is a great challenge as compared to traditional flexible manipulator. To solve the problem, a dynamics model for a simplified flexible manipulator with interval clearance joints and random material properties was established. In this model, the Lankarani–Nikravesh contact force model was used to construct the clearance joint, while a combined feedforward–feedback control strategy based on a PID controller was applied to control the flexible manipulator. In addition, the clearance sizes and the Young’s moduli of the flexible parts were described by interval variables and random fields, respectively. To solve the dynamics model, a general methodology, based on the Karhunen–Loeve expansion and Kriging model, was presented. Finally, numerical examples were employed to demonstrate the validity of the proposed approach. The simulation results indicate that the joint clearance, the flexibility of the components and the uncertainties have great impacts on the kinematic accuracy and dynamic behaviors of the flexible manipulator, while hybrid uncertainties result in worse kinematic accuracy and more complex dynamic behaviors.

Wear Analysis of Spatial Parallel Mechanisms With Multiple Three-Dimensional Spherical Clearance Joints

The goal of this work is to investigate the dynamic responses of the parallel mechanism with irregular clearances caused by wear and to further reveal the influences of multiple clearance interaction on wear. The motion model and the force model of spherical clearance joint based on a continuous contact force model and a static friction model are established. The dynamic equation of the spatial parallel mechanism considering two spherical clearance joints is derived. A general wear analysis strategy to establish spherical clearance joint with sustainable updation of the surface profile is presented, and the dynamic responses of parallel mechanism after wear are studied. The interaction between two wear joints with different initial clearance values is further investigated. The results show that it is necessary to consider the factor of irregular clearances caused by wear in the analysis of dynamics behavior for precision mechanisms. Proper distribution of clearance values can reduce wear of clearance joint and improve the useful life of mechanism to a certain extent. This work provides a foundation for life prediction and reliability analysis of parallel mechanisms.

Dynamic Analysis of a Planar Hydraulic Rock‐Breaker Mechanism with Multiple Clearance Joints

Clearance exists in the joint of a mechanism because of the assemblage, manufacturing tolerances, wear, and other conditions, and it is a focus of research in the field of multibody dynamics. This study built a planar hydraulic rock‐breaker model with multiple joint clearances by combining the hydraulic cylinder model, the clearance joints based on the Lankarani–Nikravesh contact force model, and the Lagrange multiplier method. Dynamic simulation results indicated that multiple clearance joints can degrade the dynamic responses of a rock‐breaker model, which can be decomposed to rapid vibrations and slow movements. The rapid vibrations are excited by coupling the spring‐mass system of hydraulic cylinder and clearances. The effects of the clearance size, input force, damping coefficient, and friction on the dynamic behaviour of the rock‐breaker mechanism are also investigated. The friction could reduce the rapid vibration state significantly, which is feasible for practical engineering applications. As compared with the traditional models without clearances, the present model provides not only better predictions for the theoretical study of the hydraulic rock‐breaker but also useful guidance for reducing the vibrations of the hydraulic rock‐breaker in practical engineering applications.

Dynamic analysis of a planar multibody system with multiple revolute clearance joints

This paper focuses on the dynamic responses of a planar mechanism with multiple clearance joints. The effect of the impact between the journal and the bearing in the clearance joint is described using an improved impact force model, and a typical four-bar linkage mechanism with multiple clearance joints is presented as an example. Two conditions are considered in this research, one is the single clearance joint with different position, and the other is multiple clearance joints. From a large number of numerical results, some important conclusions are obtained as follows: (1) with the influence of the clearance joint, the dynamic output of system has obvious vibration in comparison to the ideal value. (2) The position of the clearance joint has a clear effect on the response of system; the larger the distance of the clearance joint from the drive motor, the smaller its influence on the output of the system. (3) With the increase in the clearance joint number, the dynamic stability of the multibody system is decreased gradually, and the dynamic characteristic of the system also appears as obvious nonlinear phenomenon. (4) The coupling phenomenon appears when multiple clearance joints in the multibody system are considered, which should be examined seriously during the process of design and numerical analysis.

An approximate internal model-based neural control for serial robots with multiple clearance joints

A dynamic model of serial robots with multiple clearance joints is developed. The contact phenomenon in the clearance joint is modeled by a continuous dissipative Hertz contact theory, and the friction force is calculated based on the modified Coulomb’s friction law. A neural network method is employed to predict the dynamic response, which avoids the problem in solving the differential algebraic equations. An approximate internal model-based neural control method is proposed to control the undesired effects arising from the joint clearances. The validity of the proposed method is verified by simulation results.

Dynamics analysis of planar rigid-flexible coupling deployable solar array system with multiple revolute clearance joints

Abstract This paper numerically analyzes action of journal at clearance joint and interaction of journal between multiple clearance joints to reveal the dynamic behavior of planar rigid-flexible coupling solar array system considering joint clearance in depth. A typical solar array model used is composed of a rigid main-body described by Nodal Coordinate Formulation (NCF) and two flexible panels described by Absolute Nodal Coordinate Formulation (ANCF). The system consists of two torque springs, one closed cable loop (CCL) configuration, two latch mechanisms and two clearance joints. The normal contact force effect and tangential friction effect at clearance joint are considered by using nonlinear contact force model and amendatory Coulomb friction model, respectively. Action and interaction of clearance joints are studied to indicate motion property of journal in initial phase, deployment phase and post-lock phase, which provide foundations for effect analysis of overall dynamic behavior. Then comparison results reveal the effects of joint clearance, panel flexibility and their coupling on dynamics of solar array system at these three phases. Coupled with clearance at collision phase, elastic vibration property of flexible panels dominates to cause system shock; while coupled with clearance at contact phase, suspension damping property of flexible panels dominates to steady the system. Finally, rational distribution of clearance size may provide a way to balance wear degree between joints. Decrease joint clearance with more intense collision could reduce the wear depth and balances wear degree between clearance joints.