Revolute Clearance Research Articles

Dynamic modeling and performance analysis of toggle-linkage presses considering mixed clearances and flexibility

The clearance joints cause the mechanical multi-body system to exhibit complex dynamic behavior, resulting in a decrease in performance and reliability. Another important factor influencing the dynamic response of a planar mechanical system is the flexibility of links. A dynamic model of the flexible toggle-linkage mechanism with mixed lubricated clearance joints is established in this study. The dynamics model of the multi-body system is combined with the lubrication models of prismatic and revolute clearances in this approach. Experiments on toggle-linkage mechanical press under different loads and speed were made to measure the dynamic response. Meanwhile, the effects of blanking force and different clearance joints on the dynamic responses of the toggle-linkage mechanism were studied. The results of the dynamic simulations showed that the flexible–rigid model with mixed clearances and lubrication agreed with the experiment data better. The simulation results demonstrated that the linkage’s flexibility and lubrication can cushion the impact between the elements of mixed clearances. Furthermore, the increase of the number and type of the joint clearance reduces the stability and motion accuracy of the toggle-linkage mechanism.

Dynamic accuracy reliability modeling and analysis of planar multi-link mechanism with revolute clearances

Due to the influence of various factors in the planar linkage mechanism, clearances will occur at the kinematic pair unavoidably. The existence of clearances will reduce the kinematic accuracy of mechanisms and have a great influence on reliability of mechanisms. At present, most of researches focus on static reliability of mechanisms or dynamic accuracy reliability of simple mechanisms with a single clearance, while the research on dynamic accuracy reliability of complex multi-link mechanism with several clearances is less. In this paper, a novel modeling and calculation method for dynamic accuracy reliability of complex multi-link mechanism with revolute clearances is proposed, and the impact of different factors on dynamic accuracy reliability of mechanism is researched. Taking 2-DOF 7-bar linkage mechanism as an example, a dynamic model with revolute clearances is derived, and the dynamic accuracy reliability model of mechanism is developed based on stress-strength interference theory. The impact of driving speed, clearance values and friction coefficient at the clearance on dynamic accuracy reliability of mechanism in different variation ranges is studied. The research can not only provide evidence for reliability design of the follow-up mechanism, but also has a reference significance for research on reliability of other mechanisms.

Dynamic response and chaos in planar multi-link mechanism considering revolute clearances

During actual motion, there are inevitably clearances between the motion pairs of the mechanism, and the clearances will have a large impact on stability of the mechanism. Previous studies mainly focused on the dynamic response of simple mechanisms with single clearance and less on chaos. Even if chaos is studied, it mainly focused on the chaos of mechanisms and less on the chaos of clearance joints; however, it is well known that the analysis of chaotic characteristics of clearance is the key to fault diagnosis of kinematic pairs. In order to give a computational methodology for dynamic analysis of planar multi-link mechanism considering multi-clearances and master the dynamic response of planar multi-link mechanism, the dynamic response and chaos of a planar six-bar mechanism are researched. A multiple clearances dynamic model of planar six-bar mechanism is built by Lagrange multiplier method, and the dynamic model is solved by Runge–Kutta method. The influence of different clearance positions, clearance numbers and clearance sizes on dynamic response of mechanism is analyzed. The nonlinear characteristic analysis of six-bar mechanism is conducted, and chaotic phenomena of the clearance joint are explained by Poincare maps and phase diagrams. The bifurcation diagram at clearance of the revolute joint changes with different clearance values, friction coefficients and driving speeds is given. Those above results provide an important theoretical basis for the study of influence of multi-clearance on dynamic responses and chaotic phenomena of planar multi-link mechanism.

Dynamic Modeling, Response, and Chaos Analysis of 2-DOF Hybrid Mechanism with Revolute Clearances

Due to the errors arising from machining or assembly, the deformation during movement, and the wear of movement pairs, the clearance will be generated at the kinematic pair of the mechanism, and the service life or working accuracy of the mechanism is reduced. At present, most of the researches are in a simple mechanism with a single clearance, and there are few papers on the complex mechanism, such as the high-speed mechanism which contains multiple clearances. In order to give a computational methodology for the dynamic modeling and analysis of the planar multilink mechanism with multiple degrees of freedom and multiple clearances and master the dynamic characteristics of the planar multilink mechanism, the nonlinear dynamic models of the multiclearance hybrid seven-bar mechanism under different clearance numbers, different clearance values, different clearance positions, and different driving velocities are established and analyzed. The dynamic output response comparison diagram of the mechanism and the collision force diagrams and center trajectory diagrams of the mechanism at the clearance are given. Then, nonlinear dynamics of the mechanism is studied by different clearance values and driving speeds. The corresponding trajectory phase diagrams, Poincare maps, and bifurcation diagrams are given. The above research results provide an effective theoretical basis for the study about the nonlinear dynamic characteristics of the planar link mechanism with clearance and how to compensate or control the clearances.

Nonlinear Dynamics and Analysis of a Planar Multilink Complex Mechanism with Clearance

In order to understand the nonlinear dynamic behavior of a planar mechanism with clearance, the nonlinear dynamic model of the 2‐DOF nine‐bar mechanism with a revolute clearance is proposed; the dynamic response, phase diagrams, Poincaré portraits, and largest Lyapunov exponents (LLEs) of mechanism are investigated. The nonlinear dynamic model of 2‐DOF nine‐bar mechanism containing a revolute clearance is established by using the Lagrange equation. Dynamic response of the slider’s kinematics characteristic, contact force, driving torque, shaft center trajectory, and the penetration depth for 2‐DOF nine‐bar mechanism are all analyzed. Chaos phenomenon existed in the mechanism has been identified by using the phase diagrams, the Poincaré portraits, and LLEs. The effects of the different clearance sizes, different friction coefficients, and different driving speeds on dynamic behavior are studied. Bifurcation diagrams with changing clearance value, friction coefficient, and driving speed are drawn. The research could provide important technical support and theoretical basis for the further study of the nonlinear dynamics of planar mechanism.

The Impact Analysis of Revolute Pair Clearance to the End Pose Accuracy of Welding Robot

Various uncertain factors affect the movement of the welding robot, thus welding gun tend to deviate from the theory of welding position which reduces the welding accuracy, of which the revolute pair clearance have an greater effect on the movement of the welding robot. In order to study the influence of revolute pair clearance to the end pose accuracy of welding robot, the mathematical model of revolute pair clearance was established, and the software SolidWorks was used for establishing the welding robot model, making simulations of the mechanical arm with joint clearance and no joint clearance. At last, the movement characteristic of the hinge shaft is attained. The simulation results showed that the shaft velocity and displacement of mechanical arm with joint clearance has a certain degree of fluctuation, which affecting the end pose accuracy of welding robot , and reducing the movement stability and the welding accuracy of welding robot.

On the Dynamic Gear Tooth Loading of Planetary Gearing as Affected by Bearing Clearances in High-Speed Machinery

The paper studies the effect of bearing clearances in the dynamic analysis of planetary gear mechanisms in high-speed machinery. For this purpose, an analytical model is developed based on the interdependence between kinematics and kinetic relationships that must be satisfied when contact is maintained between the journal and its bearing. The contact mode is formulated such that the bearing eccentricity vector must align itself with bearing normal force at the point of contact. The analysis mainly relies on determining the direction of the bearing eccentricity vector defined as the clearance angles βi at the bearing revolutes for each contact mode of the gear teeth. The governing equations of the clearance angles are developed using the geometrical constraints of the contact point location and the velocity ratio. The clearance angles and their derivatives are used to systematically evaluate kinematic and dynamic quantities. A rigid planetary spur gears with two revolute clearances is analyzed to illustrate the procedure.

An Approach for Dynamic Analysis of Mechanical Systems with Multiple Clearances Using Lagrangian Mechanics

The paper develops a general procedure for the dynamic analysis of planar mechanisms with multiple clearance. The analysis mainly relies on determining the clearance angles βi at mechanism revolutes for each phase of the analysis. The governing equations of each clearance angle are developed using Lagrangian mechanics. The solution is obtained in the form of sufficient number of harmonic terms and used to evaluate systematically kinematic and dynamic quantities of the mechanism. A slider-crank mechanism with three revolute clearances is analysed to illustrate the procedure.

On the Dynamic Gear Tooth Loading as Affected by Bearing Clearances in High Speed Machinery

The paper studies the effect of bearing clearances in the dynamic analysis of gear mechanisms in high speed machinery. For this purpose, an analytical model is developed based on the interdependence between kinematics and kinetic relationships that must be satisfied when contact is maintained between the journal and its bearing. The contact modes are formulated such that the bearing eccentricity vector must align itself with bearing normal force at the point of contact. The analysis mainly relies on determining the direction of the bearing eccentricity vector defined as the clearance angles βi at the bearing revolutes for each contact mode of the gear teeth. The governing equations of the clearance angles are developed using the geometrical constraints of the contact point location and the velocity ratio. The clearance angles and their derivatives are subsequently used to systematically evaluate kinematic and dynamic quantities of each gear as well as the dynamic tooth load. A pair of rigid tooth spur gears with two revolute clearances is analyzed to illustrate the procedure. The model presented in the paper provides a design method for investigating the effect of bearing tolerances and wear on the evaluation of dynamic tooth load in high speed gearing systems.