Study on Dynamic Characteristics and Parameter Influence of a Kind of Bilateral Restraint Impact Vibration System

In this paper, the hinge in the articulated structure is studied, the gap hinge is described as a nonlinear bilateral constraint, and the equivalent modeling and analysis of the hinge connection collision vibration are carried out based on the Lankarani–Nikravesh nonlinear contact force model. With the help of the method of nonlinear system dynamics analysis research, the Poincaré mapping of hinge joint collision vibration is constructed, the bifurcation diagram of the system with different parameters is solved, and the variation law of the system motion and the influence of parameters are analyzed by combining the time response diagram, phase diagram, Poincaré cross section diagram, and spectrum diagram of the typical motion of the system. The simulation results show that the system moves in a single degree of freedom and varies with parameters with multiplicative period bifurcation and rubbing edge bifurcation leading to chaos; the system’s periodic motion has shock state mutation and mirror jump transformation.

Dynamics Analysis of Truss Deployment Mechanism With Imperfect Joint Considering Input Fluctuation

Modern spacecraft usually has large deployment structure, which consisting of plenty of joints could produce undesirable dynamic responses when considering clearances in joints and driving input fluctuation. However, in the dynamic performance analysis of space deployment mechanism, the clearances and input fluctuation are always ignored. In this study, the dynamic responses of a flexible planar scissor-like truss deployment mechanism with imperfect joint considering clearance and input fluctuation are investigated using computational methodology. First, the mathematic model of clearance joint is established. The revolute clearance joint is considered as force constraint and the joint components of an imperfect joint with clearance are modeled as contact bodies. The normal contact force model of clearance joint is established using a continuous contact force model considering energy loss. The friction effect is considered using a modified Coulomb friction model. Then, the dynamics performances of the flexible planar scissor-like truss deployment mechanism with imperfect joint considering clearance and input fluctuation are presented and discussed. Different case studies for the scissor-like truss deployment mechanism with clearance are investigated considering driving input fluctuation. The simulation results show that the dynamic characteristics of the mechanism with clearance joint are changed more obviously when considering driving input fluctuation. Therefore, investigation implies that dynamics responses of the truss deployment mechanism are much worse when considering clearance joint and input fluctuation, which indicates that driving input fluctuation leads to more obvious degradation of the dynamic performance of the truss deployment mechanism with imperfect joint.

An Experimental Correction Method for Relative Indentation of Normal Contact

ABSTRACTRelative indentation is the input signal estimating contact force model parameters, so the signal is required to have a higher precision to ensure the accuracy of the estimated contact force model parameters. However, in the impact experiment, the vibration displacements in multiple directions are often coupled in the relative indentation, resulting in a large error of the measured relative indentation. This paper presents an experimental correction method for the relative indentation. Firstly, the relative indentation is decoupled by the established model of the spatial position of the hammerhead relative to the sample to reduce the errors caused by the rotation of the pendulum boom and the vibration of the base. A pendulum impact test device is established to verify the correction method of relative indentation. The results show that the maximum relative error between the contact force estimated by using the corrected relative indentation as the input signal and the measured contact force is less than 3%. The estimated contact force is in good agreement with the measured value, and the correlation coefficient is above 0.92. It shows that the experimental correction of the relative indentation has achieved good results, which verifies the accuracy of the correction method.

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.