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.

Fault Feature Analysis of Rotor System With Looseness Fault

Focusing on pedestal looseness fault often occurring in practical engineering, a new looseness model is presented by considering respective advantages and disadvantages of all kinds of pedestal looseness model. By using finite element method, the looseness fault is simulated and the fault features are obtained. The simulation results show that when the amplitude of equivalent looseness mass is less than the looseness clearance, the system motion is from period-one through period-two to period-four, amplitudes of low frequency components gradually increase and the axis orbit changes from ellipse to twist with the decrease of looseness stiffness. When the amplitude of equivalent looseness mass is greater than the looseness clearance, high multiple frequency components and continuous spectra appear and axis orbit is similar to a trapezoid due to axis motion restrained by bilateral constraint. These fault features that obtained in different conditions are helpful to diagnose pedestal looseness fault in rotor system.

Tensionability Conditions of a Multi-Body System Driven by Cables

Cable-driven mechanisms have been reported in the literature for the manipulation of a single rigid body. A cable-driven mechanism configured as a Completely Restrained Positioning Mechanism (CRPM) [6], requires a minimum of n+1 cables to maintain the tensionability of the manipulator (i.e. all cables can be made taut), where n is the dimension of the motion space (typically 3 in the planar and 6 in spatial manipulators). In this paper, the idea of cable-driven manipulators is extended to the manipulation of a multi-body system by cables. The first and most fundamental issue to be addressed is the required number of cables and the cable distribution over the links. This problem is thoroughly investigated in this paper. The major issue that differentiates between single rigid body and multi-body cable-driven systems is that in the multi-body systems, each link is subjected to not only the unilateral force of the cables, but also to the bilateral constraint forces and moments of the joints. This requires a new approach for the analysis of the tensionability. The proposed approach in this paper is based on the fundamental equilibrium equations. This will be shown to result that every subsystems of the cable-driven multi-body should satisfy the tensionability condition which also provides all the necessary conditions on the number of the cables attached to that sub-system. These necessary conditions will be then complied to provide the total sufficient number of the cables and their required distribution on the links.