Effects of clearances on dynamic response and nonlinear characteristics of the planar multibody mechanical system

Clearance inevitably exists in kinematic pair of the mechanism, which leads to the reduction of the accuracy and performance of the mechanism. At present, a great deal of researches is concentrated on simple mechanism with single clearance or only on its dynamic response, but few gave priority to mechanism with multiple joint clearances, and both on its dynamic response and nonlinear characteristics. In this article, a method for nonlinear dynamic analysis of planar multibody mechanical systems is proposed, and the influence of dynamic response and nonlinear characteristics of joint clearance on six-bar toggle planar multibody mechanical system is studied. Firstly, the normal contact force and friction force of the mechanism are modeled by the Lankarani–Nikravesh model and the modified Coulomb model. The dynamic equation of the mechanism is derived based on the Lagrange multiplier. Then, influences of different clearance positions, the number of clearances, and clearance values on the dynamic response of the mechanism are explored. Finally, influences of different clearance values, friction coefficients, and driving velocity on the nonlinear characteristics of the mechanism are investigated. Chaos phenomenon of the mechanism can be judged by the phase diagram, Poincare map, and Bifurcation diagram. This study provides a method for studying the nonlinear dynamics of planar multi-link mechanisms with clearances.