Reducing undesirable effects of clearances on dynamic and wear of planar multi-link mechanism

Due to influence of manufacturing accuracy, friction and wear in the working process, the clearance error of the kinematic pair is inevitable. The clearances will lead to impact of response and vibration of mechanism, which not only accelerate wear of clearance joint, but also affect normal operation and precise control of mechanism. Nine-bar mechanism with two revolute pair clearances has been taken as a research object. Aiming at problems of reduced stability, increased noise, aggravated wear, and so on, multi-objective optimization design of multi-link mechanism containing multiple clearances is studied with the help of genetic algorithm. Minimum contact force at clearance joint has been taken as optimization objective function. Influence of clearance on mechanism is reduced by optimizing mass, position of centroid and moment of inertia for key components. The influences of LuGre model and modified Coulomb friction model on dynamical responses of mechanism with clearances are analyzed in detail. Influences of optimization on dynamics responses and nonlinear characteristics of mechanism considering clearances are studied, and nonlinear characteristics are researched by phase diagrams, Poincare maps and bifurcation diagrams. Based on optimized data, ADAMS model is established to verify correctness for dynamics model. At the same time, influences of optimization on dynamics behavior of mechanism considering clearance wear are also analyzed, including wear characteristics, dynamic responses and nonlinear characteristics. The results show that optimization improves dynamics performance of mechanism to a great extent, reduces wear phenomenon and increases stability for mechanism.