Dynamic Modelling And Simulation Of The Planar Four-bar Mechanism With Joint Clearances

The joints which connect two mechanic components of mechanisms can make sure the machines move relatively. Therefore, the presence of clearance in the joints of mechanisms must be considered. The clearance can cause contact and separation between the joint elements. So that, there will cause windages between the ideal movements and practical movements, increase the force between two machine elements. Then internal dynamic contacts can cause unusual vibration and noise, accelerate fatigue and wear and seriously reduce the machine efficiency. So, the influence of machine with clearance can not be neglected to some machine systems. So this work mainly studies the analysis of dynamic model and simulation of a deployable truss structure with clearances.Firstly, recent researches were reviewed and discussed, several typical dynamics model of pairs with clearances were compared and discussed in respect of impact, damping, friction, etc in detail. Expound the"two-state"and"three-state"clearance model particularly. Considering the influence of machine with clearance,chose the continous contact model to analyse. On the basis of analysis for planar four-bar linkages with clearances, the dynamic differential equations were established. The numerical analysis methods were used to solve the problems, so that the impact-separate rule for the elements of joints were established, meanwhile, compared the dynamic characteristics of mechanisms between clearance considered and no-clearance considered. To be continue, two typical joints with clearance were established, the rotate joint and the remove joint, analysed their dynamics differential equations, compared the dynamic charateristics with different clearances, different damp, some important conclusions were drown. Finally analyse the planar linkages with four clearances using the continuous contact model, established the dynamic differential equations using Larange equations. By solving these problems, which not only show the bad effects clearances have on the stability of mechanism, but the methods to reduce the effects as well.