Characteristic Research Of Planar Five-bar Mechanism Having Joints With Clearances

With the development of machines towards high speed and high precision, the joints with clearances affect the performance of the mechanical movement has drawn increasing attention. When the clearance size increase, the collision and vibration in the joint occurs, this leads to the wear and tear of the joint, eventually resulting in the deterioration of the precision of the machine and the reduction of service life. More importantly, the clearance undermines the ideal of clearances agency model, and thus also on the actual movement and had a deviation between the ideal movement.The planar five-bar mechanism is used in the production line robot assembly, medical arm, vacuum circuit breaker and the car suspension system. From its applications, this mechanism requires high movement precision, stability, and high reliability. So this work mainly studies the dynamic model of planar five-bar mechanism having joints with clearances.Firstly, the research background and actuality in the mechanism with clearance joints are summarized, and existing dynamic models and solutions are analyzed.Secondly, using permanent contact model, the kinematic and dynamic analysis to planar five-bar mechanism having revolute joints with clearances is proposed. Then a mathematical model for this mechanism is presented, based on Lagrange equation. And a simulating dynamic model is built by SIMULINK in MATLAB software.Thirdly, through the simulation model and test bench of the planar five-bar mechanism to comparison, an analysis the affection of clearances on the five-bar movement accuracy, movement performance. Then, kinematic effects on clearance are detail analyzed, with the crank speed change.Finally, a genetic algorithm (GA) is used to implement the optimization of link parameters based on an appropriate objective function of path errors due to joint clearances. The results of a practical example show that the mathematical model is right and the proposed method is very efficient for the purpose of adjusting the link dimensions to optimize planar mechanisms with clearances.