Research On Reliability Of Crank-slider Mechanism Based On Variable Length

Slider-crank mechanism has a large carrying capacity,beneficial to the lubrication,wear light,long life,easy processing,low cost and many other advantages,and it is widely used in the machinery industry.Due to the original manufacturing and assembly errors and the existence of rotating pair gap,these unavoidable error factors will seriously affect the slider's motion reliability.In this paper,the eccentric slider-crank mechanism is taken as an example to study the influence of rod length on the reliability of the displacement of the slider.The displacement reliability of the slider is improved by changing the size of the component.Therefore,this study on the reliability of mechanism movement has certain theoretical and practical significance.Firstly,from the perspective of mechanism kinematics,this paper establishes a calculation model of the displacement reliability of the slider of a biased slider-crank mechanism which includes the length error of the lever,and studies the influence of the change of the lever length on the reliability of the displacement of the slider.The corresponding MATLAB simulation program is compiled and the conclusion is drawn that the influence of the change of the length of crank,connecting rod and offset on the reliability of the displacement of the slider is different when considering the length error of the rod.Secondly,the calculation model of slider reliability of biased slider-crank mechanism is established considering the long-dimension error of rod and the rotating pair gap.The influence of the variable rod length on the reliability of the displacement of the slider is analyzed and compared under the two contact models(continuous contact model and discontinuous contact model).Based on the MATLAB software simulation,the displacement reliability of the slider is obtained.As the length of the crank decreases,the length of the connecting rod increases and the offset length decreases.When the rotating pair gap is continuous contact model,the change of rod length has more significant improvement on the reliability than the discontinuous contact model.Then,exhaustive method is proposed to optimize the length of the slider with improved stability of the slider with constant stroke constraints.The optimal feasible solution and the optimal solution are obtained under the combination of two kinds of bar length.Based on the obtained optimal solution,the reliability of the displacement of the slider after the combination of two kinds of bar length is analyzed is compared with the reliability of the displacement of the slider before optimization.The results show that the reliability of the displacement of the slider is obviously improved.And it is found that the reliability of the displacement of the slider when the combination of the three lever lengths changes is more significant than the combination of the two lever lengths.Finally,Based on the influence of the single rod length on the reliability of the displacement of the slider,genetic algorithm is proposed to optimize the length of the slider with improved stability of the slider with constant stroke constraints.By checking the feasibility of the solution to determine the solution to the reservation or abandoned to deal with the constraints,after using binary coding and decimal coding of these two coding methods to optimize the length of the genetic algorithm.The result of the optimization is close to that of the exhaustive method in the fifth chapter,which proves the correctness of the genetic algorithm.