Synthesis Of D-track Link Mechanism Based On Variable Rod Length

With the rapid development of electronics,information,control,drive and other new technologies,modern machines are increasingly required to achieve flexible output,one machine with multiple functions,and meet various functional requirements.Planar linkage mechanism is widely used in various mechanical,instrument and mechatronics products because of its various motion forms,small wear,convenient manufacturing and high precision.But it also has the following disadvantages: generally,it can only approximate the given motion law or trajectory,and the design is complex;When the given motion requirements are more or more complex,the number of components and motion pairs is often more,which makes the structure complex and the cumulative error increases.In this dissertation,an adjustable bar is introduced into the traditional four-bar mechanism to overcome some shortcomings of the single degree of freedom linkage mechanism.Taking the adjustable four-bar mechanism as the research object,this paper focuses on the synthesis of D-type trajectory,the realization of variable rod length and the design of engineering examples1.The straight line segment of D-type trajectory is synthesized.The inflection point circle is introduced into the rectangular coordinate system,the constraint equation of the inflection point circle is derived,and the mathematical model of the planar linkage mechanism is established.The position of the mechanism is determined by the geometric method.Then the particle swarm optimization algorithm is used to optimize and synthesize the initial solution of the adjustable four-bar mechanism with different rods.Finally,the length of the rod corresponding to the middle position of the straight line segment is obtained by using the vector closed equation.2.The special point method and the concrete point method are proposed for the curve segment of D-type trajectory.The special point method needs less computation and is mostly used in the case of low requirement of curve trajectory;The specific point method has a large amount of calculation,and is often used in the case of high requirements for specific points of curve segments.Then,the kinematic analysis of the adjustable four-bar mechanism with different adjusting rods is carried out,and the analysis results are used as the basis for the selection of different adjusting rods.3.Using servo motor to drive the ball screw to drive the slider as the way to adjust the length of the rod,and analyzing the dynamics of the adjustable four-bar mechanism,which provides a theoretical basis for the selection of motor and ball screw,and illustrates the design process through an example.4.Through the analysis of the technological requirements of the cigarette pushing mechanism,it is proposed to use the adjustable four-bar mechanism to realize the motion law and carry out the dimensional synthesis.Secondly,the model is built by Solid Works,and then the kinematics and dynamics are analyzed by Adams.The theoretical results show that the method is feasible.