Application Of Four Bar Mechanism With Variable Parameters In Position Control

The four bar linkage is widely applied in engineering machinery because of its diversity of link curves,and the movement of known trajectories is achieved according to design requirements.But there is a clear limitation in this.When every parameter of the mechanism is determined,only one fixed track can be accomplished by the fixed point on the connecting.The requirements of the modern machinery to the flexibility of the mechanism are getting higher and higher,and the requirements of the modern institutions can not be met by the single set of production movements of a set of institutions.The four-bar mechanism also needs to be improved and optimized.In order to better adapt to the development of modern manufacturing industry and enhance the application space of four bar linkage,a multi parameter variation study of hinge four bar mechanism is put forward.During the movement of four bar linkage,three parameters are controlled to realize the fixed point multi track motion on the connecting rod and control the position and posture of the connecting rod.Removing meat from shell of abalone is took as an example in the sbject.The dissection tool is controled to move along the abalone shell and the angle of the cutter is controled during the dissection.The above objectives are achieved by the double-rocker mechan--ism.The three parameters of the variable parameter four-bar mechanism are the left rocker angle,the length of the connecting rod and the length of the right rocker.In order to control tool path and angle in dissection process,the length change of connect ingrod and right rocker are controled during left rocker rotation process.The specific research work of the projectare as follows:(1)Overall scheme design of four-bar mechanism with variable parameters in posi tion control.According to the requirements of the project,the overall design process of the whole project is determined,and the control scheme of the whole organization is completed.(2)The establishment of mathematical model of four-bar mechanism with variableparameters in position control.A mathematical model is established by determining the input variables and output results of the mechanism.The functional relation between the corner of the left rocker and the coordinate of the execution point and the swing angle of the connecting rod is mainly established.The functional relationship between the length of the right rocker and the corner of the left rocker,the swing angle of the connecting rod and the length of the connecting rod is established.(3)Discrete processing of dissection trajectory of abalone.The best dissection path of abalone is obtained,the coordinate transformation is carried out,and the dissection trajectory equationof abalone is determined.The dissection trajectory is discreted using Matlab software.(4)Simulink modeling and Simulation of four-bar mechanism with variable para--meters in position control.The Simulink models of the left rocker angle function and the length of right rocker function are established on the basis of the function relation established earlier.The control data of each parameter in the dissection process are obtained by simulation,and the discrete density is adjusted.(5)3D structure design and modeling of four-bar mechanism with variable param--eters in position control.The structural design and simulation analysis of variable parameter four bar linkage are carried out with Solidworks software.The rationality of the structural design is verified.The trajectory error and the position and positioner ror of the connecting rod are calculated.(6)Inputting of control data and simulation analysis.The control data is input into the driver of the stepper motor.The rotation of the crank is controled by a stepper motor to achieve known trajectories.The length change of connecting rod and rocker are controled by other two stepper motors through the structure of screw and nut.The pose of the connecting is controled by the interpolation motion of connecting rod and rocker.The motion path and angular displacement of the tool are analyzed,and the correctness of the data is verified by the simulation in the Solidworks.