Research On Dynamics Of Main Transmission System Of Mechanical Transmission Test Machine

Generally,it is necessary for the main drive system of test machines to realize isokinetic reciprocating motion rule,such as tension compression fatigue testing machine and shock absorber testing machine and other machines,so as to ensure the comparability of the test results.Nevertheless,only approximate isokinetic motion rule can be achieved for the current testing machine,instead of standard isokinetic motion rule.It is reasonable to manufacture a machine that can realize standard isokinetic reciprocating motion rule.Several key problems to develop the main transmission system of the machine are studied successively in this paper,including its motion scheme and structure,dynamical analysis on rigid body and flexible body of the system.The main research contents are as follows:(1)According to the working requirements of isokinetic reciprocating motion rule,a functional analysis method is applied to select the mechanism type.A combined mechanism with a series of non-circular gears and a sine mechanism is put forward to realize the required movement.The pitch curve of the non-circular gear is designed by the inverse evaluation method,and the multi solvable design schemes of several non-circular gear pitch curves are given.(2)The structure of the main transmission system of the mechanical driving tester is designed.The assembly diagram of the main drive system and the structure and size of the typical parts are drawn.(3)A dynamical equivalent model is established,which is composed of the driving motor and all rigid body of the system.The motion differential equation of the system is constructed by using the law of kinetic energy and solved by the Euler method.The curve of the angular fluctuating velocity of the output shaft of the motor is obtained and the output fluctuating speed of the sine mechanism follower is also calculated.The calculating results show that the angular velocity fluctuation rate of the output shaft of the motor is 9.8%and the relevant speed fluctuation rate of the follower of the sine mechanism is up to 0.08%.It can be seen that the isokinetic motion rule of the sine mechanism follower is affected by the fluctuation of the motor.(4)A torsional vibration model of the main transmission system is established.The elastic deformation of non-circular gear teeth is considered and support bearing,transmission shaft support and torsional stiffness are ignored.In this paper,an equivalent cylindrical gear pair for the non-circular gear pair is suggested to establish the motion differential equation of the main transmission system.The comprehensive meshing stiffness of a non-circular gear pair in a moving cycle is calculated,the differential equations of the system are solved by using the Runge-Kutta method,and the output velocity law of the sine mechanism follower under the motion period is obtained.The results show that:the speed fluctuation rate of the sine mechanism follower is 1.13%,and so,it is very necessary to study the dynamical problem of the main transmission system considering the elastic deformation of the non-circular gear.Both the motor speed fluctuation and the non-circular gear vibration will cause the speed fluctuation of the follower,and under the joint action of the two,the total speed fluctuation rate of the follower is 1.15%.