The existing leaf spring fatigue tester which works on the principle of slider-crank mechanism adjusts amplitude by changing the rod length

and it has to stop working for adjustment under current structure.The planar seven-bar mechanism with 2-DOF is studied that attempts to dynamically adjust amplitude by changing the initial phase difference.The workability of the dynamic adjustment of the amplitude is testified through establishing the analytic model of the kinematics

simulating the model with resort to Matlab/Simulink software and Newton-Raphson method.When the initial phase difference is changed

the leaf spring test amplitude is accordingly adjusted.Besides

the hybrid drive fatigue tester could freely control the phase with a lot of flexibility which meanwhile maintains the efficiency and reliability of the mechanic one.