In this article,a four-limb linkage horizontal fitness bike is designed;efforts are made to fully develop its poten-tial and set up the motion equation with the help of the analytical method.On the one hand,the trajectories of the foot J point and the handrail S point are identified,and each bar's optimal length is determined accordingly.On the other hand,both the speeds and the accelerations of the J point and the S point are obtained,and then they are verified by means of motion simulation,so as to ensure that the fitness bike is moving smoothly.In addition,the fitness bike is subject to the static simulation in a motion cy-cle,in order to meet the requirements of strength.Finally,both the frame and the handrail link are subject to the modal simula-tion,so as to avoid resonance.The results show that the analytical and simulation values of the trajectory,the velocity and the ac-celeration of the J point and the S point are consistent,which verifies that the motion equation is accurate.When l1=180 mm,l2=300 mm and l0=600 mm,the trajectories of the J point and the S point are optimal,and their velocity and acceleration fluctu-ate within a minor range.In a motion cycle,the pedal stress is the maximum when θ1=-35° or θ1=145°.In order to ensure that the maximum stress at this time is less than the yield strength,the axis A's diameter is at least 15 mm.The first four-order natu-ral frequencies of both the frame and the handrail link are larger than the fitness bike's working frequency.Therefore,no reso-nance occurs.
维普
万方数据