Development Of A Novel Compact Continuously Variable Transmission For Robotics

The reducer is one of the core parts of the robotics,which has the effect of decelerating speed and increasing torque.Harmonic reducers and RV reducers with fixed transmission ratios are currently commonly used reducers for robotics.They have complex manufacturing process and expensive price,which seriously limits the rapid development of robotics industry.According to the research,the robot joint with fixed transmission ratio reducer will cause the motor to work far less than its peak efficiency,and it is difficult to play the optimal performance of the motor;while the reducer with variable transmission ratio can make the motor work near the peak efficiency,but the existing transmissions have not been widely used in robotics transmission systems because of the influence of transmission ratio range,structure and weight.Therefore,in order to meet the needs of robotics for deceleration technology and efficient transmission,this paper studies the new transmission principle based on V-belt transmission and planetary gear train transmission,and designs the compact continuously variable transmission(CVT)based on nested structure,which provides useful exploration and practical experience for the research of new reducer for robotics.First of all,based on V-belt transmission and planetary gear train transmission,this paper studies the new transmission principle,designs the compact structure of CVT based on nested method,analyzes the geometric parameters affecting the transmission and speed change of the device,and determines the range of its transmission ratio.Secondly,the dynamic models based on the novel transmission principle are established to analyze the dynamic problems such as the dynamic reaction force of the base,the restrained reaction force of the planetary pulley and the motion equation of the planetary carrier.Through dynamics simulation,the correctness of the new transmission principle is verified,the effect of different loads on the transmission efficiency at a constant transmission ratio is discussed,the influence of different eccentricity on input torque is analyzed,the influence of different transmission ratios on transmission efficiency at constant load is discussed,and the dynamic problems such as the base dynamic reaction force,the planetary pulley constrained reaction force and the planet carrier motion equation is verified.Then,after analyzing and comparing the different eccentric layout scheme and output mechanism scheme of the CVT,the eccentric shaft layout scheme and the pin hole output mechanism scheme are determined respectively,and a prototype of manually changing transmission ratio is developed.Experimental tests showed that the prototype has the function of CVT.Finally,in order to better adapt to the work of robotics and lay the foundation for the research of adaptive variable speed in the later period,this paper designs a prototype of ratio adjustment based on hydraulic drive,the static balance optimization of eccentric shaft and the finite element static structure and modal simulation analysis of key parts are developed,the hydraulic drive system is developed and tested,the optimization design is carried out according to the problems in the assembly process of the prototype and the experimental scheme of load test is designed.