Experimental Electro-mechanical Speed Ratio Variator of Rubber Belt Continuously Variable Transmission for Motorcycle Applications

In Indonesia, a motorcycle equipped with a rubber belt continuously variable transmission (CVT) is called Matic motorcycle. This kind of motorcycle mostly utilizes centrifugal forces to activate its speed ratio variator and clutch mechanisms. Matic motorcycles are very popular due to their easy drivability and smooth driving comfort. The centrifugal forces mainly depend on the engine speed. This dependency causes some disadvantages that need to be considered for future improvements. This paper introduces an electromechanical rubber belt CVT for motorcycle applications and carries out experimental works for its speed ratio variator to obtain correlation data between the position sensor voltage and speed ratio. The common type of CVT consists of driving pulley, driven pully and a stiff rubber belt that connects the two pulleys. The speed ratio is changed by varying both driving and driven pulley diameters simultaneously. The speed ratio variator of this electro-mechanical CVT employs a DC motor as its main actuator, thus removing the dependence of the speed ratio on engine speed. A test rig was set up and a data acquisition system consisting of an Arduino Uno microcontroller as well as position and speed sensors is developed to carry out the experimental works on this electromechanical CVT. Experimental results show that the CVT speed ratio has a range of between 1.8 (low speed) and 0.68 (high speed). In addition, the relationship between the speed ratio and the output voltage of the driving pulley position sensor is successfully approximated using the third-order polynomial equation with an average percentage error of about 2.87%. This equation is mainly used to determine the current value of its respective speed ratio.