In this study, the output of bicycle is a kind of dynamic link output, bicycle movement has certain inertia, its change will not jump at any time, but the speed command is jumping. Therefore, when the initial error of the system is large, in order to achieve the tracking effect, the system will produce a large overshoot, resulting in a large initial impact. In view of this, in order to reduce the initial error and overshoot of the system, a suitable Active Disturbance Rejection Control (ADRC) structure is designed in this paper. The nonlinear tracking differentiator is used to arrange the transition process, and the nonlinear extended observer is used to carry out the nonlinear PID controller to realize the automatic transmission of bicycles. Experiments prove that using proximity switch to detect the number of rotation cycles of bicycle pedal in fixed time as system count, feedback with speed sensor, and using single chip controller as PID control theory to drive DC motor to adjust the gear of bicycle transmission, and to improve the accuracy of gear transmission, can make riding bicycle more labor-saving. With the improvement of safety, in order to achieve the purpose of bicycle automatic transmission design.
