Abstract
A modified sliding mode active disturbance rejection control (MSMADRC) position system is designed for small-sized tractors to solve the longer shift time and reduced shifting quality because of the inaccurately motor control used for the automatic mechanical transmission (AMT) gear shift actuator. Firstly, the control model of the motor with total disturbance is established. Then an extended observer is presented to monitor the unmodeled dynamics and various disturbances of the system in real time, at the same time the extended state and the system feedback variables are constructed as the system variables of the sliding mode control (SMC) algorithm. Secondly, a sliding mode surface instead of the nonlinear control law in the active disturbance rejection control (ADRC) algorithm is designed, which realizes the fast and accurate tracking of the position. What's more, the stability of the control system is proved by Lyapunov theory. Lastly, the simulation results demonstrate that the position control precision by MSMADRC is higher 37% than by SMC and higher 75% than by ADRC. Furthermore, the response speed of MSMADRC is the fastest, it only takes about 0.7s.