Abstract

'''A slip film control technique based on an expansion state observer is proposed to address issues such as unclear internal characteristics of cotton-picking hydraulic equipment, modeling difficulties owing to external random disturbances, poor output speed stability, and limited controllability. First, a third-order mathematical model of the valve-controlled motor is established. Then the unmodeled model's dynamic errors and load disturbances are uniformly integrated in-to the 'total disturbances' for real-time estimation and compensated to the sliding-mode controller combined with the expanded state observer by the second-order expanded state observer, and finally, a complete valve-controlled motor system is constructed in the 'MATLAB/Simulink-AMESim' simula. The simulation test results show that the control algorithm is faster, more stable, and more resistant to interference than the PID controller and the backstepping sliding mode controller, with control accuracy improved by 94.5% and 85.6%, respectively, and hydraulic motor output with a constant rotational speed is achieved. '''Key words:''' Expansion state observer; cotton picking head; hydraulic servo system; valve-controlled motor system; constant speed control.