Method for the synchronous speed control of sugarcane root cutter disc driven by dual hydraulic motors

Sugarcane harvesting machinery has restricted the mechanization of the whole sugarcane industry. Some challenges still remain on the cutter driving of sugarcane root, due to the terrain landscape, sugarcane varieties, soil types and climates. Among them, sugarcane root cutter is one of the most key components in the combine harvester. The working performance of root cutter can depend mainly on the sugarcane head breaking rate, material blockage and energy consumption. The complex structure of the sugarcane root cutter is often driven by a single hydraulic motor in the sugarcane harvester. The low quality of the sugarcane root cutter can attribute to the heavy load of own size and the high center of gravity. The large fluctuation can be then caused by the rotational speed of the cutter disc under the time-varying loads in the throttling speed control of hydraulic motors. In this study, the dual-motor electro-hydraulic proportional load-sensitive technology was proposed into the transmission system of the root cutter. The dual cane cutting cutters were directly driven by two hydraulic motors rather than the gear box. The mechanical structure was simplified for the energy transfer path to further reduce the energy loss. The synchronization accuracy of the dual cutter disc under load disturbance was improved using the sliding mode variable control. The mathematical model was established for the speed control system of electro-hydraulic proportional valve motor. The transfer function of the system was deduced to determine the stability threshold to be only 16.5°; The simulation platform was constructed using AMESim-MATLAB. The synchronization control was explored to optimize a master-slave control strategy and the master motor of a PID (Proportion Integral Derivative) control system. Integral Derivative (PID) control was also taken as the master motor. The stability and speed control accuracy of the system were compared, when the slave motor was controlled by PID, adaptive fuzzy PID and sliding mode variable control. The simulation results show that the tracking error of the master and the slave motor speeds in the steady state stage was 5r/min in the sliding mode variable control, while the tracking errors of the steady state speeds were 20 and 8 r/min using the PID and the adaptive fuzzy PID control, respectively. The speed fluctuation of the master and slave motors was controlled in a small range using the sliding mode variable control, which was reduced the vibration of the cutter plate; The test bench of the sugarcane root cutter was built to carry out the synchronous control tracking of master and slave motors. The speeds of the master and slave motors were taken as the indexes, and the measured load spectrum was as the load input. The dynamic adjustment time of the PID, adaptive fuzzy PID and sliding mode variable control systems was 6.3, 4.6 and 3.7 s, respectively. The speed fluctuation values of the slave motor in the steady state stage were 38, 13 and 9 r/min, respectively, while the speed differences between the master and slave motors were 47, 23 and 13 r/min, respectively. The synchronization control with sliding mode variable structure was lower than the PID and self-sliding mode variable structure, in terms of the adjustment time, speed fluctuation, and speed difference of the master and slave tracking. The difference was also lower than those of PID and adaptive fuzzy PID synchronous control. The error of synchronous control was the smallest. The finding can provide the theoretical references to optimize the transmission and control system of sugarcane harvester root cutter.