Rotational speed control of threshing cylinder of oil sunflower combine harvester based on active disturbance rejection controller-dynamic matrix predictive

Aiming at the real-time, accuracy and adaptability requirements of threshing cylinder control method of oil sunflower combine harvester, the mathematical model of rotational speed control of threshing cylinder for oil sunflower harvesting is given in this paper. The walking speed of oil sunflower combine harvest was selected as the control variable and the rotational speed of threshing cylinder was selected as controlled variable. The rotational speed dynamic model of the threshing cylinder was converted to a affine system which is suitable for ADRC (active disturbance rejection controller), and then the control system based on the ADRC. The internal disturbance, external disturbance and the coupling effect between velocity tension of the system are considered as the total disturbance of the system, the extended state observer is used to observe and compensate the control delay, and the dynamic matrix predictive (DMC) control method is further used to process the control delay. The DMC predictor continuously collects feeding quantity at the current time to predict the feeding quantity at the time according to the predictor. When the predicted value exceeded the setting range, the control system would adjust the walking speed of harvester and the rotational speed of threshing cylinder in time, i. e. to increase the walking speed of the harvester, to increase the feeding quantity, to improve the efficiency or to reduce the walking speed of the harvester, to reduce the feeding quantity and to avoid the blockage of the threshing cylinder, thus the feeding quantity is always kept within the setted optimum range, so that the speed of threshing cylinder can be controlled in advance. The hardware and software system of DSP based on ADRC-DMC nonlinear controller was designed, the simulations, laboratory test and field test were carried out for the designed threshing cylinder controller. Simulation results showed that in the absence of random disturbance, system response curve was smooth, and no overshoot, faster response and system could adjust itself when feeding quantity increased suddenly, the rotational speed of threshing cylinder began to decrease and stabilized at 390.2 r/min after about 1.2 s, and the system response curve was smooth. In the bench test, when the threshing cylinder ran at the optimum speed of 430 r/min, the optimum feeding quantity was 2.45 kg/s, after 15 s, randomly invested about 0.15 kg oil sunflower tray and stem to change the feeding quantity, the test results showed that the rotational speed control method based on ADRC-DMC could adjust the speed in a small range and had a good inhibitory effect on crop uncertainty or random interference, the rotation speed of the threshing cylinder could be adjusted in a small range (0.5 r/min). In order to further verify the effect of the controller, field tests were carried out. The feeding quantity was adjusted by adjusting the traveling speed of the harvester by changing the cutting width, i. e. the cutting width was increased from 6 rows to 7 rows. The results showed that the overall change trend of the record data curve of the rotational speed of threshing cylinder and walking speed of the combine harvester was in good agreement with the simulation results, and the speed response time was about 0.5 s, which can deal with the control delay problem well and realize the real-time control of the rotational speed of the threshing cylinder, ADRC-DMC controller could make the threshing cylinder achieve stable effect. © 2019, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.