| Based on the development trend of combine harvesters and the control of roller speed at home and abroad,In order to solve the problems such as the speed of the threshing roller chain drive of domestic combine harvester is much time-consuming;the belt drive is easy to slip and the maintenance cost is high;the control system is designed for a type of machine,and the speed of the drum can not be set according to the actual working conditions;this paper designs an electro-hydraulic proportional control of the speed of the combined threshing cylinder system.The core controller selects PLC,the core algorithm selects the PID control,replaces the existing chain transmission and the belt drive with the hydraulic drive,and realizes the adaptive control of the speed.The utility model has the advantages of quick response,simple structure,strong versatility and practicability.It is especially suitable for the drive and speed control of a large and medium combine harvester threshing cylinder.The main work and achievements of research are as follows:1.Referring to the relevant literature,this paper briefly introduces the current situation of the domestic and foreign research on the rotational speed control of the threshing drum of combine harvester;According to the technical requirements of the threshing drum and the effect of the rotational speed of the drum on the threshing performance,the overall scheme of the control system is determined.2.According to the model of the control system,the mathematical model of the valve controlled hydraulic cylinder and pump control motor circuit is established;According to the schematic diagram of the control system,the transfer function of the system is obtained,and then the open-loop transfer function and the closed-loop transfer function of the control system are derived;Based on the control function of the system,the stability of the system is analyzed.The PID controller with dead zone is designed,and the PID controller is simulated by Simulink.The simulation results show that the system can meet the control requirements.3.Based on the controller PLC,prepared the motor speed acquisition display program,with dead zone PID controller program;Designed the configuration control interface,through the way of Ethernet communication,the establishment of the pc machine and PLC communication;The system can set the most suitable roller speed according to the actual harvest of crops,or in order to meet the practical requirement,set the speed of the drum;Based on the system,the speed of the monitoring could be displayed and the parameters of the PID controller could be set in manual mode;At the same time,the data of system could be recorded and stored.4.Based on the pump motor closed test bed,the speed control system is tested as follows:(1)Increase the speed from 800r/min to 900r/min(800r/min to 860r/min);(2)Set the pressure to 30 MPa in the load pump circuit and add a load to the motor;(3)The load circuit pressure from 30 MPa upgrade to 35MPa;(4)The load circuit pressure from 35 MPa down to 25 MPa.Record the test data and the speed response curve,and record the test data.The results show that the system can track the input signal about 5S when the speed changes,The adjustment time is about 4.7s and the overshoot is 3.12%.When the load increased(load pump circuit pressure increased by 5MPa),adjustment time is 4.3s,the overshoot is 3%;load reduction(loading pump circuit pressure reduced 10MPa),the adjustment time is about 5s,the overshoot is 3.37%.The results of simulation test and bench test show that the speed control system designed by the institute is stable under the condition of no load or loading;The system is oscillated by the disturbance action;After a short time adjustment,it can return to the original balance working state.The system can realize the automatic control of the speed. |
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