Research On The Control System Of Corn Grain Harvester To Prevent The Blocking Of Threshing Drum

Corn is one of the three main food crops in China,and also one of the indispensable raw materials in food,medical,chemical and other fields.It has great economic value.At the same time,corn is also the largest food crop in China.Therefore,it is particularly important to harvest corn with high efficiency and low loss by machine.However,most of the corn harvesters in the market are faced with the problems of easy blockage,difficult cleaning and low efficiency.Some scholars at home and abroad use MCU,PLC and other processors as the core to build the harvester working condition monitoring system,but it can only monitor,early warning,auxiliary role,specific also need human operation.Therefore,in view of the problem of corn grain harvester threshing drum blockage,this paper analyzes the relationship between the harvester engine power curve and header and drum blockage,expounds the relationship between the harvester engine power,engine speed,drum speed and blockage,and develops a set of corn grain harvester threshing drum prevention system based on PLC as the core controller The system can automatically adjust the feeding amount and drum speed when the detected drum speed changes more than 10% of the preset speed;the system is carried on the modified John Deere harvester for field test to verify the stability and reliability of the system.The main contents and conclusions of this paper are as follows.(1)First of all,read the relevant literature about corn grain harvester at home and abroad.After analyzing the fault situation of corn grain harvester at home and abroad,we know that the main reasons for the blocking fault are that the harvester is easy to block in the threshing drum,the feeding amount is too large due to the excessive forward speed,the engine speed decreases due to the increase of system load,and other operating parts can not work normally In addition,improper matching of operation parameters between feeding amount and drum speed,concave clearance,unreasonable design of threshing elements such as threshing drum will also cause drum blockage.Therefore,aiming at the problem of drum blocking,a set of electro-hydraulic proportional closed-loop control system is developed to adjust the drum speed and feeding amount,so as to prevent the drum blocking of corn grain harvester;the hydraulic schematic diagram of feeding amount and drum speed control system is drawn,and a worm concave clearance adjustment mechanism is designed,which uses DC motor to drive worm to realize clearance adjustment.(2)The hydraulic principle diagram of the hydraulic proportional control system and the system block diagram of the proportional control system are drawn.According to the parameters of the harvester system,the parameters of the proportional valve and other components are calculated,and other hydraulic and electric control components are selected.The parameters of each component are sorted out,and the whole transfer function of the proportional control system is calculated according to the parameters,and the overall circuit diagram of the system is drawn,and the electric control box is prepared.(3)Matlab / Simulink is used to simulate the system.The initial signal of the system is set as step signal,and the sampling time is set as 10 s.The time domain response curve of the system is obtained.In order to eliminate the oscillation of the curve in the convergence process,the PID adjustment algorithm is added to the system,and the parameters of the feeding amount and the roller speed system are set respectively to generate the system Bode diagram.In addition,the ladder diagram language is used to compile the system software program in PLC to realize the sequence adjustment of the system.(4)The electro-hydraulic control system was loaded on the harvester for field test,which was mainly divided into two parts: threshing model test and control system verification test.The data accumulation can be used to establish a large database of harvester operation and component design,which can guide the operators and manufacturers to operate and design the harvester reasonably.According to the relevant requirements of national standard dg / 015-2009 "corn harvester" for agricultural machinery,test whether the electro-hydraulic proportional control system works normally.By analyzing the relationship between the power curve of harvester engine and the jam of drum and header,this paper puts forward a scheme to prevent the jam of harvester drum,and develops a set of electro-hydraulic proportional closed-loop control system to adjust the feeding amount and drum speed during operation.At the same time,the concave clearance is adjusted by controlling the positive and negative rotation of the DC motor;the simulation is carried out in Matlab / Simulink,from the generated Bode diagram of the system,we can see that the system has good rapidity,and the response time is less than 1s;the sequential adjustment program of the system is written in PLC.At the same time,the relationship curves between engine speed change and feed rate,drum speed and concave clearance were obtained,and the mathematical models between engine speed change rate and other operation indexes(Y1 ～ Y5)and feed rate,drum speed and concave clearance(x1 ～ x3)were obtained.By solving the mathematical model,the optimal parameters of harvester operation are obtained.According to the box line diagram of the solution distribution,the optimal feeding amount is about 12 kg / s,and the corresponding forward speed is 4-5km / h;the optimal drum speed is mainly distributed between 330 ～ 370 rad/min,and the solution of 360rad/min is the most,and the optimal concave clearance is about 30 mm.At the same time,according to the box line diagram,we can also see the impurity content The corresponding range of concave clearance is very wide,which indicates that the impurity content is not sensitive to the change of concave clearance,and the gap change between 24 ～ 34 mm can meet the requirements of impurity content under the national standard,while the change rate of engine and roller speed is obvious to the parameter change,so the most stable working parameters of the system can be obtained as follows:forward speed 5km / h,roller speed 360 rad / min,concave clearance 30 mm.