Design and experimental validation of a variable-rate control system for organic fertiliser based on discrete element method — multi-body dynamics

A major challenge in excessive organic fertilisation in field crops is the inability to adjust the amount of fertiliser in real time, resulting in uneven fertilisation. We propose a variable-rate fertilisation technology for fermentation fertiliser using a propeller-blade crushing mechanism and a chain-row variable-rate applicator. A variable-discharge fertiliser device was initially designed, comprising a paddle-based fertiliser-crushing unit and chain fertiliser discharge unit. A theoretical model of fertiliser discharge device was designed, and the force acting on the chain plate and main factors affecting fertiliser discharge were investigated. Based on the theoretical results, a control model considering the sprocket speed, forward speed of the fertiliser box and amount of fertiliser discharged from the device was designed using 32 groups of organic fertiliser ground application tests. The adjusted coefficient of determination ( R 2 ) was 0.97 ( p < 0.01), indicating significance and applicability of precise control. The combined discrete element method–multi-body dynamics simulation was used to analyse the fertiliser transport process of the chain row in the fertiliser discharge model. The average speed of the fertiliser was 0.280 m s −1 , with a theoretical error of 8.9%, while the average error of fertiliser discharge was 9.3%. Results demonstrated that the established model could accurately and reliably control fertiliser discharge. The proportional integral derivative (PID) control parameters were adjusted based on the AMESim-Simulink control model. The fuzzy PID control algorithm was selected using overshoot and adjustment time as indicators. The control algorithm’s parameters were verified using a bench test. The system response time for variable fertiliser discharge was