Dynamic analysis and reliability design of round baler feeding device for rice straw harvest

The feeding device of steel-roll round baler provides an intermediate link between the compression chamber and the pickup device. A discrete element method (DEM) was used to simulate the rice straw feeding process. By differentiating the surface of jaw plate and analysing the force vector on each part, the forces on piston rod of lifting hydraulic cylinder were obtained by integral calculation. Exponential models for the mean force on piston rod and torque on feeding roller were established with increasing throughput. The displacement of piston rod represented the feed opening. When piston rod displacement was in the range 0-30 mm, there was a significant decrease in the mean values of force on the piston rod and torque on the feeding roller with increasing feed opening. This unloading effect was not obvious when the displacement exceeded 30 mm. To improve reliability, safety factors for the feeding device were calculated using FEM simulations at different values of displacement and throughput. The variation of mean force was determined with safety factor of 1.3. A hydraulic cylinder drive circuit was designed with an accumulator. Rice straw baling experiments were carried out and the performance was in basic agreement with the DEM simulations. The feed opening increased automatically once the straw throughput rate surged. This reduced the peak load, avoid blockage, and protected the feeding device. The relationship obtained between feeding load and straw throughput rate provides the basis for the design of an automatic control system for a baler.