Bond graph modeling of a hydraulic circuit on a whole-stalk sweet sorghum harvester

During operation of a whole-stalk sweet sorghum harvester, it was apparent that the load on two motors in series, driving two intermeshing chains called the gathering chains, was not distributed evenly. A bond graph model was developed and used to analyze the operation of the gathering chains subsystem and to determine design modifications which would improve operation. Simulated flow rate, line pressure, and driveline torque from the model were validated with experimental data taken from the harvester during operation. Analysis of the model revealed that 64% of the load was being driven by the first motor in the series and that removal of the external drain line of the second motor would help alleviate this condition. With removal of the drain line, pressure drop across the second motor in the series increased 10% in the simulation, compared to a 17% increase when measured on the harvester. Further analysis with the load driven by one motor showed that the gathering chains could be powered with one motor due to the low torque requirement. Model results showed that overall torque requirement was reduced 4% with just one motor. Due to the reduced plumbing and number of motors required, the one motor design was recommended.