Development of an Electrohydraulic Bin Position Control System for Mobile Harvesting Equipment Using Bond Graphs 961798
Many of the advances in mechatronic design and electrohydraulic controls have not been fully utilized on mobile equipment. Many operations, like the positioning storage bins on most mobile vegetable harvesting machines are controlled by the driver with a manually operated directional control valve located in the cab. Most storage bins on harvesting machines are located behind the cab, often requiring the operator to look back to view the product and reposition the bin while driving the harvester. Frequently, because of distractions or visual obstructions, the operator can not advance or reposition the storage bin during operation thus causing the incoming harvested product to “back-up” into the grading and conveying systems on the machine. When the product backs-up on the machine, overfilling and excessive product damage occurs.
Using bond graph modeling and simulation, a control system to automatically position storage bins on mobile vegetable harvesting equipment was designed. The control system can be incorporated into new harvesting equipment as well as retrofitted on existing machines. This feature will not only reduce harvested product damage but clearly provide safety advantages over current practices of manual control since the operator will no longer be required to frequently adjust the storage bin position.
A prototype control system was fabricated and field tested during the summer of 1995. Three pickling cucumber harvesters modified with positioning control systems were evaluated over a three week period. A total of 810,500 kg (1,783,100 lbs) of cucumbers from 44.5 ha (111 acres) were harvested with the modified harvesters. Cucumber damage was documented by Vlasic Foods, Inc. throughout the season as well as during the test period. Damage of the cucumbers harvested with the modified machines averaged 7.0% (on a percent weight basis). Damage incurred during the previous six weeks before the same three harvesters were modified averaged 9.1%. This difference was statistically significant at the 5% level. Conclusively, the automated storage bin control system significantly reduced cucumber damage. This equates to a savings of more than $40/ha ($16/acre). On a larger scale, 55,456 ha (138,639 acres) of cucumbers were grown in the US in 1992 (1993 Census of Agriculture). If a 2% reduction in damage could be achieve on half of the US acreage, savings totaling more than $1,000,000 would be achieved for pickle industry each year.