Development and performance evaluation of an electric-hydraulic control system for subsoiler with flexible tines

Subsoiling is primary practice in conservation tillage fields, as it disrupts compacted soil hardpans that restrict crop root growth and water infiltration. Subsoiler with flexible tines presents effective obstacle avoidance and draft force reduction, but the undesired depths, much less than target value, are observed during tillage operation due to the considerable variation in soil resistance. Therefore, an electric-hydraulic control system for subsoiler with flexible tines was developed and a novel method for detecting tillage depth was described. The performance of the electric-hydraulic control system was evaluated in soil bin experiment by the detecting accuracy of the tillage depth and the operation quality (qualified index, distribution uniformity of tillage depths and draft force reduction). The detecting accuracy of the electric-hydraulic control system was determined at target depths of 25 and 30 cm, by testing tillage depths and comparing with manual measurement. The values obtained by the control system differed from manual measurements by less than 3.2% (3.2% at 25 cm; 1.9% at 30 cm), indicating high accuracy. The operation quality of the electric-hydraulic control system was evaluated for the working speeds of 1.4, 2.0, 2.6 km/h at target depth of 30 cm, by testing the tillage depth, draft force obtained with and without the electric-hydraulic control system. Treatments without the electric-hydraulic control system (CP) were five types of constant hydraulic pressure, respectively 2.0 MPa (CP 2.0), 2.5 MPa (CP 2.5), 3.0 MPa (CP 3.0), 3.5 MPa (CP 3.5) and 15 MPa (CP 15). Treatments with the electric-hydraulic control system (AP) were adjustable hydraulic pressure with the range of 2.0-3.5 MPa. Results indicate that flexible tine with AP created more regular cutting cross-section and acquired relatively consistent tillage depth. The qualified indexes of tillage depth (QI) were respectively 97.5%, 98.2%, and 96.7% at the forward speeds of 1.4, 2.0, 2.6 km/h. And mean tillage depths with AP were respectively 29.54, 29.53, 28.13 cm, closely to target depths. The distribution uniformity of tillage depth with AP was better than CP. Furthermore, draft force increased at the area with high soil resistance, flexible tines with AP experienced a relatively more stable rise and obtained draft force reduction of 18.17%, 18.35%, and 25.89% at three forward speeds. The results demonstrate that the developed system can be used to improving the tillage quality for subsoiler with flexible tines.