A Novel Model for Dual-Control Hydraulic Rock Drill Based on Valve-Cylinder Coupling

The dual-control hydraulic rock drill employs a feedback mechanism between the spool and impact piston to generate periodic impacts, with its output efficiency governed by their coupled motion. This study presents a novel valve-cylinder coupled model and an experiment method for spool dynamics and impact process. Experimental results show that the model predicts impact piston stroke with a maximum error below 8% and an average error within 2%. Analysis based on the model reveals that the shorter duration of the impact process compared to the spool switching time causes post-impact velocity fluctuations, which weaken subsequent impact performance. To mitigate this, a model-based optimization strategy is proposed, which can eliminate velocity fluctuations and improve impact power about 3%. The approach provides an effective theoretical foundation for enhancing the performance and energy efficiency of hydraulic rock drills.