This paper addresses the bistable motion that occurs in hydraulic rock drills during drilling by applying a nonsmooth-system-based bistability control method to the drill's hard-impact system. This method enables the transition from undesired attractors to desired attractors via continuous pathways without affecting the original state of the system. First, a multi-degree-of-freedom dynamic model of the rock drill is established based on the dry friction rock theory, examining both viscous and non-viscous movements. An analysis of unidirectional bifurcation with respect to impact frequency reveals that viscous motion can easily induce chaos in the system. When ω = 3, the system is in the optimal motion state p1q1r1, and the rate of penetration (ROP) reaches its maximum value. In the high-frequency range, the system exhibits poor stability, showing chaotic behavior and bistability. Bidirectional bifurcation analysis at ω = 9, conducted with different initial values, reveals two bistable attractors, p0q1r1 and p1q0r2. The global attraction domain of the p1q0r2 attractor accounts for up to 90.6%. Subsequently, linear and nonlinear control methods are employed to facilitate transitions between these two attractor regions. Additionally, a pseudo-arclength continuation method is adopted for path tracking to determine the parameter domains a and b suitable for the proposed control strategy. Numerical simulations show that controlling parameters such as impact force amplitude, offset, or collision spacing can effectively alter the attractor states. Finally, the validity of the model is verified experimentally. The hydraulic rock drill exhibits bistable motion, which is attributed to unstable stress waves generated by the impact of drill tools on heterogeneous rock during high-frequency drilling. Furthermore, improper matching among the impact force, propulsion force, and buffer force causes jumps in hydraulic pressure frequency at the moment of direction reversal, which consequently alters the initial working parameters of the rock drill.
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