Method and an arrangement for controlling a rock drill

A method for controlling at least one drill parameter when drilling in rock with a rock drill, said rock drill comprising an impulse-generating device arranged to induce shock waves in a tool acting against the rock with a percussive force generated via a percussion pressure, a rotation-generating device arranged to supply a torque to an impact device with a rotation generated via a rotation pressure, and a pressurisable damping chamber arranged to at least partially regulate contact of the rock drill with the rock via a damping pressure in the damping chamber,

• wherein said method includes the steps of:
• determining a first parameter value (P1) representing the damping pressure (D),
• determining a second parameter value (P2) representing the rotation pressure (R) of the drill bit,
• determining a deviation (ΔR) between the above second parameter value and a rotation pressure reference value (Rref),
• maintaining or changing a damping pressure reference value (Dref, Dref1, Dref2) in dependence on said deviation, and
• regulating the percussion pressure (S) based on a function of the first parameter value (P1) and the damping pressure reference value.