As previously mentioned, the operating states of the impactor can be broadly divided into at least four categories, with finer divisions reaching more than ten. Clearly, these frequent state transitions present certain challenges for simulation and solution, as each transition involves issues such as state recognition, state initialization, and errors arising from the transition itself. For example, the structure of a specific impact mechanism dictates that the control oil circuit for valve reversal is engaged when the piston has traveled 2 cm during its return stroke. However, most simulation programs can only detect when the piston’s return stroke exceeds 2 cm, at which point the state transition begins. Clearly, the range of this ‘exceeding’ determines the error in state transitions, and as the number of state transitions increases, the accumulated error becomes larger.