In laparoscopic surgery, instruments are inserted into the abdomen through small incisions in order to conduct an operation. A straight rigid instrument through one incision has four degrees-of-freedom [1]. Theoretically, the area that the instrument tip can reach inside the abdomen is a cone-shape space [2], but the range of motion (ROM) of the instrument is limited to a certain space during operation, and determined by the inserted length and the pivoting angles of the instrument. Based upon the position and time, the total path length, velocity, acceleration, and movement smoothness of instruments can be calculated to evaluate surgical skills [3,4]. However, ROM of an instrument and its relative position to the operation platform have not yet been clearly understood or investigated.
In order to pursue the goal of reducing patient trauma, new surgical approaches have emerged, e.g., single-incision laparoscopic surgery (SILS)...
