1. A method for assessing the positioning accuracy of a medical robot arm that includes at least one joint and a computational unit operatively coupled to the at least one joint, the computational unit configured to access a rigidity model corresponding to the robot arm, the method comprising: using the computational unit to calculate and assess a rigidity of the robot arm, said rigidity calculated based on the rigidity model; calculating a working space which can be traveled by the robot arm based on the calculated rigidity and a predetermined minimum rigidity; and determining if the calculated working space includes a space necessary to perform a specific task.