1. A robot system comprising a robot having a movable part to which a sensor is attached to monitor at least vibrations, and a control device which controls the operation of the robot, whereinthe control device comprises a sensor coordinate system calculation unit which calculates a position and an orientation of the sensor by causing the robot to perform a predetermined operation, and
the sensor coordinate system calculation unit comprises an operation parameter optimization unit which is configured to obtain a combination most suitable for calculating the position and orientation of the sensor, from a plurality of combinations of modified values of a predetermined type of operation parameters, by making the robot perform the predetermined operation, successively using each of the combinations, and wherein
the operation parameter optimization unit is configured to
calculate the position and orientation of the sensor based on data of a physical quantity representing the vibrations, the data output from the sensor when the predetermined operation is performed by the robot in accordance with each of the combinations, and calculate the physical quantity acting on the sensor based on the calculated position and orientation of the sensor and on the position and posture of the robot during the predetermined operation, and
determine a combination in which the calculation precision of the position and orientation of the sensor becomes the highest, from the plurality of combinations, based on the data output from the sensor and the calculated physical quantity acting on the sensor.