System and method for controlling a robot

A control system for a robot (1), which robot comprises at least three setting devices (2, 3, 4) which can be extended or shortened in the longitudinal direction, each setting device being directly or indirectly secured in a fixed frame (6) via a first joint (20, 30, 40) so that each setting device is pivotable in all directions in relation to the frame and that each setting device is attached at one end in a movable positioning head (8) via a second joint (21, 31, 41), and also a rigid arm (10) joined to and emanating from the positioning head and arranged between the setting devices, the arm being radially guided but axially displaceably journalled in a universal joint (12) relative to and rigidly connected to the frame, each setting device being provided with a length sensor (LS1, LS2, LS3), said sensors forming a part of a control system (S1) for controlling the location (X, Y, Z) of the positioning head in the work space of the robot characterized in that the control system cooperates with a feedback control system (R2) arranged to correct the location (X, Y, Z) of the positioning head in the work space and that the control system (S1) and feedback control system (R2) operate in accordance with different coordinate systems.