The present robotic system finds general application in the field of robotic surgery and particularly in the field of minimally invasive surgery.  In minimally invasive surgery smaller incisions are made as compared to those in conventional surgery that require a very precise operation of the surgical tool.  Through these incisions surgical operations are carried out, including introducing of vision cameras (laparoscopy) for obtaining images of internal organs and transmitting them to a television monitor through which the surgeon can be guided to perform such surgical procedures. 
These surgical procedures through robotic surgery are performed remotely by using tele-operation stations connected to a robotic system via dedicated communication lines. 
Robotic systems include architectures designed to behave like a human arm, allowing a robot arm to be arranged in different positions.  These architectures are formed by one or several arms mounted on a supporting structure and formed by hinged members so they can be moved properly in the space to operate a tool, terminal organ or end effector, such as a gripper or other device to perform surgical operations.  Movement is driven by commands that are remotely received through the tele-operation station. 
Each of said arms is an articulated structure comprising several members hinged to each other and rotatably mounted to the supporting structure.  One example of robot arm architecture with articulated members is the robot known as Scara, with freedom of movement in the X and Y axes, although they are limited in their movements in the vertical axis Z, where simple and short-distance procedures are usually performed. 
The limitations of these architectures are typically overcome through an intensive use of complex electronics and mechanisms in order to provide a robotic system suitable for minimally invasive surgery.  This involves an undesirably costly robotic system due to complexity as a whole. 
Document US2003208186 describes a robotic mechanism with three degrees of freedom comprising a supporting structure to which an arm is slidably attached vertically.  The arm comprises a first member and a second member hinged to each other.  The first member is in turn hinged to the supporting structure and by means of it a tool can be positioned.  However, such architecture has the disadvantage that it does not allow the tool to be properly positioned in order to insert it by a surgical instrument (trocar). 
Document U.S. Pat.  No.  5,762,458 refers to a system for performing minimally invasive cardiac surgery procedures.  This system comprises articulated arms adapted to handle a tool in space.  Said arms have several degrees of freedom and, in one embodiment, they are provided with three motor driven joints (that can be driven in displacement and rotation), two passive joints and one motor driven joint that can be rotated for driving a tool placed at the arm end.  This robotic system has the disadvantage that it does not allow for a fully effective positioning of the tool through the incision in the patient.