The purpose of this master thesis is to analyse the effects induced by gravity compensators in robotic systems. Nowadays robotic research is more focused on attaining energy-efficient and safe solutions. For instance, they are key-aspects of robots that are required to interact with human workers in not confined environments. The introduction of a mechanism that passively compensates the joint torque caused by the weight of the robot may offer a valid solution. Relieving the actuators from generating the torques due to gravity has the consequence of decreasing the power consumption and allowing the possibility to reduce the size and weight of the actuators.