Feed roll control system for a forage harvester

A system for controlling the position of one or more feed rolls in a forage harvester, said harvester comprising at least one fixed feed roll arranged to rotate around a rotation axis which is stationary with respect to a chassis of the harvester, and in cooperation with said at least one fixed feed roll, a movable feed roll arranged to rotate around a rotation axis which is movable towards or away from the corresponding fixed roll, the system comprising:

• at least one piston/cylinder arrangement, arranged so as to control the movement of said movable feed roll towards or away from the corresponding fixed roll,
• a hydraulic pressure source and at least one hydraulic connecting line between said source and said piston/cylinder arrangement,
• at least one valve means arranged in connection with said hydraulic line for directing hydraulic fluid towards said piston/cylinder arrangement, so as to actuate movement of said movable feed roll,
• a means for measuring data related to the driving force exerted on said movable feed roll,
• a control unit, configured for receiving said driving force data and further configured for calculating a required pressure in said piston/cylinder arrangement as a function of said driving force data, and for sending out command signals for actuating said valve means in order to obtain said required pressure.