Control system for a work machine and method for controlling a hydraulic cylinder in a work machine

A method for controlling a hydraulic cylinder (108, 109, 110) of a work machine (101 ), which hydraulic cylinder is adapted to move an implement (107) which is subjected to a load (116), the hydraulic cylinder being controlled by a hydraulic machine (204), said method comprising:

• detecting that a lowering movement of the implement is initiated, and of before the lowering movement takes place driving the hydraulic machine (204) in a first rotation direction so that a first line (220) which connects the hydraulic machine (204) to said first side (208) of the piston (218) of the hydraulic cylinder is pressurized, which side is opposite a second side (212) on which said load acts.

A method for controlling a hydraulic cylinder (108, 109, 110) of a work machine (101) for the purpose of moving an implement (107) which is connected to the hydraulic cylinder, a hydraulic machine (204) providing the hydraulic cylinder with pressurized hydraulic fluid, said method comprising:

• detecting a load (116) acting on the implement (107);
• comparing the size of the detected load with a predetermined load level, and, if the detected load lies below the predetermined load level, bringing the piston-rod side (212) of the hydraulic cylinder into flow communication with the piston side (208) so that hydraulic fluid coming from the piston-rod side (212) is brought to the piston side (208) without passing through the hydraulic machine (204).

A method for springing a movement of an implement (107) of a work machine (101) during movement of the work machine, at least one hydraulic cylinder (108, 109, 110) being connected to the implement for controlling its movements, said method comprising:

• delivering such a pressure to the hydraulic cylinder that the implement is brought into a basic position;
• and
• bringing a first port (220) of the hydraulic machine (204) into flow communication with a piston side (208) of the hydraulic cylinder via a first line (210) and a second port (222) of the hydraulic machine (204) into flow communication with a piston-rod side (212) of the hydraulic cylinder via a second line (210), and of, in the event of a disturbance which results in an upward movement of the implement, supplying a corresponding quantity of hydraulic fluid to the hydraulic cylinder and, in the event of a downward movement of the implement, draining a corresponding quantity of hydraulic fluid from the hydraulic cylinder.

A control system for a work machine (101) comprising:

• a first subsystem (707, 709) for performing a first work operation and a second subsystem (731) for performing at least one second work operation;
• said first subsystem comprises an electric machine (202), a hydraulic machine (204) and at least one hydraulic cylinder (108, 109, 110), the electric machine (202) being connected in a driving manner to the hydraulic machine (204), the hydraulic machine (204) being connected to a piston side of the hydraulic cylinder via a first line and a piston-rod side of the hydraulic cylinder via a second line, the hydraulic machine being adapted to be driven by the electric machine and supply the hydraulic cylinder with pressurized hydraulic fluid from a tank in a first operating state and to be driven by a hydraulic fluid flow from the hydraulic cylinder and drive the electric machine in a second operating state;
• said second subsystem (731) comprises a drive unit (734) and a hydraulic actuator (732), the drive unit (734) comprising an electric machine (738) and a hydraulic machine (736), the electric machine being connected in a driving manner to the hydraulic machine, the hydraulic machine (736) being adapted for flow communication with the hydraulic actuator (732), and a means (748, 750, 756, 758) being adapted for controlling the movement of the hydraulic actuator (732).