Abstract: A work machine (1) comprises at least one structural element (21), at least one pressure medium operated actuator 22) for establishing at least one operation of the work machine, and at least one detection device (23) to determine the position of the structural element (21) of the work machine. An arrangement for controlling at least one operation of the work machine (1) comprises: a control valve arrangement (24) for controlling the actuator (22), and a control device (25) for controlling the control valve arrangement (24). The control device (25) is adapted to control said control valve arrangement (24) for adjusting the pressure and/or volume flow on the return line of the actuator (22) as dependent on the position of the structural element (21).

Abstract: A method and system for controlling a power-transmission gear in a forest machine having a harvester head includes measuring a selected property of at least two trees with aid of observation means on a basis of electromagnetic radiation at a distance from the trees being measured to create measurement data. The power-transmission gear is controlled by software on the basis of the measurement data to change a state of the power-transmission gear to optimize energy required to perform an operation of an operating device. The operating device uses the energy transmitted by the power-transmission gear (after the change in state of the power-transmission gear so that operation of the operating device create a change in the attitude, location, or state of the harvester head.

Abstract: A method for stabilizing at least one frame part of a forest work unit involves determining a moment applied by a payload of the forest work unit to a frame part to be supported and determining a magnitude and direction of at least one support moment needed at least for stabilizing the frame part on the basis of the moment applied by the payload to the frame part to be supported. An arrangement for stabilizing at least one frame part of a forest work unit comprises means for carrying out said determinations.

Abstract: A method for stabilizing at least one frame part of a forest work unit involves determining a moment applied by a payload of the forest work unit to a frame part to be supported and determining a magnitude and direction of at least one support moment needed at least for stabilizing the frame part on the basis of the moment applied by the payload to the frame part to be supported. An arrangement for stabilizing at least one frame part of a forest work unit comprises means for carrying out said determinations.