Method for controlling power-transmission gear, system, and forest machine

A method for controlling a power-transmission device in a forest machine comprising a crane and a harvester head suspended from the crane, the method comprising:

• measuring a selected property of at least first and second trees with aid of observation means using electromagnetic radiation at a distance from the at least first and second trees to create measurement data for the at least first and second trees;
• storing the measurement data of the at least first and second trees in a register of the trees' measurement data belonging to a memory for controlling the power-transmission device;
• controlling the power-transmission device with aid of a software means, on a basis of the measurement data of the first tree, to create a change in a state of the power-transmission device before the harvester head contacts the first tree so that the power-transmission device transfers to a first operating device belonging to the forest machine an amount of energy optimized on the basis of the measurement data in terms of performing a selected operation;
• performing the selected operation of the first operating device using the amount of energy transferred by the power-transmission device after the change in state of the power-transmission device , in which the operation of the first operating device creates a change in the attitude, location, or state of the harvester head, or a combination of the aforesaid;
• controlling the power-transmission device at the second tree in the register on a basis of the measurement data of the second tree in the register;
• and
• repeating the foregoing steps on subsequent trees, wherein the second tree becomes a new first tree and a tree subsequent to the second tree becomes a new second tree for performing the foregoing steps.