Tractor mounted agricultural mowers are usually powered by PTO driveline of the tractor. The power consumption depends on the driving speed, but it depends on the particular mower used and on grass field conditions. In mowing operation, the power of the diesel engine is split mainly to propulsion and rotation the mower parts. By measuring the torque of PTO shaft it is possible to control the power split in these two lines, not freely, but within certain constraints. In this paper, we study an automatic control system that regulates power consumption of the mower, by measuring the torque and RPM in the PTO shaft and controlling the forward speed of a robot tractor. The special interest in this study was the robot tractor, that enables autonomous mowing operations and if there is no human onboard monitoring faults of the mower, there is more demand that automation tries to protect the mower system and overload situations. In the experiments, forward speed was limited to range from 0.8 to 2.2 m/s and the setpoint for the power was set to 9 kW. The developed control system was able to control the power even in stepwise test patterns. Autonomous navigation was used in the robot tractor, to keep mowing width constant in 2.5 m.
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