In one example, a system for automatic control of the propulsive speed of a harvesting machine is provided. The system comprises a throughput sensor for determining an expected rate of crop harvested by the harvesting machine in dependence on a position of the harvesting machine and a conversion device configured to calculate a sequence of expected positions of the harvesting machine and, with the expected rate of crop harvested at a position of the harvesting machine, determine a predicted rate of crop harvested by the harvesting machine at the sequence of expected positions of the harvesting machine for use in an optimization problem. Further provided is a speed control device, configured to receive the data relating to the predicted rate of crop harvested at the sequence of expected positions in addition to at least one of data relating the operating state of the harvesting machine, cost function data or secondary condition data, to solve the optimization problem and generate at least one timewise successive sequence of speed commands for setting the propulsive speed of the harvesting machine； and an actuator configured to adjust the propulsive speed of the harvesting machine, the actuator receiving the first speed command of each sequence of speed commands and adjusting the propulsive speed of the harvesting machine.
