A square baler comprising a controller for controlling the operation of the baler in dependence on the first, second and third signals representing the mass of a bale, the force of the piston of the baler, the energization of the actuator respectively and an input target value for the mass of the bale wherein the first signal is fed back in a first control loop and compared with the target weight to generate a target force, the second signal is fed in a second control loop and compared with the target force to generate a target energization, the third signal is fed in a third control loop and compared with the target energization to control the energization of the actuator.