Abstract: A PID controller has a parallel arrangement of a P-element, an I-element, and a D-element coupled to a first summation point for adding their respective output signals, a summation signal produced by the first summation point being employed for control of a variable. An actual value of the controlled variable is inputted to the parallel arrangement of the P-element, the I-element, and the D-element. The I-element is a series arrangement of a weighting section followed by an integrator, the I-element being coupled to the weighting section by a second summation point. The controller applies a time derivative of the actual value of the controlled variable to the second summation point, the second summation point subtracting the derivative from a signal outputted by the weighting section of the I-element.

Abstract: The present invention relates to a hydraulic secondary control system comprising a hydrostatic machine as a secondary unit which is connected to a pressure line in which an impressed pressure of approximately constant value is generated by a hydrostatic machine as a primary unit. The volume capacity of the secondary unit determines the torque delivered to a load and the torque needed by the load determines the speed of the secondary unit. When the desired speed and thus the volume capacity of the secondary unit is too high, the capacity exceeding the capacity of the primary unit supplying the pressure line, the pressure breaks down. To prevent this, the present invention provides to calculate a permissible capacity as defined by the rotary angle for the secondary unit in accordance with the nominal quantities of the primary and secondary unit.