a hydrostatic axial piston machine employs a swash plate construction in which the diagonal position of the swash plate can be controlled by at least one positioning piston pressurized with a control pressure . a control valve is in a line which leads to at least one positioning piston . a simple electrical - hydraulic control of the swash plate can be accomplished by the electrical actuation of the control valve . the control valve may be in the form of a rotary disk valve which can be actuated by a stepper motor .