This paper presents a mathematical model of an axial piston pump/two-stage electrohydraulic controller combination. The controller uses swashplate position feedback and has been specially designed so that it is of low-to-moderate cost and so that it can respond quickly to control changes. The first stage of the controller makes use of a squeeze film damper and is dynamically stable. The model may be used for design purposes inasmuch as geometry and operating conditions can be varied over wide limits and the resulting dynamical behavior evaluated. Calculation of the dynamic response to a control current for the operating conditions and geometry of the valve shows close agreement with experiment.