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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.

This paper summarizes the study of the applicability of optimal control theories to the design of a pressure regulator for an axial piston pump for which state estimation and advanced control laws can be computed. Considerations are presented for the application of linear optimal control techniques where a weighted, quadratic performance index is minimized. The straight linear optimal regulator was augmented by the first integral of the output pressure to make the system sufficiently robust and to yield a controller that offsets constant or slowly varying flow disturbances. The paper describes the dynamic properties of the pump and their relationships to the available control resources in the form of state's peak values and the power required. Variations in root locations and state peak values for step response of the optimally controlled pump as a function of variations in performance indices are presented and used as a design tool.

A mathematical model of a dynamically stable flapper-nozzle pilot valve has been used in conjunction with the second stage of a flow control valve that comprises a single spool. The model has been used to calculate the valve gain and the dynamic response of the component parts. Real-time and frequency response results have been compared with those when using a two-spool version of the same type, each of the two spools being identical to the spool used in the single-spool version. It is shown that the dynamic response is improved significantly when the single-spool replaces the two-spool version.