This paper deals with a method for static and dynamic modeling of a three-way pneumatic proportional valve actuated by means of a proportional solenoid, which can be applied in robust design, condition monitoring, and development of advanced control strategies. Test-beds for the experimental identification of the main physical parameters of the valve are described along with the proposed experimental methods. A mechatronic dynamic model of the valve is then presented, which considers the servo-solenoid as the electromagnetic subsystem, the moving parts of the valve as the mechanical subsystem, and the fluid parts for flow-rate control as the pneumatic subsystem. Finally, the proposed mechatronic dynamic model is validated by comparing the experimental and simulated diagrams for adsorbed current, spool position, and instantaneous flow-rate.

Flow and pressure transients in fluid transmission lines can be analysed starting from a modal approximation of the frequency domain irrational transfer matrix, relating pressure and flow rate at the line ends in Laplace transform. The obtained rational approximation can be converted in a state space representation and used in variable time step simulators to evaluate the influence of the line on fluid servosystems dynamics. Particular attention must be given to the causality, to the stability and to the energy passivity of the resulting line model.In this paper the application of a numerical approximation technique (Vector Fitting) to the frequency dependent transfer matrix describing the pipeline dynamics is proposed. The admittance matrix formulation is chosen, introducing an effective passivity enforcing technique, to ensure the energy passivity of the approximated matrix, thus preserving in the model the physical meaning of the real system.The rational approximation of the transfer matrix, combined with the passivity enforcement methodology, is applied to the study of the transient response of a single uniform line and of compound hydraulic line systems, showing the agreement between the simulation and the solution obtained with inverse fast Fourier transform.

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The dynamic analysis of a cam transmission derived from an engine valve train is performed in frequency and time domain, by means of a combined lumped-distributed parameters models, capable of predicting the effects of the higher harmonics of the cam lift profile on system performances, in particular as concerning the return spring device. Dynamic stiffness of the transmission in frequency domain and time history of contact force between cam and follower are evaluated, highlighting the limits of the transmission at high-speed camshaft operations caused by the spring behavior. The aim of the study is to developed a comparison on the performances of the cam mechanism working with the original mechanical spring from design or with a pneumatic return device based on a pneumatic spring and a pressure control circuit.

The paper presents a comparison of performance for a cam transmission of an engine valve train operating with a mechanical spring and with a return spring device that uses a pneumatic spring. Dynamic analysis of the cam mechanism is performed in the frequency and time domains employing a combined lumped-distributed parameter model capable of predicting the effects of the higher harmonics of the cam lift profile on system performance, in particular of the return spring device. Dynamic stiffness of the transmission in the frequency domain and time history of the contact force between cam and follower are evaluated. The limits of the traditional mechanical spring-closing system at high-speed camshaft operations are investigated, highlighting that they are mainly imposed by the internal resonances of the spring. The pneumatic spring is an improved replacement of the steel spring because of better dynamic behavior. Furthermore, the pneumatic return device allows preload tuning of the spring, which may increase transmission efficiency through proper control of the fluid pressure. Study of the pressure control circuit is also presented.