Abwucl-Thir paper deais with a new mcehaniral Rirth Slhlulalor ~Hirthhlhli. Curmnll) a\ailable hirth simulators prwidc manikins that include ne*-bum head and malcmal pelti\ hut he) du nut produce the motemenls 4 the iiew-horn in the mother's peltis. furthermore a\aililble maternal pchk do not include intrdare prewure and are not enough rralisiir to simulate maternal pchir muwlw. In summar), thew Fimuhtors do not help \ludentr to prartice the ccstures the! should safel! w e 10 help lhe mu-him in nwnial and at-risk 4iuatiuns uf deli$w).The uriginalit) of our mechanical birth simulator, i\ to pro\ide il \!\lcm tu mimic the last rkp of the instrumentill d e h c g , to inrurc a safe training or junior oh\lrlririanr and lo 1 , -I new techniques in obrlctrim practice.'lhc nca mechanical birth ~imuifitor is rompmed of three p a r k a phyiral neu-horn head and a maternal pel,i\ munikin, an interface pressure s)stem, and a pneumatic uckator that dwclops an arthe nsistanre Driven 11) a wmputer, the simulator can \imulale the ccmtradiunr, the interfwe p m w m applied in the new-horn head and mimic hirlh complication\.Krywurds . .4Iechonirol binh rimuloror, interfurlure prcwure (emon ond uh,lrmrir immmnwnm,
PWM (Pulse width modulated) solenoid valves possess the advantages of low cost, high flow rate gain, and simple structure. However, the use of a PWM solenoid valve causes both discontinuity and nonlinearity of the flow rate; this results in difficulties of modeling and of control. This paper presents our work on modelling a pneumatic PWM solenoid valve for engineering applications. Two models are presented: one is the instantaneous mass flow rate model which can be used in the simulation to study the dynamic behavior of pneumatic PWM control systems; another model is the equivalent mass flow rate model which is developed for facilitating the synthesis of pneumatic PWM servomechanisms. An equation for determining the maximum operating modulation ratio of the PWM solenoid valve is also presented. Simulated results using the established models are compared with the experimental results for both the static characteristics of a PWM solenoid valve and the dynamic behavior of a system composed of a PWM solenoid valve and a constant volume chamber.
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