Page 563 - Mechatronics with Experiments

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JWST499-c07
JWST499-Cetinkunt
ELECTROHYDRAULIC MOTION CONTROL SYSTEMS 549
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The MATLAB code used to initialize the parameters and initial conditions for the
poppet valve is shown below. The dynamic model of the poppet valve is implemented in
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Simulink (Figure 7.100). Time domain simulation of the poppet valve model is shown in
Figure 7.101. In this simulation we did not include the preload on the poppet valve spring
in order to keep it sealed when the solenoid force is zero. As a result, when the solenoid
force is zero (time period from 0 s to 1 s), the poppet valve opens due to the line pressure. In
actual poppet valves, the spring would have initial preload to keep the poppet valve closed
despite the line pressure. This model can be used to simulate other poppet valve sizes by
simply specifying appropriate parameters. Load pressure is considered as constant in this
simulation. In a real application, the load pressure, that is the output port pressure of the
poppet valve, would be determined by the down-stream hydraulic circuit conditions.

% Poppet Valve parameters
Kleak = 0.0 ; % Leak coefficient
At = 0.0 ; %
Kfi = 1.0 ; % Solenoid current to force gain
mp = 1.0 ; % Poppet mass
cp = 20.0 ; % poppet damping
kp = 1000.0 ; % Poppet spring constant
x_preload = 0.0 ; % Poppet spring preload displacement
A1 = 0.01; % Areas
Ka2 = 0.01 ; % with saturation at 0 and A2_max
(no negative orifice area)
A3 = 0.01;
A4 = 0.001 ;
V2 = 0.10 ; % Volumes inside the valve
V3 = 1.0 ;
beta = 250 * 10ˆ3; % Bulk modulus
Cd = 100.0 ; % Flow coeffient scaled sqrt(2/rho)
ps = 3000 ; % p1 = 3000 psi
pt = 100 ; % 100 psi
pl = 100 ; % 100 psi
p20 = pt ; % Initial conditions on pressures
p30 = pt ;

Xp0=0.0 ; % Initial valve (spool) position and speed
Xpdot0= 0.0 ;

An example of a poppet valve (by Hydraforce Inc), which is two-way, normally closed
(when de-energized), proportional solenoid controlled, is shown in Figure 7.102. It shows
the valve, its installation to a standard manifold cavity, its symbol, as well as its steady-
state flow rate–solenoid current–differential pressure relationship (top right figure) and the
dynamic response characteristics as the frequency response input–output relationship (gain
and phase) between solenoid current and flow rate. Notice that for this particular poppet
valve, flow-rate to current relationship under a specific pressure differential across ports 1
and 2 is not linear. When de-energized, flow from port 1 to port 2 is allowed, but flow from
port 2 to port 1 is blocked by a check valve. This type of poppet valve is used in series with
a proportional four-way valve output line for load-holding (sealing) function. It “seals” the