Page 536 - Mechatronics with Experiments

JWST499-Cetinkunt
JWST499-c07
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T
ΔP P
cmd
i
Amp
Valve
Pressure
sensor K = K + K –1 + K –1
–1
–1
t s a l
V
i
M
K K K
s Actuator a l
V
l
A
Valve c
ΔP K Q ΔP
cmd 1
K K t c
sa q
A A S
c c
Amp Actuator and compliance
K
pq
K
fp
Pressure valve
FIGURE 7.91: (a) Components, and (b) linear block diagram model of a force (load pressure)
servo controlled one-axis electrohydraulic motion system.

3. Leakage flow rate in the valve is also modeled as a linear relationship between load
pressure and leakage flow rate (K ).
pq
4. Fluid compressibility is neglected.
5. The load inertia and cylinder inertia are neglected.
6. Compliance of the actuator to base mounting, and compliance of the actuator to
load connection are neglected for closed position controlled hydraulic system model
(K ⟶ ∞, K ⟶ ∞). In a closed loop force control system, the combined effect
s
a
of all the compliances (K , K , K ) are taken into account with the K term.
a
t
l
s
In the linear block diagram models, the symbols have the following physical meaning:
K is the amplifier command voltage to current gain,
sa
K is the valve solenoid current to flow rate gain,
q
K is the pressure gain,
p
K pq is the leakage gain,
A is the cylinder cross-sectional area (assumed to be equal areas on both sides),
c
K is the position sensor gain,
fx
K is the pressure sensor gain,
fp
Q is the compliance flow.
c