Page 524 - Mechatronics with Experiments

JWST499-Cetinkunt
JWST499-c07
510 MECHATRONICS Printer: Yet to Come October 9, 2014 8:41 254mm×178mm
pump (i.e., electric motor in industrial applications, internal combustion engine
in mobile applications), calculate the pump displacement requirement, D ,using
p
Equation 7.259. Select the proper pump given Q , P , D .
nl
s
p
D = Q ∕w in (7.272)
nl
p
Step 6: Given the calculated Q , P , Q , calculate the rated flow for the valve, Q ,at
nl s r v
its rated pressure ΔP for i = i using Equation 7.266. Notice that rated flow
v max
for a valve is defined at a standard pressure drop across the valve (i.e., typically
ΔP = 1000 psi for servo valves, ΔP = 150 psi for proportional valves) and at
v v
the fully shifted spool position (i = i ). Select the proper valve size based on
max
the calulated Q and assumed ΔP .
v
v
√
Q = Q nl ΔP ∕P S (7.273)
v
v
In summary, the load conditions determine the specifications:
Given {w ,(w , T )} (for linear actuator {V ,(V , F )}).

r
nl
r
r
nl
r
As design choices, pick D m hydraulic motor displacement (for linear actuator A c

cylinder cross-sectional area) and pick ΔP valve pressure rating.
v
Then calculate the rest of the sizing parameters: Q , Q , ΔP , P , D , Q , which are

nl
L
p
s
r
v
the size requirements for pump, valve, and motor/cylinder using Equations 7.259,
7.260, 7.266.
Component Sizing Algorithm 2
Step 1: Determine the performance specifications based on load requirements:
{w ,(w , T )} or {V ,(V , F )}
r
r
nl
r
r
nl
Step 2: Pick either displacement per unit stroke for the actuator (D or A ) or the supply
c
m
pressure, P . Let us assume we pick pump pressure, P .
s
s
Step 3: Pick the pressure differential to be delivered to the actuator to drive the load
ΔP , calculate hydraulic motor displacement (D ) or cylinder cross-sectional
m
L
area (A ).
c
D = T ∕ΔP A = F ∕ΔP (7.274)
m r L c r L
Step 4: Calculate Q from Equation 7.259 and Q at ΔP , P and i = i max from Equation
s
r
nl
L
7.266.
Q = D ⋅ w nl Q = A ⋅ V nl (7.275)
nl
c
nl
m
√
Q = Q 1 − (ΔP ∕P ) (7.276)
r nl L s
Step 5: Given the calculated value of Q , and given the operating input shaft speed of
nl
the pump w , calculate the pump displacement requirement, D , using Equation
p
in
7.259. Select the proper pump given Q , P , D .
p
s
nl
D = Q ∕w (7.277)
p nl in
Step 6: Given the calculated Q , P , Q , calculate the rated flow for the valve, Q ,atits
v
nl
s
r
rated pressure ΔP . Select the proper valve size based on the calulated Q and
v
v
assumed ΔP .
v
√
Q = Q ΔP ∕P (7.278)
v nl v s