Re: help on sf_electrohydraulic.mdl

On Jan 21, 2:09 am, "tippana " <sreekanth3...@xxxxxxxxx> wrote:
hrh1818 <hr...@xxxxxxx> wrote in message <457d6191-7fb6-

4781-a95a-34e22582a...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>...

On Jan 18, 8:23 am, "tippana " <sreekanth3...@xxxxxxxxx>
wrote:
well thanks for the reply i did infactgo through the
theory
mentioned and i am currently building a new model. but
what
i still cannot understand that how can i control the
rise
time or Ton. so thats why i had asked about how i could
change this 50 hz pulse signal. what i want o tknow is
in
the original model ho is this pulse being generated
every
20 ms. the rest of the equations and the stateflow
logic is
clear.

The detailed Mathworks model uses the variable Tpwm to
specify the
value of (On Time + Off Time) and in the Mathworks model
Tpwm = 20
milliseconds. The value of Tpwm is set in a Matlab
Command Window
with a Tpwm = 0.020; command and stored in the Matlab
Workspace. See
Equation 8 in the Mathworks detailed model and the
accompanying
discussion for the source of this statement. Notice in
Equation 8 ton
and toff are the simulation times at which the solenoid
valve is
turned on and off.

Equation 8 is repeated here for convenience. toff
= ton +
duty_cycle*Tpwm/100;
The length of time the solenoid valve is on is equal to
duty_cycle *
Tpwm/100.
For example if ton = 0.8 seconds at the beginning of a
cycle,
duty_cycle = 40% and Tpwm = 0.02 then toff = 0.808
seconds.

During the solenoid valve's transition from the on state
to the off
state the value of ton for starting the next cycle is
updated. The
state chart uses " [t > toff] /ton += Tpwm: " line of
code to
accomplish this.

Howard

regarding the model i actually have measured the current
graph of a solenoid controlled by pwm and here what i
find
is that normally such fast actuators can damage
system.the
solenoid current i measured reaches its maximum level in
atleast 8 -10 sec then the value of the resistance
makes it
stay for 5 sec and then we switch over to hold current
so
in actual the Ton is normally of the order 15-20 sec at
maximum current and then pwm for 20 sec. so the fastest
magnetic solenoid application is in paper management
system
where these solenoids work at 72000 cycles per sec or
with
a pulse period of 72 msec out of which ton is 30 sec. i
got
the data from kendrion thoma magnet so what i want to
know
is if we are implementing any pwm solenoid control
practically we cannot have the current rising to 2.5A in
just 3sec as shown by the simulation curve but as
verified
it takes atleast 8-10 ms . i also think u are right
about
the model not working. anyways it does not matter so how
can i control or change the pulse period because i want
o
run several simulations to test the current rise graph.
i also apologize if u think i am still foolish and i
cannot
getthe correct point but according to my understanding
this
is what i have found out and understood
thanks

well i had actually changed Tpwm parameter and there can be
nomore clearer explanati0on than yours one last doubt which
remains is the ascent of the magnetic curve to reach Ipull
is still within 3ms is there a way to control that because
such a thing is not possible. even though we can change the
Tpwm parymeter it only affects the cycl pulse time i also
experimented changing the magnetic data but it has no
affect ?ven with practical data in place . so does it mean
from the stateflow chart timin gis out of our control even
if we were to implement a time delay
thanks for the explanation

My first suggestion is you first try making a large increase in the
mass of the armature of the solenoid. A larger mass means a lower
acceleration and a longer closing time. In the meantime I will take a
look at the magnetic equations to see if anything can be changed
there. No guarantees. Otherwise I am completely mystified at to why
the solenoids you tested are taking seconds for the armature to close
and the Matlab's Simulink model shows milliseconds for closing time.

Howard.
.

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