Terminology: "open-loop" vs. "closed-loop"

On 17 Ù86Ù88Ù81Ù85ØA8ØB1, 09:54, Rick Armstrong <bo...@em=
ail.com> wrote:

Please forgive us for any disturbance, but we have an important
subject to address to you regarding FAITH, and we Donâ80�t intend to
overload your email with unnecessary messagesâ80¦

The Judicial System in Islam : Its Legal Basis and Islam Rulingmasjed

By The Editorial Team of Dr. Abdurrahman al-Muala (translated by
islamtoday.com)

Defining the Judicial System and its Legal basis

The judicial system in Islam is a system for deciding between people
in litigation with the aim of settling their disputes in accordance
with the injunctions of the Divine Law, injunctions that are taken
from the Quran and Sunnah.

All of the Messengers of God (may God praise them all) acted as
judges. God says:

â80�And remember David and Solomon, when they gave judgment concerning
the field when peopleâ80�s sheep had browsed therein at night, and We
were witness to their judgment. And We made Solomon to understand the
case. And to each of them We gave good judgment and knowledge.â80� (Qu=
ran
21:78-79)
God also says:

â80�O David, verily we have placed you as a successor on Earth, so jud=
ge
between people in truth, and do not follow your desires for it will
mislead you from the path of God. Verily, those who stray from the
path of God have a severe punishment because they forgot the day of
reckoning.â80� (Quran 38:26)

Prophet Muhammad, who came with the final and eternal Message, was
ordered by God to pass judgment in disputes just as he was ordered to
spread the word of God and call people to Islam. This is mentioned in
the Quran in a number of places. God says, for instance:

â80�So judge (O Muhammad) between them by what God has revealed and do
not follow their vain desires, but beware of them lest they turn you
away from some of what God has sent down to you.â80� (Quran 5:49)

God also says:

â80�E2�A6And if you judge (O Muhammad), judge between them with ju=
stice.
Verily, God loves those who act justly.â80� (Quran 5:42)

And He says:

â80�But no, by your Lord, they shall have no faith until they make you=
 (O
Muhammad) judge in all their disputes and find in themselves no
resistance against your decisions and accept them with full
submission.â80� (Quran 4:65)

The Sunnah also provides for the legal basis of the Islamic judicial
system. It is related by Amr b. al-Aas that the Prophet said:

â80�If a judge gives a judgment using his best judgment and is correct=
,
then he receives a double reward (from God). If he uses his best
judgment but makes a mistake, then he receives a single
reward.â80� (Ahmed)

Godâ80�s Messenger said:

â80�You should not wish to be like other people, except in two cases: =
a
man who God has given wealth and he spends it on Truth and another who
God has granted wisdom and he gives verdicts on its basis and teaches
others.â80� (Saheeh Al-Bukhari, Saheeh Muslim)

Many scholars have related to us that there is consensus among Muslims
on the legal status of the judicial system in Islam. Ibn Qudamah says:

â80�The Muslims are unanimously agreed that a judicial system must be
established for the people.â80�
The Islamic Ruling Concerning the Judiciary

The jurists agree that the duties of the judge are an obligation that
must be carried out by society. If some members of society carry out
this duty, it is sufficient for everyone. If, on the other hand,
everyone neglects it, then everyone in society is sinful.

The proof that these duties are obligatory comes from the Quran:

â80�O you who believe! Stand out firmly for justice...â80� (Quran=
 4:135)

It is only necessary for a small number of individuals to perform
judicial duties since judicial concerns come under the broad duty of
enjoining what is right and forbidding what is wrong. It is not
obligatory for every individual to carry out this duty as long as some
people are doing so.

The affairs of the people will not be correct and upright without a
judicial system. It is, consequently, obligatory for one to exist,
just like it is necessary to have a military. Imam Ahmad, one of the
greatest and most well-known scholars of Islam said:

â80�People have to have a judicial authority or their rights will
disappear.â80�

The duties of the judiciary include enjoining what is right, helping
the oppressed, securing peopleâ80�s rights, and keeping oppressive
behavior in check. None of these duties can be performed without the
appointment of a judiciary.

A judicial system is a necessity for the prosperity and development of
nations. It is needed to secure human happiness, protect the rights of
the oppressed, and restrain the oppressor. It is the way to resolve
disputes and ensure human rights. It facilitates enjoining what is
right, forbidding what is wrong, and curbing immoral behavior. In this
way, a just social order can be enjoyed by all sectors of society, and
every individual can feel secure in his life, property, honor, and
liberty. In this environment, nations can progress, civilization can
be achieved, and people are free to pursue what will better them both
spiritually and materially.



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�94â80�E2�94-


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On Mon, 16 Nov 2009 23:54:45 -0800, Rick Armstrong wrote:


Looks like I should be reviewing that article for clarity.  Goody, more
work!

In an ideal world you wouldn't have that complicated a setup.  In an
ideal world you'd just drive your desired signal into the controller, and
look at the output from the plant.

But this is the real world, where we have noise, plus offsets and other
worse nonlinearities (for a simple example try driving a double
integrator with a sine or cosine in the time domain -- you'll see what I
mean).  So we need a way to get the system to settle to it's normal
operating conditions, while still allowing us to take sufficient
measurements to find the open-loop response.

What that setup does is allow you to operate the system in closed-loop
(which is often the only way you _can_ operate a system to get a decent
measurement), yet still collect enough data to determine the open-loop
gain and phase.

Essentially you're exciting it with a sine wave (the input to the
rightmost summation block), and you're taking the ratio of the two
outputs (u_b and y).  The gain and phase shift from u_b to y is the ideal-
world open-loop response of the plant cascaded with the controller, even
if you could never get the system to operate in open-loop mode.

--
www.wescottdesign.com

Hi Tim,


Ok, thanks. I had the right idea in mind, then. I was just hung up on
nomenclature.

 > Looks like I should be reviewing that article for clarity.

No, I think the chapter is plenty enlightening.

By the way, I've just about got my act together to the point where I can
start taking response measurements of my quad copter in the see-saw test
jig.

Thanks again,

Rick

P.S. And thanks, Dave y for chiming in.

wrote:


I didn't wade through the article above, but there's various
configurations that can be used to measure an open loop frequency
response.  The old 'HP' has an application note on this.  I don't have
the title or link right at the moment, but you can search it out if
you try hard enough.

dave y.

On Tue, 17 Nov 2009 12:14:31 -0500, dave y. wrote:


I learned that method from the HP control systems analyzer that was
designed to use it (and reference the thing's manual, in fact) -- the
article would probably bear more than a passing resemblance to the
application note.

--
www.wescottdesign.com

wrote:


One thing I kinda remember is some measurement configurations are
easier to achieve than others, and it's temping to take the easy way
out, but the easy ones have a bias in the measurement.  I think it
came down to you had to break the loop to inject a signal vs. just
measuring the system as is.  Wish I could remember what that note was.

dave y.