### Is it P controller or PI controller?

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Dear all, could anyone tell me the following fomula is P controller or PI controller?

u(k)=u(k-1)+k*( e(k)- e(k-1) )

Thanks in advance.

-- changxl (changxl@ust.hk), September 14, 2003

### Answers

It is PD controller.

-- Ranjan Kumar (ranjanee@iitk.ac.in), October 30, 2003.

it is a PI controller

-- satendra (skd@ee.iitb.ac.in), November 24, 2003.

You are both wrong. It is a P controller. Proof: A simple proportional controller is: u(n)=Kp*e(n) Also u(n-1)=Kp*e(n-1)

Subtract the second equation from the first u(n)-u(n-1)=Kp*e(n)-Kp*e(n-1) Add u(n-1) two both sides u(n)=u(n-1)+Kp*e(n)-Kp*e(n-1) u(n)=u(n-1)+Kp*(e(n)-e(n-1)) This is the equation in question.

A PI controller: u(n)=u(n-1)+(Kp+Ki*T)*e(n)-Kp*e(n-1)

A PD controler: u(n)=u(n-1)+(Kp+Kd/T)*e(n)+(-Kp-2*kd/T)*e(n-1)+Kd/T*e(n-2)

-- Peter Nachtwey (peter@deltacompsys.com), November 26, 2003.

please send information about pi controller design. thank you.

-- ishtiaqnaveed.r (ishtiaqnaveednie2003@yahoo.com), June 06, 2004.

definitely it is PI controller, reason is simple as it is taking into account two values one current and one previous to current. Above explanation itself discards the possibily of P Controller

-- satendra dagar (skdagur@yahoo.com), March 07, 2005.

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