Floating mode controller. theory of controllers.

1. FLOATING MODE
CONTROLLER
GAURAVSINH PARMAR
(170410117023)
AADARSH PATEL
(170410117025)

2. FLOATING CONTROL MODE
• IN FLOATING CONTROL, THE SPECIFIC OUTPUT OF THE CONTROLLER IS NOT
UNIQUELY DETERMINED BY ERROR.
• IF THE ERROR IS ZERO, THE OUTPUT DOES NOT CHANGE BUT REMAINS (FLOAT) AT
WHATEVER SETTING IT WAS WHEN ERROR WENT TO ZERO. WHEN ERROR MOVES OF
ZERO, THE CONTROLLER OUTPUT AGAIN BEGINS TO CHANGE.
• SIMILAR TO TWO-POSITION MODE, THERE WILL BE A NEUTRAL ZONE AROUND ZERO
ERROR WHERE NO CHANGE IN CONTROLLER OUTPUT OCCURS.
• POPULARLY THERE ARE TWO TYPES:
1.) SINGLE SPEED
2.) MULTIPLE SPEED

3. FLOATING CONTROL MODE
SINGLE SPEED:
• IN THIS MODE, THE OUTPUT OF THE CONTROL ELEMENT CHANGES AT A FIXED RATE
WHEN THE ERROR EXCEEDS THE NEUTRAL ZONE. THE EQUATION FOR SINGLE SPEED
FLOATING MODE IS:
• WHERE,
DP/DT= RATE OF CHANGE OF CONTROLLER OUTPUT WITH TIME.
KF = RATE CONSTANT(%/S)
EP=HALF THE NATURAL ZONE.

4. FLOATING CONTROL MODE
• IF THE ABOVE EQUATION IS INTEGRATED FOR THE ACTUAL
CONTROLLER OUTPUT, WE GET
WHERE P(0)= CONTROLLER OUTPUT AT T=0
• THE EQUATION SHOWS THAT THE PRESENT OUTPUT DEPENDS ON
THE TIME HISTORY OF ERROR THAT HAVE PREVIOUSLY
OCCURRED.
• BECAUSE SUCH A HISTORY IS USUALLY NOT KNOWN, THE
ACTUAL VALVE OF P FLOATS AT AN UNDETERMINED VALUE.

5. FLOATING CONTROL MODE
• IF THE DEVIATION PERSISTS, THEN EQUATION SHOWS THAT THE CONTROLLER
SATURATES AT 100% OR 0% AND REMAINS THERE UNTIL AN ERROR DRIVES IT
TOWARD THE OPPOSITE EXTREME. A GRAPH OF SINGLE SPEED FLOATING
CONTROL IS SHOWN IN FIG.

6. FLOATING CONTROL MODE
• SINGLE SPEED FLOATING CONTROLLER AS SHOWN IN FIG.1
• A.) SINGLE SPEED CONTROLLER ACTION AS THE OUTPUT RATE OF CHANGE TO INPUT
ERROR, AND
• B.) EXAMPLE OF ERROR AND CONTROLLER RESPONSE.

7. FLOATING CONTROL MODE
• SUPPOSE A PROCESS ERROR LIES WITHIN THE NEUTRAL ZONE WITH P=25%. AT T=0, THE
ERROR FALLS BELOW THE NEUTRAL ZONE. IF K=+2% PER SECOND, FIND THE TIME WHEN THE
OUTPUTS SATURATES.
SOLUTION:
• THE RELATION BETWEEN CONTROLLER OUTPUT AND TIME IS
P= KFT=P(0)
• WHEN, P=100%,
100%= (2%/S)(T)+25%
YIELDS, T=37.5SEC.

8. FLOATING CONTROL MODE
MULTIPLE SPEED:
• IN THIS MODE SEVERAL POSSIBLE SPEEDS CONTROLLER OUTPUT.
• USUALLY, THE RATE INCREASE AS THE DEVIATION EXCEED CERTAIN LIMITS.
• FOR SPEED CHANGE POINT EPI ERROR THERE WILL BE CORRESPONDING OUTPUT
RATE CHANGE KI, THE EXPRESSION CAN BE GIVEN BY:
• IF THE ERROR EXCEEDS EPI, THEN THE SPEED IS KFI, IF THE ERROR RISES TO
EXCEED EP2, THE SPEED IS INCREASED TO KF2, AND SO ON. THE GRAPH OF
MULTIPLE SPEED MODE IS SHOWN IN FIG.2