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A PROJECT REPORT IS ON CLOSED LOOPSERVO HYDRAULIC ACTUATION SYSTEM

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The servo hydraulic actuation system drives the controlsurfaces to put the torpedo at its target.

The dynamic performance of the given system reveals an

average error of 4 % (approx). The error minimization and the system characteristicsare possible only with the characteristic knowledge of eachcomponent of the system.

The system contains different control units for thepurpose of output actuation these are all standard makeexcept rotary vane actuator

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This work deals with identifying the overall system response characteristics.

This involves the investigation of the characteristics of rotary actuator with

servo valve.

Internal leakage in the actuator is a concern which dictates its performance. Itnecessitates the study of the characteristics of the actuator to reveal the

relation between input pressure, output (angle) and importantly internal

leakage.

The temperature of t

he oil is a major factor w

hich

affects th

e response of th

eactuator.

The response-characteristics for the entire system are a transfer function for

the output angular displacement (angle) and the input command voltage.

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CONTROL SYSTEM :A controlsystemismeansbywhichanany quantityofinterestthatcanalteredormaintainedinadesiredmanner.

FLUID POWER: Fluidpowersystemsusepressurizedfluidssuchasair,water,

andhydraulicfluid(oilMIL 5606H)tocontrol,transmit,orgeneratepower.

ACT

UAT

OR

: Actuatorinafluidpowersystemisadeviceth

atconvertsth

efluidpowerenergytomechanicalenergyforthepurposeofdoingusefulwork.In

doublevane, oppositechambersintheactuatorareconnectedbypressure

equalizingpassagesintheupperandlowerheads.Inthismanner,theactuator

producesperfectlybalancedtorqueashydraulicforcesimultaneouslypushes

bothoftherotorvanesawayfromthestationaryshoes.Torqueoutputofthe

rotaryvaneactuatorremainsconstantthroughoutthefullrotationofthevalve.

Constanttorqueoutputisanespeciallyimportantfeatureinhighflowapplications.

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Servo Valve:

Thespoolisshiftedwitharotaryactuatormountedonthetopofthe

valveratherthanthesolenoidmountedattheendofthespoolinthreestage

valvethepilotstageshiftsthesecondstagewhichshiftsthethirdstage.Three

stagevalvesareusedfortheapplicationsofhighpressureandhighflowlarge

forcesarerequiredtoshiftsthethirdstagewhichdirectsthehighvolumeflow

totheactuator.

In this servo valve fluid flows across the fixed orifices and enters into

the centre manifold orifices are formed on each side between the flapper and

opposing nozzles.As long as the flapper is centered and the orifice is same on

both sides and the pressure drop to the return is same if the pressures are

equal in both sides then spool is in force balance depends on the flapper

movement.

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Meth l :

ver l l Response ch r cteristics of the closed loop system

Consider tions :

s given in the system, the act ation system is unique for the four control surfaces of

the torpedo. To analyze the entire system, it is preferable to do the analysis for one

control surface (one loop).

Theoretical PI Control is assumed for initial or

Block Diagram of the electro-hydraulic control system as shown in below fig.

Write the transfer functions foreach block for the above closed loop control system.

Derive the overall transfer function forcommand voltage and angle.

Transfer functions ofpiston pump, reliefand check valves to be identified.

Graphical representation of the theoretical and experimental results.

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Methodology

Writethetransferfunctionsforeachblockfortheclosedloopcontrol

system.

Derivetheoveralltransferfunctionforcommandvoltageandangle

(feedbackvoltage).

Comparisonofthetheoreticalandexperimentalresults.

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ROTARYACTUATOR:

Vanes

Chamberpartition

Redarrowed lines indicateoilenteringand leaving the

Chamberbetween thepartitionandthevane. Inlet

PressureP1

FlowQ1

Outlet

PressureP2

FlowQ2

Inlet PressureP3

FlowQ3

Outlet

PressureP4

FlowQ4

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Considerations:

Doublevanerotaryactuator

Inputisflowwithpressureoutputisangularmovement

Actuatorcontainsleakageduetovanemovement

TransferFunctionistotallydependsontherationbetweenangle & flow

Actuatorsupplypressureisconstant 210 bar

Inletpressuretotheactuator140 bar

Outputpressurefromtheactuator66.5 bar

Returnpressure is-3.5 bar

Rotaryvaneactuatorequationsdependsonvolumechangein

chambersandbulkmodulusandoutputanglechange

Actuatorexternalleakageiseliminated

Chambers-4 andineffectivestrokesareequal

Inactuationoppositechambersareequal.

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SERVO VALVE ANALYSIS:

The hydraulic actuator is controlled by aservo valve.If the tongue of the servo valve moves tothe right, the flows qand q3 increase,

whereas q2 and q4 decrease.

Hence p1 increases also, whereas p2decreases.The service pressure pS is much higherthan the standard atmospheric pressurep0.

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PROJECT PHASE : 1

ACTUATORMODELLING

Servovalve flowequations

ChambercontinuityequationScaling forlinearizationinactuator

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