1 © 2012 The MathWorks, Inc.

Plant Modeling and Performance

Analysis of Electro Mechanical

Actuation System for Fire Shut-off Valve

By H K Pavan Kumar Kollipara

2

Agenda

Objective

Challenges

Introduction

Problem Statement

Plant Modeling

Performance Analysis

Validation using Analytics

Conclusions & Recommendations

References

Appendix

3

Objective

To develop the plant model & study the performance of

the Electro-Mechanical Actuation System to operate

Fire Shut-off Valve

Critical performance parameters under study are:

– Operation time

Time taken by the valve to reach its desired position, since start of the

operation

– Close position error

Difference between the desired and the actual position after power shut-off

and the valve comes to rest

– Power supply demand

To understand the peak and steady-state requirements

4

Challenges

Operation time and the Close position error are two

contradictory requirements of the system

Meeting operation time and the close position error

simultaneously across wide range of operating

temperatures is a big challenge in designing this

system

Hence it becomes critical to study the dynamics of the

system at various operating temperatures

Due to absence of the controller the performance of this

system is majorly determined by its inertia

5

Introduction

Fire Shut-off Valve (FSOV) has to be installed between

hydraulic fluid reservoir and the hydraulic system of the

aircraft

In case of fire accidents in the aircraft, the valve should

stop the fluid supply to the hydraulic system

Eaton has come up with an Electro-Mechanical

Actuation System to operate this FSOV, which is as

shown in fig.1.

Fig.1 System Schematic

6

Analyze the dynamic behavior of the Eaton’s system to operate the FSOV

Verify the following requirements – Allowable error in Close position : ±1%

– Operation time: Max. 1.5 sec, at -6.6oC to 110oC and 18 Vdc

Max. 5 sec, at -55oC to -6.6oC and 28 Vdc

– Maximum duration the power supply requirements can exceed 30W is, 100ms

Provide recommendations to improve the design

Problem Statement

Non-linear dynamic equations are solved numerically

using MATLAB/SIMULINK

7

Plant Modeling

Assumptions in Plant modeling

– Neglected Gear Backlash effects

– Neglected damping inside the gearbox

– Temperature effects on Motor Mechanical damping coefficient

is not accounted for

– Temperature effects on mass MI of Rotor and the Gears are

neglected

– Shaft is assumed to be perfectly rigid

Plant model is developed based on the mentioned

assumptions

8

Plant Modeling

Motor Dynamics [1]

Gear Train Kinematics

System Dynamics [2]

Eq. (4) and (16) are solved simultaneously using

MATLAB/SIMULINK, to predict the system performance

System Dynamics

On normalizing (15) can be re-written as follows

Where,

9

Plant Modeling

Control Flow Diagram Input Parameters

Control flow diagram represents the way plant model is

developed in SIMULINK

Parameter Units

Jeqv Kg-m2

beqv N-m-sec

Tfeqv N-m

0eK Volts/RPM

0tK

Oz-in/Amp

0R Ohms

L Henry

B /deg.C

10

Performance Analysis

System responses are verified against the design requirements

Normalized Angular Displacement Power Supply Demand

@ -

55

oC

, 2

8V

@ -5

5oC

, 28

V

@ 2

5oC

, 1

8V

@ 2

5oC

, 18

V

max: 1.01

min: 0.99

max:1.01

min: 0.99

Y=1.05

Y=1.06

0.92 secs

0.56 secs

0.035 secs

11

Performance Analysis

Close Position error (%) Operation time (s)

Time duration for which the power supply

requirements exceeded 30W (ms)

Provided design recommendations based on simulation

predictions, to meet the performance requirements

Voltage

(V)

Temperature (deg. C)

-55 25 110

18 x 0.92 1.15

28 0.56 0.54 x

Voltage

(V)

Temperature (deg. C)

-55 25 110

18 x 0 0

28 35 0 x

Voltage

(V)

Temperature (deg. C)

-55 25 110

18 x 5.2 4.5

28 6.1 12.2 x

12

Validation using Analytics

Validated simulation predictions using analytics, as the

study is carried out prior to prototype development

Normalized Angular Acceleration Normalized Angular Velocity

Normalized Angular Displacement

Operating Temperature: 25oC

Supply Voltage: 28V

to

tf

13

Validation using Analytics

Considering initial time as the instant the power supply

is cut-off (t0=0.545s) and final instant as the moment

complete system came to rest (tf=0.69s)

Simulation results (acceleration & close position error)

are verified using following equations

Simulation Analytics

Y 27.5 27.5

Y 0.12 0.088

~25% variation in close position error is due to the fact that the

deceleration does not remain constant throughout, as assumed in

analytical calculations.

𝑌 𝑓2 − 𝑌 0

2 = 2𝑌0 𝑌

𝑌0 =1

𝐽𝑒𝑞𝑣𝜃𝑐𝑑(𝑇𝑀 − 𝑏𝑒𝑞𝑣𝑌0 𝜃𝑐𝑑 − 𝑇𝑓𝑒𝑞𝑣

)

14

Conclusions & Recommendations

Valve will switch from Open to Close position in desired operation of time, at all operating conditions

The valve is travelling beyond the desired close position due to Inertia effects of the gear train

Close position error is observed to be higher than the acceptable value, at all operating conditions

Motor armature resistance & the damping coefficients are very high and hence operating at very low efficiencies in the desired operating range

Selecting a motor with low armature resistance and increased damping in the system could help in meeting the CTQ’s in Operation time as well as the Close position error simultaneously

15

References

[1 ] R H. Welch Jr., G W. Younkin, “How Temperature Affects a

Servomotor's Electrical and Mechanical Time Constants,” Industry

Applications Conference, 37th IAS Annual Meeting, October 13-18,

2002.

[2] A.Tewari, “Translational Motion of Aerospace Vehicles,”

Atmospheric and Space Flight Dynamics, Birkhäuser Boston,

2007, ch.4, sec.4.4, pp.86.

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Appendix

Nomenclature

𝜃𝑐𝑑 − 𝑑𝑒𝑠𝑖𝑟𝑒𝑑 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡ℎ𝑒 𝑣𝑎𝑙𝑣𝑒