This document discusses computer modeling and simulation tools used in modern engineering design. It provides examples of how simulation was used to diagnose problems and improve the design of train control systems. Key points include: - Computer modeling allows testing of complex systems without building physical prototypes, reducing costs and shortening development time. - Matlab/Simulink was used to model train control systems to investigate stability issues and propose solutions before implementation. - Time and frequency domain simulations helped diagnose resonance problems and improve grounding schemes.

1. Computer Modelling/Simulation in Modern Design
and Engineering
Dr.Jian Shen
Date: August 17, 2006
Location: Video Conference Room, LCS

2. 2
Contents
Computer modeling and simulation
tools
 Train performance simulation (overall operations simulation)
 Frequency domain simulation (filter design, power
electronics thermal design input etc)
 Time domain simulation tools (dynamic performance
simulations)
Matlab/Simulink model of Innovia
control system

3. 3
Advantages of computer modeling and
simulation
 It helps to design and test a complex
system in its full dynamic range before
building it;
 It helps to diagnose problems and find
solutions;
 It helps to reduce costs and shorten period
of product development or trouble shoot;
 Computer modeling and simulation have
become a standard method of any modern
industry design

4. 4
Requirements for a good computer modeling
of the real systems
 Good understanding of each of the parts of
the physical system, its operation
mechanism;
 Correct mathematics modeling of the
system and the control sequence;
 It helps understanding of the system
dynamics –so a good model of the system
can be a teaching tool for junior engineers.

5. 5
Simulation tools in a electric drive system design---application
examples
 Train performance simulations ---TPS (TPSAIM, TOM etc);
 Frequency domain simulations--- FDM inverter etc;
 Time domain simulations--- SABER, Simplorer, PSPICE,
Matlab/Simulink etc

6. 6
Why so many different simulation models?—for
different applications
 Train Performance Simulation
(TPS) for overall system
evaluation and sizing the main
system components (tender
design, quick turn around);
0 500 1000 1500 2000 2500 3000 3500
0
20
40
60
80
100
speed(mph)
time (Sec)
0 500 1000 1500 2000 2500 3000 3500
0
50
100
150
200
250
300
BART Daly city to East Dublin Run Aw2 J.S. 8-22-01
Iphase(rms_amps)
0 20 40 60 80 100 120
0
10
20
30
40
50
60
Pittsburgh LRV Level tangent run @AW2 weight at low line voltage 525V
Speed(mph)
time (s)
0 20 40 60 80 100 120
-800
-600
-400
-200
0
200
400
600
800
Pittsburgh LRV Level tangent run @AW2 weight at low line voltage 525V
Motortorque(ft-lbs)
time(s)
One Acc./Dec. cycle
One trip

7. 7

8. 8

9. 9
BART TM rotor failure mechanism diagnose---photo
curtsey of Mr. Peter Pritchard

10. 10
Time domain simulation tools
 SABER
 PSIPCE
 Simplorer
 Simulink
 Real Time Simulations, hardware in
the loop (HIL) and software in the loop
(SIL) etc.

11. 11
SABER model examples
 Saber model of a 4-QS power
and control system (50Hz VS. 60Hz)
SFAA ground loss detection (report #1600) avoided
expensive development, used in all the APM projects
since including both Innovia and CX100 types.

12. 12
This simulation saved the company 60Hz combined power tests

13. 13
PSPICE and Simplorer MARTA vehicle grounding scheme and
TM motor bearing failure diagnose

14. 14
MARTA Traction motor bearing failure—solution separate the
traction return and safety ground brushes.

15. 15
SPICE model of the grounding circuit of MARTA---current
carrying brush disturbance caused voltage spikes (the model)
R_r_cable1
5E-4
Lcable9
0.35uH
Lcable3_2
2uH
con2
7.4E-5
R_cable9
R_r_cable1_2
5E-4
R_contact
0.1
Lcable1
7uH Lcable1_2
7uH
Rcable2_2
1.32E-4
U2
0.01s
1 2
Lcable4_2
2uH
con1
R_coupler1
3.05E-4
1.54E-4
R_bearing1
1E6
316E-6
R_B_gb1
R_Btruck_bolster
50E-6
7.4E-5
R_cable8_2
L3rdrail_2
2uH
7.4E-5
R_cable8
0.1E-3
R78
Rcable4
1.54E-3
0
R_bearing3
1E6
Lcable6_2
0.5uHRcable5_2
1.404E-4
R_bearing4
1E6
316E-6
R_B_gb4
Rcable3_2
1.32E-4Lcable5
2uH
1.54E-4
R_cable10_2
L3rdrail_1
10uH
R2
0.2E-3
L_track1
5uH
R_track_carbody
120E-6
R_contact2
0.1
316E-6
R_b_gb3
Lcable8_2
0.35uH
2uH
Rcable5
1.404E-4
R_carbody_half
130E-6
Rcable2
1.32E-4
V
Lcable7_2
0.5uH
R_track_Btruck
25E-6
Lcable10_2
2uH
2uH
L_track_carbody
4uH
V1
750V
Lcable8
0.35uH
I2
250A
R_bearing2
1E6
Lcable3
2uH
R_Ftruck_bolster
50E-6
Lcable10
2uH
con12
R_bus_plate
1E-6
283E-6
R_track
Lcable2_2
2uH
Lcable9_2
0.35uH
Ltruck_track2
2uH
MARTA Metro M_frame2 Carbody mod Ground
Lcable4
2uH
1.76E-4
R_cable6_2
Rcable3
1.32E-4
Lcable5_2
2uH
I1
250A
Lcable6
0.5uH
V
1.76E-4
R_cable7
1.76E-4
R_cable6
316E-6
R_b_gb2
Lcable7
0.5uH
7.4E-5
R_cable9_2
R_Btruck_frame
50E-6
576E-6
R_3rd_rail
Ltruck_track1
2uH
Lcable2
2uH
Rcable4_2
1.54E-3
<Doc> <RevCode>A
1 1Thursday,June05,2003
Title
Size DocumentNumber Rev
Date: Sheet of
R_Ftruck_frame
50E-6
1.76E-4
R_cable7_2
R_track_Ftruck
25E-6

16. 16
SPICE model of the grounding circuit of MARTA---
current carrying brush disturbance caused voltage spikes

17. 17
Real time HIL simulation dSPACE or hardware---
powerful tool for control hardware and embedded software debugging
SMSC line 7/8 inverter drive stability problem due to a
Small rotor parameter change from line 4
•SMSC line 4 inverter drive stability no problem
but the TM slightly overheating

18. 18
A more detailed introduction of Matlab/Simulink simulation
 Probably the most widely used
platform;
 Both TDM and FDM
calculations;
 Industry standard, ease of
exchange models;
 Ease of implementing both HIL
and SIL simulations;
 Modeling languages using
powerful s-functions;
 Unlike circuit simulators need
to write your own equations;
 Interface with many other
platforms as well as real
hardware instruments

19. 19
ATC
DFW ATC speed control loop stability
TCC
Prop/FR
BRK(650ms)
32ms 150-270ms 20-30ms
Rate_req*
TE/BE*
speed

20. 20
Main issue
 A low frequency (3-5Hz) oscillation in all the speed
range affecting ride quality and components life
cycle
- ATC speed regulation cycle --- rate command every 32ms.
- TCC transports & converts the command to propulsion &
friction braking in 150-270ms (random delay ).
- Propulsion to achieve the required tractive & braking effort in
20-30ms when received the command from TCC.
- A measurement showed the mechanical structure has a
natural frequency of around 4Hz.
- The above electrical delay added up to 3.3---5Hz.
- Any mechanical disturbance is coupled through the speed
sensor into the electrical system and causing the resonance.

21. 21
A low frequency oscillation 3-5Hz in all the speed range (from
the Barn), ATC mode without filter

22. 22
No low frequency oscillation 3-5Hz in all the speed range (from
the Barn), manual mode

23. 23
Possible solutions proposed
 Add a P-signal generator (about $800,000 budgeted).
- May not work, not knowing now what delays the system can tolerate. May need another
kind of device depending on stability needs.
- Ref: B.Paluf, P-Signal Decision Mitigation Plan, B70” 10-11-2001
- Extra cost of hardware.
 Model the vehicle with combined ATC--TCC--Propulsion/friction brake, to
understand the dynamics of the system and find solutions through a
systematic investigation (president Ray Betler set up a special budget for the
modeling work).
- Considered necessary for the total system adjustment not partial adjustment which
may cause new problems.
- All the subsystems are proven design and none thought their problem. Without
modeling, any change to the system (motor, inverter, TCC etc) is unknown how it will
impact system operation.
- It is related to if the Innovia control system design is valid ---impact on this
and future projects.

24. 24
Approach to tackle the issue
 Understand the three main parts of the system.
 Model the system in Matlab/Simulink (no Simulink model for
each of the components, yet)
 Validate the model by comparing the test results from the
prototype train.
 Try to find a stable solution and optimize on the model.
 Implement the solution.

25. 25
MATLAB/Simulink model of Innovia control system---a software
in the loop approach (SIL)
rate_req
V_ATO
Innovia ATO-TCC-Propulsion System Simulation Model
Click Here
To Load
Parameters
TCC
Train Commu. & Control
Reference
Reference1
P&C
Propulsion System
ClickHere
for Overview
VATO_CTM
A_speed
BE_fric
A_acc
Dist_ft
prop/brk
speed_mph
TE(lbs)
TE_dilved

26. 26
Modeling of the ATO controller (software in the loop
“SIL” approach VATO_CTM block)
The ATO model (implementing the actual C code “control train
motion” in a Matlab S-function)
2
prop/brkstate
1
rate_request(mphps)
ref_vel
com_speed
rate_req
Pro_brk_state
dis_2_station
tar_acc
sta_tar_speed
com_acc
vato_ctm
S-Function
Mux
Mux
Demux
Demux
3
Distance(feet)
2
actual_acc(mphps)
1
actual_speed(mph)

27. 27
Modeling of the TCC controller (below the TCC block)
TCC is modeled in behavioral level
Train Communication and Control Simulation Model
2
BE_fric
1
TE_prop
rate_gwex rate_wtb
wtb_dly
rate_comc rate_v cu1
vcu1_dly
rate_req2
rate_wtb rate_gwin
gwin_dly
rate_v cu1 rate_gwex
gwex_dly
rate_atc rate_comc
comc_dly
rate_gwin
TE_dilv ed
mph
pwr_brk_req
TE_prop
BE_f ric
VCU-dly2
2.236936292e-4
Gain
4
pwr_brk_req
3
mph
2
TE-dilved
1
rate_ATC

28. 28
Modeling of the propulsion control (below the P&C
block)
Propulsion control is also modeled in behavioral level with
necessary details
Propulsion Simulation Model
<Xus2>
<Xomega_m>
2
TE_dilved
1
mph
WAVE_G
wave
VSI
pwm2
torq_nm
omega_m
mph
TE_dilv ed(lbs)
Train Model
ws
is3
torq
Reference
Reference1
Controller
Orion_mod
Observer
Orion
Obs
Measure
Ts varying.
Measurement
Board4
Traction
Motor
Gamma-Model
Ud
DC-link
2
BE_fric
1
TE_require
<Xpsis_k+1>
<Xpsis_k+1>
<Xpsis2>
<Xpsis2>
<F>
<F>
<delta_ref >
<delta_ref >
<pwm6>
<is3>
<is3>
<is3>
<Xis_k+1>
<Xis_k+1>
<>
<f lux_ref >
<psis2>
<Xis2>
<us3>
<us3>
<ctrl_f act2>
<torque>
<Xtorque>
<Xtorque>
<psir2>
<Xpsir2>
omega_us

29. 29
Reproduce the low frequency oscillation problem on the
simulation model
0 5 10 15 20 25 30 35 40 45 50
0
5
10
15
20
25
30
vehiclespeed(blue)
speedsensorsignal
(red)
02-05-2002S.J.
time(s)
(mph)
15 16 17 18 19 20 21 22 23 24 25
26.5
27
27.5
28
28.5
vehiclespeed(blue)
speedsensorsignal
(red) 02-05-2002S.J.
time(s)
(mph)

30. 30
The proposed solution- A digital notch filter ‘s characteristics
1 2 3 4 5 6 7 8 9 10
-35
-30
-25
-20
-15
-10
-5
0
frequency (Hz), (fs=32Hz)
gaininDB 4th order butterworth digitized bandstop filter (SBW 2-6Hz) frequency characteristics

31. 31
Results comparison---implemented in DFW and Heathrow
projects

32. 32
R142A project one year after in revenue service, 3 trains being
trapped under river due to a “bucking” E/M resonance problem

33. 33
Measured results---Low frequency oscillations (6.5-7Hz) in speed signal
rpm1, torque dsp T, and speed signal dsp Wls,
People say it is a mechanical problem
Due to inverter shut down & still oscillations

34. 34
The Inverter and vector control simulation model --- Using a
simplified model from DFW (no ATC and TCC)
Propulsion Simulation Model
WAVE_G
wave
ud
time
VSI
pwm2
ClickHere
To Load
Parameters
Id
Un
Ud
In
dc-link1
torq_nmomega_m
Train Mdeol
Xtorq
torq
psir2
psis2
is3
Scope7
Scope6
Scope5
Reference
Reference1
Controller
Orion_mod
Observer
Orion
Orion1
Measure
Ts varying.
Measurement
Board4
Traction
Motor
Gamma-Model
Ud
DC-link
Clock
<Xpsir2>
<Xpsir2>
<Xpsis_p2>
<Xpsis_p2>
<Xpsis2>
<Xpsis2>
Ud
Ud
<Xomega_m><Xomega_m>
<Xomega_m>
<F>
<F>
<delta_ref>
<delta_ref>
<pwm6>
omega_us
<Xtorque>
<Xtorque>
<is3>
<is3>
<is3>
<psir2>
<Xis_p2>
<Xis_p2>
<torque>
<torque_ref>
<flux_ref>
<psis2>
<Xis2>
<Xis2>
<Xus2>
<Xus2>
<us3>
<us3>
<ctrl_fact2>

35. 35
Problem run with 6.5Hz oscillations injected in the speed signal
resulted in torque oscillation and motor phase current oscillations and
inverter shutdown---1
0 0.5 1 1.5 2 2.5 3 3.5 4
-2
0
2
4
6
8
Speed, current and torq with30%mechinject.speed(mph)
0 0.5 1 1.5 2 2.5 3 3.5 4
-500
0
500
1000
1500
phaseamp&torq
J.S. 9-13-2002
time (s)

36. 36
Problem run with 6.5Hz oscillations injected in the speed signal
resulted in torque oscillation and motor phase current oscillations and
inverter shutdown---2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
-500
-400
-300
-200
-100
0
100
200
300
400
500
Tractionmotor 3- phasecurrent with6.5Hz oscillation

37. 37
A proposed solution to stop the bucking—implemented in the
whole R142A fleet of more than 600 cars

38. 38
Test report

39. 39
Tests Carried Out In NYCT Test Track

40. 40
The Second Thought
 Why a cost/effective solution to a difficult problem considered a
“Patch”?
 Why some of our people so sure that it is a mechanical problem only
(similar situation in Las Vegas Monorail)?
 Why this is considered by some as not a “correct” solution but liked
by the project team and the customers (KRC & NYCT)?
 Why a totally unrelated DC link stability control is considered the
correct solution even measured data and tests prove to be not the
case? Do we have the same situation in other projects, i.e. when we
have a pain at the foot but the prescription is for curing the headache?
 Answer, EAT more --- Education and Training.

41. 41
“Fly by wire example”
http://www.centennialofflight.gov/essay/Dictionary/fly-by-wire/DI83G1.htm

42. 42
Digital Fly By Wire (http://www.disenchanted.com/dis/technology/fly-by-wire.html)
 The other reason for DFBW was to correct for
something called Pilot Induced Oscillations (PIO),
which is where the pilot over-controls the aircraft
and a sustained oscillation results. What's
interesting is that it also revealed the other hidden
advantage of DFBW: PIO wasn't accounted for on
the first flight of NASA 802, but began to show-up
on test flights of the Space Shuttle. In response,
the computer programmers wrote a filter for it and
tested it out on the F-8, making it probably the first
piece of hardware to ever be enhanced by a
software upgrade.

43. 43

44. 44
Conclusion:
 Computer modeling and simulation is an effective way of diagnose
for existing systems.
 Solutions can be found and optimized on the model once it is
established without expensive Lab time and on site tests.
 The better way is to prevent the kind of problems by systematic
modeling in the design stage but often due to budget or time
constrains it is not done.
 In projects where it is done and problems being prevented, it is not
always appreciated. Management need to understand this and
allocate the resource to carry out the task where ever and when ever
possible.
 A detailed engineering report has been written (#1815)

45. 45
Questions ?