Computer Modelling/Simulation in Modern Design and Engineering

Dr.Jian ShenDate: August 17, 2006

Location: Video Conference Room, LCS

2

ContentsComputer 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

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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

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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.

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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

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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 35000

20

40

60

80

100

spee

d (m

ph)

time (Sec)

0 500 1000 1500 2000 2500 3000 35000

50

100

150

200

250

300

BART Daly city to East Dublin Run Aw2 J.S. 8-22-01

Ipha

se(r

ms_

amps

)

0 20 40 60 80 100 1200

10

20

30

40

50

60

Pittsburgh LRV Level tangent run @AW2 weight at low line voltage 525V

Spe

ed (m

ph)

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

Mot

or to

rque

(ft-

lbs)

time(s)

One Acc./Dec. cycle

One trip

7

8

9

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

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Time domain simulation tools

SABER PSIPCE Simplorer Simulink Real Time Simulations, hardware in

the loop (HIL) and software in the loop (SIL) etc.

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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.

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This simulation saved the company 60Hz combined power tests

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

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

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SPICE model of the grounding circuit of MARTA---current carrying brush disturbance caused voltage spikes (the model)

R_r_cable1

5E-4

Lcable90.35uH

Lcable3_2

2uH

con2

7.4E-5R_cable9

R_r_cable1_2

5E-4

R_contact0.1

Lcable1

7uH Lcable1_27uH

Rcable2_2

1.32E-4

U2

0.01s1 2

Lcable4_2

2uH

con1

R_coupler13.05E-4

1.54E-4

R_bearing11E6

316E-6

R_B_gb1

R_Btruck_bolster50E-6

7.4E-5R_cable8_2

L3rdrail_2

2uH

7.4E-5R_cable8

0.1E-3R78

Rcable4

1.54E-3

0

R_bearing31E6

Lcable6_2

0.5uHRcable5_21.404E-4

R_bearing41E6

316E-6

R_B_gb4

Rcable3_2

1.32E-4Lcable5

2uH

1.54E-4R_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

Rcable51.404E-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_carbody4uH

V1

750V

Lcable8

0.35uH

I2

250A

R_bearing21E6

Lcable3

2uH

R_Ftruck_bolster

50E-6Lcable10

2uH

con12

R_bus_plate

1E-6

283E-6R_track

Lcable2_2

2uH

Lcable9_20.35uH

Ltruck_track2

2uH

MARTA Metro M_frame2 Carbody mod Ground

Lcable4

2uH

1.76E-4R_cable6_2

Rcable3

1.32E-4Lcable5_2

2uH

I1

250A

Lcable6

0.5uH

V

1.76E-4R_cable7

1.76E-4R_cable6

316E-6

R_b_gb2

Lcable7

0.5uH

7.4E-5R_cable9_2

R_Btruck_frame

50E-6

576E-6R_3rd_rail

Ltruck_track1

2uH

Lcable2

2uH

Rcable4_21.54E-3

<Doc> <RevCode>A

1 1Thursday, June 05, 2003

Title

Size Document Number Rev

Date: Sheet of

R_Ftruck_frame

50E-6

1.76E-4R_cable7_2

R_track_Ftruck

25E-6

16

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

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Real time HIL simulation dSPACE or hardware---powerful tool for control hardware and embedded software debuggingSMSC 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

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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

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ATC

DFW ATC speed control loop stability

TCCProp/FR

BRK(650ms)

32ms 150-270ms 20-30ms

Rate_req*TE/BE*

speed

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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.

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

22

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

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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.

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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.

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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

Click Herefor Overview

VATO_CTM

A_speed

BE_f ric

A_acc

Dist_f tprop/brk

speed_mphTE(lbs)

TE_dilv ed

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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)

2prop/brk state

1rate_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

3Distance(feet)

2actual_acc(mphps)

1actual_speed(mph)

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Modeling of the TCC controller (below the TCC block)

TCC is modeled in behavioral level

Train Communication and Control Simulation Model

2BE_fric

1TE_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

4pwr_brk_req

3mph

2TE-dilved

1rate_ATC

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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>

2TE_dilved

1mph

WAVE_G

wave

VSI

pwm2

torq_nm

omega_m

mph

TE_dilv ed(lbs)

Train Model

ws

is3

torq

Reference

Reference1

Controller

Orion_mod

ObserverOrion

Obs

MeasureTs varying.

Measurement Board4

TractionMotor

Gamma-Model

Ud

DC-link

2

BE_fric

1TE_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

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Reproduce the low frequency oscillation problem on the simulation model

0 5 10 15 20 25 30 35 40 45 500

5

10

15

20

25

30

vehicle speed (blue)

speed sensor signal (red)

02-05-2002 S.J.

time (s)

(mph)

15 16 17 18 19 20 21 22 23 24 25

26.5

27

27.5

28

28.5

vehicle speed (blue)

speed sensor signal (red) 02-05-2002 S.J.

time (s)

(mph)

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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)

gain

in D

B4th order butterworth digitized bandstop filter (SBW 2-6Hz) frequency characteristics

31

Results comparison---implemented in DFW and Heathrow projects

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

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

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

Click Here To Load

Parameters

Id

Un

Ud

In

dc-link 1

torq_nmomega_m

Train Mdeol

Xtorq

torq

psir2

psis2

is3

Scope7

Scope6

Scope5

Reference

Reference1

Controller

Orion_mod

ObserverOrion

Orion1

MeasureTs varying.

Measurement Board4

TractionMotor

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

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

8Speed, current and torq with 30% mech inject.

spee

d(m

ph)

0 0.5 1 1.5 2 2.5 3 3.5 4-500

0

500

1000

1500

phas

e am

p &

torq

J.S. 9-13-2002

time (s)

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

500Traction motor 3- phase current with 6.5Hz oscillation

37

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

38

Test report

39

Tests Carried Out In NYCT Test Track

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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

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

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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.

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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)

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Questions ?