1. Evaluation in Engineering Design Process Modeling and FSM
Yinong Chen
11/10/2018

2. The Engineering Design Process
Define
Problem and requirement
Research
Define
Alternative solutions
Modeling
Analysis
Simulation
Prototyping
Final Selection
Implementation
and testing

3. Roadmap: Modeling and FSM1
Engineering Models
Finite State Machine (FSM) Mode 2 3
FSM Application: Vending Machine 4
Different Maze Navigation Algorithms in FSM
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4. Mathematical Models for Engineering
Mathematical Models: Based on logical and quantitative relationships among model components.
Deterministic Models: Predictable behavior, always give the same answer each time we run the model.
Graph Model
Truth table for ALU design
Finite State Machine for circuit design and software design
Stochastic Models: Element of chance built into model different unpredictable answer each time we run the model
Coin flipping experiment
Monte Carlo Model
Reliability model of computer hardware and software
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5. Deterministic Model: Finite State Machine (FSM)
A truth table specifies the input – output relations of a system, but it does not have states (memory);
Many systems need to have states, so that they can complete the computation in a number of steps.
A FSM has a finite number of states and transitions between those states:
Transitions occur because of inputs
Output can be given in any state

6. Model For a Stateless Vending Machine
For a given input, it gives an output immediately
Parameters: coins and products
Range of values for each parameter:
Coins: 1, 5, 10, 25
Products : sicker, candy, pencil, and marker
Constraints/Relationships/Solution:
Coins
Penny (1)
Nickel (5)
Dime (10)
Quarter
Products
Sicker
candy
pencil
marker
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7. A Stateless Vending Machine
VPL Implementation: No variable is used
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8. Why does a coin-operated washing machine take all coins at the same time?
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9. A four-way intersection has red/green traffic lights that are
controlled with timers.
Traffic can only move in one direction at a time: NS or EW. W E S

10. A four-way intersection has red/green traffic lights that are
controlled with timers.
Traffic can only move in one direction at a time: NS or EW. W E S
traffic light
controller
block diagram

11. A four-way intersection has
red/green traffic lights that are controlled with timers.
Traffic can only move in one direction at a time: NS or EW. W E S
timer expired
EW green
NS red
EW red
NS green
We can show this graphically with a state diagram.
timer expired

12. timer expired or emergency signal
A Finite-State Machine (FSM)
is a model of the discrete dynamics of a system
that has a finite number of discrete states.
Transitions between states are caused by
events, such as:
- the expiration of a timer
- a change in a sensor
state diagram
EW green
NS red
EW red
NS green
timer expired or emergency signal
state table
current state
event
next state
EW grn/NS rd
timer exp
EW rd/NS grn

13. The Traffic Lights by Canary Wharf Tower, East London
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14. Finite-State Machines are often used to design
control systems...
When button pressed:
If state==open
then close
Else open
Open
Close

15. Finite-State Machines are often used to design
control systems...
A garage door opening system
If the door is closed and I press the button (touch sensor), the door begins to move up.
When it reaches the top, the door
activates a limit switch (touch sensor) and stops.
If the door is open and I press the
button, the door begins to move down.
When it reaches the bottom, the door
activates another limit switch and stops.

16. Finite-State Machines are often used to design control systems...
A garage door opening system
block diagram
button
garage door
controller
motor
door
limit
switch
...we want to design the controller...

17. Finite-State Machines are often used to design control systems...
A garage door opening system
states
- door closed
- door open
- door closing
- door opening
events
- button press
- limit switch touched (closing finished or opening finished)

18. Finite-State Machines are often used to design
control systems...
button pressed
door
closed
door
opening
stopped
button pressed
limit
tripped
limit
tripped
door
closing
door
open
button pressed

19. Finite-State Machines are often used to design
control systems...
button
pressed
button pressed
door
closed
door
opening
opening
stopped
button
pressed
limit
tripped
limit
tripped
button
pressed
closing
stopped
door
closing
door
open
button
pressed
button pressed

20. Example: FSM Vending Machine
Takes quarters and dollars only
Maximum deposit is $1 (or four quarters)
Sodas cost $0.75
Possible Inputs (Events):
Deposit quarter (25)
Deposit dollar (100)
Push button to get soda (soda)
Push button to get money returned (ret)
States: 0, 25, 50, 75, 100, and state transits on input

21. Example 3: FSM Vending Machine
soda 25 50
quarter
quarter
quarter
return 75
Start
quarter
dolllar
100
Deposit quarter
Deposit dollar
Push button to get soda (soda)
Push button to return money (ret)

22. FSM With Additional Memory (Variable)
If (Sum>75)
Sum = Sum – 75
release soda
If Sum < 75, do nothing
quarter
dollar
soda
> 0
dollar
quarter
If (Sum== 75)
release soda
Sum = Sum + 25
Sum = Sum + 100
return
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23. Example: FSM Vending Machine
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24. The Project... An autonomous mobile robot
must navigate through a maze.
An on-line navigation problem:
solving a maze from the inside.
An on-line algorithm receives its input gradually rather than all at once.
It must make decisions based on this partial input.

25. DistanceMeasured < 400
FSM of Robot in a Maze
DistanceMeasured < 400
rightFinished
Start
Forward
Turning Right
Turned Right
RightDistance 
DistanceMeasured
DistanceMeasured
>= rightDistance
Turning Left
resum180Finished
leftFinished
Resume 180
Turned Left
DistanceMeasured
< rightDistance
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26. Greedy Algorithm based on the First Working Solution
DistanceMeasured < 400
Turning
Left
Turned
leftFinished
Spin
180
DistanceMeasured < 800
DistanceMeasured >= 800
Spin180
Finished
Start
Forward
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27. Right-Wall-Following Algorithm
Variable BaseDistance = Ultrasonic sensor measure;
The robot repeats all the following steps in a loop, until the touch sensor is pressed;
Robot moves forward;
Robot keeps measures the right side-distance in certain interval, and it compares the newly measured distance with the distance stored in variable BaseDistance .
If the distance measured is less than BaseDistance - 5, the robot turns one degree left, and then returns to step 2;
If the distance measured is greater than BaseDistance + 5, turns one degree right, and then returns to step 2;
If the distance measured greater than BaseDistance + 200, turns 90 degree right, and then returns to step 2;
Touch sensor is pressed; robot moves backward 0.5 rotations, and then turns left 90 degree;
Return to step 2.

28. Right-Wall-Following Algorithm
Forward a bit then turn
Turning Right90
DistanceMeasured > BaseDistance + 400
Turned Right
rightFinished
Turning Left90
Turned Left
leftFinished
Touch-Sensor Touched
Backward then turn
Left 1 degree
Right 1 degree
Forward
DistanceMeasured < BaseDistance - 5
DistanceMeasured
> BaseDistance + 5
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Start

29. Wall-Following Diagram in VPL
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30. FSM for Hard-Coded Turns using Touch Sensor
Backward before turning
Left
Finished
Left
Finished
Touched
Touched
FW 1
Turning Left90
Turned Left 1
FW 2
Turning Left90
Turned Left 2
Turned Right 2
Turning Right 90
FW 4
Turned Right 1
Turning Right 90
FW 3
Right
Finished
Touched
Right
Finished
Touched
FW 5
Backward before turning
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31. FSM to model robot navigation (the ‘right-then-left’ algo)
do something !
Forward
dist < 400mm
Turning
Right 90
timer exp
Turned
Right
measure
distance
dist_left >= dist_right
Turning
Left
180 or
timer exp
timer exp
Turning
right
180
measure
distance
Turned
Left
dist_left < dist_right

32. Implementation of the ‘right-then-left’ FSM