Design of the Life-ring Drone Delivery
System for Rip Current Rescue
Solution
Tether
Hold/Release
System
Life-ring/Ring-buoy
Andrew Hardy, Mohammed Rajeh,
Lahari Venuthurupalli, Gang Xiang
Dji.com, (Schenkel, 2014), Parks.ca.gov, 2015, NOAA
Victim
survival
time limit
Time (s)
Lifeguard
Reach
Time
60 93
1. Context
2.
3.
4.
5.
6.
7.
8.
9.
Stakeholders
Problem/Need Statements
Requirements
Con-Ops
Alternatives
Method of Analysis
Future Work
Thanks
Beach Analysis
 About 42% of the US adult population
visited the beach every year (EPA, 2015)
 About 6,200 beaches in the US (EPA, 2015)
 Beaches are owned by municipalities
 More than $320 billion annual revenue
from US beaches (ASBPA, 2014 )
 Beach management in the US cost less than
4% of 2.65 billion annual park service
budget (ASBPA, 2014 )
• Example: Ocean City beach patrol expenses
2.3 million (Town of Ocean City Adopted
budget, 2015)
3
Beach Rescues
 Rip currents are the primary cause of rescue
• Rip currents account for 81% (334,184) from 2003 to 2012
• Note:
– Some Beach Agencies Only Report Totals For Fatalities and Rescues
– Some Beach Agencies Do Not Report Certain Subcategories
– Some Beach Agencies Do Not Report to USLA
Number of People
50,000
40,000
30,000
20,000
0
2000
40000
Rip
Current,
334184,
Surf,
81% 73670, 18%Swiftwater, Scuba,
2459, 0% 2538, 1%
300000
200000
100000
0
30000
20000
10000
0
Rip
Current, Surf, 7288,
35935, 82% 17% Swiftwater, Scuba, 272,
307, 1%
0%
Rescues
Rip Current
4
Surf
Swiftwater
Scuba
Rip Current
Rescues
Surf
Swiftwater
Scuba
2005
Year
2010
2015
Total Rescues
Rip Current Primary Cause of
Rescue 2012
Number of People
400000
y = 889.41x - 2E+06
10,000
(USLA, 2013)
Rip Current Primary Cause of
Rescue 2003 – 2012
Rip Current Rescues
90,000
80,000
70,000
60,000
50,000
40,000
30,000
20,000
10,000
0
2000
y = 1163.4x - 2E+06
2005
2010
Year
2015
Surf Zone Fatalities 2014 Total
Rip Current,
79%
90%
80%
150
y = 0.0545x - 20.436
100
50
0
2000
2005
2010
2015
Year
70%
60%
Number of People
Beach Fatalities
Number of People
Total Unguarded Deaths
60
20
0
2000
Sneaker
High Surf, 7%Wave, 3% Other, 6% Unknown, 5%
20%
10%
0%
Fatalities
Rip Current



High Surf
Sneaker Wave
Other
30
25
20
15
10
5
0
2000
Unknown
Fatalities From Rip Current Accounted For 79% in 2014
10 Year Average for Annual Rip Current Fatalities is 51
Annual Deaths Due to Rip Currents Exceed 100
•
Note:
–
–
–
5
Some Beach Agencies Only Report Totals For Fatalities and Rescues
Some Beach Agencies Do Not Report Certain Subcategories
Some Beach Agencies Do Not Report to USLA
y = 0.6727x - 1332.4
2005
2010
Year
2005
2010
2015
Year
Rip Current Guarded
Deaths
2015
Number of People
30%
Number of People
40%
y = 0.6x - 1176.2
40
Total Guarded Deaths
50%
Rip Current Unguarded
Deaths
10
NOAA, 2015
USLA, 2014
y = 0.1909x - 379.16
5
0
2000
2005
2010
Year
2015
Rip Current Circulation Diagram
Rip Current
Measurements
Surf Zone
Width
[10,200] feet
Length
~[100,1000] feet
Speed
[1,8] feet/second
Shoreline
Neck
Width
Length
Speed
Head
USLA, NOAA
http://floridadisaster.org/EMTOOLS/Severe/document
s/Rip%20Current%20Brochure.pdf
Feeder
Current
6
Rip Currents Formation
 Waves travel from deep to shallow
water, they break near the shoreline
(Next Media Animation, 2011)
• Generate currents flow offshore (rip)
and alongshore (feeder)
 Waves flowing through sandbars
 Rip currents form between cusps
 Hard Structures
• Reefs, jetties, piers, or other man made
structure
• Deflect longshore current in an offshore
direction
 Some last for many days or months
 Some form quickly and last hours or
days to disappear
(NOAA, 2004)
7
Rip Current
SEQUENCE EVENTS IN DROWNING
1.
2.
Victim is caught
in a rip current
6.
Victim tries to
fight rip current
7.
Water reaches
airway
8.
Throat Spasms
Dry-Drowning
(Forensic pathology online, 2013)
8
3.
Victim gets
exhausted or
is dehydrated
or has trouble
swimming
Lungs seal &
water
accumulates in
stomach
4.
5.
Victim Panics
Body
accumulates
carbon dioxide
10.
9.
Victim becomes
unconscious
Throat relaxes
11.
Water flows into
the lungs
Secondary Drowning – Pulmonary Edema
Process of Lifeguard rescuing victim
LG keeps an
eye on Rip
Currents
Identify
Drowning
Victim
max 10 s
Lifeguard
Radio
Control
RM
max
2s
Emergency
Care
Provided
LG swims to drowning victim
LG Rescues
max 90 s
max 30 s
LG Guides victim to shoreline
max 90 s
Victim
4.
5.
Body
accumulates
Victim Panics
carbon dioxide
9
6.
Water reaches
airway
7.
Throat Spasms
Victim out
of water
max 20 s
…
8.
max 4 min
Performance Gap
Max Victim Survival Time
Time (s)
Lifeguard
Reach Time
Max Victim
Survival if
fighting against
current
Time (s)
60
93
Red area = victims in danger of drowning
10
*not in scale
 There is a gap between victim survival
time and lifeguard rescue time.
 Reduce the rip current-related
fatalities to X/yr from the current
average of 51/yr.
1. Context
2. Stakeholders
3.
4.
5.
6.
7.
8.
9.
Problem/Need Statements
Requirements
Con-Ops
Alternatives
Method of Analysis
Management
Thanks
Stakeholders
1.
Lifeguarding Associations
2.
Lifeguards
3.
Beach Goers
4.
Manufactures
5.
Municipalities
12
•
•
•
usla.org (United States Lifesaving Association)
Redcross.com
Jellis.com (Jeff Ellis & Associates-International Lifeguard Trainings)
•
•
•
•
Sarah Litowich, an aquatic director of the Aquatic Fitness Center at George Mason
Captain Butch Arbin III, Ocean City beach patrol officer in Maryland
Captain Barry Kirschner, Virginia Beach Dep. of EMS emergency medical technician-enhanced
Dane Underwood, Red Cross and Ellis and Associates certified instructor
•
•
Want least restrictions
Want lifeguards to be 100% effective at their jobs
•
•
Produce equipment to lifeguards who pay the manufactures money
Ex: Swimoutlet, Marine Rescue Products, USLA
•
•
Beach owners have to warn non-trespassers about dangerous conditions on their property
States own land seaward of the high tide line
Tensions
Provide revenue
Provide clean beaches
Municipalities
(Beach Owner)
Accident/Injury
Liability
Municipalities
(Beach Operator)
Beach Goers
LG
protection/
rescue
services
Lifeguards
Life guarding
associations
(Certification company)
13
Feedback Loops
Equipment
Manufactures
Liability
Provide clean beaches
Municipalities
(Beach Owner)
Accident/Injury
Liability
Provide revenue
Municipalities
(Beach Operator)
Beach Goers
 Beach owner is liable for beach goers
LG
protection/
rescue
services
 Beach owner is protected under the catastrophic
umbrella insurance for huge damage
 Beaches are kept clean by the revenue BG
generate
14
Lifeguards
Certification
Municipalities
(Beach Owner)
Municipalities
(Beach Operator)
 LG Associations train professional
LGs
 Beach operator documents yearly
certification and training of LGs
Lifeguards
Life guarding
associations
(Certification company)
15
Feedback for Manufacturers
Municipalities
(Beach Operator)
 LG associations, Beach operator
and LGs provide feedback of
equipment manufactures produce
Lifeguards
Life guarding
associations
(Certification company)
16
Feedback Loops
Equipment
Manufactures
Win-Win
Lifeguarding
Operators
Lifeguards
• Reduce legal actions and save lives.
• Improve rescue process and save lives.
Beach Goers
• Increase safety of beaches without added regulation
• Decrease rip current-related deaths
Manufactures
• Allow system to use any life ring/ lifesaving device
• Let beaches use the devices they want within a
certain weight limit (no switching manufacturers)
Municipalities
• Increased safety leads to more beach goers, which
lead to more beach services used
No stakeholder is against this Life-Ring Drone Delivery System
17
1. Context
2. Stakeholders
3. Problem/Need Statement
4.
5.
6.
7.
8.
9.
Requirements
Con-Ops
Alternatives
Method of Analysis
Management
Thanks
Problem/Need
Problem Statement
 Rip tides are, on average:
• Annual beach rescues: 81% (USLA,2014)
• Annual beach fatalities: 79% (NOAA,2014)
• Average annual fatalities: 51 (NOAA,2015)
 Lifeguards can reach victims in a max time of 92 seconds (Butch,2015)
• Some victims have survival times as low as 60 seconds.
Need Statement
 There is a need for a system that can reach and assist a victim in under 60 seconds (while
the victim are still an active drowner) in order to increase the victim's survival time.
 By decreasing flotation device delivery time, we can reduce drowning deaths by X%.(TBD)
19
System Scope
 Design a rescue drone delivery system
• Reach victims using camera systems
• Drop flotation device using 1st tether
release
• When victim grabs lifesaving device, 2nd
tether release drops the lifesaving device
and tether, allowing drone to return
home.
 Determine the best possible design to:
•
•
•
•
Motor
Drone Platform (quad/hexa/octo)
Battery
Flotation Device
 Design a tether holding/releasing system
20
In the end, deliver:
1. Drone System Design
1. Business model and Cost Model
2. Rescue System Design
1. Draft training methods and user manual
Tether Hold/Release System
Front and Down Cameras
Tethered Lifesaving Device
1. Context
2. Stakeholders
3. Problem/Need Statements
4. Requirements
5.
6.
7.
8.
9.
Con-Ops
Alternatives
Method of Analysis
Management
Thanks
Mission Requirement
MR.1 The system shall reduce the
average annual number of rip current
deaths by a minimum of X%.
22
Functional Requirements
F.1 The system shall hover at a minimum altitude of 3m above the ground.
F.1.1 The system shall hover at an altitude of 3m with a minimum payload of 2.268kg.
F.2 The system shall be operable within X m of the home point.
F.3 The system shall reach a victim within X seconds.
F.3.1 The system shall increase the victim survival time by an average of X seconds, if the
system does reach the victim.
F.4 The system shall be able to restock its payload within X seconds.
F.5 The system shall be able to deploy its payload within X seconds.
F.6 The system shall do the entire rescue process at a maximum time of X seconds.
F.7 The system shall be able to hover within a horizontal distance of 0.5m from the target.
23
Design Requirements
DR.1 The system shall attach the lifesaving device to the drone through a tether.
DR.1.1 The system may have a disconnect method to cut or release the tether in order to deliver the
lifesaving device.
DR.1.2 The system shall have a tether release system that weighs under X kg.
DR.1.3 The system shall be able to release the tether within X seconds of the request to release.
DR.2 The system shall have a camera system pointing downward.
DR.3 The system shall have a camera system pointing forward.
24
Ilities Requirements
Usability
U.1 The system shall be usable by a person that has less than 12 hours of training.
Availability
A.1 The system shall be available to at least any beach on U.S territory
A.1.1 The system shall comply with all federal drone regulations.
A.2 The system shall be available for rescues over 95% of the time.
A.3 The system shall be usable in X rescues a day when balanced charged.
A.4 The system shall have a minimum lifetime of 5 years
Reliability
RE.1 The system will have MTBF of X months
RE.2 The system shall have a tether system error MTBF of 7 days
Resistability
RS.1 The system shall resist sand conditions of an average beach.
RS.2 The system shall resist humiditity conditions of an average beach.
RS.3 The system shall resist temperature conditions.of an average beach.
25
FAA UAS Regulations
Current Advisories
Proposed Regulations
 UAS flight altitude below 400 ft.
 UAS weighs under 55 lbs.
 Maintain visual line of sight of the UAS




• Spotter allowed
– Minimum 1 spotter per UAS
 UAS operator must have a pilot's license
 UAS may not be operated in restricted
airspace
• Spotter allowed
– Minimum 1 spotter per UAS

26
UAS operator:
• Be licensed
• Report incidents in less than 10 days
• Make UAS available for inspection
• (grey area)
• not applicable to government
 UAS may not be operated for commercial
purposes
 No Overhead Operation !!!
UAS flight altitude below 500 ft.
UAS weighs under 55 lbs.
UAS may not exceed 100 mph
Maintain visual line of sight of the UAS



3 mile visibility from control station
Inspect UAS prior to flight
No Overhead Operation !!!
Source: http://www.faa.gov/uas/
1.
2.
3.
4.
Context
Stakeholders
Problem/Need Statements
Requirements
5. Con-Ops
6.
7.
8.
9.
Alternatives
Method of Analysis
Management
Thanks
LG keeps an
eye on Rip
Currents
max 10 s
Rescuing Process with Drone
max 2
s
Identify
victim
Radio
Contr
ol Rm
max 90 s
LG swims to drowning victim
Emergency
Care
Provided
max 30 s
max 90 s
LG Rescues
LG Guides victim to shoreline
Control Rm
receives
Coordinates
Victim out
of water
Drone
leaves
home point
Stage
1
28
max 20 s
Drone
travels to
victim
NO
Stage 2
YES
Drops
tether w/
ring buoy
Victim grabs
buoy, tether
is released
Drone
returns to
home point
(Butch,2015)
Con-Ops
Precondition: Lifeguard has identified a drowning victim. Lifeguard is prepared for rescue process. Lifeguard radios control room of the section # or victim’s
general direction. Victim is located somewhere on the rip current and is attempting an escape method. Drone is ready to deploy. Flotation device is stocked
on drone.
Primary: Stage 1

Controller is informed by lifeguard of general area of the victim

Controller takes off drone
•



Confirm victim location by eyesight if near tower
The system takes off to a height of X meters.
The system accelerates to X m/s towards the section given.
Controller confirms specific location in that section through camera or eyesight.
•
Relative to Drone
The system maintains X m/s towards the victim's location.
Once the system is within X m of the victim’s location, system shall decelerate to victim’s speed and position. At the same time, the system will reduce
height until the flotation device is just above the water (confirmed by controller).
Primary: Stage 2

The system drops the flotation device and positions it by the victim

Once the victim is about to grab the the flotaton device, system detaches the tether.

The system maintains a X m hover over victim until lifeguard has reached the victim.


•
•
Controller uses camera to visually determine victim state (active or passive)
If necessary Controller inform medical personnel of victim status
Primary: Return

Once lifeguard has reached the victim, or drone has been determined to be of no further use, or drone has reached critical battery charge, system will
be flown back to the home point.

System lands on home point.
Post-Condition: Lifeguard is enacting the rest of rescue process starting with rescuing the victim. Drone has landed back at the home point and awaits
restocking of ring buoy. Victim is being helped by the lifeguard.
29
Identify
•Prepared for rescue
•Identify Victim
•Radio control room
Shoreline
Beach
Area
•Flotation device stocked
•Prepared to deploy
30
•attempting escape method
Stage 1
•Lifeguard swims to drowning victim.
Shoreline
Beach
Area
•Leaves homepoint
•Travels to victim
31
Stage 2
•Victim grabs flotation device
•swims to drowning victim.
Shoreline
Beach
Area
•Drops tether with ring buoy
•Releases tether when victim grabs ring buoy
32
Return
Shoreline
Beach
Area
•Drone returns to homepoint
•Drone is ready to be resupplied
33
•Lifeguard continues rescue process
1.
2.
3.
4.
5.
Context
Stakeholders
Problem/Need Statements
Requirements
Con-Ops
6. Alternatives
7. Method of Analysis
8. Management
9. Thanks
Design
Alternatives
Design of Experiment
 Set A
 DoE A
• Location of drone station
 Set B
• Design of drone
 Set C
• Choice of flotation device
35
• Location of drone station (TBD)
 DoE B
• Design of drone (TBD)
Set A: Drone Location
Section
 Option 1: main control room.
• Operation range of multiple
lifeguard towers.
• Easier to charge drone. Safer for
the drone.
Victim
3. Boat
 Option 2: near guard towers.
• Operation range of the nearest
lifeguard towers.
• Closer to shore and allows eyesight
to confirm victims.
 Option 3: At Sea
• Avoid Regulatory problems
36
1.
Control
Room
2. Tower
Tower
Set B: Design of Drone
 Motors
 Drone Platform (quad/hexa/octo)
 Battery
37
Set C: Flotation Device
Flotation
Device
38
Cost
Weight
Dimensions
Buoyance
Effectiveness
(5 Star)
Usability
(5 Star)
Ring Buoy
(Jimbuoy
JBW-20)
$85.98
3 lbs.
20 in
16.5 lbs.
5
5
Rescue Can
(Jimbuoy
model 8t)
$139.99
4 lbs.
29.5x9.5 in
18.2 lbs.
2
2
Lifejacket
(First Mate –
Stearns
flotation)
$74.99
1.5 lbs.
24x12x3 in
15.5 lbs.
4
4
Ultra 3000
(Auto
inflating life
jacket)
$204.99
3 lbs.
30x52 in
37.7 lbs.
3
3
Set C: Floatation Device AHP Analysis
Buoyance
Time of
Delivery
Effectiveness
Usability
Dimensions
Buoyance
1
1/2
5
5
5
Time of
Delivery
2
1
7
7
7
Effectiveness
1/5
1/7
1
1/2
1
Usability
1/5
1/7
2
1
3
Dimensions
1/5
1/7
1
1/3
1
• Time of Delivery & Buoyance most important
• Highest rated
• Used Intensity of importance scale to rate others
39
• Comparing 5 factors
• AHP Analysis to find
the best alternative
• Found weights of
each factor
• Still need to
calculate the best
alternative by using
weights
1.
2.
3.
4.
5.
6.
Context
Stakeholders
Problem/Need Statements
Requirements
Con-Ops
Alternatives
7. Method of Analysis
8. Management
9. Thanks
Drone Info
•Quadcopter = 4 rotors
•Hexacopter = 6 rotors
•Octocopter = 8 rotors
•Opposite rotors have same spin.
•2 rotors rotate counterclockwise
•the other 2 rotate clockwise
•This allows drone body to choose to rotate, or not rotate,
depending on the rotational velocity of the rotors.
•Picture on left shows clockwise spin being stronger, thus the
drone rotates counterclockwise.
41
Stronger clockwise motors =
Body rotates counterclockwise
Orientation
Positive x-axis = front side (direction of motor 2)
Positive y-axis = left side (direction of motor 3)
Positive z-axis = top side
Body Frame
Body frame = body reference = drone reference
Inertial Frame = our reference = our point of view
X
Y
42
Inertia Frame
Controller
Axis's of Rotation (Euler Angles)
Roll, Yaw, Pitch

Z
 φ (roll)
 θ (pitch)
 ψ (yaw)
Counterclockwise = positive

Combined
Rotational
Matrices
43
http://theboredengineers.com/2012/05/the-quadcopter-basics/
 cos  cos
R  R R R   cos  sin

sin 
Rational
Matrix for
Angular
Velocity
Y
X
 X  1
    0
 Y 

 Z 
 
0
sin cos   sin  sin  cos
cos  cos  sin  sin  sin
 sin  cos 
0
cos 
 sin 
 sin     
 
sin  cos  
  

cos  cos  

 
sin 
0
 cos

R  

sin

cos

0



0
0
1


cos  0  sin  

R  
0
1
0



0
cos  
 sin 

0
0 
1

R  
0
cos

sin




0  sin  cos  

sin  sin  cos  sin  cos 
sin  sin  cos  sin  cos 

cos  cos 

 Kt ( I  I 0 )
Electrical-Mechanical Power
V  IRm  K v
Now that we have terms for current and voltage, we
can find power produced by motor
P = power = I*V
Assuming that Kt*I0 << τ and negligible motor
resistance.
Variable 1
Relation
Variable 2
Proportionality
Coefficient
Equation
τ
∝
I
Kt
τ = Kt * I
τ
∝
T
Kτ
τ = Kτ * T
V
∝
ω
Kv
V = Kv* ω

•
•
•
•

•
•
•
Torque produced by motor
τ = torque generated by motor
Kt = torque proportionality constant
I = input current
I0 = current when there is no load on motor
–
Considered Negligible
44
Voltage drop across motor
V = voltage
I = current
Rm = motor resistance
–
•
•

Considered Negligible
Kv = back-EMF per rpm (coefficient)
ω = angular velocity of the motor
Manufacturers use inverse of Kv
Kv
P

Kt
  K T
K v K
P
T
Kt
 x  0 
m  y   0   RTbody  FD  Flifevest
 z  mg 
T [
Tbody

2
D 2 P 2 ]
1
3
 0 
K K




D 2 ( v  ) *  0 
2
Kt
 i 2 



K v K
k 
D (
)
2
KT
Tbody
45
2
 0 


 k * 0 
  i 2 


Linear Dynamics
m*a = ∑F
Force of lifevest =
Force of lifevest drag +
Force of lifevest weight (mg)
v x2 
1
 
FD  C D  v y2  A
2
v z2 
 









R = body-to-inertia
transformation matrix
TB = Thrust in body-frame
FD = force of drag due to air
Frope = force due to rope interaction
Flifevest = force due to vest interaction
-mg = force due to gravity
FD= drag force (from fluid)
CD= drag coefficient (determined
experimentally)
v = velocity of body in perspective of fluid








A = reference area
PD= power needed to overcome drag
Tbody = total thrust on body of drone
ωi = angular velocity of ith motor (in the
reference of the body)
T = Thrust
D = diameter of propeller
ρ = density of air
P = power produced by propeller
Free Body Diagram
Side-view
46
Z-axis Torque per motor








Each propeller can spin the body of the drone AKA provide torque from drag forces from the air onto the body.
A = propeller cross section (not swept area)
r = radius of the propeller.
CD = constant
τD = torque due to drag
τZ= torque in z-axis (in reference of body)
ω= angular velocity
ωdot= angular acceleration
•

Considered neglible
IZ= moment of inertia around the motor Z-axis
1
2
2
 D  rC D A( r ) ( )
2
1
2
b  rC D A( r )
2
47
 Z  b  I Z 
2
Torque of body
X
X
4
2
 Torque = Σ(Thrust x radius)
 Opposite rotors have spin
Y
• To have the same thrust
while rotating, one rotor
must decrease and one
must increase in angular
velocity in a rotor pair.
 L = distance between
motor and center of body.
 Assume angular
acceleration is negligible
48
Y
3
1
X
4
3
Y
4
2
6
1
8
1
5
B
5
7
2
3
6
2
2

 roll
Lk (1  3 )


2
2

Lk (2  4 )
 pitch
b( 2   2   2   2 )  yaw
1
2
3
4


Rotational Dynamics
I   mi ri   I i
2
rc
mr


m
i i
i
 Euler’s Equation on Torque
•
•
•
•
49
τ = torque
I = moment of inertia
ω = angular velocity
m = mass
  I    ( I)
0
0 
 I XX
I   0 I YY 0 
 0
0 I ZZ 
 x 
   y   I 1 (    ( I ))
 z 
 I YY  I ZZ



y z

  I XX 1   I XX


 I I
    I YY 1    ZZ XX  x z 


 I 1   I YY

  ZZ  I XX  I YY

 x y 
 I ZZ

1.
2.
3.
4.
5.
6.
Context
Stakeholders
Problem/Need Statements
Requirements
Con-Ops
Alternatives
7. Method of Analysis
DoE / Simulation
8. Management
9. Thanks
Drag DOE
 Determine the force of drag acting on the S900.
• Needed to accurately create a simulation of the drone.
 To determine the force of drag:
• Perform a flight test of the drone.
• Collect its telemetry.
• Broken down into:
– Horizontal force of drag.
– Vertical force of drag.
• At different speeds
– To know how much /if Cd materially changes.
51
Drag DOE
Inputs
Procedure
1.
Horizontal 2.
3.
CD test
4.
Vertical
CD test
52
fly
fly
fly
fly
30 m north
30 m east
30 m south
30 m west
1. Ascend 30 m
2. Descend 30 m
Outputs
Height
Maintain
constant
10 m
At least
10 m
above
ground
Flight
Speed
#1
1 m/s
#2
5 m/s
#3
10 m/s
#4
15 m/s
#1
1 m/s
#2
5 m/s
Pitch
Roll
Wind
Velocity speed
Altitude
Distance
Motor Parameter DOE
 To simulate the DC electric motors of the S900 we need
to determine:
• Torque-Speed curve
• Power-Speed curve
• Torque-Current curve
 The curves will be used to find:
• No load current
• Torque constant
• Torque to thrust constant
53
Motor Parameter DOE
Inputs
Voltage
Outputs
Torque
Current
Speed (RPM)
http://www.micromo.com/technical-library/dc-motor-tutorials/motor-calculations
54
Resistance
1.
2.
3.
4.
5.
6.
Context
Stakeholders
Problem/Need Statements
Requirements
Con-Ops
Alternatives
7. Method of Analysis
DoE / Simulation
8. Management
9. Thanks
Simulation
56
•
MATLAB and Simulink
•
Goal: Simulation verify that the system meets the requirements
o MR.1 The system shall reduce the average annual number of rip current
deaths by a minimum of X%.
o Design of Experiments will verify the simulation.
Simulation Requirements
SR.1 The system shall be able to fly towards a waypoint and maintain position
within 0.5m of the waypoint.
SR.2 The system shall have one run simulated under 1 minute.
SR.3 The system shall simulate wind and weight interactions with the drone.
SR.4 The system shall model drone rotational and translational dynamics.
SR.5 The system shall model the lifeguard-victim rescue process up until the
lifeguard reaches the victim.
SR.5.1 The system shall model the three victim escape methods (swim
parallel to neck, swim against the neck, float)
SR.5.2 The system shall model riptides of length 100/200/300/400/500
meters.
SR.5.3 The system shall model the lifeguard speed on land and on water as
an average velocity of X m/s and Y m/s respectively.
57
Simulation Requirements conti.
Input Requirements
IR.1 The system shall inputted a victim swimming method. It will pick between floating, swimming parallel
against the shore, and swimming parallel to shore.
IR.1.1 The system shall model the swimming methods as velocities.
IR.1.2 The system shall be inputted a random victim survival time
based on the swimming method chosen.
IR.2 The system shall be inputted a random rip current speed. The speed will be chosen by a random distribution
with mean X and variance X.
Output Requirements
OR.1
OR.2
OR.3
OR.4
58
The system shall output the victim position over time.
The system shall output the lifeguard position over time.
The system shall output the drone position over time.
The system shall output 1 or 0 depending if the lifeguard rescue time is under victim survival time.
OR.4.1 The system shall detect if the drone reached the victim before
the lifeguard and increase victim survival time by X seconds.
Simulation Model
1. Generate victim
position over time
2. generate lifeguard
position over time
4.
a.
3. generate drone
position over time
59
b.
c.
d.
Pass judgment
If drone reached victim before survival
time ended and before lifeguard, drop life
ring (increase survival time by X seconds).
If lifeguard reaches victim before survival
time, victim is saved.
If lifeguard does not reach victim before
survival time, victim is lost.
Save result
Victim Model and Lifeguard Model
60
Drone Model
61
62
Linear Dynamics
63
64
Rotational Dynamics
65
66
67
Derived through online documentation
and flight experiments
Hexacopter Base Model
68
Constants
Meaning
Kt
Value
Constants
Meaning
Propor. Const.
LR Cd
Ring drag coeff.
Kτ
Propor. Const.
LR Ax
Area of ring horiz.
Kv
Porpor. Const.
LR Az
Area of ring top
D
Rotor diameter
LR m
Ring mass
ρ
Air density
Ixx
Mom. of Iner. X-axis
CD
Drone drag coeff.
Iyy
Mom. of Iner. Y-axis
AX
Drone Area X-view
Izz
Mom. of Iner. Z-axis
AY
Drone Area Y-view
Battery Mass
AZ
Drone Area Z-view
Battery Capacity
15000mAh
m
Drone mass
Tether Syst. Mass
0.5kg
L arms
Radius of arms
from center
Tether Density
b
Rotor Yaw Const.
Camera Mass
Ar
Rotor Cross Section
1/400
1.225kg/m3
Value
2.268kg
Tether Length
1.0kg
Two Simulation Models
GPS Mode
•
Maximum tilts and velocities
•
Maintains altitude for
horizontal movement inputs
and no inputs
Current Simulation has:
•
9 PID controllers per model
•
350 lines of code per model
•
69
6 models
(simplified/vigorous)
(quad/hexa/octo)
• Simplified Model
•
Pro
•
•
Simpler to implement
Con
•
Settle time is longer
•
Does not care about max speed (unrealistic)
• Vigorous Model
•
Pro
•
•
Reaches and maintains max speed (until close to
victim)
Con
•
More unstable movements
•
Takes longer to run simulation
Stationary Target
70
Moving Target 5m/s
Stop & Move, Overshoot
71
Stop & Move, Jumping
Victim – Lifeguard – Drone Simulation
•Victim
•Lifeguard
•Drone
Victim – spotted 10m ahead, 25m to the left of lifeguard, floating
Lifeguard – already spotted victim, runs on land to current, swims ahead, 3m/s
Drone – Lifts off when lifeguard starts to run, overshoots some.
Rip current – 8m/s
72
Future Work
 WBS 7 DoE
• WBS 7.3 Design
– 7.3.1 Motors
– 7.3.2 Drone Platform
(quad/hexa/octo)
– 7.3.3 Battery
• WBS 7.4 Location
 WBS 11 Rescue System
73
 WBS 8.1.8, 8.1.9, 8.2, 8.3 Complete Simulation
 WBS 6.3 - Sensitivity Analysis
 WBS 6.5 Utility Model
1.
2.
3.
4.
5.
6.
7.
Context
Stakeholders
Problem/Need Statements
Requirements
Con-Ops
Alternatives
Method of Analysis
8. Management
9. Thanks
WBS
Top level WBS
The project’s major tasks and
subtasks
Stakeholder analysis, DOE, and
especially the simulation are
the most important of the
work.
75
Critical Path
#
18
21
22
29
31
33
35
36
37
40
52
56
77
79
80
81
89
90
97
102
104
105
106
WBS
3.2.3
4.2
4.3
5.1.4
5.1.6
5.1.8
5.1.10
5.1.11
5.1.12
5.2.2
6.3
6.4.3
8.1.7
8.1.9
8.2
8.3
9.2.1
9.2.2
9.4.3
10.1.2
10.2.1
10.2.2
10.2.3
76
Task Name
Rescue Process Diagrams
Functional Requirements
Design Requirements
Evaluate Drone Battery Alternatives
Evaluate Drone Motor Alternatives
Evaluate Drone Rotor Alternatives
Evaluate Drone Location Alternatives
Research Drone Configuration Alternatives
Evaluate Drone Configuration Alternatives
Evaluate Flotation Device Alternatives
Sensitivity Analysis
Simulation Risk Analysis
Create Rip Current Model
Create GUI
Simulation Testing
Perform Sensitivity Tests
Faculty Presentation Creation
Faculty Presentation
Spring Brief 3
Proposal Final Report
Draft Conference Paper
Draft Poster
Final Reports and Stuff
Start
10/8/15
10/30/15
10/31/15
3/31/16
3/17/16
3/19/16
3/14/16
10/1/15
10/3/15
10/15/15
3/25/16
11/27/15
2/13/16
2/27/16
3/14/16
3/25/16
11/14/15
11/20/15
3/14/16
12/9/15
12/9/15
12/9/15
11/23/15
Finish
1/23/16
11/27/15
11/27/15
4/2/16
3/19/16
3/23/16
3/17/16
10/3/15
10/27/15
4/28/16
4/3/16
12/5/15
2/27/16
3/14/16
3/25/16
4/3/16
11/19/15
11/20/15
3/14/16
12/9/15
12/9/15
12/9/15
12/8/15
Schedule
77
Schedule
78
Schedule
79
Cost, Schedule Variance & CPI, SPI
80
Earned Value
Actual cost (ACWP)
 Has been above our Earned Value
(BCWP).
 Currently below Earned Value.
Planned Value (BCWS)
 Has been roughly equal to Earned
Value
 Currently below Earned Value
 Currently we are under budget
 Currently we are ahead of schedule
81
Project Risks
Risk
Simulation Control Structure is not
done by Nov. 15th (2 weeks behind
schedule)
Severity
8
Likelihood
10
Detectability
1
Score
80
Revert to old model with no control. Manually
adjust voltages in order to get the right distance
and other values needed.
Simulation Testing is Delayed by X
days beyond scheduled due date
10
3
5
150
Do primary analysis of the drone’s effectiveness in
reducing fatalities. Forgo all other simulation
tests until we find time again.
Evaluate life saving device
alternatives is not done, ring buoy
information is wrong
9
3
5
135
Find other life saving devices with accurate
information about them and evaluate them/
Perform the flight experiment again until we get
accurate data. Use pocket money to get program
and tablet that can watch the instruments.
Gather accurate information about
force, pitch, roll, yaw, velocity,
height and wind speed
7
4
4
112
Unable to acquire tools to perform
experiments
10
6
1
60
82
Mitigation
Use the University’s lab experiments to get the
tools.
1.
2.
3.
4.
5.
6.
7.
8.
Context
Stakeholders
Problem/Need Statements
Requirements
Con-Ops
Alternatives
Method of Analysis
Management
9. Thanks
Special Thanks
 Brett Vilcovoch and Brian Yi of Expert Drones
• For the use of one of their drones
 Dane Underwood
• For helping us understand lifeguarding
 UAS Collision Avoidance System Project Team
• For help understanding FAA regulations
 Professor Lance Sherry and Barham Yousefi
• For the guidance in making this project
84
Special Thanks
 Professor Peggy Brouse
• For the sweet PowerPoint theme
 All our Teachers
• For the knowledge to complete this project
 George Mason Faculty and Staff
 Fellow Systems Students
85
Sources







86
EPA, LEARN: Beach Basics, 2015. [Online]. Available: http://www2.epa.gov/beaches/learn-beachbasics. [Accessed: 14- Nov - 2015].
EPA, National List of Beaches, 2015. [Online]. Available:
http://ofmpub.epa.gov/apex/beacon2/f?p=117:12:6598228724511::NO::P12_YEARS:Current.
[Accessed: 14- Nov - 2015].
American Shore and Beach Preservation Association, New study shows beaches are a key driver of
U.S. economy, 2014. [Online]. Available:
http://www.asbpa.org/news/Beach_News/080814Houston.pdf. [Accessed: 14- Nov - 2015].
Ocean City Maryland, Town of Ocean City Adopted budget, 2015. [Online]. Available:
http://oceancitymd.gov/City_Manager/BudgetBook.pdf. [Accessed: 14- Nov - 2015].
USLA, 'Primary Cause of Rescue at Surf Beaches', 2015. [Online]. Available:
http://arc.usla.org/Statistics/Primary-Cause-Analysis.pdf. [Accessed: 18- Oct- 2015].
USLA, 'Statistics', 2015. [Online]. Available: http://arc.usla.org/Statistics/public.asp. [Accessed: 18Oct- 2015].
National Oceanic and Atmospheric Administration, 'U.S Surf Zone Fatalities 2015', 2015. [Online].
Available: http://www.ripcurrents.noaa.gov/fatalities.shtml. [Accessed: 18- Oct- 2015].
Sources cont.







87
National Oceanic and Atmospheric Administration, 'List of Severe Weather Fatalities', 2015. [Online].
Available: http://www.nws.noaa.gov/om/hazstats/resources/weather_fatalities.pdf. [Accessed: 18Oct- 2015].
USLA, About Rip Currents. [Online]. Available: http://www.usla.org/?page=RIPCURRENTS.
[Accessed: 25- Oct- 2015]
http://floridadisaster.org/EMTOOLS/Severe/documents/Rip%20Current%20Brochure.pdf
National Oceanic and Atmospheric Administration, Rip Currents. [Online]. Available:
http://www.ripcurrents.noaa.gov/resources/Final%20Talking%20Points%20and%20Fact%20Sheet_041
707.pdf. [Accessed: 25- Oct- 2015].
National Oceanic and Atmospheric Administraion, Rip Current Science, 2004. [Online]. Available:
http://www.ripcurrents.noaa.gov/science.shtml.[Accessed: 25- Oct- 2015]
https://www.youtube.com/watch?v=d8c7RJx5pBg
NOAA's SciJinks, 'How to Escape Rip Currents', 2015. [Online]. Available:
http://scijinks.jpl.nasa.gov/rip-currents/. [Accessed: 18- Oct- 2015].
Sources cont.







88
V. Gensini and W. Ashley. An examination of rip current fatalities in the United States, August
2009. [Online]. Available:
http://weather.cod.edu/~vgensini/files/pubs/Gensini%20and%20Ashley%202011a%20NH.pdf.
[Accessed: 25- Oct- 2015].
A. Gibiansky, 'Quadcopter Dynamics and Simulation', Andrew.gibiansky.com, 2015. [Online].
Available: http://andrew.gibiansky.com/blog/physics/quadcopter dynamics/. [Accessed: 18- Oct2015].
S. Litovich, 'Drowning Information and Drone Considerations', GMU AFS, 2015.
B. Arbin III, 'Lifeguarding Information', 2015.
D. Underwood, 'Lifeguarding Litigation and Insurance', GMU, 2015.
Jimbuoy, ‘Marine Product List’, 2015. [Online].Available: http://www.jimbuoy.com/index.htm.
[Accessed:18- Oct- 2015].
CreateDJI, 'Spreading Wings S900 - Specs | DJI', 2015. [Online].
Available:http://www.dji.com/product/spreading-wings-s900/spec. [Accessed: 24- Sep- 2015].
Sources cont.






89
CreateDJI, 'Inspire 1 - Specs | DJI', 2015. [Online]. Available: http://www.dji.com/product/inspire1/spec. [Accessed: 24- Sep- 2015].
CreateDJI, 'Phantom 3 Professional & Advanced - Specs | DJI', 2015. [Online]. Available:
http://www.dji.com/product/phantom-3/spec. [Accessed: 24- Sep- 2015].
CreateDJI, 'Spreading Wings S1000+ - Specs | DJI', 2015. [Online]. Available:
http://www.dji.com/product/spreading-wings-s1000-plus/spec. [Accessed: 24- Sep- 2015].
Store.3drobotics.com, 'X8+ - 3DRobotics Inc', 2015. [Online]. Available:
http://store.3drobotics.com/products/x8-plus. [Accessed: 24- Sep- 2015].
Indeed.com, 'Systems Engineer Entry Salary | Indeed.com', 2015. [Online]. Available:
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Battery
Desire Power 10400
Desire Power 12400
Desire Power 20000
Desire Power 8300
Desire Power 16000
AT: Tenergy
Turnigy
Multistar High Capacity
Venom
Turnigy Heavy Duty
MultiStar
Tattu 22000
Tattu 16000
Tattu 12000
Custom 18650 13.6Ah
Custom 18650 10.2Ah
Custom 18650 17Ah
VENOM 15145
VENOM 15143
VENOM 15144
VENOM 15142
1524
1680
2492
1115
2162
866
816.47
1189
547
864
956
2630
1932
1620
1250
877
1900
2800
2300
2300
1716
10400 744310
12400 850640
20000 1177677
8300
536256
16000 950000
7800
433620
5000
589934
10000 537420
3200
230748
5000
421850
8000
438354
22000 1177600
16000 865800
12000 796904
13600 865800
10200 577860.48
17000 900900
22000 1296000
16000 1152000
16000 1048320
12000 864000
35C
35C
25C
35C
35C
20C
10C
30C
60C
10C
25C
15C
15C
45C
30C
45C
30C
182
217
500
290.5
320
6
100
100
96
300
80
550
240
240
20
7
32
990
480
720
360
25000
Energy Output (mAh)
Cost
Battery Mass V. Energy Output
20000
15000
y = 7.6183x + 352.76
R² = 0.9051
10000
5000
0
0
500
1000
1500
2000
2500
3000
Mass (g)
Battery Volume V. Energy Output
25000
Energy Output (mAh)
Source
Energy
Mass Output Volume Discharge Current
(g) (mAh) (mm^3)
Rate
(A)
20000
15000
y = 0.0173x - 1068.1
R² = 0.8908
10000
5000
0
0
200000
400000
600000
800000
Volume (mm^3)
1000000
1200000
1400000
Gap
Max Victim Survival Time
Lifeguard
Reach Time
Fighting
Against
Current
Time (s)
60
91
93
*not in scale
Table of Inputs/ Outputs Simulation Table
Inputs (Random)
Outputs
Baseline
Historic
Rip
Current
Speed
Rip
Current
Length
Rip
Current
Width
Rip
Curren
t YPositio
n
Victim
Escape
Method
Base
Hex
Reach
Time
Base Octo
Reach
Time
Octo 2-ring
Reach
Time
Lifeguard
only reach
time
Victim
Survival Time
…
…
…
…
…
…
…
…
…
…
%
Saved
% Saved
%Saved
%Saved
without
drone
Repeat above for X reps, until %Saved σ <
10%
Result
s: ->
%Saved
Use Grouping for lower sigma count for % saved
92
USLA Data on
Fatalities/Rescu
es
Inputs for Alternatives Analysis (1 at a
time) (same reps as before? Or less reps?)
Outputs (add time to reach as well?)
Location
Battery Type
Motor Types
Base Hex % Saved Base Octo % Saved
3 locations
Use battery
equation
Use motor
equations
Octo 2-ring
% Saved
Design Space for Weight and Power DoE
Inputs
Outputs
Drone Properties and
Base Weight
Added Payload
Maneuvers
Base Hexacopter
1kg
Hover
Const. Velo. Lv. Flight
Accelerating Lv. Flight
3kg
Hover
Const. Velo. Lv. Flight
Accelerating Lv. Flight
Base Octocopter
1kg
Hover
Const. Velo. Lv. Flight
Accelerating Lv. Flight
3kg
Hover
Const. Velo. Lv. Flight
93
Accelerating Lv. Flight
Power Needed to Maintain
Maneuver
Location DoE
Inputs
94
Outputs
Drone
Location
Random:
1. Rip position
2. Victim speed
3. Rip length
4. Identified
Victim
Drone
Velocity
Base
Hexacopter
Location A
(Main Control
Room)
20 reps
12m/s
Location B
(Lifeguard
Tower)
20 reps
Location C
(On a Rescue
ship)
20 reps
10m/s
12m/s
10m/s
12m/s
10m/s
% reached
within 30
sceonds
% reached
within 60
seconds
% reached
within 90
seconds
Lifecycle Cost (2yrs)
Prelim. Cost Model
System Acquisition Cost
Drone Platform
Annual Repair Cost
Camera System
Annual Maintenance
Cost
Tether Release System
Tether
Environment Protection
Equipment
Battery Acquisition
Location Setup
95
Operations and Support
Cost
User manual/Training
Annual Battery
Recharging Cost
Controller’s salary
Disposal
Cost
Prelim Utility Function
u  s S  T TR  E E
S = percent lives saved (%)
TR = mean time to reach victim (sec)
E = mean battery energy usage per rescue (kWh/Rescue)
96
Victim/LG/Rip Current Distributions
 Victim Escape
x  uniform (0,1)
 fight ,0  x  0.4

escape( x)   float ,0.4  x  0.65
 parallel ,0.65  x  1

• Length ~ Unif(100,1000)ft
• Width ~ Unif(10,200)ft
• Position
 Victim Survival
 [TBA,0], escape  fight

victVelo (escape)  
[0,0], escape  float
[TBA, TBA], escape  parallel

 Rip Current Properties
• Speed ~ Unif(1,8)ft/s
97
– Guarded ~ Uniform(0,250)ft
– Unguarded ~ 250+Expo(250)ft
ROPE
BACKUP SLIDES
98
Rope Interactions
 Assuming rope is tense and straight.
Tension = (rope weight per meter) * (length of rope)
Rope Drag = Tension * cos(α)
Rope Torque = radiusbody * sin(α) * Tension
α
99
Catenary Rope
 If rope is slack, use catenary equations to solve for rope
form and tension.







S = arc length of rope
d = height difference between ends
L = horizontal distance between ends
T0 = horizontal tension force on drone
µ = weight per length of rope (weight density)
• µ = mass*acceleration of gravity / total
length
T1 = vertical tension force on drone
s = length of rope between lowest point and
the end (NOT total length)
Equation 1: general form of catenary line
Equation 2: definition of a
Equation 3: definition of λ (helpful variable,
no meaning)
Equation 4: A identity used to calculate T0
1. f ( x)  a * cosh( x / a)
2.a  T0 / 
3.  L /( 2T0 )
4.(sinh  ) /  
5.T1   * s
[1] Dredgingengineering.com, 'Asymmetric Catenary Cable', 2015. [Online]. Available:
http://www.dredgingengineering.com/moorings/catenarya/asymetrische%20afleiding%20goed.htm. [Accessed:
13- Aug- 2015].
100
George Mason University LALVDS Project Team Briefing 4
( S 2  d 2 ) / L2
Removing Homepoint Tether from Simulation?
 On Amazon, a 5mm assessory cord over 100m (~300ft) is 1.84kg.
• 7mm assessory cord over 100m is 3.02kg.
• 8.8mm hiking cord over 100m is 4.82kg.
• 9mm climbing rope over 100m is 6.3kg.
 100m = 328ft (rip currents can be hundreds of feet)
 Hexacopter max lift = 5kg
• Octocopter max lift = 9kg
 Conclusion: A drone lifting a tether from the homepoint to the drone is under
heavy weight. Possibly unable to deliver a life ring.
• Simulation results soon…
http://www.amazon.com/BlueWater-Ropes-Titan-Cord-Dyneema/dp/B00BCLK5CY/ref=sr_1_2?s=outdoorrecreation&ie=UTF8&qid=1445629411&sr=1-2&refinements=p_n_feature_keywords_two_browse-bin%3A7046718011
http://www.amazon.com/Bluewater-7MM-Accessory-Cord-Red/dp/B0011W49HQ/ref=sr_1_5?s=outdoor-recreation&ie=UTF8&qid=1445629411&sr=15&refinements=p_n_feature_keywords_two_browse-bin%3A7046718011
101
http://www.amazon.com/Sterling-Rope-Evolution-Duetto-Orange/dp/B004MXAFNS/ref=sr_1_1?s=outdoorrecreation&ie=UTF8&qid=1445629001&sr=1-1&refinements=p_n_feature_keywords_two_browse-bin%3A7046718011
http://www.amazon.com/CAMTOA-Climbing-Survival-Downhill-Utility/dp/B014XUBYN4/ref=sr_1_11?s=outdoorrecreation&ie=UTF8&qid=1445629133&sr=1-11&keywords=rope+4mm
Drowning
BACKUP SLIDES
102
Drowning
Primary Drowning (Dry Drowning)
Secondary Drowning (Pulmonary Edema)
 Water reaches airway
 Person becomes unconscious
• coughs or swallows water
 Water goes to lower airways
• the throat spasms
• lungs are sealed
• Water accumulates in stomach
• throat relaxes
• allows water to flow into the lungs
 Body accumulates Carbon dioxide
• stimulates to feel the need to breathe
• involuntarily draws in breath
 Large amounts of panic
• rapid movements
(sources?)
103
(note, I'm not sure I got the content
in the right places)
Drowning
Active Drowning
Passive Drowning
 Stage just before submersion
 Will go under water in less than a
minute
 Kicking, waving and squirming for
help
 Head thrown back with face
upward




(Sources?)
104
Unconsciousness
Motionless
Victim floats face down
Hyperventilation
DOE
BACKUP SLIDES
105
DJI Spreading Wings S900
 Takeoff Weight 4.7Kg ~ 8.2Kg
 Total Weight 3.3Kg
 Hover Time 18min
• @12000mAh& 6.8Kg Takeoff
Weight
 Diagonal Wheelbase 900mm
 Rotor
• Size 15×5.2inch
• Weight 13g
http://www.dji.com/product/spreading-wings-s900/spec
106
Horizontal Component of Drag Force
 The forces at a constant velocity.
 The force of gravity
Force of
thrust
Force of
Lift
• Pulling the drone down.
 The force of drag
• Resisting forward motion.
Decompose
 The force of thrust
• Decomposed into:
– Force of lift
Force of Drag
Force of Drag
Force of going
in the forward
direction
• Counters gravity
– Force of forward
• Counters drag.
Gravity
107
Gravity
Horizontal Component of Drag Force
Coefficient of drag can be found
by knowing:
•The force of drag
– can be found by:
• The angle to recompose lift into
forward motion
– the pitch/roll of the drone
•the density of the air
•The speed of the drone(wind
relative to drone)
•The area of the projection
orthogonal to the drone
108
Coefficient of drag:
2 ∗ 𝐹𝐷
𝐶𝐷 =
𝜌 ∗ 𝑣2 ∗ 𝐴
Force of Drag:
𝐹𝐷 = 𝑚 ∗ 𝑎 − 𝑔 ∗ tan 𝑝𝑖𝑡𝑐ℎ
Vertical Component of Drag Force
Later
h
109
 Drone Maintains no
horizontal movement
 Maintains a constant vertical
velocity
Vertical Component of Drag Force
 By conservation of energy:
• The potential energy of the
drone = the kinetic energy of
the drone – the losses due to
friction of the air(drag)
 With the force of drag the
coefficient can be found same
as previous.
110
Conservation of energy
𝑚 ∗ 𝑔 ∗= 1 2 ∗ 𝑚 ∗ 𝑣 2 +𝐹𝐷 ∗ ℎ
Coefficient of drag:
2 ∗ 𝐹𝐷
𝐶𝐷 =
𝜌 ∗ 𝑣2 ∗ 𝐴
111
112
Goal
 To simulate the DC electric motors of the S900 we need
to determine:
• Torque-Speed curve
• Power-Speed curve
• Torque-Current curve
 The curves will be used to find:
• No load current
• Torque constant
• Torque to thrust constant
113
Torque-Current Curve
 No load current
• Point on the torque current curve
– Where torque = 0
– Not equal to zero
 Motor torque constant
• Slope of the torque-current curve
http://www.me.umn.edu/courses/me2011/arduino/techno
tes/dcmotors/motor-tutorial/
114
Torque-Speed & Power-Speed Curves
Motor torque to thrust constant
𝐾𝜏 = 𝜏 𝑇 ,
 2 2 13
T  [ D P ]
2
 Relates:
• Output power of the motor (P)
– Power-Speed curve
• To the torque of the motor (𝜏)
– Torque-Speed curve
http://lancet.mit.edu/motors/motors3.html#torque
115
Torque-Speed Curve
http://lancet.mit.edu/motors/motors3.html#torque
116
Procedure
1. Apply Fixed Voltage to motor
• Not to exceed motor rated voltage
2. Run motor unloaded
• Record RPM
– Torque-Speed curve
• Record current
– Torque-Current curve
http://www.micromo.com/technical-library/dcmotor-tutorials/motor-calculations
117
3. Apply torque to stall
• Record torque
– Torque-Speed curve
– Torque-Current curve
• Record current
– Torque-Current curve
4. Measure terminal resistance
5. Repeat for additional voltages
Equipment Needed
 Adjustable voltage supply
 Ammeter
• Current probe
 Ohm meter
 Adjustable Torque brake
• Small particle brake
 Non contact tachometer
• strobe
118