CDH Subsystem Design

1
Team B
Explorer
MACE35120 CDR Outline
Version 3.1.1
MACE31520 Design 3 CDR: Team B (Explorer)

2
Presentation Outline
Presenter: Arya Dash MACE31520 Design 3 CDR: Team B (Explorer)
1. Introduction – Arya Dash
1.1 Presentation Outline………………………………………………….2
2. Systems Overview – Arya Dash
2.1 Mission Summary……………………………………………….……..10
2.2 System Requirement Summary………………………………….…..11
2.3 System Level Configuration Trade & Selection……………………12
2.4 System Concept of Operations………………………………...……14
2.5 Physical Layout………………………………………………………..16
2.6 Balloon Compatibility…………………………………………...……..21
3. Sensor Subsystem Design – Arya Dash
3.1 Sensor Subsystem Overview…………………………………………24

3MACE31520 Design 3 CDR: Team B (Explorer)
4. Descent Control Design – Arya Dash
4.1 Descent Control Overview………………………………………….27
4.2 Descent Rate Estimates……………………………………………29
4.3 Safety Case………………………………………………………….30
5. Structural Subsystem Design – Arya Dash
5.1 Structural Subsystem Overview……………………………………32
5.2 Mass Budget…………………………………………………………41
Presenter: Arya Dash

6. Communications & Data Handling Subsystem Design –Siddharth Mundeja
6.1 CDH Overview……………………………………………………….43
6.2 Frequency Selection……………………...………………………...46
6.3 Antenna Trade & Selections ………………………………………47
6.4 Antenna Choice……………..………………………………………49
6.5 Radio Configuration…………………………………………………50
7. Electrical Power Subsystem Design – Siddharth Mundeja
7.1 EPS Overview………………………………………………………..53
7.2 Electrical Block Diagram…………………………………....………58

8. Flight Software Design- Bagrat Rashoyan
8.1 FSW Overview……………………………………………………………….64
8.2 FSW Architecture…………………………………....................................65
8.3 System FSW State Diagram…………………………………….………….68
9. Ground Control System Design – Bagrat Rashoyan
9.1 GCS Overview…………………………………………………….………….70
9.2 GCS Antenna System……………………………………………….……....72
9.3 Antenna Distance Link…………………………………………….…………73
9.4 GCS Software……………………………………………………….………..74
10. System Integration and Test – Stephen Choi
10.1 System Integration and Test Overview……………………….….……….76
12. Management – Stephen Choi
12.1 System Budget…………………………………………………….....……..100
12.2 Conclusions……………………………………………………….…………112

MACE31520 Design 3 CDR: Team B (Explorer) 9
Systems Overview
Arya Dash

10
Mission Summary
Mission Objectives:
 Primary Rationale: System must measure oxygen level: Data can be
used for biological studies of phenomena such as ‘hypoxia’ and
‘cyanosis’ or ‘altitude’ training of athletes
 Auxiliary:
• Safety first!!
• System must satisfy CAA Small Balloon Requirements- All up system
below 2m

System Requirement Summary
11MACE31520 Design 3 CDR: Team B (Explorer)Presenter: Arya Dash
MAJOR ITEMS OF NON-COMPLIANCE:
 Altitude of 7500 m as opposed to 9100 m.
Rationale: Biological studies are of interest in the lower
atmosphere
Benefits:
– Better Ascent performance: reduced ‘Lift’ requirements
– Enhanced Power Consumption: Reduced flight time
– Improved Sensor Performance: Warmer temperatures
– Better T/W Ratio
 Solar Sensor
 Oxygen Sensor
 No Back Up Power Source

12
System Level Configuration Trade &
Selection
MACE31520 Design 3 CDR: Team B (Explorer)Presenter: Arya Dash
• MECHANICAL SUBSYSTEM changes since PDR:
PDR LEVEL:
• Did not conform with the CAA
Small Balloon Requirements
• Unsafe and unreliable: Hook
interfaces
CDR LEVEL:
• Fully conforms with CAA Small
balloon Requirements
• Improved Reliability: Knots and
fewer interface connections

System Level Configuration Trade &
Selection
ELECTRONIC SUBSYSTEM: Selection of Components and Tradeoff
Component PDR
Selection
Major Reasons CDR
Selection
Advantages Trade-off
Microcontroller Arduino
Due
Compatibility
issues with GSM
and Oxygen
Sensors
Link-it one • Integrated GSM
• Oxygen Sensor-
‘Easy to integrate’
Power
GPS ADAFRUIT Poor Compatibility
with Link-it One
MediaTech
MT3332
Highly compatible Placement
Flexibility (Short
wire length)
Arrangement of
temperature
sensor and
altimeter
On side
surfaces
• Cross winds
• Entangling
issues
At the
bottom
protected by
a grove
• No interference
from cross winds
and mainstream
flow
• No tangling issues
Manufacturing

System Concept of Operations
• Launch and Descent
14
Ground Station
Launch,
GSM not
activated
Balloon
Burst
>7500m Parachute
Deployment
GSM
activated,
Payload
Touchdown,
System
recovery.
Sensors record
data, data
stored in SD
card,
Telemetry
packet transmit
data to Ground
Station

Physical Layout
Ascent Mode: Descent Mode:
16Presenter: Arya Dash MACE31520 Design 3 CDR: Team B (Explorer)

Physical Layout
Placement of major components:

21
Balloon Compatibility
MACE31520 Design 3 CDR: Team B (Explorer)Presenter: Arya Dash
Balloon Payload Compatibility Analysis using Non-Dimensional
Studies:
• Key Parameter for aerodynamic performance: T/W Ratio
• Min. T/W requirement is also influenced by required ‘ascent rate’
•
𝑻
𝑾 𝑺𝑳
=
𝜌 𝑆𝐿×𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑏𝑎𝑙𝑙𝑜𝑜𝑛×𝑔
𝑀𝑇𝑂𝑀×𝑔
∝
𝒅 𝟑
𝑴𝑻𝑶𝑾
=′ 𝒇′

Balloon Compatibility
22Presenter: Arya Dash MACE31520 Design 3 CDR: Team B (Explorer)
Physics
• 𝐹𝐵 − 𝑀 × 𝑔 − 𝐹 𝐷 = 𝑀 × 𝑎
• 𝜌 𝐻𝑒 𝑉𝑔 − 𝑀 × 𝑔 − 𝑪 𝒅 x 0.5𝜌 𝑎𝑖𝑟 𝑣2 𝑆
= 𝑀 × 𝑎
• 𝐹𝐵 = 𝜌 𝐻𝑒 𝑉𝑔 = 1.5 × 𝑀𝑇𝑂𝑊
Lift due to
buoyancy
Mass of
(payload+balloon) x g
Drag
𝑭 𝑩 − Force due to buoyancy
M- Total mass
g- Acceleration due to gravity
𝑭 𝑫- Force due to drag
𝝆 𝑯𝒆- Density of Helium
𝝆 𝒂𝒊𝒓 − Density of air
𝑽 − Volume of balloon
v-velocity of system
S- cross section area
of balloon

Sensor Subsystem Design
Arya Dash

24
Sensor Subsystem Overview
GPS
Model No: MT3332
This sensor will be used to
get values for
latitude, longitude
and altitude
Grove Gas Oxygen
Sensor
Model No: O2
This Sensor is used to
calculate main sensor
subsystem requirement,
that is oxygen.
Temperature Sensor
Model No: DS18B20
The System will use this
sensor in order to
measure internal
temperature.
Voltage Sensor
Model :Micro HKPilot Mega
PDB
This Sensor is used to take
voltage
reading for
battery
throughout the flight.
.
Altimeter
Model No: BMP180
Our System uses this sensor
to get values for altitude,
external temperature and
pressure.

Descent Control Design
Arya Dash

Descent Rate Estimates
0
2
4
6
8
10
12
14
16
18
20 70 120
DescentVelocity(m/s)
Diameter (cm)
Descent velocity Vs. Parachute
Diameter
Descent velocity
(m/s)
Ideal
Design
Point
Descent Rate =
2´OverallWeight
airdensity ´ chutedragcoefficient ´ Surfacearea(pD2
/ 4)
• Partial deployment of parachute reduces projected surface area and drag coefficient
due to shape deformation i.e. Cd*S reduces.

Safety Case
0
5
10
15
20
25
30
35
40
45
Kineticenergy(J)
Impact velocity (m/s)
Kinetic energy Vs. Impact velocity
Kinetic energy
Threshold
34J
40J
• According to the the document produced by Monash University,
‘Human injury model for small unmanned aircraft impacts,2013’ kinetic
energy for impact above 40 J is considered dangerous to humans.
• Max attainable kinetic energy is 34 Joules at all measure of undeployed
parachute which is below the threshold kinetic energy of 40 J.

Mechanical Subsystem Design
Arya Dash

Mechanical Subsystem overview
Structure  A newly designed light weight case to house the sensors
and other electrical components
Material  Built from polystyrene foam blocks.
Assembly  The structure is easily assembled from 2 main sections; the
main housing part and the lid.
Interface  The parachute is secured to the payload box with a
mounting plate. The Balloon is connected to the payload by
a cable that goes through a hole at the top of the parachute
and the mounting plates.
32MACE31520 Design 3 CDR: Team B (Explorer)Presenter: Arya Dash

Mass Budget
483 g,
96.6%
17 g,
3.4%
All Up Mass
Measured
Margin
All Up Mass 483 grams
Max. Allowed 500 grams

Communication and Data Handling
(CDH) Subsystem Design
Siddharth Mundeja

CDH Overview
Presenter: Siddharth Mundeja
LinkIt-One [with
integrated GSM & GPS]
3DR
Transceiver
433 Mhz Yagi
Antenna
Connected via
Tx & Rx Pin
Connected via
SMA Connector
using adapter
Connected
via USB
Sends a text
with GPS data
when below
1000m
3DR
Transceiver
Ground Station
Computer [with
GCS Software]
Data From Sensors
• Continuous data
transmission
• 10mW
• 100% duty cycle
• 434.20 MHz
• 25 kHz channel
Ground Control System

CDH Requirements
433.05 434.2 434.79
100% 1 mW; no channeling
100% 10 mW; 25kHz channels
10% 10 mW; no channeling
Ofcom specifications for 433 MHz unlicensed Short Range Devices (SDRs)
Legal Requirements.
Selected
• ~ 800 bits per second
• Low power consumption
• Omnidirectional Transmission
• Low power consumption

Antenna Trade & Selection
Trade Parameters Monopole Antenna Loop Antenna Helical Antenna
Criteria (Weightings %) Score Weighted Score Score Weighted Score Score Weighted Score
Range (50) 9 4.5 6 3 3 1.5
Ease of De-tuning (5) 9 0.45 5 0.25 3 0.15
Gain (5) 8 0.4 5 0.25 5 0.25
Size (10) 9 0.9 4 0.4 2 0.2
Weight (20) 9 1.8 6 1.2 3 0.6
Cost (10) 7 0.7 9 0.9 5 0.5
Total Weighted Score 8.75 6 3.2
Selected Antenna: Monopole Antenna
• Best range
• The whip antenna mitigates a mechanical construction that the helical antenna
and the loop antenna offers.
• With the sacrifice of cost, the best performance is delivered.
Higher is better

Antenna Choice
• Quarter wave Monopole Antenna
• Vertically Polarised
• 2dBi gain
Radiation Pattern: Doughnut Shaped
3DR Radio with
Antenna
Remote module Antenna

Radio Configuration
• 3DR Digital
telemetry radio
• Custom data
packet
• Radio configuration
(NETID, baud, etc.)
set via “Mission
Planner” GUI”
• Configuring Net ID
for pairing and
ensuring not
receiving alien data
• Setting min max
frequency for spectrum
hoping(within license
free zone)

Electrical Power Subsystem (EPS)
Design
Siddharth Mundeja

EPS Overview
Made by: Ola Majasan
Component Diagram
• Battery: 3 x Varta (1x1.2V) 500mAh NiMH
Rechargeable Coin Cell Battery
Microcontroller
• Acts as a node.
• Distributes current
to sensors &
Radio
Micro HKPilot
Mega PDB
• Measures the
Voltage across the
battery. Value
reported to GCS.
Sensor and
Radio
• Sensors 3.3 V
• Radio 5.0 V
Main Supply Battery
(3.6 V)

58
Electrical Block Diagram
Battery
Radio Module, Supply with 5 V
Altimeter, Supply with 3.3V
Oxygen Sensor, Supply with 5V
Grey Arrows :
These indicate
the direction of
flow of
information
throughout the
circuit.
Blue Arrows :
These indicate
the direction
of flow of
power
throughout the
circuit.
Temperature Sensor, Supply with 3.3V
Current/Voltage Sensor
GPS antenna, Supply with 3.3V
Made by: Ola Majasan

Flight Software (FSW) Design
Bagrat Rashoyan

FSW Overview
Initialising Sensors
(at start/reboot)
Loop: Data
acquisition
(2 second sleep)
Transmit Store
Data Flow• Programming language – C/C++
with wrappers
• MCU Operating System – None
• Programming Environment –
Arduino
• Using libraries supplied by sensor
vendors
• Data stored on SD card
• Consumes an average of 115
mAh (90 when at sleep, 140
when transmitting) available 500
mAh [Voltmeter tested]
Presenter: Bagrat Rashoyan

FSW Architecture
65MACE31520 Design 3 CDR: Team B (Explorer)Presenter: Name goes here
ARCHITECTURE
SENSORS
MCU
DATA LOGGING
RADIO
DATA RECEIVED
DATA TRANSMIT
GSM MODULE
Declare variables
Setup()
{
Initialize sensors
}
Loop()
{
Get Senor Data
Transmit Store
Sleep for 2 seconds
}
"#,teamID,packetNo,packetTime,lat,lon,alt,satNo,baroH,press,extTemp,intTemp,vol,MD5"

Ground Control System (GCS) Design
Bagrat Rashoyan

70
GCS Overview
LinkIt-One [with
integrated GSM & GPS]
3DR
Transceiver
433 Mhz Yagi
Antenna
Connected via
Tx & Rx Pin
Connected via
SMA Connector
using adapter
Connected
via USB
Sends a text
with GPS data
when below
1000m
3DR
Transceiver
Ground Station
Computer [with
GCS Software]
Data From Sensors
• Continuous data
transmission
• 10mW
• 100% duty cycle
• 434.40 MHz
• 25 kHz channel
Ground Control System
Presenter: Bagrat Rashoyan MACE31520 Design 3 CDR: Team B (Explorer)

GCS Antenna System
Presenter: Kelvin Kan 72
Radius =1
meter
Antenna in clear line
of Sight of the
remote module
manually adjusted to
pint towards the
module continuously.
Antenna 1 m clear of any
objects to prevent signal
bouncing.
Lightening arrestor
to protect the system
and operator
2m
Masted 2m above
the ground on a non-
conducting mast
Antenna set at the highest
possible position at the
launch site.

Antenna Distance Link
The following equation gives a theoretical range of the yagi antenna communicating with the system monopole
antenna.
R = Transmission Distance in km
f = Frequency
Pt= is the Tx power for the device that will be transmitting data
Gt= is the Tx antenna gain, the antenna gain of the antenna on the transmitting device.
Pr= is the Rx sensitivity of the device receiving data.
Gr= is the Rx antenna gain, the antenna gain of the antenna on the receiving device.
c = speed of light
Tx power = 10 dBm
Tx antenna gain = 3.3 dBi
Rx sensitivity = -118 dBm
Rx antenna gain = 13 dBi
Frequency = 434.2 MHz
The distance link is estimated to be 20.8 km
𝑹 =
𝑷 𝑻 𝑮 𝑻 𝑮 𝑹 𝒄 𝟐
𝑷 𝑹
×
𝟏
𝟒𝝅𝒇

GCS Software
• Custom GUI software designed Using Qt Creator (C++)
• Data received from 3DR radio through USB com port, parsed and
displayed on relevant LCDs
MACE31520 Design 3 CDR: Team B (Explorer) 74Presenter: Bagrat Rashoyan

System Integration and Test
Stephen Choi

Overview
Presenter: Stephen Choi
Test Title Purpose Test Set up Test
Inputs
Successful
criteria
Predicted
Result and
basis
Recorded
Result
Actions Required Order
Mechanical Subsystem
Payload box
drop test
Survivability
of structure
and
components
are protected
during
impact.
Container with
all components
mounted in the
container and
suspended
from high ledge
Release
of
container
• Accelerating
force inside the
container are
not too large
• Visual
inspection of
acceptable
damage
All components
remain in
working
condition after
impact.
Structure
remain
intact and
electric
components
remained
functional
• Additional
Shock
absorbing
padding
1
Parachute
deployment
test
Successful
deployment
of decent
control
mechanism
during
freefall
Parachute and
container
assembled in
decent
configuration.
Release
of
container
with
parachute
• Successful
deployment of
parachute
Successful
deployment of
parachute
N/A • Alternate nylon
cables and pre-
prepped loops
• Pre-
manufactured
parachute
3
Knot
Connections
Ensure Knots
do not come
undone or
cut during
operation
Using a force
meter pull one
end of the
cable and
secure the
other end using
knot.
Increase
force on
cables
• Retained
integrity of
knots
Knots will be
intact
N/A 2

Overview
Test Title Purpose Test Set up Test Inputs Successful
criteria
Predicted Result
and basis
Recorded
Result
Actions
Required
Order
Electrical Subsystem
Electrical
Connection
test
Integrity of
electrical
connections
after soldering
and
placement
Electrical
components
soldered
Multimeter
testing
• Voltage across
components
• No noise
Voltage and
current readings
shows a closed
circuit
All electrical
components
were
connected
4
Battery
Endurance
Test
Show the
available run
time of the
power pack
Connect all
electrical
components
and leave the
system to
operate for a
specified
period.
Timer • Can at least
power system
for four hours
System can
operate for over
four hours
Total Run-time:
6 hours
5
Cold
Temperature
Tests
Effects of
temperature
on the
electrical
components
Payload box
with electrical
components
connected
Cold box to
create
environment
• Electronics still
functional and
report sensible
values
Electronics still
functions as
intended
Tested for
-20 degrees
6

Overview
Test Title Purpose Test Set up Test Inputs Successful
criteria
Predicted Result
and basis
Recorded
Result
Actions
Required
Order
CDH Subsystem
Radio
Reliability
Test in Urban
Environment
Radio and
Antenna
communic-
ation
reliability
GCS and
completed
payload box
set at >1km
apart
GCS and
CDH
software
Continues to
communicate
and receive
data >1km
Successful
communication
with some
interruptions
Successful
communi-
cation with
some
interference
7
Data Storage Test all
required
data can
be reliably
stored on
microSD
card
Insert
microSD into
LinkIt One
and start
sensor
recordings
Non-corrupt
data could
be retrieved
from
microSD
Useful data
could be
obtained
No issues
encountered
8

Mission Operations & Analysis
Stephen Choi

Management
Stephen Choi

100
System Budget – Other Costs
Components Model Quantity Cost (£) Price Definition
Battery Varta 3.6V NiMH
coin cell
1 4.90 Actual
Microprocessor Arduino Due 1 34.27 Actual
Temperature sensor DS18B20 1 3.93 Actual
Mounting plate 4MP1212 2 16.14 Actual
Parachute - - 1 3.00 Budgeted
Polystyrene Box - - 2 5.00 Budgeted
Subtotal 67.24
Prototype & Testing
Labour
Components Model Quantity Cost (£) Price Definition
Human labour Undergraduate 1200 hours 18000 Approximation
Subtotal 18000

101
System Budget – Total Cost
Budget Type Sub-total Cost (£)
Sensor Subsystem 83.88
Electrical Power Subsystem 27.13
Communications and Data Handling Subsystem 140.41
Structural 30.50
Ground Control System 172.36
Prototype & Testing 67.24
Overall Total 521.52

Conclusions
Major accomplishments:
• Re-designed system to comply with CAA small balloon requirement
• Reduced weight to below 500g
• Sensors are working
• Communications are working
• Mitigation by producing our own payload box and parachute
• Launch day schedule and operations manual
• Budget estimated
Major unfinished work:
• Oxygen sensors need to be purchased
• Solar panel needs to be purchased
• Oxygen and solar flux sensors need to be programmed and calibrated
• Some tests to be carried out
Why we are ready to proceed to flight readiness review:
• System is designed and built, with tests done showing a good performance
and compliance to most requirements. Non-compliances are explained.

CDH Subsystem Design

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