P09141
Satellite Thermal Heater Controller
Anthony Berwin
Scott Rioux
Greg Pawlowski
Sarmad Abedin
John Scipione
Mechanical Engineer
Industrial Engineer
Electrical Engineer
Electrical Engineer
Electrical Engineer
Sponsors: ITT Corporation & D3 Engineering
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Project Overview
Description: Thermal Controller for Satellite Operations
Market: Space Systems Division of ITT
Key Deliverables:
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4.
5.
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Power Efficiency
Mass
Performance
Communications
Cost
KGCOE Multidisciplinary Senior Design
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Project Concept
Enclosure
Interface Board
Communications
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Programming
Protocol
GUI
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Project Architecture
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Milestones
MSD 1
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January 16, 2009 – System Level Design Review
February 13, 2009 – Detailed Design Review
February 20, 2009 – Project Presentation
MSD II
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March 9, 2009 – Begin Programming DSP & GUI
March 13, 2009 – Materials Ordered
April 3, 2009 – Testable Prototype
May 1, 2009 – Testing & Debugging Completed
May 20, 2009 – Final Review
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Budget/BOM
Original Budget: $1740 – $2070
Current Estimated Budget: $1703.44
All components available
Shipping time 1-2 weeks
Waiting on DSP’s
Machine time for Enclosure 2 weeks, could outsource for
faster turn around time
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Enclosure
Needs & Specifications
Size (Minimize)
Mass (<0.3 lb)
Mounting (Enclosure, PCB, Connectors*)
Vibrations (23.1 G’s Random Vibration)
Thermal (-40°C to +55°C)
Vacuum Environment
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Ventilation* (<1 psi/s)
Outgassing
Torque on Screws*
EMI Leakage* (<100 kHz)
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Enclosure
Assembly Model
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Enclosure
Assembly Model: Exploded View
Top
PCB
Side A
Side B
Base
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Enclosure
Specifications Met
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Total Size: 2.875” x 2.875” x 1.0625”
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Total Mass: 0.244 lb
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18% below the 0.3 lb limit
Enclosure Mounting:
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Size of the PCB with the Connectors: 2.61” x 2.25” x 0.5625”
Flat Plate & Cylinder (R>18”)
PCB Mounting:
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Four (4) Screws & Aluminum Heat Sink Contacts
KGCOE Multidisciplinary Senior Design
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Enclosure
Specifications Not Met
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Partially Met
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Connector Mounting
Vacuum Environment
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Ventilation
Outgassing
Not Met
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Torque on Screws
EMI Leakage
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Enclosure
Risk Assessment: Risks
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Acquiring PCB Specifications
Acquiring Connector Specifications
Acquiring Equipment (PCB & Connectors)
Stress on the Screws
Enclosure Strength
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Enclosure
Risk Assessment: Actions
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Acquiring PCB Specifications
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Acquiring Connector Specifications
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Failure during vibrations testing
Enclosure Strength
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Delay in the assembly of the enclosure
Stress on the Screws
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Delay in the redesign of the enclosure or causing a redesign much
later in MSD II
Acquiring Equipment (PCB & Connectors)
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Delay in the redesign of the enclosure or causing a redesign much
later in MSD II
Failure during vibrations testing
KGCOE Multidisciplinary Senior Design
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Enclosure
Risk Assessment: Mitigation
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Acquiring PCB Specifications
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Acquiring Connector Specifications
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Increase screw size
Use temporary thread-locking adhesive
Enclosure Strength
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Work with the customer to receive the equipment
Stress on the Screws
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Work with the customer to clarify specifications
Acquiring Equipment (PCB & Connectors)
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Work with the customer to clarify specifications
Change material to aircraft aluminum
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Enclosure
Action Items
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Redesign of the enclosure
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Increase screw size
Change material to aircraft aluminum
Final PCB Specifications
Complete
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Part Models
Assembly Model
Part Drawings
Parts List
BOM
Enclosure Specifications
Thermal and Vibrations Simulations
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Interface Board
Overview
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Purpose
Master and slave communications over a power bus
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Isolation from 28VDC Power Bus
Transmit/Receive Switching
Transmit/Receive Signal Conditioning
Voltage conversion
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KGCOE Multidisciplinary Senior Design
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Project Review
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Interface Board
Block Diagram
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KGCOE Multidisciplinary Senior Design
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Interface Board
DC Isolation
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Need
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There are no dedicated communication lines
RF signals will interfere with other satellite operations
Power bus already available
Isolation of communications signal from DC power bus
to protect electronics
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KGCOE Multidisciplinary Senior Design
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Interface Board
Switching
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Need
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Transmitting the communications signal
Receiving the communications signal
It is necessary to switch between the two modes of
operation
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Interface Board
Voltage Converter
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Need
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Negative supply voltage to operate electronics on interface
board
Will take a input voltage and output the same negative voltage
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Interface Board
Receive Signal Conditioning
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Need
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Filter out noise from communications signal
Amplify communications signal for ADC
Offset communications signal to positive voltage for ADC
KGCOE Multidisciplinary Senior Design
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Interface Board
Transmit Signal Conditioning
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Need
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Filter out high frequency harmonics from communications
signal
Generate the communications signal from pulse width
modulator
KGCOE Multidisciplinary Senior Design
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Interface Board
Risk Assessment: Risks
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Low frequency noise not filtered out
Transient noise not accounted for
Power consumption of IC’s
Design of filters
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KGCOE Multidisciplinary Senior Design
Project Review
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Interface Board
Risk Assessment: Actions
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Low frequency noise not filtered out
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Transient noise not accounted for
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Communication errors, or signal not received
Power consumption of IC’s
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Communication errors, or signal not received
Use to much power, other systems will not work
Design of filters
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Filters do not function properly
KGCOE Multidisciplinary Senior Design
Project Review
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Interface Board
Risk Assessment: Mitigation
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Low frequency noise not filtered out
Transient noise not accounted for
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Power consumption of IC’s
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Write better demodulation algorithm, use more hardware
demodulation techniques
Switch to low power modes when not in use
Design of filters
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Do more research on filter design, or seek help in filter design
from experienced engineers
KGCOE Multidisciplinary Senior Design
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Interface Board
Action Items
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Finalize parts for interface board
Build prototype and test
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KGCOE Multidisciplinary Senior Design
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Programming
Architecture
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KGCOE Multidisciplinary Senior Design
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Programming
Needs
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PC communicate with Master DSP over serial line.
Master DSP communicate with each slave over 28V
heater power bus. No dedicated lines are available.
Modulation and demodulation is needed.
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KGCOE Multidisciplinary Senior Design
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Programming
DSP
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The bits of the protocol must be generated, stored, and
interpreted.
A sine wave must be generated from binary using
PWM/ DAC.
Signal demodulated back into binary using ADC.
Communication with the PC GUI over SCI.
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KGCOE Multidisciplinary Senior Design
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Programming
How are we going to do it?
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Code Composer will be used to Program the DSP in the
C programming language.
The ADC, PWM, UART, and SCI modules are all utilized.
The program is stored in flash memory. The protocol bits
are stored in RAM memory.
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KGCOE Multidisciplinary Senior Design
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Programming
Risks
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Acquiring the DSP. Programming will be difficult to begin
without the DSP.
Learning the Code Composer Environment. Code
Composer comes with the DSP.
Programming each of the DSP elements that need to be
programmed including PWM, ADC, the protocol, serial
communication.
Finding code examples.
Writing and testing the code.
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KGCOE Multidisciplinary Senior Design
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Protocol
Communications
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SCI protocol (LabView to Master)
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3 Pins - Transmit, Receive, Ground
4 Transmissions - 12 Bit Each
1 Start Bit
8 Data Bits(Slave ID, Temp. Bits, Ctrl Bits, etc)
1 Parity Bit (Eliminates Checksum)
2 End Bits
KGCOE Multidisciplinary Senior Design
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Protocol
Communications
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UART Protocol (Master to Slave)
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Bi-directional, half-duplex (only slave or master can talk at one
time)
Bit by bit transmission
Different frequencies for ‘1’ and ‘0’ (in order to meet the 20
ms spec, min. freq = 5kHz; 200 us/bit)
‘0’ frequency = 7.5 kHz
‘1’ frequency = 17.5 kHz
No activity on line = noise only
KGCOE Multidisciplinary Senior Design
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Protocol
Communications
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40 Bit Transmission
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2 Start Bits
6 Checksum Bits
12 Data (temp) Bits
6 Control Bits (read/set, temp/htr state, etc.)
5 Telemetry Pins
8 Bits for Slave ID
1 End Bit
KGCOE Multidisciplinary Senior Design
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Protocol
Risk Assessment: Risks
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Transfer rate too slow
Not enough bits to account for other details
Bit/error rate too high
KGCOE Multidisciplinary Senior Design
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Protocol
Risk Assessment: Actions
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Transfer rate too slow
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Not enough bits to account for other details
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Not all data will be represented and can lead to a lack of outputting
required data
Bit/error rate too high
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Timing issues between the receiver and transmitter leading to wrong
messages being transferred
The wrong message to be transmitted and the appropriate output will
not be achieved
KGCOE Multidisciplinary Senior Design
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Protocol
Risk Assessment: Mitigation
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Transfer rate too slow
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Not enough bits to account for other details
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Bits will be added to protocol and the appropriate transfer rates will
be calculated.
Bit/error rate too high
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Can decrease the time it takes to send a bit
Reduction in signal to noise ratio must be changed or an increase in
the bandwidth.
KGCOE Multidisciplinary Senior Design
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Protocol
Action Items
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Acquiring EzDSP
Program the DSP using the FSM flowchart in order to
communicate from GUI to Master and Master to Slave
Work with the interface and PWM and ADC
programming to ensure proper communication
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KGCOE Multidisciplinary Senior Design
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Graphical User Interface
Overview
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System required a simple computer interface
Needed to be able to control DSP’s and send commands
Easily readable and intuitive
Be able to control multiple parameters
Be able to communicate via Serial Port
Able to control 256 DSP’s
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KGCOE Multidisciplinary Senior Design
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Graphical User Interface
Risk Assessment: Risks
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Time Constraints
Connectivity Problems
Testing, Replication Table
Loopback Testing
Programming Constraints
Final Implementation Requires Working DSP Programming
KGCOE Multidisciplinary Senior Design
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Graphical User Interface
Risk Assessment: Actions
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Time Constraints
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Connectivity Problems
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Trouble Programming in LabView
Final Implementation Requires Working DSP Programming
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Cannot Initiate Link over Serial
Programming Constraints
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Testing will be more difficult
Loopback Testing
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Will not complete GUI to Master Link
Testing, Replication Table
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GUI will not get completed
Final Product will not be completed in time
KGCOE Multidisciplinary Senior Design
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Graphical User Interface
Risk Assessment: Mitigation
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Distribution of tasks
Research and Examples
Faculty Help
Purchasing own DSP board
Discussion about final deliverables, removing
requirements
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KGCOE Multidisciplinary Senior Design
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Graphical User Interface
Concept Selection
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There were 5 candidates for GUI creation
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GUI have 5 parameters in which we rated it on
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Visual Basic
LabView
MATLAB
Java
C++
Ease of Use
Safety
Programmability
Customer Preference
Familiarity
A concept selection and screening methods were both used to
help determine which method would be best
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KGCOE Multidisciplinary Senior Design
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Graphical User Interface
Concept Selection
GUI
A
B
Conce pts
C
VB
Labvie w
C++
D
E
Java
M atLab
Weigh Rating Weight Rating Weight Rating Weight Rating Weight Rating Weight
Se le ction Crite ria
ed
Score
t
ed
Score
ed
Score
ed
Score
ed
Score
Ease of Programmability
25%
3
0.75
3
0.75
2
0.5
2
0.5
3
0.75
Safety
25%
3
0.75
3
0.75
1
0.25
3
0.75
3
0.75
Familiarity
25%
3
0.75
4
1
1
0.25
1
0.25
3
0.75
Cust Preference
15%
3
0.45
2
0.3
2
0.3
2
0.3
3
0.45
Ease of Use
10%
2
0.2
4
0.4
3
0.3
3
0.3
1
0.1
Total Score
2.90
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3.20
1.60
2.10
2.80
Rank
Continue?
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no
winner
KGCOE Multidisciplinary Senior Design
no
no
Project Review
no
R•I•T
Graphical User Interface
LabView
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LabView was chosen mainly because of its ease of use,
and familiarity between the team members
LabView allows us to easily create a nice GUI with
multiple features
LabView is also scalable, allows us to add or change
features easily without rewriting all of the programming
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KGCOE Multidisciplinary Senior Design
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Graphical User Interface
Required Features
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LabView needs to have visual indicators
Communicate over serial port (RS232)
Ability to see system status
Ability to set and change set points
Ability to chose between 255 slaves to upload
temperature
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KGCOE Multidisciplinary Senior Design
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Graphical User Interface
Front Panel
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KGCOE Multidisciplinary Senior Design
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Graphical User Interface
Communication
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LabView will communicate with the Master via RS232
ASCII
Four 12bit transmissions to communicate all data
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KGCOE Multidisciplinary Senior Design
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Graphical User Interface
Action Items
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Complete Replication Table
Replication Table Parameters
Complete Communication Development from GUI to
Master
Start Loop-Back Testing
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KGCOE Multidisciplinary Senior Design
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