p09141 satellite thermal heater controller

P09141Satellite Thermal Heater Controller

Anthony Berwin Mechanical Engineer

Scott Rioux Industrial Engineer Greg Pawlowski Electrical Engineer Sarmad Abedin Electrical EngineerJohn Scipione Electrical

Engineer

Sponsors: ITT Corporation & D3 Engineering

1 Project Review R•I•TKGCOE Multidisciplinary Senior Design

Project Overview Description: Thermal Controller for Satellite

Operations Market: Space Systems Division of ITT Key Deliverables:

1. Power Efficiency 2. Mass 3. Performance 4. Communications 5. Cost


Project Concept Enclosure Interface Board Communications

Programming Protocol

GUI


Project Architecture


Milestones MSD 1

January 16, 2009 – System Level Design Review February 13, 2009 – Detailed Design Review February 20, 2009 – Project Presentation

MSD II 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

Project Review R•I•TKGCOE Multidisciplinary Senior Design

5

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


6

EnclosureNeeds & 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

Ventilation* (<1 psi/s) Outgassing

Torque on Screws* EMI Leakage* (<100 kHz)


EnclosureAssembly Model


EnclosureAssembly Model: Exploded View


Top

Side B

Side A

PCB

Base

EnclosureSpecifications Met Total Size: 2.875” x 2.875” x 1.0625”

Size of the PCB with the Connectors: 2.61” x 2.25” x 0.5625”

Total Mass: 0.244 lb 18% below the 0.3 lb limit

Enclosure Mounting: Flat Plate & Cylinder (R>18”)

PCB Mounting: Four (4) Screws & Aluminum Heat Sink Contacts


EnclosureSpecifications Not Met Partially Met

Connector Mounting Vacuum Environment

Ventilation Outgassing

Not Met Torque on Screws EMI Leakage


EnclosureRisk Assessment: Risks

Acquiring PCB Specifications Acquiring Connector Specifications Acquiring Equipment (PCB & Connectors) Stress on the Screws Enclosure Strength


EnclosureRisk Assessment: Actions

Acquiring PCB Specifications Delay in the redesign of the enclosure or causing a

redesign much later in MSD II Acquiring Connector Specifications

Delay in the redesign of the enclosure or causing a redesign much later in MSD II

Acquiring Equipment (PCB & Connectors) Delay in the assembly of the enclosure

Stress on the Screws Failure during vibrations testing

Enclosure Strength Failure during vibrations testing


EnclosureRisk Assessment: Mitigation

Acquiring PCB Specifications Work with the customer to clarify specifications

Acquiring Connector Specifications Work with the customer to clarify specifications

Acquiring Equipment (PCB & Connectors) Work with the customer to receive the equipment

Stress on the Screws Increase screw size Use temporary thread-locking adhesive

Enclosure Strength Change material to aircraft aluminum


EnclosureAction Items Redesign of the enclosure

Increase screw size Change material to aircraft aluminum Final PCB Specifications Complete

Part Models Assembly Model Part Drawings Parts List BOM Enclosure Specifications Thermal and Vibrations Simulations


Interface BoardOverview Purpose Master and slave communications over a

power bus Isolation from 28VDC Power Bus Transmit/Receive Switching Transmit/Receive Signal Conditioning Voltage conversion


Interface Board Block Diagram


Interface Board DC Isolation


Need 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

Interface Board Switching


Need Transmitting the communications signal Receiving the communications signal

It is necessary to switch between the two modes of operation

Interface Board Voltage Converter


Need Negative supply voltage to operate electronics on

interface board Will take a input voltage and output the same

negative voltage

Interface Board Receive Signal Conditioning


Need Filter out noise from communications signal Amplify communications signal for ADC Offset communications signal to positive voltage

for ADC

Interface Board Transmit Signal Conditioning


Need Filter out high frequency harmonics from

communications signal Generate the communications signal from pulse

width modulator

Interface Board Risk Assessment: Risks


Low frequency noise not filtered out Transient noise not accounted for Power consumption of IC’s Design of filters

Interface Board Risk Assessment: Actions


Low frequency noise not filtered out Communication errors, or signal not received

Transient noise not accounted for Communication errors, or signal not received

Power consumption of IC’s Use to much power, other systems will not work

Design of filters Filters do not function properly

Interface Board Risk Assessment: Mitigation


Low frequency noise not filtered out Transient noise not accounted for

Write better demodulation algorithm, use more hardware demodulation techniques

Power consumption of IC’s Switch to low power modes when not in use

Design of filters Do more research on filter design, or seek help in

filter design from experienced engineers

Interface Board Action Items


Finalize parts for interface board Build prototype and test

Programming Architecture


Programming Needs 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.


Programming DSP 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.


Programming How are we going to do it?


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.

Programming Risks 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.


ProtocolCommunications SCI protocol (LabView to Master)

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


ProtocolCommunications UART Protocol (Master to Slave)

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


ProtocolCommunications 40 Bit Transmission

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


ProtocolRisk Assessment: Risks

Transfer rate too slow Not enough bits to account for other details Bit/error rate too high


ProtocolRisk Assessment: Actions

Transfer rate too slow Timing issues between the receiver and transmitter

leading to wrong messages being transferred Not enough bits to account for other details

Not all data will be represented and can lead to a lack of outputting required data

Bit/error rate too high The wrong message to be transmitted and the

appropriate output will not be achieved


ProtocolRisk Assessment: Mitigation

Transfer rate too slow Can decrease the time it takes to send a bit

Not enough bits to account for other details Bits will be added to protocol and the appropriate

transfer rates will be calculated. Bit/error rate too high

Reduction in signal to noise ratio must be changed or an increase in the bandwidth.


ProtocolAction Items 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


Graphical User InterfaceOverview 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


39

Graphical User InterfaceRisk Assessment: Risks

Time Constraints Connectivity Problems Testing, Replication Table Loopback Testing Programming Constraints Final Implementation Requires Working DSP

Programming


40

Graphical User InterfaceRisk Assessment: Actions

Time Constraints GUI will not get completed

Connectivity Problems Will not complete GUI to Master Link

Testing, Replication Table Testing will be more difficult

Loopback Testing Cannot Initiate Link over Serial

Programming Constraints Trouble Programming in LabView

Final Implementation Requires Working DSP Programming Final Product will not be completed in time


41

Graphical User InterfaceRisk Assessment: Mitigation Distribution of tasks Research and Examples Faculty Help Purchasing own DSP board Discussion about final deliverables, removing

requirements


42

Graphical User InterfaceConcept Selection There were 5 candidates for GUI creation

Visual Basic LabView MATLAB Java C++

GUI have 5 parameters in which we rated it on 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


43

Graphical User InterfaceConcept Selection

ConceptsA B C D E

GUI VB C++ Java MatLabSelection Criteria Weigh

t

Rating Weighted

Score

Rating Weighted

Score

Rating Weighted

Score

Rating Weighted

Score

Rating Weighted

ScoreEase of Programmability 25% 3 0.75 3 0.75 2 0.5 2 0.5 3 0.75Safety 25% 3 0.75 3 0.75 1 0.25 3 0.75 3 0.75Familiarity 25% 3 0.75 4 1 1 0.25 1 0.25 3 0.75Cust Preference 15% 3 0.45 2 0.3 2 0.3 2 0.3 3 0.45Ease of Use 10% 2 0.2 4 0.4 3 0.3 3 0.3 1 0.1

0 0 0 0 00 0 0 0 00 0 0 0 00 0 0 0 00 0 0 0 0

Total ScoreRank

Continue? no winner no no no

2.90 3.20

Labview

2.10 2.801.60


44

Graphical User InterfaceLabView 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


45

Graphical User InterfaceRequired Features 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


46

Graphical User InterfaceFront Panel


Graphical User InterfaceCommunication


LabView will communicate with the Master via RS232

ASCII Four 12bit transmissions to communicate all

data

Graphical User InterfaceAction Items


Complete Replication Table Replication Table Parameters Complete Communication Development from

GUI to Master Start Loop-Back Testing

p09141 satellite thermal heater controller

Documents