P09141 Satellite Thermal Heater Controller Anthony Berwin Mechanical Engineer Scott Rioux Industrial Engineer Greg Pawlowski Electrical Engineer Sarmad Abedin Electrical Engineer John Scipione Electrical Engineer Sponsors: ITT Corporation & D3 Engineering 1Project Review RITKGCOE Multidisciplinary Senior Design

Milestones  MSD 1  January 16, 2009 – System Level Design Review  February 13, 2009 – Detailed Design Review  February 20, 2009 – MSD I Review Presentation  MSD II  May 2, 2009 – Poster Session I  May 15, 2009 – Technical Paper  May 15, 2009 – MSD II Review Presentation  May 19, 2009 – Demonstration  May 22, 2009 – Poster Session II Project Review RITKGCOE Multidisciplinary Senior Design 2

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 3Project Review RITKGCOE Multidisciplinary Senior Design

Project Sections  Enclosure  Graphical User Interface  PC to Master Communication  Master to Slaves Communication 4Project Review RITKGCOE Multidisciplinary Senior Design

Enclosure Needs & Specifications  Material (6061 Aluminum Alloy, 316 Stainless Steel)  Size (Minimize)  Mass (<0.450 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) 5Project Review RITKGCOE Multidisciplinary Senior Design

Enclosure Assembly Model 6Project Review RITKGCOE Multidisciplinary Senior Design

Enclosure Assembly Model: Exploded View 7Project Review RITKGCOE Multidisciplinary Senior Design

Enclosure Specifications Met  Material:  6061-T6511 Aluminum Alloy (Top & Bottom Parts)  Type 316 Stainless Steel (Machine Screws)  Total Size: 3.50” x 2.875” x 1.00”  Size of the PCB with the Accelerometer: 3.0” x 2.0” x 0.563”  Total Mass: lb  4.06% below the lb limit  Enclosure Mounting:  Flat Plate & Cylinder (R > 18”), d max < 3/32”  PCB Mounting:  Five (5) 2-56 Machine Screws 8Project Review RITKGCOE Multidisciplinary Senior Design

Enclosure Specifications Not Met  Partially Met  Connector Mounting  Vacuum Environment  Ventilation  Outgassing  Not Met  Torque on Screws  EMI Leakage 9Project Review RITKGCOE Multidisciplinary Senior Design

Enclosure Design Analysis: Strengths & Weaknesses  Strengths  Scalable to Varying Sizes of the PCB  Easy to Machine  Two (2) Pieces  Low Cost of Materials  Easily Assembled  Weaknesses  Excess Weight  1/8” thickness for machining  Connector Mounting  Mating connectors are not secured 10Project Review RITKGCOE Multidisciplinary Senior Design

Enclosure Design Analysis: Potential Improvements  Decrease Weight  Decrease the thickness to 1/16” or 3/32” from 1/8”  Change the strew type from 4-40 to 2-56  Connector Mounting  Add component to secure mating connectors  Account for Ventilation  Add ventilation slot  Account for EMI Leakage  Minimum thickness  Account for the Torque on Screws  Verify minimum screw type 11Project Review RITKGCOE Multidisciplinary Senior Design

Graphical User Interface Overview  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 Project Review RITKGCOE Multidisciplinary Senior Design 12

Graphical User Interface LabView  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 Project Review RITKGCOE Multidisciplinary Senior Design 13

Graphical User Interface Specifications  Communicate over serial port (RS232)  Ability to see heater state status and telemetry information  Ability to set and change temperature set points  Ability to chose between 255 slaves to upload temperature Project Review RITKGCOE Multidisciplinary Senior Design 14

Graphical User Interface Programming  Programming started with communication over serial  Building blocks for the project were added on top  Each requirement or functionality that was needed was researched then implemented  Problems that arose were quickly dealt with by research Project Review RITKGCOE Multidisciplinary Senior Design15

Graphical User Interface Programming/Development  Message Creation  Messages were created using loops and numerical to string identifiers.  Labview sends out 24 bits, which gets converted to 3 ASCII characters  Message Contents  Message contains all elements needed to communicate with DSP  Slave ID gets transmitted first, control bits 2 nd, and temperature last  The control bits relate to controls on the front panel that allow the user to manipulate the message and retrieve different data Project Review RITKGCOE Multidisciplinary Senior Design16

Graphical User Interface Programming/Development Project Review RITKGCOE Multidisciplinary Senior Design17  Structures  All Labview programming is grouped within loop structures so data and set points can be updated continuously.  Different structures exist for different functionality.  Initialization of slaves, Continuous message sending, Message building  Some key building blocks are : Steinhart-Hart function, Binary number creation, Voltage readings, Serial port open/close

Graphical User Interface Front Panel 18Project Review RITKGCOE Multidisciplinary Senior Design

Graphical User Interface Specs Met/ Not Met 19Project Review RITKGCOE Multidisciplinary Senior Design  Met  Ability to communicate over serial  Ability to send and receive data from DSP  Ability to control temperature and control bits  Has visual indicators  Not Met  Simplicity of GUI

Graphical User Interface Strengths/Weaknesses 20Project Review RITKGCOE Multidisciplinary Senior Design  Strengths  Very Powerful  Has lots of Error Checking and Debugging  Easily Understood  Weaknesses  Computer resource intensive  Complex changes take time

Graphical User Interface Potential Improvements 21Project Review RITKGCOE Multidisciplinary Senior Design  Improvements  Make front panel more visually appealing  Revise and improve looping  Create simpler ways to do programming

Communications Overview 22Project Review RITKGCOE Multidisciplinary Senior Design

PC to Master Communications Overview  Communication between Master DSP and Graphical User Interface (GUI) must occur over SCI  Protocol must be able to incorporate the many needs of the User  Master must generate a new message for the ‘slave’ DSPs after receiving a message from GUI.  After receiving a response from the appropriate slave, the master DSP must generate a new message to send back to GUI 23Project Review RITKGCOE Multidisciplinary Senior Design

PC to Master Communications SCI Protocol  SCI protocol (LabView to Master)  3 Pins - Transmit, Receive, Ground  3 Transmissions - 12 Bit Each  1 Start Bit  8 Data Bits(Slave ID, Temp. Bits, and Ctrl Bits)  1 Parity Bit (Eliminates Checksum)  2 End Bits 24Project Review RITKGCOE Multidisciplinary Senior Design

PC to Master Communications Objectives  The SCI message was received and transmitted back using an interrupt routine using the RX buffer and TX buffer in the EzDSP.  A circular buffer routine was utilized to prevent overriding incoming messages from LabView.  The Master to DSP message also included five telemetry pins, mainly used for debugging.  Messages from LabView were appended to include start bits, transmit/receive bit, error bit, and check sum bits. 25Project Review RITKGCOE Multidisciplinary Senior Design

PC to Master Communications Specifications Met/Unmet  Specs Met  Ability to communicate from/to GUI via serial port  Ability to communicate to/from the slaves and to retrieve information from the HHC  The use of an interrupt service routine for transmitting and receiving  Unmet Specs  20ms total communication time 26Project Review RITKGCOE Multidisciplinary Senior Design

PC to Master Communications Strengths and Weaknesses  Strengths  The user can continuously ask the master to report data from any particular slave and see it updating in real time.  The protocol is reliably able to handle all of the user’s needs.  Weaknesses  Cannot guarantee a complete and/or correct message is sent all the time because of SCI  TCP for example, has the ability to automatically resend messages to ensure proper transmission to the receiver. 27Project Review RITKGCOE Multidisciplinary Senior Design

PC to Master Communications Potential Improvements  A more reliable protocol instead of SCI  In order to better handle errors and ensure proper transmission 28Project Review RITKGCOE Multidisciplinary Senior Design

Master to Slave Communication Needs  Master DSP communicates with up to 256 slaves over the heater power bus. No dedicated communication lines are used.  One master, multiple slave design.  DSPs communicate by a half-duplex BFSK technique. 29Project Review RITKGCOE Multidisciplinary Senior Design

Master to Slave Communication Modulation/Demodulation  A sine wave is generated from a binary string using the HRPWM and a passive low pass filter.  The sine wave is transmitted over the DC power bus.  The sine wave is then demodulated back into binary using the ADC with a digital filter.  The Goertzel Algorithm was used to implement the digital filter. 30Project Review RITKGCOE Multidisciplinary Senior Design

Master to Slave Communication Protocol  BFSK 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 = 62.5 kHz  ‘ 1 ’ frequency = 78 kHz  No activity on line means no signal 31Project Review RITKGCOE Multidisciplinary Senior Design

Master to Slave Communication Protocol  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 32Project Review RITKGCOE Multidisciplinary Senior Design

Master to Slave Communication Interface Electronics  Coupling transformer to couple to AC and DC components.  Capacitor along with transformer used to create a high pass filter.  Allows us to create a sine wave on power bus without disturbing the operation of the heaters. 33Project Review RITKGCOE Multidisciplinary Senior Design

Master to Slave Communication Strengths and Weaknesses  Strengths  Used software techniques in the DSP to do the modulation and demodulation rather than using external hardware.  Flexible: different frequency/bandwidth combinations possible.  Weaknesses  Each slave added creates a parallel resistance so a larger and larger signal is needed for each slave added.  We don’t check to see if a message is good until a complete message is received.  Half Duplex only, can only send or receive at one time.  Reliability could be improved. 34Project Review RITKGCOE Multidisciplinary Senior Design

Master to Slave Communication Specifications  Master to slave communication time 20ms  Did not meet, actual communication time ~200ms  Bandwidth < 300KHz  Met, Bandwidth < 90Khz  Bit error rate 1e-6  Did not meet, ber undermined but higher than 1e-6  Signal to noise ratio -40db  Did not meet, snr is around 10db  Amplitude < 10mVpp  Did not meet, Amplitude ~ 1Vpp 35Project Review RITKGCOE Multidisciplinary Senior Design

Master to Slave Communication How could these be improved?  Master to slave communication time 20ms  Reduce code size by splitting up master and slave code  Used external hardware to generate and detect sine wave  Bit error rate 1e-6  Improve synchronization between master and slave Goertzel.  Signal to noise ratio -40db  Longer transmissions per bit, raise the bandwidth  Amplitude < 10mVpp  Output smaller signal and then amplify it 36Project Review RITKGCOE Multidisciplinary Senior Design

Closing Comments  Special Thanks  Margaret Bailey, Jerome Barczykowski, Sohail Dianat, Christopher Hoople, Marca Lam, Chuck Moon, Jay Radhakrishnan, Scott Reardon, George Slack, Perry Voyer, Christianna Walter and John Wellin  Questions and/or Comments Project Review RITKGCOE Multidisciplinary Senior Design37