SPHERES. Synchronized Position Hold, Engage, Reorient, Experimental Satellites. Critical Design Review 15 February Payload Systems Inc

Transcription

1 Synchronized Position Hold, Engage, Reorient, Experimental Satellites Critical Design Review 15 February 2002

2 Agenda Introduction Operational Overview Functional Overview Propulsion Position and Attitude Determination System (PADS) Communications Data Processing Human Interfaces Experiment Hardware and Software Satellites PADS Beacons Laptop Transmitter ISS-Provided Equipment Onboard Software Laptop Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 2

3 SPHERES Points of Contact Principal Investigator: Dr. David Miller Director, MIT Space Systems Laboratory (617) Payload Integration and Safety: Steve Sell Stephanie Chen.. (617) x28 (617) x32 Space Test Program (Code ZR1): Capt. Steve McGrath, USAF, (281) Mark Adams, SAIC, (281) Johnnie Engelhardt, GBT, (281) Jim Steele, Aerospace, (281)

4 SPHERES Team Who s involved: DARPA Orbital Express Program Research and flight opportunity sponsor Massachusetts Institute of Technology Science lead Prototype design and testing Algorithm development. Flight hardware design, fabrication & testing Flight hardware integration & safety DoD Space Test Program and ISS Payload Integration Office Flight manifest on ISS Payload integration & safety support 4

5 CDR Objectives Demonstrate a comprehensive design that delivers required features and characteristics Solicit objective reviews of the design Serve as a feature/hardware design freeze Demonstrate readiness of design for beginning of flight hardware fabrication 5

6 Introduction David Miller

7 Introduction Operational Overview Functional Overview Experiment Hardware and Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 7

8 Motivation To reduce cost and improve performance, many missions are considering distributed spacecraft architectures Routine and autonomous formation flight is essential to the operation of these missions Long duration µ-g is impossible to simulate in the laboratory Therefore, an on-orbit testbed is needed to conduct research in µ-g for maturing these technologies StarLight Terrestrial Planet Finder TechSat 21 Orbital Express 8

9 Benefits of Testbeds Ability to buy down risk Allows development on systems with yet unknown models Can verify modeling results Provides confidence that technologies developed will perform as expected Cost-effective Cost to develop and use a testbed is significantly lower than full system test cost Risk-tolerant Larger number of higher-risk tests are possible in shorter amount of time 9

10 SPHERES Testbed Characteristics Mitigates modeling risk through testing Representative of envisioned missions: TPF, Starlight, TechSat 21, Orbital Express Multi-vehicle testbed Long duration micro-gravity environment: 6 Degree Of Freedom (DOF) per vehicle, close proximity maneuvers Allows testing of new technologies Cost-effective Replenishable consumables Observations by crew reduce operation costs Data (up)downlink and video coverage expedites algorithm design Reconfigurable and upgradeable hardware accommodates new technologies Risk-tolerant Ill-behaved algorithms can be stopped and corrected without affecting future operations Allows software to mature from conception to flight quality without danger of mission failure No chance of loss of testbed due to ill-behaved algorithms 10

11 Characteristics of SPHERES in ISS ISS provides the benefits of a research laboratory-like setting, but in the microgravity environment Human-in-the-loop research will allow testing to be guided along more productive routes Crew can stop a series of protocols when it s obvious they are not working Protocols that perform well can be further explored Know instantly whether data retrieved are good - can repeat if necessary Consumables can be replenished Video and crew commentary will provide valuable feedback to research team Iterative algorithm development; use last week s results to develop this week s tests 11

12 Current Testing Single satellite control on the KC-135 Multiple satellite control at MIT Multiple satellite control on the KC

13 KC-135 Testing Video 13

14 Operational Overview David Miller

15 Introduction Operational Overview Functional Overview Experiment Hardware and Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 15

16 Hardware Components SPHERES consists of three satellites eight-inches in diameter Each satellite is self-contained with power (AA batteries), propulsion (CO 2 gas), computers, and navigation equipment The satellites communicate with each other and an ISS laptop through a low-power wireless (RF) link Operational volume is 6 x 6 x 6 (up to 10 x 10 x 10 is possible) Five ultrasound beacons located in the SPHERES work envelope act as a navigation system Each beacon is self-contained and uses a single AA battery A single beacon is approximately the size of a pager Satellite PADS beacon 16

17 SPHERES Satellite CO 2 tank Thruster - X Ultrasonic receivers Pressure gauge Adjustable regulator Diameter Mass Thrust (single thruster) CO 2 Capacity 8 in (0.2 m) 7.85 lb (3.56 kg) <1 oz (0.2 N) 6 oz (170g) - Y Satellite body axes + Z 17

18 Major Components Laptop Assembly SPHERES Satellites Ultrasound Beacon (5 Total) 18

19 Operational Configurations Mode 1: Single satellite operations examples Long term station-keeping Minimum propellant maneuvers through pre-determined profiles Isolated multidimensional rotation, multidimensional translation Combined rotation & translation Modes 2 and 3: Multiple satellite operations examples (two or three satellites) Docking Topological orientations Independent control Collision avoidance Hierarchical control (leader-follower) Distributed control (consensus) Example configurations on the KC

20 Typical Test Session Transfer protocol/commands via wireless link to satellites Each satellite calculates position from PADS beacons Uplink protocols to OPS LAN prior to SPHERES ops ISS Laptop Satellites perform formation flying maneuver Control loop Appropriate thrusters fire Data continuously downloaded to laptop ISS Laptop Downlink experiment data to ground after SPHERES ops 20

21 Functional Overview Allen Chen

22 Introduction Operational Overview Functional Overview Propulsion Position and Attitude Determination Communications Data Processing Crew Interfaces Experiment Hardware and Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 22

23 Propulsion System Design Drivers Purpose: provide each satellite the means to maintain and change position in the designated work area Must be compatible with ISS internal environment Control System must provide for 6 Degrees Of Freedom System must keep control authority throughout the mission Maximize lifetime of the system The system shall be replenishable on-orbit 23

24 Propulsion Design CO 2 system CO 2 is stored in liquid form at room temperature Constant pressure in the tank Stable performance Analysis indicates that CO 2 toxicity is not a safety concern Solenoid valves provide actuation Nozzles are designed to maximize the thrust CO 2 is expelled in a gaseous form The nozzle constriction is sized so that the CO 2 flow chokes into the nozzle No expansion chamber High Pressure Storage Pressure Regulation Flow Distribution Gas Expulsion 24

25 Propulsion System Schematic High Pressure Low Pressure Manifolds Tank CO 2 Regulator (with HP burst disk) In-line capacitor Pin valve (with HP burst disk) Gauge LP pressure relief valves On/Off solenoid valves High Pressure (HP): 860 psi Low Pressure (LP): Adjustable between 0 and 55 psig Nozzles 25

26 Introduction Operational Overview Functional Overview Propulsion Position and Attitude Determination Communications Data Processing Crew Interfaces Experiment Hardware and Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 26

27 PADS Overview Purpose: to provide real-time position and attitude information to each satellite Two-element design strategy Global elements Ultrasonic beacons attached to ISS walls and ultrasonic receivers located on-board each satellite Provide low-rate (1-2 Hz) satellite position and attitude information relative to ISS interior Local elements Accelerometers and rate-gyroscopes located on board each satellite Propagate satellite position and attitude estimates between the low-rate global measurements Data from the global and local elements are combined using a Kalman Filter Key design drivers Accuracy Update rate (global) Reliability 27

28 Position/Attitude Determination Beacon locations define operational volume Time-of-flight ranging Master satellite requests a global reading by emitting an IR flash Beacons respond to IR flash with ultrasonic pulses Satellites turn off thrusters to listen for the ultrasonic pulses [cm] Time-of-flight range measurements Wall-mounted ultrasound beacons Receivers on the satellite record the times when the ultrasonic pulses are received Satellite Satellites compute ranges based on the time of flight of the pulse Satellites calculate position and attitude from ranges [cm] [cm] 28

29 PADS Global Timeline Master: IR flash IR receive Receive US 1 Receive US 2 Receive US 3 Receive US 4 Receive US 5 Slave: IR receive Receive US 1 Receive US 2 Receive US 3 Receive US 4 Receive US 5 Beacon: IR receive US 1 ping US 2 ping US 3 ping US 4 ping US 5 ping 0 ms 5 ms 25 ms 45 ms 65 ms 85 ms Time 29

30 Beacon Block Diagrams Schematic Block Diagram IR (from Master satellite) IR RX TX support electronics US TX US (to all satellites) Functional Flow Block Diagram Receive IR flash Reset counters Wait specified time (5, 25, 45, 65, 85 ms) Transmit US pulse Iterate indefinitely 30

31 Satellite PADS Schematic Ultrasound IR IR (from Master satellite) US (from 5 beacons) IR US RX US RX RX x12 X24 US US RX US RX RX x24 US X24 RX US X24RX X24 X Gyro Y Gyro Z Gyro PADS Support Electronics Analog Signal Digital Signal Main Processor X Accel Y Accel Z Accel (if Master satellite) IR IR TX IR TX TX x24 X24 X24 31

32 Satellite PADS Block Diagram Synchronize Acquire raw data Correct raw data Kalman filter Global path Receive US 1 Receive US 2 Generate matrix correction Correct matrix Reset counter and Receive US 3 and Calculate rough state guess Flash IR/ receive IR flash Receive US 4 Receive US 5 and Update/ propagate state estimate Request state est. and Inertial path Get accel data (x3) Get gyro data (x3) Note: global and inertial paths occur asynchronously Iterate indefinitely 32

33 Introduction Operational Overview Functional Overview Propulsion Position and Attitude Determination Communications Data Processing Crew Interfaces Experiment Hardware and Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 33

34 Communications Purpose: provide real-time bi-directional satellite-to-satellite and satellite-to-laptop wireless command and telemetry Design Drivers Two wireless communications channels Simulates real world spacecraft communications Satellite to Laptop (STL) - Telemetry and Commands Satellite to Satellite (STS) - Control and Commands Support at least three satellites Should be expandable Accomodate a minimum volume of 6 x 6 x 6 Maximum operational volume expected in ISS Highest data rate possible To allow for different type of mission simulations Low power 34

35 Communications Token ring network STL: 916.5MHz STS: MHz Transmit token passed among units When one transmits all others receive Individual HW ID s Allow data to be directed to specific units 35

36 RF Transmission Data Flow No Have token? Yes Have data? Yes Have No Have No commands? telemetry? No Send token Yes Send commands Yes Send telemetry Yes Token confirmed? No Commands confirmed? Yes 36

37 RF Reception Data Flow No No Data available Yes Data for us? Token Yes Data type Command Telemetry Confirm token Confirm commands Set token Push command Push telemetry 37

38 Data Packet Format Data Packets All data sent across in packets Start byte synchronizes packets (especially after errors) Identifies Origin and Destination Different data types - commands, telemetry, & token Includes a time-stamp of when packet was created Allows variable data size Checksum allows error detection (but not correction) 8-bits, 1 byte Start To From Type Time Time Size Data[0] Data[n] Check1 Check2 sync 7 sats max 7 sats max comm tel token 16-bit timestamp 0.1 s increments since last reset number of data bytes 16-bit checksum for error detection 38

39 Introduction Operational Overview Functional Overview Propulsion Position and Attitude Determination Communications Data Processing Crew Interfaces Experiment Hardware and Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 39

40 Data Processing System Purpose: provide command, data handling, and real-time control capability Design drivers Support other subsystems data processing needs Communications data processing PADS computational support Propulsion thruster actuation Provide house-keeping information to user Battery information Tank usage Allow reconfiguration of control algorithms Enable the complete software to be changed to allow testing of programs with different configurations and goals Maximize processing power for available volume and power Minimize processing needs of bus system to maximize processing power available for control algorithms 40

41 Functional Block Diagram Laptop comm Data Comm Data Other sats New Program Commands Telemetry PADS sensors Global subsystem data Local sensor data DSP Propulsion Power Low battery indicator Expansion port 41

42 Introduction Operational Overview Functional Overview Propulsion Position and Attitude Determination Communications Data Processing Crew Interfaces Experiment Hardware and Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 42

43 Crew Interfaces Satellite Power switching Consumable replacement CO 2 Batteries Pressure system flow control Handling Beacons Power switching Setup and mounting Laptop Protocol loading Data storage Experiment control (GUI) Envisioned operations in ISS Node 1 43

44 Satellite Control Panel Control interfaces for satellites are grouped on one panel Control panel configuration, labeling, and coloring will comply with relevant NASA safety specs Buttons Satellite reset Reset circuit breaker Enable thrusters Switch Power on/off LEDs Power on Low battery Thrusters enabled Future home of satellite control panel 44

45 Preliminary SPHERES GUI 45

46 Experiment Hardware and Software Edison Guerra Simon Nolet Alvar Saenz Otero

47 SATELLITE 47

48 Introduction Operational Overview Functional Overview Experiment Hardware and Software Satellite Structure Propulsion Avionics PADS Beacons Laptop Transmitter Onboard Software Laptop Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 48

49 Aluminum structure Six laser cut rings Six sheet metal brackets Twelve cross members Provides stiffness and mounting points for satellite components Structural Frame Metal bracket Laser cut rings Cross members 49

50 SPHERES Electronics Board Locations Electronics are divided into two assemblies PADS and computing Signal processing Computing Propulsion and power Thruster valve control Power distribution Propulsion and power boards PADS and computation boards 50

51 SPHERES Structural Assembly Part One Electronics assemblies Electronics are assembled inside a partial structure and wired Avionics can be tested on the bench top 51

52 Structural Assembly Part Two Remaining sheet metal brackets are attached Hold battery packs and regulator/tank assembly Mounting brackets 52

53 Structural Assembly Part Three Propulsion system tubing routing Tubing is assembled prior to final structural element placing Manifolds distribute gas from CO 2 tank to twelve thruster nozzles Tubing manifolds Thrusters 53

54 External Shell Structure Two part shell assembly Secured with four fasteners per side Hinged door for battery access Cut-outs for thrusters and sensors Constructed of Polycarbonate Polycarbonate half shell Attachment screw 54

55 Structural Elements Satellite is fully functional without shell Ultrasonic receiver Thruster Aluminum frame Pressure gauge CO 2 tank Battery pack 55

56 Single Satellite Mass Satellite Item Mass (lb) Quantity Mass (lb) Structure Thruster US/IR Sensor Node Avionics Shell (per half) Gas Delivery System Total Satellite 5.08 Consumables Battery Pack Tank (dry) CO Total Consumables 2.77 Total Operational Mass 7.85 lb g 56

57 Introduction Operational Overview Functional Overview Experiment Hardware and Software Satellite Structure Propulsion Avionics PADS Beacons Laptop Transmitter Onboard Software Laptop Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 57

58 Propulsion Hardware Considerations Safety Comply with NASA safety requirements Performance Maximize the capacity of the tank given the space limitation Assembly The overall length of the tank and the regulator assembled should be less than 11 inches The hoses should be fixed to the structure to facilitate access to the different components inside the satellite 58

59 Propulsion System Prototype Adjustable Regulator CO 2 Tank Pressure Relief Valve Capacitor Teflon Tubing Manifolds Nozzle and Solenoid Valve 59

60 Pressure System CO 2 Tank Propellant is CO 2 stored as liquid at 860 psig Tanks have a pin valve for ease of installation to and removal from satellites and prevent venting if removing a non-empty tank Mass Capacity Materials Certification 15.5 oz (440 g) 6 oz (172 g) Tank: Chromolly (steel 4130) Valve: Brass (UNS C36000) DOT-E M4580 Tank with pin valve 60

61 Regulator Assembly Output pressure: adjustable between 0 and 55 psig Custom-made adaptors at the input and output of the regulator Material: aluminum for the regulator, brass and stainless steel for the adaptors 61

62 Capacitor Assembly Helps to maintain constant pressure in the system when firing the thrusters Allows CO 2 to fully evaporate before reaching the fine tubing Capacity: 25 cm 3 Swagelok type connectors Material: stainless steel for the capacitor and aluminum for the fittings 62

63 Minstac Tubing Assembly Distribute the CO 2 to the thrusters Semi-rigid tubing Material: Teflon, PEEK, KEL-F, Valox, aluminum Adaptor Tubing Manifolds Plug 63

64 Relief Valve Assembly Maintains low pressure in the system Vents CO 2 more quickly than the regulator can provide Pop-safety type valve One opening on each side (no thrust) Nominal opening pressure: 58 ± 2 psig Material: brass for both the relief valve and the coupling 64

65 Thruster Assembly Thrusters are solenoid valve and nozzle assembly On/off type valve Maximum operating pressure: 55 psig Power rating: 500 mw Custom-made nozzles Material: Titanium (nozzles) 65

66 Propulsion System Components Manifolds CO 2 Tank Nozzles and Solenoid Valves Pressure Gauge Adjustable Regulator Capacitor Teflon Tubing 66

67 Introduction Operational Overview Functional Overview Experiment Hardware and Software Satellite Structure Propulsion Avionics PADS Beacons Laptop Transmitter Onboard Software Laptop Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 67

68 Avionics Design Drivers Provide processing power for satellites Support all electronic needs Power Propulsion PADS Communications DSP Provide an expansion port for future external upgrades 68

69 Avionics System Overview Bat 1 Switch card Power Propulsion Bat 2 Mother board DSP Power Propulsion PADS Communications Local sensors 6x PADS US/IR 12x Expansion port Comm DSP Beacons Beacon tester Laptop comm 5x 69

70 Power Design Drivers Provide the necessary power and voltages for all subsystems 3.3 V: DSP, PADS, Communications 5 V: DSP, PADS, Communications, Propulsion ±15 V: PADS (gyros and accelerometers) 22 V: Propulsion Meet applicable ISS safety guidelines Maximize battery utilization 70

71 Power Requirements Component Description Power C6701 DSP main processor Sundance DSP Systems, SMT V V RF RF transceivers for wireless communications: MHz & V 868 MHz RF Monolithics Inc, DR UART Serial and parallel communications microcontrollers V 20 MHz) and support electronics Avionics Watchdog circuits, status LEDs, solenoid driver circuitry V (custom) PADS global Infrared and ultrasound receivers and amplifiers; 6 identical V circuits (custom) PADS local Local sensor components: 3 gyroscopes and 3 accelerometers V V PADS µ P PADS system microcontroller: global timing and local A2D V Solenoids Average power is 15.0 W Stand-by power is W Maximum power is W (PIC processor, TBD) Propulsion solenoids. 22V peaks operate 10% of the time (10% * 0.5A * 22V = 1.0 W); at most 6 valves (? total) operate at any one time (50% * 0.1A * 5V = 0.25 W).. Sub-total TOTAL V V 3.3 V * 1.6 A = 5.17 W 5.0 V * 1.7 A = 8.14 W 15 V * A = 0.50 W -15 V * A = 0.25 W 22 V * 0.05 A = 0.96 W W Power consumption varies only due to use of thrusters 71

72 Power Schematic Magnetic overcurrent circuit breaker 12V unreg ( V) 3.3V Regulator Traco TSI3.3S2ROSH Max out: 2A - 6.6W 3.3 V Main power switch Bypass cap. 3300µF 16V electrolytic 5V Regulator Traco TSI5.0S2ROSH Max out: 2A - 10W 5.0 V 15V DC-DC MAXIM MAX772 Max out: 1A - 15W 15.0 V 8AA V 8AA V -15V DC-DC MAXIM MAX776 Max out: 1A - 15W V To Propulsion 72

73 Three main boards Battery pack (2x) Provides diodes and fuse for safety Control panel Switch: Power On/Off Pushbuttons: Reset, Enable Indicators: Power, Low Battery, Enable Regulators Provide necessary voltages 5 V, 3.3 V, ±15 V Pass-through for propulsion signals Propulsion 22 V created directly in propulsion board Watchdog supervisor IC Supervises all components Creates low battery signal 73 Batt pack 1 2 Power Input Switch card 2 6 power signals Power 5V 3.3V 15V -15V GND to Motherboard 12 prop Batt pack enable wdog to Propulsion prop 12 5V unreg GND reset enable Low Batt

74 Power Input Protection Power switch Double Pole: disconnects battery packs when satellite is off 3A Magnetic circuit breaker High speed shutoff (10ms) at rated current Higher current rate to prevent annoyance trips Bypass capacitor filters solenoid spikes 3A Schottky diodes prevent charge between battery packs 1.5A PolySwitch - slow blow, self-resetting fuse 74

75 Battery Pack Provide safety of each individual pack Creates redundancy to prevent single point failure Provides safety of packs outside of satellite Battery pack 8AA 3A Schottky Diode Output voltage: V Min current (2 packs): 0.55A Max current (2 packs): 1.4A Min current (1 pack): 1.10A Max current (1 pack): 2.7A Avg current (2 packs): 0.670A 1.5A PolySwitch Avg power: 15 W 75

76 Switch Card Actuators Power switch Circuit breaker Reset pushbutton Enable pushbutton Indicators Power Low battery Enable BAT 1 +V GND Breaker BAT 2 DPDT switch unreg GND +5V +V GND LED LED LED LED Enable LED LowBat Enable Reset GND 76

77 5V 3.3V SPHERES 3.3V 5V Bypass capacitor 77 GND 15V -15V unreg GND 15V -15V to Power Power Input Board to Mother board 12 LED Enable LED LowBat Enable Reset WDOG prop 5V unreg GND prop 12 to Propulsion Watchdog +5V LED Enable LED LowBat Enable Reset GND

78 Power Regulators (1) Traco 3.3 V and 5 V regulators Average current V V Output voltage 3.3 or 5 VDC ± 0.5% Output current (max) 2.0 A Input voltage V Input current no load 2 ma Input current full load (max) 1410 ma (5 V in) Stand-by current 100 µ A Short circuit protection constant current > 105% (2.1 A) Temperature ranges C MTBF 1,000,000 hr Isolation I/O none Switching frequency 200 khz PWM Vibration Hz 2 g Weight lb (6 g) 78

79 Power Regulators (2) 15 V: MAX772 Output voltage 15.0 VDC ±75 mv Input voltage V Output current (max) 1 A Average current out 16.6 ma -15 V: MAX776 Output voltage VDC ±60 mv Input voltage V Output current (max) 1 A Average current out 16.6 ma 22 V created in Propulsion board 79

80 Propulsion Avionics 22 V supply (MAX668) Create voltage spike & hold prop 12 Driver 1 thr1 3 LED 2 Solenoid output input V 5V 0V spike ~20ms hold time 22V 22V 5V 5V unreg GND Driver 12 22V Supply thr12 3 LED 2 Solenoid in LM555 Out+ Out- Shield 80

81 Satellite PADS Transceivers US/IR Transceiver Boards (12x) Transmit global request IR pulse Receive IR pulse from beacons Receive and amplify US pulse from beacons US RX 1 Amplifier Rectifier Comparator 5V US RX 1 US RX 2 Amplifier Rectifier Comparator US RX 2 IR RX IR RX IR TX Driver IR TX GND 81

82 US Signal Processing US receiver amplification LM6154 high speed quad amplifier 2.5V 2.5V US out 5V Ultrasound receiver Current amplifier Rectifier and 2x amplifier Summer and 3x amplifier Comparator (Digitizer) 82

83 Ultrasound Receiver MuRata Ultrasonic Receiver (MA40S4R) Specifications Nominal frequency 40 khz Sensitivity -63 db typical (0 db = 10 V/Pa) Directivity 80 Capacitance 2550 pf Min. detectable range 8 in (0.2 m) Max detectable range 13 ft (4 m) Operating temperature -40 C to +85 C 83

84 Vishay IR Receiver TFDU4100 Photonic Detectors IR Hardware IR Transmitter PDI-E804 Specifications Wavelength Supply voltage Supply current 880 nm 5V 2.5 ma Specifications Wavelength Peak forward current (10 µ s, 10 Hz) Max power dissipation Output power (typical) 880 nm 2.5 A 160 mw 24 mw 5V IR RX SENSE, IR TX 5V IR RX GND in 2A 10µs Pulse 84

85 Motherboard Overview Power STL Antenna STS Antenna CommPort 0 12 Comm CommPort 1 12 Comm DSP CommPort 2 12 CommPort 3 12 Global bus 80 5V 3.3V GND PADS Expansion port DIO Local sensors PADS US/IR Expansion port Prop Out In 85 Motherboard

86 PADS & DIO Avionics PADS support in mother board Local sensor support US/IR support DIO support Propulsion register 12 outputs General output register LED Enable WDOG Reset General input register LED Low battery External port detection US/IR 12x Prop Out In Gyro 3x Accel 3x 86 5V IR TX IR RX US RX V signal 15V -15V signal 5V 3.3V 15V -15V GND A/D from Power FPGA 12 5 Mother board reset to DSP CommPort 2 12 Global bus 80

87 PADS & DIO Design Drivers Implements measurement circuitry for PADS One infrared transmitter command 12 infrared receiver channels 24 ultrasound receiver channels Six 12-bit A/D channels Propulsion register (to control solenoid valves) 12 outputs with read-back capability General output register Two outputs with read-back capability General input register Two inputs 87

88 PADS & DIO Functional Block Diagram US Receiver Pulses (0..23) IR Receiver Pulses (0..11) FrameStart Frame Position Determination Subsystem Xilinx Sparta-II or Virtex FPGA VDD Xilinx FPGA Configuration EPROM (XC18Vxxx) 5V to 2.5V Step-down Regulator (MAX1644) 25 MHz Oscillator (ECS-3953C-250) Timing Generation Sample Clock Central Control MUX C40 CommPort Controller Data(0..7) Control(0..3) C40-style CommPort IR Transmitter Pulse Out System Clock A/D Controller Decode Address(0..30) Data(0..31) Control(0..16) TIM-40 Global Data Bus Register Register Register Accelerometers & Rate Gyros A/D Converter (MAX1294AEEI) Propulsion Valves General Outputs General Inputs 88

89 Design Details Implemented (almost) entirely in one Field Programmable Gate Array (FPGA), augmented with FPGA configuration PROM, clock source, A/D converter, and voltage reference Utilizes Xilinx Spartan II FPGA (XC2S200) 5,292 logic cells - 200,000 gates Maximum 284 I/Os 75 Kb distributed RAM, 56 Kb block RAM Xilinx In-System Programmable PROM (XC18V02) 25 MHz Oscillator (ECS-3953C-250) MAX1294 six-channel, 12-bit A/D converter MAX6250 5V voltage reference MAX1644 5V to 2.5V step-down regulator 89

90 Position Determination Timing Generation Interface FrameStart Frame System Clock US0 Pulse In Reset Clock Enable 24 bit Counter Q Pulse Synch Pulse Out Enable Clock D 24 bit Register Q D 24 bit Latch Q Ultrasound Receivers Interface US Pulses (0..23) US1 US23 Pulse In Pulse Synch Clock Pulse In Pulse Synch Clock Pulse Out Pulse Out Clock Reset Enable D 24 bit Register Clock Reset Enable D 24 bit Register Clock Reset Q Q Gate D Gate D Gate Reset 24 bit Latch Reset 24 bit Latch Reset Q Q Output Multiplexor Interface Clear Registers Gate Central Control Interface 90

91 Timing Generation Load Divisor Divisor (23:0) 25 MHz from Oscillator ClockIn ClockOut Load D 24 bit Divider Q Clock Reset TCount D Clock D-type Flip-Flop Q _ Q Sample Clock CLKDLL System Clock ClockOutX2 System Clock X2 Clock Pulse Synch Pulse Out Frame Start IR Pulses (0..11) Pulse In 12 91

92 CommPort Controller TI C40 CommPort TIM C6701 CommPort Write TX Data TX Data Write D Full FIFO (15 words of 32 bits) Read Q Empty Comm Port (from Sundance) Write D Full FIFO (15 words of 32 bits) Read Q Empty Enable Transmitter Clock D SET CLR Q Q Reset 92

93 A/D Subsystem VDD Command/Data DIO(11:0) VDD Command Write Write 4.7 uf 0.1 uf Data Read A/D Select Read CS A/D Converter (MAX1294AEEI) GND COM Sensor Return Conversion Complete INT CH(5:0) From Gyros & Accelerometers Conversion Clock Clock VREF OUT 1512 VDC IN Voltage Reference (MAX6250AESA) 2.2 uf 2.2 uf GND 93

94 Accelerometer Specifications Honeywell Q-Flex Accelerometer, QAT160 Specifications Performance Input Range Bias ±20 g <20 mg Scale factor 2.75 ma/g ±1.8% Threshold and resolution Bandwidth Noise 0 to 10 Hz 10 to 500 Hz RSS bias and scale factor one-year repeatability <5 µ g <200 Hz 20 µ g RMS 200 µ g RMS 1 mg Electrical Input voltage ±12.5 to ±15.5 VDC Quiescent current 6 ma per supply Quiescent power 180 mw Physical Mass 0.12 lb (55 g) Size ~1.0 inch diameter by 0.73 inch high Core materials Stainless steel Operating temperature -40 to 160 C 94

95 Accelerometer Amplifier Current source accelerometers; require load resistor Bias and amplify ±V accel to 0-5V scale Gain of V R F R F 2.5V 5V in R A + - out R L 95

96 Gyroscope Specifications Systron Donner Inertial Division BEI Gyrochip II, QRS Specifications Performance Input range Full range output (nominal) Scale factor, scale factor calibration Scale factor over temperature (dev. from 22 C) Bias calibration (at 22 C) Short term bias stability (100 s) Bandwidth Output noise (DC to 100 Hz) ±50 /s 0 to +5 VDC 30 mv/( /s), ±2% of value 0.06%/ C +2.5 ±0.045 VDC 0.05 /s >50 Hz 0.05 /s/(hz) 1/2 Electrical Input voltage Input current +9 to +18 VDC <20 ma Physical Mass 0.11 lb ( 50 g) Operating temperature -40 C to +85 C 96

97 Communications System reset GND 3.3V 5V STL antenna STS antenna from Power CommPort 0 12 to DSP PIC 3 RF CommPort 1 12 PIC 3 RF Mother board 97

98 Comm Channel Detail One of two comm channels DSP CommPort 12 PIC 16C66 UART kbps 128 Byte I/O buffer TX RX R/T RFM DR300X or MHz kbps 1 mw Helical antenna -1dB Mother board RFM DR300X 98

99 PIC Algorithm Serial RX interrupt Interface TIM40 CommPort with UART serial data Parallel bi-directional data bus with token-style handshaking 128 byte buffer each for input and output No Check RX buffer Not empty Have token? Yes Send data to DSP Token request? Empty No Request token Yes Give token Empty Check CommPort Not E TX buffer Set R/T Timer int clear R/T Transmit 99

100 DSP / Motherboard Interface Sundance SMT375: TI C6701 DSP based board Provides all processing power Communicates via TIM40 standard CommPorts and global bus Comm Comm PADS Expansion port DIO Motherboard 100 CommPort 0 12 CommPort 1 12 CommPort 2 12 CommPort 3 12 Global bus 80 5V 3.3V GND DSP

101 DSP Sundance SMT375 specifications Form factor Single-width TIM CPU TI TMS320C6701 Speed 167 MHz FLOPS 1 GFLOPS peak Floating point 32 bit RAM 16 MB Cache 512 KB ROM 512 KB CommPorts 6 CommPort rate 20 MBps Programming C/C++ IDE TI CCS 2.0 Power 7 W 101

102 SPHERES Expansion Port Provide digital interface for future expansions Global data bus connector 32-bit bi-directional data 31-bit address One RS232 serial line DSP Implemented in same manner as communications CommPort 3 12 Global bus 80 PIC 16C66 80 Mother board V 15V -15V US/IR (2x) Expansion US/IR (2x) PADS Satellite US/IR (2x) 2 80 GND 2 80 Expansion port 80 GND 5V 15V -15V Serial I/O Global data bus

103 PADS BEACON 103

104 Introduction Operational Overview Functional Overview Experiment Hardware and Software Satellite PADS Beacons Laptop Transmitter Onboard Software Laptop Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 104

105 Ultrasound Beacon Structure 3.3 cm (1.3 in) Beacon power switch IR receiver Beacon components One IR receiver One US transmitter One AA battery Associated circuitry 10 cm (3.9 in) AA Battery Ultrasound transmitter Mass Dimensions Power (inc lifetime) US emitter frequency 0.25 lb (113 g) 1.3 x 3.9 x 1.7 in (3.3 x 10.0 x 4.3 cm) TBD 40 khz 4.3 cm (1.7 in) 105

106 Beacon Assembly Drawing 106

107 Beacon Dimensions Drawing 107

108 Beacon Electrical Schematic Listen to IR trigger Transmit ultrasonic (US) pulse at t = {(N-1)*20+5} ms Battery (1AA) N = beacon number (1-5) 3.3V 12V Selectable beacon number Single battery operation On/off switch IR RX PIC 12LC508A Driver Low battery LED ID SW 3 US TX 108

109 Beacon Power Schematic Single AA battery provides >24hrs operation Power requirements US driver: 12V, 90 ma, 1.1 W (peak), duty cycle 0.02% PIC: 3.3V, 0.8 ma, 2.64 mw 3.3V Battery (1AA) Switch MAX1674 MAX761 V out = 3.3V A max = 420mA V out = 12V A max = 150mA 109

110 Beacon Controller PIC12LC508A 3.3V 8-pin microprocessor Input: IR RX Output: US TX IR RX PIC 12LC508A Driver Octal binary switch 4 MHz Algorithm Rotary digital switch 3 Boot Read octal switch IR RX? Yes Delay loop Set US TX via PWM No Set delay = [20*(n-1)]+5ms 110

111 US Transmitter Amplifier US transmitter amplifier 12V NAND gate creates effective 24V drive signal Actuator is a resonator Effectively a high-pass filter Steady voltage does not drive speaker Out+ In Out- Out+ - Out- Out- Out+ In V time 111

112 Ultrasound Transmitter MuRata Ultrasonic Transmitter (MA40S4S) Specifications Nominal frequency 40 khz S.P.L. 120 db typical (0 db = 0.02 mpa) Directivity 80 Capacitance 2550 pf Min. detectable range 8 in (0.2 m) Max. detectable range 13 ft (4 m) Max. input voltage Operating temperature 20 V p-p continuous signal -40 C to +85 C 112

113 Beacon Tester Schematic Beacon tester Creates IR pulse Indicates reception of US pulse Battery (1AA) Switch MAX1674 LM555 LED Pushbutton LM555 LM555 LED Comparator LED Driver Satellite US/IR transceiver (1 US only) Rectifier IR TX IR RX Amplifier US RX 113

114 LAPTOP TRANSMITTER 114

115 Introduction Operational Overview Functional Overview Experiment Hardware and Software Satellite PADS Beacons Laptop Transmitter Onboard Software Laptop Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 115

116 Laptop RF Hardware Data from Serial port Power from PS2 keyboard port 5V GND LM V Serial data TX RX 14C232 TX RX DR CTS CTR0 RS232 level converter RFM RF MHz 116

117 ONBOARD SOFTWARE 117

118 Introduction Operational Overview Functional Overview Experiment Hardware and Software Satellite PADS Beacons Laptop Transmitter Onboard Software Laptop Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 118

119 Onboard Software Design Drivers Purpose: provide a standardized and flexible interface to support the needs of the Guest Investigator Program The software structure will facilitate rapid development and modification of tests and maneuver profiles The software will provide high-level interfaces for Satellite to satellite communications Satellite to laptop communications (command & telemetry) Position and attitude determination Control of thrusters The software structure will facilitate the inclusion of flight code in a simulation environment Simulation environment will be used to verify compilation and execution of custom code 119

120 Software Design Propulsion interrupt (1000 Hz) Controller interrupt (50 Hz) Thrusters Control algorithm Laptop Local sensors PADS data collection State estimator STL communications Global request / infrared flash Watchdog Background processes (free running) Housekeeping STS communications Other satellites 120

121 Guest Investigator Program The SPHERES Guest Investigator Program (GIP) provides a multi-level development environment for control alogorithms on the SPHERES testbed. Development and verification of code occurs on four platforms Each platform has benefits and limitations Increasing Accessability GIP simulation (1-g, µ-g) GFLOPS simulation (1-g, µ-g) SPHERES laboratory (1-g) SPHERES ISS (µ-g) Increasing Fidelity 121

122 GIP Development Parts GIP simulation (1-g, µ-g) A simulation tool for the development and coding of control algorithms Allows independent development - does not require direct interaction between the guest investigator and the MIT SPHERES team Provided to guest investigators in the form of ANSI C source files Used to verify correct compilation of code, and basic operation in a lowfidelity simulation of the testbed dynamics GFLOPS simulation (1-g, µ-g) High fidelity, easily reconfigurable verification tool Accounts for the separated nature of the free-flyer satellites, interrupt and background process timing, and the expected disturbance environment SPHERES laboratory (1-g) Hardware is identical to flight hardware Limited to 3-DOF (mounted on air-carriage) SPHERES ISS (µ-g) 122

123 GIP Development Plan M.I.T. GIP interface delivery Independent source code Deliver to SPHERES GIP simulation GFLOPS simulation Laboratory testbed International Space Station Guest Investigator at local facility 123

124 Control Interfaces To accommodate current and future needs of the GIP, three software frameworks are available for control code implementation on the SPHERES testbed The standard control interface An organized modular control framework into which precisely defined code blocks are placed Predefined inputs and outputs Maneuver element functions can be reused Simple to use Requires limited knowledge of the code Changes to maneuver behavior can be made at several levels without digging through code Facilitates very easy integration with other algorithms that may be used during a given test period 124

125 Standard Control Interface Test 1 Set parameters Maneuver 1 Command Controller Mixer Terminator Maneuver 2 Maneuver 3 Test 2 Set parameters Maneuver 1 Maneuver 2 Maneuver 3 Command function state error Controller function force/torque cmd Mixer function thruster cmd Terminator function end maneuver 125

126 Control Interfaces The direct control interface Allows for the placement of guest investigator code blocks directly into one or more of the interrupt and background process handlers, by replacing the existing handler code. Requires in-depth knowledge of the existing code and insight into the interaction of different processes May be difficult to integrate with other algorithms during a given test period. The custom control interface Has no specific limitations on code modifications May be used if exceptional freedom is needed in algorithm design. Requires collaboration with the MIT SPHERES team during the development process May lead to significant issues during integration of the code with algorithms from other researchers. 126

127 LAPTOP SOFTWARE 127

128 Introduction Operational Overview Functional Overview Experiment Hardware and Software Satellite PADS Beacons Laptop Transmitter Onboard Software Laptop Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 128

129 SPHERES GUI Elements Data displayed on GUI Reduced satellite telemetry (position, attitude) Commands interface Satellite status information (tank, battery, communication status) Log / Comments input Instructions (per protocol) Preview protocol window Real-Time Virtual Reality Display Debugging software 129

130 Preliminary SPHERES GUI 130

131 Command and Status Windows Command window Programs are uploaded to the satellites Protocols within each program will not need to be uploaded individually, only run individually Satellite status window Displays telemetry Use NASA display standards as guidelines 131

132 Additional GUI Windows Instructions window Explain the current protocol in text Provide checklist style instructions Comply with appropriate NASA guidelines Debug window Allows crew member to troubleshoot Notes / Log window Simple questionnaire style Crew members have ability to enter comments Preview and/or Real-Time Virtual Reality display window Allows operator to preview the motion in different frames of reference and/or allows operator to view motion sensed by satellites 132

133 Preview / RT VR Display 133

134 Mission Logistics Stephanie Chen

135 Introduction Operational Overview Functional Overview Experiment Hardware and Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 135

136 Mission Logistics SPHERES on ISS for two increments Ascent flight ISS-12A.1 (STS-116) Re-supply flight ISS-13A.1 (STS-118) for replacement of consumables Descent flight ISS-15A (STS-119) Operation Time Allocated 24 hours operation time (twelve 2-hour sessions with option for eight 3-hour or six 4-hour sessions) Setup and tear down time not included in total operations time Initial stowage requirements Three SPHERES satellites Five US beacons Laptop transmitter Consumables (CO2 tanks and battery packs) Spares are TBD 136

137 Stowage Allocation SPHERES is allotted 1.83 Middeck Locker Equivalents (MLEs) over ascent and resupply flights 1.5 MLE total on ascent flight 0.33 MLE total on one resupply flight Stowage likely to be in Cargo Transfer Bags in the Multi- Purpose Logistics Module (MPLM) Possible to be stowed in actual middeck locker 137

138 Consumables Replacement CO 2 tanks and battery packs CO 2 tanks Part of SPHERES mission investigates ways to minimize propellant usage This means that no exact number of tanks can be determined for total operations Initial estimate is 48 tanks from fixed stowage constraint (top-down) Batteries Current estimate is 64 battery packs split between ascent flight and resupply flight Two approaches were taken to determine consumable estimates: top-down (fixed stowage constraint) and bottom-up (fixed operation hours) 138

139 System Assumptions 24 hrs operation time... Does not include setup and tear down Does include time between protocols (writing down notes, uploading new protocols, etc.) Average 15 minutes per test protocol; time between protocols equals time running protocols (average 15 min.) Greater restriction on volume rather than mass Tank packing based on JSC estimate, 50% packing margin for all other items 139

140 Packing Analysis Current (Volume Constrained) Additional needed to complete baseline mission Total (Operations- Hours Constrained) Volume (MLE) Tanks Battery Packs % of Baseline Mission Operations-Hours With current MLE allotment, can complete 80% of baseline mission: 19.2 Ops hrs Additional 0.29 MLE allows completion of entire baseline mission: 24 Ops hrs 140

141 ISS Equipment Workstation SPHERES will use Payload Equipment Restraint System (PERS) as a temporary workstation H-Strap interfaces with seat track provides two sides of Velcro Attach laptop restraint for configurable laptop station Belly bag can be used to contain extra hardware (satellites) during test session Laptop Restraint Belly Bag H-Strap 141

142 ISS Equipment Laptop SPHERES GUI runs protocols from laptop Protocols uplinked to OPS LAN but no connection is required during testing Data stored on laptop until downlinked to ground following test session US beacons will attach to seat-track interfaces and/or handrail clamps Locations will be entered into laptop prior to operations ISS Laptop Handrail clamp 142

143 Operational Scenarios SPHERES will operate in United States Operational Segments (USOS) only Ideal test area is 6 x 6 x 6 Most likely will operate in 5 x 5 x 10 given ISS Node configuration Envisioned operations in ISS Node 1 Envisioned operations in US Lab 143

144 Typical Crew Operations Unstow equipment Setup test area (position US beacons) Take down and stow equipment Load tanks & battery packs into satellites Upload protocols from laptop to satellites Run protocols from laptop YES NO YES Satellites out of gas / power? NO Test session over? 144

145 Open Issues Steve Sell

146 Introduction Operational Overview Functional Overview Experiment Hardware and Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 146

147 Open Issues Hardware design issues RF Antenna system placement is TBD Payload integration issues Possible interference issue with the Russian module for the MHz frequency Ultrasound emissions need to be reviewed by Life Sciences and Animal Research groups at NASA/JSC to determine compatibility Assessment of impact to ISS CO 2 scrubber system! These issues are currently being coordinated with the appropriate entities in the ISS program 147

148 Current Status & Build Schedule Steve Sell

149 Introduction Operational Overview Functional Overview Experiment Hardware and Software Operations and Mission Logistics Open Issues Current Status / Build Schedule 149

150 Current Status Electronics circuit design complete Propulsion system design is complete and prototyped Mechanical design nearly complete - only a few minor remaining tasks Possible battery pack redesign to eliminate wires Finalize hinge/latch on battery compartment doors Provide mounting for final antenna placement No issues are holding fabrication start 150

151 Major Build Schedule Milestones Critical Design Review: February 2002 Engineering Unit fabrication start: March 2002 Long lead and low-risk components ordered immediately after CDR (e.g., frame, propulsion system) Engineering Unit fabrication complete: May 2002 KC-135 Test of Engineering Unit: June 2002 Flight Units fabrication start: June 2002 Flight Units fabrication complete: September

152 Questions Adjourn