full mission simulation: second teleconference
DESCRIPTION
Full Mission Simulation: Second Teleconference. West Virginia University Rocketeers Student team : N. Barnett, R. Baylor, L. Bowman, M. Gramlich, C. Griffith, S. Majstorovic, D. Parks, B. Pitzer, K. Tewey, E. Wolfe Faculty advisors : Y. Gu, D.J. Pisano, D. Vassiliadis May 22, 2010. - PowerPoint PPT PresentationTRANSCRIPT
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Full Mission Simulation:Second Teleconference
West Virginia University Rocketeers Student team: N. Barnett, R. Baylor, L. Bowman, M. Gramlich, C. Griffith,
S. Majstorovic, D. Parks, B. Pitzer, K. Tewey, E. Wolfe
Faculty advisors: Y. Gu, D.J. Pisano, D. Vassiliadis
May 22, 2010
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Atmospheric/Plasma Science Payload1. Atmospheric temperature. • Processes: atmosphere heating/cooling mechanisms.
• Objective: identify layers based on temperature profile
2. Terrestrial magnetic field.
• Processes: field controls charged-particle motion.
• Objectives: – Measure vector B, dependence on altitude, geocentric distance.– For high S/N: detect low-frequency waves
3. Plasma and energetic particles. • Processes: solar UV produces ionosphere >85 km. Cosmic rays produce avalanches of particles.
• Objectives:– Emit radio pulse which is reflected where index of refraction=0– Measure density profile; identify E layer peak– For high-activity conditions: high-density patches descend to E-layer altitudes (“spread-F” effect)
Echo
Refracted rays
Refracted rays
n=0n>0
n<0
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WVU in RockSat 2010: Functional Block Diagram
Power SupplyPower Supply
Thermistor
uMag
G
uController
FlashMemory
RBF
Swept-fPulse Tx
Power flow
Comm/Con
Data flow
Z Accel
Gyro
Main Board Radio Board
OpticalPort
ADC
Legend
Fixed-fPulse TxPre-amp &
Power filter
Superhet
LO
Amplifier
IF
InertialSensor
Regs
G
RegsANT
Power
C&DH
Sensors
RF in
uControllerADC
FlashMemory
ANT
ANT
RF out
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Summary of Changes
Since Last Report
- Radio board (transmitter/receiver used to measure plasma density)- Receiver filter: several versions tested, some successful
- PCB: v. 1 delivered. Revisions incorporated in v. 2.
- Control and data acquisition software: in development
- Main board (sensors: orbital and rotational motion, temperature, magnetic field)- Sensor calibration: ongoing
- PCB v. 3 (minor changes from 2nd): ready to be ordered
- Servo for energetic-particle detector included in PCB v. 3
- Independent testing by ABL.
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Receiver: main filter
• State-variable active filter: implemented with NJM1238 quad op amp, shown on perf board
• Stability issues: oscillations– Autonomous (similar to standing
waves); input ignored– Clearest between op amps 2-3
and 2-4.
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Receiver: main filter (cont.)
RLC passive filter: L=1 mH & C=10 pF f0=1.59 MHz. Combine with low R (~50-100 Ohm).
Result: sharp (Q=15-20) response curve for several different configurations.
Frequency generator;driving frequency shown in kHz
Input signal and RLC response
At/near central frequency Far from central frequency
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Receiver: main filter (cont.)
VCVS active filter (1 op amp): amplification over desired range, but broader rolloff than RLC
High response near f0 (~1.5 MHz)
Circuit Rolloff example far from f0 (here: 599 kHz)
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Receiver: main filter (cont.)
1st-order Butterworth implemented as Thomas-1 active filter (3 op amps): unstable, similar to state-variable filter.
Input (sinusoidal) vs. output (flat lines)Output unstable, sensitive to capacitive coupling; easily breaks up into nonlinear, autonomous oscillationsSchematic
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Receiver: main filter (cont.)
1st-order Butterworth implemented as Sallen-Key active filter (1 op amp): stable
f<f0: low responsef~f0: amplification (filter~inverter) f>f0: lower response
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Main filter: summary of responses
RLC,passive (0)
VCVS,active (1)Butterworth as
Sallen-Key, active (1)
Butterworth asThomas-1,active (3)
= filter is a) stable, b) amplifies input, c) amplification occurs over bandpass region centered at design f0
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Programmable Circuit Elements
• The ColdFire PIT is used to control the digital capacitor.
• Earlier we could only control one capacitor (images on right).
• Currently we can control simultaneously multiple capacitors: useful in extending range or resolution of effective capacitance.
Capacitance (pF)
0
2
4
6
8
10
12
14
0 5 10 15 20 25 30 35
Number of Pulses
Capacitance (pF)
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Radio PCB
• v.1 delivered
Transmitter
Receiver
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Radio PCB (cont.)
• Revisions incorporated into v. 2 (receiver shown below)
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Main Board
• Background: the main board was completed in April.
• Sensor calibration is ongoing.
• Data storage: transition to binary files, more efficient storage.
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Main Board: PCB v. 3
• Minor revisions have been made based on feedback from tests on v. 2.
• In addition, to complement the plasma board operation, we have added an energetic-particle sensor operated by a servo.
• Image on right: PCB design without servo leads.
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Main Board: PCB v. 3 (cont.)
• Image on right: new PCB design including servo leads.
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Main Board: Other Tests
• Data acquisition of individual sensors.
• Top image: data acquisition from the high-rate sensors (gyro and accelerometer) on the breakout boards.
• Bottom image: the main board and several breakouts during the same run. The LED on the left represents a servo for the energetic-particle sensor (not connected).
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Main Board: Other Tests
- Electrical interfaces/connectivity (transistor pins corrected; breakout headers added; analog I/O utilized for battery voltage sensor; connection to IMU resolved)
- Mechanical fits (hole-fastener fits; breakout boards added; working area added where accel/gyro used to be; will be used for CR detector/other prototyping)
- Sensor tests: completed (gyro replaced)- Data handling: completed (collected at 1000 Hz; verification LEDs
blinking every ½ second; still need to save as calibrated binary data)- Calibration: not completed- End-to-end (flight) test: completed- Length of tests: 3-7 minutes- Software debugging: appears complete (Programmable Interrupt
Timer/PIT used; all MOD analog and digital pins configured)
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Independent Testing at ABL
• Two students will take the main board to ABL; will participate in tests along with ABL staff.
• Tests planned:1. Board inspection/connectivity of circuit cards by JSTD-certified
engineer2. Thermal/vacuum3. Vibration:
• Sine sweep• Random
4. Impulse/shock acceleration (classical shock or SRS).
• Test schedule: 2 days at end of May/beginning of June.
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Vibration Testing
• ABL will build a basic fixture to mount payload plate.• We have provided them with specifications for plate and canister
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Vibration Testing (cont.)
• Alternatively the plate will be mounted on the canister, and the canister will be bolted on vibration platform
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Vibration Testing (cont.):Impulse Specification
• We have specified the impulse using the RockOn 2009 acceleration profile.
Position wrt Time
020000400006000080000
100000120000140000
0 2000 4000 6000 8000 10000 12000
Time ( .1 seconds)
Alti
tude
(m)
Series1
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Overall Analysis
Launch readiness: we are still working on several issues related to the radio reception and control. We focus on two areas in particular:
1. We have several versions of stable filters in the frequency range of interest and we need to test them against each other.
2. The antenna transmission/reception tests indicate inductive (magnetic) rather than RF coupling. This is probably due to a mismatch in the circuit impedances.
Otherwise we are now integrating the radio board!
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Lessons Learned
Improvements: • We are much more familiar with several sensor and
electronics issues and know how to resolve them than we were a month ago.
• Logistics problems have improved and we are now in a good operational cycle.
Unresolved issues:• Instabilities in the radio filters are delaying the integration
of the radio experiment.
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Conclusions
Issues and concerns:– Stable active filters have been identified; final selection needs to
be done.– Transmission/reception tests are continuing.
Summary/Closing remarks:- The main board will be taken to independent testing at the end
of the month. - There is additional work to be done on several radio board
components.