Transcript WVU_FMSTR

Full Mission Simulation
Test Report
West Virginia University Rocketeers
Students: N. Barnett, R. Baylor, L. Bowman, M. Gramlich, C. Griffith,
S. Majstorovic, D. Parks, B. Pitzer, K. Tewey, E. Wolfe
Faculty: Y. Gu, D.J. Pisano, D. Vassiliadis
May 12, 2010
Atmospheric/Plasma Science Payload
1. 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 Elayer altitudes (“spread-F” effect)
n>0 Refracted rays
n=0
n<0
Echo
Refracted rays
WVU in RockSat 2010:
Functional Block Diagram
Main Board
Radio Board
Power Supply
G
Power Supply
RBF
RF in
G
ANT
Regs
Flash
Memory
Inertial
Sensor
A
uController D
Regs
Fixed-f
Pulse Tx
Pre-amp &
Power filter
uMag
LO
Optical
Port
ANT
RF out
Super
het
IF
Swept-f
Pulse Tx
ANT
Thermistor
C
Amplifier
Z Accel
Gyro
Flash
Memory
A
D
C
uController
Legend
Power
Power flow
C&DH
Comm/Con
Sensors
Data flow
3
Changes Since Subsystem Integration
-
Main board (sensors for: orbital and rotational motion, temperature,
magnetic field)
-
-
All sensors and electrical interfaces: tests completed
Flight software, incl. data acquisition and storage: tests completed
Servo for CR detector included in PCB
Sensor calibration: ongoing
Independent testing by ABL: electrical, mechanical, vibration.
3rd version of PCB (minor changes from 2nd): ready to be ordered
Radio board (sensors for plasma density)
- Receiver (Rx) active filter: redesigned (two versions: state-variable and
VCVS), in testing phase
- Rx detector: two designs (analog circuit with diode vs. AD637 converter)
compared; analog circuit was chosen
- Tx/Rx antennas: several prototypes constructed; in testing phase
- PCB: completed
- Control and data acquisition software: in development
-
Canister replica completed
Main Board
• The main board was
completed in April.
• Since then the flight
software, incl. sensor
control, and data
acquisition/storage, was
finished and tested.
• The main board has
been mounted on the
Makrolon along with
power supply, G switch
and accelerometer/gyro
board
Radio Board: PCB Design
• Several board components
have been redesigned
• Top image: PCB design
• Bottom image: the PCB
showing the microprocessor
and flash memory, power
supply, RBF and G switch,
and receiver active filter. The
detector has since been added
at the center.
Test Description: Main Board
-
-
-
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)
Test Description: Radio Board
-
-
Active filter: comparison of 3 designs (state-variable, biquad, VCVS;
electrical connectivity (breadboard vs. perf board); choice of op amp
types (operating voltages; slew rates)
Detector: comparison of two designs
Antenna: Inductive vs. RF coupling
Calibration: not completed
End-to-end test: not completed
Software: control of digital components (cap is close to completion;
potentiometer incomplete)
Test Results
- In the following slides we present and discuss
selected results from the two boards.
Test Results (1): Main Board
• Testing the flight
software on the
main board.
• Shown on the right
is the disassembled
board during such a
test.
Test Results (2): Main Board Sensors
• 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 assembly during
the same run. The LED
on the left represents a
servo (not connected
here).
Test Results (3): Circuit Elements
• In order to tune the
Tx/Rx pair we use
digital circuit
elements.
• Image on right:
debugging the
digital resistor.
Test Results (3): Circuit Elements
• The ColdFire PIT is used to
control the digital capacitor
and the serial peripheral
interface (SPI) is used for the
resistor.
• Top image: running a test
on the MAXIM capacitor and
recording the reactance.
• Bottom image: results from
a test on the capacitor: PIT
pulses delivered versus
measured capacitance.
Capacitance (pF)
14
12
10
8
Capacitance (pF)
6
4
2
0
0
5
10
15
20
Number of Pulses
25
30
35
Test Results (4): Detector Design
1. Analog circuit (detector with backdiode):
2. AD637 converter:
• Green: high-pass filter
• Red: half wave rectifier
• Blue: low-pass filter
• Brown: AD8099 op amp w/ squaring FB loop
• The receiver’s detector rectifies the
active-filter voltage and turns it into DC
(right image).
• Two alternative designs (top images)
were compared.
Digital oscilloscope output illustrating
half-wave rectification of AC input
Test Results (4): Detector Design
The ideal detector output is 1) DC, 2) constant over a wide
frequency range, and 3) linear (or at least monotonic) with
input amplitude. Below are 2 results from the analog circuit:
• Red is the output voltage when
frequency scan was performed at 3V
p-p, while blue is at 2V p-p.
• The wobble is well within
measurement error, no more than one
millivolt.
• The output amplitude is monotonic (actually
linear) with input
• However, only over a narrow input voltage
range
Conclusion from these and other tests:
analog circuit is satisfactory, chosen over
converter.
Overall Analysis
Launch readiness: we are still working on several issues related to the
radio reception and control. The following issues are problematic:
• The active filter in two realizations (state-variable, biquad) is not
stable above 1.1 MHz (needs at least 1.6 MHz). We may resort to the
simpler VCVS version which is more stable.
• The antenna reception is weak and indicates inductive (magnetic)
rather than RF coupling.
• Otherwise the board is very similar in hardware (PCB, processor, data
acquisition, etc) to the main board which has been ready for some time.
Lessons Learned
Improvements:
• Logistics problems have improved and are now in a
good timing.
• We are much more familiar with several sensor and
electronics issues and know how to resolve them than
we were a month ago.
• Task allocation has improved, but is still not perfect.
Unresolved issues:
• Basic-research complications in some components are
delaying the construction of the radio experiment.
Conclusions
Issues and concerns:
– Active filter design is evolving.
– Transmission/reception tests are continuing.
Summary/Closing remarks:
- The main board tests have been completed and
independent testing has been scheduled.
- There is additional work to be done on several radio
board components.