1. Image Acquisition and Processing of Remotely Sensed Data (ImAP RSD)
Dec08-01: Inertial Measurement Unit (IMU)
Team: Luis, Julian, Amar, Matt
Client: Matthew Nelson - Space Systems and Controls Lab (SSCL)
Advisor: Dr. Basart

2. Presentation Outline Background/History Requirements Specification
Project Plan
Design
Testing/Verification on IMU system
Project Evaluation

3. Background/History

4. ImAP RSD Motivation
Methods of monitoring crop health over large areas are currently cost and labor intensive
Airplane
Manual Inspection
ImAP RSD initiated by SSCL HABET program to develop an improved method of monitoring crop health
Automated photography via high-altitude weather balloon
Accomplished by integrating multiple subsystems including:
Horizon Detection, Inertial Measurement Unit, GPS, Processing, and Camera systems

5. ImAP RSD Concept Sketch

6. ImAP System Description
The ImAP RSD system will be mounted as a payload attached to a high-altitude weather balloon.
The onboard sensor systems will be used to determine payload flight path and orientation
This system will capture images at predetermined waypoints using flight prediction software
Collected field images will be analyzed to extract image intensities and make geometric corrections
The corrected images will be transferred to a plant pathology team who will interpret the images

7. Horizon Detection System
Developed by previous team to determine pitch and roll
Thermopile System
Compares sky and ground temperatures to determine horizon
Image System
Aquires images and uses DSP to determine horizon
Completed in Spring of 2008

8. Requirements Specification

9. Dec08-01 Problem Statement
The ISU SSCL requires an Inertial Measurement Unit (IMU) and data logging system for the ImAP RSD project.

10. Block Diagram

11. Operating Environment
The payload will operate at altitudes from 20,000 – 30,000+ feet
The payload will experience temperatures ranging from -40° to 80°C

12. User Interface RCA power jack Serial Port
11V
Serial Port
RS-232
BCD to primary processor
Logomatic universal data logger
SD Card
Post Flight Analysis

13. System Requirements Functional Requirements
FR01: IMU shall measure balloon oscillation frequency and angular rotation rate to degree per second.
FR02: IMU shall measure linear acceleration to 0.01g for each of the three principle axes.
FR03: Data logging system shall log at a 100HZ+ rate with 10 bit or greater precision.
FR04: IMU shall operate over a temperature range of -25˚ C to +85˚ C
Non-functional Requirements
NR01: IMU shall receive power from a 11.1V nominal lithium-ion battery
NR02: IMU shall function for a minimum of 2 hours using a 4 Amp-hour battery
NR03: IMU may measure temperature and voltage levels during flight.

14. Market Survey: IMU Commercial IMUs
SEN IMU with 2 degrees of freedom for $99.95
Inertia-Link-2400-SK1 IMU for $
Military grade IMUs
Buying an IMU would defeat the purpose of a student project

15. Deliverables Project Plan √ Design Report √ Final Report
Project Poster √
IRP Presentation
IMU √
IMU User Manual √

16. Project Plan

17. Work Breakdown Structure: S08
Personnel
Gyro and Accelerome ter Research
Microcontr oller and Flash Memory Research
Gyro and Accelerome ter testing
Microcontr oller and Flash Memory Testing/Pro gramming
Operational Manual
Documenta tion, planning & organizatio n
Total Hours
Luis 20 10 18 30
118
Julian 35
115
Matt 25 8 15
113
Amardeep
Total 75 48 70 88 80
100
461

18. Work Breakdown Structure: F08
Personnel
IMU Circuit Board Design & Testing for Data Acquisition
Gyro and Accelerometer Calibration
System Integration
Operational Manual
Documentati on, planning & organization
Total Hours
Luis 30 25 20
125
Julian 50 7 35
132
Matt 15
120
Amardeep 40 10
Total
150 92 85 90
502

19. Resource Requirements
Estimated Hours
Estimated Cost
***Insert Parts list cost

20. Project Schedule: S08

21. Project Schedule: F08

22. Risks Unfavorable weather Power Failure Continue or cancel mission
Schedule another flight

23. Design

24. Theory of Operation
An accelerometer coupled with a rate gyro can efficiently be used for attitude determination purposes. Rate gyros measure angular rotation rates. By subtracting out known linear accelerations, an accelerometer can be use as a tilt measurement device. These two angles can be combined in an optimal fashion to accurately determine attitude.

25. Pendulum Model of HABET system
The HABET balloon and payload system has been modeled as a simple, 2-D rigid pendulum. From this model we can determine angular rates, as well as the normal and tangential components of acceleration that the payload will experience.

26. Rate Gyro Model
The equation of motion on the left can be numerically integrated to obtain rotational rates. This model is only for roll/pitch rates.
These rotational rates will help us choose the appropriate rate gyro for our project. We have simulated this model on Simulink. The results follow.
Fig. Model for determining roll/pitch rates.

27. Rate Gyro Simulink Model

28. Rate Gyro Simulink Results
Roll/pitch rates under 75°/sec.
From past data, we have determined that yaw rates typically range from 20°- 50°.
FFT results suggest a sampling rate greater than 90Hz.
Conclusion:
Rotational rates and sampling rate obtained from math model meet functional requirements. Rate gyro used in this project, MLX90906, measures 300deg/sec, which satisfies both functional requirements and math model.

29. Accelerometer Model
By assuming a simple pendulum, the acceleration equation reduces to the one boxed in red. This equation measures tangential and normal components of acceleration.
These acceleration values will help us choose the appropriate accelerometer for our project. We have simulated this model on Simulink. The results follow.

30. Accelerometer Simulink Model

31. Accelerometer Simulink Results
Greatest magnitude of acceleration expected is under 1.5g.
FFT results suggest a sampling rate greater than 80Hz.
Conclusion:
Acceleration and sampling rate obtained from math model agree with our functional requirements. Accelerometer used in this project, MMA7260Q, measures ±2g’s, which satisfies both functional requirements and math model.

32. Data Storage Space and
We are required to log for a maximum of 3 hours. A 1 GB SD Card will be used for data storage
Using a baud rate of symbols/sec, we can log for approximately 28 hrs (maximum) at this rate

33. Electric schematic

34. Mechanical CAD of IMU Casing and PCB boards

35. Power Budget
Device
Maximum I [A]
Quantity
Flight Duration [hr]
Amp-Hours
MMA7260Q Accelerometer
.0008 1 3
.0024
MLX90609 Gyroscope
.02
.18
ATMega128
.019
.057
Logomatic
.08
.24
LM78XX Voltage Regulator
.008
.024
The power budget for the IMU components totals at Amp-Hours and will be powered by a 4.8 Amp-Hour battery leaving Amp-Hours for other systems.

36. Software Flow

37. Testing/Verification of IMU system

38. Rate Gyro Testing/Calibration
EMI effects: Electromagnetic interference degrades or obstructs the performance of the circuit.
Output verification using test platform:
Encoder test platform 
Rate gyro  angular rate
We compare it by differentiate and angular rate

39. Accelerometer Testing/Calibration
EMI Shielding: Electromagnetic interference degrades or obstructs the performance of the circuit.
Tilt measurement using test platform:

40. Test Platform Rotations
Maximum 400deg/s

41. Test Platform Accelerations

42. Accelerometer Tilt Angle Measurements

46. Project Evaluation

47. Earned Value Analysis Spring 2008 Tasks Budgeted Hours Actual Hours
BCWS
BCWP
ACWP
IMU Research 75 72
$750.00
$720.00
MCU Research 48 42
$480.00
$455.00
$420.00
Sensor Testing 70
$700.00
$684.00
Programming/SW Debugging 88
760
$880.00
$810.00
$760.00
Documentation
100
109
$1,000.00
$984.00
$1,090.00
Subtotal
$3,810.00
$3,683.00
$3,740.00
Fall 200
IMU Design
150
173
$1,500.00
$1,430.00
$1,730.00
Testing/Data Acquisition 92
123
$920.00
$850.00
$1,230.00
Sensor Calibration 85 46
$460.00
System Integration 90
104
$900.00
$1,040.00
Operation Manual 60
$815.00
$820.00
$5,020.00
$4,755.00
$5,280.00
Total
$8,830.00
$8,438.00
$9,020.00

48. Earned Value Analysis

49. Earned Value Analysis Schedule Variance BCWP-BCWS -$392
Behind Schedule
Cost Variance
BCWP-ACWP
-$582
Over Budget
Cost Performance Index
BCWP/ACWP
Schedule Performance Index
BCWP/BCWS

50. Conclusion/Lessons Learned
We spent more hours on the project than anticipated.
The system integration and debugging consumed most of our time.
We tried to make the system as simple as possible.
The assumptions can be wrong for the same component made by different supplier and buffers for this should be accounted.
Ask for expert help sooner.

51. References
Dynamics of Flight, Stability and Control; B. Etkin, L. Reid. John Wiley and Sons, 1996
Aurzkai et al. ImAP Fall 2007

52. Appendix

53. Euler angle rates:
p,q,r are angular rates measured by the rate gyro in the body frame. To transform into the inertial frame, we utilize the transformation matrix, T. We run this through RK4 and produce the desired angles, and thus the payload attitude.

54. Acceleration on a point b with respect to CM on an arbitrary object.

55. Tilt Calculations Vout = Output of Accelerometer
Voffset = 0g offset of Accelerometer
1g = Earths Gravity
= Angle of tilt

57. Hardware 3 MLX90609 1-axis Gyroscope 1 ADXL330 3-axis Accelerometer
1 GB SD Card
1 Atmel Mega 128 Processor
1 Logomatic SD Data Logger
Various Electrical components (resistors, capacitors, etc)

58. Hardware: MLX90609: Gyroscope
Requirement:
Measure angular rotation to 300 degrees per second for each of the three principle axes(FR:01). Operational temperature: -40°-85°C(FR:06).
Reasons for choosing this part:
The MLX90609 is a 1 axes gyro that includes a breakout board for
evaluation purposes.
Measures 300 °/s which is not excessive and will not have resolution issues,
but also measures more than the required specifications.
Low Price: $59.95
The selling point of this gyro is the angular rate measurement and the temperature
range.
Rate Gyro
MLX90609
ADXRS150
IDG-300
Full Range
± 300 °/s
± 150 °/s
± 500 °/s
Noise Performance
0.03 °/s/√Hz
0.05 °/s/√Hz
0.014 °/s/√Hz
Sensitivity
0.006V/°/s
.001 V/°/s
0.002 V/°/s
Temperature Range
-40°-85°C
0°-70°C
Price
$ 59.95
$ 69.95
$ 74.95

59. Hardware: ADXL330 (Accelerometer)
Requirements:
Measures linear acceleration to 0.01g for each of the three principle axes(FR:02). Operational temperature: -40°-85°C(FR:06).
Reasons for choosing this part:
Includes a breakout board which will make the evaluation process easier.
Very low noise density: 280μg/√Hz rms
Very good sensitivity change due to temperature: ± 0.015%/°C
Non-linearity: ±0.3
Low Price: $34.95
Accelerometer
ADXL330
LIS3LV02DQ
MMA7260Q
Full Scale
± 3.6g
± 2g
± 1.5g
Sensitivity Vs Temperature
.015 %/°C
.025 %/°C
.03 %/°C
Non-Linearity
±0.3%
± 3%
± 1%
Price
$34.95
$43.95
$ 39.95

60. Hardware: Atmel Mega 128 Microprocessor
Requirements:
Power and weight
Reasons for choosing the part:
light weight
price
Microcontroller
Atmel mega 128
Pic 18 series
Throughput
16 Mhz
10Mhz
Flash program memory
128 KBytes
N/A
On chip RAM
4 KBytes
512 – Bytes
Price
$100
$129

61. Hardware: Logomatic Serial SD Data Logger
Requirements:
We needed some system that had the FAT system ready to use. There is a lot of code that has to be written to be able read anything legible from the SD card
Reasons for Choosing this Part:
Automatically logs incoming data from the UART (saves time, and power)
Comes with a lot of FAT16/32 code for free on Sparkfun.com (saves a lot more time)
Has a place holder for the SD card which saves spaces
An alternative was the DosOnChip ($44.95) board which also utilizes a FAT system , but it has really poor documentation and is unavailable indefinitely.
Price: $59.95