P07521 BRDF Imaging Platform Concept Review 19 Jan 2007

Team Members

Project Description

Needs Assessment

Specification Table

Function Generation (brainstorming)

Function Decomposition (our flow chart)

Benchmarking TASE system

Benchmarking Askman AP system

Camera Stabilization System

Customer Needs 15x15 pixel area on target at all times 50-70 degree angle from horizontal on target Keep the system nearly level while imaging Robust enough to prevent damage of equipment

Concept Generation Active Gyro Passive Gyro Dampened Joint Model Airplane Gyro Floating Compass System Model Airplane Gyro/Dampened Joint

Pugh’s Matrix

Askman AP system

Kenyon Labs Passive Gyro

Model Airplane Gyro

Concept Selection Dampened Joint with airplane gyro is preferred Airplane gyro will be purchased if budget allows

Data Storage System

Customer Needs Store images as .TIFF files Log GPS coordinates with each picture taken Time stamp on pictures to know when it was taken

Concept Generation Serial RS-232 Compact Flash Flashdisk

Pugh’s Matrix

Pictures Compact Flash Flashdisk Serial RS232 to USB

Concept Selection Customer prefers both options Will add removable media if budget allows Customer has a serial to USB converter if removable media is too expensive

Batteries

Customer Needs Self contained power Battery life = flight time Easy access to battery

Specifications Battery current Battery voltage System to withstand temperatures

Concept Generation Concepts Solar Battery – only feasible choice Wind Nuclear Fuel Fuel Cell

Pugh’s Matrix

Concept Selection NiCd used as reference – most common NiMH cheaper and as good as NiCd Size and discharge rate were issues Li-Ion better power, lifespan, performance Higher cost Li-Polymer very small size and weight Lead Acid is unstable and friggin huge

Pictures Ni-Cd Li-Ion Li-Poly NiMH Lead Acid

Pan Tilt Assembly Motor Selection

Motor Selection Pan Tilt Assembly Evaluated four different types of motors: AC Motors DC Motors Servo Motors Stepper motors Each was evaluated for the specific criterion of this project Torque available Speed Reliability Repeatability of results

Pugh’s Matrix

AC Motors Pros: Cons: Very rugged and simple Wound – rotor AC motors have controllable speed and torque Cons: Don’t have AC current available for UAV Do not have the longevity and reputation of DC motors in precision/positioning applications Good for constant speed applications

DC Motors Pros: Cons: Very easy to control Very high torque is possible Very high speeds are possible Cons: Most efficient as high speeds so a gearbox is needed Brushes can and will wear out after time Switched DC motor can be jerky at low speeds and do not have the torque of standard DC motors

Servo Motors Pros: Cons: Excellent for high dynamic requirements Continuous duty for high speed and torque requirements Delivers continuous power at high speeds (12000 RPM) Cons: Requires a feedback loop Without and encoder inertia can carry the rotation beyond what is desired Expensive and can be complex

Stepper Motors Pros: Cons: Require no position feedback Small in size and highly accurate Easy to program High torque low speed applications under 2000 RPM Cost effective and economical Cons: Can skip steps when overloaded Can become bulky at high torque

Pictures DC Motor AC Motor Servo Stepper

Motor Selection A Stepper motor will best fit this project Excellent positioning accuracy Two members of the group have previous experience with this application Can be easily interfaced with the existing hardware Is a highly cost effective solution Will produce the necessary skew rate Will not “skip” steps if proper motor selection is used Stepper will be controlled by a Basic STAMP to the PC104+ board

Sketch

Future Work