P11562 MIS Frame and Stabilization Module
Detailed Design Review
Rob Bingham
Matt Moore
Karen Smith
KGCOE MSD Technical Review Agenda
Meeting Purpose: Review and receive feedback for the design of P11562 Frame and Stabilization Module subsystems and overall design.
Materials to be Reviewed:
Needs/Specs
Subsystem Design
Risk Assessment
Bill of Materials
Preliminary Test Plan
Meeting Date: Feb 11th 2011
Meeting Location: 09-2255
Meeting time: 8:00 am to 10:00 am
Timeline:
Meeting TimelineStart time / Topic of Review
8:00 / Project Background
8:05 / Needs and Specs
8:15 / Stabilization System
8:35 / Impact Foam System
8:50 / Frame System
9:05 / Risk Assessment
9:15 / Areas of Concern
9:25 / Bill of Materials
9:30 / Test Plan
9:50 / MSD II Action Items
9:55 / Conclusion
Table of Contents:
Project Background………………………………………………………………………………………………………...4
Mission Statement…………………………………………………………………………………………………………..5
Subsystems…………………………………………………………………………………………………………………….5
Customer Needs……………………………………………………………………………………………………………..6
Specifications…………………………………………………………………………………………………………………6
Stabilization System………………………………………………………………………………………………………..7
Impact Foam System……………………………………………………………………………………………………..12
Frame System……………………………………………………………………………………………………………….15
Risk Assessment…………………………………………………………………………………………………………...19
Areas of Concern…………………………………………………………………………………………………………..20
Bill of Materials…………………………………………………………………………………………………………….20
MSD II Action Items………………………………………………………………………………………………………21
Appendix A: Test Plan…………………………………………………………………………………………………...22
Appendix B: Works Cited………………………………………………………………………………………………38
Project Background
Project Name: MIS Frame and Stabilization Module
Project Number: P11562
Project Family: Open Source / Open Architecture Modular Imaging System
Track: Printing & Imaging Systems
Start Term: 2010-2
End Term: 2010-3
Faculty Guide: Dr. Alan Raisanen
Primary Customer: CIS, Carl Salvaggio
Mission Statement
The Frame and Stabilization project's mission is to create a module interface for the UAV platform, standardize the camera mounting interface, design and implement the camera shock and vibration systems, minimize the module weight, and maximize the impact survivability.
Subsystems
Stabilization System – Reduces vibration of camera using a 3 axis shock mount system allowing camera to take clear images from the air.
Impact Foam System – Reduces G force felt by camera and components during impact allowing maximum survivability in case of an incident.
Frame System – Contains camera and components in a durable lightweight frame that fits in the cargo holding area of UAV C.
Customer Needs
Specifications
Stabilization System
Customer Need:
Isolate camera lens from engine propeller vibrations.
Specification Theory:
The specification for the damping material will be determined by the natural frequencies of the material, the camera lens, and the engine/propeller system. Therefore the ideal material can be determined through analysis of the natural frequencies of the camera lens and the engine/propeller system.
Specification Calculations:
Cruise speed of aircraft is typically 75% of the maximum speed of the aircraft.
The ideal natural frequency of the material would be an order of magnitude(1/10) less than the natural frequency of the engine at cruise speed. A marginal value for the natural frequency of the material would be half an order of magnitude (1/5) less the natural frequency of the engine at cruise speed.
Current Vibration Isolation System:
The material that is currently being used for the vibration isolation system is Sorbothane Shore 30 oo. The customer has stated that the current damping material is unacceptable because it allows for too much displacement of the camera lens during operation.
Calculations of Current System:
The mass of the camera lens, cross-sectional area of the shock mounts, and the thickness of the shock mounts are from the documentation of MSD P09561.
The Young’s Modulus of the damping material can be found at
Poisson’s Ratio of Sorbothane is assumed to be the same as similar materials (ie Polyurethane and Rubber)
Proposed Alterations:
In order to decrease the displacement of the camera lens during operation of the vibration isolation system, the stiffness of the damping material must be increased without increasing the natural frequency to a range that won’t allow proper vibration isolation. The natural frequencies of materials tend to increase as stiffness and shear modulus of the material increase (if the area, mass and thickness values are kept constant). In order to find the ideal material for the system, the previous equations will be used in reverse order to take the ideal natural frequency and calculate the ideal Shear and Young’s Modulus (G and E respectively).
Ideal Material Calculations:
The mass of the camera lens, cross-sectional area of the shock mounts, and the thickness of the shock mounts are from the documentation of MSD P09561.
Poisson’s Ratio of Sorbothane is assumed to be the same as similar materials (ie Polyurethane and Rubber)
If the Poisson’s Ratio was assumed to be 0.5:
A marginal material solution can be found using the marginal natural frequency that was previously found.
If the Poisson’s Ratio was assumed to be 0.5:
Conclusion:
The ideal material for this vibration system would have a Young’s Modulus between 225 [psi] and 270 [psi]. The strongest of the materials listed on the Sorbothane website (Shore 70 oo) has a listed Young’s Modulus of 206 [psi], it is possible that this material would be strong enough to reduce the camera lens displacement during system operation, however a stronger material would have a greater effect. The proposed solution is to use the Shore 40A (Shore 75 oo) rubber material found the McMaster-Carr website.
Graph:This graph shows the Dynamic Young’s Modulus for Sorbothane 30 oo, 50 oo, and 70 oo plotted with the frequencies at which those Moduli occur. There is a linear trend line plotted along the natural frequencies of the Sorbothane. The vertical line at 7.9 Hz represents the Ideal natural frequency of the material used as a solution. The red shaded areas represent the natural frequencies and Dynamic Young’s Modulus at which a material won’t properly dampen the system.
Impact Foam System
Specification:
Camera and components must survive a 20 G crash.
System must be lightweight.
Assumptions:
Free fall with no drag or aerodynamic forces (lift).
Ground surface is soil and grass (allows for greater travel on impact).
Theory:
G force is a measurement of acceleration given by the following formula:
where a is the acceleration in feet per second squared and g is the acceleration due to gravity which is 32.174 feet per second squared.
If the object were to fall from this maximum height the velocity of the object just before it hits the ground surface can be found using the following equation:
The acceleration can then be found using the following equation:
Where is the distance is the object travels once it hits the ground surface (crush zone). The greater the distance, the slower the acceleration. The G force felt by the object can then be found using the first formula.
The pressure can be found using the following formula:
This pressure force takes into account the mass and area of the objects surface that is hitting the ground surface. This pressure is used to pick out a foam material that will allow the object to decelerate over a longer distance. The object then experiences a smaller acceleration and has a higher chance of surviving the impact.
Experiment:
Two densities of foam were tested to determine the effect of foam type on the crush zone created. Large celled foam and small celled foam were tested from 1 to 6 feet and the results are as follows:
The small celled foam had less penetration which would allow for maximum crush zone for large impacts, but would not crush under lower impacts. The opposite is true for the large celled foam. The small cell foam tended to crack to absorb the energy rather than impact, which would pose a problem in a realistic scenario.
Analysis:
The maximum height of UAV C is 400 ft. If the camera were to fall from this maximum height the final velocity is 160.435 feet per second. A more realistic drop would be from a tumble or failure to land properly. This height is estimated as a maximum10 foot drop. The velocity in this case from 10 ft is 25.37 feet per second.
The G force acceleration from maximum (400 ft) drop with a crush zone of 4 inches is 100 Gs. The more likely scenario of a drop from 10 ft with a crush zone of 2 inches has an acceleration of 5 G’s. If the crush zone is .5 inches, then the acceleration is 20 G’s. So the minimum distance the camera would have to travel to feel a 20 G acceleration is 5 inches.
Each component has a shock rating that it is manufactured to survive up to. The camera has a shock resistance of 70 G’s and the circuit boards around 50 G’s. Knowing this, the camera and components will already survive a 20 G crash without any protection. From 400 feet it can be calculated that it would take an 8 inches crush zone to allow the components to survive the impact. This crush zone includes the balsawood frame of the aircraft, the indentation in the ground and the addition of foam padding.
This addition of padding will allow the components the maximum survivability from taller heights. The components will also not be falling like a rock as assumed in these worst case scenarios. There will be a drag force from the air slowing it down and unless the plan is completely destroyed, a small lift force will slow the fall as well.
To select a foam material the pressure forces were calculated on the camera component. At 20 G’s the pressure on the camera would be 1.72 psi and at 100 G’s the pressure would be 8.60 psi. Foam was selected on these pressure values. A combination of easy to crush foam and harder foam will allow the camera to be protected from high and low impacts.
Results:
Foam Choices:
Neoprene, Firmness (25% deflection) = 2-5psi
Polyurethane, Firmness (25% deflection) = .57psi
Frame System
Background:
The frame design that was chosen was designed to withstand an impact from the maximum flight altitude. A partition was created to divide the frame into two sections. One section will contain the camera lens and the other section will contain the camera’s components. This partition will protect the camera lens from potential damage cause by the components assembly in the event of a crash. The top of the frame is designed to open and close to allow easy installation of all components. The frame material selected is Al 6061-T651. This has a yield strength of 40 ksi.
Figure 1: Frame Design
Analysis:
The worst case scenario force was calculated to be 1500 pounds. This was applied to the frame in two different ways. In the first case, the 1500 pound load was applied to the side face of the frame. This yielded a minimum factor of safety of 1.2, a maximum displacement of 0.06793 inches, and a maximum stress of 33 ksi. These results are shown in Figures 2-4.
Figure 2: Factor of Safety Results with 1500 lb load on entire face
Figure 3: Displacement results with 1500 lb load on entire face
Figure 4: Stress results with 1500 lb load on entire face
The second case was applying the same maximum force of 1500 lb on one edge of the frame system. The 1500 lb load was applied at 45°. This case resulted in a factor of safety of 1.0, a maximum displacement of 0.12 inches, and a maximum stress of 33.3 ksi. These results are shown in Figures 5-7.
Figure 5: Factor of Safety results with 1500 lb load applied at 45°
Figure 6: Maximum displacement results with 1500 lb load applied at 45°
Figure 7: Stress results with 1500 lb load applied at 45°
Details of Frame:
All faces of the frame will be CNC machined. These pieces will then be welded together. The top portion will be connected with hinges.
Material: Al 6061-T651
Dimensions: 15.75” x 5.75” x 5”
Weight: 2.54 lb
Risk Assessment
Areas of Concern
Stabilization System:
- Material chosen too stiff not allowing proper dampening of vibration
- Material chosen too soft allowing a larger camera displacement then desired
- Testing equipment availability
Impact Foam System:
- Foam material properties vague
- Proper protection of camera: soft vs hard foam
Frame System:
- Long lead time on CNC machine
- Extra time to make prototype frame
Bill of Materials
MSD II Action Items
Build Phase
Order Parts and Materials
Machine frame parts
Weld frame parts
Build Frame Structure Prototype
Build Frame Structure
Assemble foam
Change dampeners on existing vibration isolation system
Build vibration test stand
Test Phase
Create Final Test Plan
Vibration Testing
Impact Testing
Interface Testing
Total System Specs Testing
Presentation
Technical Paper
Make MSD Poster
Make presentation for Imagine RIT
Final Project Review
EDGE website
Miscellaneous
Create Meeting Schedule
Regular Updates with guide
Appendix A:
P11562 MIS Frame and Stabilization Module
Preliminary Test Plan
1. MSD I: WKS 8-10 Preliminary TEST plan
1.1. Sub-Systems
Major Sub-Systems/ Features/ Function
1 Interface
2 Total System Specifications
3 Impact Protection
4 Vibration Dampening
1.2. Test Results
Interface Test
Subsystem: Interface
Date Completed:______
Performed By:______
Tested By:______
Engr. Spec. # / Specification (description) / Unit of Measure / Marginal Value / Ideal Value / Comments/StatusES2 / Interfaces – All parts must interface with each other as well as the camera system and UAV / Proper Fit / Everything Fits / Everything Fits
Total System Specifications Test
Subsystem: Total System Performance
Date Completed:______
Performed By:______
Tested By:______
Engr. Spec. # / Specification (description) / Unit of Measure / Marginal Value / Ideal Value / Comments/StatusES3 / Total System Weight – System must be less than 15 pounds / lb / 15 / <15
ES4 / Total System Volume – System must fit inside UAV and allow room for camera system / inch / 15.75x5.75x5 / 15.75x5.75x5
Impact Survival Test
Subsystem: Impact Protection
Date Completed:______
Performed By:______
Tested By:______
Engr. Spec. # / Specification (description) / Unit of Measure / Marginal Value / Ideal Value / Comments/StatusES6 / Impact Isolation - The frame and components must survive a 20 G or greater shock. / G / 20 / >20
Vibration Test
Subsystem: Vibration Dampening
Date Completed:______
Performed By:______
Tested By:______
Engr. Spec. # / Specification (description) / Unit of Measure / Marginal Value / Ideal Value / Comments/StatusES1 / Mechanical Isolation / Hz / >75 / >50
ES5 / Withstand Atmospheric Conditions – System needs to withstand varied atmospheric conditions / Degrees F / -20 to 120 / <-20 to >120
1.3. Test Equipment
Engr. Spec. # / Instrumentation or equipment not available (description)ES1 / Vibrations Lab Computer and Stabilization block
ES2
ES3
ES4
ES5 / Oven, Freezer
ES6
Interface Test
Date Completed:______
Performed by:______
Specifications Tested
Engr. Spec. # / Specification (description) / Unit of Measure / Marginal Value / Ideal Value / Comments/StatusES2 / Interfaces / Everything Fits / Everything Fits / Everything Fits / All parts must interface with each other as well as the camera system and UAV
Revision History
Revision / Description / Date1 / Document Created / 2/8/2011
Equipment
_____Assembled Frame (prototype)
_____ Stabilization Assembly
_____Components Assembly
_____UAV (with wing removed)
_____Layered Foam Material
Sections
- Part 1 Component Interface
- Part 2 UAV Interface
Part 1 Component Interface
Date Completed:______
Performed by:______
_____1. Place Stabilization Assembly into Frame and verify proper fit.
_____2. Place Components Assembly into Frame and verify extra room provided on all sides.
_____3. Remove Components Assembly.
_____4. Place layers of foam into frame.
_____5. Place Components Assembly into frame.
_____6. Place foam around sides and on top of masses.
_____7. Verify foam fits properly around Components Assembly and Stabilization System.
_____8. Close lid and ensure it is properly latched.
Sign off on section before continuing:______
Part 2 UAV Interface
Date Completed:______
Performed by:______
_____1. Place latched frame assembly into UAV.
_____2. Place foam around sides and on top to make frame fit tight.
_____3. Verify proper fit of the frame.
Sign off on section before continuing:______
Impact Survival Test
Date Completed:______
Performed by:______
Specifications Tested
Engr. Spec. # / Specification (description) / Unit of Measure / Marginal Value / Ideal Value / Comments/StatusES6 / Impact Isolation / G / 20 / >20 / The frame and components must survive a 20 G or greater shock.
Revision History
Revision / Description / Date1 / Document Created / 2/6/2011
Equipment
_____Assembled Frame (prototype)
_____Accelerometers
_____ Rectangular Mass1 - represent components box
_____Rectangular Mass2 - represent camera and stabilization platform
_____Layered Foam Material
Sections
- Part 1 Frame Impact Survival
Part 1 Frame Impact Survival
Date Completed:______
Performed by:______
_____1. Place layers of foam into frame.
_____2. Place masses with accelerometers attached into frame.
_____3. Place foam around sides and on top of masses.
_____4. Replace lid and secure.
_____5. Place accelerometers on frame.
_____6. Drop starting from lowest height and record in chart.
_____7. Verify that components are below g force rating at 20 G impact.
Height (ft) / G force on Box / G force on Mass1 / G force on Mass21
2
3
4
5
6
7
8
9
10
Height at which 20 G is felt on box
Height (ft) / G force on Box / G force on Mass1 / G force on Mass2Max height for component survival
Height (ft) / G force on Box / G force on Mass1 / G force on Mass2Sign off on section before continuing:______
Total System Specifications Test
Date Completed:______
Performed by:______
Specifications Tested
Engr. Spec. # / Specification (description) / Unit of Measure / Marginal Value / Ideal Value / Comments/StatusES3 / Total System Weight – System must be less than 15 pounds / lb / 15 / <15
ES4 / Total System Volume – System must fit inside UAV and allow room for camera system / inch / 15.75x5.75x5 / 15.75x5.75x5
Revision History
Revision / Description / Date1 / Document Created / 2/9/2011
Equipment
_____Assembled Frame (prototype)
_____ Stabilization Assembly
_____Components Assembly
_____Layered Foam Material
Sections
- Part 1- Total System Weight
- Part 2 - Total System Volume
Part 1 - Total System Weight
Date Completed:______
Performed by:______
_____1. Place Stabilization Assembly, Components Assembly, and Foam Material into Frame.
_____2. Place the Assembly on scale and verify that the total weight is less than or equal to 15 pounds.
Sign off on section before continuing:______
Part 2 - Total System Volume
Date Completed:______
Performed by:______
_____1. Measure the length, width, and height of the Frame Assembly.
_____2. Verify that the Frame is 15.75" x 5.75" x 5".