Launching Station for Sensor Deployment
Dr. Jeff KozakProject Supervisor
/ Dr. Wayne Walter
Robotics Mentor
/ Dr. Ferat Sahin
EE Mentor
/ Brian M. Molnar
Project Manager
Shawn McGrady
Mechanical Engineer
/ Joseph Liquore
Mechanical Engineer
/ Kenneth Schroeder
Mechanical Engineer
/ Michael Shahen
Consultant
Midterm Design Review
Submitted on:
February 21, 2003
10:15AM
Submitted to:
Dr. Jacqueline R. Mozrall
Professor and Department Head of Industrial and Systems Engineering
Dr. Jeff Kozak
Professor of Mechanical Engineering, Project Supervisor
Dr. Vincent Amuso
Professor of Electrical Engineering
Mr. Mark Smith
Industry Representative
Table of Contents
Review and Preview4
1Executive Summary...... 4
2Nomenclature...... 5
3Figure Number and Location...... 6
1Introduction7
1.1Motivation ...... 7
1.2Product Description ...... 8
1.3Scope Limitations ...... 8
1.4Stake Holders ...... 9
1.5Critical Performance Parameters ...... 9
1.6Previous Research in Sensor Deployment ...... 10
1.7Budget ...... 11
1.8Markets ...... 11
1.9Order Qualifiers ...... 11
1.10Order Winners ...... 11
1.11Background Literature Review ...... 12
1.12Mission Statement ...... 14
2Theory15
2.1Sensor Aerodynamics ...... 15
2.2Wind Effects ...... 18
2.3Mass Effects on Sensor Range ...... 19
2.4Stress in Pressurized Vessels ...... 22
3Design and Analysis25
3.1Brainstorming Session ...... 25
3.2Compressed Air Concept ...... 27
3.3Spring Concept ...... 28
3.4Wheel Drive Concept ...... 29
3.5Rubber Band Concept ...... 29
3.6Feasibility Assessment ...... 30
3.7Preliminary Design ...... 33
4Results and Discussion34
4.1Barrel Wall Thickness ...... 34
4.2Finite Elements Analysis of Barrel ...... 35
4.3Wind Sensor Resolution ...... 37
5Final Design39
5.1Pneumatics ...... 39
5.2Wind Sensor...... 43
5.3Bolt, Barrel, and Receiver ...... 46
5.4Sensor ...... 52
5.5Sensor Encapsulation ...... 52
5.6G.P.S...... 54
5.7Angle of Launch Actuation ...... 56
5.8Initial Budget ...... 58
6Conclusion60
6.1Project Wrap-up ...... 60
Bibliography63
Appendices
AModification of Needs Assessment
BRe vs. Cd for a Sphere
CSensor Range Spreadsheet
DSpecifications of G.P.S.
EHand Sketched Drawings of Concepts
FCAD Drawings
Review and Preview
1Executive Summary
This Midterm Design Review details the design process for a Launching Station for Sensor Deployment. The launching station will operate remotely via a currently existing robotic base. A Global Positioning System mounted onto the robot will allow for the operator to accurately position the launching station as well as keep track of launched sensors. A wind sensor will be mounted on top of the launching station that will detect wind magnitude and direction. With this information fed into the processing unit on the robot, the launch trajectory can compensate for initial wind conditions, for a more accurate placement of sensors. Deployment of only one sensor would not be an efficient utilization of the area on the robot, therefore a holding device for yet to be launched sensors must also be designed.
Dimensions and weight will be in the forefront of the team’s mind when designing any components for the launching station. There is a limited amount of space in which all components must be placed and must also be light enough as not to damage any of the sensitive electrical components below. The following pages explain the complete design process starting at the product description and ending with the final design.
2Nomenclature
...... Drag Force
...... Coefficient of Drag
...... Air Density
...... Sphere Projected Area
...... Velocity
...... Reynolds Number
...... Reynolds Number Characteristic Length
...... Sphere Diameter
...... Viscosity
...... Force
...... Mass
...... Acceleration
...... Gravitational Acceleration
...... Vertical (y-axis) Acceleration
...... Horizontal (x-axis) Acceleration
...... Horizontal (x-axis) Displacement
...... Vertical (y-axis) Displacement
...... Time
...... Drag Constant Simplifier
...... Radial Stress
...... Tangential Stress
...... Yield Stress
...... Internal Pressure
...... Outer Pressure
...... Inner Radius
...... Outer Radius
...... Radius
...... Total Pressure
...... Free Stream Pressure
...... Change in Pressure
3Figure Number and Location
1Introduction
1.6.1A Design of a Launching Station for Microrockets...... 10
1.11.1Smart Dust Module...... 13
2Theory
2.3.1Flight Trajectory: Velocity 32ft/s, Angle 45 degrees ...... 20
2.3.2Horizontal Displacement: Velocity 32ft/s, Angle 45 degrees ...... 20
2.3.3Flight Trajectory Velocity 32ft/s, Angle 25 degrees ...... 21
2.3.4Horizontal Displacement Velocity 32ft/s, Angle 25 degrees ...... 22
3Design and Analysis
3.1.1Initial Brainstorming Results ...... 25
3.1.2Brainstorming Results After Voting ...... 26
3.1.3Brainstorming Results with Majority of Support ...... 27
3.1.4Distribution of Concepts for Initial Sketches ...... 27
3.6.1Radar Plot of Feasibility Assessment...... 32
4Results and Discussion
4.2.1Barrel With 0.05-inch Mesh ...... 35
4.2.2Barrel With Boundary Conditions ...... 36
4.2.3Barrel With Applied Internal Pressure ...... 36
4.2.4Tangential Stress in the Barrel ...... 37
5Final Design
5.1.1Pneumatics Flow Chart ...... 43
5.2.1Wind Sensor Assembly ...... 44
5.2.2Omega Pressure Sensors ...... 45
5.3.1Isometric View of Barrel ...... 47
5.3.2Isometric View of Bolt ...... 48
5.3.3Isometric View of Connector ...... 49
5.3.4Isometric Views of Receiver ...... 49
5.3.5Isometric View of Magazine ...... 50
5.3.6Receiver Assembly in Position 1: Reloading...... 51
5.3.7Receiver Assembly in Position 2: Ready to Fire...... 51
5.4.1Transponder used for Sensor ...... 52
5.5.1Sensor Assembly ...... 54
5.6.1G.P.S. Receiver ...... 55
5.6.2G.P.S. Antenna ...... 55
5.7.1Spur Gears ...... 57
5.7.2Worm Gears ...... 57
5.8.1Initial Budget ...... 58
6Conclusion
6.1.1Model of Prototype to be Built ...... 60
6.1.2Spring Quarter Schedule ...... 61
1Introduction
1.1Motivation
As technological and scientific knowledge increases there are new products that are created that tend to be smaller, less expensive, and require less human interaction. Smart Dust is the latest and smallest new development that fits this trend. The overall size of a Smart Dust Module is anticipated to be no larger than 1mm in any direction. With a specific sensor onboard, a Smart Dust Module could measure anything from temperature and humidity to nuclear and chemical residue. This lends the use of these modules to civilian use, but the most widespread use will most likely be by the military.
With today’s concerns over chemical and nuclear warfare, a device that is almost invisible to the eye that is capable of measuring the chemical composition of a remote location and transmitting the data back to a safe location would have a great deal of appeal to the military.
Sensors like mentioned above would be of little use alone. If a Smart Dust Module 1mm in size were launched into the air it would soon settle to the ground. To overcome this wings can be added to the sides of the cube. This allows the modules to float in the air like maple or dandelion seeds. Sensors launched into the air could stay up in the air for days before falling to the earth. In order to get the Smart Dust up into the air a launching station is needed.
The need for a launching station has been debated since the advantages are not well known. Launching sensors in a systematic method over a large area over a battlefield, or area of concern, would allow for virtually invisible surveillance for days. Not all of the applications are limited to military purposes. Sensors deployed over a wildfire or in a weather system would provide valuable information on the intensity, changes and movement of these systems. A more immediate use for the launching station that will be described in this report is to deploy miniature robots, or tethered sensors. A 10mm fully functional robot has been built and is currently undergoing testing at the LACOMS department at R.I.T. These robots could carry small cameras with the ability to travel down pipes or get into small crevices in a debris field.
A launching station does not have to be mounted exclusively on a robotic base. The launching station would be much more robust if it could be installed on a variety of buildings and vehicles such as: military vehicles, police cars, fire trucks, and airplanes.
1.2Product Description
As research and development of millimeter sensor continues, there is an ever-growing need for a device that can accurately launch sensors. Previous research suggests that microrockets, that were initially designed to deploy sensors, are too erratic in flight to effectively and accurately deploy these sensors. Theory suggests that a sensor that is launched from a base station and contains no thrust capabilities onboard should have a much more predictable flight path.
Since the launching station will be placed on a robot, the size and weight of the components must be kept to a minimum. Future teams will pick up where this project leaves off and continue to reduce the size of projectiles that can be launched. This will continue until the launching station can effectively launch 1-2mm sensors. At this point the launching station can be marketed to organizations such as the Department of Defense.
1.3Scope Limitations
The design of the launching station must be complete by February 21, 2003. A presentation of the design will be given to a review panel that must include the following:
- Complete CAD Drawing Package
- Bill of Material with initial budget
- Preliminary design documentation (Design Planner Notebook)
- Design Review Document detailing design process
The prototype and initial testing must be completed by May 16, 2003. Another presentation will be given to update the review panel on the progress at that time. The following must be included:
- Complete Prototype
- Documentation stating what prototype testing was conducted
- Final budget
- Complete design documentation (Design Planner Notebook)
- Design Review Document detailing design process
1.4Stakeholders
The major stakeholders in this project are the team members and the faculty advisors associated with it. Another major stakeholder is the Mechanical Engineering Department whom is funding the project. Future senior design teams and graduate students working on sensor deployment will benefit from what is completed in this project.
1.5Critical Performance Parameters
The minimum required performance parameters are the features that the launching station must include for the project to be deemed a success. The minimum required performance parameters are listed below.
- Launching station shall rest on a remotely controlled vehicle.
- Launching station shall be able to traverse over smooth ground and relocate based on remote inputs.
- System shall have G.P.S. to translate location to base station.
- Launching station shall be no larger than 12” x 12”.
- System shall have onboard wind sensors that automatically reposition the launch trajectory of sensor deployment based on wind conditions observed.*
The desired performance parameters are features that are not required for successful completion for the project and would be nice to have, time permitting. The desired performance parameters are listed below.
- System should have self-contained power supply.
- System should have load capacity to carry at least 20 additional sensors.
- Launching station should be as small as possible
- Launching station should be able to operate in atmospheric conditions ranging from 0°C to 50°C.
*Note:See Appendix A for an explanation of updated made to the critical performance parameters
1.6Previous Research in Sensor Deployment
Previous work on sensor deployment at the Rochester Institute of Technology has concentrated on using a microrocket that is powered by an onboard power supply. Figure 1.6.1 shows an example of one design of a launching station for microckets. These microrockets were found to be instable and hard to control. By encasing the sensor in a protective cover and giving it in an initial velocity at a launching station, the flight path should much more predictable.
Figure 1.6.1A Design of a Launching Station for Microrockets
1.7Budget
The Mechanical Engineering Department has provided a budget of $2,000 to fund this project. The budget must cover the following expenditures:
- Raw Materials
- Off the shelf components
- Electrical engineering/technician support
- Wind Tunnel calibration equipment
1.8Markets
The Primary markets for the launching station are:
- R.I.T. Mechanical Engineering Department
- LACOMS Laboratory for Autonomous, Cooperative Microsystems
- Military monitoring/surveillance
Secondary Markets include, but are not limited to:
- Weather monitoring
- Wild fire monitoring
- Other monitoring/surveillance agencies
1.9Order Qualifiers
The team shall design, build, and test a prototype launching station that can launch a 0.5–inch sphere 10 to 30 feet away from it. The launching station must rest on a remotely controlled vehicle, have integrated G.P.S., and include a wind sensor capable of measuring wind direction and velocity.
1.10Order Winners
Bells and whistles that would be nice but are not critical to the project include:
- Completely wireless operation
- Strong enough to stand impact if dropped from aircraft
- Onboard tracking device for all deployed sensors
- Overall size less than a 6-inch cube
- Ability to operate in atmospheric conditions ranging from 0°C to 50°C.
1.11Background Literature Review
One of the main motivations for the launching station is Smart Dust deployment. Smart Dust is a very small-computerized sensor that is capable of sending information from air borne particles. The size of Smart Dust has been decreasing rapidly due to increases in MEMS technology. The original contract for Smart Dust was for space applications. A Smart Dust module in space could monitor temperature and other conditions. They could serve as an early warning system for satellites in the earth’s orbit by warning of extreme temperatures or hazardous chemicals.
Researchers at the University of California at Berkley have built a prototype the size of a matchbox that is capable of measuring temperature, humidity and barometric pressure. Smart Dust can be used for military applications, weather monitoring, or to monitor the movements of insects and small animals and any situation that would be too dangerous for humans. The sensors have the ability to transfer information for a period of several days; in the future the sensors could have the capability of sending pictures and data. Figure 1.11.1 shows an illustration of a Smart Dust module.
Figure 1.11.1Smart Dust module
This project is not the first to attempt to build a mechanism to deploy Smart Dust Modules. The University of California at Berkeley and the Rochester Institute of Technology have both conducted research projects in sensor deployment. Both of these efforts focused on microrockets. A microrocket is a 10mm to 20mm long rocket powered by solid propellant. The microrocket has a small nozzle where it generates thrust as well as where it is ignited. The microrockets would be able to carry 5-10 Smart Dust Modules in the nose cone or on external storage bays.
When microrockets were manufactured and tested there arose problems with the stability of the system. The flight pattern was very erratic if they lifted off. Fins were added to the external sides of the microrocket to try and improve stability, but the flight path and accuracy of final landing position were never accurate enough for use as sensor deployment devices.
1.12Mission Statement
The goal of the Launching Station for Sensor Deployment Team is to design and build a fully functional prototype capable of launching a 0.5-inch diameter sphere. The design and prototype will be a proof of concept for sensor deployment. This concept will be utilized by future research projects at the Rochester Institute of Technology as well as other universities.
2Theory
2.1Sensor Aerodynamics
The first section of theory will focus on the aerodynamics of the sensor during flight. A key factor in the deployment of the sensors is their aerodynamic qualities. In order to accurately deploy the sensor to a location up to 30 feet from their initial launch point, any aerodynamic effect on the sensors must be predetermined and thus compensated for prior to its launch. Since the launch platform is designed to deploy various types of sensors, which may or may not carry the same aerodynamic characteristics, the idea was to encapsulate the sensors in one-half inch diameter spheres. This reduces the number of aerodynamic factors that need to be compensated for, as well increases the universality of the launch platform.
The spherical shape was chosen due to its advantages versus other projectile shapes, most notably in the area of drag. Drag in general is the resistance force placed upon the projectile by the medium for which it is passing through, in our case air. Ideally any fired projectile will travel in a parabolic path; however with the presence of drag the projectile will follow a more truncated path thus decreasing its overall range. The drag force is typically expressed by Equation 2.1.1 from Shevell, 1989:
2.1.1
The drag coefficient represented by “CD” is a dimensionless parameter, which represents the complex relationships between drag, the projectiles shape and its various flow characteristics. The object shape has the most significant effect in regards to the force of drag exerted upon it. For a sphere the drag coefficient typically varies between 0.07 and 0.5. This large variance is as a result of the sphere’s significant dependency on Reynolds number. Reynolds number is dimensionless number that represents the ratio of inertia forces to viscous forces. For sphere the type of flow can vary significantly based on its velocity. With this in mind, in order to calculate the drag on our sensor we have to determine the Reynolds number for our half-inch sphere by means of the means of Equation 2.1.2 from Shevell, 1989:
2.1.2
Once the Reynolds number is determined we can determine the sphere’s drag coefficient by looking up the value on a previously developed graph representing their relationship. This graph can be seen in Appendix B.
Another advantage for a sphere is that its projected area remains constant in flight, unlike an oblique shaped object, which can have the tendency to tumble in flight thereby causing changes in drag. A sphere however can spin in flight causing it the curve in a given direction depending on the type of spin imparted upon it. This comes as a result of the changes in the fluid flow very close to the surface of the sphere creating a force in a given direction. This effect is most commonly known as the “Magnus Effect”. For the purpose of deploying our sensor we can neglect this effect, since the short range and accuracy for which we wish to obtain limits its influence.
Knowing the drag effects on the sensor allows us to calculate the range the sensor will travel based on its initial velocity and launch angle. However the process is complicated since the drag is proportional to the square of the objects velocity. Since the velocity in both the horizontal (x) and vertical (y) directions change over time, as a result of a deceleration from drag and both an acceleration and deceleration from gravity. Given Newton’s second law we can determine the accelerations or decelerations affecting the sensor in flight. Newton’s second law is as follows from Serway, 1996:
2.1.3
With gravity and drag acting in the vertical direction we can resolve Newton’s second law for the vertical instantaneous acceleration to the following:
2.1.4
As for the instantaneous acceleration in horizontal direction in relation to the drag force the second law can be resolved as:
2.1.5