Team Vision for System-Level Design PhaseDuring this phase, the team planned on benchmarking the separate subsystems and overall system for the instrumentation platform. The team accomplished these goals by creating a functional decomposition, which allowed for the outlining of important functions of the instrumentation platform. From there, benchmarking was done to help to identify possible solutions and concept options. First, other full-system High Altitude Ballon (HAB) projects were benchmarked to gain initial understanding of what has and hasn't worked well in the past. Then, individual component benchmarking were executed for NTSC cameras, HD cameras, reaction wheel motors, temperature sensors, pressure sensors, humidity sensors, LEDs for the ground recovery signalling system (GRSS) and buzzers for the GRSS to gain a better understanding of available options for each of the important components within our system design. A morphological chart and a Pugh chart were created to allow for easier selection of components for the subsystems and full system. More development was completed, which was done by executing multiple feasibility analyses through prototyping, simulation, and analysis. Overall six feasibility analyses were created to gain better understanding in regards to environmental testing chambers, data storage, buzzer selection, budget fulfillment, weight fulfillment, and power source selection. Flow diagrams for system energy flow, system information flow and system structure flow were created for the instrumentation platform with an emphasis on understanding flow conjunction with HABIP-COMMs. Then, a risk assessment was updated to allow for better understanding of possible future problems and for the ability to plan for the next phase. Finally, the future plan for the next phase is displayed with documents displaying each individual team member's estimated contributions for the next phase of the overall system design.
Problem Statement Recap
Here is a re-cap of our project statement.
- RIT SPEX performs high altitude balloon launches.
- An instrumentation platform is needed as a base system for these missions that will be executed in the future.
- There have been launches in the past (like the METEOR project, which is a past MSD team), but they were not completely successful and compared to our proposed design, lacked a lot of functionality.
- A fully functioning design
- Acquire and transmit sensor data, location information, and video stream.
- Store locally sensor data and HD video stream.
- Stabilized platform on z-axis via reaction wheel for video stream.
- Interface with GPS and transceivers
- Receive and execute ground commands
- The final design is in conjunction with the HABIP-COMMs team
Partner Team -- HABIP-COMMs
Reminder, we are working with the High Altitude Balloon Instrumentation Platform Communications Team (HABIP-COMMs). Their Systems Design page has other system concepts, thermal analysis, structure design and more information that applies to both teams.
Functional DecompositionTwo functional decompositions may be seen below. The first will outline the entirety of the instrumentation platform, including both the DAQCS and COMMS teams' functions. These are color-coded as specified in the figure. The second is specifically a functional decomposition created by the HABIP-DAQC team.
The active working document can be found here.
The active working document can be found here.
The following high altitude balloon projects were
observed due to their similarity to this projects goals.
The METEOR project was chosen due to it being the
previous instrumentation platform created at RIT. The MIT
project was chosen due to its simplicity and use of GoPro
cameras. The PiBalloon was analyzed due to a Raspberry Pi
being the main controller and the similarity between
sensors being used. The McGill HAB was observed due to
its implementation of a reaction wheel to stabilize the
balloon in one axis. While all of these projects prove to
be good examples, none of them have a combination of
everything that will be incorporated in our project. None
of these projects incorporate a high redundancy of
sensors, HD and VGA cameras and a reaction wheel.
The active working document can be found here.
Component Selection Benchmarking
Some of the main individual components within the system were benchmarked to gain better understanding on selecting the best part to fit this team's needs and desires.
Reaction Wheel Motor
The active working document can be found here.
A morphological chart may be seen below. This outlines different options for many of the team's needs for the instrumentation platform. In the next section, entitled "Concept Selection," six different systems are created from these rows.
The active working document can be found here.
Concept Selection and Development
The figures below show the screening and scoring matrices that were created from evaluating the six different possible systems. The screening and scoring matrices were based on several important system-level selection criteria:
- Power Consumption
- Data Quality
The screening matrix above show the overall systems measured against a datum of the team's choosing.
The scoring matrix above shows the weighted distribution of the selection criteria for each of the possible systems.
Feasibility: Prototyping, Analysis, Simulation
Environmental Testing Chamber Feasibility
BackgroundWhen assembling the instrumentation platform, testing will be needed to ensure that it will survive in the environmental conditions associated with a flight altitude of at least 100,000 feet. In order to do this testing, an environmental chamber, altitude chamber, autoclave, or another method of testing will be needed. The customer’s requirements are that the electronics are able to withstand the commercial temperature range.
Feasibility TestUpon discovering the need for a testing chamber, the environmental testing lab was found in Slaughter Hall on campus. This is a free testing location for students and has several possible chambers for use. They are also used for testing by other companies, but if scheduled ahead, students are able to test within the chamber. The picture below shows the inside of the testing lab. The white enclosed room shows the environmental testing chamber, which can cycle between -20 to 70 degrees C, as well as 0 to 95% humidity levels.
Also within this lab is a previous senior design project (P10229), which can be seen in the next picture below.
It is an autoclave with the following specifications:
These specifications were found in the group’s technical paper: http://edge.rit.edu/edge/Reports/public/2009-10/Technical_Papers/P10229_Technical_Paper.pdf. This autoclave can achieve high maximum temperature and pressures, which is beneficial to P17105. However, there are no specifications mentioned about how low the temperature can go as well. Another testing facility was found on RIT’s campus in the Center for Electronics Manufacturing and Assembly (CEMA, https://www.rit.edu/cast/cema/facilities-and-equipment-page). There were many different, smaller chambers, as well as vacuum chambers. There was a chamber there that also allowed for very quick cycling between two extreme temperatures, which is another necessary test that will have to be done.
ResultsSeveral testing chamber options were found and given to the team, which provides enough evidence of the fact that testing will be able to be done on any design that is prototyped for the high altitude balloon instrumentation platform. When needed, the team will decide which chambers would be best suited for each individual test.
BackgroundAll data collected during a mission, including sensor data and video/image data must be stored locally to a storage device. Digital storage devices are able to store high quantities of data quickly and efficiently. The most commercially available and reliable storage solution is NAND gated based memory. This memory technology has been proven to be low power, lightweight and has been steadily increasing capacity. Within NAND memory, there are many formats the memory can be housed and accessed. The three main technologies include SD (secure digital), eMMC (embedded MultiMediaCard), and SSD (solid state drive). These three packaged technologies will need to be analysed to ensure they will fall within weight, price, simplicity and storage constraints.
In terms of weight, the eMMC and SD technologies are much lighter in comparison to SSD. In terms of price, eMMC is the cheapest yet in the long run would cost more than an SD card due to the additional hardware that would be necessary to interface with it. SSD technology is the most expensive due to its high capacity. This leaves SD cards the most viable solution in terms of price. Ini terms of simplicity, SD cards and SSDs are very simple and easy to interface with compared to eMMC. In regards to storage capacity, SSDs have the most memory capacity but even SD cards can achieve up to 256 Gb of space, which is more than enough space in our application. After all this analysis, it is clear that SD cards are the most appropriate technology to use. The feasibility then becomes a question of storage space versus price. Given a 3 hour flight, the SD cards on board need to be able to store 4 independent HD video streams worth of data and acquired sensor data. In order to test this, the video resolution and frame rate will be assumed to be 1920x1080 at 30fps. Using a GoPro recording with the same parameters will give an estimate as to how much memory this configuration will consume. Using a Raspberry Pi Zero and a Raspberry Pi Camera Module V2, multiple video compression techniques will be experimented with to maximize image quality but limit data quantity.
Using a GoPro set at 1920x1080 at 30 fps, the output video (.mp4) consumed 225Mb of data per minute of video. Therefore, for three hours worth of video, approximately 40.5 Gb of data would be necessary. Using a Raspberry Pi camera, the default video is saved as h.264 format and consumes 100Mb of data per minute of video. Therefore, for three hours of video, approximately 18 Gb of data would be necessary. Both mp4 and h.364 would allow a feasible amount of memory (32Gb or 64Gb) to be used.
Buzzer Feasibility Analysis
BackgroundA buzzer is needed for the GRSS that would enable the users of the high altitude balloon to be able to find it after its descent. An approximate sound level was decided in the engineering requirements. The engineering requirement that matches to the buzzer is ER 5, which is based on the customer requirement CR 3. The buzzer sound levels specified here is a range of 60 to 85 dB, with a nominal level of 75 dB.
Feasibility TestA buzzer used by the Hot Wheelz team was found and used for testing. It is a Floyd Bell buzzer, with a siren alarm. The range of noise for this buzzer is 92 to 103 dB, depending upon the input voltage, which has a range of 5 to 15 VDC. It is also ASTM B117 Certified, IP 68 Certified, able to withstand exposure to salt spray for 300 hours, able to withstand vibration between 0 and 55 Hz, and can withstand water submergence and dust exposure. It is also able to operate within a temperature range of -20 to 65 degrees Celsius. The storage temperature is from -40 to 85 degrees C. This buzzer’s specification sheet may be found here: http://www.alliedelec.com/m/d/15a1b8158ec3c3902afaa6fbc6205c0d.pdf This buzzer was hooked up to approximately 5 V in order to listen to its alarm. It was extremely loud and would be able to be heard from quite a distance away. This would be more than enough for the GRSS to function. It was also a continuous siren, in comparison to other alarms available for approximately the same price.
ResultsThis buzzer is more than able to sound and alert passerby of its location. Due to its small size, it has been decided that a similar buzzer, at a lower dB range, would be acceptable for use on the instrumentation platform. Other buzzers may be found here: https://www.floydbell.com/choose/index.php?category=&alert_type=Beep+Tone&mount=&termination=&volume_control=&voltage=&voltage_type=&_submit=Search. These buzzers only beep, rather than having a continuous noise. Several buzzers have the ability to regulate the volume of the alarm. There are also various types of connectors available, including panel and PC mount.
Budget Feasibility Analysis
BackgroundThe cost for a high altitude balloon (HAB) mission is desired to be as minimal as possible while also providing a design that is robust, reliable, aesthetically pleasing and habits all functionality required. Most factors involved with quality for a HAB design are hard to quantitatively assess in terms of cost throughout the beginning stages. Some of these factors are testing and component selection. Various choices are available for testing the design and for selecting each individual component. In addition to this, there are added costs for parts that will fail during testing and for new part selection due to redesign at later stages.
Feasibility TestThe testing involved adding a cost to all parts already selected to provide a very good estimate. In addition to this, thorough research / benchmarking was embarked to provide good estimates for parts that haven’t been selected yet and for categories of cost that will be seen in later stages.
ResultsWith current estimates, there is around $300 still available in the budget to provide cushion for possible costs that come up throughout the design.
Weight Feasibility Analysis
BackgroundAccording to the FAA standards, the high altitude balloon is only able to hold six pounds without further approval through the correct governing body. With this weight limit comes the constraint for the instrumentation platform to be under six pounds, so that additional work does not need to be done in order to launch the high altitude balloon. With two teams working on this instrumentation platform, it was decided that the weight would be split in half, each team only allowed to weigh up to three pounds.
Feasibility TestFeasibility was completed for the weight through research and benchmarking, as well as weighing individual components already within possession of the teams. The table below shows the approximation of the DAQCS portion of the instrumentation platform.
ResultsIt can be seen above in the table that the approximated weight is 2.624 pounds. This places the current plan for the instrumentation platform underneath the FAA regulations. However, the team has a small buffer of approximately 12.5 %, or 0.375 pounds, in case of any values not being exact and underestimated. Therefore, if the team is careful and designs the system well, the instrumentation platform should feasibly be able to be within the three pound limit.
Power Source Feasibility
BackgroundThe best power source for a high altitude balloon (HAB) mission is a power source that is lightweight, low cost, and has a high energy capacity. Safety is also a major concern, as the power source needs to function in harsh conditions without damaging the HAB platform or the surrounding environment. The two main power sources used during HAB missions are batteries and solar cells. Batteries provide power from an “already stored” energy reservoir while solar cells convert sunlight (photons) to electrical energy “on the fly”. Various types of batteries (Lithium Ion, Lithium Polymer, NiMH, etc) and solar cells (GaAs, amorphous Silicon, etc) exist. These are two distinct types of energy storage technologies which need to be analyzed to determine the best fit power source for HAB missions.
The first feasibility test metric is the type of energy storage: “already stored” versus “on the fly”. Batteries provide a reservoir of energy which depletes over time while solar cells constantly provide energy as long as they are exposed in sunlight. In terms of energy capacity, batteries can provide more current on demand than solar cells. Batteries are also not limited to sunlight only operation, which is critical if a HAB mission is launched on a cloudy day. Finally, solar cell efficiency (which can be less than 20% under non-ideal photon angle of incidence) is a major drawback for a short duration mission of less than four hours. Analysis of the two types of power sources shows that from a raw energy standpoint batteries fit the power supply need. Batteries will be used as the power source for the HAB, with tradeoffs being mainly in the added payload weight.
Narrowing the power source scope to batteries still leaves multiple choices for the battery chemistry. The most common portable and rechargeable batteries available include NiCd (Nickel Cadmium), NiMH (Nickel Metal Hydride), Lithium Ion, Lithium Polymer, and reusable Alkaline. NiCd chemistry can be discarded for two reasons. First, the battery offers very low energy density, which results in a high capacity battery being large and heavy. Second, metals used in the battery are extremely toxic to the environment and if the battery case cracks internal fluids can leak out. Reusable Alkaline batteries can be discarded due to their extremely high internal resistance (potentially up to a few ohms) at lower operating temperatures, which reduces the system's usable capacity. This leaves NiMH, Lithium Ion, and Lithium Polymer batteries. All three of these chemistries have similar internal resistance over temperature. Lithium Polymer batteries are more readily available in higher rated current discharge and density packs thanks to the RC hobby market. A drawback to these batteries, however, is the need for low discharge protection circuitry to disconnect battery terminals at low states of discharge. Failure to do so can result in the battery being damaged (best case) to explosion (worst case). Finally, NiMH batteries are more available in lower capacity packs, but do not require protection circuitry for low current deep discharging where the risk of battery explosion is non-existent.
ResultsFrom the above feasibility analysis, it is clear that various battery technologies accel in certain applications based on the specific chemistry. Currently, the DAQCS subsystem requires three batteries (one for general system microcontrollers/components, one for reaction wheel power, and one for the GRSS). The GRSS system is a very low current draw system and is designed to be on in excess of 24hours. The system should use the entire capacity of a battery to extend life, which makes a smaller stand-alone NiMH battery the ideal choice. Both the general microcontroller system (sensor acquisition) and the reaction wheel draw much higher current loads. The reaction wheel, in particular, can draw much higher instantaneous currents during motor operation. These two systems will use Lithium Polymer battery packs with build in protection circuitry and hard-housings to protect the battery cells from impact.
Joint System Architecture
DAQC Specific System Architecture
Design Review Materials
Our presentation can be found here.
Our handout can be found here.
Plans for next phase
Preliminary Detailed Design Gantt Chart
The following is the gantt chart detailing the action items necessary for the Preliminary Detailed Design phase.
Sydney Kaminski's Three Week Plan: Sydney's Goals
Chris Schwab's Three Week Plan: Chris's Goals
Lincoln Glauser's Three Week Plan: Lincoln's Goals
Steven Giewont's Three Week Plan: Steven's Goals