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Team Vision for System Level Design Phase
The System Level Design phase focused primarily on the generation of design concepts and the solidification of high-level implementation details of those concepts. The work done in this phase forms a bridge between understanding the problem at hand and the design of a solution for that problem. Beyond Concept Selection and high-level architecture design modelling, feasibility analysis was performed on both the concepts and the problem at hand. The Problem Definition phase opened more questions than it answered by the time it was finished, and so answers to those questions of scope and others were explored.
Systems Level Design Goals:
- Develop multiple design concepts based on the CRs and ERs and the various tools provided in the systems level design phase modules.
- Subtract and operate
- Function Trees
- Transformation Diagrams
- Analyze the feasibility of the developed concepts.
- Develop selection criteria based on CRs and ERs to help filter through the concepts.
- Construct a Pugh chart based on the selection criteria
- Identify potential rules, regulations and safety standards that need to be considered in future development and testing.
- Develop high level systems level flow charts to describe basic connections and concepts.
Updated Use Cases
The use cases which were created during the Problem Definition phase were concerned with operational modes and failure modes. In this phase, the team found that those use cases did not sufficiently constrain and define the problem at hand. In an effort to avoid feature creep, three use cases which will be tested against were selected by the customer and developed by the team.
Flooded Area
In the use case of flooded areas, the drone is expected to operate in flood like conditions while gathering data in mostly suburban areas.
Night Time Search Operations
Night time operation will have to adjust for the lack of light and the fact that the visible light camera will no longer be as effective.
Lost Hiker (Daytime)
The lost hiker scenario will assume mostly wooded areas and lots of foliage, making direct line of sigh detection difficult.
Functional Decomposition
Subtract and Operate
| Part | Category | Functions | ||
|---|---|---|---|---|
Wing | Structural | Provides Lift | ||
| Ailerons | Feedback | Provides mechanical heading control | ||
| Prop | Transmission | Creates thrust | ||
| Motor | Transmission | Provides rotational energy to prop | ||
| Battery | Power | Main power source | ||
Frame | Structural | Provides stiffness | Provides strength | Protects electronics, other in event of crash |
| Skin | Structural | Provides optimal aerodynamics | Protects sensitive electronics inside from weather, wind, etc. | |
| Microcontroller | Control | Provides computerized control | Controls failure operation | Provides control system stabilization |
| Microcontroller mount | Structural | Keeps microcontroller cool | Protects microcontoller from turbulence, sudden impact | |
| Motor mount | Structural | Keeps motor cool | Minimizes vibrations to rest of frame | |
| Thermal imaging camera | Information | Provides sensor data for person location | Provides navigational aide | |
| Camera Gimbal | Structural | Minimizes vibration to camera | Holds camera in optimal data collection position | protects camera from sudden impact |
| Control Surface Servos | Control | Moves Ailerons/Elevators | ||
| Wing Tips/Stabilizers | Structural | Guides plane | Reduces severity of wing inconsistencies | |
| RF RX/TX | Control/Transmission | Provides telemetry to pilot | Provides emergency control | Provides emergency data dump |
| Casing | Structural | Protects inner mechanics | Designed to be aerodynamic | Holds things together for flight |
| Thermal Sensor | Information | Sense body heat | ||
| Memory Unit | Information | Stores the flight data | Hold recorded sensor data | Keeps location of people found |
| GPS | Information | Keeps track of drone location | Records location of person found | |
| Camera | Information | Takes picture of scenery and area below | Used to gather information for person detection | |
| Remote Control | Control | Control code to the drone during non-autonomous stage | Allows for communication between drone and pilot | |
| Antennae | Transmission | Allows for information transfer | ||
Each part listed in the subtract and operate function falls under four categories: structural, control, transmission, and information. Information includes parts that are mainly utilized for data storage and processing. Structural components include the parts that make up the physical frame the drone, such as drone casing and camera gimbal. Lastly, the control parts deal with maneuvering the drone and flight control.
Function Tree
Transformation Diagram
Safety Standards
| Standard | Details |
|---|---|
| ASTM F2909-19 | Standard to address minimum requirements for determining if a drone is continually airworthy |
| ASTM F2910-14 | Standard Specifications for designing and building small unmanned aerial systems |
| ASTM F3002-14a | Standard Specifications for designing control systems for small unmanned aerial systems |
| ASTM F3366 | Standard Specification for General Maintenance Manual |
| ASTM 3201-16 | Standard Specification for ensuring dependability of software used on UAS |
| NFPA 2400 | Small UAS for Public Safety |
| FCC Part 15 | 15.247.a3 RF on the 5.8GHz band |
| FCC Part 15 | 15.245 RF on the 2.4GHz band |
| FAA 107.12 | Requirement for a remote pilot certificate with a small UAS rating |
| FAA 107.29 | Daylight Operation. No persons may operate a small unmanned aircraft system during night. |
| FAA 107.51 | Operating Limitations. The groundspeed of a UAS may not exceed 87 knots (100mph). The altitude of the UAS cannot be higher than 400 feet above ground level (unless there are structures...) |
| FAA 107 | UAVs should weight less than 55 lbs |
| FAA 107 | Visual line of sight must always be maintained with pilot and drone |
Concept Development
Benchmarking
Drone Type Analysis
- Fixed wing drones and drones that are capable of switching are able to fly above 40 minutes at various price ranges.
- Small increases in flight time on a rotary drone costs significantly more money.
- Fixed wing drones are able to achieve a significantly greater flight time with lower battery capacity compared to rotary drones.
- It can be observed that rotary drones struggle to have a flight time above 40 minutes even for various battery capacities.
- SUI Endurance with a battery capacity of 9000 mAh only has a flight time of 40 minutes (and costs about $13500).
- No such plateau is observed for fixed-wing aircraft.
- There is a higher cost per minute to fly rotary drones than fixed-wing drones.
Flight Time Analysis
- It becomes extremely expensive to achieve long flight time.
- Price increases significantly as battery capacity increases.
Morphological Chart
Concept Selection
| Concept Component | 1 - Flex | 2 - Fixed | 3 - Rotary |
|---|---|---|---|
| Power | LiPo | LiPo | LiPo |
| Motor | Outrunner | -- | Outrunner |
| Propulsion | Open Prop | EDF | Open Prop |
| Take-off | VTOL | Spring-Assisted Launch | VTOL |
| Landing | VTOL | Parachute | VTOL |
| Lift | Wing | Wing | Rotary |
| Imaging/Sensing | Visible Light | Visible Light | Visible Light |
| Sensor Mounting | Gimbal | Underneath | Gimbal |
| Body Type | VTOL Fixed | Fixed | Rotary (3-4) |
| Crash Protection | Parachute | Parachute | Parachute |
| Steering | Elevons | Elevons | Thrust Vectoring |
| Data Storage | P2P Radio | P2P Radio | P2P Radio |
| Indicate Victim Location | Don't | Don't | Don't |
| Sensors for People | Visible Light | Visible Light | Visible Light |
| Construction | Foam | Aluminum | Carbon Fiber/Wood |
Pugh Chart
Microcontroller Selection
Benchmarking for Microcontrollers was done by comparing several different types of microcontrollers together. For ease of comparison, a color coordinated chart was created to compare the different features and decide which microcontroller had the most desired features. According to preliminary results, the MK64F12 stood out as the most desirable as it had the largest ROM, RAM, and number of UARTs. The only draw back with this microcontroller was its price point in comparison to the other devices; however, due to previous circumstances the team has access to several of these microcontrollers, making the price point negligible.
Motor Selection
| Selection Criteria | Description |
|---|---|
| Operating Voltage | Voltage at which the motor operates. |
| Weight | Lighter motors yield a faster change in speed; Heavier motors yield a slower change in speed. |
| Efficiency (g/W) | Thrust per power. The motor must be efficient throughout the range of operation. |
| Power | Batteries must be able to handle the power requirements of the motor. |
| Torque | Rotational force about an axis. Effects the time it takes the propeller to reach a desired speed. Higher torque motors are easier to tune. |
| Kv Rating | The negative of the torque constant. High Kv motors tend to be more efficient at high RPMS but at the expense of torque. High Kv motors tend to require more current than lower Kv motors to produce a certain torque. |
Motor selection criteria is highly dependent on the selected concept. The following all affect the operation of the motors:
- Frame Size
- Propeller Size
- Stator Size
As a result, no comparisons will be made at this stage.
Battery Selection
Battery Selection is highly dependent on concept selection due to the current draw requirements of the different models. The "C rating" of a battery is the main determinant of the battery's current draw capacity, and consequently, batteries with higher C rating cost more money. Once concept selection is completed and finalized, we will select appropriate batteries. Some of the criteria we are considering are:
- Series cell count
- Parallel cell count
- C rating
- Capacity
Updated Risk Management Plan
| Risk | Description | Risk Type | Likelihood (0-5) | Severity (0-5) | Importance (L x S) | Action(s) Taken |
|---|---|---|---|---|---|---|
| Overbudget | Budget is limited - no funding outside of team members and RIT | Resource | 3 | 5 | 15 | Avoid |
| Fabrication | Machine shop/Construct tools could be busy, or available building resources could be limited | Time | 3 | 3 | 9 | As soon as a preliminary design is settled upon, start to source materials and fabricate parts as they become finalized, not once all parts are finalized |
| Software (telemetry) | Telemetry is difficult, and difficult to debug. Significant technical challenge. | Technical | 3 | 3 | 9 | Start early, plan ahead for this challenge, since it will be necessary during testing. |
| Injury | Someone could be hit by the drone, or cut by the spinning prop | Safety | 2 | 5 | 10 | Have a designated drone spotter when testing, mark dangerous area on drone with labels, have a testing plan with steps clearly outlined to ensure personnel safety, only test drone in areas away from residential areas |
| Drone Protection | Effective crash mitigation tech may be expensive or technically difficult to implement, affect CR's and putting drone safety at risk | Resource | 4 | 3 | 12 | Choose a concept which has crash protection built in. Ensure pilots are trained before flying the real aircraft. |
| Efficient Wiring | Small problems in wiring and electrical design can become troublesome quickly. | Technical | 3 | 3 | 9 | Consider current flows, do initial testing. Overbuild subsystems likely to cause problems (engine power subsystem, for example). |
| Testing | A quick, accurate, and safe way to test drones is critical given that we cannot test on campus | Technical/Time | 5 | 4 | 20 | Choose a concept which we are capable of testing. |
| Flight Time | The drone should be able to maintain flight long enough to test fully and not worry about sudden loss of power mid-flight | Technical | 2 | 4 | 8 | Choose a concept for which we can optimize power consumption and therefore flight time. |
| Limited Number of Drones | Only so many testing drones can be constructed with budget constraints | Resource | 3 | 3 | 9 | We will only be able to build one drone, but we have two indoor aircraft that may be used as trainers. |
| Loss of Team Member | Reduced work capacity due to missing/absent team members. | Resource | 5 | 1 | 5 | Mitigation plan is to reduce our dependency on custom mechanical parts. (Ben is leaving) |
| Customer Redirection | A new customer is added, thus changing CRs | Time | 1 | 4 | 4 | Mitigated. At this point it is not feasible for the team to take on a new customer. |
| Customer Absence | No official outside customer is identified, leaving us with speculated CRs and little expert knowledge | Information | 5 | 2 | 10 | We have been continuing our design validation and analysis techniques. |
| Extended Winter | Inclement conditions make flight testing difficult | Time | 2 | 4 | 8 | Find resources where we can reserve indoor flying space, even if small. |
| Unexpected Roadblock | Unforeseen technical hurdle, miscommunication or serious bug not found in testing | Technical | 5 | 3 | 15 | Plan project. Break large tasks into smaller ones until they can not be broken down further. Ensure communications are clear and quick. |
| Team Communication | Wealth of information spread across platforms and people could create discrepancies in planning | Personal | 5 | 1 | 5 | Communicate in advance of personnel absences, after every meeting post in group chat what assignments were and the expected due dates so there is accountability |
Updated Engineering Requirements
Systems Architecture
Hardware Connections
Data Transmission
Power Subsystem
Software Flow
Phase 3 Preview
Gantt Chart
Team goals
For the next phase, we would firstly like to complete all necessary research including material and component selection, testing facilities and other subsystem research. Next, we would like to come to create at least a proof of concept of a frame designed as well as some prototyping data using FEA in ANSYS (mechanical engineers). As a team we need to come to a decision on electronics on board, select them and come up with a general layout of how they will be implemented (electrical and mechanical engineers). We would also try and order some parts so we can physically see any limitations our frame might have. Finally, we would like the computer engineers to start developing a plan on how this will be coded. The way we strive to achieve these goals are listed below.
Individual Goals
Atulya
- Speak with Dr. Kaputa about this UAV project, specifically about pattern recognition and possible testing options.
- Work with the team to determine exactly what sensors will be used.
- Talk to Gordon field house reps about possibly using the field house facilities for testing.
- Work with Piers, Andy and Sabrina to come to a consensus on which microcontroller to use.
- Determine which power supply to use, i.e. either two power supplies for motors and sensors, controller or modular power supply with multiple voltage outputs.
- Research and understand power management schemes.
Piers
- Look into sponsorships for sensors.
- Assist with any DevOps infrastructure.
- Research controls for both fixed wing and rotary drones.
- Research PhysX for simulations.
- Research design of debug infrastructure for embedded devices.
- Finalize the selection of motors.
Sabrina
- Assist with test/prototyping setup for software.
- Narrow down budgets for each component needed for the drone.
- Include budget plan for prototype components.
- Assist with simulation options and which options are most applicable in terms of realistic flight mechanics and physics while still maintaining feasibility for quick testing.
- Have a concrete selection for which microcontroller to use.
- Work with Piers and Andy to decide how many sensors can be feasibly purchased within budget.
- Figure out how much data needs to be stored for the duration of one flight (assuming that most processing will be done off board).
Mutahir
- Design Electronics Holder.
- Research and Design Emergency Release mechanism.
- Research build materials.
- Work with team to prototype different drone frames.
- Keep in mind electric components and sensor wiring needed.
- Prep drawings for next design review.
- Learn ANSYS for FEA analysis.
Ben
- Design Frame (SolidWorks).
- Use cardboard, wood, and 3D printing to prototype early release connectors.
- Use cardboard, wood, and 3D printing to prototype early frames for structural analysis.
- Work with team to prototype different drone frames.
- Prep drawings for next design review.
- Learn ANSYS for FEA analysis.
Andy
- Produce a good test-prototyping timeline. In summary, what supporting designs do we want to have ready to run, and by when? We will need to get going on some of this pretty soon in order to really understand our concepts.
- Reach out to nearby organizations for sponsorship. While at this point we are not interested in gaining an external customer, finding some interested persons who also have funding would be nice.
- Investigate options for simulation. There are several modifications to the popular game Kerbal Space Program which add realistic flight mechanics and physics. Qualities of real engines and wings can be added to the game with relative ease, which might make it worth looking at. ANSYS is likely a better overall solution, but it may be faster to set up this game in the short term.
- Explore places we can fly outdoors. Martin Road Park, North Hampton Park come to mind.
- Explore feasibility of different sensor options. Questions include "how much power draw?", "how far can it see?", "how much onboard processing is needed?", and others.
- Work with Ben and Mutahir on frame prototypes, specifically motor mounting options and propellers. I think I have a CAD model of the standard motor mount for outrunners somewhere.
- Look into gimbal options. These are traditionally quite expensive and involve a lot of motors or servos, as well as several PID feedback loops and complex vibration sensing.
- Work on ensuring everyone is on task and not overwhelmed. The weeks are getting shorter but the work is getting longer, so some facilitation will be necessary to minimize team-wide burnout and frustration.
- Finalize battery selection criteria, and select the battery or batteries that we intend to use.