The design of the Personal Automated Lawn Mower shall include the following high-level requirements:
High-Level Requirements:
- The user is able to teach the Mower which sections of the lawn to mow.
- The Mower is able to successfully mow a predetermined section of the lawn without further help from the user.
- The Mower actively charges by using the attached solar panel to extend battery life, and is able to return to the dock once its done mowing.
Mid-Level Requirements:
- The Mower is able to automatically avoid obstacles in the yard using sensors.
- The Mower remembers the mowing path for future use.
Low-Level Requirements
- The Mower provides at least 45 minutes of mow time.
- The Mower is fully recharged with the dock.
These requirements outline the project’s design and implementation standards.
Requirements and Specifications:
The P.A.L.M. provides automatic maintenance of the users lawn with the only contact required being the initial setup of the mower. The engineering specifications table shows the project’s requirements and product specifications. These specifications ensure ease of use for the user as well as an automatically recharging and deploying system to ensure the lawn is constantly being maintained.
Engineering Specifications
Mower
| Part | Specific Component | Engineering Specification | Justification & Verification | Responsibility |
|---|---|---|---|---|
| Micro Controller | Raspberry Pi 4 | Must be able run off a 12V DC power source Controls motor and directional controls to determine where to move and what is left to cut. Must be able to detect at least 3 safety and detection sensors. Must be able to use a GPS and compass antennas to determine global position. | Justification: Needs to be able to apply custom code and respond to GPS, sensor, and pre-mapped paths. Controller also must be able to monitor speed, direction, and cutter speeds. Verification: Controller will verify gps and sensors are active. If pre-mapped path is not created a new path will be generated by the code or user input. | Gabriel |
| Car Kit | Robot Smart Car Chassis by XiaoR | Must be able to support the weight of solar charging kit, batteries, motors, and electronics. Must have enough room to hold all components and allow cutter to move freely. Must be able to traverse multiple terrains and ground conditions. | Justification: The frame is capable of carrying the solar panel on top, batteries and electronics within, and cutter mower on the bottom. Verification: Aluminum construction frame and metal track gears will be able to support the weight. | Group |
| Solar Panel Kit | TBD | Must be able to charge batteries both while docked and while mower is moving. Must be able to charge a 12V battery source. Must weigh less than 1 kg | Justification: Battery must be able to be recharched within 8 hours of direct sunlight. Verification: Solar Panel test will be checked before installation and microcontroller will verify battery charge before use. | Group |
| Blades | TBD | Must be lightweight and easily replaced. Must be able to cut grass efficiently | Justification: The cutter blades must not tax the cutter motor and can be easily replaced if damaged. Verification: A test run of the motor will be run to verify that the cutter mower is not experiencing high current drain. | Brian |
| Battery | ML9-12 – 12 V 9 Ah Rechargeable SLA Battery – Mighty Max | Must be able to fit in designated assembly frame. Must be able to provide 9V power to motors Must be able to provide at least 45 minutes of run time. | Justification: Battery pack must fit within the alloted space on the unit and be able to provide more than the required voltage and current. Battery must be able to power the unit for at least 45 minutes at a time. Verification: Microcontroller will have a voltage test code program to verify that the battery voltage is within 95% of the stated voltage (12 V). | Brian |
| Object detection sensor | MUZHI SPDT 1NO 1NC Momentary Hinge Metal Roller Lever Micro Switch | Must be momentary and sealed to the environment. Must be passive and not drain batteries. | Justification: Momentary switches will close a signal loop and notify the microcontroller that an impact has occured. This will allow the impact sensor system to operate with no power drain under optimal conditions. Verification: Switches will be mechanically tested and verified that they are in working order. | Gabriel |
| Blade Motor | 775 Motor | Must be able to spin cutter blades at 2000 rpm minimum Must be durable and resilient enough to take impact Must be able to run on a 12V DC source. | Justification: Most commercial lawnmower blades spin at 3000 rpm, but grass can still be cut with a 2000 rpm motor. This will allow for better power efficiency and still allow the blades to cut through most grasses and weeds. Verification: Upon startup, mower will turn on cutter mower while docked and verify current drain is within specifications without a load. | Brian |
| GPS | U-Blox ZED F9P | Must have RTK base station and Rover communication capability Must be able to communicate with multiple satellites and proved real time corrections for accurate pathing Must have at least 3cm of positional accuracy. | Justification: Since the mower will be GPS driven, accurate positioning will be required to be at least 5% of overall cutting area. Verification: Upon startup, mower will calculate and send real time adjustments between mower GPS unit, Docking Station GPS unit, and satellites. | Group |
Docking Station
| Part | Specific Component | Engineering Specification | Justification & Verification | Responsibility |
|---|---|---|---|---|
| Solar Panel Kit | TBD | Must be able to charge batteries while system is running. Must be able to charge a 12V battery source. | Justification: Docking station will have vital electronics necessary to provide real time corrections for GPS accuracy. Verification: Charging system will have a voltage controller that will display the supplied voltage and voltage of the battery | Brian |
| Micro Controller | Raspberry Pi 3 | Must be able run off a 12V DC power source Must be able to use a GPS and compass antennas to determine global position. | Justification: Needs to be able to run RTK GPS system for real time corrections for mower. Verification: Controller will verify GPS and sensors are active. | Gabriel |
| GPS | U-Blox ZED F9P | Must have RTK base station and Rover communication capability Must be able to communicate with multiple satellites and proved real time corrections for accurate pathing Must have at least 3cm of positional accuracy. | Justification: Since the mower will be GPS driven, accurate positioning will be required to be at least 5% of overall cutting area. Verification: Upon startup, mower will calculate and send real time adjustments between mower GPS unit, Docking Station GPS unit, and satellites. | Group |
Controller
| Part | Specific Component | Engineering Specification | Justification & Verification | Responsibility |
|---|---|---|---|---|
| Bluetooth controller | TBD | Must be able to communicate with the micro controller on the mower for programming and directional controls Must be able to provide real time controls for fine tuning programs | Justification: Controller will allow user to program and give fine tuning to cutting path Verification: When mower is set to program mode, mower and controller will connect. | Group |