The design of the Personal Automated Lawn Mower shall include the following high-level requirements:
High-Level Requirements:
- The user shall be able to teach the mower which sections of the lawn to mow.
- The mower shall be able to successfully mow a predetermined section of the lawn without further help from the user.
- The mower shall actively charge by using the attached solar panel to extend battery life.
- The mower shall be able to return to the docking station once it has 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 |
| Microcontroller | Raspberry Pi 3B+ | Must be able to 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 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. The controller also must be able to monitor speed, direction, and cutter speeds. Verification:Controller will verify GPS and sensors are active. If a 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 the solar charging kit, batteries, motors, and electronics. Must have enough room to hold all components and allow the cutter blade 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, and electronics within, and a cutter blade, drive motors, and battery on the bottom. Verification:Aluminum construction frame and metal track gears will be able to support the weight. | Group |
| Solar Panels | 12V 10W Flexible Monocrystalline | Must be able to charge batteries both while docked and while the mower is moving. Must be able to charge a 12V battery source. Must weigh less than 1 kg | Justification:The battery must be able to be recharged within 8 hours of direct sunlight. Verification:Solar Panel test will be checked before installation and the microcontroller will verify battery charge before use. | Group |
| Blades | Stainless Steel | Must be lightweight and durable. 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 a high current drain. | Brian |
| Battery | 12V 6Ah LiFePo4 | Must be able to fit in the 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:The battery pack must fit within the allotted space on the unit and be able to provide more than the required voltage and current. The battery must be able to power the unit for at least 45 minutes at a time. Verification:The microcontroller is able to display power available from the battery. | Brian |
| Object Detection Sensor | Bumper Sensors | Must be passive and not have an excessive drain on batteries. | Justification:Sensors will close a signal loop and notify the microcontroller that an object is in the mower’s path. Verification:sensors will be 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 lawn mower 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, the mower will turn on the cutter mower while docked and verify current drain is within specifications without a load. | Brian |
| GPS | Ardusimple simpleRTK2B | Must have RTK Base station and Rover communication capability. Must be able to communicate with multiple satellites and provide 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 the overall cutting area. Verification:Upon startup, the mower will calculate and send real-time adjustments between the mower GPS unit, Docking Station GPS unit, and satellites. | Group |
Docking Station
| Part | Specific component | Engineering Specification | Justification & Verification | Responsibility |
| Solar Panel Kit | 12V 10W Polycrystalline | Must be able to charge batteries while the system is running. Must be able to charge a 12V battery source. | Justification:The docking station will have vital electronics necessary to provide real time corrections for GPS accuracy. Verification:The charging system will have a voltage controller that will display the supplied voltage and voltage of the battery. | Brian |
| Inductive Charge System | 12V inductive charge coils | Must be able to transmit voltage and current without a physical connection. | Justification: System is to help increase battery recharge rate. Verification:Tests will be done to verify power transfer. | Brian |
| GPS | Ardusimple simpleRTK2B | 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 the overall cutting area. Verification:Upon startup, the mower will calculate and send real-time adjustments between the mower GPS unit, Docking Station GPS unit, and satellites. | Brian |
Controller
| Part | Specific component | Engineering Specification | Justification & Verification | Responsibility |
| Microcontroller | Raspberry Pi 3B+ | Must be able to communicate with the microcontroller on the mower for programming and directional controls Must be able to provide real time controls for manual movement. | Justification:The controller will allow the user to program and give manual controls. Verification:When the mower is set to program mode, the mower and controller will connect. | Gabriel |