Week 17 - Applications and Implications
This week's assignment requires us to plan a final project masterpiece that integrates the various units we have covered. The project is expected to incorporate 2D and 3D design, additive and subtractive fabrication processes, electronics design and production, embedded microcontroller interfacing and programming, and system integration and packaging.
Work log
Completed tasks
- Define the scope of a project.
- Develop a project plan including a schedule and a bill of materials (BOM).
- Tracked the progress of my project.
- Summarised and communicated the essence of my project development.
1. What will it do?
My final project is a mobile robot that utilizes transformable wheel-legs for movement across various surfaces and employs RTK localization. The wheel-legs are equipped with independent linear actuators that enable them to switch between an open and closed state. In the closed state, the wheel-leg spokes contact the surface, allowing the robot to navigate rigid terrains. Conversely, the open state positions fin-ray appendages directly on the surface, facilitating movement over loose surfaces. Additionally, the robot is equipped with a Raspberry Pi AI camera for video transmission and carries RTK equipment for precise centimeter-level localization.
2. Who's done what beforehand?
The Biorobotics Center, under the leadership of Dr. Roger Quinn at Case Western Reserve University, developed wheel-leg robots. Dr. Robert Siddall researched the use of Fin-ray spokes for robot locomotion while at the Max Planck Society. During my master's studies, I worked with transformable wheel-legs. For RTK navigation, I drew inspiration from the Smart Rover developed by Drone Dojo.
3. What sources will you use?
I will reference the datasheets for the Raspberry Pi Zero 2W, Raspberry Pi AI Camera, Raspberry Pi Pico 2, Attiny 1616, DRV8871, MP1584, ESP32C6 chip, and the UM980 and UM982 RTK modules. For software, I will consult the documentation pages for Python 3 and the Centipede project.
4. What will you design?
I will design a body frame for the robot that encases all components to prevent cables from tangling with objects. Additionally, I need to create the PCBs to interface with the Raspberry Pi Zero 2W, Raspberry Pi Pico 2W, Attiny, and RTK equipment. I have already manufactured fin-ray spokes using 3D printing; however, I also plan to experiment with moulding and casting processes to create fin-ray appendages. This will allow me to utilise both additive and subtractive methods in my design. FabLab Ibero Puebla already has an RTK base station.
5. What materials and components will be used? Where will they come from? How much will they cost?
Mechanical components
| Item | Quantity | Details | Cost per unit ($) | Source |
|---|---|---|---|---|
| Hyper PLA (1Kg spool) | 2 | Used for the main structural components. | 25.94 | Amazon |
| TPU-95HF (1Kg spool) | 1 | Used for compliant appendages and wheel-leg pads. | 21.40 | Amazon |
| 3 mm x 30 mm aluminum bars 10 piece package | 1 | Used as a guiding element for the linear actuators. | 15.22 | Amazon |
| Aluminum couplers 4 piece package | 1 | Used for connecting the PLA wheel-legs to the DC motor metallic shaft. | 12.55 | Amazon |
| M3 PCB Copper Spacers package | 1 | Used for separating the upper and lower PCBs. | 17.58 | Amazon |
| 3 x 18650 Battery holder | 1 | Used for holding the batteries that power the entire system. | 3.47 | Amazon |
| 12-volt Micrometal DC motor with encoder | 4 | The motor torque should be 2.2 kg x cm in order to fully move the system. | 5.53 | AliExpress |
| 12-volt Micrometal DC motor with M3 x 30 mm worm screw with hexagonal nut. | 4 | This motor is used for the linear actuators and ideally should have a torque of 2.2 kg x cm. | 13.24 | Mercado Libre |
| Limit switch sensor | 8 | This sensor is used to detect the position of the linear actuators. | 0.23 | Unit Electronics |
| M2 screw package | 3 | These screws are used to secure the limit switch sensors, camera, and Fin-ray appendages in place. | 10.64 | Amazon |
| M3 screw package | 5 | These screws are used to secure assembled the wheel-legs and PCBs into the robot structure. | 13.38 | Amazon |
| M2/M3/M4/M5 screw package | 1 | This package contains enough M5 screws to assemble the structure of the robot. | 28.05 | Amazon |
| 9 mm ball bearings 10-piece package | 1 | These bearings are used to facilitate wheel-leg rotation. | 11.68 | Amazon |
| 3 mm ball bearings 20-piece package | 1 | These bearings are used for holding the linear actuator guidelines | 14.98 | Amazon |
| 2 mm ball bearings 5-piece package | 4 | These bearings are used to hold the end on the linear wormdrive | 1.01 | Aliexpress |
| 3 mm linear ball bearings 4-piece package | 1 | These bearings are used to hold the end on the linear wormdrive | 17.81 | Amazon |
Electronic Components
| Item | Quantity | Details | Cost per unit ($) | Source |
|---|---|---|---|---|
| Raspberry Pi Zero 2W | 1 | Used for video streaming, telemetry and control over wi-fi. | 91.08 | Amazon |
| Raspberry Pi AI Camera | 1 | Used for video streaming. | 153.89 | Amazon |
| Raspberry Pi Pico 2 | 1 | Used for sending commands to motor drivers and Attinys. | 20.90 | Amazon |
| MP1584 Buck converter | 3 | Used for regulating the voltage supply on the different PCBs. | 3.45 | Amazon |
| Attiny 1616 | 2 | Used for controlling linear actuators. | 1.33 | Mouser Electronics |
| DRV8871 | 8 | Used for driving the DC motors of the robot. | 5.12 | Mouser |
| SMD electrolytic capacitors package | 1 | Used for the DRV8871 driver. | 21.30 | Amazon |
| SMD ceramic capacitors package | 1 | Used for the DRV8871 driver. | 15.14 | Amazon |
| 1206 SMD electronic components package | 1 | Contains resistors and voltage regulators. | 15.14 | Amazon |
| Male and female pin header connectors bundle package | 1 | These connectors serve as the physical interface between the PCBs. | 10.31 | Amazon |
| Terminal block 50-piece package | 1 | These terminals allow connection between the PCBs and the battery. | 10.19 | Amazon |
| Dupont jumper connector package | 1 | These connectors are useful for fabricating compact cables. | 18.77 | Amazon |
| 4 18650 3.7V 9A battery package | 1 | These batteries serve as the power supply for the robot. | 11.68 | Amazon |
| ESP32 Development Board | 1 | This board serves as the link between the RTK module and the Raspberry Pi Zero 2W. | 8.98 | Amazon |
| UM982 | 1 | This module allows for RTK positioning. | 125.45 | Aliexpress |
| RTK Antenna | 2 | This antenna helps the module recieve RTK signals. Two antennae are required for position and direction. | 33.43 | Amazon |
| 22 AWG wire (1 meter) | 5 | This wire is for sharing energy between PCBs. | 0.29 | Amazon |
Total cost: $989.51 USD
6. What parts and systems will be made?
- Body frame: A sturdy frame to house all components and prevent cable tangling, manufactured through 3D printing.
- Molded Fin-Ray Appendages: Appendages created through moulding and casting processes.
- PCBs: Custom printed circuit boards will be needed for the Raspberry Pi Zero 2W and the Raspberry Pi Pico 2W, along with Attinys, DRV8871 drivers, and RTK equipment. All PCBs will be designed using a modular approach.
7. What processes will be used?
- PCB milling
- 3D printing
- Resin 3D printing
- Moulding and casting
8. What questions need to be answered?
- PCB milling
- 3D printing
- Resin 3D printing
- Moulding and casting
9. How will it be evaluated?
The project will be evaluated using the following criteria:
- Wheel-leg transformation: The wheel-legs must effectively transition between their different states. Each linear actuator must generate a force that exceeds the gravitational pull on the robot's weight.
- Video transmission and telemetry: The robot must consistently transmit video streaming and IMU data.
- RTK positioning: The robot should maintain constant awareness of its position while navigating an open field.
Reflection
Doing this assignment helped me realize how much someone would need to spend to build a robot similar to the one I am developing. While I am fairly certain that not every item in the packages I listed will be used, it is safe to assume that individual components are hard to find. Therefore, I decided to list packages that contain the necessary items.