P18229: Robotic Otter/public/
Preliminary Detailed Design
Team Vision for Preliminary Detailed Design PhaseOur team goal for this phase was to prototype and simulate subsystems and concepts that have a high risk. In this phase, we performed three main tasks.
- First, we prototyped the spine using at-hand materials and 3D printed parts. Then we simulated moving the spine using only the "wire/cords".
- Second, we practiced making silicone. This was to better understand the best method to make silicone parts with as little flaws as possible.
- Lastly, we made a more detailed design of our robotic otter and modeled it in CAD.
Prototyping, Engineering Analysis, Simulation
Spine PrototypingWe prototyped the spine as it is the core system within our robot. We want this spine to be able to bend significantly; however, the math to determine the force required to do so is not well defined. To spec our motors, we needed to know how much torque they needed to provide. We took our prototype spine, attached a force gauge, and measured the force required to bend the spine 90°, the maximum bend desired for our robot. During the experiment, we noticed two important things; the natural bend in the tube is a significant factor in characterizing the tube's ability to bend, and the tube has the potential to buckle within the range we are considering.
- Tubing Kinks
- Possible Solution: Filling tube with material like silicone, stiffer tube, or sealed air.
- Tube naturally curves in one direction
- Possible Solution: Heat and re-shape tubing.
- Maximum force of 5N
- Design Consideration: Choose a motor with a FOS 5x the maximum force.
Silicone Part Casting
Drawings, Schematics, Flow Charts, Simulations
- A tube (hollow/filled) will be used for the base of the spine. The 3d printed vertebrae will be slid onto the tube with silicone bushings in between all of the vertebrae. Fishing line will be threaded through all of the vertebrae and connected to DC motors in order to induce torque which will flex the spine, that will create movement.
- Legs will be be either 3D printed or machined parts. The legs will be attached directly to Servos motors that are embedded into the large vertebrae. Within the knee and ankle joint, there will be torsional springs that will conform to the environment that the otter is traversing. When the leg is lifted off of the ground, it will return to its original position.
- Electronics will be placed where the vital organs would be located in an actual otter. Either a box or bladder will house all of the electronics in order for the components to remain dry.
- Rings will be integrated into the spine in order to create a profile for the body. They will be small (thin) and rigid so that the shape of the body will remain when the otter is moving through the water as well as on land.
- Skin will be created from a silicone based polymer. It will either be made from Dragonskin or Ecoflex. Sheets of this material will be created and combined in a manner that will allow the internal components to remain dry when in use.
- The head of the otter will be 3D printed ABS. It will also be 3D printed in order to create an accurate representation of an otter skull.
Bill of Material (BOM)The current bill of materials for our robot can be seen below. Note that this is just a pure bill of materials; the budget is still not finalized, as the primary things we need to purchase, the motors, have not yet been specified. We are in the process of deciding the requirements for these items. here. The working budget can be found here.
Test PlansAs we move ahead in the detailed design, it is imperative that we proceed with certain goals in mind. The following preliminary test plans will allow us to stay focused and mold our design around the goals we must accomplish.
Design and Flowcharts
A full list of our working risk assessment can be seen here: Risk Assessment
Plans for next phaseThe primary goal for the next phase is to finish prototyping the crucial components so that we are prepared to start our build come the second semester. We also want to focus on ensuring that we have all of the documentation for our processes and simulations that we have done to date. here.
Individual Three Week Plans