Team Vision for Detailed Design PhaseOur team goal for this phase was to finish detailed design before the end of the semester. We focused primarily on the leg and tail subsystems with a secondary focus on waterproofing, intermediate structures (spine, hips, shoulders), and RC.
We have mostly settled on a final design and all critical components have been selected. We have begun a bill of materials which we will flesh out as we continue to finalize component specifications. A few things are still in flux though, like the final torso dimensions.
Feasibility: Prototyping, Analysis, Simulation
Leg Motor Selection
We had a hard time finding motors that met all of our specifications, but we did find a continuous rotation servo motor that meets all of our design specifications besides being waterproof. We will order one to start and verify that it works and that we are able to successfully waterproof it before ordering the rest. The specs for the motor can be found here
In order to save money on servos we looked into different mechanical designs to have a leg with a joint be moved by one servo. We found the Theo Jansen walking machine and used it as a basis for a new leg design.
It was then 3D printed and tested to make sure it would work in real life. The only issue is that the design requires a 360-degree servo in order to work and after exhaustive research, there are none available with the torque we need that are also waterproof. This meant that the only option was to manually waterproof the servo so we tried it out with some cheap servos we already had. We tried different sealants but overall the waterproofing was a success so we are moving forward with this design. The continuous servo was ordered and will be waterproofed and tested upon arrival and in the meantime the CAD is done.
Drawings, Schematics, Flow Charts, Simulations
This is the full hip design assembly that will hold both the tail and the legs.
Bill of Materials (BOM)
Currently these are the required materials for purchasing. A budget increase request form will be eventually presented to the client, if necessary.
- Waterproof servo has passed all testing including short duration tests over a 2 weeks span and a 24 hours under water test
- Once the tail has been assembled and glued together it will be tested in water with the single servo we have to ensure it will provide enough torque.
- Once the waterproof servo passes our test we will order a second to be able to test the full tail motion in water with both servos
- A test setup will be created by mounting the servo that would normal be mounted on the body to a floating raft. This will allow us to see if the motion we planned will provide enough thrust in the water.
Design and Flowcharts
RC Transmit and Receive Design
To implement an RC Controller for our Robotter, we need to understand how the controllers communicate with an Arduino. RC Controllers typically communicate on various channels, at 2.4GHz. Each channel corresponds to a different operation on the physical controller. For example channel 1 may be a joystick and channel 2 may be a button. That signal is transmitted from the controller to a receiver, with a matching number of channels. Many controllers fortunately come with a matching receiver. The receiver will take the signal, at 2.4GHz, and then output a converted digital signal to the Arduino. The Arduino can then map the receiver's signal to values that correspond to something the servos understand. The figure below outlines how the RC Transmit and Receive would work in the system.
Risk AssessmentNo changes were made to our risk assessment during this phase.
A working copy of our risk assessment can be found here.
Design Review MaterialsOur Design Review Slides can be found here
Plans for next phaseA working copy of our project plan can be found here.
- As a team, where do you want to be in three weeks at your next review?
- As an individual on the team, what are you doing to help your team achieve these goals? (Use the individual 3-week plan template for this)