P19229: Robotter
/public/

Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

Our team goal for this phase was to begin detailed design with a focus on high risk subsystems. We focused primarily on the leg and tail subsystems with a secondary focus on waterproofing, intermediate structures (spine, hips, shoulders), and RC.

We have settled on a final design for tail and have narrowed down to 2 potential leg designs. We have begun a bill of materials which we will flesh out as we continue to finalize component specifications.

Prototyping, Engineering Analysis, Simulation

Iterative activities to demonstrate feasibility, including assumptions you made in your analyses or simulations. Have you completed sufficient analysis to ensure that your design will satisfy requirements? Have you included all usage scenarios in your modeling?

Feasibility: Prototyping, Analysis, Simulation

Leg Motor Torque Feasibility

To better reflect our actual designs, the leg torque calculations were revised to a 2 degree of freedom model.

We used Section 2.1 of this paper as a basis for the model.

Two Degree of Freedom Leg Model

Two Degree of Freedom Leg Model

By plugging in our rough parameters we can calculate a projected worst case torque for each joint:

Joint Projected Torque (kg-cm)
Hip 22.9
Knee 12.8

The code used can be found here.

Alternate Leg Design

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.

Theo Jansen leg design

Theo Jansen 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 means that we will need to manually waterproof the servo. We plan on trying it out with a cheap servo we already have so we do not destroy the expensive one. If this fails we will go back to the original design of moving the leg with two normal servos.

Theo Jansen leg design prototype

Theo Jansen leg design prototype

Drawings, Schematics, Flow Charts, Simulations

CAD Model of Tail Assembly

CAD Model of Tail Assembly

A waterproof servo will be placed inside the rear housing and will provide the torque needed to move the tail from side to side. This side to side motion will generate thrust allowing the Robotter to swim.
Full CAD Model of Tail Assembly

Full CAD Model of Tail Assembly

The above shows the full tail assembly. This will be connected to the body via the shaft that will couple to a servo that will be mounted on the rear of the body.
Full CAD Model of Body

Full CAD Model of Body

This shows the CAD assembly of the ribs and spine. Eventually the tail and legs will be attached to it via 'hip' and 'shoulder' pieces (still being designed).

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.

Full Current Bill of Materials

Full Current Bill of Materials

Test Plans

Tail Testing

Design and Flowcharts

Control design continous Leg Motor

Control design continous Leg Motor

Control design Stepper Leg Motor

Control design Stepper Leg Motor

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 Trasnmit and Receive would work in the system.

RC Trasmit and Receive

RC Trasmit and Receive

Risk Assessment

We have not yet been able to decrease the projected likelihood of any of our risks but hope to be able to do so by the end of this semester. We added an additional risk with respect to how our bearings will behave when submerged in water.
Current Risk Assessment

Current Risk Assessment

A working copy of our risk assessment can be found here.

Design Review Materials

Our Design Review Slides can be found here

Plans for next phase

Individual Plans
Jacob Huppe
Ian Kay
Jonathan Travers
Drew Meunier
Chris Ugras
Mia Garbaccio

Home | Planning & Execution | Imagine RIT

Problem Definition | Systems Design | Preliminary Detailed Design | Detailed Design

Build & Test Prep | Subsystem Build & Test | Integrated System Build & Test | Customer Handoff & Final Project Documentation