Project Specifications System Level



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Overview

  • Overview

  • Subsystem Contributions

  • 208: Drive / Steer / Yoke

  • 205: Support / Electronics / Controls

  • Closing Comments

    • Results
    • Strengths & Weaknesses
    • Future of RP1






Transport 1kg Payload

  • Transport 1kg Payload

  • Robust = Withstand Tabletop Drop

  • Wireless Communication

  • Power Motors with a PWM Signal

  • Open Source & Open Architecture

  • Reflect Design of the RP Family

  • Modular Design for Multiple End Uses



Quantity

  • Quantity

  • Speed @ max efficiency

  • 38 in/s

  • Drop Test Repair Time

  • < 20 min

  • Battery Life

  • 1 hour +

  • Modular Design



Responsibilities:

  • Responsibilities:

    • Design modular drivetrain system
      • Multiple modes of motor operation
    • Design and build a robust drivetrain
  • Challenges of MSD II

    • Drivetrain friction losses
    • The need for a belt tensioner?
    • Machining knowledge inadequacy
    • Failing drop testing
    • Unforeseen assembly woes
    • Differences between analytical solutions and testing results


Using the chart to the left a motor gearbox can be selected from velocity requirements that ensures efficient motor operation

  • Using the chart to the left a motor gearbox can be selected from velocity requirements that ensures efficient motor operation





Strengths

  • Strengths

    • Modular gearbox options
    • Multiple opportunities to change gear ratios
    • Belt protects critical drive components
    • Easy assembly of drive components
  • Weaknesses

    • Lack of belt tensioner limits modularity
    • Size of motor increases RP1 size
    • Limited availability of motor gearboxes


Responsibilities:

  • Responsibilities:

    • Design a steering system capable of infinite rotation
    • Implement, build and integrate with all RP1 subsystems
  • Challenges of MSD II

    • Total re-design including custom turntable, starting week #1
    • Subsystem integration
    • Belt Sizing
    • Friction!




Strengths:

  • Strengths:

    • Robust steer system
    • Custom turntable is light, smooth, and easy to access/assemble
    • Infinite rotation
    • Intuitive and efficient belt tensioning
  • Weaknesses

    • Side load from belt drive system causing misalignment
    • Extreme sensitivity to belt length
    • Tendency of steer system to force rotation of drive shaft, and vice versa
    • Friction!
    • Demands tight tolerances






Responsibilities:

  • Responsibilities:

    • Responsible for structural skeleton of RP1
    • Design a rigid and robust framework
    • House all other sub-systems within framing
    • Provide protection against a drop to the floor
    • Challenges of MSD II:
    • Maintaining machining tolerances during mass production
    • Lack of experience with machining equipment early in MSDII
    • Developing precise and efficient machining techniques








Strengths

  • Strengths

    • Robust: designed for impact
    • Concentrates force of impact from drop in lower axle
    • Easily assembled and disassembled
  • Weaknesses

    • Size: minimally smaller than RP10
    • Lower axle fails in drop test but can be quickly replaced


Responsibilities:

  • Responsibilities:

    • Design a prototype platform
      • Includes area for 1kg payload
      • Includes area for platform electronics
      • Testing the functionality of 1 MM at a time
      • Built-in wheels to allow for platform travel
    • Design a modular mounting system
      • Must be capable of attachment to platform
      • Must meet design spec for attachment
  • Challenges of MSD II

    • Use of materials readily available for platform
    • Having a low center of mass for drivability




Strengths

  • Strengths

    • Easy to make prototype platform
    • Very quick and efficient mounting
  • Weaknesses

    • Made of plywood and boards
    • Structural support questionable when using substantial weight
    • Requires a square-shaped cut-out
    • MM must mount in the designated forward direction for index to work properly




Responsibilities

  • Responsibilities

    • Provide components for motor control
      • H-bridge
      • Boost & Buck PCB
      • Interface PCB
      • Wiring & Connectors
    • Design and implement power supply
  • Challenges of MSD II

    • PCB board design
    • Integration of all electrical components










Strengths

  • Strengths

    • Capacity for 2 MM’s
    • Integration of all electrical components
    • Single connection with platform
  • Weaknesses



Responsibilities:

  • Responsibilities:

    • GUI for user control
    • Wireless communication between MM and computer
    • Generate all necessary signals used for controlling motors
    • Display speed, turning angle, and battery life
  • Challenges of MSD II

    • Selected wireless components not functioning
    • Limitations of microprocessor – not enough I/O pins
    • Out of practice with Java


Wireless Transmission:

  • Wireless Transmission:

    • Couldn’t download code to MICAZ motes
    • TelosB motes used instead
    • Not yet demonstrated to be functional
  • Microprocessor:

  • GUI:

    • Java, using the Eclipse IDE
    • New design in consultation with Prof. Hawker




Strengths

  • Strengths

    • Ability to turn, drive, and stop based on commands issued by the user
    • GUI supports multiple platform designs
    • Open-source, Java readily available
  • Weaknesses

    • One direction communication with the MM
    • Only set up to work with one MM




MM attaches in under 1 minute

  • MM attaches in under 1 minute

  • Weighs under 5 pounds

  • Complete disassembly in less than 10 minutes

  • Compact size

  • Infinite rotation

  • Robust

  • Less than $900







Proven robust design

  • Proven robust design

  • Modular mounting

  • Replace drive with 1:71 gearbox motor

  • Resulting 14.5 in/s @ peak efficiency

  • ANSYS MODELING RESULTS

  • Check:

    • Design of Machine Element calculations
    • Effects on batteries


Yes it can!

  • Yes it can!



Strengths

  • Strengths



Open motor selection & configuration

  • Open motor selection & configuration

  • 170°or 180° rotation requirement, to replace infinite rotation requirement

  • Emphasize compact design

    • + Establish clear size constraints
    • + Goal of existing design size (ex. 10%)














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