Project Specifications System Level

Overview

• Overview

• Project Specifications
• System Level

• 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

• 1, Functioning Platform & Motor Module
• 3, Motor Modules

• 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
• Also incorporated re-vamp of tensioning system
• 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

• Takes time to locate broken components on PCB
• PCB Corrections
• PCB has no output diode

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:

• Freescale
• Handles encoder feedback
• Speed up, slow down, turn left and right

• 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%)