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2021-09-23 Meeting Minutes - Drivetrain

2021-09-23 Meeting Minutes - Drivetrain

Sept 27, 2021

7 Days until Prototyping Conclusion!

  • Will include a formal recap of prototyping results & discussion for next steps

11 Days until Sourcing Conclusion!!

25 Days until First Draft CAD Due!!!

 

Goals

  • Review prototype results so far

  • Review next steps sourcing & design phase

Current State of Progress

Prototype

  • Mechanical state

    • 1 Bogie popped off cause of the short screws

    • Hard stops for the differential were a bust...lol. Needed very little clearance → further investigation to confirm

    • Might want to invest in a Wheelez pressure gauge

    • Weighed the prototype. It's 41.55 kg!!

    • To do still:

      Repair bogie leg, reinforce with longer screws, more screws
      Assemble legs back onto the rover
      Secure bottom of MDF to crossbeams lmao

  • Wiring/Controls

    • Got current sensing working! There is quite a bit of noise though, so data will not be super precise

    • Issues pulling the voltage data from the RPI

    • To do still (Sahil):

      Write a function to pull the peak and nominal voltages. Print at the end of the .txt file

  • Prototype results!

    • High-stress locations:

      • Connecting plates on the legs. When turning, these pates are getting pushed/pulled as the wheels resist the movement

      • Connection point from the legs/suspension to the chassis. Is constantly twisting about that point during turns → maybe we continue allowing it to move?

    • With little pressure, the differential bar will allow the chassis to pivot about the rocker beam. This is likely due to the differential bar being able to twist out of position and into its clearance zone

    • Chassis bounces for on-the-spot turns. Something for EE & Arm team to keep in mind

    • Having our motors protected/out of the way is a really good idea :^) Almost cracked one dragging it across a rock

    • Totally bidirectional. Rocker arm should be the front for going over large obstacles, whereas use bogie for small & frequent obstructions

    • To do still:

      Test turning scrub → to clarify
      Test against hills and sand
      Test CoG without battery
      Test different locations of CoG on obstacles
      Tread style testing → do we feel the need? Maybe assess after we drive in sand

Additional Items

Sourcing

  • Motor and gearbox selection

    • Emily

  • Carbon fibre sourcing → do we need greater than 32mm in diameter?

    • Asha

Short-Term Research

  • Accurate Wheelez CAD

    • Chan

  • Differential bar VS differential gearbox

    • Emily

  • Strategies to keep suspension aligned

    • Max

Long-Term Research

  • Read documentation and analysis papers of rocker-bogie projects

    • Emily

  • Carbon fibre bonding, figure out tolerance and prototyping

    • Asha

  • Learn FEA

  • Learn SolidWorks simulation?

  • Investigate and prototype tread styles

  • Continue custom wheel research

Update & Action Items

Member

Update

Action Items

Member

Update

Action Items

@Emily Adam (Deactivated) (Differential bar)

  • Got some motor candidates! But maybe got ghosted

  • Wrap up prototyping

  • Do differential bar VS gearbox research

  • Finalize motors, organize meetings to review choices

  • Put together drivetrain budget

@Former user (Deleted) (Wheel connections)

  • Initial CAD of motor-wheel integration

    • NOTE: need to consider motor dimensions VS Wheelez hub size

    • Increase fit around motor to prevent damage if we run into a wall (avoid resting it)

    • Consider sheet metal brace to give more tolerance for bending

    • Use thicker sheet metal if possible

    • Consider critical holes close to bend in sheet metal

  • Evaluate 32mm CF under expected forces

  • Source carbon fiber

    • Provide an estimate of how much we need to buy

    • Propose piece of stock to go with

@Former user (Deleted) (Chassis)

  • Continued planning & analysis of mechanism mounting

    • Weight saving wise: probably best to use a square plate that's lasercut with the openings we need

    • Probably minimize chassis width

  • Get in touch with Ethan, Austin, Ali(?) about mounting mechanisms

@Former user (Deleted) (Frame/structure)

  • Prototype CAD of adjustable CF connectors!

    • Would require a super close fit on the bolt. Maybe look at more permanent fastening options?

    • Could make mounting block also modular + add mounting locations

    • Consider mass doe

  • Investigate suspension alignment

  • Work on initial CAD

Chan

  • Prototype testing

  • 95% of training

  • Create an accurate CAD for the Wheelez

Thomas

  • Working through training

 

Discussion Planning for Prototype Conclusion Meeting

  • Differential bar VS differential gearbox decision

  • Discuss methods of increasing the suspension's stability and its alignment to the rest of the rover

  • Review motor layout

    • Proceed with motor integration into wheels?

    • Combined bogie motors? 6 motors → 4 motors

  • Review wheel layout