2021-09-23 Meeting Minutes - Drivetrain

7 Days until Prototyping Conclusion!

Prototype

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

Sourcing

Short-Term Research

Long-Term Research

Member	Update	Action Items
Emily Adam (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

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