It has been several years in the making but I am finally ready to start talking publicly about some design work I have been working on for 3 years now.
A photo of my Diff Swerve V3.0 module was released today on the Formlabs Instgram site. Please go visit that link and like/comment/follow/etc. If I get a ton of traffic to the site, I am hopeful that Formlabs will be more likely to support FIRST-type projects going forward.
Before I do, some thankyous.
#1 TJ2 Team 88. The team has been supportive in 100s of ways. Buying supplies, devoting coding resources, providing moral support. So grateful
#2 Formlabs. when they hired me and told me “infinite 3D prints” were part of the offer, I am not sure they understood just how many prints that would mean in my particular case. But despite my outsized appetite for printing, I’ve gotten nothing but support.
#3 Steal from the best. This design owes a lot to the work of Swerve Design Specialist, West Coast Design, & (the ever gracious) Stryke Force #2767 & Bomb Squad #16 (well, as long as I am thanking Swervey FIRST teams, Robonauts #118, Wildstang #111, & ChiefDelphi #47 carried a lot of water moving Swerve Designs forward over the years)
- New concept for Diff Swerve: the Differential is accomplished using spur gears only – I hate having one bevel gear in this design. I wasn’t about to add more if I can help it.
- Designed from ground up to have as much as possible printed on a Formlabs Fuse1 Printer. Only non printed parts: Sensor, motors, shafts, gears, bearings, tread, chain, fasteners
- All gears, shafts, bearings designed using 100in-lbs load input at Falcon Shaft (~2.5X stall torque of Falcon 500 motor)
- 100% custom spur gear profiles to maximize strength, packaging, & performance
- Approx 40 ball bearings (they are cheap and the design is complicated, why skimp?)
- The equations of motion for driving a Diff Swerve compared to a standard Swerve are surprisingly straightforward. A simple 2D matrix transformation allows you to basically treat the steering and drive outputs as independent (e.g. you desire OmegaSteering and OmegaWheels you simply multiply that vector by a 2D matrix to determine OmegaMotor1 & OmegaMotor2 that will provide desired steering and wheel outputs)
- Oh yeah. IT WORKS! It works really well. This is the 1st Diff Swerve module that have seen that is close to what I will call Competition Ready.
Video of the module
Video of the chassis
Now to the spec (for V3.1):
- Motors: Falcon 500
- Wheel: 3.5Dia with 1.5" Blue Nitrile Tread on custom printed hub
- Ratio (wheels): 6:1 (=1.83"/motor rev = 46.5mm/motor rev => Top Speed 14.5fps 4.5m/s)
- Ratio (steering): 12:1
- Weight: ~6.5lbs per module
- Height: 7" << Key Priority to stay under bumper height
- Swerve Axis to Frame Perimeter: 2.93"
- Steering Sensor: Absolute Position (in addition to Falcons of course)
Multi motor configurations (Current design is a Ukulele form factor with both motors along the same frame rail. Coming Soon: SkyScraper with the motors standing tall & proud and Stealth Bomber with one motor against each rail forming a sort of V shape plan view)
Complete Software Package (goal is to make Diff Swerve easier than Tank Drive)
Find some beta tester
Figure out a “go to market” plan in order to get Diff Swerve on as many robots as I can. I am really hoping to get some interest in someone willing to distribute this (AM, Vex, WCP, REV, CTRE, … at me, I am all ears)