Odom Pod Improvements

Odom pods

Last year we had a lot of problems will odom accuracy and consistency that we think had to do with the way that the physical odom was set up. Last year we decided to put a wheel on a long cantilever with little support, which caused it to lack rigidity. The lack of rigidity in this system allowed it to move around and cause inaccuracies in our odom measurements. There were 2 unneccecary cantilevers in this system that even at the maximum tightness allowed the wheels to move around a lot. All of this slop was often because odom was an afterthought. This year we are putting more time into determining all the requirements for an odometry system, and designing an ideal odometry system around that to give our odometry system the most accuracy without having to reset.

Requirements for an odom system

• Springs below the base more than 1/2 an inch
• Rigid side to side and tortionally(Doesn't rotate off axis)
• Doesn't slip
• Reliable

Springs

TODO: rewrite to be more like other categories

There are a lot of ways that you can apply a spring force in vex.

• Cantilevered arm w/ rubber bands
  • Most people with odometry use this solution because it is the most well known and applies a fairly consistent force
  • Pros:
    • A lot of designs are out there
    • We have experience making robots with it
    • You can switch out rubber bands if they get old
  • Cons:
    • Rubber bands can wear out
    • Leaves a lot of slop
    • Bulky
• Polycarbonate springs
  • Using polycarbonate springs as a compliant spring component will allow us to get rid of a joint and increase rigidity in the system
  • Pros:
    • More rigid
    • Less parts
    • Simple
  • Cons:
    • Harder to replace

Another solution that we thought of was to use polycarbonate springs that also support the wheel. This solution will allow more consistency over time because the polycarbonate will break down slower and retain more consistency than a rubber band would.

Sensor

VEX offers 2 types of sensors to determine rotation, the V5 rotation sensor, and the 3 wire optical rotation sensor.

• V5 rotation sensor
  • Pros
    • Overall smaller
    • 0.01 degree accuracy
  • Cons
    • Thicker
    • Unknown limitations, thanks vex 🖕
• Optical rotation sensor
  • Pros
    • Thinner
    • 1 degree accuracy
  • Cons
    • Bigger overall
    • ~163 in/s max speed

We chose the rotation sensor because of the more compact package that will fit better onto the polycarbonate spring

Cantilever

There are plenty of options for the part that supports the wheel but there have been 2 main options that have been primaraly used polycarbonate and metal

• Metal
  • Pros
    • Very rigid
  • Cons
    • Can't be used as a bearing surface
    • Heavy
• Polycarbonate
  • Pros
    • Light
    • Very custom
    • Bounces back to original position when bent
    • Can be used as a bearing surface
    • Less slop
  • Cons
    • More flexible

We chose polycarbonate because of how little slop it is and how clean the design will be.

Designs

Design 1

• Polycarbonate springs
  • Why?
• Polycarbonate construction
  • Why?
• Rotation sensor
  • Why?

Design 2

• Polycarbonate springs
  • Why?
• Polycarbonate construction
  • Why?
• Optical shaft sensor
  • Why?

Final design

Conclusions