[FTC]: Drive Platform- Design Exercise

[DavisDad]

Originally Posted by cadandcookies

...were you able to fit 20 pieces of debris in the goals? ...!

I took a closer look at the CAD model and it looks like about 10 pieces will fill the bin.

[cadandcookies]

Originally Posted by DavisDad

Hmm... looking at the scoring table in Scoring Summary 1.7, it looks like you can. I don't understand what 1.5.3.4.e means: "e. Cliff Zone: See End Game scoring". But... we'd be in the "High Zone", not the "Cliff Zone", at the end of Driver-control period.

According to the manual:

Originally Posted by FTC Game Manual, 1.5.3-4

Point levels are
based on the Area of the Mountain that Supports the Robot. The Score is not dependent upon being In or Completely In an Area.

Also relevant:

Originally Posted by FTC Game Manual, 1.5.4

The last thirty seconds of the Driver-Controlled Period is called the End Game.

and I'm not sure what conditions you could find where you could be scored to be both fully supported by the mountain High Zone and the Pull-Up Bar at the end of the match, as they're mutually exclusive conditions, since the End-Game is part of the Driver Controlled Period.

Could you explain how you came to a different conclusion?

Originally Posted by DavisDad

I took a closer look at the CAD model and it looks like about 10 pieces will fill the bin.

Nice! This is a bit higher than my estimate, which was 6 based on the CAD model.

[DavisDad]

Originally Posted by cadandcookies

...and I'm not sure what conditions you could find where you could be scored to be both fully supported by the mountain High Zone and the Pull-Up Bar at the end of the match, as they're mutually exclusive conditions, since the End-Game is part of the Driver Controlled Period.

Could you explain how you came to a different conclusion?

The statements below seem to conflict, but I agree your interpretation makes more sense.

"The Driver-Controlled Score is based on the location of the Scoring Elements, all Clear Signals, and Robots at the end of the Match after all objects have come to rest."

"Robots earn points based on where they are Parked On the Mountain at the end of the Driver-Controlled Period."

I was assuming,and the Scoring Summary (1.7) seems to indicate, that "Driver Control Period" and "End Game" are 2 different periods. But... the robots are under driver control during the End Game.

[manojkr]

Originally Posted by DavisDad

Hi Manoj,

Yes, there are Tetrix as well as Modern Robotics Inc. and Matrix models that have been added to OnShape. You asked: "How does that work?" Are you asking about how use OnShape? Or... specifically how to use the "Public" models at the OnShape site?


Craig

Hi Craig, thanks for confirming that. I meant if those models are readily available to use or do I need to do additional importing of the models. I guess when I start using it might become more clearer. Let me try it tonight and I'll get back if I've more questions.

Thanks
Manoj

[DavisDad]

Thanks Nick (cadandcookies) for pointing out my error in scoring related to driving/climbing of the robot, as well as capacity of the goals for Debris. Below is revised scoring:

Scoring- The scoring capability related to drive design is challenging related to climbing the mountain. We estimate that purely driving/climbing ability can score 40 points by driving up to the "Mountain High Zone" in Autonomous Mode. And... if the robot can climb to the High Zone, we'll be able "hang" using fairly simple mechanisms (80 points hang & 20 points "All Clear Signal"). So... climbing could affect a total of 140 points for the team.

[DavisDad]

Originally Posted by manojkr

... if those models are readily available to use or do I need to do additional importing of the models. ...

They are available in 2 ways within OnShape.

1. Any "Public" workspace can be copied by anyone using OnShape. Parts and assemblies created with OnShape have all the attributes of the original.
2. Models created in other CAD software can be uploaded and used within OnShape, but don't have the original detail (e.g. sketch dimensions). Tetrix, AndyMark, Modern Robotics Inc, McMaster-Carr, etc. CAD models are available at their websites as STEP files and are very useful for CADing.

The above is true for all the mainstream CAD packages: Solidworks, Creo, Inventor and more. My opinion is that OnShape is ideal for FIRST as all computing and file handling is done "in the cloud" and eliminates the IT headaches for PC installed software. OnShape can be used from any machine and any OS using web browsers: Safari (Mac OS only), Mozilla Firefox, Google Chrome & Opera (not IE). And... it's FREE with easy account set-up.

[manojkr]

Originally Posted by DavisDad

....They are available in 2 ways within OnShape. ....

Thank you so much for your help. I was able to import the field setup from Andymark.

[DavisDad]

We've done some work on the "Big Wheel" concept design to look at the center of mass (CoM) issues:

• 8" wheels result in a narrow wheel base ~8"
• When climbing the 50 deg churros rungs, the contact point of the wheels narrows to 5.3" and the vertical distance inside the wheel base narrows to ~3.5"
• Not only must the CoM be kept inside the 3.5" zone, torque from the rear wheel can flip the robot.
• We want to maintain 2" clearance between robot bottom to floor. This prevents lowering the motors, battery, etc. This will allow "debris" to pass under without obstructing travel of the robot. "Tripping" over the blocks could hinder autonomous navigation.

We sketched a design where the motors are set forward and battery is at front. Even this does not put the CoM in the "safe zone".

[GeeTwo]

Originally Posted by DavisDad

We sketched a design where the motors are set forward and battery is at front. Even this does not put the CoM in the "safe zone".

Have you moved your arm fully forward and/or down? That could move your CoM a good bit.

Another thing that might help would be to make your wheelbase (distance between axle centers) a multiple of the churro spacing (4.8"?). This would keep you from rocking back and forth as you climb, though you would need a bit of extra torque as you come up out of a trough. In order to do this and remain under the size limit and not fall into the spaces, you may have to have more than one plane of wheels on each side.

[Greg Needel]

Originally Posted by DavisDad

We've done some work on the "Big Wheel" concept design to look at the center of mass (CoM) issues:


We sketched a design where the motors are set forward and battery is at front. Even this does not put the CoM in the "safe zone".

So my team is playing with this also, and while the problems of weight distribution are important, we feel that you can get around it because there is no weight limit on FTC bots. While you want to keep the robot as light as possible since power is limited, it also is very realistic to add ballast exactly where you need it using things besides the battery and motors. With a few lbs of steel riding right on the front of your chassis you should be able to compensate to make this concept work.

[DavisDad]

Originally Posted by GeeTwo

Have you moved your arm fully forward and/or down? That could move your CoM a good...

Yes, extending arm forward, with 1lb weight, moves CoM to about centerline of safe zone. And... has better distribution when level.

[DavisDad]

Originally Posted by Greg Needel

...it also is very realistic to add ballast exactly where you need it using things besides the battery and motors. With a few lbs of steel riding right on the front of your chassis you should be able to compensate to make this concept work.

Yes, ballast will be used after the other mechanisms are chosen. We've found weight balance and precise alignment of the wheels make a big different in how the drive platform tracks.

For this design exercise, we're looking at using the arm as follows:

[GeeTwo]

Originally Posted by DavisDad

Yes, extending arm forward, with 1lb weight, moves CoM to about centerline of safe zone. And... has better distribution when level.

Originally Posted by DavisDad

For this design exercise, we're looking at using the arm as follows:

Cool - almost exactly what I had in mind when I suggested moving the arm forward and down. Glad to see it's working out.

[wgardner]

Originally Posted by DavisDad

Will do… other motors are at school and won’t be able to test them until September. We also want to test the secondary gearbox performance we’re adding as part of this project.

Hi,

Any chance for these tests to be rerun with the Tetrix and Neverest motors now that school is open and the motors are presumably available? Thanks so much!

[DavisDad]

Originally Posted by wgardner

Hi,

Any chance for these tests to be rerun with the Tetrix and Neverest motors now that school is open and the motors are presumably available? Thanks so much!

I've been preoccupied with the new controls and changes in drive platform requirements. Hopefully I'll get to it this weekend.