Today a group of students began making some renders for our technical binder starting with our drivebase. We used Blender as opposed to another CAD rendering engine due to the faster render times and higher quality results. To import CAD files into Blender, the file format .gltf must be used, which is the blender equivalent to a .step file. Due to the larger size of the file, the download takes significantly longer. In Blender, materials need to be updated to be more realistic and a world shader must be added. As more CAD is finalized for the current build of the robot, more renders will be completed and posted.
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Tweaking & Testing
It feels like the season just started, but here we are less than a week from our first event of the year. On Saturday 2/18 our team will be one of 30 teams at the official Week Zero Scrimmage hosted by Team 811 The Wild Cards. Good luck to all teams attending or hosting a scrimmage!
To prepare we have been busy working on many small adjustments to the robot, making our first set of practice bumpers, and automating routines on the gold robot. More updates will be in the next software post.
Yesterday we took our gold robot and alpha robot to WPI to test on a full field. WPI has gone above and beyond supporting the New England community by providing a full practice field for teams to use. This included having a real Charging Station made providing some ideal access to tune some auto balancing routines before hitting an official field. As a COTS swerve team using SDS MK4i modules we were very curious how our robot would handle getting the ramps of the Charging Station down during auto consistently and if an active mechanism may have been needed.
We started tuning our Auto Balancing routine we made on our wooden Charing Station at home. It worked pretty well and we did some tests if another robot was stationary while a driver ran the routine.
Since our robot is very light (under 100lbs) the gold robot had a hard time driving onto the station if Alpha was already balanced on it. One time we came at an angle and it did get up but didnât seem consistent. Once it was on the ramp, auto balancing could do its thing. We didnât drive Alpha around because we didnât have bumpers made so we didnât test two driving on at once.
Next we moved into basic autonomous routines and played around getting a simple L3 Cone + Mobility and L3 Cone + Auto Balancing made. These we feel are satisfactory for next weekend and will let us move to other tasks.
Thereâs still more work to be done making tweaks to speed things up, work on inverting for Red/Blue, and slowly get the Mobility routine closer to a Staging Mark to plan to set us up for picking up a game piece. Youâll notice the auto balancing sequence stopped working halfway through this video. After we did some teleop practice we started increasing the drivebase speed and the changes started to impact the auto balance routine we had tuned. By the end of the video near the end of the day we got it working.
These auto routines worked with minor tweaks with no adjustments between the wooden and real versions. We were very excited about this since again we were worried if our robot would be consistent on a real charging station. For any teams wondering about our clearance the bumpers we used in the video are 1 â â inches off the floor and using a slicker fabric VX21 X-Pac Fabric.
Next we did some much needed cycling to work through the setpoints we had been tuning in the Grid and Double Substation.
In these videos the drivebase top speed was limited and some other things like the Cardinal Direction Control had not been fully tuned. We also swapped a few different drivers and one of the Cone pegs wasnât 100% stable causing some misses in auto. The good thing was it proved our robot can do what we intended it to do with scoring and pickup. We have long list of improvements to things like our sequencing, speeds, and handling of game pieces to not lose them so easily. The ground intaking isnât groundbreaking, but we knew that when we made the decision to use the wrist and basic claw vs. dedicating a whole mechanism which is in the works. More on this later.
Something it did show was the importance of the driver and operating communicating to ensure all arms in the robot are stowed before leaving the Community or Loading Zone. A trick we found was if you hugged the wall in and out of the Loading Zone you can extend your travel time in a safe space if you need to extend out two sides. Traffic patterns will be very interesting in this game coordinating 2-3 robots on each alliance needing to move in and out of these areas and crossing traffic with your opponents.
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Canât wait to see yâall this Saturday!
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It was a pleasure to see the Windham robot in person yesterday. Yâall are killing it, canât wait to get on the field together!
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Likewise! Canât wait to see the 1768 machine again next week. That robot is slick!
Thanks again for the BAG.
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Thanks for sharing the charging station videos with another robot on at various locations. We didnt have time to try this extensively.
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Love this process, do you think youâd be willing and able to post a âhow toâ when you guys are wrapped up? Iâve got a couple students who are looking to get started on renders, but I donât have much experience on how to do it well. Any details you guys would be willing to share would be an awesome resource for them!
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We look to release an in-depth tutorial on how to render a CAD model in Blender later on. However, this tutorial by BlenderGuru gives a very good explanation of Blenderâs features and how to use them. You can download Blender for free at Download â blender.org.
For now though, here are 2 more renders of our V1 and V2 claw. More to come soon later
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Is the CAD for V1 published? I couldnât find it on your onshape. Thank you.
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The various subsystems are in their own documents in an attempt to speed up the main assembly document.
Main assembly: Onshape
Arm: Onshape
Claw: Onshape
Drivetrain: Onshape
There have been a few other documents made for climbers and separate ground intakes but itâs unclear if any of that will be on the robot for week 1.
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Scouting!
Weâll be scouting at Week 0 both so we can make educated selections come alliance selections and so we can test out our scouting system in preparation for GSD.
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We have 6 scouting tablets loaded with a custom configuration for QRScout (Thanks 2713!).
- If youâd like to download the config to your own device, it can be found here and uploaded to your QRScout page with the âUpload configâ button at the bottom of the page
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Tablets are very much not necessary to run the system, as it can be run on any device with a web browser. Weâve run it on studentâs phones before. The key is making sure everyone has the same configuration downloaded.
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6 scouts will each watch a separate robot every match, noting every scoring action they take on the QRScout webpage on the tablet.
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The Head Scout will scan the QR code with a wireless barcode scanner hooked up to a computer via a dongle, entering the data into a Google Sheet
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If possible, the laptop that is taking down data will be connected to wifi to allow the data to be updated on-the-fly. If not possible, the laptop taking data will host an offline google sheet and the data will be uploaded later. Many NE events have Wifi for public use, but this wasnât possible at the World Championship last year, so we had to run the system offline.
Some fun stuff in the scouting system:
- Sparkline trend graphs in the averages sheet
- Match quick reference:
mmmm data
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Wow! Looking great.
I see you guys moved the wire grommet on the forearm near the elbow from the side of the arm to the top of the arm. I noticed in one of your earlier pics that it looked like that wire snake sticking out the side of the arm was going to clash with the elbow chain. So that seems like a good move.
Do you have any pics of the new wire management scheme at the elbow?
Correct. We moved the grommet from the side to the top. One of those things you do in the model and then when you build it you realize when the arm is in the stowed position that grommet gets covered by a chain.
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One other technical update we havenât posted yet is a situation we are monitoring in the first stage of our gold robot. Also, we should stop using the term âgold robotâ because the other night we settled on Midas and Midnight as the names of the two robots. Midas is our practice robot with the yellow gussets and Midnight will be the competition spec robot with black gussets.
During the firsts tests of the Midas we noticed the arm appeared looser than the Vex arm on Alpha. You can see the second stage arm 1.5" box tube holding the end effector has a lot of side-to-side movement.
Major differences between the two robots is one used VersaFrame and the other MAXTube. The first stage on Alphas uses the 2x1 0.05" wall VersaFrame while Midas/Midnight have 2x1 Light 0.04" wall MAXTube. Upon closer inspection we found the second jointâs dead axle was cut a tad short so we re-made it and that tightened things up nicely. We also forgot to install blocks where the dead axle is held to act as spacers so the tube didnât crush. Simple error but adding those two changes stiffened things up nicely.
A few nights after we discovered the failure of our tube nuts we noticed a crack in the MAXTube at the second joint. The same joint that displayed the most slop from the short dead axle during the initial tests. The crack is right on the interior scribe line. We added some MAXTube endplugs here which fit perfectly above the 3dp block already installed. We realized we should have made a whole 3dp block to fit this space initially.
Right now its a watch item and the tube hasnât been replaced because it would be a long repair and will take the only working robot offline. So far the robot has been through an extensive amount of testing in our shop and at WPI and held-up fine. This weekend will be a big test to see if this issue grows between scrimmage and practice leading up to it.
Once Midnight is together we will investigate a plan to fix this so by GSD we have two solid arms together with the plan being Midasâ arm can be swapped in as the spare. Unsure if the fix is a better 3dp block/insert or making this stage out of thicker wall MAXTube. We think the block will be sufficient since we havenât seen this issue getting worse or show up on the other side.
Weird stuff.
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If you can drill a stop hole at the end of the crack you will buy a lot more life for that part.
I donât think you need to get crazy with adding a pin or arrester though.
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Interesting! So the crack in your tube appears to be aligned with the groove on the exterior surface. Is that what you are seeing. This would serve as a stress riser of sorts for shear stress in the wall.
The video that you showed seems to show a deformation mode that would result in the lower arm tubes twisting about their own centerline. This, of course would result in shear on the perimeter and maybe accounts for that crack you are seeing. It seems like perhaps a more substantial tie between the two beams would also help. If you replaced one of your round cross bars with a short length of 1x2 with some T gussets to tie that cross beam into the two main beams, you could probably stiffen that mode quite a lot. The problem of course is that would interfere with the scossoring of the arm if it was placed close to the elbow joint. But even if it were only able to be placed 1/2 way along the lower arm, I think it would help. The closer to the elbow, the better.
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The more I deal with stress and strain, the tensor and tensor I get and I just end up fatigued!
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