Articles by tag: control

Articles by tag: control

    Swerve Drive Experiment

    Swerve Drive Experiment By Abhi

    Task: Consider a Swerve Drive base

    During the entire season of Relic Recovery, we saw many robots both in and outside our region that had a swerve drive. As Iron Reign, we never considered a swerve drive in the past but seeing all the robots, I wanted to see if it was maybe possible. One motivation was that I didn't like how slow mechanums were. Swerves generally use traction wheels and create a faster speed than usually can be found with mechanum. Also, it seemed as if swerve could provide the mobility neccessary that a mechanum drive provided. This is why I wanted to consider the possibility of a swerve drive and why I did more investigation.

    I first came across the PRINT swerve for FTC by team 9773. They had a very detailed explanation of all the parts and assebly tools. After reading into it more, I decided that the system they created wasn't the best. First, the final cost of the drive train was very expensive; we did not have a very high budget despite help from our sponsors. If this drive train didn't work for some reason after playing with it over the summer or if the chassis didn't make sense to use in Rover Ruckus, we would have almost no money for an alternate drive train since we wanted to presearve Kraken. Also, they parts used by 9773 invovled X-rail rather than extrusion rail from REV. This would cause problems in the future as we wold need to redesign the REVolution system for X-rail. In the end, I decided this was not worth it to pursue.

    After further investigation, I found a chassis by team 9048. The swerve they developed looked like a more feasible option. By using REV rail and many of the parts we had, I thought this would be a possible prototype for Iron Reign. Because they didn't have a parts list, we had the find the rough estimate of cost from the REV and Andymark websites. Upon further analysis, we realized that the cost, though cheaper than the chassis of 9773, would still be a considerable chunk of our budget. But I am still motivated to find a way to make this happen.

    Next Steps

    Possibly scavenge for parts in the house and Robodojo to make swerve modules.

    Swerve Drive Prototype

    Swerve Drive Prototype By Abhi and Christian

    Task: Build a Swerve Drive base

    During the discussion about swerve drive, Imperial robotics, our sister team, was also interested in the designs. Since we needed to conserve resources and prototype, I worked with Christian and another member of Imperial to prototype a drive train.

    Due to the limited resources. we decided to use Tetrix parts since we had an abundance of those. We decided to make the swerve such that a servo would turn a swerve module and the motors would be attached directly to the wheels. This system would be mounted to a square base. We decided to go ahead and make the base.

    Immediatly we noticed it was very feeble. The servos were working very hard to turn the heavy module and the motors had trouble staying aligned. Also, programming the train was also a challenge. After experimenting further, the base even broke. This was a moment of realization. Not only was swerve expensive and complicated, we also would need to replace a module really quickly at competition which needed more resources and an immaculate design. With all these considerations, I ultimately decided that swerve wasn't worth it to use as a drive chassis.

    Next Steps

    Wait until Rover Ruckus starts so that we can think of a new chassis.

    Position Tracking

    Position Tracking By Abhi

    Task: Design a way to track the robot's location

    Throughout the Relic Recovery season, we have had many issues with the autonomous being inaccurate simply because the scoring was dependent on perfectly aligning the robot on the balancing stone. This was prone to many issues as evidenced by numerous matches in which our autonomous failed. Thus far, we had relied on the encoders on the mecanum chassis to input distances and such. Though this worked to a significant degree, the bot was still prone to loss from drift and running into the glyph pit. We don't know if glyphs will be reused or not but we definitely needed a better tracking mechanism on the field to be more efficient.

    After some investigation online and discussing with other teams, I thought about a way to make a tracker. For the sake of testing, we built a small chassis with two perpendicular REV rails. Then, with the help of new trainees for Iron Reign, we attached two omni wheels on opposite sides of the chassis, as seen in the image above. To this, we added axle encoders to track the movement of the omni wheels.

    The reason the axles of these omnis was not dependent of any motors was because we wanted to avoid any error from the motors themselves. By making the omni wheels free spinning, no matter what the encoder reads on the robot, the omni wheels will always move whichever direction the robot is moving. Therefore, the omni wheels will generally give a more accurate reading of position.

    To test the concept, we attached the apparatus to ARGOS. With some upgrades to the ARGOS code by using the IMU and omni wheels, we added some basic trigonometry to the code to accurately track the position. The omni setup was relatively accurate and may be used for future projects and robots.

    Next Steps

    Now that we have a prototype to track position without using too many resources, we need to test it on an actual FTC chassis. Depending on whether or not there is terrain in Rover Ruckus, the use of this system will change. Until then, we can still experiment with this and develop a useful multipurpose sensor.

    Replay Autonomous

    Replay Autonomous By Arjun

    Task: Design a program to record and replay a driver run

    One of the difficulties in writing an autonomous program is the long development cycle. We have to unplug the robot controller, plug it into a computer, make a few changes to the code, recompile and download the code, and then retest our program. All this must be done over and over again, until the autonomous is perfected. Each autonomous takes ~4 hours to write and tune. Over the entire season, we spend over 40 hours working on autonomous programs.

    One possible solution for this is to record a driver running through the autonomous, and then replay it. I used this solution on my previous robotics team. Since we had no access to a field, we had to write our entire autonomous at a competition. After some brainstorming, we decided to write a program to record our driver as he ran through our autonomous routine and then execute it during a match. It worked very well, and got us a few extra points each match.

    Using this program, writing an autonomous program is reduced to a matter of minutes. We just need to run through our autonomous routine a few times until weare happy with it, and then take the data from the console and paste it into our program. Then we recompile the program and run it.

    There are two parts to our replay program. One part (a Tele-op Opmode) records the driver's motions and outputs it into the Android console. The next part (an Autonomous Opmode) reads in that data, and turns it into a working autonomous program.

    Next Steps

    Our current replay program requires one recompilation. While it is very quick, one possible next step is to save the autonomous data straight into the phone's internal memory, so that we do not have to recompile the program. This could further reduce the time required to create an autonomous.

    One more next step could be a way to easily edit the autonomous. The output data is just a big list of numbers, and it is very difficult to edit it. If we need to tune the autonomous due to wear and tear on the robot, it is difficult to do so without rerecording. If we can figure out a mechanism for editing the generated autonomous, we can further reduce the time we spend creating autonomous programs.

    Relic Recovery Brainstorming & Initial Thoughts

    Relic Recovery Brainstorming & Initial Thoughts By Ethan, Charlotte, Kenna, Evan, Abhi, Arjun, Karina, and Justin

    Task: Come up with ideas for the 2018-19 season

    So, today was the first meeting in the Rover Ruckus season! On top of that, we had our first round of new recruits (20!). So, it was an extremely hectic session, but we came up with a lot of new ideas.

    Building

    • A One-way Intake System
    • This suggestion uses a plastic flap to "trap" game elements inside it, similar to the lid of a soda cup. You can put marbles through the straw-hole, but you can't easily get them back out.
    • Crater Bracing
    • In the past, we've had center-of-balance issues with our robot. To counteract this, we plan to attach shaped braces to our robot such that it can hold on to the walls and not tip over.
    • Extendable Arm + Silicone Grip
    • This one is simple - a linear slide arm attached to a motor so that it can pick up game elements and rotate. We fear, however, that many teams will adopt this strategy, so we probably won't do it. One unique part of our design would be the silicone grips, so that the "claws" can firmly grasp the silver and gold.
    • Binder-ring Hanger
    • When we did Res-Q, we dropped our robot more times than we'd like to admit. To prevent that, we're designing an interlocking mechanism that the robot can use to hang. It'll have an indent and a corresponding recess that resists lateral force by nature of the indent, but can be opened easily.
    • Passive Intake
    • Inspired by a few FRC Stronghold intake systems, we designed a passive intake. Attached to a weak spring, it would have the ability to move over game elements before falling back down to capture them. The benefit of this design is that we wouldn't have to use an extra motor for intake, but we risk controlling more than two elements at the same time.
    • Mechanum
    • Mechanum is our Ol' Faithful. We've used it for the past three years, so we're loath to abandon it for this year. It's still a good idea for this year, but strafing isn't as important, and we may need to emphasize speed instead. Plus, we're not exactly sure how to get over the crater walls with Mechanum.
    • Tape Measure
    • In Res-Q, we used a tape-measure system to pull our robot up, and we believe that we could do the same again this year. One issue is that our tape measure system is ridiculously heavy (~5 lbs) and with the new weight limits, this may not be ideal.
    • Mining
    • We're currently thinking of a "mining mechanism" that can score two glyphs at a time extremely quickly in exchange for not being able to climb. It'll involve a conveyor belt and a set of linear slides such that the objects in the crater can automatically be transferred to either the low-scoring zone or the higher one.

    Journal

    This year, we may switch to weekly summaries instead of meeting logs so that our journal is more reasonable for judges to read. In particular, we were inspired by team Nonstandard Deviation, which has an amazing engineering journal that we recommend the readers to check out.

    Programming

    Luckily, this year seems to have a more-easily programmed autonomous. We're working on some autonomous diagrams that we'll release in the next couple weeks. Aside from that, we have such a developed codebase that we don't really need to update it any further.

    Next Steps

    We're going to prototype these ideas in the coming weeks and develop our thoughts more thoroughly.