Articles by tag: mechanical

Articles by tag: mechanical

    C.A.R.T. Bot Summer Project

    C.A.R.T. Bot Summer Project By Evan, Abhi, and Janavi

    Task: Enhance our robot-building skills

    At Iron Reign, we hate to waste the summer since it’s a great time to get all the ridiculous builds out of the way. Thus, we created C.A.R.T. Bot (Carry All our Robotics Tools). Our constant companion these last few seasons has been our trusty Rubbermaid utility cart which has been beaten and abused, competition after competition, as it carried all our tools and robots. Because of all of this, we decided it was time to show the cart a little love, and in typical Iron Reign fashion, we went all out and turned it into a robot.

    Our first step was to switch out the back wheels on it to elf-sized bicycle wheels, allowing us to take on the mightiest of curbs and motorize it. To attach the wheels, a four foot or so cylinder of threaded steel was inserted in holes on either side of the cart. Two slots were cut out in the bottom for the wheels and they were eventually slid on, but not after 3D printed mounts for sprockets were attached to the wheels, enabling us to gear them in a one to one ratio with the sprocket attached to the motors, which consisted of two SIM motors commonly found on FRC robots.

    Before we used SIM motors, we attempted to power the cart using two Tetrix motors which were geared for speed but, due to load, barely moved at all. Besides a lack of power, they also tended to come out of alignment, causing a terrible noise and causing the cart to come to a stall. This was quickly scrapped. To mount the motors, we used two pieces of aluminum bars and bolted them to the motors, then screwed them to the floor of the cart, aligned with the wheels. We chained them together and got about powering the system. We got two 12-volt batteries and chained them in parallel so as to not overload the system, and hooked them up to a REV hub. Then, we ran them through a switch and breaker combination. We connected the motors to the rev hub and once we had it all powered up, we put some code on it and decided to take it for a spin.

    It worked surprisingly well, so we went back in and put the finishing touches on the base of Cart Bot, mainly attaching the top back on so we could put stuff on top of it, and cutting holes for switches and wires to run through, to make it as slick as possible. We added a power distribution station to assist with the charging and distribute current to any device we decided to charge on the cart. We will eventually hook this up to our new and improved battery box we plan on making in the few spare moments we’ll have this season, just a quick quality of life improvement to make future competitions go smoothly.

    Next Steps

    Our cart box isn’t done yet, as we intend to make a mount for a solar panel, which we will be able to charge the cart during the downtime in competitions (only if there’s a good window we can park it next to). The cart wasn’t just about having a cool new and improved cart that we don’t have to push (which it is), it also was a test of our engineering skills, taking things that never should have been and putting them together to make something that we will utilize every competition. We learned so much during this experience, I for one learned how to wire something with two batteries as not to destroy the system, as for everyone else, I can’t speak for all but I think we learned a very important lesson on the dangers of electricity, mainly from the height of the sparks from an accidental short that happened along the way. Despite this, the cart came out great and moves smoother than I ever could have hoped. The thing is a real blast and has provided a lot of fun for the whole team, because yes, it is ridable. We predict the speed it’s set at is only a fifth of its full potential speed, and since it already goes a tad on the fast end we don't intend to boost it anymore while there’s a rider on it. Overall, the project was a success, and I’m personally very proud of my work as I’m certain everyone else is too. Come to see it at our table, I really think it’s worth it.

    Designing Wheel Mounts

    Designing Wheel Mounts By Justin

    Task: Create wheel mounts for our Mini-Mecanum chassis

    Today, we modeled two possible designs for mini-mecanum wheel mounts. The purpose of the mounts is to hold a churro or hex shaft in place to mount mecanum wheels to. The first design was a 6cm by 6cm square with rounded edges that was 5mm thick. A hexagon was removed from the center to hold the churro that supports the mecanum wheel. This design, when printed on low infill, allowed the churro to rotate when enough force was applied. We modeled this design off of the wheel mounts on Kraken and Garchomp; the only differences are the size and material. Because we will be 3D printing these mounts, material efficiency is very important. This mount design used a lot of material to make a prototype, meaning a finished stable mount would need even more material to prevent the churro or hex shaft from slipping.

    Taking these problems into account, we designed a different way to mount the wheels. The new version can mount underneath a REV Rail and hold the shaft or churro perpendicular to the rail. This design uses much less infill than the previous one because of how small the mount is, and because the REV Rail also acts as support to prevent the churro or shaft from spinning. The mount also allows the mini-mecanum wheels to be mounted as close to the frame as possible, which can help make the robot more compact. This design will allow us to easily mount mini-mecanums to our frame, while using minimal filament and taking up very little space.


    Next Steps

    We need to build the full mini-mecanum robot to judge whether these designs will fully work.

    Corn-Cob Intake

    Corn-Cob Intake By Ethan and Abhi

    Task: Design an intake system unique for balls

    Right now, we're working on a static-deposit system. The first part of this system is having an intake mechanism that passively differentiates the balls and cubes, reducing complexity of other parts of the design. Thus, we created the corn-cob intake.

    First, we bought ice-cube trays. We wanted a compliant material that would grip the particles and be able to send them into a larger delivery mechanism.

    Then, we designed a wheel which' spokes would fit into the holes on an ice cube tray, allowing the tray to stay static while still being compliant in a cylindrical shape. Then, we can put axle hubs through the center of the wheel, allowing us to mount the wheels on a hexagonal shaft. Then, we can mount a sprocket on that, allowing the bar to be rotated for intake. This bar is mounted at the height of the balls, not blocks, so we can passively sort the minerals in-action.

    Next Steps

    We need to mount this on our robot and design a way to deliver the field elements. We're also going to go into more detail on the ice cube mounts in a later blog post.

    Another Design Bites the Dust

    Another Design Bites the Dust By Ethan

    Task: Discuss a new rule change

    At one point, we were thinking about creating a "mining facility" robot that stays static within the crater and delivers the blocks into the mining depot. In our eyes, it was legal as it would hold as many blocks as possible inside the crater but only deliver two at a time outside. It would be super-efficient as we would be able to stay within the crater, and not need to move.

    However, fate has struck. Earlier this week, we received this message:

    The rule limiting control/possession limits of minerals has been updated to indicate that robots may _temporarily_ hold more than 2 minerals in the crater, but must shed any excess over prior to performing any other gameplay activities (which would include scoring).
    says that "Robots In a Crater are not eligible to Score Minerals". Per the definitions of "In" and "Crater", if _any_ portion of a Robot is in the vertical area above the crater (extending from the field walls to the outside edge of the Crater Rim), then scoring a Mineral results in a Major Penalty.
    says that Robots may not obstruct another Robot's path of travel in the area between the Lander and a Crater for more than 5 seconds.

    This means that we couldn't do a static mining facility as we cannot score within the crater. Since we'd have a portion of the robot always in the crater, the existence of our robot would be a major penalty.

    Next Steps

    So, we need to rethink our robot. We still want to create a semi-static robot, but we need to redesign the intake portion.

    Mining Base 2.0

    Mining Base 2.0 By Ethan

    Task: Rethink our static robot idea

    So, our dream this year is to create a static robot. Last week, we found out about a rule change that would prevent our mining robot from staying within the crater. Naturally, we found a way around this, leading us to the Mining Base 2.0.

    The robot will be fixed under the lander's hooks, and have a horizontal and vertical linear slide attached to it. The horizontal linear slide would reach over the crater walls and pick up the silver balls, and shoot them up towards the lander. On the lander, our vertical linear slide would create a backboard that would allow the balls to fall into the lander. This wouldn't violate the rules as we wouldn't be in the crater. And, it would give us the benefit of having an extremely high-scoring robot.

    Next Steps

    We need to start on the designs of this robot, but to do this, we first need to create a working chassis.

    Issues with Driving

    Issues with Driving By Karina

    Task: Get ready for Regionals

    Regionals is coming up, and there are some driving issues that need to be addressed. Going back to November, one notable issue we had at the Conrad qualifier was the lack of friction between Bigwheel's wheels and the field tiles. There was not enough weight resting on the wheels, which made it hard to move suddenly.

    Since then many changes have been made to Bigwheel in terms of the lift. For starters, we switched out the REV extrusion linear slide for the MGN12H linear slide. We have also added more components to intake and carry minerals. These steps have fixed the previous issue if we keep the lift at a position not exceeding ~70 degrees while moving, but having added a lot of weight to the end of the slide makes rotating around the elbow joint of Bigwheel problematic. As you can see below, Bigwheel's chassis is not heavy enough to stay grounded when deploying the arm (and so I had to step on the back end of Bigwheel like a fool).

    Another issue I encountered during driver practice was trying to deposit minerals in the lander. By "having issues" I mean I couldn't. Superman broke as soon as I tried going into the up position, and this mechanism was intended to raise Bigwheel enough so that is would reach the lander. Regardless of Superman's condition, the container for the minerals was still loose and not attached to the servo. Consequently, I could not rotate the lift past the vertical without dropping the minerals I had collected.

    Next Steps

    To run a full practice match, Superman and the container will need to be fixed, as well as the weight issue. Meanwhile, I will practice getting minerals out of the crater.

    Latch Model

    Latch Model By Abhi and Justin

    Task: Model and print the Latch

    Early in the season, we made a hook, Although it was durable, it required a higher amount of precision than we would have liked to have, especially in the rushed last seconds of the endgame. As a result, we designed a latch that is completely 3D printed and placed it on the robot.

    This is the general model of it fit together (excluding left panel). The panels in the front are there to guide the latch into place when extending upwards from the ground.

    This wheel represents what actually does the latching. When sliding upwards, there are two wheels that twirl in opposite directions and slot into the lander bracket. We attached a smaller piece to this to tension with a rubber band allowing us to move up into the bracket but not back down.

    Next Steps

    We actually mounted this onto the robot and it seems to hold its own weight. However, the mounting was done very weirdly so we need to find a definite place for this system before we use it in auto or end game.

    Intake Omnis

    Intake Omnis By Ben

    Task: Add omnidirectional wheels to intake arm

    We need to add omniwheels to the intake arm to allow the arm to rest on the ground, while still maintaining the necessary height for collecting the minerals. If the height is too low, the minerals wouldn't be able to move through the intake. If the intake was too high, it wouldn't be able to grip onto the minerals and pull them through. We decided to use omnidirectional wheels as they would allow us to drive forward and backwards with the arm extended.Our first challenge was finding space on the intake arm to attach the wheels. We had a few options:

    • Attach the wheels parallel to the arm
    • To do this, we would have to have a "u" shaped component, which we could mount off of a threaded extrusion, then attach that to the servo mount.
    • Mount the wheel perpendicular to the arm
    • This would give the same degree of maneuverability. To attach this, we would have to use an elbow bracket and attach that to an extrusion at a 90° angle.
    Both of these present a similar challenge, leaving enough room for the intake to function properly. With about 2.5in. to work with, we mounted the wheel perpendicular with a 1.75 in. extrusion. We threaded the extrusion and used an elbow bracket to mount the wheel; this ensures the strength of the wheel. This left about 0.5in. between the wheel and the "corn on the cob" intake.

    Image of wheel attached to intake arm

    Next Steps

    Our next steps are to perform testing on the wheels to determine if they are durable and low enough, and improve the performance of the robot. One issue that may arise is rubbing against the gears, as they may shift over prolonged usage, along with twisting of the extrusion.

    Latch V.3.5 Assembly

    Latch V.3.5 Assembly By Ben

    Task: Assemble the V.3.5 latch and attach to the robot

    We assembled the fourth version of the latch today. Some of the improvements on this latch include using bigger bearings and thrust bearings inside. This latch is designed to be stronger and more reliable. After cleaning the parts and trimming some edges, we assembled the pieces. Upon assembly, we discovered an issue: the gears required a different amount of pressure to catch the lock. If left untreated, it could result in the robot falling off the hook. We determined the root of this problem was that the locking mechanism on the right gear was shorter than the left. To fix this, we trimmed a few millimeters off the piece that provides tension on the left gear to match that of the right gear.

    Latch attached to polycarbonate brackets.

    Next Steps

    We will need to perform various tests on the latch to determine if the height is correct, if the latch can support the robot, ease of latching and unlatching, and consistency. We plan to test our robot this Saturday at the DISD STEM Expo, which will provide an opportunity to practice latching.

    Fixing Mineral Dropper Components

    Fixing Mineral Dropper Components By Jose and Evan

    Task: Fix any issues with the mineral dropper

    At the STEM expo we saw a clear issue with the mineral dropper: it is very poorly geared and doesn't deposit minerals well. A quick look at the gear configuration revealed that the gears were attached in a poor manner such that there was a lot of gear skippage. To remedy this, we attached a gear-box to the dropper to keep the gears interlocked.

    The way the mineral dropper works is by having a wire attached to the shaft that turns the release be pushed when the robot hits the lander. The wire is attached with a portion of a gear custom cut for the job.

    We need to upgrade to a thicker wire for more reliable shaft rotations. After doing so we needed a different wire holder and we chose a REV wheel. After cutting it and drilling bigger holes to accommodate the new wire we needed to attach it all to the shaft for the mineral release.

    Next Steps

    We need to finish bending the wire and test its ability to open the mineral release when contacting the lander.

    Big Wheel Articulations

    Big Wheel Articulations By Abhi

    Task: Summary of all Big Wheel movements

    In our motion, our robot shifts multiple major subsystems (the elbow and Superman) that make it difficult to keep the robot from tipping. Therefore, through driver practice, we determined the 5 major deployment modes that would make it easier for the driver to transition from mode to mode. Each articulation is necessary to maintain the robot's center of gravity as its mode of operation shifts.

    The position seen above is called "safe drive". During normal match play, our drivers can go to this position to navigate the field quickly and with the arm out of the way.

    When the driver control period starts, we normally navigate to the crater then enter the intake position shown above. From this position, we can safely pick up minerals from the crater.

    From the intake position, the robot goes to safe drive to fix the weight balance then goes to the deposit position shown above. The arm can still extend upwards above the lander and our automatic sorter can place the minerals appropriately.

    During the end game, we enter a latchable position where our hook can easily slide into the latch. After hooked on, our robot can slightly lift itself off the ground to hook.

    At the beginning of the match, we can completely close the arm and superman to fit in sizing cube and latch on the lander.

    As you can see, there is a lot of articulations that need to work together during the course of the match. By putting this info in a state machine, we can easily toggle between articulations. Refer to our code snippets for more details.

    Next Steps

    At this point, we have 4 cycles in 1 minute 30 seconds. By adding some upgrades to the articulations using our new distance sensors, we hope to speed this up even more.

    Up-to-Date Bigwheel Model

    Up-to-Date Bigwheel Model By Justin

    Task: Finish the Bigwheel model

    Updating the Bigwheel model to the robot’s current configuration was a challenge. The new linear slides are not standard parts, so we had to model them from scratch. There was some cleaning up that was needed on the drivetrain of the model. This was mainly attaching floating motors to motor mounts and axles to bearings. These were mainly cosmetic changes, but they help define the purpose of the different parts of the drivetrain. We also updated the intake assembly to our current ice cube tray intake. The structure of the intake was easy to model but the ice cube tray gave us some trouble with its unique shape and pattern. The ratchet latching system was a failure, so a new hook model was needed. The main issue with this was that we custom forged our new hook, so there was some difficulty in getting the model to accurately represent the capabilities of the hook. Another challenge was the mineral storage system. This is made from polycarb pieces and has many unique pieces, so arranging the pieces to accurately show the flow of minerals was difficult.

    In addition to updating the model, we also learned how to show the different movements of the robot with the model. Mechanical constraints were added to allow certain parts to slide or rotate. The one problem we had with this was that there were no limitations to how far something could slide or rotate, so many parts of the model would disconnect and be left floating. After some research, a solution was found. Zero points were created for each moving part and minimum and maximum movement limits were added. Some parts that now can move on the robot are the wheels, superman arm, hook, and linear slides. This allows us to not only show the movement of the robot, but also the limitations of its parts, which can help us visualize new solutions to our remaining problems.

    Next Steps

    Our next step is to wait for more build changes, so we can keep updating the model. Another addition we might make is making stress maps of the robot in different configurations to see where parts might fail. This has been an ongoing challenge of keeping the model accurate when the robot gets updated or rebuilt, and now we finally have a finished model and ready robot for regionals.

    Intake Speed

    Intake Speed By Karina

    Task: Analyze efficiency of our intake system

    A big part of our redesign is improving our intake system. To see where some of the errors may lie, we took detailed videos of our robot intaking silver and gold minerals from a side view, one mineral at a time. We measured the time between when the intake first made contact with the mineral, and when the mineral was directly underneath the rotating icecube tray, and therefore in our control, using LoggerPro video analysis.

    Silver Minerals
    TrialΔt (s)
    10.733
    20.466
    31.233
    41.934
    50.766
    60.634
    70.600
    80.466
    92.133
    100.700
    Gold Minerals
    TrialΔt (s)
    10.234
    20.532
    30.300
    40.533
    50.533
    60.300
    71.433
    80.567
    90.800
    100.433

    On average, silver mineral intake took 0.967s and gold mineral intake took 0.567s, meaning our intake was more efficient at gold mineral intake. Looking at Big Wheel intake frame by frame revealed faults in our intake. Intaking gold minerals went smoothly. For silver minerals, however, the slack in the ice cube tray resulted in it losing its grip on the mineral multiple times before the mineral was firmly grasped. This is likely the result of frictional forces struggling to overcome the elastic force of the flexible icecube tray pushing outwards. In trial 4, for example, our intake lost its grip on the mineral 4 times before it could be considered in our control.

    Next Steps: Redesign Intake Mechanism

    We are assembling a subteam of builders to take on the challenge of designing a new intake system. Some issues we'll have to address include:

    • The slack in the center of the corn-on-the-cob intake

    • The silver minerals slipping on the sorter
    • We'll have to have what changes will be made to our current design. (E-147, Intake Update)

    Reverse Articulations

    Reverse Articulations By Abhi

    Task: Summary of Icarus Movements

    In post E-116, I showed all the big wheel articulations. As we shifted our robot to Icarus, we decided to change to a new set of articulations as they would work better to maintain the center of gravity of our robot. Once again, we made 5 major deployment modes. Each articulation is necessary to maintain the robot's center of gravity as its mode of operation shifts.

    The position seen above is called "safe drive". During normal match play, our drivers can go to this position to navigate the field quickly and with the arm out of the way. In addition, we use this articulation as we approach the lander to deposit.

    When the driver control period starts, we normally navigate to the crater then enter the intake position shown above. From this position, we can safely pick up minerals from the crater. Note that there are two articulations shown here. These show the intake position both contracted and extended during intake.

    During the end game, we enter a latchable position where our hook can easily slide into the latch. After hooked on, our robot can slightly lift itself off the ground to hook. This is the same articulation as before.

    At the beginning of the match, we can completely close the arm and superman to fit in sizing cube and latch on the lander. This is the same articulation as before.

    These articulations were integrated into our control loop just as before. This allowed smooth integration

    Next Steps

    As the final build of Icarus is completed, we can test these articulations and their implications.

    Connecting the Hook to a Servo

    Connecting the Hook to a Servo By Karina

    Task: Connect the hook to a servo

    When attaching the hook to the servo, it was very important that the configuration gave the hook its widest possible range of motion. The open position needed to as far back retracted as possible for an easier lander dismount, and the closed position had to be closed enough so that our robot would not fall off the lander in competition.

    The hook was forged prior to its attachment, of course, so the mechanism had to account for the overextension of the end opposite the hook past the horizontal. To solve this problem, a L-bracket was mounted onto the end of the hook.

    The closed position was easier. The servo rotated approximately 180 degrees (its full range of motion being from 899 to 2100) into the closed position.

    Next Steps: Intake

    Now that the hook system is completed, all that's left is to test it and then mount the intake.