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Iron Reign

Welcome to Iron Reign at Dallas ISD's Science and Engineering Magnet

Articles by section: engineering

Hoverboards and PID

09 Apr 2016
Hoverboards and PID By Caitlin, Omar, Darshan, Tycho, and Max

Task: Continue with the Hoverboard and tweak PID

After the long weekend last week, today was a reasonably relaxed practice. We decided that we could work on anything, as long we stayed focused. The two main foci were the -Robot on a Hoverboard- and fine tuning our PID for autonomous.

Reflections

We experimented with balancing the robot more evenly on the hoverboard to keep it on a straight path and then getting creative with the controls to speed it up. We found that we could effectively rocket it forward by extending and angling the cliff climber while flipping the block dispenser forward at the same time. While it was easy to send the robot forward, there was little we could do to recover outside of just pushing it back by hand. This created a game of hot potato as we passed the robot around from person to person, but was ended rather abruptly when it careened into the table.

If we're going to get our autonomous functional for UIL then we need to fix our PID. We used the parts of the current autonomous demo to check the straight line gyro drive, and went from barely correcting, to crazy oscillations, to a good level in between. This took a decent amount of tweaking for K-proportional, and when we felt we were straddling the line between too much and too little correction we messed around with K-Derivative to be better prepared. After the initial gyro guided line the robot is programmed to do a 45 degree turn towards the beacon, and then fine tune its angle using color blob. The color blob detection seemed to track the selected color accurately, outlining the area in neon green, but for some reason didn't turn to aim at it. If anything it turned away from the beacon. We found a mistake in our error calculation, where leftover error wasn't properly cleared before the guided turn, that we believe caused at least some of the odd turning behavior.

Making a Ports Map

28 May 2016
Making a Ports Map By Omar and Jayesh

Task: Create a list of motors/servos and what ports they're connected to

Very often, when we disconnect a motor or servo (maybe on accident), we forget what port we got it from. This even happened to us today when we unplugged the servo that lifts the trough. Because of this hassle, we decided to write out a list of all the motors and servos on our robot and what port they're connected to so we can refer back to it if we ever forget where we took something from again.

Reflections

This didn't take us much time at all and was easy to do, so we might want to make a lot more of things like these in the future to keep ourselves organized. Organization is definitely something we need to work on for this next competitive year, and even small things like these help out with that.

New tread material test

11 Jun 2016
New tread material test By Caitlin, Tycho, Max, and Evan

Task: Initial tests for new tread material

The standard Tetrix treads and tread inserts aren't nearly as sturdy as we would like. When they snap it's a real effort to put back together stretched over the idlers, and the inserts peel apart, bringing our traction down. The new material is a rubber conveyor belt material from Andymark, and the underside track chain is 3D printed in nylon to mesh with the track drive gears. Outside: high strength high traction rubber Inside: 3D printed nylon to mesh with gears

Reflections

We first glue the nylon sections to the treads, laying them out flat so that some of the nylon hangs over one end and let them set overnight. The next day we bend it into a loop and glue the overlapping nylon and rubber together, and then let that set overnight. This isn't strong enough alone, so we ended up using the awl (used previously in Cascade Effect's game) to stitch at the boundary between two nylon strips, sort of like a thread staple.

Initial tests showed that this design was a huge step up from the tetrix treads, and we're working to make another to complete the pair. One downside is that this design is a much thicker design, and rubs on the underside of other parts that weren't previously a problem.

2016-2017 Robot

15 Oct 2016
2016-2017 Robot By Ethan, Omar, Jayesh, Evan, Tycho, and Max

Task: To build the robot for the 2016-2017 season

As much as we love our robot from last season, Geb, we need a robot that is better able to fit the season's challenges. Our needs for this year are:

  • Manuverable and fast
  • Able to play defensively
  • Can support attachments such as an intake system
For manuverability, we decided to use mecanum wheels.

The cool thing about these wheels is that they enable you to strafe side to side, instead of turning. However, they do require different coding than our normal wheels.


To play defensively against other robots, our robot must be decently sized without falling into the same trap of last year, where are robot barely fit into the sizing limits, and in one tournament, did not at all. As well, it must be heavy enough to not be pushed out of the way by other robots, especially due to our strategy this year (blog post on that later).

Finally, our robot must support attachments. Currently, we are considering a launcher, and intake system, a circulation system, and a yoga ball-lifter. And, to accommodate all of these attachments, our basic frame is a re-enforced square frame.

Experimenting with a Mecanum wheel chassis! #ftcrobotics #omgrobots

A photo posted by Iron Reign Robotics FTC (@team6832) on


However, we are still experiencing problems, such as our chain falling off due to the supports moving toward each other. As well, we probably need to find a better place to put our motor controller and battery.

Reflections

We need to get our robot effectively finished within the next month if we are to go to the Arkansas tournament. As well, we need to add supports to our robot to stop the chain issue. Within the next two weeks, we should have made one or two attachments.

Programming our New Robot

15 Oct 2016
Programming our New Robot By Tycho, Caitlin, Ethan, and Jayesh

Task: Program our new mecanum wheel driving platform

Now that our new robot has been built with a mecanum wheel platform, we can start write our drive code and figure out how to make our robot preform three basic motions: forwards and backwards, side-to-side and to rotate. We decided that, in order to get the best understanding of our robot, how it moves and our code, that we would try to write our drive code through trial and error. However, we did reference some guides written by other various FTC and FRC teams if we got stuck on something and needed to figure out where to start in solving the problem.

Reflections

In order to drive our mecanum wheels properly, we need to first discuss how each wheel is placed on the robot, and also how each wheel needs to move in respect to the others in order move in a certain direction. Each wheel has small rollers that point 45 degrees off of the larger wheel itself. In order to properly set up mecanum wheels, the rollers on each wheel have to point towards the center of the robot.

This is important, because if these wheels are not pointing in the proper direction, then the rollers will begin to fight against each other, causing strange driving patterns that aren't very useful. We learned this the hard way, because when reconstructing the wheel mounts, the positions of two wheels on robot were flipped, causing the robot to drive in circles when we tried to drive sideways.

The main reason we decided to go with mecanum wheels is because they open so many different ways to navigate the field. Robots that properly use mecanum wheels can not only go forwards, backwards and turn, but they can also make a robot move side to side. These three types of movement can be mixed with each other to do even cooler things like move in diagonals or even strafe, which is when a robot moves in an arc while moving sideways. Of course, we cannot use mecanum wheels to their full potential if we do not first understand the first three basic types of movement. Driving forwards and backwards is pretty simple, and it's the same as any other robot; all of the wheels have to move in the same direction. Turning also remains unchanged from other platforms; the left side of the robot has to move one way, and the right side of the robot has to move the other.

However, moving side to side is not really intuitive compared to the others. In order to move side to side, the wheels on either side have to move opposite of each other. For example, if I wanted to, from a top-down perspective, drive to the right, the wheels on the left side of the robot would have to drive away from each other, while the wheels on the right side of the robot would have to drive towards each other. The rollers start spinning away from the center and to the right on the left side of the robot, or towards the center and to the right for the right side of the robot. The forwards and backwards components of the wheels and the rollers cancel each other out, and the robot moves to the right.

Need for ZTE Speed - The Movie - The Game

22 Oct 2016
Need for ZTE Speed - The Movie - The Game By Max

Task: Make a case for the ZTE Speed controlling the robot

While we are still in the early stages of design and it's not wise to make a permanent decision about where the robot's controlling phone will be, we can't let it float freely around the robot like a brain in a jar for much longer or it'll start getting caught in the developing systems. Normally, we could solve this easily by drilling a few holes in an off-the-shelf phone case and bolting it to the robot, but both the robot's design and the phone's code are constantly changing, so this would be far too permanent. We decided that the best way to house the phone would be a custom-made case with plenty of bolt holes to make it easily mountable and removable as well as a front which can be taken off at any time so we can take out the phone to reprogram it without driving ourselves insane.

I decided to make the case a pair of 3D-printed parts: a sturdy base made of t-glase which can be bolted to the robot and can easily socket the phone, and a flexible nylon cover plate which is kept in place by tabs which wrap around the base component but can be pulled out of the way when the phone needs to be put in or taken out.

Reflections

It took a few iterations before we printed the pieces, but the system as a whole is working smoothly. The phone is easy to replace and so far we haven't seen the cover come off once while the robot was driving. The only forseeable issue is with the tabs. Although they are flexible enough for our purposes, they are thin enough that they can be broken if bent too far. Since the face plates don't take too long to print and the 3 tabs left over after one breaks are still entirely capable of holding the phone in anyways, this shouldn't be too much of an issue, but it's still something to keep in mind for the future.

Launching Mechanisms

26 Oct 2016
Launching Mechanisms By Ethan

Task: To build a launching mechanism for the particles

For the 2016-2017 season, particle scoring is really important. During autonomous, balls that are launched into the center vortex earn 15 points each, and balls that are launched into the center vortex earn 5 points. If done quickly enough, the particle scoring can negate most of the advantages another team has - just 8 particles scored during the driver-controlled period is equivalent to scoring all 4 beacons. With a good scoring mechanism, the only thing that your team must contend with is the other team scoring autonomous beacons and/or moving the cap ball off of the field.

So, we must seriously consider all of our launching options. We narrowed our options down quickly:

  • Slingshot - Easy to make, but wouldn't hold up
  • Air launcher/Pneumatics - With our team, bad idea waiting to happen
  • Crossbow - Dangerous, but accurate.
  • Flywheel launcher - Accurate, requires least maintenance, but huge battery load
  • Catapult - Less accurate, but simple and powerful
Of these options, we narrowed it down to the Flywheel and Catapult

Flywheel

Above is an example of a fully functional flywheel. The pros of that design are that it is efficient, accurate, and requires little upkeep. On the other hand, it needs at least 2 motors unless someone is willing to do gear witchcraft. As well, two extra motors will drain the battery (bigly), as we learned from last year's mountain climber. Finally, it can take up quite a bit of space on the robot and weigh it down a lot.
Also, my initial model of it did not function well.

Catapult

We had trouble deciding on a catapult design. Initially, we were considering a more complicated flipper design, but after seeing our sister team's struggle with their design, we decided on a simpler, bungee cord design. The pros of this design are accuracy, simplicity, and strength, but the cons are that it isn't *as* accurate and that the elastic band will need to be replaced.

The coolest thing about this design is that it can be simulated before I change anything, using a catapult simulator. A sample of our catapult can be found here.

Reflections

This add-on is the first of many that we must make to prepare for competition. Next, on the build list, we need to create a capping attachment and intake system. In the future, we should probably speed up our development process if we are to head to the Arkansas regional tournament.

Ready the Artillery

29 Oct 2016
Ready the Artillery By Max

Task: Design a bowl for our upcoming catapult system

We've been experimenting with catapult systems for a little while now, but we're still sorely lacking one of the core ingredients of any catapult system: the ability to throw things. I mean, technically we're lacking the ability to hold what we're trying to throw, but it's the same effect.

In any case, it's an issue we have to deal with, and our solution is good ol' nylon. I went through a few designs for a bowl to hold balls, and the one we're using is pretty much a semicircular shell with a handle which mounts to the arm of the catapult and plenty of holes to lower the weight while keeping it sturdy.

(herecomedatbowl.jpg)

Reflections

The bowl is a great fit for the ball and doesn't seem to interfere with the strength of the catapult, but there are still two issues which we can't address yet.

Firstly, we haven't gotten a loading mechanism planned out yet. We can make the catapult as strong and reliable as we want, but beyond the first ball we're allowed to load for autonomous, it won't do us any good until the robot can actually take balls from the floor and load them into the bowl. That might not seem very pertinent to the design of the bowl, but since it's the only physical interface between the loading mechanism and the catapult, it'll be the first thing to change if the two don't fit together on the first try.

The second issue is just that cleaning out the printed model is an utter pain. Again, this is no reason to change the model right now (and it probably won't be one later on, either), but since we're likely to have at least one more version in order to solve whatever issues we encounter while developing the loading mechanism, there's at least a 90% chance that another catapult bowl will need to have its support structure gouged out over the course of an hour. I just feel sorry for the poor bugger who has to do it.

Yeah, it's probably gonna be me.

Launching Mechanisms Pt. 2

31 Oct 2016
Launching Mechanisms Pt. 2 By Ethan

Task: To improve upon launching mechanism designs

Catapult

First and foremost, we now have one completely functional, terrifying, catapult. The motor mechanism is cannibalized from our sister team's attempt at a catapult, which broke apart on testing.


Flywheel
So, while we don't have a functional flywheel as of yet, we have done the math in order to get it up and working on the first try.

For reference, we need to launch the ball ~1 meter, the frequency of the motor is 2.53 s^-1, and the radius of our gear is 2.65cm.
velocityfinal^2 = velocityinitial^2 + 2*acceleration*change in y
velocityfinal = sqrt(2*9.8m/s^2*1m)
velocityfinal = sqrt(19.6m^2/s^2)
velocityfinal = 4.427 m/s

actual final velocity = 4.427 * 1.25 = 5.534m/s
actual final velocity = 2*pi*radius*frequency
(5.534m/s)/(2*pi*2.53s^-1) = .348m

gear ratio = gear1radius/gear2radius = 2.65/.348 = 1:7.615
However, for simplicity, our needed gear ratio is 1:8.

Reflections

We should advance in building our attachments - if we go to Arkansas, we have <6 practices to go. And, from now on, we need to do the math behind them so we know we're doing them right.

The Robot is a Nautilus Now

02 Nov 2016
The Robot is a Nautilus Now By Max

Task: Make a conveyor shaft to guide particles to the catapult

We’ve thoroughly proven that the tread of rubber bands is an effective method of ball collection, but as of yet it can only move the balls along the ground. We’ll need a way to move them upwards to the catapult bowl’s level. While we could use another motor to push the particles up and over the belt, it could get caught and we’d rather not take up another motor port. We decided to instead make a semicircular tube to guide the balls, with no motors of its own, but instead simply keeping each ball in contact with the center belt as it turns around to move back to the front of the robot.

After measuring how large the tube would have to be to house the ball, it was clear that it couldn’t be printed in one part (not that I would have if I could - the infill would be a nightmare to remove), so instead I made a model for a segment of it which can be printed several times and then bolted together at a few built-in sockets. Each segment accounts for 30 degrees of the 180-degree arc we plan to build. A segment can be seen below.

Reflections

The model prints well, connects easily, and sockets the particles perfectly, but it lacks the friction required to keep them from spinning in place instead of moving up the tube. We were able to solve this by applying a stripe of memory foam to the inside of the tube with double-sided tape.

Parasyte

06 Nov 2016
Parasyte By Jayesh, Omar, Darshan, Caitlin, and Max

Task: Design a collector for the balls

We've spent the last few practies creating a ball collector. The idea was to have our track with the gripping rubber bands reach from the bottom of the robot to our 3D designed ramp. The path would guide the balls to a higher position on our robot to the launching mechanism. We needed to adjust the correct orientation of the support beams guiding the balls, needing to drill new holes and adjust beam lengths.

Reflections

There have been a lot of adjustments we have had to made to the this tread-based system. Starting from an eyeball test of the length, we had to eventuall lengthen the whole tread to fit the whole system. With our length being about finalized, and our entire path about done, We are about ready to attach our launching mechanism and start adjusting the scoring mechanism.

Mecanum Driving

13 Nov 2016
Mecanum Driving By Tycho

Task: Code driving under mecanum wheels

Today, I wrote the whole code for controlling our mecanum wheels. It is entirely fron scratch, and works perfectly right off the bat. This code allows us to strafe, move backwards and forwards, and rotate, in one method.

Reflections

We still have a lot of coding to do, as we're currently working on a particle-launching system. As well, we need to consider autonomous soon.

Intake System Improvements

21 Nov 2016
Intake System Improvements By Caitlin and Janavi

Task: Replace rubber bands with smaller versions and add wider intake area

New intake area is wider than before


At the Scrimmage we noticed that the rubber bands would get tangled as they rubbed against the underside of the catapult bowl, and so didn't reach as far down at the bottom. We untangled them before each match but decided to test out the smaller ones when we had the chance at practice. We were planning on adding a wider area for intake with some circles of treads and rubber bands, but with the long rubber bands they just got completely tangled in each other. So this practice we replaced the long rubber bands with the shorter versions and looked at differences

Reflections

It took a little while to physically pull out and replace each band, but the rubber bands we use are stiff enough that they can be pulled thin enough to slip in without getting twisted up. The single conveyor with the smaller rubber bands wasn't any noticeably worse than the same conveyor with longer ones, and our load rate stayed pretty much the same. We then added the smaller side brushes/spinners on that axle. Originally the longer rubber bands tangled up and threatened to break the belt, but this made it easier for Tycho and Omar to score. The added wheels on the axle make the intake area almost as large as the robot, stretching from wheel to wheel.

Catapult Unfixes

22 Nov 2016
Catapult Unfixes By Ethan

Task: To bring the catapult within size limits and improve it

What Actually Happened: Abject failures

So, the original catapult, when not stuck, performed pretty well at the scrimmage. However, since we opted not to measure our robot at the scrimmage, we didn't realize that our robot was not within the FTC size limits. When measured after the fact, it was 18x19x20 in x, y, and z axes respectively, due to the catapult's position on the robot. To rectify this, we decided to cut the catapult down, and add a new ball-scoop while we were at it.

So, we cut down the catapult arm, and that's where the critical error occurred. I forgot how a lever lever-ed, and completely removed the pull-down part of the lever. And, since I didn't check it afterwards, I continued to make modifications, cutting down the top to 18 inches, and reattching it to the robot. Also, these modifications prevented testing of the robot.

And finally, in the moment of truth, the robot failed to work.

Reflections

In the future, I should probably have someone check on my work to make sure I'm not fouling everything up. As well, I probably should try to not make modifications the week before the tournament.

Autonomous Setup Options

23 Nov 2016
Autonomous Setup Options By Tycho

Task: Create a basic autonomous

Autonomous is one of the things that we tend to be weak on every year, and this year, we really want to get to super-regionals. So, to start off this year's autonomous, we first mapped out a potential path for the robot on the field. We then followed up with programming, using our previous methods like driveForward and driveCrab. So now, we have a basic autonomous program in which we can push the cap ball and attempt to shoot the vortex.

Reflections

We still have a long way to go in working on our autonomous - we need to be more accurate in shooting the vortex, we would like to hit the beacons, and we want to get parking points as well.

Catapult Upgrades

23 Nov 2016
Catapult Upgrades By Max

Get Nostradamus on the horn, there’s a new prophet in town.

Task: Imbue the catapult bowl with infinite power

As I predicted in the article about the first version of the catapult bowl, it’s gonna need a rework. There’s enough room for the catapult system and the conveyor system to fit together on the robot, but the lip of the bowl is too high for a ball to roll into the slot. This is a tough issue to solve: we’ll have to slice a chunk out of the hemisphere of the bowl, but doing so will make a bunch of sharp corners in the area of the catapult which is closest to the rubber bands, and the potential repercussions of the belt and catapult getting snagged on each other in the middle of a competition are catastrophic. I’ve solved the problem as best I could with a very generous rounding over of the points left over after removing the section of the bowl which is blocking the balls.

Reflections

This has solved our problems in interfacing the two systems, but I’m a bit concerned that taking so much material out of the outer end of the bowl may affect the flight path of the particles by providing less resistance to the centrifugal momentum of the ball as it accelerates. We won’t go back to the original bowl based on that knowledge, but it’s still an important detail to keep in mind as we consider our options for scoring points.

Final Catapult

27 Nov 2016
Final Catapult By Ethan, Evan, Omar, and Jayesh

Task: Finish up the catapult before Arkansas

Today marks six days until Doomsday (AKA Little Home, Arkansas), so we needed to finalize everything. For the catapult, Jayesh and Omar fixed my catapult "fixes". However, with the new fixes, the catapult was more powerful, and required recalibration. To adjust to the new fixes, we removed the old stop-mechanism, and replaced it with a wooden one that stops it on the 2nd level of the robot.

As a result of these changes, the arc of the catapult is more horizontal while preserving the height of the launch. This actually gives us a slight advantage in where we can fire the balls from. The only downside of the new design is that it tends a bit to the left.

Reflections

The catapult is good for this tournament, but we need to pursue alternate designs, such as the flywheel in the future. We should also make better prototypes to test.

Combining TeleOp and Autonomous

01 Dec 2016
Combining TeleOp and Autonomous By Tycho

Task: Combine TeleOp and Autonomous code

Today, I combined the autonomous and teleop so that we can demo both more easily. As well, during testing, we now can switch between them seamlessly so that our testing is power. The most important part of this code is that we can configure the autonomous before we launch - telling the robot how many balls we have, how many to shoot, what side the robot is on, and other pertinent options.

Reflections

We still need more code and fixes - our robot keeps having random errors while launching. As well, we have intermittent lag.

Time to Skip Version 9

10 Dec 2016
Time to Skip Version 9 By Max

Task: Make some changes to the catapult bowl

The apocalypse is at hand.

Chaos reigns as the world is thrown into peril; whole nations are thrown into anarchy by the second; and the superpowers of the world, once bitter enemies, have no choice but to band together as a horrid product of our own hubris, a threat more devastating than any which mankind has ever before seen, appears to put a grisly end to humanity:

The catapult bowl is too floppy.

Cut to black. Text appears: VERSION 8.

So, we got a problem. And as the guy who does the bulk of the 3D modeling around here, I’ll be fixing it. In case you didn’t gather what that problem is from the intro sequence, the catapult bowl is a bit too flexible for our liking, which is causing a bit of inaccuracy. To remedy this, I’ve added some simple buttress-type structures to the underside of the bowl to put some more support on the thin section where it seems to be flexing the most.

Reflections

The supports are just what the bowl needed. It’s flexing far less, and there’s been a noticeable increase in the accuracy of the catapult since it’s been added. All in all, this was a box-office blockbuster.

See VERSION 8 starring Adam Sandler as Catapult Bowl this summer in DVD and IMAX.

Beginning the build for the Cap Ball Trapper

24 Dec 2016
Beginning the build for the Cap Ball Trapper By Jayesh and Omar

Task: Give Deadshot flexibility in end game scoring by designing Cap ball launcher

One of the issues we saw in Arkansas was in the lack of flexibility we had in terms of the end game. We efficiently scored balls and beacons, but when our teammate for a specific match could do the same, we lost possible points scored. This led us to conclude that a Cap Ball Trapper, would be necessary for the sole purpose of flexibility. We focused on an extrusion-based system, based on a set from AndyMark. We've rigged up a pair of basic stairway systems, which will form the main lifting mechanism for the Cap Balls, now we have to figure out where to place them.

We followed the Youtube video above to figure out how everything was put together initially, and then expanded from there.

Reflections

The idea of flexibility is a luxury we can consider due to the progress made for the Arkansas competition. The idea is in scoring the maximum amount of points, regardless of the capabilities of our respective partners. The rigs themselves (although they do need some end covers so they don't fall apart) work fine, but we need to figure how it's going to fit into the general scheme of our robot. We have concluded that the rig will require two motors (we're at our limit; hooray traditions). The main goal in finishing this system is in figuring out both its deployment and placement.

Fixing Faulty Encoder

26 Dec 2016
Fixing Faulty Encoder By Tycho and Jayesh

Task: Fix a faulty encoder on our robot

This shows a test of our encoder issues. It might have been a month ago that we noticed a strange behavior in our autonomous code when the robot was moving forward at low speed. It would curve to the right when we were telling it to go straight. We probably would have noticed the problem earlier if we had any kind of subtlety in our driving. But we didn't, partly because the problem goes away when driving at full speed. We did suspect that the problem was in the encoder feedback of the front left drive wheel. In this video you can see how it ramps up to full speed much faster than the other motors. Here we are driving the robot with encoder PID active. But when driving backward, the motor/wheel behaves properly. This indicated to us that one channel of the encoder was working normally while the other was skipping ticks. But the problem could be in the encoder, the encoder cable or the motor controller. Since our motors take some time to change out and we were heading off to the Arkansas State Championship, we decided to simply turn off PID control. The problem goes away when we are simply driving the motors with open loop power levels - proving that the encoder is the culprit and that motor imbalance was not an issue. The problem with just turning of PID control is that we were still getting bad odometry since our method of calculating distance traveled is based on averaging the encoders across the four motors. So we had to adjust our target distances in autonomous based on trial and error instead of proper calculations.

Here we are trying to identify the source of our encoder issues. We swapped the encoder cable and and ports on the motor controller, but the problem stayed with the front left motor. That told us that it was the motor's encoder that was the issue. We confirmed through telemetry that the encoder was giving no ticks when driving forward, but worked fine in the reverse. So we replaced the whole motor and this time it sped up faster than the other motors in both directions. That really mystified us for a bit. Turns out the substitute motor had an encoder that was dead on both channels. What were the odds of that? We'd simply pulled a motor from our inventory and assumed it would be OK. But it must have been one we hadn't needed to be encoder controlled. We finally found a third motor, this time tested its encoder before throwing on the robot, and all is well now. We can now drive the robot under PID control and it drives as expected at various power levels. We need to re-calibrate our blended travel distances with the working encoder, but feel much better about our performance. We can even reliably use run to position commands if we want, though our navigation code doesn't require that.

This just shows the proper behavior of the robot after our encoder troubles were resolved:

Mapping Out Autonomous

30 Dec 2016
Mapping Out Autonomous By Janavi, Tycho, Omar, Evan, and Darshan

Task: Mapping Out Autonomous

To tell the robot how far to move forward we had to calculate our motors RPM. We did this by telling the robot move to 10 rotations forward and calculating how far it travelled. After he RPM we created a model field upon which we designed a set path for the robot during autonomous. One path for red and then one for blue. Both of these paths allowed the robot to shoot two balls and then push the beacon buttons.After testing this we realised that our alliance partner may be better or worse than us at shooting the balls. So we created a method that allowed us to push a,b, or x to change the number of times the catapult fired.

Reflections

We are constantly working to improve the design our Autonomous. Before this, while our autonomous may have worked. It didn't allow us to collaborate with our alliances to create the best path, stopping us from earning the most points possible. Now with these changes we can work together with our alliance partners to complement each others strengths and weaknesses, helping us earn more points. This will also encourage us to scout around and interact with other teams before and in-between the matches, letting us create a even more detailed scouting sheet.

Cap Ball Lift

12 Jan 2017
Cap Ball Lift By Omar, Jayesh, Darshan, Evan, and Max

Task: Build a lift to try cap-ball scoring

Although we're confident in our robot's ability to shoot balls and press beacon buttons, we decided that in order to be competitive, we should try to score the cap ball. The lift would have to be strong enough to lift the surprisingly heavy ball, but also not take up too much space. Our robot, as like every year, is very close to the 18 inch size limit in all directions, so we needed to think of a volume-saving method of mounting the lift. After considering several methods and remembering other lift mechanisms that we'd seen at previous competitions, we decided to use a series of sliding extrusions. It's a common design and not up to our usual standard of flair, but it's relatively small, flexible in terms of mounting, and only requires one more motor, bringing our total up to seven. We first visualized how we'd mount the lift:


(We went with a mix of both)

Using a YouTube video guide, we were able to assemble two columns of four extrusions each that slide up when pulled by a tough string, which is wound around a spool connected to the new motor. It is mounted on top of the robot rather than on a side because we had the most clearance in the vertical direction. It then rotates forward and stands in the correct position, the motor rotating with it. After several rounds of testing, we decided to use a faster motor, and it proved to be successful in speeding up the lift's ascent.

Reflections

Although it won't be ready for our qualifier, we've made very solid progress on this lift. There are several problems which still need to be tackled. First, we need to figure out what we're going to use to actually grab the cap ball. The lift is useless without it, and even if we use some simple pieces of wood and a servo, there needs to be something there. Second, there is a large space between the rotation point of the lift and the ground, which means that it must somehow reach down in order to wrap around whatever claws we devise around the ball.

Motor Controller Mounts

12 Jan 2017
Motor Controller Mounts By Ethan, Darshan, Max, and Tycho

Task: Prevent static shocks to our robot

Throughout the year, we've dealt with static issues with our robot, as shown here and here. And, now that we've pretty much gotten autonomous and the lift out of the way, the static was our only remaining issue.

To prevent the static shocks, we needed to isolate the motor controllers and other parts from the metal section of the frame. This was achieved by adding a polycarbonate shield on each side, and mounting the corresponding motor controllers. However, we had to partially remove the swinging arms that we created in the last post in order to mount the siding. We plan to add LEDs on each side of the robot to give the robot some "bling".

Reflections

The polycarbonate siding in conjunction with staticide should give us a huge advantage in the robot game for the Jan. 14 tournament. As well, it may net us some design points, as it is a solution to a problem that many FTC teams suffer from.

Introducing the New Particle Accelerator

22 Jan 2017
Introducing the New Particle Accelerator By Max

I was going to make a Windows 10 joke but then we stopped using the catapult at version 8.

Task: Design a flywheel for a new system replacing the catapult

So while our catapult was good, we needed something better. It frequently missed and had other issues due to it being dependent on elastic bands that can lose tension over time. It would occasionally miss balls from areas it would usually be able to shoot from. As well, it was just a little dangerous with the metal arm snapping up and down.

At the beginning of the year, we had toyed with the idea of using a flywheel on our robot, inspired by videos such as this, as well as other competing teams at our Wylie and Ellis Davis Field house qualifiers. So, finally, we decided to create a flywheel launcher.

We tested numerous versions of this flywheel. We printed out the same design with three different materials, high density nylon covered in foam tape, high density ninjaflex with 35% infill, and low density ninjaflex with 20% infill. We decided on the last one, as it accelerated the ball the fastest without slipping. We also designed a particle guidance system so that the balls would be more accurate in making the vortex shots.

<infomercial>

Introducing: The Iron Reign Particle Accelerator 1.0

This beautiful piece of machinery is a particle accelerator, which has a huge, ninjaflex, 20% infill flywheel to take all of the particles off the field, and jettison them to the moon (and back down into the vortex). We've revamped our intake system so that we can control the balls going into the accelerator. All of its important parts are designed and 3D-printed by Iron Reign. It is quite literally the best attachment we've ever designed for our robot, and probably could launch people into space faster than NASA can at the moment.

</infomercial>

Reflections

We still need some finetuning in our code for the flywheel, as our autonomous isn't designed for it yet. As well, we'll probably run into some unexpected issue at the tournament, like we always do.

Return to Machine Vision

29 Jan 2017
Return to Machine Vision By Tycho

Task: Prepare to reintegrate machine vision

A year and a half ago while the new Android-based platform was still in pre-launch, we were the first team to share a machine vision testbed on the FTC Forums. That color-blog tracker was implemented with OpenCV on Android, but with a different low-level control system and robotics framework. Then we integrated OpenCV into our implementation of ftc_app, which was in turn based on the great work of rgatkinson's team supporting Swerve Robotics. Our main game repo for FIRST RESQ was also open sourced and we gained a lot of experience using it. But we had many issues that prevented full usage of the capability. There were problems with the whole control system that created extremely variable loop times which really challenged our custom PID implementation. On top of that, we found that in many tournaments the beacons were not working, or the lighting was too bright and our camera was being flooded by the white shell of the beacons. That made it an unreliable solution.

So this year we switched to the modern robotics color sensor as a slightly more reliable method of detecting the current color while up close. This also gave us the ability to add color sensors to both sides of the robot so we no longer have to turn around when on the blue alliance. And we found we had good-enough navigation based on calibrated odometry so that we could get into position without color tracking.

But now we need to go ahead and try to re-integrate our previous machine vision code and see if we can improve on the situation. We also need to at least try out the Vuforia object tracking capabilities, even though we've set that as a lower priority because we know that specular reflections are likely to be a problem under varying lighting conditions at different competition spaces. We've noticed this problem at a couple of spaces due to the marker placement behind the planar polycarb of the border walls. So we don't actually plan to rely on this as a primary means of navigation and positioning, but we should try it out and see how robust it might be.

We still want to use machine vision to possibly track beacons and particles. We are hoping to track particles to create an autonomous behavior that triggers during teleop so that a particle near the front of our particle collector can be automatically approached and pulled in without operator intervention. This should help since picking up particles on the far side of the robot from the drivers is very difficult because of blocked sight lines. We want to use color tracking to make sure we don't pick up opposing alliance particles.

Research / References

I checked out Vuforia and there is no ability to track based on color. So we need to use OpenCV again, but when Vuforia is present it also locks up access to the camera. Fortunately there is now a way to get a frame from Vuforia and reformat the image data for OpenCV's use.

I plan another post to document the actual steps we went through. Stay tuned. If Vuforia proves troublesome, we might revert to getting our image from a camera preview just like last year. Though that would mean messing around with the Android manifest and the layouts in the main FtcRobotController folder.

Fly Wheel 2 - Fly Harder

08 Feb 2017
Fly Wheel 2 - Fly Harder By Max

Task: Create a backer rail to guide the particle as it fires

Our work on the flywheel design has been an effective proof of concept, and now we need to work it in to the rest of the robot. However, just like with the catapult, there’s a couple issues to iron out before all the pieces can start moving in a way that doesn’t make the robot implode.

Most notably to the 3D modeler in me, I fear that our current rails which we use to guide the ball as it is sped along by the flywheel might get caught on the rubber bands of the belt which collects the balls. Both ends of the rail have sharp angles which can easily catch on the bands, and it doesn’t really help that the flexible nylon of the rails means that a rubber band that is particularly stubborn in releasing it could turn our launching system back into a catapult of sorts again.

The fix was quite simple: I used Creo to take out the piece of the rail which ran the greatest risk of being caught, and got rid of some extra bolt holes too since I happened to be in the neighborhood.

Reflections

Not much to report on this one. We’ve printed and tested the model with no catches, and it also seems that the changes to the rail have had no effect on the speed or accuracy with which we can fire the ball. Overall, this one was a simple success.

Building the Fly Wheel Launcher

10 Feb 2017
Building the Fly Wheel Launcher By Jayesh, Omar, Darshan, Evan, Tycho, and Max

Task: Create a particle launcher with a higher scoring rate

The first particle launcher we saw by another FTC team was actually a crude flywheel and rail design back in October where the rail was a cut up PVC elbow. Back then we considered a number of different designs including impact launchers, catapults, flywheel + rail systems and dual flywheel shooters like our sister team built. We decided to go with a catapult design because Max had experience with catapults and knew that they could create very repeatable trajectories.

Our catapult has achieved those reliable trajectories. We operated it with a choo-choo mechanism that allowed us to fire and re-cock without having to change direction, so that made reloading easier and faster that it might otherwise be. It accurately scored, with consistent ballistic trajectories, however, the system had problems with ball loading when our 3D printed catapult bowl kept failing due to layer separation. As a result we had a lot of misfires and had to replace our bowl often. So our moderate cycle rate and our misfires meant we actually scored only about 4 balls during our average teleop phase. As the season progressed it became increasingly clear that we would have to radically improve our center vortex game and that was driven home when Technical Difficulties and Technibots crushed us with their world record score in the finals match at our first qualfier.

So we decided to move on to a flywheel-based design, knowing that we would likely be sacrificing some accuracy for a much greater cycle rate. We knew that dual flywheels tended to have even greater issues with accuracy due to their extremely short contact period and the chance that one or both wheels would hit a slot in the wiffle ball. We saw direct proof of this as our sister team, Imperial Robotics, struggled to get their dual-flywheel design to work consistently. And Ethan had attempted to build one very early in the season, but never really go it working. So we decided to design with a single wheel with a semicircular ball guide or rail. Max created a custom 3D design for both the flywheel and for the rails. The rails were printed in nylon, our preferred structural plastic. He printed three different flywheels for testing. One was in nylon meant to be covered with foam for compliance. The other two were printed in Ninjaflex (urethane) at different infill densities. The foam on the nylon version shredded at the RPMs we were using. We probably could have found a better adhesion solution, but found that the low-density Ninjaflex version worked beautifully and has stood up to extensive testing.

Reflections

The continuous improvement of designs is a constant focus we adhere to. Previously we'd gone through two major revisions of our catapult system, with a whole bunch of minor modifications, and that system got us qualified for the North Texas Regionals. We saw the pros and cons, and eventually saw fit to change the system to score more points in the long run. We are now able to score around 75% of the balls we shoot. The key is in how quickly we shoot now. Before we would have to collect balls, turn the robot around, load a singular ball into the scoop, and shoot. Now, we can shoot 4-5 balls right after another without turning around. This will allow us a much greater center vortex scoring rate as we aim to be one of the top teams at Regionals.

Backups and Shields

21 Feb 2017
Backups and Shields By Caitlin, Omar, Max, and Tycho

Task: Build a backup flywheel track and remount side shields

Previously, our side shields were zip-tied through 4 bolt holes on tetrix pieces per side, and we had taken one off to reach our drive system. When putting it back on to fine tune autonomous we took the time to cut out space for a wrench and bolt it on. The holes were already the correct size, we just had to line them up with the mounting position.

Omar spent a good amount of time inspecting our current track in order to replicate it accurately. Unfortunately, it took him a few tries to get it. We want to have a second copy available in competition if we get hit around too hard or something snaps. One weakness of our previous catapult design was that the bowl broke in a way we couldn't repair, andwe don't want to be in that situation again.

Reflections

While It was easy to mount one side of a shield, the other proved to be difficult. The pre-existing drill holes almost lined up, zip ties had enough give, but the bolts definitely didn't. We had to widen the area but it's much more secure now. When we got it to workon the left shield, we clipped the ties holding the right side up and did the same thing

Vuforia

18 Mar 2017
Vuforia By Janavi and Tycho

Task: Use Vuforia to enhance autonomous

We use Vuforia and Open CV vision to autonomously drive our robot to the beacon and then click the button corresponding to our team's colour. We started this by getting the robot the recognize the image below the beacon and keep it within its line of vision. Vuforia is used by the phone's camera to inspect it's surroundings, and to locate target images. When images are located, Vuforia is able to determine the position and orientation of the image relative to the camera.

To start setting up our robots vision, we watched Team 3491 FixIt's videos on Vuforia to help us understand how to set it up. After finishing the code for following the image, we went to go test it out. We found out that we had accidentally coded the robot to follow the picture by moving up and down, as we had coded the phone for portrait mode instead of landscape. After fixing that, we tested out the robot and it ended up attacking Tycho by running at him and the image at full speed. Apparently, we had accidentally told the robot to go much farther than it was supposed to go by placing a parenthesis in the wrong spot. We tested the code one more time, only this time I held the picture while standing on top of the chair. Luckily the robot worked this time and was able to follow the image both ways.

Reflections

We would like to explore the uses of Vuforia+OpenCV. We are considering using it to determine particle color as well as using it to view the images beneath the beacons.

OpenCV

18 Mar 2017
OpenCV By Ethan and Tycho

Task: Implement OpenCV in autonomous

Last year, we had some experience with OpenCV to press the beacons, and this year we decided to do the same. We use OpenCV to find the color we are looking for on the beacon in conjunction with Vuforia. First, it detects the search pattern in the view with vuforia, then isolates that area and finds the side of the beacon with the correct color. Our code is based off of FTC team 3491, Fixit.

In a previous post, we talked about OpenCV and Vuforia research, as well as how we plan to use it in the robot game. And now, I am happy to say, we have implemented it partially in our autonomous. We can now figure out what side a specified color is on the beacon using our new phones, the Galaxy S5. (Side note - do not update them to Android Lolipop if you want to use OpenCV, it will not work.)

Reflections

In the future, we would like to implement OpenCV so that we can detect the color of a particle during autonomous and pick it up to shoot it. However, we probably don't have time to program it before Super Regionals.

Contact Us

E-Mail: ironreignrobotics@gmail.com Website: In the address bar