Day 6: Shooter Prototyping

Prototyping

Double Wheel Vertical Flywheel

The design of this shooter is based around two rollers feeding into two wheels that spin rapidly, compressing and shooting the ball into the goal. When we tested this prototype, we found it shot very wildly. We figured we needed another wheel above the first two to act as an active hood in order to improve accuracy. We then cut into the plate to make room, and lasered new plates. This new design worked slightly better, but it needed more compression, so new plates were lasered and assembled; however, we ran out of time to test it and will test it next time we meet.

Testing:

Double Belt Shooter

Today, we worked on prototyping a polybelt shoot using a design which was designed outside of lab hours. We began by modifying the design to work alongside the polybelt, as the original design assumed that the center to center distance between shafts could change. After changing the design and cutting new plates, we assembled the shooter. We used a 775 Pro motor with a VersaPlanetery gearbox with a 5:1 reduction. After testing it and finding that the roller speed was too slow, we replaced the 5:1 with a 3:1 and found an immediate improvement. We also increased the compression on the balls on our feeding mechanism by adding polyurethane strips to our feeder plate. While our shooter was able to shoot balls, accuracy was low and there was a significant amount of variability between shots. We were not confident about what the issue was, but we now are sure that we need to provide more energy to the balls and in a more efficient manner.

Testing:

Retrofitted Dropshot Shooter

Early in the season we modified dropshot to shoot the fuel balls. We are now working on a new version that will have a powered feeder and new rails to shoot the ball. We haven't finished assembly yet.

Programming

Robot Programming

We debugged some code that was written last build and got it to run on our prototype drive base and we also fixed an issue on our other development board by replacing the radio. Also, the web configuration code that we used in 2015 was ported to this year’s code base for easy constants configuration. With all of the prototypes we were working on, the github started getting messy, so we cleaned it up by branching and adding more files to the gitignore.

Camera Calibration

Today we worked a lot on Camera Calibration. In the morning, we got some code that allows OpenCV (the library we use for calibration) to directly communicate with the Pixy Cam. Other than some small fuzziness at the bottom of the image, it seems to be working well. In the afternoon, we merged that code with the calibration code. Also, we mounted the dot grid that is used to calibrate the camera, on a piece of wood, so it is flat and can consistently calibrate all of the cameras.

Vision Targets

Today we started to build a 1/5 scale model of the high goal of the boiler. What we did was laser cut a CAD of a circle, twice. What we need to do next meeting, is put up the support beam in the middle, and wrap the whole thing in paper and reflective tape. This should be an accurate representation of the boiler that we can use.

Day 5: Strides in Prototyping and Testing

Prototyping

Shooter

Today we worked on assembling and improving the shooter. After assembling a plethora of VersaPlanetary gearboxes, forming polycord, and machining new hubs for the flywheel, we managed to assemble the prototype. After testing it, we found the real world version to have varied from the CAD, and the compression on the flywheel to be too much. We recut the two shooter side plates to allow for more reasonable levels of compression. We then hooked the prototype up to a mock drivebase and speed controllers. When we tested it, we found that the shooting was inconsistent, most likely due to dead space between the feeder and the flywheels. We tried killing one side of the feeder and changing to a fixed plywood side to lower the variability. While the variability was removed, the spin increased so this plan was immediately scrapped. We then tried to add a makeshift barrel, around 6 inches in diameter and in length. This barrel significantly increased our shooting accuracy. Later, we will have to choose whether or not to have a wide shooter or multiple separate flywheels.

Fuel Intake and Hopper

Today we made great progress on the intake and the hopper. We assembled the updated design from yesterday, and it while it was better (faster, more balls made it over the bumper), we still had the issue of some balls becoming stuck in a "dead zone" and not fully clearing the bumper. To fix this, we decided to try putting 8 thick zip ties on the top roller with about two inches of uncut length, in order to kick the balls up and over the bumper when they got stuck. The results were fantastic: the intake overall worked much faster and balls never got stuck anymore. It seems like this is close to the design that will be implemented in the real robot later on.

After thoroughly testing the intake, we began work on a prototype hopper that would sit directly behind the intake and hold about 150 balls. This prototype has a sloped floor, which will help funnel balls to the back of the robot so we can continue to intake efficiently and feed into the back conveyor belt that will lead to the shooter. While the hopper was fully assembled and ready for testing, we did not get a chance to try it on the practice drivebase because it was being used for the shooter prototype. For the future, we will test the combination of the intake and hopper, and continue iterating those designs. We are also considering prototyping a hopper with a powered conveyor belt floor, to agitate the balls and feed them towards the back even faster.

Testing:

Gear Intake

Today’s build was essentially a continuation of what we did yesterday. We finished putting together the pieces that were CADed previously and fine-tuned the claw system so that it could consistently pick up gears and manipulate them in 360 degrees. One special feature of our design is that, even if one claw is out of position, the locking mechanism is still able to prevent the other individual claw arms from moving around. Although this design works extremely well as it is, the next step will be to condense it significantly so that it can meet the size constraints of the robot.

Drivebase

Today we nailed down an initial version of our drivebase which included the weldment, electronics baseplate, gearbox, and wheels. To finalize our design, changes may have to be made to the frame dimensions to accommodate both the ball and gear intake as well as the bumpers. Moving forward, our priorities are to pocket the baseplate and waterjet it out of 1/8" aluminum to save weight, design new mounting provisions/supports for the bumper rails for easy access, and potentially modify the main breaker placement which is currently positioned in the bumper rail.

Climber

After mounting the “comb” onto a shaft, we were ready to begin putting together the climbing prototype. However, we soon ran into some problems with the VersaPlanetary gearbox we constructed. After taking it apart and putting it back together (with a 10:1 gear ratio), we were ready to restart testing. At this point we ran into another problem as our setup proved to be unstable, making it impossible for the prototype to run smoothly.. We lasercut new, larger sidepanels and attached them to a 2×4 for stability. Next, we recut the metal bar we had used to stop it from interfering from the turning of the comb. Finally, we were ready to attach it to Dropshot’s drivebase, set up a hanging station, and start testing. While the prototype could successfully grab and hold onto the rope, it just did not have enough power to life the entire robot (even after changing to a 50:1 gear ratio in the VersaPlanetary). Looking toward the next build, we’ll have to find a way to increase the prototypes strength and speed.

Full Robot Mockup

The team created a quick mock up of the robot that features an intake on the front and shooter in the back. A large hopper made of polycarbonate pops out to over the bumpers to maximize its volume. A system of polycord or belts pulls the balls to the back of the robot then up into the shooter. It not a finalized design but serves as a start to get an idea of how much space subsystems like the bumpers and drivetrain take up so they can start being manufactured.

Programming

Robot Programming

Today, we fine-tuned a PID control loop for the intake. PID is a control algorithm that maintains a constant RPMs on a motor, regardless of motor loads. For example, a ball launcher’s motors may slow down when balls are inserted due to the increased load. PID would keep the motor’s RPM constant when a load like a ball is inserted.

We also rewired the encoders to connect to the RoboRIO instead of from the CAN Talon. At the moment, we are running our PID + feed forward loops off the RoboRIO (instead of the CAN Talon) and need the encoders to connect to the RoboRIO. While we can get encoder values from the CAN Talon, we need perfect time synchronization for the control loop on the RoboRIO, which we can accomplish by connecting the encoder to the RoboRIO.

Camera Connectivity

Today, we continued on the previous build’s progress, and decided to continue working on SPI. First, we connect the PixyCam to an Arduino and used the Arduino library to see if it worked correctly with the Arduino, as it hadn’t been working with the RoboRIO. Our test was successful, and the PixyCam worked as expected with the Arduino, leading us to conclude that there was a problem in the communication between the PixyCam and the RoboRIO. We connected the RoboRIO and Pixy pins to an oscilloscope to ensure that data was being transmitted correctly. After a few minutes of trying to get proper data, we realized that the PixyCam only broadcasted data when it saw an object; when no objects were detected, it would only send null bytes. This was the reason for the issues yesterday; when we got null bytes, we thought there was a communication error with the Pixy, as the documentation did not indicate that no data would be transferred when no objects were detected; we expected frame separators, but none were sent. After realizing this, we put a ball in front of the camera, which had been programmed to recognize balls, and updated our RoboRIO program to search for objects in a loop. At last, we were able to successfully retrieve object metadata, but we encountered connectivity issues between our driver station and the RoboRIO and were not able to finish our code. This build, we were able to get our program to parse the Pixy’s object broadcast data. Next build, we plan to finish our SPI driver by parsing the frame separator indicators, so we can recognize when there are multiple recognized objects in a single frame.

Day 4: Iteration of Prototypes

Prototyping

Double Wheel Vertical Flywheel

As we proved this flywheel could attain a high throughput, we transitioned today to begin testing different wheel types and compression as well as the conveyor system. In the process of setting up the next prototype, we found we lacked enough polycord pulleys, and machined more out of some delrin stock. We scavenged the 3:1 VersaPlanetary gearboxes from our previous prototype. While we did not have enough time to finish developing the prototype, we have all of the pieces and can finish it quickly tomorrow.

Fuel Intake

Taking the intake design from yesterday using two polyurethane rollers, we laser cut and assembled it, discovering that while it was able to pull balls up and over the bumper, the balls sometimes got stuck. the compression was too little on top of the bumper and it sometimes got stuck. The compression seemed to be too little at the top of the bumper because we didn't account for the bumper compressing alongside the ball, so we went back in CAD and redesigned the geometry of the upper roller to have increased compression. We are still in the assembly stage of the new and improved version, so we will see tomorrow how well it works with the improvements. For the future, we still have to see how effective the new design is before we CAD the real intake for the robot, but it is likely that this will be the preferred design because of the simplicity of having just 2 rollers.

Gear Intake

Throughout the course of the build today, we worked on constructing the 3D CAD design that one of the students made the day before. This worked out well because we were able to get the whole thing laser cut and fully constructed relatively quickly. Although this design seemed to be very similar to the previous version, a new key feature was added: A locking system for the claws while they are grabbing onto the gear. Although we were not able to fully test the design today, these improvements should theoretically allow us to manipulate the gear in 360 degrees, something we were not able to do previously. At the build tomorrow (Saturday), the main focus will be to finish building the prototype and look at potential ways of packaging the design give the tremendous size constraints presented.

Drivebase

Today we finalized the CAD Design for the Drive Gearbox, which is now almost ready for manufacturing. We started by pocketing the gearbox plates, a method used to reduce weight while maintaining the structural integrity of each plate. Our two gear ratios are 15:48 and 28:35. We decided to have a two stage gearbox with a dog shifter in anticipation of heavy defense, allowing the robot to have speed and maneuverability based on the situation. We also added spacers, an intermediate shaft, and designed a new front gearbox plate. Through the design of the gearbox plate, we were able to save 0.04 pounds in a game where the robot weight is inversely proportional to its speed.

Regarding the drivebase weldment, We modified it to have a cut out in the back. The gearboxes will sit in the two cutouts in the back corners and the gap in the middle will be for a gear intake mechanism..

Climber

Today, the rope-climbing project finished prototyping a “comb” to grab the rope as well as housing to connect the comb to the robot for testing. We completed the comb by measuring the diameter of the string to find the distance between each prong of the comb. After this, we cut these parts out and tested it by ensuring that rope with knots would successfully hook onto the comb. Besides this, we also created the housing by attaching a VersaPlanetary enabled motor to a wood structure. We then connected the motor to a shaft by using gears and bearings. At this point, we just need to attach the comb to the shaft in order to finish assembly and begin testing.

Programming

Camera Calibration:

After manually calibrating one camera with limited success, we decided to automate the process to make calibration quicker and more accurate. The goal of the project is to have the OpenCV calibration code to read the camera input automatically so that we can see what angles will work for calibration before we take the picture. Today we downloaded all the necessary software needed to run the calibration program (OpenCV, Eclipse C/C++, MinGW, etc.); however, we did not finish this. Needed for next build is to set up Eclipse with a compiler and Download all the premade libraries for OpenCV. After that, we can edit the code to make it more user friendly, by having it connect directly to the Pixy Camera, and improve calibration.

Camera Connectivity:

Today, we deployed multiple test programs to an old RoboRIO to test our serial driver. Unfortunately, we ran into many issues early on. We then created another program to dump raw SPI input data to attempt to diagnose the issue: we noticed that we were only receiving null bytes (0x00), perhaps due to an SPI protocol error. We found that this occurred because the SPI connection hardware had a loose contact issue between the RoboRIO’s pins and the header pinout; after this was fixed, we received (0xff) bytes. Unfortunately, even after attempting to replicate the protocol according to the description, we could not get the PixyCam to send us anything other than (0xff), which was oddly not documented in the protocol information page. However, we suspected that the issue may stem from WPILib’s abstraction of the SPI interface itself; thus, we plan to implement a PixyCam SPI driver in C/C++ based on a low level library that accesses the serial port directly. In addition to working on SPI, we also worked on our `libpixyusb` interface, attempting to run the sample program. Unfortunately, we received an error about a failure to transmit/receive data over USB; we traced down the issue in the libpixyusb source code to the low level USB handshake. Getting `libpixyusb` to work reliably on the RoboRIO will likely be extremely difficult, possibly even requiring custom drivers and a kernel patch; the exact same code works as expected on an Intel x86 laptop, but when cross-compiled onto a RoboRIO with the FRC C/C++ toolchain, it encounters this unexpected error. After evaluating the pros and cons of both methods of connectivity, we decided to continue to pursue SPI rather than USB.

Robot Programming

Last workday, we tried deploying robot code to the RoboRIO but ran into problems deploying the code due to conflicting libraries for the CAN Talon motor controllers. After removing the conflicting drivers, we were able to successfully deploy the robot code. These changes are reflected in the latest commit on Github.

We then successfully deployed the code for the shooter prototype to the RoboRIO, but faced problems with maintaining a constant RPM. We used a basic feed-forward controller, which should set a near-constant RPM, but we measured drastic fluctuations in the RPM. We hypothesize that this is because the encoder is returning data at a different rate than the robot is running, leading to discrepancies in the measured RPM. To fix this, we will try connecting the encoder directly to the RoboRIO’s digital inputs instead of to the CAN Talon.

Waypoint visualizer:

We worked on an autonomous mode path simulator. The app lets a user enter waypoints and speeds and plots out a path that the robot will take. The app also supports animating the robot's movement. We also worked on implementing a radius feature into the program that would allow the robot to round corners. This app is a vast improvement over the current method of programming paths which require trial and error. With a helpful web interface, we will be better equipped to plan auto routines before we even test them, which allows us to develop before the robot is built. It’s not done yet, but we have made a lot of progress:

Day 3: Progress in Prototypes

Prototyping

Double Wheel Vertical Flywheel

Today, we worked on assembling the Double Wheel Vertical Flywheel. Taking the parts from last build, we assembled it using the new VersaPlanetary gearboxes and encoders we received. We assembled the flywheel to our previous spec, but we had problems with the gears we had in stock. We changed the ratio in CAD and laser cut a new plate. After doing so, we assembled the flywheel. While the flywheel worked well after changing to polyurethane, the conveyor system failed. Rather than cutting a new plate, we cut a bearing hole and inserted a hex shaft on the inside of the polycord, essentially acting as a tensioner. This worked relatively well, but needs further refinement. We did prove our concept, and will further iterate to better understand how best to integrate our design with the robot.

Testing:

For the Double Wheel Variable Compression Vertical Flywheel, we assembled the majority of the pieces and only need to insert the wheels to begin testing.

Fuel Intake

We finished assembly and began testing the belt intake, which was very fast when pulling balls in, but protruded several inches beyond the bumper. We began to design a new intake today, which will be much more compact and will therefore allow for a larger hopper and more room for other systems. This intake uses no belts, and two polyurethane rollers pull the balls up and over the bumper into the hopper. This removes the inefficiency and added complexity of belts, and makes the whole design cleaner and simpler. The intake's design is finished in CAD, but it has not been built or tested yet. On Friday we will laser cut it, finish assembly, and test it to see how effective it it..

Testing:

Gear Intake

The Gear Intake development process continued today with the construction of a recently CADed design that has an inner slider in order to pinch the gear between the claws and itself. This process was difficult because the .25” plyowood that was used for construction is actually .2”, so the original design needed to be modified slightly so that all the pieces would fit together. Other small improvements involved adding polyurethane strips to the inner slider and the claw so that the whole system grips onto the gear well.

Testing:

Drivebase

We finished an initial weldment of the general structure modeled after our 2014 robot and the side rails/bearings/housings modeled after our 2016 robot. Taking bumpers and an intake into account, the frame was dimensioned to fit within the 36" by 40" by 24” size limit.

In addition, we designed the drive train gearbox in CAD with 2 CIM motors per side in a 2 stage reduction with a dog shifter and pancake piston to have 2 speeds: low gear for pushing force and high gear for maneuverability. With the design almost done, we only have to add spacers, intermediate shaft, standoffs, screws and nuts, retaining screws, and pocketing to the CAD (members can access the design from pdm under the name 254-17-A-0300 Gearbox if you want to see or help design it).

Climber

Today, we designed and began to build prototype mechanisms for climbing the rope. The prototypes for actually holding onto the rope included variations combs with differing spacing. We began working on a standard mount for each type of prototype climbing roller. We decided to use a VersaPlanetary gearbox in our build, using a gear ratio of 1:90 to heavily reduce the rpm of the motors from ~18,000 RPM and increase torque to ensure the robot could lift itself. We then assembled the multi-stage gearbox, attached the motor, and soldered the battery leads. Lastly, we began the process of building a frame and prepared the parts to completely assemble the mounts next build.

Programming

Control Board

On Wednesday, we met up and worked on control systems for recent prototypes and we also continued developing pixycam communication. We added three talons to the prototype board to support the growing complexity of prototypes.

Robot Programming

With a prototype board ready, we added feed-forward PID control to our two-roller shooter prototype. PID is a control loop that keeps a constant motor speed, allowing us to effectively test the shooter prototype.

We also rewrote a majority of our code using elements from last year’s code, to avoid re-inventing the wheel. The new code is far more scalable and efficient. In particular, we implemented Loopers, a structure that runs code extremely fast, and compartmentalized our code into the various (potential) subsystems on the robot. We also discussed code conventions to ensure uniformity in the code down the road.

However, we had issues with compiling and deploying the code due to issues with the motor controller driver. We’re resolving those issues down the road.

Camera Connectivity

We worked on camera connectivity, finishing a testable version of an SPI driver built on WPILib for the RoboRIO. Previously, we built a native library that allowed us to communicate with the PixyCam over USB and wrote a JNI wrapper to let us invoke the native code from Java, but today we encountered issues when connecting to a physical PixyCam. Rather than debugging the USB connection, we decided to ensure that we could build a reliable SPI driver first, as we are confident that we will be able to communicate with the camera over SPI. Though a USB interface would be optimal, it is significantly complex and we plan to work on that functionality once the SPI driver is confirmed to work as expected.. We added a new pinout to the PixyCam and connected it to an old RoboRIO board for testing. To help with testing, we connected the PixyCam to a computer and trained it to recognize the yellow game balls. In the upcoming builds, we will proceed with testing our SPI driver with an old RoboRIO so we have a working method of connection for this year’s code.

Day 2: Prototyping

Today, we continued our work on prototyping designs for the shooter, intake, and drivebase. Our programming team also worked through a variety of projects including camera calibration and configuring the RoboRIOS.

Shooters

Double Wheel Horizontal Flywheel

We assembled the feeder for the horizontal flywheel shooter using three wheels of two different sizes to optimize contact with fuel balls. We determined that we would either use polycord or rollers for the feeder. However, due to availability of resources, however, we decided to prototype with a wheel roller. The horizontal flywheel was ready for testing but is still waiting on more planetary gearboxes.

Double Wheel Vertical Flywheel

Today we continued working on developing a double wheel vertical flywheel. In the process, we tried to optimize throughput with the limited space available on the robot. Initially starting with a hand loaded prototype, we combined the shooter with a conveyor prototype to remove the variables of human error.. We managed to design and laser cut the sidepanels for the prototype, and began assembly. We have organized the VEX Pro VersaPlanetary gearboxes and will implement it on Wednesday.

Another project based off a double wheel vertical flywheel aimed to optimize the best materials and fuel compression to maximize accuracy and shot speed. We spent the build designing a model in Solidworks to later be laser cut.. By the end of build, we acquired all the materials for the prototype including the 80/20 Extrusion Material, T-nuts, modified Versa Side Bearing Motor Gussets, 2 x 4 Wood Blocks, Bearings, and laser cut to design ½” Plywood.

Catapult

We improved the catapult and eventually hit an accuracy rate of 15/15 into the high goal. The improvements we made include:

• Adding a stronger shaft

• Tightening the medical tubing that provided the power to pull the shaft to the hard stop

• Moving the hard stop and axle into the optimal position

• Figuring out how to calibrate the machine

• Securing the catapult to a piece of plywood so it wouldn’t move after every shot.

The design still needs a lot of improvements based on the power applied and the contact with the ball to make it into the boiler quickly and consistently.

Testing:

Intake

Today we took the intake prototype from yesterday and added several more surgical tubing belts in order to pull in more balls at once. In addition, we resized it for better geometry and added a CIM motor for lots of power. The results are very successful, and we are able to rapidly suck in several balls at once over a bumper, meeting our original goal for this prototype. The next step is to mount it on our practice drivebase and see how well it can intake once in a robot. We prototyped this specific intake because we have used similar ones in the past successfully, but were unsure how they would react to the plastic balls compared to more traditional foam balls.

Testing:

Drivebase

Today for the 2015 Deadlift drivebase we installed a new radio with updated 2017 firmware in order to successfully connect to the driver station. Additionally we experimented with different types of wheels. Initially we started with colson wheels on the outside and an omni-wheel for turning. The idea was that due to the center drop of the drivebase we would only be on an omni, and a colson wheel at all times. In order to optimize for turning we changed to all omni wheels, yet the turning was erratic so we think another set of wheels would be best for this game.

Gear Intake

Today we worked on the gear intake for the 2017 FRC Robot. The process involved spending a little bit of time on CAD to create a preliminary design, and then following up by actually laser cutting the wood pieces and then putting them all together. After that, we experimented with different heights for the grabber pieces on the claw to figure out which angle would be optimal in sliding up and over the edge of the gear. The next step in this project will be to cad a significantly more robust version of a similar design, as well as add a system for actually “grabbing on” to the gear so that we can manipulate it.

Testing:

Programming

A lot got done in programming today! We had our first build meeting and we will be having subsequent meetings every build where we will get anyone involved who wants to work on something. During this build we divided the work into the following tasks:

1. Installing updates onto drivers stations

2. Camera USB to RoboRIO Communication

3. Camera Calibration

4. Programming prototype boards

Driver Stations

We successfully updated the driver station software on the driver station computers. Now, everything works well.

Camera USB to RoboRIO Communication

Since last build, we successfully cross-compiled libpixyusb to the RoboRIO’s ARM architecture using QEMU on Ubuntu. We then created a JNI for it so that we can integrate it into our codebase. However, it has not been tested yet and we will be doing this throughout the week. If his port works, then we will not be using SPI with the Pixy Camera

Camera Calibration

The goal of calibration is to get rid of the distortion in the camera. Here are some screenshots that illustrate this distortion:

After the calibration, the dots in the image or more linear and the edges of the dot grids are parallel. This is the result of the calibration:

With better calibration, we will be able to more accurately approximate the angles of the goals so that we can make the targets. The calibration above isn’t perfect, but we are still working on making it better. The current issues that we have encountered are mostly due to the low resolution of the pixy camera which prevents OpenCV from recognizing the dots at more oblique capture angles. If it were higher resolution, it would generate a more accurate calibration.

Robot Programming

This build, we successfully configured the RoboRIOs and programming computers to use the latest version of FRC software, albeit with a few hiccups. In techno-speak, the RoboRIO wasn't assigning itself a static IP address, leading to communications problems. The programming subteam was able to overcome this issue, albeit with a temporary fix.