Day 42: Preparing for World Championships

Quick Summary

Everything that we need at competition, which includes the pit, was packed and prepared for being shipped to St. Louis.

Robot Progress

Shooter

We worked on some hood geometry and started to look at the placement of the hanger tube and different sizes. We also finished the design of the new hood and CNCed the new hood plates. We laser-cut a new center divider for the hood. Everything was assembled at on Monday’s build.

Hopper/Intake Ramp

The old hopper broke on the practice bot, so we laser cut new plates and assembled them onto the robot. We also cut spare hopper plates and spare intake ramps in case we need them during champs.

Driver Practice

We started practicing a new kind of gear cycle called the check mark cycle, which we plan will probably use from here on out.

Programming

Today, we worked on shooter tuning and semi-automated gear placement in teleop using an ultrasonic sensor.  For shooter tuning, we worked on fixing a problem where our stream will begin to walk backwards over long periods of time.  We believe this is a result of the system becoming more efficient over time as the bearings on our flywheel heat up.  To solve this problem, we tried compensating for the increased flywheel speed over time by taking an average speed of the flywheel between shots and using it to adjust our voltage..  For teleop gear placement, we tried to use the ultrasonic sensor to limit the amount the robot can drive backwards when scoring gears to prevent it from driving too far back and bending the spring.  However, we found that the ultrasonic sensor updates far too slowly for this to actually work right now, so we are investigating ways to speed up the ultrasonic sensor and use our drivebase encoders to compensate for this lag.

Day 41: Improving Gear Scoring

Gear Grabber

Today we worked on the Cow Catcher, or an assembly that prevents balls from getting stuck in the Gear Grabber and pushes balls out of the way. We began with prototyping with two delrin side plates and a 3/8" standoff, and while the results were promising, balls still got caught in the general vicinity, affecting its performance. To solve this issue, we prototyped the cow catcher with a longer standoff, which prevented balls from getting caught.

Having determined the relative effectiveness of the Gear Grabber, we began to design a deployment mechanism such that the cow catcher fits in the framer perimeter at the start of the match. We came up with the use of a torsion spring and hardstop to deploy the cow catcher at the start of the match. Due to the limited availability of springs at the lab, we used rubber bands instead, but the deployable cow catcher was ultimately too weak. Thus, we added standoffs and reinforcing plates to increase rigidity.

Robot Progress

We worked on fixing up our practice bot, making a new intake ramp and straightening out our hopper flanges. We also did a lot of shooter testing and were able to significantly improve the accuracy of our shots.

Day 40: Improvements for SVR

Driving Improvements

We added additions to our robot in order to create an easier and more efficient driving environment. We have placed a blue LED strip on the back of the hood to let drivers know whether or not they are in a good shooting proximity. To do so, we wired up MOSFETS to control the LED strip, which will plug into the DIO port on the roborio.

CamerasfAutono

At SFR, we found that installing “back-up cameras” would help with gear placement. Therefore, we worked on optimizing the camera placement, as well as finding a way to widen the narrow field of view (currently 70 degrees) to better capture the gear’s location.

Autonomous

After the post-mortem we worked to improve the robot's turning during autonomous. We prototyped small Delrin sliders that didn't quite work when sliding on carpet. We anticipate that the best solution will be to try to implement drop-down omni wheels that we can turn on. However, if that does not work either we will resort to changing the autonomous routine itself.

Days 37, 38, & 39: Preparing For Competition

Intake

Today, we worked on fixing the intake after it broke earlier this week. After analyzing the strength of our current weldment and modifying it slightly, we decided that simply strengthening it would not help the fundamental problems existing in the design. We took one of the broken intakes and attached it to new polycarb side plates hoping that this would decrease impact forces by increasing the time of impact (change in momentum = force * time). We drove around and crashed the intake several times with minimal damage occurring, and we are proceeding with the new design.

Hopper

Today, we worked on the Hopper and testing the fully assembled redesign. After fixing some initial discrepancies in the real life assembly, we tested out deployment and stowing. As of a few tests, the intake deployed well (after modifying the intake ramp slightly to have slightly deeper notches to fit the constraint screws in) and we will be updating the CAD with these changes on Friday. We will also laser cut a new intake ramp to get definitive results. If all systems work well after that, we will begin assembling the new parts for comp as well as a back up.

Between, Friday and Saturday, we were able to finalize the hopper design. After some CAD work on the redesign and some troubleshooting after assembly, we were able to make a solid hopper. More testing will continue to confirm consistency, but we will be moving forward with the Comp set soon.

Shooter Flywheel

In the last week, we explored the use of a large flywheel to help increase the consistency of the shooter. A flywheel dramatically increases the kinetic energy of the shooter wheel system, hopefully reducing the amount that the wheel slows between shots. We designed a steel flywheel with about 4 lb*in2 of inertia. It is geared up 2.5:1 from the shooter wheel to increase the kinetic energy. Preliminary testing shows that adding the flywheel may not actually achieve the desired result. The elasticity of the timing belt caused some controllability challenges that the programming team worked on this weekend. Each time the direction of tension in the belt switched (from energy going into the flywheel to energy leaving the flywheel), there was a little bit of elastic movement which added oscillations to the shooter wheel system. The plots looked like the typical mass/spring/damper plots for a 2nd order system from a controls or dynamics class.

Climber

We are using inline elastic to add stretch to the rope. This will allow the robot to pull the rope down with a low amount of force at first, getting some wrap before beginning to lift the robot off the ground. This is important because the Velcro that engages the climber drum is strong in shear – and its strength is proportional to surface area. Once the rope has wrapped around the drum enough, the load transfer switches to Capstan forces. We are assembling several ropes, each with a number of pockets like the ones shown below.

A video is linked below of the climber being tested. Note that in this test case, we were pulsing the motors. Typically, the climb is much faster.

https://youtu.be/UYMntdI0CPo

Gear Grabber

The latest iteration of the gear grabber has a dual pivot design – the whole mechanism pivots from a pickup configuration to a scoring configuration with one pivot, and a second lower pivot is sprung to allow the wedge to conform to the floor without digging in. We built this prototype last week out of delrin on the laser cutter and used it for driver practice over the weekend. We moved forward with making this out of metal and sent the parts to Anodize on Monday morning.

Check out the video below for pickup and scoring performance of the current prototype:

https://youtu.be/Oj6FkjkXHtM

Driver Practice

We practiced driving by cycling gears with and without defense, climbing, and intaking balls off the floor. We are much better now at quickly scoring gears, and in one practice match we scored 9 gears and climbed when no defense was played on us. The gear grabber is much more reliable, and consistently picks up gears off the ground the second we touch them. Scoring is still tricky, but we are getting better at finding the right depth at which we need to drive into the spring.

Programming

Autonomous Program

Today, we worked on finding and fixing a bug in our Adaptive Pure Pursuit controller.  The bug was causing arc lengths in the controller to be calculated incorrectly in some cases, resulting in a value much higher than it should have been.  This would in turn cause the robot to drive way too fast and shoot past the end point in the path.

Gear Grabber State Machine

Today, we worked on implementing a new Gear Grabber state machine. The new gear grabber code greatly simplifies the operator controls. Now, there are only 2 buttons used for intake and release. The state machine uses output current to determine when a gear has been picked up and will activate the piston automatically.

More Information

We also found two bugs resulting in the robot not turning left and twisting along an autonomous routine, and we were able to fix these edge cases.

The hardware team began crimping and attaching 15 battery leads and running battery tests to determine true battery capacity.

Day 36: Improving Subsystems

Hopper Floor

Today we ordered all the the parts for the upper extension of the hopper floor and got majority of the CAD done. We will be going with 50 degree edges made out of Delrin with the first two rollers of the upper extension not having any surgical tubing to allow for horizontal movement.

Feeder

Today we worked on inventorying all the COTS parts for the Feeder subsystem. This would allow us to become more organized and make sure parts we need we have or are buying. I also helped lead students in inventorying other subsystems via the CAD,

Gear Grabber

We worked on the gear grabber. We removed the polyurethane added before with black, conforming WCP wheels. We found them to work significantly better than the polyurethane, but still not extremely well. We continued to work and changed the WCP wheels to red conforming wheels, which while ugly, worked better.

Days 33, 34, & 35: Preparing for Competition

Gear Grabber/Driver Practice

We worked with the drivers over the weekend, doing basic drills like gear cycling, in order to become accustomed to driving the robot prior to the SFR Competition. We started the day by iterating on the floor for the gear grabber.  The floor pickup for gears still needs work as it is inconsistent at picking up the gears when we drive into them. The polycarbonate knife edge was not as smooth as the prototype. There was a small edge on the actual version which was causing problems, so we sharpened it. After iterating on it, we then mounted it, and set ourselves on solving the jackknifing. We realized the best solution for this would be to redesign it, so Andrew and Mani are working on a new CAD. Meanwhile, the group worked on iterating on the length of the polycarb. We still have work to do before we finalize the design.

Bumpers

The major problem we were trying to solve was that the bumpers were too low. This was because the mounting solution uses C-channel brackets that go around the bumper supports and are supposed to sit flush to the underside of the little 1/2 x 1/2 bumper rail.  But, what we didn’t realize is that the rail actually has a weld bead under it so the brackets could not go up high enough. This made the bumpers too low to the ground. To fix this, we removed a couple staples and pulled back just a bit of fabric on one of the practice bumpers so we could remove the brackets without actually remaking the entire bumper. We used the mill to make the brackets shorter, so they can move up and avoid the weld. We also used the drill press to add a new hole so they can align to the holes already drilled in the robot. This works pretty well, but some concerns are that the bumper is now too high and lifting the intake up, preventing it from going down far enough to have good compression on the balls. As of now, the intake is working fine. We still need to mill down all the other brackets, and we talked about making new ones and getting them anodized for the competition bumpers. The red comp bumper still needs fabric, and the blue one should have the fabric removed.

Hopper

Over this weekend, we worked on the hopper redesign. After some initial tests, we found that perhaps preventing the hopper from expanding sideways in the front expansion might add rigidity and strength to the hopper. To do this, we tested by bolting the front sliders to the hopper to prevent them from sliding. After testing, however, we found that intake by actuating the field hopper became difficult as the decreased width of the hopper prevented the balls from coming into the robot. To accommodate this, we redesigned the hopper in CAD so that the top will slide out vertically while the bottom pivots about a fixed point that torques the flexible polycarbonate. We also started the CAD of the new hopper floor for SFR which has the top rollers and wedges and a center to increase our ball throughput. We started the construction of the wedges on the hopper floor. After some brief testing, we CAD-ed this out. We will begin manufacturing on Monday.

Hanger Rope

This weekend, we received the 3/4” ratchet strap climbing ropes with the sewed on velcro. We tested it by pulling on it and rubbing it at corners in order to see distressing. The rope was then tested using the rope climber on the practice robot but the lack of stretch/slack made it hard to latch onto. In the near future, the rope team will attempt to plan out elastic placement on the rope.

LED Light

We wired up a MOSFET to control the switching of the LED light, located on the front of the robot, by having a voltage signal sent out from the relay port of the Roborio. It allows the drivers to see better when having to place a gear without the light blinding them.

Programming

Autonomous Program

Today, we worked on creating a reliable 40 kPA autonomous mode. We decided that previous autonomous modes that used complicated S curves to swerve into the hopper were too inconsistent, so we settled for a new, much simpler mode. But, at the end of the night, we had a working auto mode that deployed the intake, rammed into the hopper head on, waited a few seconds for balls to pour in, then aimed and fired the balls into the goal. We continued to improve the efficiency of this autonomous mode until we had it begin shooting around 6.3 seconds or less. We needed the autonomous mode to begin shooting as early as possible because there is around a 5 second delay between scoring a ball and having the scoring system pick it up. Because of this, any balls shot past 10 seconds will probably not be scored during auto.

We continued revising our robot's autonomous routines, and we were able to drive to the hopper and trigger it, receive a payload of balls, and fire into the boiler.

We also worked on a live data plotter that could plot robot data much faster than SmartDashboard. Various subsystems, such as the drivetrain, simply push data to a server, which pushes data to a grapher website on the driver station. This utility will be useful for tuning drivebase and shooter PID, as well as other programming tasks.

Day 32: Continued Assembly and Programming

Gear Grabber

Today, we worked on designing and testing the roller gear grabber. We installed a prototype onto the programming robot, and it worked somewhat well. When we drove into a gear directly, it was always ours, but it was narrow and difficult to always aim correctly at the gear. We played around with passive funneling, but were unable to significantly improve the width from which we can intake because of the sidewalls of the rollers were too low. Griffin and Colin are currently designing a new gear grabber that will likely funnel more effectively, and we plan to have it on the robot and testing it on Friday.

Hopper Floor

We took the top roller prototype that we have been working on, and added a center wall. The one from Monday was not long enough, so we extended it and stiffened it. We found this to help immensely. We also added zip ties across rollers to help the balls move across faster. We have reached a point where we are comfortable and confident with the floor.

CAD

We made progress on the hopper improvements in CAD and the redesigned Gear Grabber. We determined the geometry for the gear intake, designed the gearbox, and made the basic assembly that will be developed upon later.

Programming

Today, we worked on improving the web interface for the autonomous pathing tool.  We improved the overall aesthetic of the app, and added several new features. These include the ability to see robot start and end rotation, and having the path colored based on the current speed of the robot.

Day 31: Continued Assembly and Programming

Hopper

On Monday, we worked on making the hopper more rigid as well as tackling other issues with it, including breach of size constraints and inability to actuate field hopper. We brainstormed and tested off of current practice-bot hopper with small team to determine solutions. We plan to change the front extension components to prevent them from expanding sideways by making it one piece. We will also lower the hopper to fold over the intake to give it greater strength and rigidity. As a result, the hopper will fold have slightly less volume for ball storage, but much greater strength.

Rope Climber

The rope design has been prototyped. The length and placement of velcro on the rope as well as the knot have been measured. The rope has not been tested or sewn on with velcro yet. Next build, we will attempt to prototype elastic and the placement of elastic on the rope as well as the amount.

Hopper Floor

We constructed a new top roller for the hopper floor. We also made few wedges at different angles to see which angle was best in directing each ball towards the shooter. Once we find the ideal wedge angle, we tested it. It worked well during the first test, but it was not consistent. Next time, we should keep experimenting in order to find the proper wedge angle.

Programming

We continued testing a ball counter for the shooter, but we were not able to count balls fast enough with the shooter on full power. For the counter, we’re using a Sharp distance sensor and creating a threshold that returns true when a ball is within range of the sensor. It is likely that our voltage threshold for the ball counter is too wide, causing some balls to not be detected.

Day 29 & 30: Getting Ready for Competition Season

Assembly

Hopper/Hopper Floor

Today, we worked on solving the funneling speed issue by placing a set of 4 rollers at the end of the hopper floor and above the wedges to provide a force pushing the ball forwards. This worked extremely well as our output increased to around 10 balls per second. More work needs to be done with different wheels and friction surfaces on the rollers and wedges to further increase our output.

Programming

We worked on pneumatically actuating the gear grabber by activating the solenoids individually. We are going to work on a state machine for Monday to make it more intuitive for drivers. We also deployed a sine scaling function to the driver inputs to significantly improve robot driving. We tuned the path following program by fixing some bugs and also investigated using the talon magic motion profile. We also developed the state machine for the gear grabber.

Day 28: Bag and Tag Day

Robot Progress

General Assembly

Today, we started by receiving news that after visiting 3 anodizing places, we could get parts for our hopper and hanger anodized for the competition robot. After calling, we knew that we would receive parts by 4, so we had to get everything ready for that time. The first thing we did was find every screw, every tool, every part, needed to assemble those subassemblies the moment they arrived. We then, finished the side panels and assembled the hopper. As soon as the parts arrived, we built up the entire robot and cleaned it, the best we could. We proceeded to take robot photos, and then diagnose the robot.

We also spent majority of the day working on a battery tab mount to keep the battery leads away from the hopper floor. The battery tab mounts to the PDP and fastens the Andersons together.

We found the shooter to have some issues that need to be dealt with, but physically fixing them must be pushed off until SFR. The robot was bagged around 10 minutes before 9pm.

Hopper Assembly

Yesterday, we worked on assembling and attaching the hopper container. While we waited for the anodized parts for the hopper floor and climber to come in, a group of students worked on assembling the main components of the hopper while carefully avoiding smudging the sponsor side panels before pictures. After prepping everything and waiting for other subsystems to be assembled and attached, we riveted and bolted on the hopper in under 10 minutes to allow media time to take pictures and then carry out any final checks before bag and tag.

Programming

Today, we worked on tuning our autonomous program some more. We discovered that the bug from yesterday was caused by two segments of the path not lining up, causing the pure pursuit controller to go out of control as it attempted to move the robot to the correct position.  We managed to get a fully working autonomous mode that scored a gear, activated the hopper, then shot around 40 balls into the boiler.  We noticed some inconsistencies with the gear scoring segment of the auto, most likely caused by wheel slippage.  We didn't have enough time to fully resolve this issue, so we will continue to work on it this weekend.

Day 23: Continued Assembly Hopper Progress

Robot Progress

Almost all our parts are back from anodizing and we are trying to rapidly assemble as much of the robot as possible. The team working on putting surgical tubing over the rollers is almost finished and just needs to trim the excess off of each edge. The intake team finished assembling their first subsystem and is ready to mount it to the robot and assemble the rest. They had some trouble locating the appropriate timing belts, but now are ready to assemble. The shooter team also collected all their hardware. They just need to laser cut the rest of the polycarb and delrin plates, assemble the other shooters, and mount on the robot. Superstructure wiring was set back when we had to unfish the wires and drill additional holes in the weldment, and we are not back on track and ready to terminate the shooter wires. Late in the evening, a team of students and mentors stayed late to double check our inventory to ensure that we have ordered everything that we need to complete the robot by Tuesday. We are hoping to finish assembling intakes, shooters, and feeders today and at least one conveyor assembly as well. Wiring should be able to finish the practice and comp robot shooters and begin wiring the other subsystems.

Field Construction

Today we have finished all the feeders for the field by attaching the tops to the base. We have all the polycarb cut for the hoppers, but need people to cut the pipe that slides in and zip tie them on. The prototyping for the driver station to boiler mount is almost finished. The final idea has been decided and is going through final stages of being designed. The 2×2 wood for the boilers net have been cut, and all that is left is to place them on and attach the netting.

Programming

We decided to scrap the PixyCam system and use two separate camera systems, the Android phone, and a webcam connected to the RoboRIO. The Android phone system is the same system that we used last year but trained for this year’s boiler targets. We worked on getting the phone mount ready to mount on the robot. The webcam will be used for the gear placement; it connects to the RoboRIO via USB and serves live video to SmartDashboard via MJPEG. We were able to view a live stream of video on SmartDashboard, and we began work on identifying the boiler targets with the webcam’s stream on the RoboRIO.

We also worked some more on the Autonomous Pathing system.  First, we got the pathing system working with the new RobotState class, replacing the old Odometer class to keep track of robot position and heading.  We also added linear interpolation to the lookahead point of the last segment of the path.  This was in order to fix a problem where the robot would jerk sharply at the end of the path, causing its heading to end up out of place.  Finally, we worked on tuning the wheel radius so the RobotState class would give a more accurate position. After making these improvements to the pathing system, we worked on tuning PID for the drivebase using the built-in talon PID control. Tuning Kf went smoothly, but we ran into some problems with tuning Kp.  Even extremely small Kp values would cause the robot to turn wildly, and we weren't able to find out exactly what was causing this problem today.

Day 22: Finishing Up The Field

Robot Progress

Today was a productive manufacturing and assembly day even though we didn't have our anodized parts back. We took off the superstructure today to make holes to run wiring from the shooter and feeder motors and encoders from the top of the superstructure to the drivebase. We began fishing wires, but were not able to finish because we have to add more holes to the superstructure to mount the feeder roller plates. Tomorrow we should have several parts back from anodizing and we can begin to assemble several subsystems including the intake, superstructure, shooter, and feeder. Manufacturing will also continue on the hopper polycarb pieces.

Field Construction

Today we finished up all 6 of the feeder stations for the field. We also changed all the plastic from the previously used HDPE to the new official colored plastic, which allows gears and balls to slide down it much more easily. We plan to continue with field work, with the next tasks being to finish the more complex airships and assemble the field side walls/driver stations.

Programming

We made leaps and bounds towards cleaning up our Github codebase and making work far easier Previously, our codebase had sprawled across multiple branches, each with their own versions of essential robot code, which made collaboration difficult. We merged the latest autonomous and camera code into the master branch. In the future, we will ensure that all code remains within three commits of the Master branch, and we will pull far more frequently.

We also began integrating the code for the Nexus phone camera system, as well as the robot state machine, into our codebase. The Nexus vision system was used with great success last year but is far more complicated than our PixyCam system. We will test the PixyCam again, using the central point on the top segment instead of the centroid (a far more consistent, reliable means of estimating the distance), and the accuracy/reliability will determine whether we use the PixyCam or the Nexus phone.

The drivebase PID control was tuned for our unweighted robot drivebase to compensate for mechanical differences. Previously, we set a constant voltage to the motor to control the robot’s speed, called open-loop control. This does not take into account different mechanical differences, like gearbox lubrication or bits of carpet stuck in gearboxes (a problem we saw). Now, instead of swerving, the drivebase drives in a straight line!

Finally, we began work on integrating an infrared laser distance sensor into our robot code. The sensor turns on a high-power infrared laser beam and measures the time taken for the beam to reflect back to a detector, then uses that information to calculate the distance between the sensor and the object. This “time of flight” sensor has great accuracy, and we envision using it in conjunction with our camera system to accurately measure distances and aim appropriately.