Blog - 2018
Build Blog Day 7 (1/17/2018)
Drivebase
Task: Cartoon CAD
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Prior to today, we had the idea of having an intake feed into a tunnel. The tunnel would serve as a conveyor system to transport the cube back and forth across the robot. However, the issues with the tunnel are that a) it will be very bulky and would serve as a huge cantilevered load on the elevator and b) the vertical translation of a cube from the ground to the tunnel (~4.75") would be hard. To solve these issues, we had a new idea where we could have an intake that would pivot 180 degrees to pick up a cube in the front of the robot and then fold back to spit it out on the back side. Since the intake is now taking in and spitting out the cube, there is no need for a vertical translation of the cube and no need for a series of rollers to convey the cube back and forth across the tunnel we need to continue investigating the geometry of this new intake design and make a decision if we want to pursue this design or not by this weekend.
Bumpers
Task: Design a way of attaching the bumper to the drive frame rails
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We have been working on using latch pieces to latch the bumpers onto the bumper rails. During our next build, we will decide if this is the best way to go and finalize the bumper mounts on the drive frame rails.
Intake
Task: Complete designing the new intake prototype
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With our new intake prototype design, the intake is mounted on an arm and grips the cube. The arm that the intake is attached to has the ability to rotate back 180 degrees. We plan to have the arm and the intake system itself mounted onto the elevator. When the elevator moves up, the intake arm rotate back and ejects the cube onto the scale or switch. A few issues we are facing and trying to solve, are that we don’t want the intake to be too heavy and we want the intake to have a better grip on the cube.
Build Blog Day 6 (1/15/18)
Gearbox
Task: Design drivebase gearbox
- We found out today that the gearbox will have to be redesigned. Our original plan consisted of a triangle of mini-CIMs but this design was too tall and would not allow the tunnel to lay flat and exhaust cubes to the exchange. Our new design still uses 3 mini-CIMs but they are arranged flat so that they can be lower than the bumper rails.
Tunnel
Task: Design tunnel with timing belts to friction drive the cube across on all four sides
- For the tunnel, we worked on prototyping a mechanism that used timing belts to move the cube.. We made a four bar that allowed us to test the cube in both orientations (11 and 13 in width). Initially, we had trouble with the prototype as there was too much friction between the wood the cube rested on and not enough tension in the belt. We redesigned the prototype and made changes including making the four bar structure more secure, tensioning the timing belt, and installing plastic rails for the cube to slide on. These changes greatly increased the effectiveness of the prototype, and pushed the cube quickly through the tunnel. We now are designing a variation of this but using rollers instead of timing belts, to see which one works better.
Programming
Task: RPLIDAR Driver
- After ensuring that the RPLIDAR works, we discussed several options, and have started to implement two of them. For our first method, we were able to use existing examples of code, from the RPLIDAR’s Software Development Kit (SDK), and write our own program that gets data and a timestamp for that data from the RPLIDAR, and send that data to the robot. Because the SDK is for C++, we would probably have to run this program on a co-processor on the roboRIO that communicates with the rest of the robot code over User Datagram Protocol (UDP). Our other option, which is more preferable, is to use the Java Native Interface (JNI). JNI allows the Java Virtual Machine, which runs Java code, to call functions written in other languages, which will allow us to use the SDK, even though it is written in C++. We will continue work on both of these methods, and choose whichever will work better for the robot.
Task: RPLIDAR Visualizer
- We scaled down points to the size of the field, but this messed with the zooming and panning functions so we’ll have to fix this. Here is a sample image of the current functionality of this interface:
Build Blog Day 5 (1/13/18)
Drivebase
Task: Model drivebase moving up platform ramp with 1/8" center drop and minimal space from outside bumper supports
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To ensure we have a stable robot when our CG raises with our elevator, we decided to extend our wheelbase as far out as possible. By doing so though, we are more susceptible to high centering on the platform ramp. To ensure we do not do so, we revisited the sketch we used to model the drivebase motion and adjusted the parameters to space the wheels as far out as possible and with a center drop. We also decided to constrain the lowest height of the bearing holes by having the center 16 tooth sprocket with chain OD be tangent to the baseplate. We will account for the chain run by having a cutout in our base plate.
Task: Finalize drive gearbox
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We finalized the design of the drive gearbox and placed an order for the necessary hardware required (gears, pneumatics, screws, etc.) We hope to begin assembly of the drive gearbox this week.
Task: Sketch electronic placement
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Task: Sketch electronic placement
We sketched the electronics placement on the baseplate. We plan on having the battery lay flat as in 2017 rather than standing up as in our 2016 robot. This way, we can lower the carriage/tunnel as far down as possible which means the cube does not need to move vertically as much from the ground to the handling mechanism.
Intake
Task: Prototype Intake
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We assembled an intake with adjustable wheel placement and pivotable arms/outer wheels, and mounted it to the 2017 drivebase. We controlled each wheel with its own independent 775pro geared with a 5:1 reduction —- by doing so, we were able to test asymmetry and easily adjust certain speeds of certain wheels. This intake prototype worked well in quickly drawing in the cube and orienting it from a diamond to a square shape. We also saw that by increasing the pressure in the pistons controlling the outer arm pivot, the intake itself became a lot stiffer and was able to better control the cube. We quickly implemented a bottom kicker roller and saw that it worked well because the intake itself was able to provide enough force to push the cube up and above the kicker roller. Moving forward, we will design a prototype that combines this intake with a kicker roller and mount it on a test drivebase.
Task: Prototype ramp intake
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We design and tested if a kicker roller + a ramp with wheels on either side guiding the cube up would work in transitioning the cube from the ground to the tunnel. While testing, we realized that the wheels on either side did not grip well to the cube (we used colsons) and the transition from the kicker roller to the ramp and wheels was not as straightforward as expected. When the cube goes over the kicker roller, its motion is not very controllable especially when that is the only roller it is contacting. We added a vertical constraint (a piece of 2×4) to stop the cube from being kicked too high, however it deflected the cube from the center of the intake and away from the ramp. Watch this video to see the prototype in action.
Miscellaneous CAD
Task: Cartoon CAD and system integration of robot
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Today was mostly filled with discussion regarding how best to integrate the various systems of the robot and how to constraint the placement of those systems. In terms of the elevator, we will be moving the outer bars (2×1 box tubing) to sit on top of the frame rails. The outside face of the intermediate stage will come in 0.138" (same clearance used in 2011) from the inside face of the outer bars, and then the carriage tunnel will be another 0.138" in from the inside face of the intermediate stage. This leaves us with around 17" for the width of the tunnel which we think will be enough to handle any orientation of the cube. We also investigated the elevator placement with regards to climbing. To make climbing especially easy on the drivers, we plan on driving straight up onto the ramp and having our bumpers flush against the scale wall and our elevator bar flush against the 2×2 box hanger box tubing. With those constraints, this means our elevator sits 8" from the outside face of our bumper which also means that given we want to spit cubes out on the back side of the tunnel (the side opposite the intake), we need to spit them 8"+. 8"+ is not ideal especially if we want to strategically place a cube, so we need to further investigate how best to optimize elevator placement. We also did line contact calculations on the bearings contacting the intermediate stage from the outside bar, and given that we are hanging 3 robots, then the bearings as well as the aluminum tubing will endure more load than their static load capacity and yield strength, respectively, can handle, To solve this, we tossed around ideas of alleviating a portion of the load from the bearings with a tensile member extending from the top of the intermediate stage to the CG of our robot (the tension of the cable acts opposite to the torque of the robots). Lastly, we decided that to ensure we have a smooth transition from the intake to the tunnel, we will have the intake fixed to the tunnel and not pivot, but will have the entire tunnel + intake system pivot such that it can stow within the frame perimeter, intake horizontally, and place cubes on stacks on the scale.
Programming
Task: RPLIDAR Driver
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We tested the driver that was already written, but nothing happened. After rewriting some of the code, we were able to send a request to the RPLidar and received some sort of "ok" response, but still, the RPLidar did not start scanning.
Task: RPLIDAR Data Visualizer
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We worked on some more modifications to the visualizer. We were able to cache all the data sent to the visualizer in an array, so that we could view data with specific timestamps. We also worked on being able to zoom in and pan around the image of the field, so that it is easier to see, but there are still some bugs with this.
Task: Intake Prototype
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For testing purposes, we remapped the control board so we could toggle each of the four motors on the intake prototype with four separate buttons on the driver station. We also added some buttons to change the speed of the motors on the intake. In addition, we read the drive code, but since last year's programming bot did not have a working compressor for the dog shifters on the drivebase, the robot could not drive.
Build Blog Day 4 (1/12/18)
Drivebase
Task: Test different wheel arrangements between colsons and omnis
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We decided to switch our initial idea of using 6 colsons to 2 colsons and 4 omnis on the drivebase. We also decreased the drivebase width by 0.6 inches to accommodate for the entire width of the colsons. In addition, we added custom wheel shafts into the Drivebase CAD. We also added the gearboxes into the drivebase CAD. This will require us to change the placement of the electronic components.
Gearbox
Task: Design drivebase gearbox
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We started by resolving a few minor issues with packaging Cims around the shifter cylinder. We also realized that we needed more space for components in our gearbox, so we decided to increase the size of the gears between the Cims to fit all necessary components. After fixing these issues, we now have a working gearbox design. At our next build, we plan to finalize the assembly and detail the Gearbox CAD.
Intake
Task: Design intake prototype with two horizontal rollers to pull in and kick up cube
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We began build by testing the 1st simbotics style intake prototype with 2 sets of wheels. After our testing, our results confirmed that asymmetry is the best way to go forward. Next, we assembled a new intake prototype with a horizontal roller and a kicker roller placed slightly behind the horizontal roller. When testing this prototype, we noticed that the cube would be lifted off the ground and get stuck between the rollers. We plan to keep testing this prototype since the kicker roller showed some promise in getting the cube over the frame rail. Look at Video 1 and Video 2 to see this new intake prototype in action.
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Lastly, we laser cut version 2 of the simbotics intake, which will be assembled during our next build.
Tunnel
Task: Design tunnel with timing belts to drive the cube across on all four sides
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The original plan for the tunnel was to have a square tunnel 13”x13” that would have power belts on each side. This way, no matter the orientation of the cube, it would always be in contact with at least 3 sides.
Programming
Task: Test the lidar driver with the roboRIO
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We worked on the driver, which helps us get data from the RP LIDAR sensor. The sensor gives the distance in mm and the angle in degrees of a detected object.
Task: Hook up the visualizer to the robot
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We also worked on the visualizer by plotting dummy points on a picture of the field. We encountered a few bugs, but fixed them all. Look below for a picture of the visualizer.
Task: Setup and testing
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Limelight is a camera specifically made for FRC, which makes it easier to use, so we have been experimenting with it. We tuned the vision pipeline specifically for the power cube. In this process, we realized that we had to re-tune the vision pipeline in different lightings, so at each competition we would have to re-tune the pipeline if we were to use the Limelight. The Vision Pipeline is a set of consecutive image processing functions that work to isolate and find specific objects.
Build Blog Days 2 and 3 (1/8/18 – 1/10/18)
Drivebase
Task: Test drivebase with modelled dimensions (28"x33") 1.15” center drop; from top of frame rail and placed 2.5” from the front and back of the drivebase frame high centering on the ramp at various angles.
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When approaching the ramp perpendicularly, the robot clears the ramp and does not high center. However, when it approaches at angle towards the corner of the platform where the front and side ramps meet, it high centers. Also, when the robot is travelling up the ramp with the cable protector below it, The back of the drivebase frame contacts the cable protector and high centers on it. The drivebase modelled with these dimensions in CAD accounts for a 16 tooth sprocket with chain OD and a 0.1" clearance between the sprocket-chain OD and the baseplate. In addition, the 4" colson wheels used are actually 3.9" wheels. If we were to bring the sprocket lower to the baseplate and use fully 4" wheels, there is a possibility it would not high center. We need to investigate the lowest we can go with the sprocket-chain OD and test with new 4" wheels. Additionally, these results may change our driving strategy where we will only attempt to go up the ramp perpendicularly. See these videos to see the drivebase in action.
Task: CAD drivebase weldment and begin work on drivebase assembly
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We designed the drivebase frame rails such that the wheel placement and center drop can be easily modified as they are yet to be finalized. We went with our traditional West Coast Drive using 4” colson wheels. Assuming we will want to carry our partners while climbing, we need to beef up our drivebase, whether it be using thicker box tubing or by adding cross members. We will perform a bending calculation on different sizes of box tubing to determine what is the best size to use. Regarding bumper mounts, we currently see to ways to approach the task. The first way is a 2014 style bumper mount with latches on the drivebase frame that latch onto mounts on the bumper. The second way is a 2017 style bumper mount that uses guiding rods that go into the drivebase frame and some other latching system. The 2017 is definitely a harder bumper mount to work with, however, the straight face with mounting provisions may prove useful if we decide to deploy ramps for our partners to climb up on. We will investigate this in a cartoon CAD.
Task: Drivetrain gearbox design
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We decided on a triangular configuration of mini-CIMS, with ratios that yield about 10ft/s and 18.6 ft/s. We are now trying to figure out how to package the shifter cylinder into the gearbox below the CIMs. We are exploring either a smaller bore cylinder or a nose-mount piston instead of pancake. Changing from 3/4 to 9/16 bore reduces the shifting force from 22lb to 11lb; Further testing is needed to see if this is enough force to shift. Regular air cylinders can be used if it is ok that they stick out longer than the CIMs. The next steps are to finalize which shifter cylinder we want to use, model the rest of the gearbox plate, and then detail in the entire gearbox assembly with Cheesy Parts.
Intake
Task: Test intake prototype with pivotable arm
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We assembled the intake prototype and mounted it to the 2015 drivebase to test. We were able to run a few tests with a single set of wheels, but unfortunately, as the intake was made out of 0.25" plywood, a part of the arm broke off and we were unable to gather any further data.
Task: Test 2015 Simbotics style intake prototype with pivot wheel sets
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We initially based the intake prototype off of 2015 Simbotics’; with the first set of wheels pivotable but not the second set–we spaced out the second set to be tangent to the cube when it is 13" width. When intaking a cube in a square position, the intake easily worked, however, when intaking a cube in a diamond position, the cube got trapped between the first set of wheels which were able to pivot to comply to the cube's shape and second set of wheels which were stationary. To fix this, we made the second set also pivotable and were able to intake a cube at different angles. We hooked up the motors on the intake to the drive talons on the development board and were able to simulate different speeds for different sides by turning with the control board joysticks. With different speeds, we were able to force the cube to rotate into a square position in a certain direction which shows that some amount of asymmetry may be necessary to intake cubes. We will continue testing this intake on the field carpet to account for the friction between the cube and field and will further design this in CAD into a stronger prototype.
Programming
Task: RPILIDAR Driver
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We finished up writing the driver and implementing all necessary methods. The driver is ready to be tested once the LIDAR sensor arrives.
Task: LIDAR Visualizer
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We continued work on the LIDAR visualizer. We set up a Node JS server that recieves LIDAR point data encoded in JSON from the roboRIO using Network Tables. The server then uses websockets to send this information over to the viewing page. We also continued work on the visualizer interface. It can now plot fake JSON data, but needs to be hooked up the the websocket so it can display a continuous stream of data from the LIDAR sensor.
FRC Build Blog Day 1 (1/6/2018)
Here is the 2018 game animation.
Game Analysis
This year’s game involved many variables, requiring a strategy that succeeded in performing all tasks presented in the challenge. With the power ups, scoring based on points/sec, randomized sides, and the difficulty of climbing, no straightforward strategy which ensures a win presents itself. After trying various combinations of scores, we concluded the best way to maximize our points would be during autonomous when the scoring is scaled by a factor of 2 and during the endgame when each climb is worth 30 points. Since autonomous scoring is worth more than tele-op scoring, we decided that autonomous scoring was a major priority to stay ahead during a match. We planned for short paths to score cubes (<30 ft), so drivetrain acceleration and our ability to score from either side of the robot was critical for rapid cycles. We debated between starting off on the middle or side of the field. If we were to start off on the middle, we would have an equally distant route to reach the switch and scale. However, we could not guarantee the successful completion of our autonomous route as our alliance partners may get in our way. If we were to start on the side, we may either have a very long or a very short route to reach the switch and scale. However, we could guarantee the successful completion of our autonomous route as our alliance partners would not get in our way. During the endgame, we aimed for having all 3 robots climb or by having 2 robots climb and 1 levitate.
Drivebase
Task: Fix 2015 drivebase and prototype if it can go over the platform ramp
- We fixed the 2015 drivebase which was missing a control system. We mounted our development board on the drivebase and programmed it to drive, but immediately saw issues as it went up the ramp. Because of the long wheel base and short distance between the wheels and the ground, the drivebase high centered on the ramp when the bellypan came into contact with it. This result shows that for our 2018 drivebase, we will need a shorter wheelbase and a greater centerdrop.
Task: Model drivebase motion up the platform ramp
- We modelled in CAD the motion of a possible 2018 drivebase going over the platform ramp without high centering. We tweaked two factors (distance of outer wheels from side edge of frame rail, center drop) until we arrived with the dimensions of a drivebase that would safely clear the ramp with 4 wheels (2 on each side) always contacting it and without the bumpers or bellypan ever contacting it.
Intake
Task: Fix 2015 intake and prototype if it can intake Power Cubes
- We fixed the 2015 intake which was initially missing the intake wheels, shafts, and timing belts. We used this intake to prototype the intaking of the Power Cubes. We did see some promise with this intake, however since it was designed for the tote and not the Power Cube dimensions, we were not able to efficiently intake the Power Cube. Moving forward, we plan on testing out different wheel materials to contact the Power Cube as it is being intaked and will design/prototype an intake with the correct geometry to fit the width of the Power Cube.
Field Prototyping
Task: Test coefficient of friction of Power Cube on scale plate
- We wanted to calculate the coefficient of kinetic friction between the Textured HDPE and the fabric of the Power Cubes. To do this we looked at how high we had to lift the straight piece of HDPE before the Power Cube started to slide down. From this we calculated the angle formed and the coefficient of kinetic friction which ended up averaging to about 10.32 degrees and 0.18, respectively.
Task: Test geometry of 3 robots on the platform
- We laid out the spacing of three robots on the scale platform to see if it was physically feasible of having 3 robots side by side with enough space for the robots to maneuver to those locations. It seems that it is possible for 3 robots to fit on the platform.
Task: Find what angle does the scale tilt to at its highest state
- At its highest state, the scale tilts to around an angle of 7.662 degrees. Based on our data gathered from the task: “Test coefficient of friction of Power Cube on scale plate”, the Power Cubes will not slide down the scale plate when it is tilted to its highest state.
Field Construction
Task: Assemble wooden scale
- We assembled a wooden version of the scale, however we are planning on assembling an aluminum version similar to the scale we will see in competition. This is because we don’t want any differences from the tournament scale from different materials that will arise in different materials (center of mass, weight, friction) which may impact our robot performance and drive our robot design.
CAD
Task: Space claim of 3 robots on the scale platform
- In CAD, we made a space claim of 3 robots, placed them in various arrangements on the scale platform, and looked at the feasibility of having all 3 side by side. It seems that it is possible for 3 robots to fit on the platform.
Programming
Task: Program 2015 drivebase to steer in correct direction with controller joysticks
- When we initially placed the development board control system on the 2015 robot and attempted to drive it, the wheels were turning in the opposite direction to the controller joysticks. We corrected this by reprogramming the drivebase to match with the direction of the controller joysticks.
