Ringslinger 9000 OverviewTags: design, innovate, think, and mechanical
Task: Describe the construction and development of the flywheel ring shooter
The launcher of any robot is a central part of the design, just like the intake which is why we developed the two systems separately in order to achieve the best design for both. We also used our knowledge of shooting systems and previous prototypes to develop a mechanism that is both reliable and accurate. This post will detail the function and overall process of building the Flywheel shooter and its parts. It is not a post outlining specifics, the specifics of each set of parts are outlined in their respective posts.
The overview starts with a mechanical build breakdown. The best way to look at the design of the shooter is in levels. From top to bottom, there are the mounting, driving, and ring levels. The lowest level is where the mounting hardware sitsThis is where the shooter attached to the arm which sits on a pivot in the far back of the robot which changes angle depending on where the ring needs to be shot. The second level is the driving level where the motor, pulleys, and timing belts sit. Currently, the motor that is mounted is a 3:1 REV UltraPlanetary motor that can spin its sprocket at 1,727 RPM which drives the wheel in the ring level at a 1:1 ratio by another sprocket driven by the belt between the two sprockets. The last and final level is the ring level which is where the ring is actually gaining momentum to travel through the air. The rings are loaded into the holding area where they are pushed by a servo-driven arm into the wheel that both speeds up the ring and starts it turning as it travels down the barrel. After traveling the curved section, it reaches a straight portion where the ring is allowed to travel forward to help adjust its path to the target, ensuring a more accurate system. And that’s it. It’s a very basic construction. Boiled down to the simplest form, all that is happening is a wheel is spinning and accelerating a ring to get it to fly. The rest is just parts that are added to make it actually move.
Creating the shooter in real life is also quite complicated. Due to the pandemic, we are doing a lot more design in fusion 360 which allows us to take a more custom approach to building systems. The majority of the launcher is custom with 9 3D printed parts and 6 CNCed parts. Each one was specially designed to serve its purpose. The majority of the 3D printed parts are the spacers that separate the 3 CNCed plates, housing each level. There is also a custom spacer for the motor, NinjaFlex center for the flywheel, and push rod for rings which are all custom designed and 3D printed. The CNCed parts also include the plates on the top and bottom of the flywheel and the slide mount for the motor. The CNCed parts should have a post detailing the CNC process and there should also be a modeling breakdown for the spacers and other 3D printed parts.
Testing and Calculations:
The last thing that should be spoken at least briefly of is testing and flight prediction. The overall goal is to be able to pick up rings and automatically know where to point the barrel and with how much speed to launch a ring to automatically score it. We want to be able to let vision keep the barrel on target the whole time so we can quickly cycle rings. To do this we need to both have an accurate system and know where the rings will land depending on the situation. Making an accurate system is accomplished by rigorous testing to see how closely clustered a set of consecutively fired rings hit a target. We do this by setting the robot a fair distance from a foam board and monitor where the rings it launches hit and then show how close the shots are. The closer the better. We conducted our first round of tests a few days ago with ok results. A photo of the results is above. We are hoping to do better than this in the future so improvements need to be made. We also need to be able to calculate where the rings will land and are doing this with projectile and ballistics physics calculations which can be replicated in the code to target the shooter. More on that in posts that cover it.
We are working right now on dialing in the shooter to make it more consistent and also testing a 1:1 motor to see how it compares to the 1:3 motor in terms of accuracy. We are also being posed with a challenge unlike any other challenge we have faced this season which is taking what we made when we were developing intakes and making a system that can feed into the shooter. This is going to prove a challenge because of the size of the shooter and the fact that it can be rotated or tilted to any angle. The challenge may be large but we are a worthy opponent.