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FIRST robots are evolving into smarter, lighter, faster, and more-complex machines.
FRC team 4068 “Bearbotics” addressed these trends through the development and adoption of multiple strategies which allow low- to medium-resource teams to compete with intelligent robot design. Many of these techniques can be of benefit to the highest-performing teams as well. These solutions help teams save time and money while building advanced robots. These innovations helped our 2019 project save almost $2,000 and an estimated week of build time, while producing our highest-performing robot ever. We are promoting and sharing these methods to help the local and global FRC community continue the legacy of innovation and advance intelligent robot control at a low cost.
Software Defined Robotics
- Sensor-Based Control: we believe that “smarter” robots are faster and more reliable at game play – and therefore more competitive. Therefore, we have switched to a full-sensor mode of robot control, even when the drivers are controlling the robot. Most major robot operations such as speed, robot arm movements, manipulator height, and angle of attack, use sensor-feedback control directly; i.e., the robot doesn’t work without the sensor. This allows us to attain greater speed, accuracy, and repeatability, and gives us a direct path to automation many critical robot actions. However, it requires the sensors and control code to be reliable, which we’ve addressed by other measures described here.
- Navigation and Path Control: we have built numerous automated routines that enable the robot to quickly and accurately align with scoring target locations on the field. We call this “partial auto” because the drivers can command the robot to execute these complex routines at any time during the match, and repeatedly, as needed.
Custom Electronics and sensors
- BearCoders: there's lots of information and text already available about this. These save us over $500 per robot, with even more future potential.
- BearCAN: self designed and assembled. Allow us to connect, disconnect, and inspect the CAN bus that controls our robot. Saves us about $100 per robot. Can be assembled for less than $5 each.
- Compact vision camera light bar: custom designed and built for less than $5. Conveniently runs fully on a RoboRio DIO port and the brightness is fully controllable.
- Custom alternate power circuit for vision camera: allows us to power the JeVois camera from primary robot power outside the RoboRio, while maintaining the data connection to the RoboRio. No secondary battery required!
- Sensor Status Indicators: since the robot depends completely on sensors for most operations, we need to know that the sensors are connected and ready before each match. Most of our sensors have status indicators on them to indicate they are connected to the RoboRio controller.
Digital Design and Fabrication to Change the Game
while the parts from FRC suppliers keep improving, teams must be able to custom-design and fabricate some robot components and assemblies for performance differentiation. We propose and demonstrate methods that only require an inexpensive desktop 3D printer and digital CNC router.
- 3D-printed assembly components: one of our 2019 project goals was to 3D design and print as many parts of the robot as we could, to demonstrate the practicality and versatility of this fabrication method. This reduced the time and difficulty of robot machining and assembly, and gives us ready solutions to future parts-mounting challenges. In addition, we developed a simple cheap method of reinforcing 3D-printed parts so they could withstand higher amounts of mechanical impact and shock.
- 3D-printed sensor components: several of our critical control sensors use mounts, mechanical connectors, and gears that are 3D printed. Part of this is for flexibility and ease of fabrication, but we are also using this year’s robot to demonstrate the feasibility and versatility of 3D printed parts to the FRC community.
- 3D-printed sensor mounts: a lot of adapters are required to mount all the different kinds of sensors we use. All of these adapters are 3D printed, and they are readily adaptable to almost any part of the robot. Want to put it there – yes you can!
- Machine assembly gussets: one of our biggest challenges in 2019 was suppliers not having important parts available at critical times. When these shortages limited availability of important gussets, we built our own on the CNC router. Our 2019 manipulator uses these gussets almost exclusively.
- Fabricate our own custom-designed assemblies: while pre-build CAD design of the full robot is still an advanced skill, custom design of robot assemblies is within the reach of most teams. We custom designed 2 critical assemblies that differentiate the performance of our 2019 robot (the manipulator “wrist” axis driver, and the elevator lift carriage) and fabricated the key structural parts on a CNC router.
Precision Robotics is a set of methods to build robots more accurately and with more reliability so they can be lighter while more-powerful and -complex.
- Drilling Templates: we prefer to use the VEXPro VersaFrame parts set, which provide a lot of flexibility but demand sub millimeter machining accuracy to attain required alignments and strength. To achieve this we developed 3D-printable drilling templates for a wide variety of VEXPro parts to ensure attachment and pass through holes are precisely positioned and aligned. These provide such accuracy that we’re able to use the option of bearings set in the frames extensively, for a stronger robot.
- BearHugs: the reinforcement method we use for our largest most-critical connections.
- Reliable Connection Protocol: the goal is zero defects during competition. All electrical connectors are soldered, unless they are in a known-good reliable COTS part. All electrical connectors are double-checked for integrity, strength, and loose ends (that might cause shorts). All connections are mechanically tested, reinforced (see BearHugs), and identified.
- Standardized Parts: reduce the set of connectors and fasteners to the smallest possible set, and keep those parts organized and available. Also to reduce the requirement for tools (95% of the mechanical work on our robot can be done with a Phillips screwdriver and adjustable wrench). Ensures the right part is used for the job.
- Methods to achieve alignment precision with less machining precision: building on the VEXPro design philosophy that started this approach, we’ve designed and built our own gussets and bearing mounts that allow some variance in accuracy and reduce cost and time. We are testing these in our 2019 test robot, and will share further when we have verified long-term wearability and utility.