For our horizontal extension and the original vertical lift seen in our league meet videos, we are using Rev Robotics 15mm extrusion with the v2 linear slide kit. It’s tricky to get REV extrusions to slide smoothly so we have a couple tricks that help with that by allowing the screws to be looser yet not slip out of place. Our new vertical extension uses Long Robotics ball bearing slides with our own 3d printed slide inserts.
In the original lift seen in our league meet videos, we have two 40:1 motors chained together. The slides are three stages strung in cascading style which triples the amount of force required. Pulling up the lift with a kitchen scale and multiplying the maximum weight by 3 gets an approximate value. Using this and the stall torque of the motors gives you a general starting point for calculation of spool size. Our new lift uses a combination of two 3.7:1 motors and continuous stringing. Instead of REV slides, we’re using Long Robotics ball bearing slides. Again, estimating the weight/friction using a scale, the right spool size is calculated given the torque of the 3.7:1 motors.
We are using direct drive Andymark 20:1 orbital motors. These offer a fast and smooth driving experience and because they are direct drive it eliminates multiple points of failure such as chains and set screws.
We are using a gripper that holds the “nub” and the end of the stone. It can rotate 90° or 180° to orient the stone the way we want on the foundation.
One reason the robot is so controlled is many of the scoring functions, such as lifting and servo rotation, are automated to go to the correct height and orientation with a single button press. Driving speed is achieved by lots of practice. For tele-op, the mecanum code is pretty standard code which combines left stick as robot direction and right stick turning.
Vuforia takes a picture with the phone in the view of the first three stones. We then take that image and turn it into a bitmap (so we can scan color from it). The image is then cropped so most of the image is filled with the 3 stones. It is compressed so that the next step of scanning the pixel colors is faster. The program then counts the rgb color of 3 columns of pixels where it thinks the center of the 3 stones is. Which ever stone’s column has the lowest rgb value is the skystone (Because yellow has a high rgb value and black has like no rgb value).
We can currently stack 12 stones tall plus the capstone. With our REV lift, we were only able to stack 9 plus the capstone.
Our new horizontal extension is another Rev Robotics 15mm extrusion linear slide and is driven by a regular servo, 40:15 gearing and a 3″ spool. The old extension seen in our league meet videos used a Vex 393 motor with an encoder attached for positional feedback.