Big Wheel Articulations

Tags: Think, Innovate, Control, mechanical, and software
Personhours: 24
Big Wheel Articulations By Abhi

Task: Summary of all Big Wheel movements

The two main subsystems for our robot this year are the Superman arm and the elbows. Because all of our robot relies on these two to work together well, we paired them together in our Pose class and created a set of methods to articulate the subsystems. The presets were created by using manual control to find our encoder values and creating a set of state machines to move them.

The reason why each articulation is necessary and complicated is that we have to manage our center of gravity. When moving our arm, the center of gravity moves with it since the lift is so heavy. When transitioning from intake to deposit, we cant go directly because our robot will tip over so we have to go to safe drive then deposit. We are still managing this constantly with driver control but we hope to fix this easily with distance sensors in future.

The position seen above is called "safe drive". During normal match play, our drivers can go to this position to navigate the field quickly and with the arm out of the way.

When the driver control period starts, we normally navigate to the crater then enter the intake position shown above. From this position, we can safely pick up minerals from the crater.

From the intake position, the robot goes to safe drive to fix the weight balance then goes to the deposit position shown above. The arm can still extend upwards above the lander and our automatic sorter can place the minerals appropriately.

During the end game, we enter a latchable position where our hook can easily slide into the latch. After hooked on, our robot can slightly lift itself off the ground to hook.

At the beginning of the match, we can completely close the arm and superman to fit in sizing cube and latch on the lander.

As you can see, there is a lot of articulations that need to work together during the course of the match. By putting this info in a state machine, we can easily toggle between articulations. Refer to our code snippets for more details.

Next Steps

At this point, we have 4 cycles in 1 minute 30 seconds. By adding some upgrades to the articulations using our new distance sensors, we hope to speed this up even more.

Date | February 20, 2019