108’s 2007 Robot Revealed!
Here is a video of our robot scoring in autonomous mode: http://www.youtube.com/watch?v=b0plubOXnU8
Looks great guys. What type of feedback are you using to drive to the proper position?
We are using two different feedback techniques.
For the linear “joint” (which is not used in the video) there are three stationary reed switches which detect when a magnet (located on the moving telescope section) are within a few millimeters proximity. Using a state machine, controlled motor direction, we infer 5 states of the telescoping arm position bottom, middle, top, and two states for any area between those two intervals. We can then find out where we currently are, and using another state machine, control the motor accordingly to become where we want to be.
The two rotational joints both have banebot encoders. We can infer relative angular position from starting positions (these will eventually be zeroed with limit switched). We implement a simple proportional feedback control. This is especially needed for the last joint (the wrist is what I think we agreed on calling it) because it moves extremely fast.
We saw no need to implement a full PID routine for these joints. We also felt no need to implement any form of mathematical control for the elevator due to the fact that it pretty much stops within very few milliseconds of commanding it to stop.
Sounds cool for controlling the arm postion. How about driving to the proper position?
We are relying solely on information from the camera. We do have encoders installed, but currently do not implement them since dead reckoning is not viable this year for the rack moves at every match.
We set positive velocities of both wheels until the tilt angle reaches a certain value and we offset that on both wheels for the pan angle. The result is that the robot drives toward the light while driving forward. We created a raw drive function that does basically the same thing as the one joystick arcade control found in the default code.
will the arm go any quicker, was it that speed because of testing purposes? it seemed a bit slow…but maybe its just me. either way congrats on a successful autonomous and good luck at your regionals
looks good, glad to see you guys finally got it working.
Thanks
The arm goes that fast because it is powered by a globe motor with a 30:1 worm gear reduction. We couldn’t use a larger motor or a chain and sprocket system because the entire transmission needed to fit into a very small space (it fits into a 3"x3.25"x3.5" box). If it were any larger we would lose telescoping height to fit the extra size in the 4 foot height. Alas, the telescoping part (not used in the video) is very fast, so with that and the arm, we can reach the top level in about 5 seconds.
-Evan
awsome job guys…looking good
Looking really good guys. Looks like you are bouncing back and are going to be a force again this year. Can’t wait to see your team in 2 weeks!
I have to agree with Barry’s post above this robot looks much better then the last couple of years robots. Evan the way you described your worm gear drive for the arm it sounds alot like the 04 setup on 108. One final thing what are you using to drive that beast of a chasis? Looking great can’t wait for Florida regional.
-Drew
Very, very nicely executed. I hope we see a lot of this during the competitions!
-dave
.
One final thing what are you using to drive that beast of a chasis?
We are using the evil Banebots transmission from the kit with the adapter and 4 CIMs and 6 IFI wheels.
-No L