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 1) Field reset will want to do mean things to you. They have to remove the tubes. - EricH [more] |
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From our lead programmer...
This year, we have an interesting control system for our robot featuring a scale model of the robot and its arm. To operate the robot's arm, all you have to do is move the scale model to the position you want, then flip the on/off switch to open/close the gripper.
Potentiometers determine what the position of the model is, and determine that of the robot's arm. The control board has 3 potentiometers - one at the base of the arm (think shoulder), one where the boom connects to the stick (think elbow), and one at the wrist. These potentiometers are wired into the Cypress First Touch I/O module, which can connect to the driver station via USB. The values from this module can be read using the EnhancedIO parts of the WPI libraries for FRC. The potentiometers on the robot are in similar positions, and are wired straight to the Jaguar motor controllers we use to control the output to the window motors that move the arm.
The driver station is constantly sending the current voltage readings for the potentiometers on the control board to the robot. Meanwhile the robot is constantly reading the current voltage for its own potentiometers. After some scaling (secret sauce!) the robot determines how much its arm needs to move in order to match that of the control board, then outputs power to its arm motors based on that difference.
Discussion
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21-03-2011 16:09
connor.worley
Re: pic: FRC1899 Control Board
That's probably the coolest control system I've seen so far. Have you considered adding scale model driver stations and pegs?
21-03-2011 16:19
billbo911
Re: pic: FRC1899 Control Board
We did a similar controller this year as well. Although, we only controlled one axis. We made a scale model of our robot's arm geometry. We found that because the rotational axis moved greater than 270 deg. normal potentiometers would not cover the entire range of travel. So, we replaced the standard potentiometers with continuous rotation pots.
Here is the "secret sauce" we used for scaling.
The robot controller supplies +5vdc to an analog input device. The Cypress board only provides +3.6vdc.
So we simple multiplied the sampled voltage from the Cypress by (5/3.6)=1.389.
Here is the logic:
At one end of travel, both pots will give you 0vdc. At the other end, one will give you 5vdc and the other 3.6vdc. Both travel the exact same distance, so scaling is linear, just multiply the lower value by the scaling factor and now they are identical throughout the range of travel.
21-03-2011 16:34
nikeairmancurry
Re: pic: FRC1899 Control Board
Do you have video of this working? I'd love to see it!
21-03-2011 17:27
spacepenguine
Re: pic: FRC1899 Control Board
That's darn cool. And I thought we were clever with our pre-set positions...
21-03-2011 18:18
PaW
Re: pic: FRC1899 Control Board
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Originally Posted by nikeairmancurry
Do you have video of this working? I'd love to see it!
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21-03-2011 19:43
davidalln
Re: pic: FRC1899 Control Board
This is absolutely fantastic. Please post a video!
22-03-2011 00:13
davepowers
Re: pic: FRC1899 Control Board
Awesome control board, this is deffinatly inspirational! I'll be by your pit in St.Louis to check it out!
22-03-2011 00:15
penguinfrk
Re: pic: FRC1899 Control Board
In this picture, you can see some magnets embedded into the wooden panel. There are small pieces of metal on the scale model. The magnets are our version of the presets, having 6 magnet locations of the rack and one for transport mode. There is a physical barrier (small block of wood) that denotes the ground for tube pickup. There are youtube links in that picture thread.
Autonomous mode is on when the arm is "tucked away" under the robot, making all of the pots at their most extreme values.
We had an excellent freshman operating the arm. Best part of it? He understands every bit of programming behind it. 
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