One of our primary goals is to install a controller which, when activated, will keep the submarine at the optimum angle of attack and on an even keel for the straight-line portion of the race this summer.
In order to accomplish this, the controller must perform a variety of different logic functions, and it must do it underwater reliably.
The functions that the controller must perform are shown below graphically in the form of a Simulink block diagram. Please note that this block diagram serves only as our starting point, and it will change as the project progresses. The block diagram represents the analytical solution to the control problem. However, the actual hardware that we choose, the dynamics of the submarine in the water, and component placement all have limitations and implications upon this analytical solution. In other words, it will change often.
The controller consists of a microprocessor, an accelerometer, and a set of servos.
The microprocessor is a BasicStamp2, currently mounted on the Homework Board, which is manufactured and distributed by
The accelerometer is a Memsic 2125 model, which is also distributed by Parallax. The accelerometer provides a square wave output signal that the microprocesser reads and converts to a tilt angle on the x- and y-axis simultaneously. This input is then used to position the servos at the proper angle for the control surfaces to be most effective in keeping the boat at its best angle of attack for maximum speed.
If this sounds complicated, take a look at the governing equations behind this system
We chose this particular microprocessor system because it is relatively inexpensive and is more than capable of performing the tasks that we demand of it. This has a two-fold advantage: We're going to take this underwater, over and over again. If it gets wet...well, we can afford a few spare parts. The second advantage is the small power supply needed. Submarines don't have much extra space, especially subs designed to go fast for short distances. Since our sub is manned, we're dedicating as much space as we can to breathing gas for the pilot. Batteries don't help us breath in an emergency.
To date, the controller is functioning as a proportional controller. It isn't installed in the sub yet, as we're building the waterproof boxes and stuffing tubes at this time. This page will be updated as the project progresses.
