We've arrived at a new set of inputs and controls for our CVC.  Since we've mostly ruled out a propulsion mode that we were secretly considering (more on that at a later date), we don't have much of a use for the balancing plank that we presented at design review.

Our new control method consists of a large (13" diameter) plastic sphere that the user holds.  The user will tilt the sphere forwards and backwards to control speed and side to side to control turning.  The user will squeeze the sphere harder to amply the boat's speed, or he will hold the sphere gently for precise movements.  The user will calibrate the accelerometer by shaking the device to initialize a calibration sequence.  The sensors we will use are:

• 2-Axis ADXL203 (pdf) accelerometer -- this senses the forward/backwards and side-to-side tilt of the sphere for driving the boat.
• Force Sensing Resistor (2128260 at Jameco) -- Two of these, one on each the left and right side of the sphere, will detect that the user is holding the sphere.  They will also measure how hard the user is squeezing the sphere for amplifying the boat's speed.
• Optical Shake Switch -- Inspired by tilt switches, we will make our own "shake switch" that will consist of an opaque weight inside a tube.  When shaken, the weight will travel to the top of the tube and interrupt an IR LED/Sensor pair.  This action will initialize calibration of the accelerometer.
  

Here's an idea for how we can set up all our communications between PICs.  Dashed lines are connections I'm not 100% sure we need (and the dotted lines are RF communication).  One interesting idea is having the output of the PIC that reads the RFID reader connected to the input of the Security Controller.  The Security Controller would output to a second pic, and this PIC would report to the main processor on board the ACV.  We might be able to get rid of the PIC that interfaces with the Security Controller by putting the Security Controller and the Xbee on the same EUSART lines.  Doing so may or may not be easier.

The control method that we will be presenting at the design review will consist of a plank with force sensors (for speed control), a steering wheel with accelerometer control (for turning), and a microphone (for capturing an atoll -- we couldn't think of another reason to have a third input method).  We've also been brainstorming about alternative control methods.

One that could be very precise and intuitive to use could consist of a handle (either T-shaped or spherical, for instance) that the user grasps.  The user could tilt this handle forward for speed input, which would be registered by an accelerometer.  The user could also tilt it side-to-side (measured by a multiaxis accelerometer) or slide it horizontally (measured by a linear pot or a rotary pot with some mechanism) for turning movements.  This could be a cool, smooth input method.

So I've been thinking about general design ideas while I went to SPDL and discovered the communication committee meeting got pushed back an hour.

One major thought:  our Illustrious coach mentioned the other day that there was no requirement to actually make the boat from scratch!  He said that about half the people from his year used existing boat hulls and modified them to suit their needs, and the other half started from scratch.  He also said that some of the guys that built from scratch had a major disadvantage in that they didn't have anything to test till late in the game.  Perhaps it would be a good idea to get Javier working fine first off, while we work on a boat, and should the worst happen, its no biggy.

Second thought:  Instead of speed, there is a decent chance we will be more limited by a need for agility as we maneuver around the tight quarters of the atoll trying desperately to make the RFID Cards line up and read.  We have to be literally within inches, which may not sound that bad, but its in every axis, and I would imagine may be even more sensitive to out of alignment errors.

The propellers are really nice as they are easy to implement and really fast, but we might still want to keep in mind a dual paddle differential  wheel design as well.  I would imagine it would be more agile.  The obvious trouble is the increased mechanical complexity.  A couple of things are good here though:  I think perhaps the load on the motor is not actually as bad as it sounded at the beginning.  Since its a boat, and not wheels, it wont have to carry its own weight on the motor shaft.  If we extend the motors into the area of the paddle wheels, it may not be impossible to center the load in such a way that its largely just sheer on the shaft.  The goal would obviously be to make these things as light as humanly possible, so the weight of the wheel shouldn't be huge, and then if its made of foam (more on that in a minute) then it might actually end up being at least partially buoyant.

At first I was thinking about using like acrylic or something for the paddle wheels, and then I remembered how incredibly light my helicopters are, with a surprising amount of strength.  what if we used closed cell Styrofoam, as the structure and then laminated the outsides with a layer of waterproof aluminum foil tape??  They sell it on mcmaster, and it looks like it might actually be legit.  I've used regular aluminum foil tape before, and the ahem, "stuff" is ahem "freaking" fantastic! Super stiff and strong, the styrofoam is just there to give it a distance on 2 layers apart.  I'm not saying this is the way to go, but it might be worth a quick prototype.  If we can get the weight down, paddle wheels might be really useful in tight quarters.
found a video of a dual paddle bot. completely random art design, and worst paddle design ever, but still looks pretty dang agile and simple:

http://www.societyofrobots.com/robot_thai_boat.shtml

Also, Hoff from class got a little 3 axis accel from spark fun.  Seems pretty surprisingly simple.  analog out for each axis, and we have analog in on the pic.  Might be an ok option for one of our sensing modes.

Ok, thats all I have for now...
-D

We received the project today.  We started thinking about and researching what sort of propulsion mechanisms our vehicle could take.

Some boat and underwater ideas, from YouTube research.
 - Can DC motors go underwater?  Yes, if they are brushless.
 - Might a paddle wheel work?  Sure, but maybe slowly.
 - Something crazy?  Swamp boat!