Page 21 - Fuel Cell Student Edition

MODEL OUTPUT ❖ Kinetic energy is proportional to mass and
speed
❖ Rover height
❖ Rover distance traveled ❖ Total Mechanical Energy = Potential Energy +
Kinetic Energy
❖ Maximum slope
❖ Total mechanical energy needed to traverse the ❖ More energy is required to go uphill than
path downhill
❖ Power rover battery needs to deliver to traverse ❖ Converting energy from one form to another is
the path not 100% efficient (chem. to elec. to mech.)

❖ The power needed at a particular point may
KNOWN AND UNKNOWN INPUTS be higher than the average power needed (one
short but steep slope)
KNOWN:

❖ Rover mass ASSUMPTIONS / CONSTRAINTS
❖ Gravitational acceleration of moon ❖ Constant velocity

❖ Rover path ❖ No additional energy consumed to
turn the rover
❖ Rolling resistance of tire in sand
❖ No additional energy for powering accessories
❖ Electrical to mechanical energy conversion
efficiency

❖ Maximum rover grade Now that our requirements have been satisfied, we
begin to design our model. Because we will assume
❖ Fuel cell power output (from fuel cell lab)
that turning the rover takes minimal energy, we
will not model it. Therefore we will be performing a
UNKNOWN: 2d analysis of the rover path. It will contain height
and position data. The problem is now, how do we
❖ None (thus far) convert a 3-dimensional path into a 2-dimensional
one. We will use a free software program from the
National Institutes of Health (NIH) called ImageJ to
SCIENTIFIC PRINCIPLES/ examine our height map and pick points along the
CONCEPTS/FORMULAS path. These points contain 3 pieces of information:
height (in the form of the pixel’s brightness, or value),
❖ Law of conservation of energy
X location, and Y location. If we straighten out the
❖ Forces as vectors and components path, we are left with a 2-dimensional representation
of it. This is not the same as a projection. A projection
❖ Force required to keep mass from rolling down would skew the distance data between points. We
an incline
are simply ignoring the horizontal angles (turning)
❖ Potential energy is proportional to mass and between the points while the distance and slope
height (uphill and downhill) remains unchanged.

20 TOTAL REDOX™ – FUEL CELLS TOTAL REDOX™ – FUEL CELLS 21