HP48SX MES Message #1 Posted by J. Veazey on 13 Mar 2007, 8:34 p.m.
(The 48 is my office machine; I have an HP50g at home for serious play).
I've got an application that seems to be tailor made for the MultiEquation solver, yet MES consistently tells me I have too many unknowns.
This is a vector triangle problem, having to do with the placement of sonobuoys in front of an advancing convoy by an ASW helicopter, and the flight time and course of the helo.
Here are my 3 equations:
Ca=Sr+Vc*Slt+Vc*t
R=SQRT(Ca^2+D^22*Ca*D*cos(alpha))
t=R/Vh
My 3 unknowns are:
Ca  convoy advance
R  flight distance of helo to sonobuoy location
t  flight time of helo to sonobuoy location
All the rest of the variables above are known constants:
Sr  sonobuoy detection range
Vc  convoy speed
Slt  sonobuoy lifetime
D  Distance from convoy to helo at start
Vh  helo speed
alpha  Angle on the bow from the convoy to the helo
This system can be solved iteratively by just cycling thru the 3 equations to generate updated values of the unknowns. It usually takes about 7 or 8 iterations to converge to full displayed accuracy (which is way overkill).
I have set it all up in its own directory. I have done an MINIT, and an MITM just fine. When I punch MSOLV softkey, all the softkey labels act like they should, displaying all my variable names on white softkeys. I initialize the constants and those soft keys turn dark to show they are not variables.
When I try to solve via LSALL, I get the message "Too Many Unknowns". Trying to solve for a single variable also fails with the same message.
I have tried reordering the equations. No joy. I even added the other 2 angles in this vector triangle as unknowns, and more triangle relations (3 law of sines equations) and the equation Pi=sum(the angles in the triangle). I hoped this would help since I added just 2 more variables, and 4 equations. But, attempting to solver still gets the "Too Many Unknowns".
Am I doing something wrong, or is this system simply something that the MES can't handle? It seems too simple for that to be the problem, but ....
