Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

Thread Subject:
System of equations Symbolically

Subject: System of equations Symbolically

From: Sean_C_1999@yahoo.com Currie

Date: 25 Apr, 2009 00:17:04

Message: 1 of 3

We are looking for 10 equations that are functions of the variables A,
B, C and D as well as the variables TS1, TS2, TS3, TS4 and DS1, DS2,
DS3, DS4, DS5, DS6 (read these as single variables with numerical
subscripts IE. TS1 is a single variable where 1 is a subscript).

We currently have 10 equations and 10 unknowns, however our current
equations are functions of both the above variables and other
functions.

T1 = TS1*(A+D1+D4+D6)
T2 = TS2*(B-D1+D2-D5)
T3 = TS3*(C-D2-D3-D6)
T4 = TS4*(E+D3-D4+D5)

D1 = DS1*(T1-T2-A+B+D2-D4-D5-D6)
D2 = DS2*(T2-T3-B+C+D1-D3+D5-D6)
D3 = DS3*(-T3+T4+C-E-D2+D4-D5-D6)
D4 = DS4*(T1-T4-A+E-D1+D3+D5-D6)
D5 = DS5*(-T2+T4+B-E-D1+D2-D3+D4)
D6 = DS6*(T1-T3-A+C-D1-D2-D3-D4)

Subject: System of equations Symbolically

From: Roger Stafford

Date: 26 Apr, 2009 07:06:03

Message: 2 of 3

"Sean_C_1999@yahoo.com Currie" <Sean_C_1999@yahoo.com> wrote in message <gstkq0$e3n$1@fred.mathworks.com>...
> We are looking for 10 equations that are functions of the variables A,
> B, C and D as well as the variables TS1, TS2, TS3, TS4 and DS1, DS2,
> DS3, DS4, DS5, DS6 (read these as single variables with numerical
> subscripts IE. TS1 is a single variable where 1 is a subscript).
>
> We currently have 10 equations and 10 unknowns, however our current
> equations are functions of both the above variables and other
> functions.
>
> T1 = TS1*(A+D1+D4+D6)
> T2 = TS2*(B-D1+D2-D5)
> T3 = TS3*(C-D2-D3-D6)
> T4 = TS4*(E+D3-D4+D5)
>
> D1 = DS1*(T1-T2-A+B+D2-D4-D5-D6)
> D2 = DS2*(T2-T3-B+C+D1-D3+D5-D6)
> D3 = DS3*(-T3+T4+C-E-D2+D4-D5-D6)
> D4 = DS4*(T1-T4-A+E-D1+D3+D5-D6)
> D5 = DS5*(-T2+T4+B-E-D1+D2-D3+D4)
> D6 = DS6*(T1-T3-A+C-D1-D2-D3-D4)

  I am guessing from your description that T1, T2, T3, T4, D1, D2, ..., D6 are to be regarded as the ten unknowns to be solved for. (You didn't say so explicitly.)

  To do this symbolically you can either use 'linsolve' or 'solve' in the Symbolic Toolbox. The 'linsolve' function will require you to manipulate with your equations appropriately, but 'solve' can use the equations as they stand. In any case be prepared for a possibly very messy answer. You can use functions like 'simplify', 'expand', 'simple', 'factor', 'collect' and the like to attempt to make the solutions simpler, but sometimes these need help from the user to succeed in this endeavor. Of course all this presupposes that you have the Symbolic Toolbox available.

Roger Stafford

Subject: System of equations Symbolically

From: Roger Stafford

Date: 26 Apr, 2009 07:25:03

Message: 3 of 3

"Roger Stafford" <ellieandrogerxyzzy@mindspring.com.invalid> wrote in message <gt114r$9pp$1@fred.mathworks.com>...
> To do this symbolically you can either use 'linsolve' or 'solve' in the Symbolic Toolbox.

  I notice that 'linsolve' is no longer available in the Symbolic Toolbox, so just use 'solve'.

Roger Stafford

Tags for this Thread

No tags are associated with this thread.

What are tags?

A tag is like a keyword or category label associated with each thread. Tags make it easier for you to find threads of interest.

Anyone can tag a thread. Tags are public and visible to everyone.

Contact us