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Matrix Help

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Matrix Help

For a school project involving the modeling of the dynamics of a hydraulic servovalve, I need to create matrices in order to create the transfer functions for valve model.

Now when I try to make a 3x2 matrix, I need the values to be [0 0; 0 1/m; K 0].

I have modified the variables m and K to be unitless. However, I get an error with the 2nd 0 ( [0 0; 0 1/m; K 0] ), has a unit of A/m^3 although I entered 0.

Later I get an error with another matrix in which it claims that a constant is 'unitless' while everything else is '[]unitless'

Any thoughts?

Thx

Finny

4 REPLIES 4

Re: Matrix Help

Finny wrote:

For a school project involving the modeling of the dynamics of a hydraulic servovalve, I need to create matrices in order to create the transfer functions for valve model.

Now when I try to make a 3x2 matrix, I need the values to be [0 0; 0 1/m; K 0].

I have modified the variables m and K to be unitless. However, I get an error with the 2nd 0 ( [0 0; 0 1/m; K 0] ), has a unit of A/m^3 although I entered 0.

Later I get an error with another matrix in which it claims that a constant is 'unitless' while everything else is '[]unitless'

Any thoughts?

Thx

Finny

From the sound of it you have hit on the limitation that arrays need to be all of the same unit (strictly, dimension).

The solution is to put all values into the same, preferably coherent, system of units (eg, SI) and then write your worksheet in a unitless form; alternatively, use conversion constants to make all value unitless, then restore the results to the expected units.

Stuart

Re: Matrix Help

We can have in Mathcad **-15 vectors and matrix with unitless values or with values of one dimention (mass, time etc).

We can have vectors and matrix with values with different dimention only in Mathcad Prime.

One example (sorry - in Russian):

http://twt.mpei.ac.ru/TTHB/1/chain.1.jpg

Re: Matrix Help

that is what I have been with all my variables, m, b,etc. They are all unitless when they go into the matrix. The problem however is when I put a single digit eg 0 or 1 into the matrix, for some reason mathcad automatically gives the matrix a unit even though I just want the digit.

Re: Matrix Help

Finny wrote:

that is what I have been with all my variables, m, b,etc. They are all unitless when they go into the matrix. The problem however is when I put a single digit eg 0 or 1 into the matrix, for some reason mathcad automatically gives the matrix a unit even though I just want the digit.

Finny,

Could you please post your worksheet (or an extract that shows the problem)?

Stuart