problem with multi linear regression, because of scaleabilitiy

Hi,

Currently I am trying to find several dynamic parameters of a linear motor. (D dampingcoef, C forcecoef and a variable linear mass= (M+m*x))

My system of equations is:

D*x+M*y+m*z=C*f

Where x y z f are arrays of measured values

Is there a way to use a multilinear regression in order to find (D,M,m and C)? My problem is that with the regular methods I can just change C and still find solutions in other words its not a finite solution.