Determine the linear combination of the two inputs: y = y0*(1 + k1*u1 + k2*u2)
y = y0*(1 + k1*u1 + k2*u2)
Note, for y0=0 the output is always zero.
To improve the implementation, the formula will be changed (non-backwards compatible) in the future: y = y0 + k1*u1 + k2*u2
y = y0 + k1*u1 + k2*u2