In Eq. (3-31) and Eq. (3-32), the speed terms are the components
that are proportional to ωdA (the speed of the dq reference frame relative
to the actual physical rotor winding speed) and to the flux linkage
of the orthogonal winding.
Equation (3-31) and Equation (3-32) can be written as follows in a
vector form, where each vector contains a pair of numbers—the first
entry corresponds to the d-axis and the second to the q-axis: