I have troubles solving this question:

Given the general DC motor governed equation, find the control voltage such that the speed w tends to constand reference input w* and the convergence rate is determined by the desired eigenvalues L1 and L2.

I think it's easy to find the control voltage to the speed w. However I don't know how to find "convergence rate" which is determined by the desired eigenvalues. Can anyone give me some suggestions? Thanks.