There are a number of challenging factors that influence the performance of the industrial servo systems. One of these factors is the inertia mismatch between the motor and the load. Another problem is the variable-inertia load. This paper applies a robust control tool called μ-synthesis to design a controller which deals with the uncertainty of the inertia in the
load. Different practical experiments are presented to investigate the effect of some parameters in the synthesis process on the performance of the synthesized controller. Also simulations are included to introduce different values of inertia mismatch and study the effect of increasing inertia mismatch on the servo system performance. It has been found the robust controller can deal with variable parameter control problem with adequate weighting functions. Also the increased inertia mismatch has been found to slow the servo system down and demand higher control action.