A classical PID controller for a certain turntable positioning system is enhanced to compensate for the Coulomb friction by incorporating an inner acceleration feedback loop. The acceleration signal is assumed to be computed based on friction estimation. In order to estimate the frictional torque, a novel nonlinear observer is developed. And its global asymptotical stability is proved as well. The simulation results are given against those obtained by classical PID control without acceleration feedback loop, to demonstrate the effectiveness of the proposed approach