In this paper, a adaptive non-linear controller is presented for permanent magnet synchronous motor (PMSM) sensorless drives. The adaptive non-linear controller is designed based on an input-output feedback linearization control technique. The unscented Kalman filter is used to estimate the speed, position and load torque. The PMSM is fed by an indirect power electronics converter. This indirect converter is controlled by a sliding mode technique that enables minimization of harmonics introduced by the line converter, as well as the control of the power factor and DC-link voltage. We study the robustness of the overall system using simulation for different operating modes and varied parameters.