In this paper, we consider the observer design problem for permanent magnet synchronous motors (PMSMs). We assume that only the stator current and control voltage are measured, while all motor parameters are known. The load torque is unknown and assumed to be constant or slowly varying over time. We propose a new one-stage observer based on the Generalized Parameter Estimation-Based Observers (GPEBO) method, which simultaneously estimates rotor speed, flux, and load torque. The observer explicitly accounts for viscous friction, a factor that was not always considered in previous studies. The simulation results demonstrate the effectiveness of the proposed approach. © 2025 Elsevier B.V.. All rights reserved.