To enhance the speed control of permanent magnet synchronous motor （PMSM） drive systems， this paper introduces a new sliding mode control （NSMC） strategy with an improved exponential convergence law and an adaptive Lunberger observer. Firstly， to overcome the slow convergence of traditional exponential laws， a nonlinear adaptive function-based law is proposed， enabling faster convergence and reduced jitter for the NSMC strategy. This adaptive function also resolves the discontinuity issue of the convergence law's exponential term. Secondly， addressing the limitations of the traditional Lunberger observer， an adaptive version is developed to estimate and compensate system perturbations， offering quicker response without affecting steady-state performance， thus enhancing the system's disturbance resistance and speed tracking. Simulations and experiments demonstrate that for step speed commands at 500 r/min and 750 r/min， the system's settling times are 0.44 s and 0.71 s， respectively. When loads suddenly increase by 5， 10， and 20， the settling times are 1.16 s， 1.79 s， and 1.99 s. The proposed sliding mode control strategy significantly improves both dynamic and steady-state system performance.