<p>This paper proposes a novel adaptive second-order sliding mode (ASOSM) controller for speed regulation in permanent magnet synchronous motor (PMSM) drive systems. Initially, an adaptive law is designed based on the principle of integral dynamics to realize the handling of disturbances without the need for a known disturbance boundary. Subsequently, the second-order sliding mode (SOSM) is constructed through the adding-a-power-integrator methodology, ensuring finite-time convergence while maintaining system robustness. Unlike conventional SOSM methods that rely on fixed gains and known disturbance magnitudes, the proposed ASOSM introduces a self-regulating mechanism that dynamically adjusts the control gains based on system states. This approach enhances robustness and significantly reduces steady-state chattering under uncertainty. Finally, comparative experiments are conducted to compare the ASOSM proposed in this paper with a variety of other methods. The experimental studies demonstrate the superior performance of the proposed ASOSM.</p>