<p>This paper researches the composite nonlinear feedback (CNF)-based sliding mode control (SMC) method for permanent magnet synchronous motor speed regulation systems. Firstly, according to the dual closed-loop cascaded control framework and taking the current characteristic into full consideration, an accurate second-order mathematical model of the speed loop is consequently established. Then, on the foundation of the traditional equal-velocity reaching law, a novel variable-velocity reaching law is presented by introducing the system state error, and their characteristics are compared and analyzed in detail. Furthermore, the CNF control technique is considered to dynamically change the damping-ratio, such incorporating into the designed SMC law and eventually resulting a smooth switching function-based speed regulator. Finally, the advantages and effectiveness of the proposed approaches are demonstrated by the comparative simulations and experiments. The research results illustrate that the proposed CNF-based SMC strategy can realize the speed tracking without any overshoot, meanwhile the control system has favorable dynamic performances and possesses strong robustness against the external load disturbances.</p>