<p>With the expansion of their applications, velocity regulation of the PMSM motors is considered a challenging issue nowadays. This article deals with increasing the resistance of the PMSM motor velocity regulation loop against sudden load changes. For this purpose, in this article, a non-singular terminal sliding mode observer (NSTSMO) is created to estimate the load torque online as well as refer it to the regulator for compensation. A traditional sliding estimator has a high chattering phenomenon and low convergence speed. To solve this problem, this research proposes an NSTSMO estimator where the chattering phenomenon is greatly eliminated and it has a higher convergence speed. The load torque estimated by this estimator is referred to by the sliding regulator to increase the resistance of the whole control loop to load changes, hence increasing the speed tracking accuracy. The outcomes of the presented control structure have been tested during a series of practical experiments, and its performance was compared to a conventional sliding strategy without estimation. These outcomes have shown that the recommended strategy has a higher convergence accuracy than the conventional sliding strategy.</p>