• • Fixed-time disturbance observer achieves convergence within a pre-settable time bound, independent of initial conditions, as proven by Lyapunov analysis with T ≤ 1/(∂1(1-∂2)) + 1/(l1(l2-1)), eliminating the initial-state dependence of finite-time observers.
• • Replacement of the discontinuous sign function with a continuous h(s) function reduces chattering, a critical industrial concern for PMSM drives in electric vehicles where audible noise and torque ripple degrade passenger comfort and component lifespan.
• • Introduction of a power term in the adaptive super-twisting controller accelerates convergence far from the origin, addressing the slow transient response that limits deployment in high-precision servo applications such as robotics and CNC machining.
• • Feedforward compensation of the estimated disturbance into the sliding mode controller enhances disturbance rejection, enabling robust performance under load torque variations and parameter perturbations typical of rail traction and aerospace actuators.