An improved LADRC based on composite disturbance compensation for SPMSM speed control

In surface-mounted permanent magnet synchronous motor (SPMSM) speed control, proportional-integral (PI) regulation has limited disturbance rejection, while conventional linear active disturbance rejection control (LADRC) still couples reference tracking with disturbance attenuation. Sudden load torque changes may also cause linear extended state observer (LESO) lag and delayed compensation. This paper proposes a composite-disturbance-compensation LADRC (CDC-LADRC) strategy. The current loop retains PI control, and the speed loop introduces a first-order reference-input optimization link and a load-torque observation compensator. The former smooths abrupt speed commands, while the latter estimates the dominant external disturbance from the PMSM mechanical equation and provides feedforward compensation, leaving the LESO to reject residual disturbances. A simplified speed-loop model, boundedness analysis, and bandwidth-based tuning rules are developed. Simulation and back-to-back experiments show that the proposed method reduces command-induced current impact, suppresses speed drop under sudden load, and shortens recovery time compared with PI control and conventional LADRC.