Form Induced State-Drop Compensator: Compensation Scheme in Electric Motors With Zero-Speed Drop

Both power systems and mechanical systems are inevitably subject to sudden external disturbances. Existing control methods primarily address the effects of unknown disturbances through the use of observers. Influenced by the thinking of the proportional–integral–differential controller, which originated from an intuitive approach, this article proposes a novel form-inspired control scheme: the form-induced state drop compensator, also referred to as the zero-speed-drop compensator. By observing the form of state drops, a squared exponential function is designated as the compensating function for speed drops. The speed compensation function is embedded into the inner-loop current control by leveraging the partial derivatives considering speed and current, establishing a relationship between the errors over discrete time steps and the current compensation value. Subsequently, a switching compensation strategy is formulated to endue switch-like characteristics to the motor current loop, similar to the switching actions of transistors. Four parameter design theories for the compensator are then proposed, accompanied by a parameter tuning guideline. The proposed theory is validated on platforms driven by the low-inertia permanent magnet synchronous motor (PMSM), the relatively high-inertia PMSM, and the low-inertia brushless direct current motor motor-powered propeller. Experimental results demonstrate that speed drops caused by sudden large disturbances can be eliminated in small-inertia motors. This form-induced theory can be easily extended to power electronic devices, power grids, and robots in the future.