The papers in this special section focus on position sensorless AC motor drives. Rotor position and speed information is crucial for highperformance ac machine drives. Since the merits, such as cost reduction, system downsizing, and reliability enhancement can be achieved through position sensorless (also noted as self-sensing) control, many techniques for a wide range of rotor speed from standstill to high speed have been developed in the last few decades. Sensorless control techniques have been commercialized and widely used in industrial applications. However, there are still a large number of unresolved issues, which limit the applications of sensorless ac motor drives. The extreme speed sensorless control is still a big challenge. Besides, the robustness of the position estimation scheme against timevarying parameters, inverter nonlinearities, multisaliency, etc., also aggravate the control performance in some applications. This Special Section on “Position Sensorless AC Motor Drives” in the IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS provides an insight into some of the newly emerging challenges and potential solutions to overcome those aforementioned issues. It will be timely and of great interest for all those working in this area and, of course, for industry.

Fil: Solsona, Jorge Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages"; Argentina

Fil: Valla, Maria Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina

Fil: Wang, Gaolin. Harbin Institute of Technology; China