The Programmable Permanent Magnet Actuator: A Paradigm Shift in Efficiency for Low-Speed Torque-Holding Robotic Applications

In this letter, we propose a new type of electromagnetic actuator called the “programmable permanent magnet” (PPM) actuator. The PPM actuator is designed to tackle low-speed high-torque applications where classic electromagnetic actuators are highly inefficient. The PPM actuator is based on the application of pulsed current to magnetize a hard ferromagnetic stator that is made of individual SmCo (custom grade) magnets placed in a Halbach array configuration. The motor creates a springlike torque function that generates up to 0.2 N·m. Unlike electromagnetic actuators, by design, the PPM actuator does not draw current while exerting torque. Instead, the motor's power consumption depends on its rotational speed or torque variations. The PPM actuator is, by consequence, most efficient, whereas classical electromagnetic motors are most inefficient, and is a new alternative to actuators for robotic applications, which tend to operate in low-speed, high-torque conditions. The prototyped PPM actuator measures 47 mm in diameter, with a height of 35 mm and weight of 200 g, and has been successfully integrated in a commercially available 2-finger gripper from Robotiq, Inc.