Good article, but I think the editor missed something. Units for torque aren't millimeters! Millimeters (mm) are a distance unit, torque is a force (F) vector multiplied by a distance vector (r) to yield the cross-product torque vector (T=F x r). the correct units are Newton-millimeters (N-mm), dyne-centimeters (dyne-cm), or pound-inches (lbf-in) maybe, but not millimeters (mm).
Interesting article, it is nice to see that changing the shape of the magnet can add a significant increase in the rpm of the motor. With this incredibly large rpm, it can be of great use in robotics and mechatronics applications.
Although, as this large speed is obtained at the cost of torque, and also due to the open loop nature of stepper motor it has to be limited to low torque applications, otherwise faulty conditions will arise. But its a great design acheivement by introducing a disk magnet.
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