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The overall height of the motor is sufficiently low to fit in the base plate of the turntable. Secondly, the GN9T motor uses an iron-free armature for zero cogging and no torque ripple under load, so that the motion is extremely smooth, ensuring angular precision of the workpiece

The motor is coupled to a zero-backlash strainwave gearbox, for precision angular motion. As there is a high ratio reduction gearbox between motor and turntable, even the slightest ripple in the torque would be amplified. This is eliminated with the GN9T motor.

One of the key components for a new robot developed for a novel warehouse storage and retrieval system was its motor. As no commercially available motor fitted the company’s demanding specifications, PMW was asked to design and develop a compact but powerful model that could move the robots horizontally as well as raise and lower their loads.

The type of motor chosen was a permanent magnet brushless motor with an external rotor. Having its high strength neodymium magnets positioned on the externally running rotor gives it the fundamental advantage that the torque is generated at maximum radius, enabling it to produce high torque smoothly and over a wide range of speeds

Precise individual control of the robots was required, with positional feedback from the robot to the control system

During development, PMW precisely modelled the motor within the customer’s specification constraints, in order to optimise efficiency and unit cost. Electromagnetic modelling of the motor was carried out over a number of iterations, with the thermal studies based on the different duty cycle models and updated after customer reviews

The short axial length of the motor was crucial, since if it was as little as 2 mm longer it would have led to a substantial increase in the overall warehouse area