BECKHOFF AL2000 - Manual (Page 9)

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9
Linear and rotary motors compared
A rotary motor opened up and laid out flat
It will be notified that a linear motor is based on the same physical principles as the normal rotary electric motor.
In fact a linear motor is a rotary motor opened up and laid out flat (see figure). Hereby the function of the rotor is
transformed in the slide function. The torque has become a linear force and so the rotary movement has chan-
ged to a flat movement.
Because of its flat topolgy the main advantage of the linear motor is apparent. It generates a direct linear mo-
vement. Whereas a rotary motor needs some kind of transmission, the linear motor directly provides it.
The direct drive results in some significant advantages.
•
Accurate position control and response is possible at submicron level.
•
A linear motor provides a smooth and controlled motion. No velocity ripple.
•
In comparison with standard rotary motor systems a high velocity and acceleration performance is ob-
tained. This is due to the high ratio of peak force to motor inertia.
•
Except for the side bearings there is no contacting surface. Friction is negligable, virtually no wear.
•
The only limitation on travel displacements is the length of the magnetplate. In the case of added
length there are no speed limitations nor is there a higher inertia or lower dynamic stiffness.