Linear stepper actuators (LSAs) are devices which transform digital (or pulse) inputs into linear incremental motion outputs. They are counterparts of rotary stepper motors. When they are properly operated, the number of linear steps of the actuator equals the number of input pulses, and the mover of the actuator advances by one linear step increment, τss. LSAs have applications for short-travel linear step motion. An example of application is the Sawyer motor, which has been successfully applied in drafting equipment, head positioning, laser beam positioning for fabric cutting, etc.

Just like their rotary counterparts, LSAs may be either reluctance or hybrid (with permanent magnets). A unique feature of LSAs is that they can produce directly linear motion insteps smaller than 0.1 mm [1]. Other advantages of LSAs are as follows:

• They can operate as an open-loop system and yet yield a precise position control.

• They are robust and mechanically simple.

• They can be repeatedly stalled without any damage to the actuator.

• Required electronic controllers of LSAs are simple.

Among the disadvantages of LSAs are as follows;

• They have relatively high losses perthrust (unless the airgap is drastically reduced (to less than 0.2 mm).

• With open-loop operation, the step size is constant.

• Step response may have a large overshoot and subsequent oscillations.

• The mover weight tends to be high for the thrust produced.

• Frictional loads and linear ball bearings lead to position errors in open-loop operations.

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