Fig. 2. Design for control example from [35] modifying actuator design to eliminate translational loading in voice-coil motors. (a) In disk drives, the actuator for the read/write head is a typical lorentz-force voice coil motor that produces a force at an offset. The force also excites the translational mode of the bearing. (b) A novel design for the voice coil motor, based on a magnetic array called as Hallbach array, which is commonly found in linear motors, is used in a rotary configuration to produce a unidirectional magnetic field in the hub. (c) The resulting actuator is a pure torque motor that minimizes the effect of the translational mode of the bearing.
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