Abstract: A multi-actuator hard disk drive includes a lower actuator with a corresponding voice coil motor assembly (VCMA), a coaxial upper actuator with a corresponding VCMA, and a central support plate positioned between the upper and lower VCMAs and to which the upper VCMA is fastened. Use of a central support plate enables some control over the direct and coupled plant transfer functions, while effectively providing a base support structure for the upper VCMA and enabling use of conventionally-sized fasteners.

Abstract: A multi-actuator hard disk drive includes a lower actuator with a corresponding voice coil motor assembly (VCMA) including a magnet coupled with a first magnet housing plate, a coaxial upper actuator with a corresponding VCMA including a magnet coupled with a second magnet housing plate, and a central support plate mechanically fastened to an enclosure base, at one or more locations, and positioned between the first magnet housing plate of the first VCMA and the second magnet housing plate of the second VCMA. Thereby, the pivot and VCM tilt and the coil torsion modes of the direct plant transfer function are minimized and the peak-to-peak gain in the coil torsion mode of the coupled plant transfer function is reduced.

Abstract: A multi-actuator hard disk drive includes a lower actuator with a corresponding voice coil motor assembly (VCMA) including a magnet coupled with a first magnet housing plate, a coaxial upper actuator with a corresponding VCMA including a magnet coupled with a second magnet housing plate, and a central support plate mechanically fastened to an enclosure base, at one or more locations, and positioned between the first magnet housing plate of the first VCMA and the second magnet housing plate of the second VCMA. Thereby, the pivot and VCM tilt and the coil torsion modes of the direct plant transfer function are minimized and the peak-to-peak gain in the coil torsion mode of the coupled plant transfer function is reduced.

Abstract: A hard disk drive includes multiple actuator assemblies, each of which includes a head-stack assembly (HSA) including an end-arm to which a single head-gimbal assembly (HGA) is coupled, where this end-arm is configured with a notch along one side and a triangular or quadrilateral-shaped through-hole at a root-side of the end-arm, and where the HSA further includes a plurality of other end- and inner-arms to each of which two HGAs are coupled and none of which have a through-hole near their root. The single-HGA end-arm may be further configured with an outer damper having a through-hole coincident with the end-arm through-hole, such that the through-hole of the end-arm is not covered by this damper, and an inner damper having no through-hole, such that the through-hole of the end-arm is covered by this damper. Gains are thereby better matched across all HGAs for problematic arm and system modes.

Abstract: A hard disk drive includes multiple actuator assemblies, each of which includes a head-stack assembly (HSA) including an end-arm to which a single head-gimbal assembly (HGA) is coupled, where this end-arm is configured with a notch along one side and a triangular or quadrilateral-shaped through-hole at a root-side of the end-arm, and where the HSA further includes a plurality of other end- and inner-arms to each of which two HGAs are coupled and none of which have a through-hole near their root. The single-HGA end-arm may be further configured with an outer damper having a through-hole coincident with the end-arm through-hole, such that the through-hole of the end-arm is not covered by this damper, and an inner damper having no through-hole, such that the through-hole of the end-arm is covered by this damper. Gains are thereby better matched across all HGAs for problematic arm and system modes.

Abstract: A hard disk drive includes multiple actuator assemblies, each of which includes a head-stack assembly (HSA) including an end-arm to which a single head-gimbal assembly (HGA) is coupled, where this end-arm is configured with a notch along one side and a triangular or quadrilateral-shaped through-hole at a root-side of the end-arm, and where the HSA further includes a plurality of other end- and inner-arms to each of which two HGAs are coupled and none of which have a through-hole near their root. The single-HGA end-arm may be further configured with an outer damper having a through-hole coincident with the end-arm through-hole, such that the through-hole of the end-arm is not covered by this damper, and an inner damper having no through-hole, such that the through-hole of the end-arm is covered by this damper. Gains are thereby better matched across all HGAs for problematic arm and system modes.