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# Global optimization of discrete variablesShape Optimization of Hard Disk Drive Head Support Arm

## Analysis Case

### Overview

A hard disk drive (HDD) writes, retains and reads data in very high density. Its precise operation is supported by its own components, including a magnetic head. A magnetic head writes and retrieves data from rapidly rotating disk media. When moving, it accelerates faster than a Formula One car, and when stopping at a target position, it decelerates more quickly than a jet when it lands. To position a magnetic head on a fast-running hard disk drive, it is necessary to suppress oscillation of the head tip. One way to do this is to reinforce the support arm, but this will make it difficult to get rapid access due to the additional weight. This case example illustrates shape optimization of a support arm that prevents radial oscillation by putting the head tip on the node of oscillation.

### Analysis model

Real eigenvalue analysis model of a support arm equipped with a magnetic head

### Optimization model

Objective Minimization of head tip displacement in the disk radial direction Natural frequency Material type (discrete variables), plate thickness (discrete variables), geometries of the reshaped part (continuous variables), radius and width of the hole

## Example of Analysis Using the Solution

Below is a case where noise terminal voltage in a flyback converter is minimized using Optimus's optimization function called Differential Evolution (DE). The switching element, noise filter and snubber circuit are defined as variables to specify the optimal combination of elements for noise reduction.
A simple flyback converter with wiring inductance and stray capacitance is used as an analysis model, and the noise is calculated by inserting an LISN equivalent circuit in the power line.
Not only does it perform automatic analysis using string variables, it also provides results equivalent to analysis where every possible combination is calculated, in one fifth of the time. The workload for designers can be significantly reduced using this optimization algorithm.