HDD - Testing

The Hard Disc Drive (HDD) project appears in three sections of this portfolio. Here is a summary of the project (repeated in all three sections):

For my senior project in mechanical engineering at CU, I was part of a five-member team that developed a systems-testing tool for the Research and Development area of Hewlett Packard (HP). HP received customer complaints about the noise levels of some of their computers. The cause of the noise was determined to be vibration from Hard Disc Drives (HDDs), which HP purchases from third parties. The solution to the problem is to develop damping techniques within the computers using test results from HDD vibration, however actual HDDs do not have a reliable vibration output. We were asked to build a tool to accurately simulate HDD vibration in a more repeatable manner to facilitate testing. This was accomplished by modifying four actual HDDs, which involved removing the discs and most other hardware from the interior of the HDD form factors, and replacing them with a fiber optic sensor to give live feedback of the motor speed. We took control of the motor with our own pulse width modulation circuit in order to adjust the frequency, and adjusted the amplitude of vibration by changing the mass and balancing of the motor itself with different combinations of screws.

HDD Testing

Both the HDDs and our HDD simulator modules required extensive testing over the course of five months. We needed to characterize the HDDs in order to closely match their typical vibration behavior with our modules. Once the modules were running, we tested them to determine their initial behavior and refine their performance until we could control them with a satisfactory baseline vibration level. We then tested levels of increasing vibration amplitude settings to characterize our modules for HP test engineers.

I was responsible for creating the test plan, determining metrics with which to characterize and compare the HDDs and modules, developing the test platform and software, and finally performing the tests and analyzing the data. After comparing several potential test beds, I used 2" soft foam to isolate HDDs from the surrounding environment. They were also tested installed in a computer chassis. I wrote a LabView program to digitize and record take time-domain vibration data from an accelerometer placed on the test subject through our data acquisition (DAQ) system.

I wrote a MATLAB program to read the raw LabView accelerometer data sets, average them, subtract background noise and perform a Fast Fourier Transform (FFT), which broke the vibration data for a single tested HDD into component frequencies. Next, the program located all peak frequencies in the range and with the criteria I wanted, measured their frequency, amplitude, full width at the maximum height (FWHM), and computed the error in ten measurements. I wrote a second program to plot and list the resulting data in a table, which facilitated comparisons between different HDDs, as well as differences between the HDDs and our modules.