Date of Defense
Electrical and Computer Engineering
Dr. John Gesink
Dr. Janos Grantner
The objective of this project was to design and implement a small device that would emulate memory chips used in surgical power tools made by Stryker Instruments, the sponsor. These memory chips are used to store motor control settings such as minimum and maximum voltages, minimum and maximum currents, torque versus speed curves, and many other parameters.
During development, engineers perform many experiments to determine the optimal settings for a particular motor. Previously, new memory chips had to be programmed each time a setting was to be changed. This process had been very time consuming and tedious, taking 5 minutes for every incremental adjustment. This project, the TPS NVRAM Box, was designed to make this process more efficient. Now, using the NVRAM Box, this process takes between three and four seconds.
The device has been implemented using a Phillips 8-bit microcontroller, embedded software, CPU software, and serial communication. The electronic components used in the microcontroller circuit design were built onto a printed circuit board that was also designed by this group. The printed circuit board was then integrated into a small plastic enclosure. This makes the NVRAM box portable and very easy to use. The NVRAM box allows the surgical power tool connected to it to operate exactly as it normally would, except that the motor control parameters are read from the NVRAM box instead of the tool's embedded chip. The CPU software is user-friendly and allows new settings to be quickly and repeatedly downloaded to the microcontroller.
This project's ultimate success can be attributed to Stryker's financial support, access to their electronics lab and other facilities, and technical advice from their engineers. The project proved to be very challenging, but turned out to be a great success. Thirteen of the fourteen specifications were met in their entirety. The one specification that was not met proved to be unfeasible.
Dozeman, Mike; Graves, Cory; and Westphal, Grant, "Memory Chip Emulator for Surgical Power Tools: "TPS NVRAM Box"" (2001). Honors Theses. 1485.
Honors Thesis-Campus Only