Design of Support Platform for the Spectral MD Imaging System

Photo of Mitchell George, John Allison, Matt Tanner Students: Mitchell George, John Allison, Matt Tanner

Sponsor: Spectral MD, Inc.

Date: Fall 2009

Requirements:
A standard hospital bed is 84 inches long and 36 inches wide. Spectral MD would like the design to allow whole body scanning from one side of the bed because it is not uncommon that one side of a hospital bed is blocked by other equipment. This means that the furthest the arm will ever need to reach is approximately 55 inches in a straight line. Also, the imaging device must remain motionless during the scanning process, so the arm should require no user support in any configuration. The arm should have six degrees of freedom that allow it to reach any position required for scanning.

Problem:
Design two mobile platform prototypes for Spectral MD's new PPG imaging device. The platform should contain a manipulator arm that supports the imaging device and provides optimal degrees of freedom.

Solution:
The combination of the extension arm and end affecter provides six degrees of freedom to the imaging system. The extension arm allows translation of the imaging package along the x, y, and z axes, while the end effector provides rotation around all three axes. When placed next to the middle of the hospital bed, the extension arm's 55" reach allows the imaging package to access any part of a supine patient. The extension arm is precisely tuned to suspend the end effector and imaging payload so they remain motionless in any position after user input. Also, the end effector's friction hinges maintain its orientation in any position, regardless of the magnitude of the moments exerted on the joints. With the extension arm fully extended, the tipping safety factor of the whole system is 5, which exceeds the requirement of a 1.5 safety factor. In addition, the extension arm will always buckle before the computer-on-wheels tips, preventing catastrophic failure.

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