Project+Definition+Document

Saturday October 24,

I have updated section 10.2 in the PDD as was discussed on Wednesday.

Andrew

Here is the final draft of the PDD. I am printing this version and will submit it at the beginning of today's lecture. Please remember to insert the files you upload here onto the appropriate page (ie home page). Files that are uploaded but not posted to a page are inconspicious and other group members may not find them right away, as has been the case this week.

-Mitch

THis is posted as a document as well, and has been since Monday morning. IT is here as well so you don't miss it.

Background: Human locomotion is a popular area of study and one that influences many areas. A full understanding of human locomotion is important in many medical fields. When the basic principles of normal walking are understood, it is possible to understand pathological or compensatory gait deficits. People looking at prosthetic design, creating orthotics, or aiding in the rehabilitation of a patient that is relearning how to walk can utilize this information. Dr. Bertram is currently studying locomotion using the basis that people’s gait is such that momentum losses are minimized [1]. An extension of the theory that human gait minimizes momentum losses proposed by Dr. Bertram is that human gait will entrain to ambient movements. When the Millennium footbridge opened in London in June of 2000, an estimated 80,000 people crossed it. The response of the bridge to the motion of the people crossing it was unexpected. A phenomena now being referred to as synchronous lateral excitation caused the bridge to sway sideways upwards of 70mm. Eventually the bridge was shut down so this could be studied and it was determined that chance correlation of footsteps from the crowd generated a slight sideways movement in the bridge. As this occurred it became more and more comfortable for people to walk in synchronization with the bridge movement, increasing the total sideways force. Damping has since been added to the bridge to prevent excessive lateral swaying [2]. This occurrence adds evidence to the proposal from Dr. Bertram that human gait minimizes momentum losses. In order to prevent momentum loss human gait will entrain to external movement or stimuli. This proposal offers new insight into human locomotion and creates a new approach to studying human gait. In order to further investigate this phenomenon Dr. Bertram has proposed a device to mimic the feeling of walking on an unstable bridge by changing the center of gravity of a subject while they are walking. The original apparatus concept was a vertically oscillating treadmill that would mimic an unstable bridge however this design was deemed impractical due to the amount of power it would take to run it. As an alternative a device will be created that attaches to a subject’s back with an oscillating weight. This will alter the center of mass of the subject, giving them the same feeling of motion as walking on an unstable bridge. This device will be used to further Dr. Bertram’s research on human locomotion but may also have eventual potential to be used for rehabilitation purposes. Goal: TO design a wearable device that shifts the centre of mass of a subject. The device will involve a mass oscillating at up to 4 Hz with amplitude of 4 cm. Normal motion should not be affected when the device is worn but not turned on. References: [1] Ruina, A., J. Bertram & M. Srinivasan, "A collisional model of the energetic cost of support work qualitatively explains leg sequencing in walking and galloping, pseudo-elastic leg behavior in running and the walk-to-run transition,” //Journal of Theoretical Biology//, Vol. 237, pp. 170-192, 2005. [2] ARUP. "The millennium bridge." [Online] Available: http://www.arup.com/ MillenniumBridge/index.html (Accessed October 11, 2010).

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The device must be attached to a person such that the center point of oscillation can be adjusted within 5cm vertically of a person’s L5 or L4 vertebra. =====

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This objective is to ensure that the oscillation of the mass occurs equally above and below a person’s center of mass. A person’s center of mass is located approximately near a person’s lumbar 4 (L4) or lumbar 5 (L5) vertebra, although it is in a slightly different location for each person. Having vertical adjustability in the mounting system will ensure that the device is properly situated for any person. An adjustable height for the device will also help to ensure that the device will not interfere with a person’s normal gait when walking. =====

Feel free to make the above less specific if you feel it is appropriate.
Andrew

4.3.1 Amplitude
Design the apparatus such that the amplitude of oscillation is controlled.

4.3.2 Discussion The amplitude must be controlled so as to move the mass independently and not be affected by the subjects motion, or lack there of. A consistent and controlled amplitude is crucial for accurate research data.

4.2.1 Mass
Design the apparatus such that it has the ability to oscillate a mass.

4.2.2 Discussion Addition of external mass to a subject is necessary to alter that subject's center of gravity. Alteration of the subject's center of gravity is integral to the customer's planned experiments.

4.1.1 Ergonomics

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It is necessary to prevent strain on the body that will affect research studies. It takes the study of how individuals walk and how a testing equipment can be attached without hindering motion. =====

11 Oct 2010

I have added a Web Updates page to the wiki (See to the left). Let me know what you think of the pre-lim version of the webpage. I believe it will be a good idea to use the web updates page to upload pictures/documents etc so that I will be able to put them on the webpage once we get up and running.

-Andrew

Functional Block Diagram -Andrew