Abstract

1. In Shoe Pressure Measurement and Analysis in relation to Foot Strike Saba Naghipour Department of Electrical and Systems Engineering Procedure Highlights Abstract Experiment Setup • Sensor selection criteria • Pressure range for running(2.5-76psi) • Sufficient accuracy(5%) • Corrosion and dust resistance • High sensitivity • Extremely thin & easy to adjust in shoes • Sensor position selection • There are 15 areas on the sole foot that support body weight but we select the heel and metatarsal areas to see if a person, favors HeelStrikeor Forefoot Strike. • Circuit Design • Design & develop an electronic interface circuit for the resistive sensors • Extract voltage signals from the sensors • Filter out the noise using a low pass filter at 15Hz. • As the frequency increases above 15Hz the gain decreases. 15Hz is the frequency of the steps, and anything above that is noise that need to be filtered. The attach shows that my experimental result matches my theoretical result. • The final design of the circuits ended up as an inverting low-pass amplifier with variable input resistance.Each of the FlexiForcepressure sensors in the insole are connected to a 2.2nf capacitor, a 5M resistor ,LM324N 𝑂𝑝 𝐴𝑚𝑝 and grounded though the connector. The -0.5 voltage is input to each of the sensors. • Data processing • Convert embedded analog to digital (A/D) using the Elvis board • Convert voltage to pressure using calibration • using multiple known masses to came up with voltage for given pressure then the system convert it to linear equation for easier analysis. • Convert the data to an array of numbers, record and sample data. • Data analysis • When the pressure increase the resistance of the sensors decrease and the voltage increase. The Voltage and pressure are proportional by a constant of k=0.040885. The In Shoe Pressure System project is a research effort to reduce running injuries and prevent FootStrike. Despite the money that has been dispensed into reducing running injuries by designing better shoes, the ideal way to reduce running injuries may be to simply work on foot posture finding a way to see the impact of the force and pressure in different parts of the foot while running. In Shoe Pressure Systemseems to be the very reasonable solution to prevent FootStrike. Overview • Goal: • To display the maximum pressure in different parts of foot while running and to inform the person if they run on their heels. • Approach: • Design a circuits to collect data output from sensors • Convert the data to pressure • Use the data to calculate peak pressure, mean pressure, center of pressure in both recorded and real time. • Application: • Footwear research for design • Compare, screen, and isolate food function • Identify pressure range for medical purposes and personal running regulation. Results Background Biomechanics of Running Heelstrike runners experience more running injuries such as hip injuries, IT band syndrome and hip bursitis. The Heelstrike runners land on their heel first so that the impact force of the heel on the ground causes significant transient force to their body via the skeletal system. Even though the heel is the hardest bone of the body, it does not absorb the impact force but it combines the gravitational forces and compresses them toward the skeleton. Daniel Lieberman, a researcher at Harvard University said: “Heelstrikecan cause a direct force of up to three times more than a runner’s body weight on the feet, ankles, knees and hips between 1000-1500 times per time.” Since MidFoot Strike is considered a preferred type of FootStrikeand we consider the HeellStrike as the worst case, Mid and Heel are the most important parts of foot that we consider in this research. Effects of running barefoot or with shoes in relation to foot strikes Barefoot runners are mostly front foot strikers when running. The heel cushions and arch supports within athletic shoes have made our feet weakerand adapted many people to favor HeelStrike. That is the reason that changing back to barefoot may cause injury to weakened feet. Three basic types of FootStrikes: Heelstrike(75%) Midfoot strike (24%) Toestrike(1%) Forefoot Heel Future Work • Develop a portable technology suitable for outdoor activities. • Add additional sensors to reduce the error and be more accurate Vout= -Vin()= -Vin(=-Vin Acknowledge I would like to thank Professor Morley for all of his help. I am so grateful to Professor Richter, who made this project possible . Many thanks to the Electrical Engineering Department at Washington University for their support . References Challenges Using Different Methods • Using accelerometer • Advantage: most smart phones have the application and no need to do any additional programing on the phone. • Disadvantage: the output is the peak force and there is no way of • seeing the comparison pressure range in different parts of the foot. • Using versatile Tekscan sensor • Advantage: It gives us a perfect picture of foot pressure • Disadvantage: High resolution requiring advance equipment and skill http://barefootrunning.fas.harvard.edu/4BiomechanicsofFootStrike.html http://www.livestrong.com/article/553745-the-impact-of-running-sneakers-on-the-foot/#ixzz1rPBjHyRI http://www.tekscan.com/medical/system-fscan1.html http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=05378500