Foot Pressure Monitoring System for a Speed Skater

1. Project Objectives 2. Performance Specifications 3. Design Details Hardware: Parts list Construction Software Information flow Post-process flow 4. Results 5. Assessment of Design Performance 6. Evaluation of Results 7. Possibilities for further improvement 8. Division of labour 9. Self Education – Andrew, Ben, Matthew 10. Schedule / Milestones 11. Budget Line Category analysis 12. Social, Environmental and Enterprise Context 13. Conclusions

 Improving a system to monitor foot pressure on the soles of speed skaters  Display pressure results alongside skater footage for use as a training tool to club level skaters  Ensure a minimum hindrance to the safety and performance of the speed skater  Skater stats (typical Kingston Striders skater)  Max velocity = 34km/h  Average stride duration = 720ms

RequirementTargetReasoning Sensor placement 8 FSRs per footAllows reasonable spread of inputs to identify mass distribution over sole Sampling frequency 40Hz samplingGives average of 29 discrete steps per stride – sufficient to identify mass transitions within stride Wireless fidelityMax range 60m; <3% Tx error Operation inside short track speed skating rink; Tx error limit corresponding to one sample packet lost per stride Compact transmission unit Minimize injury potential Consider Tx unit placement and size such that the skater is at no additional risk in a fall situation Minimally intrusive insole ~1mm thickness Low profile to maximize skater comfort, but must be robust to withstand mechanical strain inside skate Data visualization Max time drift 25ms Display data in contour map and bar graph alongside time matched skater footage.

 Arduino Uno – Micro-controller chosen for project, has 6 analog and 16 digital inputs  Xbee Chip – employed for wireless communication  WiFi Shield: Shield designed to extend the Arduino Uno providing wireless capabilities  Dual Axis accelerometer: to determine the initial start of a speed skater  RTC: real time clock to provide a clock time stamp  4051 Analog multiplexer: accepts the analog inputs of the force sensitive resistors  Resistors and holders: specific to each individual FSR; scaled to provide a scaled force output (components not to scale)

 Tekscan Force Sensitive Resistor (FSR) – used to evaluate the pressure exerted at a given point on the foot  Xbee base station chip: used to enable wireless capabilities of Arduino Uno  Base Station Shield: enables wireless Xbee chip to establish communication between a laptop and the Data Acquisition Pack.

 Information Flowchart Serial.println To Tx baud MATLAB Function WriteCSV COM Port Serial baud Arduino AnalogRead (all 8 sensors) FSR resistance Recorded.csv file Base Station Rx XBee XBee packetization and Tx

 Software Flowchart (Post processing) Draw sample and capture frame Extract sampling instance, interpolate values Input.csv file & skater footage Overlay pressure plot Produce final.avi file Align time index with skater footage Capture frame Loop

 Simulation pressure profile video ◦ Compiled from fictional.csv file ◦ Uses MATLAB griddata(‘v4’) function to smoothly interpolate between the eight sensor locations

 Employ the accelerometer for further data acquisition beyond the current application of a trigger to start sending data when a speed skater starts moving  Inclusion of a triple axis accelerometer to measure acceleration in 3 degrees of movement for turn analysis  Separation of scaled resistors to outside the DAQPAC for ease of exchange and to ensure the DAQPAC seals tightly  Use of a rechargeable lithium battery pack system for greater battery life while minimizing the environmental footprint of the unit  Further refinements to the placement and number of sensors in the foot sensor system for greater resolution

SegmentTaskAndrewBenMatthew ProjectFSR research ProjectPart sourcing5025 ProjectScheduling8010 ProjectLogistics4030 ProjectCommunication5025 Project Wikispaces Project website6020 ProjectProject Calendar Project Speed Skating Research33 34 ProjectOverall512524

SegmentTaskAndrewBenMatthew HardwarePart Selection HardwareSoldering75205 Hardware Wiring Diagramming HardwareTesting10000 HardwarePrototyping HardwareInsole Construction75205 HardwareOverall652312

SegmentTaskAndrewBenMatthew SoftwareMatlab Research Software Arduino Subroutine Development Software Matlab Data Acquisition01000 SoftwareMatlab Data Analysis01000 SoftwareVideo Input09010 SoftwareData Video Output01000 Software Video / Data Marriage08020 SoftwareOverall78111

 Digital and analog inputs work very differently, and both can be used for very different things  Much more can be extracted from resultant data then just pressures at given times, speed can be found as well as other things  A better understanding of circuits and how they interact with parts like processors and small IC’s

 Choosing the best visualization method  Colour blindness  Ease of interpretation for youth audience  Fail fast design  Build a prototype early, learn from it, then move on  Considering transient behaviour of ICs  When trying to maximize the sampling rate, components (i.e. MUX) do not behave instantaneously  Weekly meeting with supervisors  A source of unrivalled brainstorming and suggestions for improvement

 Micro-electronics are very approachable; the Arduino platform is a versatile platform to make use with an invaluable open source community  Soldering is an art that is a necessity when working with micro-electronics  The good news: Crazy glue is not conductive; the bad news: Crazy glue is not conductive.  Planning a design project requires more time than the actual project process itself; it is completely true that an engineer spends ½ of the time working, ¼ of the time writing reports and ¼ of the time presenting those reports to keep those involved updated with the current status  Project planning is a necessity. The amount of time spent planning at the beginning of the project is directly proportional to the success of the project and inversely proportional to the work required to complete the project.  Fail fast prototypes are integral to bypassing project bottlenecks

Canakit Supplier Order ItemDescriptionUnit PriceQuantityExtended Price X-Bee KitXbee Wireless Kit Arduino Uno SX00099Real Time Clock Module SX10088Arduino Project Enclosure SX00844 Dual Axis Accelerometer Breakout Board - ADXL Subtotal Tax28.29 Freight20.00 Total TekScan Supplier Order (Force Sensitive Resistor) ZFLEX(A201) 100-8A Pk US Conversion CAD(US*0.9939) Brokerage12.5 GST The Source Order (Prototyping Silicon Board) IC PC Board - Multi-purpose Taxes0.91 Total7.90 Project Total Slack2.55

 Analysis of the budget provides insight into the limitations due to component cost  FSR Sensors: 33%  Wireless Components: 22%  Peripheral Components: 20 %  Taxes / Shipping: 17%  Microcontroller: 7%

 The device made already exists but can cost more than $ dollars. The one made for this project is meant for the club level of skating – many uses, cost effective  Other applications of this project include heath-care and rehabilitation  This project has little to no environmental impact, but changes could be made so that it is more environmentally friendly

 From a cost perspective, the limitations of the current design project stem from the high initial cost of sensor equipment.  The least expensive component cost was in actuality the Arduino microcontroller.  The ease of connectivity resulting from the inclusion of the Wi-fi shield in conjunction with the Xbee has exceeded all expectations in terms of reliability, range, encryption and functionality and was worth the 22% budget allocation.  The pressure sensor system for a speed skater can be expanded to encompass varied practical applications that exceed the original application of monitoring foot pressure for a speed skater: ◦ Ergonomics analysis of repetitive and stressful working conditions ◦ Sport-specific analysis of the movements and pressures experienced during sports related activities ◦ Gait analysis that can aid in diagnosing possible issues relating to back problems resulting from bad posture or possibly misshapen feet that require orthotic support ◦ As a data collection unit that can be interfaced with any type of data acquisition system not necessarily that of a foot pressure monitoring system.  The unit is highly versatile due to the nature of the Arduino platform and is easily extended to other applications while being highly approachable in those disparate implementations.