Group 15MaBeaN

Foot Pressure Monitoring System for a Speed Skater

1. Project Objectives2. Performance Specifications3. Design Details• Hardware:• Parts list• Construction

• Software• Information flow• Post-process flow

4. Results5. Assessment of Design

Performance6. Evaluation of Results

Presentation Outline7. Possibilities for further

improvement8. Division of labour9. Self Education – Andrew,

Ben, Matthew10. Schedule / Milestones11. 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

Project Objectives

Performance SpecificationsRequirement Target Reasoning

Sensor placement

8 FSRs per foot Allows reasonable spread of inputs to identify mass distribution over sole

Sampling frequency

40Hz sampling Gives average of 29 discrete steps per stride – sufficient to identify mass transitions within stride

Wireless fidelity Max 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.

Design Details - Components

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)

Design Details – Parts List

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.

Design Details – Part List

Design Details

Information Flowchart

Design Details

Serial.printlnTo Tx Xbee @ 38400 baud

MATLAB Function WriteCSV

COM Port Serial Buffer

@ 38400 baud

Arduino AnalogRead

(all 8 sensors)FSR

resistance

Recorded .csv file

Base Station Rx XBee

XBee packetization

and Tx

Software Flowchart (Post processing)

Design Details

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

Design Details

Results

Simulation pressure profile video◦ Compiled from

fictional .csv file◦ Uses MATLAB

griddata(‘v4’) function to smoothly interpolate between the eight sensor locations

Results – Software

Results

Results

Results

Assessment of Design Performance

Assessment of Design Performance

Evaluation of Results

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

Possibilities For Further Improvement

Division of Labour and Team Effectiveness

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

Self Education – Matthew McKerroll

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

Self Education - Ben York

Self Education – Andrew Yaworski

Schedule / MilestonesOverall Project Timeline

Schedule / MilestonesHardware Timeline

Schedule / MilestonesSoftware Timeline

Budget – Line Item ReviewCanakit Supplier Order

Item Description Unit Price Quantity Extended Price X-Bee Kit Xbee Wireless Kit 89.95 1 89.95

Arduino Uno Arduino Uno 29.95 1 29.95 SX00099 Real Time Clock Module 19.95 1 19.95

SX10088 Arduino Project Enclosure 12.67 1 12.67

SX00844Dual Axis Accelerometer Breakout Board -

ADXL2030 39.95 1 39.95 Subtotal 192.47 Tax 28.29 Freight 20.00 Total 240.76

TekScan Supplier Order (Force Sensitive Resistor)

ZFLEX(A201) 100-8 A201 Sensor @ 100 - 8 Pk 117.00 1 130.00 US Conversion 129.207 CAD(US*0.9939) Brokerage 12.5 GST 7.08535 148.79

The Source Order (Prototyping Silicon Board)

2760150 IC PC Board - Multi-purpose 417 6.99 1 6.99 Taxes 0.91 Total 7.90

Project Total 397.45Slack 2.55

Budget – Category Breakdown

Wireless Components Micro-controller Peripheral ComponentsSensors Taxes ShippingSlack

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 $10 000 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

Social, Environmental and Enterprise Context

Conclusions