Foot Pressure Monitoring System for a Speed

safflowerpepperoniMobile - Wireless

Nov 24, 2013 (3 years and 8 months ago)

118 views

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


Requirement

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
25
ms


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 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)




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




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


Canakit

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



SX00844

Dual 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

397.45

Slack

2.55

Wireless Components
Micro-controller
Peripheral Components
Sensors
Taxes
Shipping
Slack

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