MEASUREMENT OF ANKLE SUPINATION TORQUE

Submitted By: ASHOK KUMAR GUPTA

(07BMD012) MANISH KUMAR

(07BMD025) ROOPAM DEY (07BMD047)

Guide: CHAITANYA SRINIVAS L.V. ASSISTANT PROFESSOR BIO-MEDICAL DIVISION

Room No: 107, CBMR.

Place Of Work: VELLORE INSTITUTE OF TECHNOLOGY, VELLORE.

INTRODUCTION

The objective of this project was to calculate the Ankle Supination Torque by converting the pressure applied by the foot into electrical signal.

Ankle supination points the muscle weight of the body outside the foot and hence high arch of supination can cause Achilles tendonitis, Peroneal tendonitis, Ankle sprains.

Though there are clear symptoms of higher degree of ankle supination but there is hardly any signfor minor damage in an ankle leading to supination. Hence this project aims to be very simple and sensitive, the results can be used as a feedback system for training athletes.

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Fig 1 – Supination Posture of a foot

PREPARATION

The overview of this project was taken from the work done by the Chinese scientists Daniel Tik-Pui Fong et al[2].

The sensors used by us are Force Sensing Resistors (FSR), manufactured by Interlink Electronics. The work done by Indian scientist Dr. N.K. Rana of RGIT[1] helped us to work with the sensors.

A thorough study of FSR[4]was done that helped us to narrow down to a voltage-divider circuit using LM 324.

Introduction to Data AcQuisition[9] is the tutorial of National Instruments that gives the overview of the DAQ and its functions.

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The manual of National Instruments on Lab VIEW Analysis Concepts[8] gave us the basic idea of signal processing and analysis in Lab VIEW.

METHODOLOGY 3

Fig 2 – FSRs attached to the In-Sole Fig 3 – Voltage dividing circuit for a single FSR

Fig 4 – PIC Microcontroller CircuitFig 5 – The Visual Basic GUI Main Frame

3-PS SYSTEM

S-60 : Second/Third Distal Phalange S-72 : Third Metatarsalphalangeal JointS-98 : Fourth/Fifth Metatarsalphalangeal Joint

Sensor Locations :

SupT (Nm)= -2.068+0.00190827*e^0.01252 (1023-S60) +0.002763846 *e^0.01252 (1023-S72) + +0.003248253*e^ 0.01252(1023-S98)….1

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Fig 6 – Sole DivisionsFig 7 – Linear increase in the ADC output

with increase in output voltage. Fig 8 – Sensor Points

Fig 9 - FSR

FORCE SENSOR RESISTOR (FSR)Sensor Characteristics :

1. Resistance inversely proportional to applied pressure.2. Can withstand 1000N of force. Resistance stabilizes above this point.3. Gives a resistance of 0.25KΩ at 100N and 1.25KΩ at 10N.4. Size used 0.5” diameter model 402.5. Lifetime of the sensor is >10 million actuations.6. Temperature Range is -30°C to 170°C.

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Fig 10 – The Internal Structure of a FSR Fig 11 – Output Characteristics of FSR

VOLTAGE DIVIDER CIRCUIT 6

Vout = Vin * [1 / (1 + Rfsr / Rm ) ]

Fig 12 – (a)The theoretical design and (b) the practical output of Voltage Divider Circuit a b

To convert the pressure of the foot into voltage a voltage divider circuit was implemented. The above given formula was used.

5V was used as the Vin.

Fig 13 – (a) Outputs using different Rm values (b) Perfect linearity observed by using 8.2KΩ with Rfsr being 0.25KΩ.

a b

Rm is the resistor applied in series with the Rfsr to divide the input voltage. In this project 8.2KΩ was used as Rm.

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The output of the circuit was given to LM324, a linear quad-op amp that accepts PnP inputs, that reduces the noise of the converted signal.

PRACTICAL OUTPUT OF VOLTAGE DIVIDER CIRCUIT

Fig 14 – Output of the Voltage Divider Circuit

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Fig 15 – Graphical Output

DATA ACQUISITION KIT

Fig 16 – The interfacing of the Voltage Divider Circuit with the Data AcQuisition (DAQ).

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Main function of this block is to sample, analog to digital conversion and digital analog conversion.

The signal was sampled at 500 Hz and 1000 samples were taken that gave us one sample in 2 milliseconds.

WORK DONE IN Lab VIEW 10

Fig 15 – The Block Diagram designed in Lab VIEW to calculate and store the values of Ankle Supination Torque

Fig 16 – The VI designed in Lab VIEW to display the calculated values of Individual Sensors and Ankle Supination Torque

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Fig 17– Averaged Ankle Supination Torque sensed from 4 different subjects during normal walking and controlled supination walking

FINAL RESULTS

a b

c

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Fig 18 – Output of each sensors during supination walking and normal walking (a) S 60, (b) S72 and (c) S 98.

CONCLUSION

This work was successful in calculating the ankle supination torque in real time, while the subject walks

An increase in the ankle supination torque was observed when the subject walked in the controlled supinated way. The average specific increase being 158.6585 N-m

These values can be further used to find out the exact threshold of ankle supination torque that an ankle can withstand. This will help in safe training of the athletes.

In future a wireless devices can be made to calculate the supination torque which will be a boon to the sports world.

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PROBLEMS FACED 15

Availability of FSR with desired dimensions in low cost

To get the best sensitivity of the voltage divider circuit to get a linear output.

Status- Solved (Purchased the sensors from Chennai)

Status- Solved (Tried and tested the circuit with several resistors and incorporated 8.2K)

Implementation of hardware for calculating ankle supination torque by serial communication using microcontroller

Status- Partially solved in simulation.

REFERENCES[1] Application of Force Sensing Resistor (FSR) in Design of Pressure Scanning System for Plantar Pressure Measurement By: Dr. N. K. Rana, Department of Instrumentation Engineering, Rajiv Gandhi Institute of Technology[2] A three-pressure-sensor (3PS) system for monitoring ankle supination torque during sport motionsBy: Daniel Tik-Pui Fong, Yue-Yan Chan, Youlian Hong, Patrick Shu-Hang Yung, Kwai-Yau Fung, Kai-Ming Chan[3] LM 324 DatasheetBy- Phillips Electronics[4] FSR an Overview of the technologyBy- Tech Storm Inc[5] MAX 232 DatasheetBy- Texas Instruments[6] PIC 16F873 DatasheetBy- Microchip[7] 3-Terminal 1A Positive Voltage RegulatorBy- FAIRCHILD SEMICONDUCTORS

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[8] Lab VIEW Analysis and ConceptsBy- National Instruments[9] Introduction to Data AcquisitionBy- National Instruments

THANK YOU