design of an apparatus to measure elbow...

Design of an Apparatus to Measure Elbow Spasticity

Team 5: Kevin Glick, Allison Heil, Michelle Cunanan

Clients: Dr. Steve Tippett & Dr. Elizabeth T. Hsiao-Wecksler

Advisor: Dr. Julie Reyer Course Coordinator: Dr. Martin Morris

Objective1. Demonstrate the ability to quantify elbow spasticity & rigidity

2. Provide sample data for an elbow spasticity simulator

Design & Analysis

Our prototype can be seen in the images below.

Left: FSR and flex sensor are mounted to a compression sleeve and

connected to the microprocessor (snowboard).

Right: Modified Snowforce interface provided by Kitronyx that

displays force in 2D and angular position output

Design Constraints:

Spasticity and rigidity can be characterized using position, torque,

velocity, and torque rate• Angular position limited to a range of 0° to 135°

• Angular velocity will be limited to a range of ±400 deg/s

• Angular acceleration limited to a range of ±2000deg/s²

• Torque limited to a range of ±10 Nm

Selected Sensor Package:• Spectra Symbol 4.5” Flex Sensor

• Resistance across the sensor increases as the

sensor is flexed

• Needs to be calibrated before each use

• Outputs angular position (degrees) to text file

• Sensitronics ThruMode Matrix Array• An array of 160 force sensing resistors (FSRs) that allows

the user to measure force over the 2”x 3” sensing area

• Calibrated with known masses

• Outputs resistance that can be converted to force via post

processing data analysis

• Kitronyx Snowboard• Arduino Leonardo with integrated force and touch sensing

controllers

• Access to Snowforce interface with editable Arduino and

Processing codes that are compatible with FSR array

Schematic:

Value to Client• Simulation Education: Data collected can be implemented into

a robotic elbow to stimulate elbow spasticity/rigidity.

Budget

Total Cost: $279.92

Project ProgressionGantt Chart

Deliverables• A working prototype measuring device

• A final report including a recommendation for sensors for a

future measuring device

• A database in Excel that holds all of the experimental data taken

with final prototype

Initial Concepts/Down-Selection Motion Capture Load Cell & Rotary Encoder

Torque Sensor

Accelerometer

Rotational Potentiometer

Inertial Measurement Unit (IMU)

AcknowledgementsBradley University Mechanical Engineering Department:

Dr. Julie Reyer Dr. Richard Johnson Gayle Dezner

Bradley University Physical Therapy Department:

Dr. Melissa Peterson Kristen Tetuan Sharon Key

Additional Acknowledgements:

Deepak Gaddipati James O’Connor

Carrie Liang Alex Ferrebee

Product Qty Total Cost

Kitronyx Snoboard with Sensor Package 1 $ 144.99

Spectra Symbol Flex Sensors 4 $ 45.58

Sensitronics Force Sensitive Resistor Matrix Arrays 2 $ 31.83

Hardware (Jumper Wires, Shift Registers, Multiplexers) N/A $ 57.50

Background• Elbow spasticity is a velocity-dependent stiffening of the

muscles that affects the motion in the elbow

• Rigidity is the stiffness or inflexibility present in both agonist

and antagonist muscles, and is characterized by the increased

resistance to passive movement.

• Currently measured using a

passive stretch-reflex test that

has limited sensitivity and is

highly subjective

• Current measurement analysis techniques are qualitative no

quantitative

Modified Ashworth Scale:

Recommendations• Develop a more user-friendly interface

• Use a higher quality sensor to collect position (i.e. fiber optic

goniometer or potentiometer)

• Complete HSRB process to conduct testing on actual patients• If testing actual patients, pay attention to dτ/dt (“jerk”)

• Perform in-situ measurements that is minimally invasive

• Pressure mapping system that can calculate a net pressure in specific

direction (i.e. Pressure Profile Systems Company)

• Create wire connections with more conductors than a 4 stranded wire

McGibbon, C. A., et al. "Elbow Spasticity during Passive Stretch-Reflex: Clinical Evaluation using

a Wearable Sensor System." Journal of NeuroEngineering and Rehabilitation 10.1

(2013)SCOPUS. Web. 23 Sep. 2014.