1. Ankle Injury Simulator Via Wobble Platform
Judd Terrell
Advisor: Kevin Robinson

2. General Design 30” x 30” variable support section
Section supported at all times by springs:
4 inch outer diameter
9 inch height
Spring constant: 14 lb/inch
Appr. 10 ft and 3 ft on front and back
$ total for springs
Very large spring; very low strength
Might drop cost of spring
Look for alternate methods of platform support
Advisor approved cost of springs, on order
Spring constant = Board weight / 4
Board weight = 55 lbs

3. Side Supports Wooden supports On all four sides
Support platform when weight is applied
Platform travel controlled by notch

4. Perturbing the System 1.5” drop = 3 shift Max. = 12 shift
Shift causes change in muscle contractions
Identify which muscles are important in recovering balance
30 inches * tan 3 = 1.5 inches
Max – Hobeika, Claude P. MD, “Ear, Nose, and Throat Journal” August 1999.
Perturb BoS forward -> Tibialis Anterior, Quadriceps, Abdominals
Perturb BoS backward -> Gastrocnemius, Biceps Femoris, Paraspinal muscles

5. Design for Variable Support
Solenoid-Bolt coupling
12VDC cylindrical solenoids
Controlled by voltage
5 position
rotary switch
Soleniod-bolt latch on each side
Position 1 – Right side latched, etc
Position 5 – All sides latched
Build 12V power supply as in 271 lab

6. Platform Construction
Wobble platform shown
Fully withstands excessive forces
Outer frame to be constructed when springs arrive
Weighs 55 pounds
Supports 400+ lbs standing
Supports 220+ lbs jumping
Reinforced edges to prevent splintering

7. Estimated Cost Item Total Hardware $114.18 Springs $155.68
12VDC solenoids
$40.45
Electronics
$18.31
$328.62
Springs from Diamond Wire Spring Co., Taylors, SC
Same price for 4 or 8 -> unusual requirements
Normal spring of this size = 100 lb/in

8. To do:
Build control circuit
Construct platform frame

9. References
Whittle, Michael W., Gait Analysis; An Introduction 2nd Edition, Butterworth – Heinemann 1996.
Hobeika, Claude P. MD, “Ear, Nose, and Throat Journal” August 1999.
Pai, Y. C., Patton J. L., “Center of Mass Velocity – Position Predictions for Balance Control” Journal of Biomechanics, 30(4): , 1997.