1. Design and Fabrication of a
Controllable Knee for Above Knee
Amputees

2. SECTION – 01
• Introduction
• Objectives
• Project outline
• Methodology

3. Above Knee Amputation
• What is AKA ?
• Due to what ?
• What are the Solutions ?
....... AKAs in Sri Lankan.

4. Available Products and Facilities for AKAs
in Sri Lanka
• Jaipur Knee
• WalkRite Limited
• A J Medichem Major Prosthesis Importers
• International Health Care
• Dept. of prosthetic leg manufacturing, Ranaviru Sewana, Ragama
• July 7th to 23rd 2009 – Sri Lanka’s first mobile artificial limb clinic

5. Project Outline
Prototype
Develop Design
the Control
Capture System
Gait Data

6. Objectives
• Study the previous project.
• Less power consuming and a light weight
design.
• Reduce the electronic sensor requirement.
• Develop the communication between two legs
in real time.
• Design and fabricate the bionic leg.

7. Methodology
•Study the previous
Stage 02 •Apply the new
Stage 04 •Install the
project mimic mechanism prototype to an
•Computer aided •Develop a prototype
•Conduct a •Conduct a existing prosthetic
design of the knee •Check whether it can
literature survey simulation test leg in the market
•Selection of an acquire the required
actuation motion real time
Stage 01 mechanism
Stage 03 Stage 05

8. SECTION - 02
• Experimental Setup
– Motion capture for gait analysis via MATLAB
– Use of a mechanical sensors to measure the knee
joint angle
– MATLAB Simulink walking model
• Results analysis

9. Motion Capture to Gait Analysis
• Video recording
– Shutter speed- 1/25 s
– Aperture- f/4
– Frame rate- 24
• Upload to the Mat lab workspace

10. • Select the region where points hanging
• Segment the points
• Find the center of the segmented points
– SE = strel('disk', N)
– Threshold (0-1)

11. Result

12. MATLAB Simulations and Modelling
• Measuring the segment angle and displacement using gait
data.

13. Derive the equation of motion using
curve fitting
f(x) = a1*sin(b1*x+c1) + a2*sin(b2*x+c2) + a3*sin(b3*x+c3)
+ a4*sin(b4*x+c4) + a5*sin(b5*x+c5)
a1 = 2.92 (-664.5, 670.4)
b1 = 2.092 (-132, 136.2)
c1 = 0.587 (-56.2, 57.38)
a2 = 1.68 (-665.6, 668.9)
b2 = 3.097 (-176, 182.2)
c2 = 3.303 (-71.74, 78.34)
a3 = 0.2094 (0.09089, 0.3278)
b3 = 11.08 (3.52, 18.64)
c3 = 0.7017 (-1.986, 3.39)
a4 = 0.01324 (-0.1941, 0.2205)
b4 = 15.96 (-12.78, 44.69)
c4 = 1.76 (-11.69, 15.21)

14. Design the motion using MATLAB Simulink

15. Derive the torque at both knee during
walking

16. Use of QE to measure knee angle
• Encoder - HP HEDS 5500 C11
• CPR (counts per revolution) – 100
• Data acquisition software - C#.NET

17. Results
• Knee angle during level ground walking -

18. SECTION - 03
• Control System
• Prototype Design
• Specifications
• Further Improvements

19. Relationship between heel strike and toe strike of the real and
prosthetic leg -
• PLH = 1 - Prosthetic Leg Heel is on the ground
• PLT = 1 - Prosthetic Leg Toe is on the ground
• RLH = 1 - Real Leg Heel is on the ground
• RLT = 1 - Real Leg Toe is on the ground

21. Finite State Machine -

22. Factors to be Considered Prior to Design-

23. New approach to mechanical design of the leg and related factors -

26. Mobile Artificial Limb Clinic
• Held at - District General Hospital, Mannar, Sri Lanka.
During the project
period of 17 days
146 amputees were
assessed

27. Ranaviru Sewana