Introduction: 4KARE (Knee Joint Exoskeleton)
The knee joint is one of the strongest and most important joints in the human body. It allows the lower leg to move relative to the thigh while supporting the body’s weight. Movements at the knee joint are essential to many everyday activities, including walking, running, sitting and standing.
The product is completely a pure mechanical structure designed to reduce the load on knee joint. The main purpose/ problem which our idea will solve is that it will transfer partial amount of force from the upper leg i.e. thigh to the lower leg i.e. shin through an external structure mounted on leg Thus the force/load on knee is reduced.
The external structure is made up of four bar mechanism and the benefits of using four bar mechanism are-
I. Gives combination of rotational plus translational motion i.e. it exactly traces the complex motion of the knee
II. Follow trajectory of knee curve (J-curve) i.e. it exactly traces the motion of the leg.
Step 1: 4 Bar Mechanism Check
The working of the four bar mechanism was checked by making a wooden model and by tying on the leg. The motion was thus verified by stretching, walking and running.
Step 2: Scaling, Dimesioning & Sketching
the dimensions of the link for scale 1.0, 0.9,0.8, 0.7 & 0.6 were calculated and the exterior structure of the four bar mechanism was cut on a cardboard for each scaling. It was then tied on the leg with the help of the thread as shown in the figure.
The number of clamping required to properly transfer the load and to prevent it from getting loose and sliding down were then decided. Clamping is very important when it comes to hold the product tight with the leg. After doing a research on the type of clamping with the help of Velcro and the number of clamping, we finally decided to go with three clamping on the thigh part of the exoskeleton and two clamping for Shin part.
A circle is marked covering the entire patella.Taking the midpoint of the circle marking were done on each side of the knee. The height of the top and bottom edges depends on a person’s height. This exoskeleton has been designed for a person of height 6’16”. A length of 3.5” were marked on the thigh and shin. Top most and bottom most edges for the structures were marked at a height of 8.5” on the thigh and 6.5” on the shin. We than had 5” on the thigh and 3” on the shin for clamping the exoskeleton.
The rough sketch was then prepared in order to imagine a picture of the targeted product.
Step 3: Modelling
Taking the original dimensions of the leg the product was then modelled in Fusion 360.
Step 4: Simulation and Shape Optimization
The 3D model was then simulated and its shape was the optimised by applying load on the required points and the final design was obtained.
Step 5: Final Design and Assembly
Step 6: Prototype
The Prototype has been made through 3D printing in ABS plastic.
Step 7: Testing Video of Prototype 1.0
The Video of the testing was recorded with first Prototype(1.0) of the product but the Images of the prototype shown in the previous steps are of the second prototype(2.0)
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