Introduction: Spring in Your Step
My project is an elastically-assisted knee brace to help people with knee pain climb stairs and build strength in their legs. The brace was constructed using flexible anti-fatigue material to fit multiple leg sizes, and aluminum flat bar as a frame. Two hinges and pieces of aluminum flat bar were used to connect the support pieces. Heavy duty elastic bands were attached to the flat bar frame in the front of the brace to provide resistance to the eccentric motion of bending one’s leg. Results from mechanical testing show that the device is successful in self-extending following a forced contraction.
The brace can also be used during rehabilitation to help a patient bend their knee through resistance training. A patient can slip on the brace and practice bending their leg, opposing the resistance of the bands. The more the patient practices and is able to bend their leg against the resistance, the healthier their leg will become.
The brace also features an Arduino microcontroller with an angle sensor and digital display. This tracks and shows in real time how far the user is bending their leg in the brace, relative to the starting position. It doesn't track the exact angle measurement in degrees, but gives a value that increases the more a patient bends their leg. This is extremely useful for the rehabilitation aspect of the device, giving therapists the ability to quantitatively measure a patient's progress, as opposed to the traditional, subjective 1-10 pain scale. A patient can see if certain exercises and plans are improving their health if they increase the number they can achieve on the brace.
The angle sensor also has many future applications, including the possibility of a safety lock to prevent the brace from extending past a certain angle (to prevent hyperextension) and the automation of the leg motion through the use of a timer and servo motor wired into the Arduino and using data from the sensor.
Step 1: Step 1: Parts List
Heavy Duty Rubber Elastic Bands: 4
¾” Aluminum Flatbar: 46”
Velcro Strap: 2
Velcro Receiver: 2
Anti-Fatigue Material: 73 in3
Mae to Male wire
Step 2: Step 2: Building the Brace
1) Curve two pieces of aluminum flat bar around a PVC pipe.
2) Cut the curved pieces to a size that fits around the average human leg, slightly above and below the knee.
3) Cut non-curved flat bar into four connecting pieces that fill the gap between the hinge and the top and bottom of the brace.
4) Cut anti-fatigue material into two pieces, one that fits around the leg above the knee and one that fits around the leg below the knee.
5) Connect straight flat bar to fitted pieces of anti-fatigue material with rivets.
6) Take two hinges and drill four holes in each one.
7) Drill two holes in each curved flat bar piece
8) Put screws through holes in hinges and connect the two pieces of curved flat bar and the two anti-fatigue material components to the hinges.
9) Drill four holes in each curved piece of flat bar,
10) Attach four cut heavy-duty elastic bands to the curved flat bar pieces using screws.
11) Glue a piece of Velcro receiver to each anti-fatigue support piece using epoxy
12) Rivet a holder for the Velcro straps on the opposite side of the brace.
13) Thread the Velcro straps through the hook and connected them to the receivers.
Step 3: Step 3: Electronic Components
A breadboard and an Arduino microcontroller were glued onto the top support piece of the brace with epoxy. An angle sensor was attached to a small aluminum extension that was built off of one of the hinges The sensor was connected to the Arduino and the breadboard, then wired to a two-component digital display, giving numerical values proportional to the angle bend.
Step 4: Step 4: Arduino Code
Attached is the code that was used with the Arduino to display angle displacement.