Lower Limb Exoskeleton

An exoskeleton is a hard armor with joints, which covers completely or partially the body, whose objective is to recover mobility of the extremities (rehabilitation) or to improve the capabilities of the extremities themselves. During rehabilitation of the lower limbs, patients have problems to understand the gait cycle and to replicate it by themselves. The problem is that it is difficut for the patients to carry out this process consciously, since until then it has been done automatically. We, as biomedical engineering students, must apply technology to help in rehabilitation and fisiotherapy processes. Therefore, the main objective for this project is to create a scale exoskeleton to help people comprehend the gait cycle from the outside.

First of all, we were given the project specifications: 30 cm high, only MDF, use of Arduino, replicate (at the very most) the gate cycle, no 3D printing. Then, we made a draft on paper to have a picture of the exoskeleton, to which we added measurements in order to draw its 3D model in SolidWorks, and saved it in DXF format to be cut in the laser cutter.

Once the pieces were cut, we screwed some of the pieces to the servomotors to give movility to the exoskeleton, and the rest were glued with industrial glue. Finally, the servomotors were programmed with Arduino software to take specificic positions, with the purpose of replicating the gait as close to reality as possible.

Electronics:

• 6 servomotors
• Jumpers

Construction:

• 3 mm MDF
• 12 M4 lag screws (to secure servomotors on MDF)
• 12 M3 lag screws (to secure vanes on MDF)
• 6 M3 screws (to join vanes and servomotors)
• Screwdrivers
• Lime
• Drill
• M5 drill bits

Others

• Laser cutter

First of all, we brainstormed desing ideas, which are shown in the figures above.

Then, we complemented our drafts with measurements of the pieces (above pictures) to use them in the modeled parts.

Next, we used the SolidWorks software for the 3D design of the pieces (SLDPRT files). We also made the exoskeleton assembly (as shown in the previous image), where we used prisms to simulate the servomotors. Then, we cut triangles in the leg structure to reduce the wieght. This is not considered in the drafts of step 2, but appears in their corresponding file. All of the files can be found in the following links.

Later we cut the pieces with a laser cutter (first image): 4 times the "leg" file (second image), 2 times the "foot" file (third image) and one time the "hip" file (fourth image).

After that we adjusted only the leg piece introducing a hole for the screw on the top. We also had to add a space for the servomotor cable to fit in.

In the next step, we screwed the vanes to introduce the four legs, making sure that the hole in the middle top and the hole on the vanes lined up, which makes half of the leg. The images show both sides of the piece.

Following, we screwed a servomotor to each of the legs using the holes at the top to introduce the screws.

Lastly, we programmed the servomotors to move all at once in order to simulate the gait cycle.