Mechanical exoskeletons are robots attached to the extremities of the human body, primarily focused on rehabilitation and enhancing strength, speed, and performance [1]. They consist of a structure connected to a series of actuators, sensors, controllers, and coupled viscoelastic elements. These devices primarily provide additional physical support, enabling patients to perform various tasks. Additionally, by smoothly integrating with the gait cycle, exoskeletons can improve the wearer's energy efficiency, providing assistance at critical moments to reduce fatigue and increase endurance during activity [2].

Therefore, the gait cycle is essential to the design and effective functionality of exoskeletons, as it provides a frame of reference to synchronize the movement of the device with the natural movements of the user during walking. This ensures that the exoskeleton offers adequate biomechanical support in each phase of the cycle, promoting a natural gait and reducing the load on joints and muscles [3].

By gathering all this data and aiming to demonstrate the significance of these devices nowadays, this project seeks to create a scaled prototype of a lower limb exoskeleton that closely replicates the gait cycle, with the main purpose of integrating different areas of knowledge into its development, primarily focusing on understanding the fundamental aspects of the gait cycle. This endeavor aims to apply diverse insights and expertise to the creation of the prototype.

References

[1] López, R., Aguilar, H., Salazar, S., Lozano, R., & Torres, J. A. (2014). Modelado y Control de un Exoesqueleto para la Rehabilitación de Extremidad Inferior con dos grados de libertad. Revista Iberoamericana de Automatica E Informatica Industrial, 11(3), 304–314

[2] Miranda, C., Juan, I., Morán, Gastón, M., & Francucci. (2021). Diseño y Fabricación de Exoesqueletos Ultralivianos. Proyecto Final de Grado Ingeniería en Materiales.

[3] Lugo, E., Ponce, P., Molina, A., & Castro, S. (2014). Co-simulación del Diseño Biomecánico para un Exoesqueleto Robótico del Miembro Inferior. Revista Mexicana de Ingeniería Biomédica, 35(2), 143–156.

Supplies

4 Servo Motors (2,2 Kgf/cm)
2 Servo Motors (10 Kgf/cm)
Arduino NANO
MDF 3mm
Dupont Jumpers
Power Supply
Resistors
Protoboard
Nails 5/8
Servomotor screws and holders
White glue

Step 1: Drafting

Before the final design of the project, it is very important to study the final product and have a very clear idea of what you want to achieve. Issues such as anatomy, biomechanics, and the gait cycle contribute to a good analysis of our prototype. In this way, a first draft was prepared, considering the joints involved and the materials to be used.

Step 2: Design

Once we were clear about how we wanted to make our prototype, we designed our draft in the CATIA app. The hips, legs and finally the feet were designed. All of these pieces were cut on MDF (3mm) using a laser cutting machine. The size of each of the servomotors was taken into account when making the design.

Note: The measurements shown on the plans are in mm.

Exoesqueleto.dxf
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Step 3: Assembly

When cutting the exact pieces for the exoskeleton, each of the servomotors were screwed, with the help of their supports, to each of the assigned joints (hip, knee and foot). In this case, it was previously verified that each of the servomotors worked properly.

The parts that were not screwed using servomotors were glued with white glue, this to have more support for the pieces.

Step 4: Programming

When programming this project, the Arduino application was used, in this case, it was chosen to use an Arduino NANO. The first thing to develop was a code that calibrated the six servomotors to 90°. After this, a new code was made so that each of the servomotors complied with the necessary angles to carry out the gait cycle.

MARCHA.ino
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Step 5: Result

Authors:

Thomen Roldán Sofia (cuarto semestre en Ingeniería Biomédica)¹, Zurita López Mercedes Guadalupe (cuarto semestre en Ingeniería Biomédica)¹, Moreno Hernández Ana (Profesor responsable)¹, Girón Nieto Huber (profesor asesor) ¹

1 Universidad Iberoamericana Puebla, San Andrés Cholula, Puebla, México