Motorised Exoeskeleton

The human gait is one of the most complex movements the body is capable of performing, being possible thanks to many systems working together.

An analysis of a person’s gait can provide a lot of information, especially because the way a person walks can be affected by extrinsic and intrinsic factors; in healthcare, an abnormal gait can be indicative of a disease or an injury. [1]  

Healthcare professionals use the data obtained in a gait analysis to determine what type of treatment a patient with a pathological gait may need; today, there’s a lot of options, one of which are exoskeletons, both for rehabilitation and for aiding in mobility. 

Exoskeletons are machines made to be worn by the user equipped with motorized joints to simulate the natural movements of the body. This technology provides support with posture, weight distribution and even help with injuries and disabilities [2].

In the present, an excellent example of the use of exoskeletons used for rehabilitation purposes, is the Robotic Assisted Gait Training (RAGT). This technology is used in patients suffering from neurological injuries, spinal cord injuries, cerebral palsy, multiple sclerosis, to mention a few, all of these disabilities have in common the loss of movement in the inferior extremities, to provide stability, security and speed up the process of rehabilitation. [3]  

Knowing what we know, is more than obvious how the understanding and development of aids that can simulate the gait-like movement is of paramount importance. The present project proposes a design of an exoskeleton capable of reproducing the human gait. MDF will be used to ensemble the exoskeleton, while MG995 motors controlled with Arduino UNO will provide the mobility. In the spirit of spreading knowledge, all the necessary documents and instructions necessary for the project to be replicated will be uploaded to the internet and will be available free of charge. 

For this project you will use:

• MDF (thickness: 3mm)
• 6 MG995 servomotors
• Arduino Uno
• Protoboard
• Power supply
• 9 volts batteries
• Jumper wires
• Resistors
• Servomotor screws and holders
• Kola loka glue (or any instant glue)

The robot will emulate the inferior part of the human body, so it's pieces are to be understood as the hip, the legs and the feet (all parts included below).

The whole robot is aproximately 20 cm in height accouting for the servomotors size and the space used between pieces.

All files are to be cut once, except for the one titled columns.dxf that one has to be cut three times.

NOTE: The software used to model the pieces was CATIA, but the platform Instructables does not support the extension (.CATPart), so the (.dxf) files were uploaded (these extensions is the one you'll use to cut the MDF), nevertheless a link with the (.CATPart) files is included (CATPart). Photos are available so you know how they'll look once put together.

First off, we have to make sure the selected servomotors work properly, for this you can connect the motor to an Arduino and a power supply to test them by running the program shown in the second image. This will make the motor move from 0° to 180° and you'll know if they are functional. Note that the motors work with 5V.

To build the exoeskeleton, you must first, attach the servomotors to the MDF parts (hip, knee, foot). Once the motors are in place, from top to bottom you must screw together the bridge and the hips; the knees and the hips are going to be attached by the colums, these function as axis so it can allow a smooth rotation; finally, the foot is attached to the knee using the foot link. Once everything is attached together Arduino is used so the programming part allows movement on the servomotors. Please check out the pictures provided in order to see the whole construction and how all the parts were attached together.

Please refer to images two to four for deatils on how to assemble exactly the motors on the pieces.

An Arduino is a powerful tool when it comes to creating electronic projects. Thanks to the multiple libraries, the relatively easy use and the many programmable pins, Arduino is a favourite among amateurs and professionals in the various areas of engineering.

For this part of the project a basic knowledge of programming in Arduino is advised.

You'll need to have the Arduino IDE installed in your computer to proceed (if you dont you cann download it here: https://docs.arduino.cc/software/ide-v1).

As a reminder, the basic connection for all servomotor is shown in the second picture, but of course more than one can be connected to the Arduino, always taking into consideracion common ground, as shown in the third picture.

NOTE: Do NOT attempt to energize the servomotors using a computer, they use way too much resources and the computer could be damaged.

Program