TFM: Design of a Communication System Through the Body
Posted on by rookie

The loss of a limb is a traumatic event for a human being, permanently altering the way they perform everyday tasks. Currently, most of these patients require a prosthesis for both aesthetic and functional reasons. Today, there are various types of prostheses, with robotic arms being the most commonly used for movement. These mechanical and/or electrical devices mimic human movements, controlled by the person. At present, the communication between the robotic arm and the user is established either through implants inside the body or via vulnerable communication methods.

The objective of this master’s thesis is to design a non-invasive communication system that uses the human body as a transmission medium. This approach is based on the innovative Human Body Communication (HBC) technology, which is part of Wireless Body Area Networks (WBAN). It is designed for wearable devices on the surface or inside the human body, specifically in the field of medicine. The goal is to transmit electrical or electromagnetic signals using the conductive properties of the human body.

To achieve this, an exhaustive study was conducted to understand how the human body behaves when a signal is transmitted at the selected frequency of 2.45 GHz. The signal will be transmitted through the patient’s forearm, which consists of multiple layers of materials with different dielectric properties. Therefore, computational simulations are necessary to analyze how the signal behaves.

This project is based on two experimental studies aimed at measuring propagation losses. The goal is to place the transmission and reception devices on the skin’s surface, using study [1] as a reference to calculate the signal losses through the multiple layers of the spleen. Additionally, the signal losses associated with transmission through the interior of the forearm, between the transmitter and receiver, were evaluated based on the data from study [2].

Once the system requirements were established, preliminary tests were conducted to validate the designed system. The results showed greater propagation losses than the theoretical estimates, prompting the project to focus on developing a functional prototype that is small, low-cost, and energy-efficient. The following image shows the completed system.

Finally, after testing the assembled system, it was determined that the selected insulator, RFSW-S-125-FR-PSA from Laird Technologies, is effective for communication through the air. However, aluminum yielded better results for communication through the body. On the other hand, the selected antenna was not ideal due to market limitations.

The results obtained suggest multiple areas for improvement and encourage further research to optimize the system.

References:

[1] Y. M. G. M. D. Zhi Ying Chen, «Propagation characteristics of electromagnetic wave on multiple tissue interfaces in wireless deep implant communication,» IET Microwaves, Antennas & Propagation, vol. 12, nº 13, pp. 2034-2040, 2018.

[2] C. G.-P. A. F.-L. A. V.-L. G. V. J. S. M. I. I. B. S. M. I. a. N. C. S. M. I. Ra´ul Ch´avez-Santiago, «Experimental Path Loss Models for In-Body Communications Within 2.36–2.5 GHz,» IEEE JOURNAL OF BIOMEDICAL AND HEALTH INFORMATICS, vol. 19, nº 3, pp. 930-937, 2015.

TFG:DESIGN AND DEVELOPMENT OF AN LOW-COST WIRELESS PROSTHETICS ARM
Posted on by b105

This final project focuses on the field of robotics aimed at developing automated prostheses, helping to recover part of the lost mobility of people who need it. More specifically, it will focus on analysing and designing a wirelessly controlled robotic arm, which will serve as the basis for future projects at the B105 Electronic Systems Lab.

To this end, a preliminary study was carried out of the technologies currently used to develop a robotic arm, extracting which components can be used to carry out the movement and control of the arm, what considerations must be taken into account to design the different parts that make it up and what prototypes currently exist, extracting their characteristics to try to find a way to improve them.

Once the previous study had been done, the design of the arm was carried out, where the way to control it, the type of wireless communication, the motorization to be used and how it is fed were chosen. After this, we have chosen the components that best suit to meet the specifications requested, the modeling program has been used to design the parts, the materials used to build them, and the type of manufacture used to make them. It has been concluded that the parts must be manufactured by 3D printing, that Bluetooth will be used as technology for wireless communication, and servomotors to motorize the system.

Afterwards, the connection has been made, the design of the pieces by means of a 3D modeling program and the subsequent manufacture of part of them by means of 3D printing. A mobile application has also been developed to control several servomotors and check the wireless connection between the arm and the mobile, in addition to having created several integration files on the board to check the operation of the components.

Then different tests have been carried out, using the software created, where different components have been connected, and it has been checked whether they work correctly or not.

In the end a complete functionality has not been achieved, but a partial functionality has been achieved where it has been possible to connect by means of Bluetooth the mobile and the arm, to move two servomotors, with which two fingers have been moved, and the battery has been controlled by means of a series of leds. Several problems have also been found with regard to the power supply of the servomotors and the reception of data sent by the board that controls the servomotors to the mobile.