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.

TFM: DISEÑO DE UN SISTEMA DE MONITORIZACIÓN DE CONSTANTES VITALES DE ROEDORES A DISTANCIA
Posted on by rookie

The VISNE project, from the B105 Electronic Systems Lab at the ETSIT in collaboration with the Neuro-Computing and Neuro-Robotics group at the Complutense University, focuses on the development of a thalamic prosthesis to restore vision in humans. In its initial phases, this system will be tested on rodents, specifically mice, through behavioral tests in an operant conditioning chamber, also known as a Skinner box (as can be seen in the image below) .

However, the use of animals for medical research is one of the most controversial and debated topics in the modern scientific community. Therefore, ensuring the welfare of the animals has become a fundamental task, and to this end, the aim is to remotely monitor their vital signs.

In this master’s thesis, two techniques for monitoring mice were evaluated and tested: an infrared camera (MLX90640 from Melexis) for temperature measurement and an FMCW radar (AWR6843AOP from Texas Instruments) for tracking heart rate and respiration through thoracic variations. An electronic system was designed and implemented, consisting of two components: a proof-of-concept using both sensors and a prototype PCB that integrates the temperature monitoring system.

The proof of concept was integrated with a central interface within a Skinner box for mice. A user-friendly graphical interface was developed to display measurements from both sensors over time. A program was created using the infrared camera to detect the rodent’s warm body, positioning it at the central point to enable precise tracking and presence detection. The motion data collected could be used to estimate the rodent’s stress level during behavioral tests. Additionally, this program records temperature and movement data in text files for further analysis.

System tests demonstrated that the camera enabled continuous monitoring of the mouse’s body temperature, while the radar successfully measured heart rate in humans, with results closely aligning with those obtained through traditional methods. However, the radar measurements exhibited notable variability. Additionally, the system effectively measured the respiratory cycle and accurately detected presence.

The Printed Circuit Board (PCB) for the prototype temperature monitoring system was designed and manufactured with compact dimensions of 50 x 103 mm. It includes wireless connectivity and supports data storage on a microSD card. Additionally, the PCB is equipped with a micro-USB port for easy programming and powering of the system. All the TFM’s files are available in this repository: https://bitbucket.org/b105upm/tfm_rpeon/

The PCB has been successfully soldered, tested, and programmed. The embedded software enables data communication with a central node using the MQTT protocol, while the central server capture the data and displays thermal images on a web interface. All the embedded software of this system is located in this repository: https://bitbucket.org/b105upm/skinnerbox

TFG: Development of an evaluation device for wireless networks on the body
Posted on by fgarcia

B105 Electronic Systems Lab, of the Electronic Engineering Department, developed in the past several nodes called ‘Yetimote’, which work on the ISM frequencies of 433 MHz, 868 MHz and 2.4 GHz. During the last years, one of the main target’s laboratory has been the study of wireless networks over the human body (WBAN), composed by sensor nodes that are placed on different points of such human body to collect data for several purposes, usually for medical applications. However, the Yetimote node is addressed to use traditional wireless networks (WSN), due to its size and specific physical format.

The objective of this project was to adapt this node for evaluating and developing WBAN networks. To achieve this goal, one of the main printed circuit boards of the Yetimote node, called Cerberus, which is in fact the part in charge of carrying the wireless communications out, has been modified to make it more wearable.

On the other hand, the context of the project has been analyzed in more detail, describing WBAN networks in depth, the most common characteristics of these networks and their different usages. After a detailed analysis of the requirements to be fulfilled by the new board to be designed in the context of this work, a very deep study has been carried out about possible antennas to be used in this new solution. Finally, the specific choice of the antenna to be used in this work for each band was determined based on its characteristics. One of the electronic components which humans are more accustomed to is a wristwatch, so the PCB has been designed to be integrated inside an enclosure with this shape.

The next step was the electronic design and the PCB implementation of the new board called ‘Mini-Cerberus’, which has been designed using the Altium Designer tool. This new PCB will be connected to the rest of the Yetimote node through the board ‘Auxiliar’ which will be connected to the ‘Mini-Cerberus’ PCB through a flat cable. In addition, the ‘Mini-Cerberus’ board has several versions, one of them has a Pi-Network for each frequency band. Finally, the components were assembled using an industrial furnace and by manual welding. In the figure below, the previous ‘Cerberus’ PCB is shown in front of the new ‘Mini Cerberus’ prototype.

Additionally, some trials have been carried out in real environments to verify the correct operation of the developed design. Several tests have been performed in different real-world scenarios to study the performance of the new Mini-Cerberus board for different frequencies and transmission power values, and these results have been compared with those obtained for the original Cerberus board, which was used as reference or baseline.

In conclusion, it can be affirmed that the new ‘Mini-Cerberus’ PCB has a better performance in WBAN scenarios in the 433 MHz frequency band, while the 2,4 GHz frequency band has the worst performance of those studied. In relation to the Cerberus board, the new prototype has a lower performance compared to the original model, but this is an expected result due to the modifications made for its miniaturization

TFM: DESIGN AND IMPLEMENTATION OF AN ADAPTER FOR COMMUNICATIONS THROUGH COGNTIVE RADIO
Posted on by b105

This work is part of the ROBIM project in which the working group B105 Electronic Systems Lab of the University Universidad Politécnica de Madrid collaborates. The ROBIM project takes part in the program Programa Estratégico CIEN with the support of the CDTI (Centro para el desarrollo tecnológico Industrial) and the RDF (Regional Development Forum) for Europe.

The ROBIM project seeks to automate technical inspections of buildings, reducing costs and execution times associated with these processes. The system makes use of a drone for inspection work, thus avoiding the installation of scaffolding and all the security measures that the process requires, which is costly in time and money. Currently, the drone has a communication channel that allows users to obtain information on the process, as well as direct the drone whenever necessary.
The main objective of this work is to create a secondary, safe and effective communication channel, for situations where communication with the main system is not possible. To achieve this, the project stablish the following requierements:

– The device must allow radiocommunication in ISM bands.
– The device has an USB interface to connect with the computer/drone.
– The communication must be reliable by allowing communication throwgh various channels and implementing software-defined radio and cognitive radio.

Therefore, to achieve these objectives, this work proposes the design of a 2-channel device for radiocommunication in the 433 MHz and 868 MHz bands, using two SPIRIT1 transceivers and an ARM Cortex-M4 microcontroller.

Picture of the device’s high-level design

The Hardware design has been made usign the Altium Designer PCB design layout tool . The designed PCB is divided into three parts: the power/communication stage, the control stage with the microcontroller and the radiofrecuency stage with both SPIRIT1 trasnceivers.

Picture of the 3D reconstruction of the board designed in Altium Design tool

The software design has been developed in 2 stages: software design of an application for evaluation boards during the PCB manufacturating process and software design of a final application for the designed PCB.
For the software design of evaluation board, the NUCLEO – L053R8 with the X-NUCLEO-IDS01A4 radio frequency module has been chosen, which allows radio communication in the 868 MHz band. The final design of the software is based on the software of the evaluation board but improving its functionality by adding communication through two channels with a cognitive procedure based on the CSMA / CA protocol and implementing serial communication with the user.

The application designed for the device allows, then, a cognitive communication based on CSMA/CA protocol in bands 433 MHz and 868 MHz in addition to communication with the user and the drone enabling the possibility of the implementation of the second channel for the communication with the drone.

TFG: Design and development of a haptic device oriented to multimodal assisted perception for cases of low vision or blindness
Posted on by b105

In the past few years, technological developments have allowed the invention of aid systems for disabled people. Related to visual impairment, many of these systems have focused on achieving a correct guidance for these people.

There is an open research line in the B105 Electronics System Lab which is focused on this field. Specifically, its goal is to give more autonomy to blind people to move around cities, building interiors… To make this possible, a system provides acoustic and tactile information through sensory substitution. However, the user’s experience is limited because of these tactile stimuli are generated by a smartphone. Therefore, this branch of the research has a lot of room for improvement.

This graduate thesis is focused on the development and implementation of a device able to provide a better tactile experience with haptics stimuli based on the user’s movement.

To achieve this goal, this project has started doing an analysis of the most appropriate method of haptic simulation. Factors such as human physiology or the study of the actual haptics technology have been considered. Based on the chosen option, a printed circuit board (PCB) that allows motion capture and the desired stimulation has been designed.

Furthermore, some software tools have been developed to offer this haptic. This task is divided into two phases. The first part is the generation of the code that allows the management of the actuators and the reproduction of tactile effects. The second, is the construction of some tools to define the device’s orientation. A library for operating with quaternions and an application for obtaining the coordinates of a direction vector of the PCB have been elaborated.

Finally, the project concludes by making multiple tests on a development platform. The goal of these experiments is to verify the correct implementation of all the designed tools. The results show that it has been possible to support useful functionalities in research on sensory substitution. Some of these experiments are compiled on the following YouTube channel: https://www.youtube.com/channel/UCu0XuS97EoKVY_ilHYkemPg.