TFG: Design and development of synchronization protocols for wireless EMG devices

Clock Synchronization

Electromyography is the technique used to check the health of muscles and the nerve cells that control them. Muscle data is normally collected through non-intrusive surface electrodes, which are placed on the skin. One of the problems that this technique has traditionally presented is the number of wires that are needed to connect the electrodes to the device that processes the information.

In the B105 Electronic Systems Lab there is a line of research focused on the development of a platform that removes these wires. The proposed solution is a platform with wireless sensors that allows the collection of EMG data.
The design and development of the synchronization and data transfer protocols are essential and will be covered in this project. This work is a fundamental piece along with the detection of EMG signals, the encapsulation of the device and the representation of the data to create a final wireless EMG product.

In this project the objective is to design and develop at least one synchronization protocol and one data transfer protocol that allow the specific activities of an EMG platform to be carried out. A previous study of the EMG technique, as well as the available hardware and software have been conducted. Subsequently, two synchronization protocols and one data transfer protocol have been designed and implemented.

Finally, tests have been carried out to evaluate the operation of the protocols, verifying that they work properly.

TFM: Design and implementation of a neuromuscular stimulator based on electromagnetic induction

In recent years, the development of medical devices has become a key element in order to face the research of new treatments and diagnosis of different diseases. These devices are designed to reduce the negative effects of some pathologies in which traditional pharmacologic treatments are not effective. An example of these pathologies are those that are produced due to a nervous system deterioration. Dysfunction of the human nervous system can be caused by situations such as a stroke or an accident in which the spinal cord is injured. This deterioration can lead to signal transmission disorders to the muscles, which are responsible for the movement of the body, and lead to muscle weakness or paralysis. The pathologies affecting the spinal cord, such as paraplegia, block communication between the central nervous system and the nerves, responsible for transmitting signals to the muscles. Therefore, these signals which are sent to the muscle from the brain can not be propagated, preventing the contraction and relaxation of muscles that give rise to movement. For all these reasons, different techniques of functional electrical stimulation (FES) have been developed and their use has been growing during these years. They are based on the concept of induction of the muscle contraction through the generation of electrical stimulus in the nerve. This technique produces skin damage and pain sensation. On the other hand, artificial stimulation by electromagnetic induction has been barely studied. Magnetic stimulation is based on the induction of a time-varying magnetic field that causes a current into the tissue and therefore, into the nerve. In this End of Master Project a prototype is designed to work on this less common technique.

Model of the generation and propagation of the signal that produces the muscle contraction.

This required a first stage of research on the state of the art in applying electromagnetic induction in neuromuscular stimulation techniques and understanding the main characteristics of the devices used in them. From this study, the advantages and disadvantages are established, and at the end, the characteristics to be considered in the design of the prototype. The prototype is based on a modular solution called modular multilevel converter, which allows to obtain the desired voltage and current to generate a time-varying magnetic field that induces the stimulating current in the nerve.

The device designed in this project is composed by a hardware part and by a software part. In the hardware part of this modular multilevel converter, the microtopology is established, based on the modules as a unit, and the macrotopology, based on the combination of the modules. The different modules and their components are implemented on a printed circuit board (PCB) that will serve as support and connection of the modules. The software part defines the control signals that allow each of the modules to define their working states, and therefore their contribution to the signal that generates the time-varying magnetic field. The designed software allows the modules to work in a synchronized relationship in the macrotopology of the system.

The results obtained on this project allows establishing some first conclusions about the use of modular multilvel converters focused on magnetic stimulation. The control signals of the modules are a great challenge for the implementation of a system composed of more modules than those presented in the prototype. In addition, the size of the system with a larger number of modules, necessary to cause an effective stimulation that leads to muscle contraction, must be considered in successive design iterations. This prototype establishes the first milestones towards the development of a platform that allows the magnetic stimulation of the motor nerves.

TFM: Design and implementation of a gateway node based on LTE mobile communications for a Wireless Sensor Network

Wireless Sensor Networks (WSN) research has recently become a key element in the Internet of Things (IoT) concept. These networks use autonomous devices, also known as nodes, whose purpose is to gather information from the environment and transmit it on the internet. We may classify these nodes into two categories: sensor nodes, which extract information from diverse environment parameters; and gateway nodes that transmit this information outside the network.

The main goal of this thesis is the development of a gateway node based in fourth generation mobile communications (4G). This gateway node has been developed both at hardware and software level and should be integrated in a wireless sensor network at future stages.

The hardware for this project is based in a previous design of a modular PCB developed at the B105 Electronic Systems Lab. Some modifications have been introduced in the original design in the power supply, RF and voltage shifter blocks in order to complete a functional prototype. The software architecture has been completely designed and implemented from the very beginning based on YetiOS – an embedded OS developed at the B105 Lab – including a specific API for the module and diverse connectivity functionalities such as call features and TCP/IP communication establishment.

Each hardware and software module has been tested separately and also operation of the whole node. In addition, system performance was evaluated measuring three parameters: consumption, latency and throughput, which are critical in the deployment of a practical application for the node.

The obtained results are discussed at the end of the document, comparing them to the original objectives and finally some working lines are proposed to continue with the node development.