Fernando Gomes de Almeida

DigiScope — Unobtrusive collection and annotating of auscultations in real hospital environments

Digital stethoscopes are medical devices that can collect, store and sometimes transmit acoustic auscultation signals in a digital format. These can then be replayed, sent to a colleague for a second opinion, studied in detail after an auscultation, used for training or, as we envision it, can be used as a cheap powerful tool for screening cardiac pathologies. In this work, we present the design, development and deployment of a prototype for collecting and annotating auscultation signals within real hospital environments. Our main objective is not only pave the way for future unobtrusive systems for cardiac pathology screening, but more immediately we aim to create a repository of annotated auscultation signals for biomedical signal processing and machine learning research. The presented prototype revolves around a digital stethoscope that can stream the collected audio signal to a nearby tablet PC. Interaction with this system is based on two models: a data collection model adequate for the uncontrolled hospital environments of both emergency room and primary care, and a data annotation model for offline metadata input. A specific data model was created for the repository. The prototype has been deployed and is currently being tested in two Hospitals, one in Portugal and one in Brazil.

Acceleration‐based force‐impedance control of a six‐dof parallel manipulator

Purpose – This paper seeks to present an acceleration‐based force‐impedance controller, applied to a six‐dof parallel mini‐manipulator: the robotic controlled impedance device (RCID).Design/methodology/approach – The proposed control strategy involves three cascade controllers: an inner acceleration controller, built as a set of six single input/single output acceleration controllers (one per manipulator axis), an impedance task‐space controller, and an outer force controller.Findings – The control strategy enables two kinds of manipulator behaviour: force‐limited impedance control and position‐limited force control. The type of behaviour depends only on the chosen manipulator trajectories.Practical implications – The RCID may be used as a force‐impedance controlled auxiliary device, coupled in series with a position‐controlled commercial industrial robot. The two manipulators combined behave as a single manipulator, having the impedance and force control performance of the RCID, as well as the workspace ...

A macro–micro motion servopneumatic device

Micro motion tasks can be found in a wide set of applications, ranging from the assembly of small parts in the semiconductor industry to assisted surgery in medicine. Conventional actuation systems for these types of task are based on the existence of electromagnetic fields (servomotors) or on the existence of some kind of material shape alteration (piezoelectric actuators). Driven by the intrinsic advantages presented by pneumatic systems, such as low cost, the absence of heat or magnetic field generation and a wide range of operation, this article presents a different approach, based on the use of commonly available industrial servopneumatic components. Experimental results show that it is possible to correctly follow 5 µm step references within a 280 mm stroke, without any controller retuning and with mass load changes from 2.69 to 13.1 kg.

Impact of Laser-Based Technologies in the Energy-Consumption of Metal Cutters: Comparison between Commercially Available Systems

This paper introduces a framework for the Ecodesign of sheet metal cutters, which targets the definition of a set of design guidelines for this type of machine-tools, based on the contribution of the main equipment sub-systems to the processing and environmental impacts associated to their electrical energy consumption. A comparative study of commercially available Laser cutting equipments, using CO2 or doped fiber as the energy source, is described. Two parallel analysis of electricity consumption have been carried out: (1) the observation of CO2-Laser cutters usage, production modes and work conditions in real industrial environments, and (2) a comparison between these and a Fiber-Laser equipment, for a similar work order (material and thickness). The specific process energy with the different equipments was calculated, and confirms the importance of alternative technologies and practices for the energy efficiency of machining processes.

Undesired Oscillations in Pneumatic Systems

Automatic positioning devices are worldwide used in tasks like handling or assembly, making them key components of modern manufacturing systems. Pneumatic solutions are usually less expensive than their electrical counterparts, are more reliable and require less maintenance. However, the complex nonlinear nature and high model order of pneumatic systems lead to a very difficult control task. This paper illustrates these difficulties by presenting a study where several linear controllers are experimentally tested. In fact, despite their simplicity, these controllers can lead to undesired oscillations in the system output. The causes of these oscillations are described and justified in detail.

On the Influence of Velocity and Acceleration Estimators on a Servopneumatic System Behaviour

Pneumatic systems are clean and reliable actuators, presenting very high force to weight ratios. They further present some advantages, such as inherent compliance and suitability for fire hazard environments. However, their intrinsic nonlinearities have hindered a more wide range of applications, leading to the use of complex control laws that typically require the knowledge of velocity and acceleration. This means that the velocity and acceleration estimators might play a crucial role in servopneumatic systems control, since a difficult to achieve balance between differentiation noise and phase lag must be inferred by the control engineer. This paper experimentally compares the performance of several velocity and acceleration estimators, relying upon a digital encoder position signal. The comparison is performed not only regarding the quality of the actual estimates per se but also on their effect on the control error and control action obtained when using a nonlinear sliding mode-based controller.

LuGre Friction Model: Application to a Pneumatic Actuated System

Pneumatic systems offer a wide range of load capacity and velocities, present advantageous power to weight ratios and do not generate thermal or magnetic fields. However, their broader use in industry has been hindered by the difficulties found in fine motion or force control. Amongst the several phenomena that contribute to this scenario, friction in piston and rod seals is probably the most important one. Industrial pneumatic cylinders present friction forces with several undesired features for control purposes like highly nonlinear behavior, hysteresis and dwell time dependence.

Hypnotic administration for anesthesia using sliding-mode control

Nowadays general anesthesia is maintained using as the controller the human intervention, relying only on the quick and certain response of the anesthesiologist to the surrounding conditions, in order to provide the adequate state of anesthesia for the three main components - hypnosis, analgesia and paralysis. One of the most advantageous breakthroughs in anesthesia has been the appearance of depth of anesthesia monitors, assisting anesthesiologists in the hard job of knowing the hypnotic state of a patient. This information allows a way of closing the loop for administration of the hypnotic drug, and a more secure maintenance of hypnosis. The objective of this work was to apply sliding-mode control techniques to the model structure of the hypnotic in the human body (measured by the effect), and evaluate the robustness of this method to expected deviations from the average patient.

Quasi-static model of a thermal driven volumetric pump for an underwater glider

Underwater gliders enable an increase of human presence in the oceans. A particularly interesting solution lies in the use of the thermal gradient of the ocean as a means to provide energy to the vehicle. These type of gliders - thermal gliders - may remain years underwater collecting and transmitting data to seashore. A key element of these vehicles is the thermal driven volumetric pump that enables energy harvesting. In this paper a new quasi-static model of a thermal driven volumetric pump, for use in underwater gliders, is presented. The system considered includes a Phase Change Material (PCM) to convert thermal to mechanical energy and a hydraulic accumulator to store retrieved energy. The model allows the description of the quasi-static behaviour of the PCM coupled to the hydraulic system. The full thermodynamic cycle of the system can thus be simulated so that, in future works, the parameters of the system can be tuned for optimal performance.

The Ecodesign of Complex Electromechanical Systems: Prioritizing and Balancing Performance Fields, Contributors and Solutions

In the Product Development (PD) of complex mechanical and electromechanical systems, such as machine-tools, mapping the relationships between technical behavior, environmental and cost impacts brings new challenges. Having technological advances, cost drivers and environmental performance under surveillance, manufacturers and designers are expected to provide eco-efficient systems keeping a competitive price. This introduces a new set of design functions with increased complexity due to the new interdependent variables, requiring complementary technical, environmental and cost assessments. The redesign study of a sheet metal forming machine-tool, a press brake, is here used by the authors to present the first assessment of a proper methodology to support the main decision processes and to illustrate the technical and technological trade-offs faced by a PD team in order to achieve the global design objectives. The design process aimed to reduce the environmental footprint of the machine-tool and simultaneously to improve the bending process accuracy. A Voice of Customer (VOC) study was carried out in order to assess the receptiveness of press-brake users to the targeted product specifications and price changes sensitivity. The research effort was mainly focused in defining and testing the applicability of different assessment and measurement tools for the Ecodesign of a press-brake.