Vítor Viegas

A virtual instrument to test smart transducer interface modules (stims)

This paper reports the hardware and software of virtual instruments and the tests conducted on a microcontroller-based smart transducer interface module (STIM) to check both STIMs performance and the suitability of a network capable application processor (NCAP) implemented in LabVIEW. The tests include the characterization of a digitizing channel of the STIM and the performance analysis of the system when the STIM simultaneously operates its digital outputs and its analog inputs.

A brief tutorial on the IEEE 1451.1 Standard - Part 13 in a series of tutorials in instrumentation and measurement

The 1451.1 standard addresses the definition of a network capable application processor (NCAP). The NCAP is a piece of hardware and software that acts as a bridge between transducers and the communication network. On the field side, an abstraction layer provides high-level functionality to communicate with transducers. On the network side, an abstraction layer provides high-level functionality to handle network requests. In the middle, the control routine adds intelligence to the NCAP by running algorithms that process the data received by both sides (the field and the network) and decide the next state of the system. The software architecture of the 1451.1 Std. is based on an information model, a data model, and two network communication models.The diversity of fieldbuses and network protocols leads a manufacturer to closed, less-flexible, and generally more-expensive solutions.

Toward developing a smart wheelchair for user physiological stress and physical activity monitoring

The article presents a smart wheelchair characterized by embedded sensors and an acquisition, processing and communication platform based on a multifunction I/O module and an embedded PC for monitoring of physiological stress parameters and motion activity of the wheelchair user in unobtrusive way. The embedded sensors include E-textile electrodes attached to the wheelchair arms and a 3D MEMS accelerometer used to extract the motion activity information. Additional sensing channels, expressed by piezoresistive flexible force sensors are used to optimize the measurement of contact ECG and skin conductivity. A server application, developed in LabVIEW and hosted on the embedded computer, delivers information about the digital processed signals to the client application installed in mobile platforms such as tablet PC or smartphones. The mobile platform provides interface for nurses, physiotherapists or physicians as well as for the wheelchair user or informal caregivers.

.NET Framework and Web Services: A Profit Combination to Implement and Enhance the IEEE 1451.1 Standard

In 1999, the 1451.1 standard, which defines a common object model and interface specification to develop open multivendor distributed measurement and control systems, was published. However, despite the well-known advantages of the model, there have been a few initiatives to implement a commercial version of the standard. In this paper, we describe the implementation of a network capable application processor (NCAP) in a well-known and well-proven infrastructure, i.e., the microsoft .NET framework. The use of a commercial framework increases productivity because it handles low-level programming details and provides good development tools, which allows us to produce a reusable and robust code. In addition, a solution to enhance the 1451.1 Standard is presented by proposing a new format for interNCAP communication based on eXtended Markup Language (XML) Web Services. This approach promotes interoperability because any device with a compatible Web Service middleware can locate and communicate with our prototype.

A low cost measurement system to extract kinematic parameters from walker devices

This paper presents a low cost measurement system that can be used to extract kinematic parameters from walker devices. The proposed measurement system can be easily integrated in any commercial non-smart walker device and includes mainly a set of six force sensing resistors and one 3D accelerometer, with the associated signal conditioning circuits, and the data acquisition and processing unit with wireless communication capabilities. The signals that are acquired from the sensors are used to obtain, in real time, the values of several variables related with strength, acceleration and tilt angles that are associated with the usage of walker devices. The proposed measurement system enables the detection of conditions that are related with a deficient usage of the walker device, such as, bad positioning of the walker legs during gait, amplitude and timing unbalances of the forces applied on the walker legs or on the walker hand grips, excessive values of mechanical oscillations or tilt angles of the walker device. Some calibration and experimental results are included in the paper.

Smart walker solutions for physical rehabilitation

In the last decade, the clinical reasoning in physical therapy has been to develop systems for physiotherapists to make clinical decisions rapidly, effectively and efficiently, in response to the increasingly complex needs of health and rehabilitation units [1]-[3]. Some studies show the importance of walking aids during rehabilitation from some diseases, and after surgery for arthroplasty in the elderly population [4], and in elderly patients with balance disorders, muscle weakness [5] or in people with diabetes mellitus [6]. Walkers are important devices that aid the rehabilitation process. The use of a walker is recommended for gait changes and imbalance due to various factors, such as surgery of the lower limbs or neurodegenerative changes, especially in the early recovery period [7].

IEEE 1451.1 Standard and XML Web Services: a Powerful Combination to Build Distributed Measurement and Control Systems

In 2005, we presented the NCAP/XML, a prototype of NCAP (network capable application processor) that runs under the .NET framework and makes available its functionality through a set of Web services using XML (extended Markup Language). Giving continuity to this project, it is time to explain how to use the NCAP/XML to build a distributed measurement and control system (DMCS) compliant with the 1451.1 std. This paper is divided in two main parts: in the first part, we present the new software architecture of NCAP/XML (which suffered some changes since the first version), and secondly, we describe the network configuration of a Web-enabled DMCS, which includes several NCAP/XML stations, a database and a Web server

Next Generation Application Processor Based on the IEEE 1451.1 Standard and Web Services

Over the last decade, the 1451.1 Std has been a reference model to develop smart and open distributed measurement and control systems. Now, that the 1451.1 Std is about to be revised, there is the opportunity to enrich it with emergent and successful technologies as is the case of Web services. Following this idea, we present a prototype of network capable application processor (NCAP) that runs on the .NET Framework and exposes its functionality through a set of Web services. The prototype takes advantage of three key technologies: (i) the abstraction layer proposed by the 1451.1 Std; (ii) the interoperability provided by Web Services; and (iii) the productivity supplied by the .NET Framework.

Advantages of PWM-A/D Conversion Techniques in Smart Sensing Systems

This paper dedicates a particular attention to pulse-width modulation (PWM) analog-to-digital ( A/D) conversion techniques underlining their importance in smart sensing systems. Nowadays, smart sensing systems and advanced signal processing techniques can improve measuring systems performance and flexibility relaxing hardware specifications and associated cost. The integration of sensing units, conditioning circuitry and A/D conversion is becoming trivial in a large number of instrumentation and measurement applications. In a large number of systems, linearization is generally required because most sensors have an intrinsic nonlinear characteristic or the presence of influence variables makes their characteristic nonlinear over its measuring range. Fortunately, digitalization and linearization can be performed in a single step nearby the transducer in smart sensing systems. A possible solution to achieve this goal is based on a PWM scheme for nonlinear A/D conversion. The proposed A/D conversion method is easily implemented in low-cost microcontrollers that generally include comparator inputs and PWM outputs. The input voltage range can be divided in several intervals and the nonlinearity profile of the A/D in each interval can be dynamically adapted if results from calibration or auto-calibration are available even when hysteresis effects are present. The paper includes some simulation results obtained with MATLAB and an experimental result of a strain gage system linearization is also presented in the final part of the paper.

Monitoring Walker Assistive Devices: A Novel Approach Based on Load Cells and Optical Distance Measurements

This paper presents a measurement system intended to monitor the usage of walker assistive devices. The goal is to guide the user in the correct use of the device in order to prevent risky situations and maximize comfort. Two risk indicators are defined: one related to force unbalance and the other related to motor incoordination. Force unbalance is measured by load cells attached to the walker legs, while motor incoordination is estimated by synchronizing force measurements with distance data provided by an optical sensor. The measurement system is equipped with a Bluetooth link that enables local supervision on a computer or tablet. Calibration and experimental results are included in the paper.