Browsing by Author "Viegas, Vitor"
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- Application of force and inertial sensors to monitor gait on legacy walkersPublication . Viegas, Vitor; Pereira, José Miguel Costa Dias; Postolache, Octavian; Girão, Pedro SilvaWalker assistive devices play an important role in extending the autonomy of elderly people and in recovering the mobility of people affected by locomotion disabilities. The next generation of walkers are hoped to include embedded sensors and data processing capabilities that will allow for the extraction of objective metrics (about gait and body posture) to assist the work of physiotherapists and to enable the self-control nature of walker usage. The paper presents the Andante, our latest proposal of a smart walker intended to monitor and analyze gait in real time. The system makes use of e-textile electrodes to sense the heart rate of the user, load cells to measure the forces applied on the walker legs, and an inertial measurement unit to sense motion and orientation. These signals are sampled locally and transferred over a Bluetooth link to a remote host, where they are processed in real time. Data processing includes the detection, classification, and characterization of the steps. A rich set of parameters is presented for each step, including estimates of balance and motor coordination, step length and azimuth, and lift of the walker frame. This information can be used by physiotherapist to objectively assess the physical condition of the user and tune rehabilitation therapy if needed. The proposed solution can be easily integrated into any commercial walker without any loss of functionality.
- Digital to analog converter based on pulse-width addingPublication . Viegas, Vitor; Pereira, J. M. DiasThis paper presents a digital-to-analog converter(DAC) based on the pulse width created naturally by the binary counting sequence. Theconcept involves combining the counting impulses of the bits to forma pulse-width modulated signal,where the mean voltage is proportional to the input digital code. We propose a circuit capable of achieving this using general purpose components. Although our design targets 8bits, it is scalable for any number of nibbles. The paper details simulations conducted to verify the proper functioning of the circuit and to evaluate its performance.Tests were performed to determine the static characteristics of the converter, measure its differentia nonlinearity(DNL),and observe its step response. Instaticterms,theconverterexhibitednegligiblegainandoffseterrors,withaDNLbelow1LSB(least significant bit).The converter operated correctly without any missing codes. In dynamic terms,the converter demonstrated a band width of 10kHzand behaved like a second-orderlow-pass filter with critical damping.
- A dual-proposal device for condition-based maintenance and energy harvesting in the context of IIoT applicationsPublication . Pereira, José Dias; Viegas, Vitor; Postolache, Octavian; Girão, Pedro SilvaThis paper presents a dual-purpose device for condition-based maintenance (CBM) and for energy harvesting (EH) in IIoT applications. Vibration monitoring in industrial environments is a key indicator for predictive maintenance purposes and for energy harvesting. The paper includes the description of the hardware and software of a flexible platform that permits vibration measurements, vibration sensor calibration and energy harvesting testing. The vibration exciter included in the platform can be controlled by the output signal of a common signal generator. The platform also includes a differential temperature sensor that can gather additional data for CBM purposes. The final part of the paper includes experimental results of a vibration sensor under characterization and of the performance evaluation of a commercial EH module.
- Service extensions for Instrumentation (SXI)Publication . Viegas, Vitor; Girão, Pedro Silva; Pereira, José Miguel Costa Dias