Body Sensor Networking, Design and Algorithms. Saeid Sanei. Читать онлайн. Newlib. NEWLIB.NET

Автор: Saeid Sanei
Издательство: John Wiley & Sons Limited
Серия:
Жанр произведения: Программы
Год издания: 0
isbn: 9781119390015
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M is mass, k is the spring constant of the frame-substrate springs. By driving the resonating mass at a known frequency, its changing displacement D induces a voltage from which the angular speed can be derived reasonably linearly. However, as with MEMS devices, the problems of drift, noise, and other artefacts remain. An IMU can be a combination of both accelerometers and gyroscopes (and a magnetometer in a 9D version) that measures rate, angle, and direction of motion. IMUs can be attached to any part of the body and are effectively used in gait analysis. Recent IMUs have built-in magnetometers as well that sense gravity and can be used in fall detection.

      3.2.3 Force Plates

      Force plates measure vertical ground reaction forces (GRFs) applied by gait during walking. A force platform can be integrated under the moving belt of a treadmill or under the entire treadmill [31]. Force platforms are expensive and have some limitations as the plates are installed within a short space and need to remain stationary. These make their applications in free space difficult. Nevertheless, there are force or pressure sensors that can be accommodated inside or under shoes to monitor the walking steps of humans or help correct the posture of athletes.

      3.2.4 Goniometer

      A goniometer is used to track the angle changes and is used for angle measurement in gait analysis since it is flexible and can rotate proportionally to the joint angle being measured [32]. It is particularly useful for the analysis of ranges of motion. Using a goniometer, it is possible to determine the range of knee joint angular movement to monitor patients with knee injuries. An optical fibre-based goniometer has been introduced in [33].

      3.2.5 Electromyography

      3.2.6 Sensing Fabric

      The goal in sensing fabric-based technology is the integration of sensors, communication components, and the processing elements into the fabric. The most common types are pressure sensors, including piezoelectric, piezoresistive, resistive, and capacitive sensors [35]. These sensors can be networked in a carpet to record the step pressure from both feet. In a more useful design, however, the pressure sensors and their associated electronics and wireless communication system, which does fit completely inside the shoe, is very demanding for the long-term monitoring and recordings of daily activities. Therefore, to make a valuable gait analysis platform, the sensing fabric technology has been directed towards the development of pressure-sensitive foot insoles with wireless communication capability [36].

      These sensors sense and capture the information emitted from the body inherently due to physiological or metabolic changes. These can be due to normal or abnormal human states. They can also be due to external effects such as viewing intriguing scenes, temperature change, and various physical activities.

      3.3.1 Multichannel Measurement of the Nerves Electric Potentials

Schematic illustration of a simple EEG differential amplifier used in EEG or EMG systems.

      ECG (also called EKG) is used to measure the electrical activity of the heart muscle nerves. The activity stems from pumping the blood through the right supraventricular down into the right ventricle and circling upward from the left ventricle to the left supraventricular and pumping into the arteries. Often 10–14 electrodes are used with reference to the arm, wrist or foot to capture the state of different heart sections.

      The systems for measuring electrical activity of the body don't involve any time delay and therefore processing of EEG, MEG, EMG, and ECG doesn't suffer any fading, clutter, or time overlapping of the signals. On the other hand, the effective frequency range falls below 500 Hz, which requires low processing power and bandwidth.

Photos depict (a) 


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