An Evaluation of the Accuracy and Precision of Jump Height Measurements Using Different Technologies and Analytical Methods

This study aims to comprehensively assess the accuracy and precision of five different devices and by incorporating a variety of analytical approaches for measuring countermovement jump height: Qualisys motion system; Force platform; Ergojump; an Accelerometer, and self-made Abalakow jump belt. Twenty-seven male and female physical education students (23.5 ± 3.8 years; height 170 ± 9.1 cm and body mass 69.1 ± 11.4 kg) performed three countermovement jumps simultaneously measured using five devices. The 3D measured displacement obtained through the Qualisys device was considered in this study as the reference value. The best accuracy (difference from 3D measured displacement) and precision (standard deviation of differences) for countermovement jump measurement was found using the Abalakow jump belt (0.8 ± 14.7 mm); followed by the Force platform when employing a double integration method (1.5 ± 13.9 mm) and a flight-time method employed using Qualisys motion system data (6.1 ± 17.1 mm). The least accuracy was obtained for the Ergojump (−72.9 mm) employing its analytical tools and then for the accelerometer and Force platform using flight time approximations (−52.8 mm and −45.3 mm, respectively). The worst precision (±122.7 mm) was obtained through double integration of accelerometer acceleration data. This study demonstrated that jump height measurement accuracy is both device and analytical-approach-dependent and that accuracy and precision in jump height measurement are achievable with simple, inexpensive equipment such as the Abalakow jump belt.

Comparative study of theoretical and real deflection of a simple and reinforced concret joist

This research aims to determine the actual deflection of a concrete joist and to correlate the result with the theoretical deflection. This is based on the theories of elasticity as the double integration method, considering the homogeneous, isotropic and linearly elastic material from an ideal theoretical model. The construction of a concrete joist does not make a 100% homogeneous, isotropic and linearly elastic element, since its manufacture depends on many conditions such as the choice of aggregates, water, the manufacture of cement, tests carried out for the elaboration of the mix design, the operator who is going to perform the mix and the construction of the joist. The variation of the real deflection with respect to the theoretical one has been investigated. For this, 30 simple concrete joists and 30 reinforced concrete joists were manufactured. The dimensions of these joists were 15cm x15cmx53.5cm (b x h x L). The reinforcement of the last 30 joists was 4 Փ 1/4 "as longitudinal reinforcement and Փ 1/4" @ 0.10 m of transverse reinforcement. The joists were tested for flexion by measuring the maximum deflection and compared with the theoretical one, calculated by the double integration method, having much greater experimental results than those calculated with the theory of the double integration method, not being within the ranges expected in literature

Mathematical model of functioning of multisensor converter of binary mechanical signals in electric on the basis of fiber-optic digital-to-analog converter

The design and operation principle of a multisensor converter of binary mechanical signals into electrical signals consisting of a fiber-optic digital-analog converter, a photo amplifier and a voltage-to-code converter with double integration are considered. A generalized mathematical model of multisensor converter functioning has been developed, which combines particular mathematical models of fiber-optic digital-to-analog converter, photo-amplifier and voltage-to-code converter with double integration. The mathematical model of functioning of the multisensor converter in the form of analytical expressions for definition of the output electric code depending on values of bit digits of the input mechanical code taking into account a complex of constructive, circuit and power parameters of the converter is developed. The analytical description of the signal in the frequency converter in code, using which an algorithm is developed for numerical analysis of mathematical models of the functioning of the devices under study, providing the maximum permissible values of the instrumental errors of manufacture of the transducer elements in which is implemented the complete accuracy of the device. The presented results can be used for the development of multisensor converters of binary displacements of control systems, control and monitoring of energy-saturated objects, for which high noise immunity, electrical neutrality, low chemical activity and information security are of paramount importance.

Estimation of Displacement for Internet of Things Applications with Kalman Filter

In the vision of the Internet of Things, an object embedded in the physical world is recognizable and becomes smart by communicating data about itself and by accessing aggregate information from other devices. One of the most useful types of information for interactions among objects regards their movement. Mobile devices can infer their position by exploiting an embedded accelerometer. However, the double integration of the acceleration may not guarantee a reliable estimation of the displacement of the device (i.e., the difference in the new location). In fact, noise and measurement errors dramatically affect the assessment. This paper investigates the benefits and drawbacks of the use of the Kalman filter as a correction technique to achieve more precise estimation of displacement. The approach is evaluated with two accelerometers embedded in commercial devices: A smartphone and a sensor platform. The results show that the technique based on the Kalman filter dramatically reduces the percentage error, in comparison to the assessment made by double integration of the acceleration data; in particular, the precision is improved by up to 72%. At the same time, the computational overhead due to the Kalman filter can be assumed to be negligible in almost all application scenarios.