Local Positioning Systems in (Game) Sports

Position data of players and athletes are widely used in sports performance analysis for measuring the amounts of physical activities as well as for tactical assessments in game sports. However, positioning sensing systems are applied in sports as tools to gain objective information of sports behavior rather than as components of intelligent spaces (IS). The paper outlines the idea of IS for the sports context with special focus to game sports and how intelligent sports feedback systems can benefit from IS. Henceforth, the most common location sensing techniques used in sports and their practical application are reviewed, as location is among the most important enabling techniques for IS. Furthermore, the article exemplifies the idea of IS in sports on two applications

Inertial Sensor-Based Motion Tracking in Football with Movement Intensity Quantification

Inertial sensor-based measurements of lower body kinematics in football players may improve physical load estimates during training sessions and matches. However, the validity of inertial-based motion analysis systems is specific to both the type of movement and the intensity at which movements are executed. Importantly, such a system should be relatively simple, so it can easily be used in daily practice. This paper introduces an easy-to-use inertial-based motion analysis system and evaluates its validity using an optoelectronic motion analysis system as a gold standard. The system was validated in 11 football players for six different football specific movements that were executed at low, medium, and maximal intensity. Across all movements and intensities, the root mean square differences (means ± SD) for knee and hip flexion/extension angles were 5.3° ± 3.4° and 8.0° ± 3.5°, respectively, illustrating good validity with the gold standard. In addition, mean absolute flexion/extension angular velocities significantly differed between the three movement intensities. These results show the potential to use the inertial based motion analysis system in football practice to obtain lower body kinematics and to quantify movement intensity, which both may improve currently used physical load estimates of the players

Spatial Data Performance Test of Mid-cost UAS with Direct Georeferencing

Recent development of lightweight and small size multi-frequency GNSS receivers allows determination of the precise position of the moving platform and spatial data acquisition without the need for setting up and measuring of ground control points. The main advantage of this approach is a higher operational capacity with reduced time and cost of field measurement. This relates to fieldwork in inaccessible areas with demanding terrain configuration. In this paper development and use of a UAS with direct georeferencing of camera sensor for spatial data acquisition is described, and the possibility of 3D scene reconstruction based on the precise position of the camera with predetermined interior parameters is examined. Modern computer vision-based SfM photogrammetry algorithms are used for determining attitude parameters and reconstruction of the scene. For that purpose, several tests on two different test fields were performed using various system parameters for collecting and analysis of several spatial data sets. The presented results demonstrate a satisfactory accuracy (3.1 cm planar and 6.4 cm spatial) of the system for various applications in geodesy

MICROCANTILEVER-BASED FORCE SENSING, CONTROL AND IMAGING

This dissertation presents a distributed-parameters base modeling framework for microcantilever (MC)-based force sensing and control with applications to nanomanipulation and imaging. Due to the widespread applications of MCs in nanoscale force sensing or atomic force microscopy with nano-Newton to pico-Newton force measurement requirements, precise modeling of the involved MCs is essential. Along this line, a distributed-parameters modeling framework is proposed which is followed by a modified robust controller with perturbation estimation to target the problem of delay in nanoscale imaging and manipulation. It is shown that the proposed nonlinear model-based controller can stabilize such nanomanipulation process in a very short time compared to available conventional methods. Such modeling and control development could pave the pathway towards MC-based manipulation and positioning. The first application of the MC-based (a piezoresistive MC) force sensors in this dissertation includes MC-based mass sensing with applications to biological species detection. MC-based sensing has recently attracted extensive interest in many chemical and biological applications due to its sensitivity, extreme applicability and low cost. By measuring the stiffness of MCs experimentally, the effect of adsorption of target molecules can be quantified. To measure MC\u27s stiffness, an in-house nanoscale force sensing setup is designed and fabricated which utilizes a piezoresistive MC to measure the force acting on the MC\u27s tip with nano-Newton resolution. In the second application, the proposed MC-based force sensor is utilized to achieve a fast-scan laser-free Atomic Force Microscopy (AFM). Tracking control of piezoelectric actuators in various applications including scanning probe microscopes is limited by sudden step discontinuities within time-varying continuous trajectories. For this, a switching control strategy is proposed for effective tracking of such discontinuous trajectories. A new spiral path planning is also proposed here which improves scanning rate of the AFM. Implementation of the proposed modeling and controller in a laser-free AFM setup yields high quality image of surfaces with stepped topographies at frequencies up to 30 Hz. As the last application of the MC-based force sensors, a nanomanipulator named here MM3A® is utilized for nanomanipulation purposes. The area of control and manipulation at the nanoscale has recently received widespread attention in different technologies such as fabricating electronic chipsets, testing and assembly of MEMS and NEMS, micro-injection and manipulation of chromosomes and genes. To overcome the lack of position sensor on this particular manipulator, a fused vision force feedback robust controller is proposed. The effects of utilization of the image and force feedbacks are individually discussed and analyzed for use in the developed fused vision force feedback control framework in order to achieve ultra precise positioning and optimal performance

Modeling and Control of Flexible Link Manipulators

Autonomous maritime navigation and offshore operations have gained wide attention with the aim of reducing operational costs and increasing reliability and safety. Offshore operations, such as wind farm inspection, sea farm cleaning, and ship mooring, could be carried out autonomously or semi-autonomously by mounting one or more long-reach robots on the ship/vessel. In addition to offshore applications, long-reach manipulators can be used in many other engineering applications such as construction automation, aerospace industry, and space research. Some applications require the design of long and slender mechanical structures, which possess some degrees of flexibility and deflections because of the material used and the length of the links. The link elasticity causes deflection leading to problems in precise position control of the end-effector. So, it is necessary to compensate for the deflection of the long-reach arm to fully utilize the long-reach lightweight flexible manipulators. This thesis aims at presenting a unified understanding of modeling, control, and application of long-reach flexible manipulators. State-of-the-art dynamic modeling techniques and control schemes of the flexible link manipulators (FLMs) are discussed along with their merits, limitations, and challenges. The kinematics and dynamics of a planar multi-link flexible manipulator are presented. The effects of robot configuration and payload on the mode shapes and eigenfrequencies of the flexible links are discussed. A method to estimate and compensate for the static deflection of the multi-link flexible manipulators under gravity is proposed and experimentally validated. The redundant degree of freedom of the planar multi-link flexible manipulator is exploited to minimize vibrations. The application of a long-reach arm in autonomous mooring operation based on sensor fusion using camera and light detection and ranging (LiDAR) data is proposed.publishedVersio

Bluff-body aerodynamics and transfer functions for non-catching precipitation measurement instruments.

Starting from the old and trivial technique of using a graduated cylinder to collect and manually measure precipitation, numerous advances were made for in-situ precipitation gauges. After decades of scarce innovation, a new family of in-situ precipitation gauges was developed. They are called Non-Catching Gauges (NCG) since they can measure precipitation and its microphysical and dynamic characteristics without the need to collect hydrometeors. The attention that NCGs are gathering today is quite notable, even if they represent only a small fraction of the total precipitation gauges deployed. Their use in the field is bound to continuously grow in time, due to several advantages, discussed in this work, that such instruments present over more traditional ones. However, their major disadvantage is their increased complexity, the effects of which are highlighted by the literature through evidence of calibration and correction issues. Various field intercomparison experiments showed the evidence of significant biases in NCGs measurements. The goal of this work is to investigate two main sources of bias, producing the largest impact on precipitation measurements. The first source of bias evaluated in this work is due to instrument calibration. Several attempts at developing a calibration procedure are presented both in the scientific literature and from the manufacturers. Nevertheless, those methods are hardly traceable to international standards and, in most cases, lack a suitable reference measure to compare against the instrumental output. In this work, a fully traceable calibration procedure is proposed, in analogy with the one already existing for catching type gauges. This requires drops of know diameter and fall velocity to be released over the instrument sensing area. For this reason, the Calibrated Rainfall Generator (CRG) is developed, able to release single drops on demand and measure them independently just before they reach the instrument sensing area. Detachment of drops is obtained by using an electrostatic system, while the measure of their diameter and fall velocity is performed by means of a photogrammetric approach. The Thies Laser Precipitation Monitor (LPM) was tested using the CRG considering two different output telegrams. The first one provides the raw measure of each drop sensed by the instrument while the second one provides the Particle Size and fall Velocity Distribution (PSVD) matrix. Both telegrams show a tendency to underestimate the drop diameter that increases with decreasing the drop size, while errors in the fall velocity measurements have a less definite trend. Furthermore, tests also show a large standard deviation of the measurements, significantly higher than the one of the reference measurements. The underestimation of drop size and fall velocity is also reflected into the RI measurements provided by the instrument, with a resulting underestimation that decreases with increasing the precipitation intensity. The difference between the two telegrams considered is large and may only be explained by differences in the instrument internal processing for the two telegrams. The second instrument tested using the CRG is the Biral VPF-750, a light scatter gauge. Results show a tendency to underestimate both the drop diameter and fall velocity. In the first case, the error decreases with increasing the drops size, similarly to the Thies LPM. However, the error in the fall velocity is considerably higher and instead increases with increasing the drop sizes. In terms of Rainfall Intensity (RI), the instrument shows a strong underestimation that, due to the opposite trend observed for drop diameter and fall velocity, is almost constant with the precipitation intensity. Both instruments show significant biases, corroborated by field intercomparison results from the literature, that is often larger than 10% for the investigated variables. This means that both gauges cannot be classified according to the guidelines proposed in this work for the development of a standard calibration procedure, derived from those already existing for CGs. The second source of bias is wind, a well-established source of environmental error for traditional Catching-type Gauges (CG) but also affecting NCGs. The wind-induced bias is investigated using a numerical approach, combining Computational Fluid Dynamics (CFD) and Lagrangian Particle Tracking (LPT) models. Two different CFD models were tested, the first providing a time-independent steady state solution, while the other is fully time-dependent. Both were compared against wind tunnel results, showing a good agreement with the experimental data, and proving their ability to capture the complex aerodynamic response of instruments when impacted by the wind. The Thies Laser Precipitation Monitor (LPM) is first chosen as a test instrument, being representative of the typical NCGs that are currently deployed in the field. CFD simulations show that wind direction is the primary factor determining the aerodynamic disturbance close to the instrument sensing area. Similar results were found for the OTT Parsivel2, that is another widely diffused NCG. For wind flow parallel to the laser beam, strong disturbance close to the gauge sensing area is observed. Meanwhile, wind coming perpendicular to the laser beam produces minimal flow disturbance. The wind-induced bias is also investigated for the Vaisala WXT-520, an impact disdrometer. This gauge is smaller ad has a more regular shape if compared to the optical disdrometers, but its measuring principle is based on the detection of the drop kinetic energy, while the size and fall velocity are indirectly obtained. CFD simulations show limited disturbance close to the sensing area of the instrument and a negligeable dependency on the wind direction (due to a more radially symmetric geometry). The instrument body further provide minimal shielding of the sensing area. Strong updraft however occurs upstream of the instrument for all wind directions, significantly affecting the fall velocity of the smaller and lighter drops. Using these results, three different LPT models are also tested. The first is an uncoupled model based on the time-independent CFD results and is used to evaluate the instrument performance for all wind speeds and directions considered. The other two models, due to their high computational requirements, are applied only to a selected number of combinations of wind speed and direction for the Thies LPM. Results show a good agreement and allow concluding that the significant increase in computational burden of the latter two models does not significantly improve the accuracy of the results. However, the one-way coupled model highlights the role of turbulence, that may have a significant impact on the instrumental performance when strong recirculation is present near its sensing area. In the case of the two other gauges, only the uncoupled LPT model in combination with the time-independent CFD model is used, this being the best compromise between numerical accuracy and computational cost. Results of the LPT model are presented in terms of variation in the retrieval of precipitation microphysical properties, Catch Ratios (CR), Collection Efficiency (CE) and Radar Retrieval Efficiency (RRE). For the three gauges considered, it is shown that smaller hydrometeors fall velocity close to the instrument sensing area is strongly affected by wind and is – in general – reduced. A significant wind-induced bias is also evident in the Drop Size Distribution (DSD) measured by the gauges. Optical gauges may report a significant lower number of small hydrometeors even at moderate wind speed. Due to the gauge body partially shielding the sensing area. Impact gauge DSD is also strongly influenced by wind, since hydrometeors with high kinetic energy are sensed as having a large diameter. The DSD is therefore shifted towards larger diameters and the instrument tends to overestimate the number of hydrometeors of all sizes. This suggests that the different shapes of the DSD function reported in the field by different instruments may be due, at least partially, to wind-induced biases. In terms of integral precipitation characteristics, the wind direction is the primary factor in determining the performance of optical gauges in windy conditions. For wind parallel to the laser beam, the instrument senses less and less precipitation with increasing the wind speed, with no hydrometeors even reaching the sensing area in some configurations . On the other hand, when the wind is perpendicular to the laser beam, the instrument performs similarly for all wind speeds, with CR and CE values close to one and only a moderate amount of overcatch being observed at high wind speed. Only for the OTT Parsivel2 a non negligeable overcatch is also evident for wind coming at a 45° angle with respect to the beam direction. For the Vaisala WXT-520 the Kinetic Catch Ratio (KCR) and Kinetic Collection Efficiency (KCE) are defined as substitutes for the CR and CE. At low wind speed, the KCR is below unity, due to the reduction in fall velocity produced by the updraft. However, with increasing wind speed, the kinetic energy of hydrometeors carried by wind increases considerably, overcoming the reduction caused by the updraft close to the gauge. For this reason, KCR values becomes much higher than unity, especially for small size hydrometeors. The increase in kinetic energy is reflected into increased KCE values, that are close to unity at low wind speed, but rapidly grow with increasing the wind speed. Wind direction has instead very limited influence on the measurements. In terms of RRE, optical gauges present limited bias for all combinations of wind speed and direction, except for the highest wind speed and flow parallel to the laser beam. This is because a large portion of the radar reflectivity factor (dBZ) is due to medium and large size hydrometeors, that are less influenced by wind. In the case of the impact disdrometer instead, RRE behaves very similarly to the CE, with values that increases with increasing wind speed. This is due to the shift toward larger diameters noted in the DSD that occurs when hydrometeors kinetic energy is increased by wind