Search Results (22)

Accurate onboard velocity updating is essential for UAV strapdown inertial navigation, especially under GNSS-degraded and high-dynamic conditions. Instead of relying only on local Taylor-series cancellation as λ → 0 or directly transferring coning compensation coefficients, the proposed method redesigns velocity-specific sculling coefficients over the finite dimensionless interval λ = ΩΔT ∈ [⁰,¹]. A two-stage strategy is developed. Stage I constructs a low-cost proxy error model from the analytical expansion and applies a minimax criterion to generate robust candidate coefficients. Stage II further refines them by minimizing a multi-condition time-domain RMS sculling error. Attitude-transfer coefficients are also tested to assess the transferability of optimized coning coefficients to velocity sculling compensation. Under a stringent single-frequency sculling protocol, the velocity-specific Stage-II coefficients reduce the global RMS and worst-case errors by 12.57% and 14.20%, respectively, compared with the classical six-sample coefficients. Under constant specific-force bias, constant angular-rate bias, and double-frequency sculling, the reductions remain 10.62–12.44% and 12.29–16.17%. Ablation and reproducibility checks show that the main gain comes from Stage-II time-domain RMS refinement and remains stable under grid, reference-integration, and base-index variations. Full article

Rowing performance depends on boat velocity and technical efficiency, varying across boat classes. We quantified intracycle velocity variation (IVV) during 2000 m competitions using a GPS- and accelerometry-based monitoring and examined its relationship with biomechanical variables. Forty-nine races were recorded during three national regattas, involving 206 experienced rowers (72 females). Boats were classified by discipline (sweep vs. sculling) and length (short vs. long). Boat velocity and position were recorded using GPS (15 Hz) and accelerometry (100 Hz). Sculling boats demonstrated higher average velocity and lower IVV than sweep boats (p ≤ 0.05), possibly due to reduced lateral asymmetries. Long boats (quadruple scull, four and eight) reached significantly higher maximum, average, and minimum velocities than short boats (single scull, double scull, and pair) (all p ≤ 0.05), as well as greater technical index and distance per cycle. Correlation analysis identified large associations (r ≥ 0.5): in long boats, maximum and minimum velocity (r = 0.79) and cycle rate with distance per cycle (r = −0.50), whereas in short boats, average velocity was associated with minimum velocity (r = 0.76), technical index (r = 0.84) and distance per cycle (r = 0.64). In conclusion, IVV appears to be influenced by boat class and crew characteristics, representing a relevant sensor-derived indicator for monitoring technical efficiency in competitive rowing. Full article

This study aimed to monitor the biomechanical development of an artistic swimming duet across a macrocycle through an individualised training approach. Two swimmers (17.5 ± 0.5 years), members of the Los Angeles 2028 National Olympic Project, were assessed in December 2023 (M1) and April 2024 (M2), corresponding to the beginning and the end of the macrocycle. Maximal (Fmax) and mean (Fmean) force in the prone sculling and kick pull action were measured using a 20 s tethered test. Split velocity (vSplit) was assessed in free format based on video recording. Dry-land strength included assessments of internal (IR) and external (ER) shoulder rotation strength of the dominant (D) and non-dominant (ND) limbs, and countermovement jump (CMJ) power. The standard duet choreography was analysed in competition at both time points. Percentage variation (∆%) between swimmers was calculated for M1 vs. M2. Results showed convergence (M1 vs. M2) in Fmean of the sculling (21.6% vs. 9.9%) and kick pull (45.1% vs. 29.1%), accompanied by greater similarity in vSplit (15.9% vs. 15.5%). Further convergence was observed in IR_ND (33.7% vs. 13.9%), ER_D (11.6% vs. 4.4%) and CMJ (7.4% vs. 3.6%). The duet’s competition score increased from 168.9943 to 190.7183 points. It can be concluded that individualised training was useful for the duet to become more homogeneous in in-water strength, in-water kinematics and dryland strength, resulting in improved competitive performance. Full article

Rowing is a cyclic sport that consists of repetitive biomechanical actions, with performance being influenced by the balance between propulsive and resistive forces. The current study aimed to assess the relationships between intracycle velocity variation (IVV) and key biomechanical and performance variables in male and female single scullers. Twenty-three experienced rowers (10 females) completed a 2000 m rowing competition, during which boat position and velocity were measured using a 15 Hz GPS, while cycle rate was derived from the integrated triaxial accelerometer sampling at 100 Hz. From these data, it was possible to calculate distance per cycle, IVV, the coefficient of velocity variation (CVV), and technical index values. Males presented higher mean, maximum and minimum velocity, distance per cycle, CVV, and technical index values than females (15.40 ± 0.81 vs. 13.36 ± 0.88 km/h, d = 0.84; 21.39 ± 1.68 vs. 18.77 ± 1.52 km/h, d = 1.61; 11.15 ± 1.81 vs. 9.03 ± 0.85 km/h, d = 1.45; 7.68 ± 0.32 vs. 6.89 ± 0.97 m, d = 0.69; 14.13 ± 2.02 vs. 11.64 ± 1.93%, d = 2.06; and 34.25 ± 4.82 vs. 26.30 ± 4.23 (m²/s·cycle), d = 4.56, respectively). An association between mean velocity and intracycle IVV, CVV, and cycle rate (r = 0.68, 0.74 and 0.65, respectively) was observed in males but not in female single scullers (which may be attributed to anthropometric specificities). In female single scullers, mean velocity was related with distance per cycle and was associated with technical index in both males and females (r = 0.76 and 0.66, respectively). Despite these differences, male and female single scullers adopted similar pacing strategies and CVV remained constant throughout the 2000 m race (indicating that this variable might not be affected by fatigue). Differences were also observed in the velocity–time profile, with men reaching peak velocity first and having a faster propulsive phase. Data provided new information on how IVV and CVV relate to commonly used biomechanical variables in rowing. Technical index (r = 0.87): distance per cycle was associated with technical index in both males and females (r = 0.76 and 0.66, respectively). Future studies should include other boat classes and other performance variables such as the power output and arc length. Full article

Dragon boating and rowing are reported to be safe and provide physical benefits for women with breast cancer. Sculling, characterized by a distinct biomechanical technique, may serve as a potential tool to mitigate the adverse side effects of cancer treatments. This study investigated the feasibility and impact of a 6-month integrated physical activity program in breast cancer survivors. A longitudinal intervention study was conducted involving 20 women with breast cancer (age: 55.8 ± 6.1 yrs; BMI: 24.6 ± 3.3 kg/m², stages I-III; surgery performed 6 months to 20 years prior) who participated in a 6-month exercise program consisting of three weekly one-hour sessions of adapted physical activity, walking, and sculling, with assessments conducted at baseline, 3 months, and 6 months. Physical activity, arm lymphedema, flexibility, and fatigue were tested. The program did not lead to the development or worsening of pre-existing lymphedema. A reduction of 78.9 cm³ was observed in the operated limb over 6 months (p = 0.005). An improvement in flexibility was also observed with a 2.7 cm increase in the back scratch test for the operated limb (p < 0.001). However, no significant change in fatigue-related variables was recorded. This is a novel study, as sculling has not previously been investigated in the context of breast cancer rehabilitation. The findings suggested that, when integrated into a structured exercise program, sculling is not only a safe and accessible activity but also effective in promoting physical and health-related improvements, with no adverse events reported. Therefore, it should be considered as part of a comprehensive rehabilitation plan for breast cancer survivors. Full article

The ESA DIVERGENCE (Diversity Architecture for Robust GNSS Receivers in Launcher Applications) project is focused on the design of a GNSS/INS hybrid navigation system and an appropriate FDIR/FDE algorithm for GNC applications in launchers and re-entry vehicles. The main goal is to demonstrate architecture robustness with respect to possible threats and weaknesses introduced by GNSS and INS technology. A baseline navigation system architecture has been developed through a sensor fusion algorithm, which combines IMU, GNSS/DGNSS, a radar altimeter, and a star sensor to cover the accuracy requirements for all the flight phases. The navigation system has been designed to be easily adaptable to multiple applications, such as expendable launch vehicles, micro-launchers, reusable first stage boosters and unmanned re-entry vehicles. The most critical threats/failures were considered for the development of the FDIR/FDE algorithm, comprising GNSS signal outages, spoofing, satellite/receiver clock bias/drift discontinuities, IMU failures, saturation, vibration rectification, coning and sculling, and INS software numerical failures. A preliminary description of the implemented robust FDIR/FDE techniques is reported, and an analysis is conducted to compare the performance before and after FDIR/FDE algorithm implementation in a representative launcher scenario. Full article

Analyzing performance in rowing, e.g., analyzing force and power output profiles produced either on ergometer or on boat, is a priority for trainers and athletes. The current state-of-the-art methodologies for rowing performance analysis involve the installation of dedicated instrumented equipment, with the most commonly employed systems being PowerLine and BioRow. This procedure can be both expensive and time-consuming, thus limiting trainers’ ability to monitor athletes. In this study, we developed an easier-to-install and cheaper method for estimating rowers’ forces and powers based only on cable position sensors for ergometer rowing and inertial measurement units (IMUs) and GPS for scull rowing. We used data from 12 and 11 rowers on ergometer and on boat, respectively, to train a long short-term memory (LSTM) network. The LSTM was able to reconstruct the forces and power at the gate with an overall mean absolute error of less than 5%. The reconstructed forces and power were able to reveal inter-subject differences in technique, with an accuracy of 93%. Performing leave-one-out validation showed a significant increase in error, confirming that more subjects are needed in order to develop a tool that could be generalizable to external athletes. Full article

To reduce the aerodynamic performance degradation caused by the sculling phenomenon on the flap of amphibious seaplanes, this study proposes a grid-slat fusion design method that integrates grid channels into the slats to create multiple lift surfaces. This new configuration enhances not only the lift capacity of the slats but also the lift characteristics of the main wing, leveraging ejector effects from the grid channels. A grid-slat fusion configuration parametrization method is developed based on the “new conic curve” concept, and an optimization approach is implemented using the NSGA-II algorithm. Computational fluid dynamics (CFD) verification of the 30P30N airfoil demonstrates that the grid-slat fusion design enhances the lift-to-drag ratio of the optimized 2D configuration by up to 8.5% at a specific condition, thereby significantly improving its aerodynamic performance at high angles of attack and meeting the requirements for take-off and landing. The three-dimensional configuration demonstrates a stall angle of attack delay of 2° and a maximum lift coefficient increase of 6%. Furthermore, the grid-slat composite configuration allows a better lift-to-drag ratio, and its aerodynamic characteristics improve with increasing wave height. During the wave runup phase, aerodynamic performance is further enhanced, with different wave positions significantly influencing the aerodynamic performance. Full article

Rowing is a complex sport where technique can significantly impact performance. A better understanding of the rowers’ technique and neuromuscular activations during scull rowing, along with their impact on rowing performance, could greatly help trainers and athletes. Twelve male rowers were asked to row at their competitive stroke rate, and we collected data describing neuromuscular activations, trunk and arm kinematics, as well as technical determinants such as oar angles and angle asymmetries. We fitted linear mixed-effect models to investigate the effects of these variables on power production and boat speed. A larger effective angle had the greatest positive effect on power output, and slip angles had the largest negative effects. Increased elbow flexion at catch had the greatest negative effect on speed. Angle asymmetries affected neither power nor speed. Increased upper limb neuromuscular activity during the first and third quarters of the drive phase helped reduce slip angles, thus increasing performance. Power and speed were influenced similarly by the predictor variables. Still, they showed subtle differences, indicating that the strategies to maximize power production might not be the best ones to also achieve the maximum speed. Full article

The purpose of the study was to identify the durations of maintaining apnea, in different static positions, with and without the use of a nose clip, in girls aged between 7 and 14 years,. The study included a total number of 92 girls, grouped by age into four groups of 2-year spans (7–8, 9–10, 11–12, 13–14 years), and depending on the experience of practicing synchronized swimming (6–42 months). In the study we applied five physical tests where apnea maintenance times were recorded in different static positions: Apnea Test of Facial floatation with and without nose clip, Apnea Test of Front tuck with and without nose clip and Apnea Test of Front layout with support to scull. The statistical analysis was performed with SPSS-24. During the study, a program of specific exercises to learn/consolidate the apneic breathing specific to artistic swimming was implemented, for a time interval of 3 months. The results were recorded at the beginning of the study (TI) and at the end of the study (TF). Analyzing the results of the study, we found positive and statistically significant improvements, related to age and experience. The most significant progress, taking into account the averages between the final and initial tests, was recorded in relation to Facial Flotation for 1.301 s for the 7–8-year-old group and 1.110 s for the 9–10-year-old group; the 11–12-year-old group recorded the most positive effect in the Facial Flotation test with a nose clip, with a result of 0.853 s, and in the 13–14-year-old group in the front tuck with nose clip test, a result of 0.807 s was reached. In all tests of the study, the Cohen’s values in all groups fell between 0.184 and 0.478, the size of the effect being small and medium. The ANOVA analysis of variance showed that the differences were statistically significant for p < 0.05 between the arithmetic means of the four groups according to age and sport experiences. For all groups, the value of Wilks’ Lambda was 0.009 (p < 0.01) for age and 0 (p < 0.01) for sports experience, highlighting large differences between groups. We conclude that the development of the ability to maintain apnea specific to synchronized swimming shows an upward trajectory, being conditioned by the training methodology, the age of the subjects and the sports experience. The small and medium values of the effect size highlight the fact that the improvement in apnea maintenance time is dependent on the duration and frequency of the apnea exercises performed in technical conditions specific to synchronized swimming. The training methodology must be adapted to the particularities of age, sports experience and the characteristics of synchronized swimming. Full article

Underground coal mines belong to the GNSS-denied environment, and the Strapdown Inertial Navigation System (SINS) has a significant advantage in the precise positioning of equipment in this environment because of its operation without requiring interaction with external information and strong anti-interference capabilities. Nonetheless, the vibrations of the installation platform adversely affect the positioning accuracy of SINS. This article focuses on the monorail crane in coal mines as the subject of research, developing a dynamic model for the motion unit consisting of the “track + drive unit + driver’s cab”, while analyzing the relationship between track roughness conditions and the vibration excitation of this unit. Subsequently, utilizing the dynamic model, the study calculated the angular and linear vibration characteristics and formulated models to address coning error and sculling error specific to the SINS in this vibration condition. Lastly, by employing a multi-sample compensation algorithm, this article compensated for positioning errors in the SINS caused by track roughness-induced vibrations during uniform straight-line motion of the motion unit, thus achieving optimal positioning information for the monorail crane. The simulation results demonstrated that employing a four-sample compensation algorithm reduces the coning error in SINS positioning calculations by a minimum of 50% and decreases the sculling error by at least 31%, satisfying the positioning accuracy requirements for precise parking of the monorail crane during the transportation phase, while establishing the foundation for autonomous precise positioning and integrated navigation of underground track transport equipment in coal mines. Full article

This paper presents a prototype, on-water rowing monitoring system and its testing results for a single scull boat. The proposed system aims at recording critical kinetic (athlete biomechanics and oar/seat movements) and kinematic (boat position, velocity, acceleration, and attitude) parameters for sport performance evaluation and rowing technique improvement. The data acquisition unit is organized in two parts: the first part aims at logging boat kinematics based on GNSS/INS filtering, while the second one facilitates kinetics data recording using a series of analog sensors (potentiometers, strain gauges) installed on the athlete’s body and the boat seat and oars. Both parts are connected to a central unit featuring analog voltage digitizers and a micro-PC for device handling and data storing. In order to test the performance of the system a series of field trials were undertaken featuring different observation scenarios as well as intentionally induced errors in the rowing technique. Analysis revealed the high performance of the system in terms of sensor completeness and setup procedures as well as operational efficiency. Moreover, system performance evaluation exercised through studying raw data recordings and resultant parameters at stroke cycle and average (standardized) stroke cycle level confirmed the fruitfulness of the proposed approach and system and its potential for implementation on a broad scale. Finally, the data acquired from the proposed system were used to compute the adopted input parameters and performance indicators to characterize the system in terms of functionality and operational efficiency. Full article

The rowing technique is a key factor in the overall rowing performance. Nowadays the athletes’ performance is so advanced that even small differences in technique can have an impact on sport competitions. To further improve the athletes’ performance, individualized rowing is necessary. This can be achieved by intelligent measurement technology that provides direct feedback. To address this issue, we developed a novel wireless rowing measurement system (WiRMS) that acquires rowing movement and measures muscle activity using electromyography (EMG). Our measurement system is able to measure several parameters simultaneously: the rowing forces, the pressure distribution on the scull, the oar angles, the seat displacement and the boat acceleration. WiRMS was evaluated in a proof-of-concept study with seven experienced athletes performing a training on water. Evaluation results showed that WiRMS is able to assess the rower’s performance by recording the rower’s movement and force applied to the scull. We found significant correlations (p < 0.001) between stroke rate and drive-to-recovery ratio. By incorporating EMG data, a precise temporal assignment of the activated muscles and their contribution to the rowing motion was possible. Furthermore, we were able to show that the rower applies the force to the scull mainly with the index and middle fingers. Full article

Intelligent mining is the demand and inevitable development direction of China’s coal industry, and the shearer attitude based on the 3D spatial scale is the essential basic information for realizing intelligent mining at the fully mechanized mining face. The traditional shearer attitude monitoring technology cannot meet the accuracy requirements of attitude sensing of mining equipment at an intelligent working face. In this paper, based on the basic principle of strapdown inertial navigation system (SINS), a real-time solution algorithm for shearer attitude is constructed, and the specific process of SINS coarse alignment and fine alignment is studied. The main error terms affecting the accuracy of SINS are analyzed, and the initial alignment error, installation deviation angle error, and vibration effect error are compensated and analyzed through simulation one by one. According to the working characteristics of the shearer, the coning error and sculling error of the shearer’s SINS are compensated and analyzed through simulation. This paper provides a complete set of theories and methods for improvement of the accuracy of the shearer attitude sensing in underground operation; simulation results also verify that the theories and methods can significantly improve the perception accuracy which can provide theoretical and technical reference for the production state prediction of fully mechanized mining face and intelligent control of underground mining equipment. Full article

The agile and power-efficient locomotion of a water strider has inspired many water-walking devices. These bioinspired water strider robots generally adopt a DC motor to create a sculling trajectory of the driving leg. These robots are, thus, inevitably heavy with many supporting legs decreasing the velocity of the robots. There have only been a few attempts to employ smart materials despite their advantages of being lightweight and having high power densities. This paper proposes an artificial muscle-based water-walking robot capable of moving forward and turning with four degrees of freedom. A compliant amplified shape memory alloy actuator (CASA) used to amplify the strain of a shape memory alloy wire enables a wide sculling motion of the actuation leg with only four supporting legs to support the entire weight of the robot. Design parameters to increase the actuation strain of the actuator and to achieve a desired swing angle (80°) are analyzed. Finally, experiments to measure the forward speed and angular velocities of the robot are carried out to compare with other robots. The robot weighs only 0.236 g and has a maximum and average speed of 1.56, 0.31 body length per second and a maximum and average angular velocity of 145.05°/s and 14.72°/s. Full article