Dynamic Positioning Research Articles

Robot Dynamic Object Positioning and Grasping Method based on Two Stages

Robot Dynamic Object Positioning and Grasping Method based on Two Stages

Optimized Chassis Stability Relative to Dynamic Terrain Profiles in a Self-Propelled Sprayer Multibody Dynamics Model

Highlights This study presented a new optimization methodology using a prismatic joint with high stiffness and damping. The virtual suspension model contained the main bodies, an optimization subsystem, and a free-floating cylinder. Under aggressive terrain, an optimized chassis platform resulted in a 19.5% increase in boom height stability. Abstract. Multibody dynamics (MBD) models are continuing to be valuable for engineering design and product development, especially regarding subsystem optimization. Most MBD optimization processes begin with a sensitivity analysis of treatment factors and levels to understand how uncertainty in model inputs can be attributed to different sources of uncertainty within model outputs; however, this study developed a new MBD methodology to automatically determine the optimized dynamic chassis suspension responses on each corner of the vehicle from a single simulation for a self-propelled sprayer model as the chosen application use-case. This technique leveraged a prismatic joint (with a high spring stiffness and damping coefficient) connected between the chassis mainframe and the simplified optimization tire to create a distance constraint that held the chassis body at a near-consistent height above the ground. Then the solver optimized the response of the chassis suspension system to maintain a stable chassis platform relative to the terrain beneath it as the vehicle traversed across dynamic terrain conditions. This optimization response was also accomplished by replacing the baseline chassis suspension components with a free-floating cylinder, which permitted the unrestricted, optimized motion needed to keep the chassis body at a near-level position with respect to the roll and pitch profiles of the terrain. For a simulation with an aggressive terrain configuration, the analysis showed that an optimized suspension system resulted in a 46% decrease in operator comfort and a 19.5% increase in overall boom height stability as the boom height control system better maintained a dynamic position closer to the specified target height. Keywords: Boom height, Chassis suspension, Multibody dynamics (MBD), Optimization, Prismatic joint, Simulation, Terrain.

Dynamic analysis of the subsea production system with lazy-wave risers attached to FPSO.

The lazy-wave riser is an input and output riser for a flexible development system, which is widely used in all the riser and pipeline systems. Because of the influence of various factors, its configuration description, control and motion which have a strong nonlinear character are complex during the running process of the lazy-wave riser. Reference to the specific structure and environmental parameters of a certain lazy-wave risers system with a 300 thousand tons FPSO, with the basis of the specific process of the flexible riser system at work, the lazy-wave risers were discretized into lumped mass models, combined with AQWA, the simplified dynamic model of the whole system at the depth of 2100m has been established by the large hydrodynamic analysis software OrcaFlex. The dynamic response characteristics of the lazy-wave risers have been given by using time domain coupling method. With and without the consideration of the 2nd wave drift load in the simulation process, the effects of the 2nd wave drift load on the results are obtained. The simulation results reveal the difficulty of simulation convergence caused by a large number of risers and flexible components. The 2nd order wave drift loads have a significant effect on the riser system, resulting in the increasement of the effective tension at each end of each riser. To counteract the magnitude of the FPSO response caused by such loads, the number of mooring lines needed to be increased or combined with dynamic positioning techniques to optimize the design.

Workers and Their Foes: Customer Scapegoats in the Service Triad

The author reconceptualizes the service triangle as a Simmelian triad and draws on 16 months of fieldwork to analyze restaurant servers’ experiences of income and interactional precarity. Precarious work frustrates servers. However, triadic dynamics position customer scapegoats as responsible for servers’ frustrations. Employers passively benefit from this dynamic, which continually minimizes opposition to the structure of employment. This is a new mechanism for the reproduction of precarious service work that can explain why service workers consent to exploitation. These findings apply to workplaces in which workers experience low levels of autonomy and encounter customers who are interactionally salient and can control workers’ behavior. In such workplaces, the triadic dynamics identified in this article could weaken the potential for worker-customer alliances and complicate the promise of anti-tipping campaigns.

Design and stabilization analysis of luxury cruise with dynamic positioning systems based on sampled-data control.

This paper studies the sampled-data control issue for a luxury cruise (LC) with dynamic positioning system (DPS). The design method and mathematical model of LC is given. By constructing an improved time-dependent Lyapunov-Krasovskii function (LKF) by adding new useful terms, the sampling pattern is fully captured and less conservatism of the results are obtained. Based on the constructed the LKF, the new stability criterion is obtained and the sampled-data controller for LC with DPS is designed. Finally, an example is exhibited to prove that the proposed approach is valid and applicable.

Smart Dynamic Position Tracking Wearable for Geofencing in Marine Environment

Smart Dynamic Position Tracking Wearable for Geofencing in Marine Environment

Modeling and Detection of Dynamic Position Sensor Offset Error in PMSM Drives

Rotor position information obtained through a position sensor is crucial for proper field-oriented control (FOC) of permanent magnet synchronous machine-based high dynamic energy conversion applications. In applications such as transportation and industrial, PMSM energy conversion systems are subjected to harsh environmental conditions such as vibration, shock, and thermal shock causing mechanical interfaces holding position sensors to fail, introducing errors to the position measurement. A dynamic position sensor offset error (DPSOE), being such a failure mode has the potential to degrade system torque output or more adversely, reverse machine torque output that may cause catastrophic outcomes. This paper evaluates different DPSOE scenarios, presents an approach to model the failure mode for analysis and proposes two novel, and robust DPSOE detection methods for PMSM drive systems. The proposed detection methods are analytically proven and supported by simulation and experimental results under multiple operating conditions proving robustness.

Designation of the Boundary Conditions for Estimating the Thrust Loss due to Thruster-Hull Interactions

The azimuth thruster is mainly installed on a vessel that requires a dynamic positioning (DP) function for special purposes. When the azimuth thruster on a vessel operates for DP, the thrust loss is induced by the thruster-hull interaction. This study examined the influence of boundary conditions in numerical simulations for predicting thrust loss. Wind turbine installation vessels (WTIV) and floating production storage and offloading (FPSO) were chosen as a target vessels. In this study, two types of boundaries were defined. The first consideration is that the boundary condition was assigned with consideration of the azimuth angle of the thruster, whereas it is fixed regardless azimuth angle of the thruster. The predicted thrust loss according to these boundary conditions showed a difference. This observation originated from the current load of the vessel. Therefore, the boundary conditions for which the current load is not induced need to be designated to obtain a realistic thrust loss in a numerical simulation.

Does the Retül System provide reliable kinematics information for cycling analysis?

The Retül Vantage system is a popular tool to assess dynamic positioning of cyclists. Despite of using a low sampling rate (18 Hz) to record position data, Retül measures shows a moderate to very high correlation with data from gold-standard tridimensional camera systems reaching higher sampling rates, but its reliability has not been tested. Here we assess the reliability of the Retül Vantage system for kinematic assessment of cyclists. This cross-sectional study had two phases. Phase 1 included a survey with certified Retül bike fitters to select the most common variables used in cycling kinematics assessment. Phase 2 involved assessment of the selected cycling kinematics variables to check for intra-examiner reliability. Ten bike fitters answered the online survey (response rate of 47.6%) and 7 variables were identified as the most common to conduct during bike fitting analysis. Then, ten cyclists were submitted to kinematic assessments and Vantage system variables were checked for inter-examiner reliability and standard error of the variables. Good to excellent inter-tester reliability levels were found for all the 7 kinematics variables tested. Standard error of angular variables was lower than 3º for all as well as lower than 5 mm for the linear variable tested. The minimal detectable difference values ranged from 2.15 to 6.55º for angular variables and of 15.51 mm for linear variables. A high and very high degree of intra-rater reliability can be achieved using Retül Vantage system for kinematics assessment of the most common variables included in bike fitting.

Dynamic Hull Vane—A Solution for Active Pitch Motion Reduction and Resistance Reduction of Ships

_ The Dynamic Hull Vane® is an actively controlled version of the Hull Vane®, a patented energy-saving and seakeeping device which consists of a submerged wing mounted on the aft ship. The Hull Vane is positioned in the upward flow aft of the ship, to develop forward thrust and reduce the stern wave. Naiad Dynamics US Inc, is a supplier of ride control systems and has worked with Hull Vane BV to develop the Dynamic Hull Vane®. By enabling the Hull Vane® to rotate, it can produce variable lift forces which when suitably controlled can reduce the pitching motions of a vessel in a seaway. This paper describes some of the research carried out on the AMECRC series 13, a generic fast displacement hull. Introduction Among other characteristics, two main performance parameters of a ship are fuel consumption and ship motions. Besides a well-designed hull, several appendages can be used to increase the performance. One of this is the Hull Vane. The Hull Vane is a fixed hydrofoil behind the transom of the ship. The Hull Vane has the potential to create large lift forces on the aft ship, thereby changing the resistance and the dynamic position of the vessel (Uithof et al. 2014). Ship motion reduction has long been a topic of research, and this has led to a number of solutions, which are widely applied. Most of the study work and products have been related to the rolling motions of ships, and there are indeed various effective solutions available, such as fin stabilizers, gyrostabilizers, interceptors, trim tabs, and antiroll tanks. The pitching motion of ships has been studied less, and while there are systems on the market to actively dampen the pitching motions of fast (planing) vessels, it has always been a challenge to dampen the pitch and heave motions of displacement ships, due to their inertia and limited speed. The pitch and heave motions are the prime source of vertical accelerations on board and these in turn are one of the main contributors in the Motion Sickness Incidence (MSI). Passive systems to reduce pitch motions exist, such as bow foils, which are preferably retractable to avoid their resistance penalty in calm water. There are two passive systems which dampen pitching motions while not adding calm-water resistance on specific ship types, because they reduce the wavemaking resistance of the ship: the bulbous bow and Hull Vane®. The pitch dampening effect of the passive Hull Vane has been demonstrated on naval vessels in computational fluid dynamics (CFD) (Bouckaert 2016) and in model tests (Ferré 2019).

Research on Indoor 3D Positioning Algorithm Based on WiFi Fingerprint

Indoor 3D positioning is useful in multistory buildings, such as shopping malls, libraries, and airports. This study focuses on indoor 3D positioning using wireless access points (AP) in an environment without adding additional hardware facilities in large-scale complex places. The integration of a deep learning algorithm into indoor 3D positioning is studied, and a 3D dynamic positioning model based on temporal fingerprints is proposed. In contrast to the traditional positioning models with a single input, the proposed method uses a sliding time window to build a temporal fingerprint chip as the input of the positioning model to provide abundant information for positioning. Temporal information can be used to distinguish locations with similar fingerprint vectors and to improve the accuracy and robustness of positioning. Moreover, deep learning has been applied for the automatic extraction of spatiotemporal features. A temporal convolutional network (TCN) feature extractor is proposed in this paper, which adopts a causal convolution mechanism, dilated convolution mechanism, and residual connection mechanism and is not limited by the size of the convolution kernel. It is capable of learning hidden information and spatiotemporal relationships from the input features and the extracted spatiotemporal features are connected with a deep neural network (DNN) regressor to fit the complex nonlinear mapping relationship between the features and position coordinates to estimate the 3D position coordinates of the target. Finally, an open-source public dataset was used to verify the performance of the localization algorithm. Experimental results demonstrated the effectiveness of the proposed positioning model and a comparison between the proposed model and existing models proved that the proposed model can provide more accurate three-dimensional position coordinates.

A Robust Adaptive Filtering Algorithm for GNSS Single-Frequency RTK of Smartphone

In this paper, a single-frequency real-time kinematic positioning (RTK) robust adaptive Kalman filtering algorithm is proposed in order to realize real-time dynamic high-precision positioning of smartphone global navigation satellite systems (GNSSs). A robust model is established by using the quartile method to dynamically determine the threshold value and eliminate the gross error of observation. The Institute of Geodesy and Geophysics Ⅲ (IGG Ⅲ) weight function is used to construct the position and speed classification adaptive factors to weaken the impact of state mutation errors. Based on the analysis of the measured data of Xiaomi 8 and Huawei P40 smartphones, simulated dynamic tests show that the overall accuracy of the Xiaomi 8 is improved by more than 85% with the proposed robust RTK algorithm, and the overall positioning error is less than 0.5 m in both open and sheltered environments. The overall accuracy of the Huawei P40 is improved by more than 25%. Furthermore, the overall positioning accuracy is better than 0.3 m in open environments, and about 0.8 m in blocked situations. Dynamic experiments show that the use of the robust adaptive RTK algorithm improves the full-time solution planar positioning accuracy of the Xiaomi 8 by more than 15%. In addition, the planar positioning accuracy under open and occluded conditions is 0.8 m and 1.5 m, respectively, and the overall positioning accuracy of key nodes whose movement state exhibits major changes improves by more than 20%.

Who’s the Dupe? A Farce

Who’s the Dupe? A Farce

Dynamic response of a SWATH vessel for installing pre-assembled floating wind turbines

New and efficient installation concepts which can reduce the cost of developing an offshore wind farm are of particular interest. This paper explores a promising concept using the small water-plane area twin-hull vessel (SWATH) to install pre-assembled wind turbines (OWT) onto floating spar foundations. A focus is placed on the hydrodynamic performance of the SWATH and the response analysis of the coupled SWATH-spar system. Firstly, the numerically calculated difference-frequency wave force effect and damping forces of the original SWATH were verified with experimental data. Secondly, the original SWATH was modified to satisfy the criteria of weight-carrying capacity and hydrostatic stability. Thirdly, a multibody numerical model for the SWATH-spar system was developed, in which the hydrodynamic and mechanical couplings between the SWATH and a spar were considered. The SWATH is equipped with a dynamic positioning system to counteract the slow-drift wave force effects. The nonlinear time-domain simulations were carried out for the mating stage when a wind turbine is lifted above the spar foundation. Based on the analysis of statistics of the relative displacement and velocity of the tower bottom and the spar top, the installation concept with SWATH is found to be of decent performance. Finally, recommendations are provided for future research on this concept, which contributes to developing next-generation installation concepts for bottom-fixed and floating wind farms.

Analysis of data fusion algorithms for the vessel with the dynamic positioning system

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Adaptive Kalman filter based on integer ambiguity validation in moving base RTK

In high-precision dynamic positioning, it is necessary to ensure the positioning accuracy and reliability of the navigation system, especially for safety–critical applications, such as intelligent vehicle navigation. In the face of a complex observation environment, when the global navigation satellite system (GNSS) uses carrier phase observations for high-precision relative positioning, ambiguity resolution will be affected, and it is difficult to estimate all ambiguities. In addition, when the GNSS signal quality and measurement noise level are difficult to predict in an environment with many occlusions, the received satellite observations are prone to very large errors, resulting in apparent deviations in the positioning solution. However, traditional positioning algorithms assume that the measurement noise is constant, which is unrealistic. This will cause incorrect ambiguity resolution, lead to meter-level positioning errors, reduce the reliability of the system, and increase the integrity risk of the system. We proposed an innovative adaptive Kalman filter based on integer ambiguity validation (IAVAKF) to improve the efficiency of ambiguity resolution (AR) and positioning accuracy. The partial ambiguity resolution (PAR) method is applied to solve the integer ambiguities. Then, the accuracy of the fixed ambiguity is verified by the ambiguity success rate. Taking the ambiguity success rate as a dynamic adjustment factor, the measurement noise matrix and variance–covariance matrix of the state estimation is adaptively adjusted at each time interval in the Kalman filter to provide a smoothing effect for filtering. The optimal Kalman filter gain matrix is obtained to improve positioning accuracy and reliability. As a result, the static and dynamic vehicle experiments show that the positioning accuracy of the proposed IAVAKF is improved by 26% compared with the KF. Through the IAVAKF, a more realistic PL can be obtained and applied to evaluate the integrity of the navigation system in the position domain. It can reduce the false alarm rate by 2.45% and 1.85% in the horizontal and vertical directions, respectively.

Human-automation interaction centered approach based on FRAM for systemic safety analysis of dynamic positioning operations for offshore tandem offloading

The offshore and maritime industry comprises technologically complex vessels and facilities with increasing automation. However, automation may introduce human-automation interaction problems with possibly catastrophic consequences. Dynamic positioning (DP) operations are typical of high exposure to such threats. This study develops a human-automation interaction centered approach for systemic DP operational safety analysis in offshore tandem offloading. The proposed methodology utilizes a prevailing systemic method, i.e., the functional resonance analysis method (FRAM), to resolve holistic modeling of human-automation interaction. Therein, a novel semi-quantitative framework of FRAM based on Monte Carlo simulation is integrated and improved to facilitate traditional FRAM analysis. A case application of the methodology is presented to demonstrate the usefulness for unraveling human interactions with the DP system and enhancing operational safety. An integral FRAM model is established to investigate the performance variability of human and DP automation and their various manners of aggregation in the interactive context of tandem offloading. The results reveal critical functions, couplings, and interrelated resonant paths for systemic analysis of the emergence of tanker drive-off and collision scenarios. The FRAM analysis embraces Safety-II and resilience engineering perspective to devise more proactive safety strategies through managing variability and augment DP safety management.

Network-Based Multiple Operating Points Cooperative Dynamic Positioning of Unmanned Surface Vehicles

This article investigates the network-based multiple operating points cooperative dynamic positioning of multiple unmanned surface vehicles. First, a dynamic positioning system model is established for multiple unmanned surface vehicles. Second, a network-based multiple operating points cooperative dynamic positioning control protocol and a resultant system model for multiple unmanned surface vehicles are constructed under fixed topologies. Third, a networked multiple operating points cooperative dynamic positioning control scheme, which can guarantee the multiple operating points cooperative dynamic positioning error exponentially converge to a bounded region, is proposed. The dynamic positioning control scheme design is then extended to the case of switching topologies. Finally, the multiple operating points cooperative dynamic positioning performance analysis verifies the efficiency of the proposed control schemes.

The Effectiveness of Serial Casting in the Treatment of Recurrent Equinovarus in Children With Arthrogryposis.

Arthrogryposis multiplex congenita (AMC) is characterized by joint contractures in 2 or more body areas, often resulting in clubfoot deformities that are typically stiffer than those seen in idiopathic clubfoot deformities. While surgery is routinely used to treat clubfoot in AMC, it has a high rate of recurrence and complications. Current literature suggests serial casting (SC) could be useful in treating clubfoot in AMC, though evidence of its effectiveness is limited. Passive range of motion (PROM), dynamic foot pressure, parent-reported Pediatric Outcomes Data Collection Instrument, brace tolerance, and the need for post-casting surgery were evaluated retrospectively in children with AMC treated with SC to address clubfoot deformities. Analysis of variance or paired t tests were used as appropriate on pre-casting, short-term (within 6mo after SC) and/or longer-term (6 to 18mo after SC) parameters to determine the effectiveness of SC. Brace tolerance before and after SC was analyzed using the Global Test for Symmetry, and medical records were reviewed to determine the need for surgery post-SC. Forty-six children (6.1±3.1y old) were cast an average of 2.5±1.9 times, resulting in 206 SC episodes. PROM showed improvement in ankle dorsiflexion and forefoot abduction in the short term (P<0.05), returning to baseline measurements in the long term (P=0.09). Brace tolerance improved after casting (P<0.05). Only 15% of feet required surgery at follow-up at 10.3±5.5 years. There were no significant changes in dynamic foot pressure or Pediatric Outcomes Data Collection Instrument results after SC, except for an increase in the pain subtest (P<0.05). Serial casting in children with AMC can be effective in temporarily improving PROM and improving brace tolerance, but it does not impact dynamic barefoot position. Positive impact of conservative management in children with AMC can potentially delay or reduce the need for invasive surgical intervention by improving PROM and brace tolerance. Level III, Retrospective Comparative Study.

Rapid Re-Convergence of Real-Time Dynamic Precise Point Positioning by Adding Velocity Constraints

Rapid Re-Convergence of Real-Time Dynamic Precise Point Positioning by Adding Velocity Constraints