Kinematic guidance using virtual reference point for underactuated marine vehicles with sideslip compensation

Accurate detection of the unknown radio transmitter (URT) is crucial to combat illegal occupation of radio signal resources and protect communication system from harmful signal interference. The fingerprint positioning technique based on received signal strength (RSS) is famous for requiring no extra equipment, antenna arrays, and time synchronization. However, conventional RSS-based fingerprint positioning techniques that utilize K-nearest neighbor (KNN) method are confronted with problems when the positioning target is radio transmitter with unknown emission strength and frequency. Moreover, they not only cannot realize the precise localization of the URT but also only rely on pre-set reference points in the fingerprint database. In this paper, a new KNN-based geo-location approach using received signal strength difference (RSSD) information and virtual reference point is proposed to estimate an URT location. To obtain more accurate RSSD measurements, a RSSD-based filtering method by calculating the Euclidean distance between each sampling RSSD and the average value is devised to establish the fingerprint database. To achieve higher positioning accuracy, we combine KNN technique with the virtual reference (VR) point to propose RSSD-VRKNN algorithm. The simulation results show that the proposed scheme can obtain the best positioning performance compared with the conventional KNN and weighted K-nearest neighbor (WKNN) techniques. The performance and feasibility of our proposed algorithm are verified through extensive experiments.

Defining static floor field of evacuation model in large exit scenario

In order to measure the character of the biology impedance at the same time and different frequency, the excitation method of multi-frequency and mixing frequency is used. As for the problem on the phase error led by general biology impedance measurement, a novel biology impedance measurement method based on virtual reference point was presented. According to the corresponding relationship between the reference resistance and the measured impedance in the vector space, the magnitude and phase of the measured impedance may be calculated. A prototype system based on the method was constructed and the experimental tests compared with the Agilent 4294A impedance analyzer show that the method is feasible

In this paper, a nonlinear tracking controller with integral action for ships is presented. The controller is based on state feedback linearization. Exponential convergence of the vessel-fixed position and velocity errors are proven by using Lyapunov stability theory. Since we only have two control devices, a rudder and a propeller, we choose to control the longship and the sideship position errors to zero while the heading is stabilized indirectly. A Virtual Reference Point (VRP) is defined at the bow or ahead of the ship. The VRP is used for tracking control. It is shown that the distance from the center of rotation to the VRP will influence on the stability of the zero dynamics. By selecting the VRP at the bow or even ahead of the bow, the damping in yaw can be increased and the zero dynamics is stabilized. Hence, the heading angle will be less sensitive to wind, currents and waves. The control law is simulated by using a nonlinear model of the Japanese training ship Shiojimaru with excellent results. Wind forces are added to demonstrate the robustness and performance of the integral controller.

Nonlinear Control of Ships Minimizing the Position Tracking Errors

International audience

In this paper, a sliding mode controller is presented for the trajectory tracking by a group of ships with an established formation along a given parametrized path via neural network and sliding mode control technique. The control objective for each ship is to keep its relative positon in the formation while a virtual Formation Reference Point (FRP) tracks a predefined path. We first solve the virtual structure formation problems via sliding mode control method due to its excellent adaptability to external disturbance and system perturbation. Moreover, a radial basis function NN is considered in the design of the controller to approximate the unknown uncertainties efficiently. Some simulations are given to verify the theoretical results in this paper.

In this paper, a local observer is designed for formation control of marine surface vessel. Sliding mode control is applied to follow the desired the formation of marine surface vessel and a local state observer is designed by Linear Matrix Inequation (LMI). The goal of formation control is to keep the relative position of each marine surface vessel in the formation given in the virtual formation reference point (FRP) path is given. For controller needs a good performance of external disturbance, the sliding mode control algorithm is used in the formation control of marine surface vessel. A local state observer scheme is designed in which the parameters of the observer are computed. Various simulations are given to illustrate the controller validity.

This paper first proposes a new clustering algorithm for selection of reference points (RPs) based on virtual positions of access points for indoor localization in area without linear constraints, which can not only cluster automatically but also guarantee the consistency of methods between the offline phase clustering and the online phase positioning. A new weighted algorithm based on physical distance is then presented for position determination. With angle velocity measurement provided such as by gyroscope, the weighted algorithm is particularly suited for scenarios where the mobile moves along a trajectory. The number of clusters in traditional RP clustering algorithms needs to be predefined, which means an unsuitable number of clusters would lead to poor estimation accuracy. Traditional weighted K-nearest neighbor (WKNN) algorithm weights the RPs' coordinates by the inverse of the received signal strength indication (RSSI) difference, which is not accurate enough because of the exponential relationship between RSSI and physical distance. Furthermore, methods based on probabilistic model or data fusion do not consider the uneven spatial resolution of Wi-Fi RSSI. Experimental results show that the proposed weighted algorithm considerably outperforms the K-nearest neighbor (KNN), Euclidean-WKNN, ManhattanWKNN, EWKNN, LiFS, and GPR in terms of positioning accuracy which is defined as the cumulative distribution function of position error. The results also demonstrate that RPs in indoor area without linear constraints can be clustered automatically by the proposed clustering algorithm, and cumulative distribution function of the proposed clustering algorithm outperforms KNN, WKNN, RP location clustered, and signal distance clustered.

The dynamic multi-frequency bioimpedance measuring system based on discrete fourier transform is designed in this paper, in order to obtain the bioimpedance information in different frequencies simultaneously. A novel information extraction method of discrete fourier transform combined with the virtual reference point is presented. The hardware platform of the system is composed of the signal source module, the signal conditioner and PCI-6111 card. Using LabVIEW, functions of the collection, analysis, display and data storage are implemented, with which the bioimpedance information can be detected dynamically. From the experimental results, the dynamic reaction of respiratory and sphygmous information in different frequencies can be manifested according to the human impedance measurement

International audience

The point following method controls the vehicle so that it follows a virtual reference point that is moving along the road. The control system in the vehicle is simpler than the one in the car-following method, but it needs an infrastructure on the roadside to provide reference points along the road. As an extension of this method, a moving cell control scheme was proposed, in which the reference point is given in a cell and a vehicle is controlled so that it remains in the cell moving along the road. This paper proposes a platoon control method as an extension of the moving cell control scheme. This method enables us to create a platoon controller that does not generate a dilatational wave, consisting of a simple PID controller using a simple form of communication from the preceding vehicle to the following vehicle, we call this method car in a virtual moving cell.

The upper eyelid blepharoplasty incision affords direct access to the frontal bone for skull base surgery and trauma reconstruction with a well-hidden scar. The goal of this study is to quantify frontal bone exposure that can be achieved with an upper eyelid blepharoplasty incision. Anatomic study with human cadaver heads. UC Davis Medical Center. Fourteen human cadaver heads were used to perform 26 upper blepharoplasty approaches. Exposure was measured with virtual planning software to create virtual reference points at the midline of the superior orbital rim. Surgical navigation was used with a 3-dimensionally printed drill model to measure the maximum exposure achievable relative to the virtual reference point at 5 standardized angles. Mean ± SD exposures at medial 60°, medial 30°, 0°, lateral 30°, and lateral 60° were 16.1 ± 1.3 mm, 17.8 ± 1.3, 18.3 ± 1.4, 19.3 ± 1.9, and 20.9 ± 1.9, respectively. Significant differences were detected between exposures at 60° laterally and 60° medially and between exposures 60° laterally and 30° medially ( P < .05). The upper eyelid blepharoplasty incision provides direct surgical access to the inferior frontal bone. Access was greatest with far lateral extension (mean, 20.9 mm) and most limited with far medial extension (mean, 16.1 mm). Treatment of injuries above this level could be achieved with additional percutaneous incisions for screw placement.

This paper aims to define and describe features of the motion of coronary arteries in two and three dimensions, presented as geometrical parameters that identify motion patterns. The main left coronary artery centerlines, obtained from digital subtraction angiography (DSA) image sequences, are first reconstructed. Thereafter, global and local motion features are evaluated along the sequence. The global attributes are centerline and point trajectory lengths, displacement amplitude, and virtual reference point, while local attributes are displacement direction, perpendicular/radial components, rotation direction, and curvature and torsion. These kinetic features allow us to obtain a detailed quantitative description of the displacements of arteries' centerlines, as well as associated epicardium deformations. Our modeling of local attributes as quasi-homogeneous on a segment analysis, enables us to propose a novel numeric to symbolic image transformation, which provides the required facts for knowledge-based motion interpretation. Experimental results using real data are consistent with cardiac dynamic behavior.

High-speed blades form core mechanical components in turbomachines. Research concerning online monitoring of operating states of such blades has drawn increased attention in recent years. To this end, various methods have been devised, of which, the blade tip-timing (BTT) technique is considered the most promising. However, the traditional BTT method is only suitable for constant-speed operations. But in practice, the rotational speed of turbomachine blades is constantly changing under the influence of external factors, which lead to unacceptable errors in measurement. To tackle this problem, a new BTT method based on multi-phases is proposed. A plurality of phases was arranged as evenly as possible on the rotating shaft to determine the rotation speed. Meanwhile, the corresponding virtual reference point was determined in accordance with the number of blades between consecutive phases. Based on these reference points, equations to measure displacement due to blade vibrations were deduced. Finally, mathematical modeling, numerical simulation and experimental tests were performed to verify the validity of the proposed method. Results demonstrate that the error in measurement induced when using the proposed method is less than 1.8 %, which is much lower compared to traditional methods utilized under variable-speed operation.