Real-time Tracking Framework Research Articles

Real-time tracking and berthing aid system with occlusion handling based on LiDAR

In smart ports, accurate perception of the state of a berthing ship relative to the berth is critical for the safety and efficiency of ships and ports. A real-time tracking and berthing system with occlusion handling based on Light Detection and Ranging (LiDAR) is proposed. First, the data is pre-processed, including fast filtering and clustering, and then a real-time tracking framework is proposed to solve the occlusion problem. This framework adapts to different berthing scenarios through accurate determination of dynamic and static targets and efficient retracking of berthing ships. To verify the effectiveness of the method, an on-site monitoring experiment of the “Yukun” training ship in Dalian Port is conducted, and a simulated berthing scene under occlusion is constructed to test the algorithm. The practical results prove that our method shows feasibility and effectiveness in the application of ship dynamic target tracking and safe ship berthing.

Research on Lane-Change Strategy With Real-Time Obstacle Avoidance Function

Lane changing (LC) is the basic maneuver of a variety of lateral control scenes such as overtaking, paralleling, collision avoidance, etc. The surrounding vehicle may drive into the planned path during the ego-vehicle's LC maneuver, the ego-vehicle could only stop or fail to respond in time. Aiming to tackle this issue, this article proposes a LC strategy with real-time obstacle avoidance function. Firstly, the common LC strategy adopts the single planning and real-time tracking framework, which cannot handle emergent situations during the LC maneuver. This article proposes a new framework of real-time planning and real-time tracking for obstacle avoidance in the process of the LC. Secondly, this article constructs a two-layer judgment condition and control mode matrix for the two obstacle avoidance conditions of current-lane preceding-vehicle lane-change (CPC) and target-lane preceding-vehicle deceleration (TPD). Finally, experiments and simulations demonstrate the effectiveness of the proposed algorithm.

Real-Time Tracking of Single and Multiple Objects from Depth-Colour Imagery Using 3D Signed Distance Functions

We describe a novel probabilistic framework for real-time tracking of multiple objects from combined depth-colour imagery. Object shape is represented implicitly using 3D signed distance functions. Probabilistic generative models based on these functions are developed to account for the observed RGB-D imagery, and tracking is posed as a maximum a posteriori problem. We present first a method suited to tracking a single rigid 3D object, and then generalise this to multiple objects by combining distance functions into a shape union in the frame of the camera. This second model accounts for similarity and proximity between objects, and leads to robust real-time tracking without recourse to bolt-on or ad-hoc collision detection.

Real-Time Tracking Framework with Adaptive Features and Constrained Labels.

This paper proposes a novel tracking framework with adaptive features and constrained labels (AFCL) to handle illumination variation, occlusion and appearance changes caused by the variation of positions. The novel ensemble classifier, including the Forward–Backward error and the location constraint is applied, to get the precise coordinates of the promising bounding boxes. The Forward–Backward error can enhance the adaptation and accuracy of the binary features, whereas the location constraint can overcome the label noise to a certain degree. We use the combiner which can evaluate the online templates and the outputs of the classifier to accommodate the complex situation. Evaluation of the widely used tracking benchmark shows that the proposed framework can significantly improve the tracking accuracy, and thus reduce the processing time. The proposed framework has been tested and implemented on the embedded system using TMS320C6416 and Cyclone Ⅲ kernel processors. The outputs show that achievable and satisfying results can be obtained.

TH-AB-202-05: BEST IN PHYSICS (JOINT IMAGING-THERAPY): First Online Ultrasound-Guided MLC Tracking for Real-Time Motion Compensation in Radiotherapy

Purpose: While MLC tracking has been successfully used for motion compensation of moving targets, current real-time target localization methods rely on correlation models with x-ray imaging or implanted electromagnetic transponders rather than direct target visualization. In contrast, ultrasound imaging yields volumetric data in real-time (4D) without ionizing radiation. We report the first results of online 4D ultrasound-guided MLC tracking in a phantom. Methods: A real-time tracking framework was installed on a 4D ultrasound station (Vivid7 dimension, GE) and used to detect a 2mm spherical lead marker inside a water tank. The volumetric frame rate was 21.3Hz (47ms). The marker was rigidly attached to a motion stage programmed to reproduce nine tumor trajectories (five prostate, four lung). The 3D marker position from ultrasound was used for real-time MLC aperture adaption. The tracking system latency was measured and compensated by prediction for lung trajectories. To measure geometric accuracy, anterior and lateral conformal fields with 10cm circular aperture were delivered for each trajectory. The tracking error was measured as the difference between marker position and MLC aperture in continuous portal imaging. For dosimetric evaluation, 358° VMAT fields were delivered to a biplanar diode array dosimeter using the same trajectories. Dose measurements with and without MLC tracking were compared to a static reference dose using a 3%/3 mm γ-test. Results: The tracking system latency was 170ms. The mean root-mean-square tracking error was 1.01mm (0.75mm prostate, 1.33mm lung). Tracking reduced the mean γ-failure rate from 13.9% to 4.6% for prostate and from 21.8% to 0.6% for lung with high-modulation VMAT plans and from 5% (prostate) and 18% (lung) to 0% with low modulation. Conclusion: Real-time ultrasound tracking was successfully integrated with MLC tracking for the first time and showed similar accuracy and latency as other methods while holding the potential to measure target motion non-invasively. SI was supported by the Graduate School for Computing in Medicine and Life Science, German Excellence Initiative [grant DFG GSC 235/1].

Extraction of 3D freeform surfaces as visual landmarks for real-time tracking

This work presents a system for the generation of a free-form surface model from video sequences. Although any single centered camera can be applied in the proposed system the approach is demonstrated using fish-eye lenses because of their good properties for tracking. The system is designed to function automatically and to be flexible with respect to size and shape of the reconstructed scene. To minimize geometric assumptions a statistic fusion of dense depth maps is utilized. Special attention is payed to the necessary rectification of the spherical images and the resulting iso-disparity surfaces, which can be exploited in the fusion approach. Before dense depth estimation can be performed the cameras’ pose parameters are extracted by means of a structure-from-motion (SfM) scheme. In this respect automation of the system is achieved by thorough decision model based on robust statistics and error propagation of projective measurement uncertainties. This leads to a scene-independent set of only a few parameters. All system components are formulated in a general way, making it possible to cope with any single centered projection model, in particular with spherical cameras. In using wide field-of-view cameras the presented system is able to reliably retrieve poses and consistently reconstruct large scenes. A textured triangle mesh constructed on basis of the scene’s reconstructed depth, makes the system’s results suitable to function as reference models in a GPU driven analysis-by-synthesis framework for real-time tracking.