Track, then Decide: Category-Agnostic Vision-based Multi-Object Tracking

The most common paradigm for vision-based multi-object tracking is tracking-by-detection, due to the availability of reliable detectors for several important object categories such as cars and pedestrians. However, future mobile systems will need a capability to cope with rich human-made environments, in which obtaining detectors for every possible object category would be infeasible. In this paper, we propose a model-free multi-object tracking approach that uses a category-agnostic image segmentation method to track objects. We present an efficient segmentation mask-based tracker which associates pixel-precise masks reported by the segmentation. Our approach can utilize semantic information whenever it is available for classifying objects at the track level, while retaining the capability to track generic unknown objects in the absence of such information. We demonstrate experimentally that our approach achieves performance comparable to state-of-the-art tracking-by-detection methods for popular object categories such as cars and pedestrians. Additionally, we show that the proposed method can discover and robustly track a large variety of other objects.Comment: ICRA'18 submissio

Universal flow-density relation of single-file bicycle, pedestrian and car motion

The relation between flow and density is an essential quantitative characteristic to describe the efficiency of traffic systems. We have performed experiments with single-file motion of bicycles and compare the results with previous studies for car and pedestrian motion in similar setups. In the space-time diagrams we observe three different states of motion (free flow state, jammed state and stop-and-go waves) in all these systems. Despite of their obvious differences they are described by a universal fundamental diagram after proper rescaling of space and time which takes into account the size and free velocity of the three kinds of agents. This indicates that the similarities between the systems go deeper than expected.Comment: 5 pages, 5 figure

Updating radical ring-opening polymerisation of cyclic ketene acetals from synthesis to degradation

Radical ring-opening polymerisation (RROP) of cyclic ketene acetals (CKAs) has gained momentum as it yields polyesters as biodegradable polymers from a radical polymerisation. In order to advance the polymerisation, some of its major limitations were addressed in the research presented, focussing on the four mainly used CKAs in modern research on RROP. Monomer synthesis has been updated towards a cobalt/TMSCl-based system that was performed reliably on several monomers at room temperature. Calculations using the density functional theory (DFT) revealed that the ring-opening step is energetically hampered in comparison to a ring-retaining reaction, which explained the challenges faced to promote the ring-opening reaction. Higher molecular weights up to four times the values reached by thermally initiated polymerisation were obtained by exploiting UV light and ultrasound as alternative methods to facilitate the polymerisation. The reaction procedure also influenced thermal properties of the polymers, which in turn affected the enzymatic degradation of nanoparticles based on those polymers. Altogether, the present study offers a holistic update to enhance the RROP of CKAs

Comparative Analysis of Pedestrian, Bicycle and Car Traffic Moving in Circuits

In this study, we provide results of controlled experiments of single file bicycle movement on a circuit. We compare the fundamental characteristics of bicycle traffic with that of car and pedestrian traffic, which have been studied extensively in previous research under similar condition. From the comparison of the time-space diagrams of these three one-dimensional traffic flows, different states of motion (free flow state, the jammed state and stop-and-go waves) can be observed in all these systems. The fundamental diagrams are compared in two different ways. Without considering the size and free velocity of these three kinds of objects, the data points occupy different density ranges in the diagram. However, when we use the concept of scaling by considering the free velocity and size of the moving objects, the fundamental diagrams show the same structure and values. This implies that the transport properties in these three different types of single file traffic flow could be unified in a certain range by simple scaling. These results provide insights into the dynamics but also may be relevant for the improvement of mixed traffic systems

Robust Marker-Based Tracking for Measuring Crowd Dynamics

We present a system to conduct laboratory experiments with thousands of pedestrians. Each participant is equipped with an individual marker to enable us to perform precise tracking and identification. We propose a novel rotation invariant marker design which guarantees a minimal Hamming distance between all used codes. This increases the robustness of pedestrian identification. We present an algorithm to detect these markers, and to track them through a camera network. With our system we are able to capture the movement of the participants in great detail, resulting in precise trajectories for thousands of pedestrians. The acquired data is of great interest in the field of pedestrian dynamics. It can also potentially help to improve multi-target tracking approaches, by allowing better insights into the behaviour of crowds

Universalities in fundamental diagrams of cars, bicycles and pedestrians

Since the pioneering work of Greenshields the fundamental diagram is used to characterize and describe the performance of traffic systems. During the last years the discussion and growing data base revealed the influence of human factors, traffic types or ways of measurements on this relation. The manifoldness of influences is important and relevant for applications but moves the discussion away from the main feature characterizing the transport properties of traffic systems. We focus again on the main feature by comparing the fundamental diagram of cars, bicycles and pedestrians moving in a row in a course with periodic boundaries. The underlying data are collected by three experiments, performed under well controlled laboratory conditions [5-9]. In all experiments the setup in combination with technical equipment or methods of computer vision allowed to determine the trajectories with high precision. The trajectories visualized by space-time diagrams show three different states of motion (free flow state, jammed state and stop-and-go waves) in all these systems. Obviously the values of speed, density and flow of these three systems cover different ranges. However, after a simple rescaling of the velocity by the free speed and of the density by the length of the agents the fundamental diagrams conform regarding the position and height of the capacity. This indicates that the similarities between the systems go deeper than expected and offers the possibility of a universal model for heterogeneous traffic systems