The development of new electric traction machines is a time-consuming process as it involves intensive testing on motor test benches. Machine-Learning-empowered monitoring offers the opportunity to anticipate costly failures early and hence reduce development time. However, machine learning (ML) for process monitoring requires large amounts of training data, especially as the targeted fault states are scarce and yet diverse in their appearances.Therefore, we propose to use synthetic time series data to leverage the high cost of acquiring training data from experiments in real test benches. In this article, we present a novel scheme to generate synthetic data based on a sub-dimensional time series representation. We introduce a highly flexible model by mapping the data to a latent representation and approximating the latent data distribution by a Gaussian Mixture Model. In addition, we propose the Fréchet InceptionTime Distance (FITD) as a new distance measure to evaluate the generated data. It allows extracting characteristics at different scales by using multiple kernel sizes. In this way, we ensure that the synthesized data contains characteristics similar to those present in the real data. In our experiment, we train two types of fault detectors, one based on real data of a motor test bench and the other based on synthetic data. We also consider employing fault-aware conditional architectures to generate training data for different fault types explicitly. Our final results show that using synthesized data in the training process increases the performance in terms of classification accuracy score (CAS) up to 29%.

Abstract In transductive active learning, the goal is to determine the correct labels for an unlabeled, known dataset. Therefore, we can either ask an oracle to provide the right label at some cost or use the prediction of a classifier which we train on the labels acquired so far. In contrast, the commonly used (inductive) active learning aims to select instances for labeling out of the unlabeled set to create a generalized classifier, which will be deployed on unknown data. This article formally defines the transductive setting and shows that it requires new solutions. Additionally, we formalize the theoretically cost-optimal stopping point for the transductive scenario. Building upon the probabilistic active learning framework, we propose a new transductive selection strategy that includes a stopping criterion and show its superiority.

Radar-based road user detection is an important topic in the context of autonomous driving applications. The resolution of conventional automotive radar sensors results in a sparse data representation which is tough to refine during subsequent signal processing. On the other hand, a new sensor generation is waiting in the wings for its application in this challenging field. In this article, two sensors of different radar generations are evaluated against each other. The evaluation criterion is the performance on moving road user object detection and classification tasks. To this end, two data sets originating from an off-the-shelf radar and a high resolution next generation radar are compared. Special attention is given on how the two data sets are assembled in order to make them comparable. The utilized object detector consists of a clustering algorithm, a feature extraction module, and a recurrent neural network ensemble for classification. For the assessment, all components are evaluated both individually and, for the first time, as a whole. This allows for indicating where overall performance improvements have their origin in the pipeline. Furthermore, the generalization capabilities of both data sets are evaluated and important comparison metrics for automotive radar object detection are discussed. Results show clear benefits of the next generation radar. Interestingly, those benefits do not actually occur due to better performance at the classification stage, but rather because of the vast improvements at the clustering stage.

In near future, vulnerable road users (VRUs) such as cyclists and pedestrians will be equipped with smart devices and wearables which are capable to communicate with intelligent vehicles and other traffic participants. Road users are then able to cooperate on different levels, such as in cooperative intention detection for advanced VRU protection. Smart devices can be used to detect intentions, e.g., an occluded cyclist intending to cross the road, to warn vehicles of VRUs, and prevent potential collisions. This article presents a human activity recognition approach to detect the starting movement of cyclists wearing smart devices. We propose a novel two-stage feature selection procedure using a score specialized for robust starting detection reducing the false positive detections and leading to understandable and interpretable features. The detection is modelled as a classification problem and realized by means of a machine learning classifier. We introduce an auxiliary class, that models starting movements and allows to integrate early movement indicators, i.e., body part movements indicating future behaviour. In this way we improve the robustness and reduce the detection time of the classifier. Our empirical studies with real-world data originating from experiments which involve 49 test subjects and consists of 84 starting motions show that we are able to detect the starting movements early. Our approach reaches an F1-score of 67 % within 0.33 s after the first movement of the bicycle wheel. Investigations concerning the device wearing location show that for devices worn in the trouser pocket the detector has less false detections and detects starting movements faster on average. % compared to reference detector involving all wearing locations. We found that we can further improve the results when we train distinct classifiers for different wearing locations. In this case we reach an F1-score of 94 % with a mean detection time of 0.34 s for the device worn in the trouser pocket.

If knowledge such as classification rules are extracted from sample data in a distributed way, it may be necessary to combine or fuse these rules. In a conventional approach this would typically be done either by combining the classifiers' outputs (e.g., in form of a classifier ensemble) or by combining the sets of classification rules (e.g., by weighting them individually). In this paper, we introduce a new way of fusing classifiers at the level of parameters of classification rules. This technique is based on the use of probabilistic generative classifiers using multinomial distributions for categorical input dimensions and multivariate normal distributions for the continuous ones. That means, we have distributions such as Dirichlet or normal-Wishart distributions over parameters of the classifier. We refer to these distributions as hyperdistributions or second-order distributions. We show that fusing two (or more) classifiers can be done by multiplying the hyperdistributions of the parameters and derive simple formulas for that task. Properties of this new approach are demonstrated with a few experiments. The main advantage of this fusion approach is that the hyperdistributions are retained throughout the fusion process. Thus, the fused components may, for example, be used in subsequent training steps (online training).

In this article, we introduce and investigate 3DS, a novel selection strategy for pool-based active training of a generative classifier, namely CMM (classifier based on a probabilistic mixture model). Such a generative classifier aims at modeling the processes underlying the “generation” of the data. The strategy 3DS considers the distance of samples to the decision boundary, the density in regions where samples are selected, and the diversity of samples in the query set that are chosen for labeling, e.g., by a human domain expert. The combination of the three measures in 3DS is adaptive in the sense that the weights of the distance and the density measure depend on the uniqueness of the classification. With nine benchmark data sets it is shown that 3DS outperforms a random selection strategy (baseline method), a pure closest sampling approach, ITDS (information theoretic diversity sampling), DWUS (density-weighted uncertainty sampling), DUAL (dual strategy for active learning), and PBAC (prototype based active learning) regarding evaluation criteria such as ranked performance based on classification accuracy, number of labeled samples (data utilization), and learning speed assessed by the area under the learning curve.

In this article, we provide a new technique for temporal data mining which is based on classification rules that can easily be understood by human domain experts. Basically, time series are decomposed into short segments, and short-term trends of the time series within the segments (e.g., average, slope, and curvature) are described by means of polynomial models. Then, the classifiers assess short sequences of trends in subsequent segments with their rule premises. The conclusions gradually assign an input to a class. As the classifier is a generative model of the processes from which the time series are assumed to originate, anomalies can be detected, too. Segmentation and piecewise polynomial modeling are done extremely fast in only one pass over the time series. Thus, the approach is applicable to problems with harsh timing constraints. We lay the theoretical foundations for this classifier, including a new distance measure for time series and a new technique to construct a dynamic classifier from a static one, and demonstrate its properties by means of various benchmark time series, for example, Lorenz attractor time series, energy consumption in a building, or ECG data.

Experts have important qualitative knowledge about interrelations between more or less abstract concepts in an application area. However, the knowledge of a single expert is typically quite uncertain (e.g., incomplete or imprecise). By fusing the knowledge of several experts it would be possible to obtain more certain and, therefore, more valuable knowledge. Conventional systems for knowledge discovery (KD) and data mining (DM) have the ability to extract valid rules from huge data sets. These rules describe dependencies between attributes and classes in a quantitative way, for instance. By fusing this kind of knowledge with the combined, qualitative knowledge of several experts it would be possible to obtain more comprehensive knowledge about an application area. In this article, we propose a concept for a new KD & DM technique based on computational intelligence: collaborative knowledge discovery (CKD). These techniques combines the uncertain knowledge of several experts using methods based on Dempster-Shafer theory. The combined human knowledge is again fused with automatically extracted, well interpretable knowledge (fuzzy rules embedded in a radial basis function neural network) of a conventional KD system. Thus, a CKD system not only acquires more comprehensive knowledge, but also experience (knowledge about knowledge), meaning that it is able to explain automatically extracted rules to the human experts and to assess the interestingness (e.g., novelty or utility) of these rules. This can be done by adapting inference mechanisms from the field of probabilistic argumentation systems. A CKD system will comprise self-awareness mechanisms (it must know what it knows) as well as environment-awareness mechanisms (it must know what human experts know or what they want to now). In order to reduce the effort for knowledge acquisition, a CKD system must learn (pro-)actively. There are many application areas for such CKD systems, e.g., in the field of technical data mining (quality control, process monitoring, etc.)

Driver assistance systems are the key technology to improve traffic safety and lower the number of deadly accidents. Direct communication between cars will further enhance this field of driver safety. In the context of foresighted driving, Bayesian networks can be used to determine a traffic situation at the current position of a car. Communicating this awareness for the current time and position will help other traffic participants. However, situations change dynamically and cars cannot trust all the information provided by other cars over time. Reasoning with this information is difficult as Bayesian networks cannot use spatial and temporal data in an appropriate way. This article outlines the spatial and temporal problems in predictive driver assistance and demonstrates how they can be solved by considering spatial and temporal influences by applying weighting techniques. The pre-processed information is utilized by a Bayesian network for further refinement. Thus, the proposed approach enables the detection and correct prediction of traffic situations. The approach is evaluated by predicting hazardous rain fields in a car by means of information received from other cars