Robot localization systems typically assume that the environment is static, ignoring the dynamics inherent in most real-world settings. Corresponding scenarios include households, offices, warehouses and parking lots, where the location of certain objects such as goods, furniture or cars can change over time. These changes typically lead to inconsistent observations with respect to previously learned maps and thus decrease the localization accuracy or even prevent the robot from globally localizing itself. In this paper we present a sound probabilistic approach to lifelong localization in changing environments using a combination of a Rao-Blackwellized particle filter with a hidden Markov model. By exploiting several properties of this model, we obtain a highly efficient map management approach for dynamic environments, which makes it feasible to run our algorithm online. Extensive experiments with a real robot in a dynamically changing environment demonstrate that our algorithm reliably adapts to changes in the environment and also outperforms the popular Monte-Carlo localization approach.

To act intelligently in dynamic environments, a system must understand the current situation it is involved in at any given time. This requires dealing with temporal context, handling multiple and ambiguous interpretations, and accounting for various sources of uncertainty. In this paper we propose a probabilistic approach to modeling and recognizing situations. We define a situation as a distribution over sequences of states that have some meaningful interpretation. Each situation is characterized by an individual hidden Markov model that describes the corresponding distribution. In particular, we consider typical traffic scenarios and describe how our framework can be used to model and track different situations while they are evolving. The approach was evaluated experimentally in vehicular traffic scenarios using real and simulated data. The results show that our system is able to recognize and track multiple situation instances in parallel and make sensible decisions between competing hypotheses. Additionally, we show that our models can be used for predicting the position of the tracked vehicles.

Abstract-Accurate and robust localization is essential for the successful navigation of autonomous mobile robots. The majority of existing localization approaches, however, is based on the assumption that the environment is static which does not hold for most practical application domains. In this paper, we present a localization framework that can robustly track a robot's pose even in non-static environments. Our approach keeps track of the observations caused by unexpected objects in the environment using temporary local maps. It relies both on these temporary local maps and on a reference map of the environment for estimating the pose of the robot. Experimental results demonstrate that by exploiting the observations caused by unexpected objects our approach outperforms standard localization methods for static environments.

Abstract-Robust and reliable localization is a fundamental prerequisite for many applications of mobile robots. Although there exist many solutions to the localization problem, structurally symmetrical or featureless environments can prevent different locations from being distinguishable given the data obtained with the robot's sensors. Such ambiguities typically make localization approaches more likely to fail. In this paper, we investigate how artificial landmarks can be utilized to reduce the ambiguity in the environment. We present a practical approach to compute a configuration of indistinguishable landmarks that decreases the overall ambiguity and thus increases the robustness of the localization process. We evaluate our approach in different environments based on real data and in simulation. Our results demonstrate that our approach improves the localization performance of the robot and outperforms other landmark selection approaches.

The majority of existing approaches to mobile robot mapping assumes that the world is static, which is generally not justified in real-world applications. However, in many navigation tasks including trajectory planning, surveillance, and coverage, accurate maps are essential for the effective behavior of the robot.  In this paper we present a probabilistic grid-based approach for modeling changing environments. Our method represents both, the occupancy and its changes in the corresponding area where the dynamics are characterized by the state transition probabilities of a Hidden Markov Model. We apply an offline and an online technique to learn the parameters from observed data. The advantage of the online approach is that it can dynamically adapt the parameters and at the same time does not require storing the complete observation sequences.  Experimental results obtained with data acquired by real robots demonstrate that our model is well-suited for representing changing environments. Further results show that our technique can be used to substantially improve the effectiveness of path planning procedures.