Vision-and-Language Navigation (VLN) requires an agent to follow given instructions to navigate. Despite the significant progress, the model trained on seen environments has a performance drop on unseen environments due to distribution shift. To improve the generalization, existing method attempts to apply test-time adaptation to VLN. However, it needs to access the training data and all testing data for updating the model before inference. The setting is not suitable for the real application because it is hard for the agent to access training data and all testing data when the agent is applied in a new environment. In this paper, we consider a more practical setting with source-free and online-inference test-time adaption. In other words, the model can only access one testing sample for test-time adaptation. In this setting, the model may suffer from catastrophic forgetting of the learned knowledge and unstable parameter update issues. To solve these challenges, we propose an elastic adaptation model (EAM) that consists of an auxiliary decision model and a sample replay mechanism. We use the online testing samples to adapt the auxiliary decision model to new environments, which cooperates with the frozen original model to make better action decisions. The sample replay mechanism stores the historical testing samples to make the adaptation process more stable. Our method is model-agnostic and is effortless to be applied to most existing methods. Experimental results show that our method achieves stable performance improvement based on three existing methods on three VLN benchmark datasets.

Getting robots to navigate to multiple objects autonomously is essential yet difficult in robot applications. One of the key challenges is how to explore environments efficiently with camera sensors only. Existing navigation methods mainly focus on fixed cameras and few attempts have been made to navigate with active cameras. As a result, the agent may take a very long time to perceive the environment due to limited camera scope. In contrast, humans typically gain a larger field of view by looking around for a better perception of the environment. How to make robots perceive the environment as efficiently as humans is a fundamental problem in robotics. In this paper, we consider navigating to multiple objects more efficiently with active cameras. Specifically, we cast moving camera to a Markov Decision Process and reformulate the active camera problem as a reinforcement learning problem. However, we have to address two new challenges: 1) how to learn a good camera policy in complex environments and 2) how to coordinate it with the navigation policy. To address these, we carefully design a reward function to encourage the agent to explore more areas by moving camera actively. Moreover, we exploit human experience to infer a rule-based camera action to guide the learning process. Last, to better coordinate two kinds of policies, the camera policy takes navigation actions into account when making camera moving decisions. Experimental results show our camera policy consistently improves the performance of multi-object navigation over four baselines on two datasets.

We address a practical yet challenging problem of training robot agents to navigate in an environment following a path described by some language instructions. The instructions often contain descriptions of objects in the environment. To achieve accurate and efficient navigation, it is critical to build a map that accurately represents both spatial location and the semantic information of the environment objects. However, enabling a robot to build a map that well represents the environment is extremely challenging as the environment often involves diverse objects with various attributes. In this paper, we propose a multi-granularity map, which contains both object fine-grained details (\eg, color, texture) and semantic classes, to represent objects more comprehensively. Moreover, we propose a weakly-supervised auxiliary task, which requires the agent to localize instruction-relevant objects on the map. Through this task, the agent not only learns to localize the instruction-relevant objects for navigation but also is encouraged to learn a better map representation that reveals object information. We then feed the learned map and instruction to a waypoint predictor to determine the next navigation goal. Experimental results show our method outperforms the state-of-the-art by 4.0% and 4.6% w.r.t. success rate both in seen and unseen environments, respectively on VLN-CE dataset. The code is available at https://github.com/PeihaoChen/WS-MGMap.