Extrinsic calibration is a fundamental step in sensor fusion systems. However, existing methods often lack generalization capabilities when facing diverse hardware configurations, sensor poses, and environmental conditions, hindering their large-scale deployment. To address this limitation, we propose a general extrinsic calibration method, CalibWorkflow. Our core innovation lies in positioning multimodal large language models (MLLMs) as ''visual guides'' for the calibration process, leveraging their powerful vision-language understanding capabilities to guide parameter search and refinement. This reliance on visual scene understanding, rather than specific geometric features or sensor characteristics, enables the method to generalize effectively across diverse hardware and environmental conditions. Specifically, CalibWorkflow employs a three-stage calibration pipeline: initial parameter search, coarse optimization, and fine optimization. First, it utilizes the MLLM to assess the visual consistency between the projected point cloud and the image, rapidly determining an initial range for the extrinsic parameters. Next, the MLLM serves as a differential evaluator, giving simple ''better'' or ''worse'' feedback on parameter changes to guide the search through the parameter space. Finally, the method refines the calibration by matching edge features and performing non-linear optimization. Extensive experiments are conducted across six diverse scenarios and four heterogeneous sensor combinations. CalibWorkflow achieves state-of-the-art sub-degree and centimeter-level accuracy on four datasets and demonstrates highly competitive performance on others. These results thoroughly validate the generalization and robustness when facing various scenarios. Codes will be available.

Robot navigation using deep reinforcement learning (DRL) has shown great potential in improving the performance of mobile robots. Nevertheless, most existing DRL-based navigation methods primarily focus on training a policy that directly commands the robot with low-level controls, like linear and angular velocities, which leads to unstable speeds and unsmooth trajectories of the robot during the long-term execution. An alternative method is to train a DRL policy that outputs the navigation path directly. Then the robot can follow the generated path smoothly using sophisticated velocity-planning and path-following controllers, whose parameters are specified according to the hardware platform. However, two roadblocks arise for training a DRL policy that outputs paths: (1) The action space for potential paths often involves higher dimensions comparing to low-level commands, which increases the difficulties of training; (2) It takes multiple time steps to track a path instead of a single time step, which requires the path to predicate the interactions of the robot w.r.t. the dynamic environment in multiple time steps. This, in turn, amplifies the challenges associated with training. In response to these challenges, we propose PathRL, a novel DRL method that trains the policy to generate the navigation path for the robot. Specifically, we employ specific action space discretization techniques and tailored state space representation methods to address the associated challenges. Curriculum learning is employed to expedite the training process, while the reward function also takes into account the smooth transition between adjacent paths. In our experiments, PathRL achieves better success rates and reduces angular rotation variability compared to other DRL navigation methods, facilitating stable and smooth robot movement. We demonstrate the competitive edge of PathRL in both real-world scenarios and multiple challenging simulation environments.

The conditional diffusion model has been demonstrated as an efficient tool for learning robot policies, owing to its advancement to accurately model the conditional distribution of policies. The intricate nature of real-world scenarios, characterized by dynamic obstacles and maze-like structures, underscores the complexity of robot local navigation decision-making as a conditional distribution problem. Nevertheless, leveraging the diffusion model for robot local navigation is not trivial and encounters several under-explored challenges: (1) Data Urgency The complex conditional distribution in local navigation needs training data to include diverse policy in diverse real-world scenarios; (2) Myopic Observation Due to the diversity of the perception scenarios, diffusion decisions based on the local perspective of robots may prove suboptimal for completing the entire task, as they often lack foresight. In certain scenarios requiring detours, the robot may become trapped. To address these issues, our approach begins with an exploration of a diverse data generation mechanism that encompasses multiple agents exhibiting distinct preferences through target selection informed by integrated global-local insights. Then, based on this diverse training data, a diffusion agent is obtained, capable of excellent collision avoidance in diverse scenarios. Subsequently, we augment our Local Diffusion Planner, also known as LDP by incorporating global observations in a lightweight manner. This enhancement broadens the observational scope of LDP, effectively mitigating the risk of becoming ensnared in local optima and promoting more robust navigational decisions. Our experimental results demonstrated that the LDP outperforms other baseline algorithms in navigation performance, exhibiting enhanced robustness across diverse scenarios with different policy preferences and superior generalization capabilities for unseen scenarios. Moreover, we highlighted the competitive advantage of the LDP within real-world settings.