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Legged robots have demonstrated high potential when dealing with rough terrain, for which an efficient motion planner becomes crucial. This article presents a novel approach for quadrupedal robot motion planning on rough terrain that is both conceptually straightforward and computationally efficient. Implementing the concept of workspace constitutes the cornerstone of this method: both body poses and swing-leg footholds are chosen within their corresponding workspace. A novel approach called the “cross-diagonal method” is developed to facilitate the search for new body poses. Based on the obtained body pose, the foothold for a swing leg selected within its foot workspace satisfies the reachability constraint automatically. The proposed motion planning scheme is integrated with an elevation mapping module and a state estimation module, enabling quadrupedal robots to travel through uneven terrains with high efficiency. The significance of this work is validated through simulation and physical experiments with a quadrupedal robot, which achieves high success rates in overcoming difficult terrains without prior knowledge of the environment. This approach offers the advantages of high computational efficiency, simplicity, and adaptability to different types of terrain, making it a promising solution for real-world applications.

Tropical disturbances play an important role in the formation of tropical cyclones (TCs), but their climate characteristics are still poorly understood. The present study investigated the characteristics of tropical disturbances over the western North Pacific (WNP) for the period 1965–2020 using the reanalysis datasets. An algorithm based on the threshold of synoptic-scale vorticity and convection was developed to identify and track tropical disturbances. Approximately 116 tropical disturbances were detected primitively in the WNP from June to November each year, and about 13.1% of them subsequently developed into TCs. These developing disturbances contributed to the formation of 80.9% TCs in the WNP. Compared with nondeveloping disturbances, the position of developing disturbances is more eastward and southward, whereas the majority of their lifetimes and propagation speeds are similar. The annual numbers of developing disturbances exhibit significant interannual (interdecadal) variability. The percentage of TCs associated with disturbances also experiences a significant inverse interdecadal relationship with the number of TC genesis in the WNP, indicating that the formation probability of TCs is inconsistent with the transition probability from disturbances to TCs. In addition, the long-term trends of developing and nondeveloping disturbances suggest that global warming might be responsible for more tropical disturbances in the WNP instead of higher transition probability from disturbances to TCs.