Robots still struggle to dynamically traverse complex 3D terrain with many large obstacles, an ability required for many critical applications. Body–obstacle interaction is often inevitable and induces perturbation and uncertainty in motion that challenges closed-form dynamic modeling. Here, inspired by recent discovery of a terradynamic streamlined shape, we studied how two body shapes interacting with obstacles affect turning and pitching motions of an open-loop multi-legged robot and cockroaches during dynamic locomotion. With a common cuboidal body, the robot was attracted towards obstacles, resulting in pitching up and flipping-over. By contrast, with an elliptical body, the robot was repelled by obstacles and readily traversed. The animal displayed qualitatively similar turning and pitching motions induced by these two body shapes. However, unlike the cuboidal robot, the cuboidal animal was capable of escaping obstacle attraction and subsequent high pitching and flipping over, which inspired us to develop an empirical pitch-and-turn strategy for cuboidal robots. Considering the similarity of our self-propelled body–obstacle interaction with part–feeder interaction in robotic part manipulation, we developed a quasi-static potential energy landscape model to explain the dependence of dynamic locomotion on body shape. Our experimental and modeling results also demonstrated that obstacle attraction or repulsion is an inherent property of locomotor body shape and insensitive to obstacle geometry and size. Our study expands the concept and usefulness of terradynamic shapes for passive control of robot locomotion to traverse large obstacles using physical interaction. Our study is also a step in establishing an energy landscape approach to locomotor transitions.
Ulnar nerve injury (UNI) is not uncommon and often results in incomplete motor recovery after the initial nerve repair and requires secondary functional reconstruction. To clarify the prognosis and predicting factor of UNI, and if it is reasonable to wait after the initial repair, a systematic literature review from PubMed computerized literature database and Google scholar was performed. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) checklist and guidelines were followed to develop the search protocol for this literature review. Two reviewers independently assessed titles, abstracts, and full-text articles, and a third reviewer resolved any disagreements. Seventeen articles with 260 cases were found with sufficient data and enough follow-up. After multiple logistic regression, age, injury level, gap of lesion, and delayed time to surgery were significant prognostic factors in UNI. If considering only high-level injuries (injury at or above proximal forearm), age became the only predicting factor. In cases with likely poor prognosis, their motor recovery tends to be unsatisfactory, and observation for months after the initial repair might not be reasonable. Other surgical interventions such as early nerve transfer may be an option to improve the outcome.
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