A Review on Environment-Adaptive Gait Planning for Semiautonomous Lower Limb Exoskeletons

Recent years have witnessed a growing interest in lower limb exoskeletons (LLEs) designed to restore walking capabilities for individuals with motor impairments. Currently, the research community faces the challenge of enhancing the translational impact of this technology by proposing solutions to move from laboratory and clinical settings to daily life scenarios. In this context, the topic of environment-adaptive gait planning (EAGP) is of particular interest and importance. EAGP refers to the ability of LLEs to assist in walking on various terrains (e.g., stairs and slopes) and under different conditions (e.g., the presence of obstacles and uneven ground) by adapting their behavior according to the context. However, the proliferation of publications has led to a general lack of convergence within the scientific community toward a common definition of this research topic. Therefore, this article proposes a review of EAGP for LLEs. The objectives are to: 1) provide a clear definition of EAGP, highlighting its main components and characteristics; 2) propose a taxonomy for classifying the most frequently used techniques in the state of the art; and 3) conduct a comprehensive survey of the literature, situating each article within the proposed taxonomy. In addition, we identify the most urgent future challenges toward the development of more autonomous LLEs.