Taxonomy of Stair-Climbing Mechanisms for Wheelchairs

Abstract Autonomous climbing mechanisms have been present for over a couple of decades now, and it has been a part of various equipment such as wheelchairs, agricultural robots, rescue robots, etc. A centralized database of all existing stair-climbing mechanisms for wheelchairs can aid in selecting the appropriate one for the subjective terrain and/or finalizing the direction of additional research and design. This systematic literature review on autonomous climbing mechanisms for applications such as crossing obstacles, stair climbing, as well as climbing over/onto higher platforms, etc. assesses parameters such as climbing efficiency, power efficiency, stability, etc. This also initiates a centralized all-inclusive classification for existent robotic climbing mechanisms. By identifying commonly used components such as different ‘link and joint’ types as well as the nature of motion performed by the mechanism while climbing, different mechanisms are broken down into categories such as ‘Wheeled, Legged, Hybrid’. These are further broken down into ‘2-spoked, 3-spoked, etc… up to n-spoked and ∞-spoked’ with consideration to the parts interfering with the obstacle surfaces. Additionally, based on the nature of motion, such as continuous, periodic intermittent, sporadic, and hybrid, another aspect which is the nature of resultant motion is added to the classification. The control systems Used for different mechanisms are also a matter of concern for this review as it becomes a differentiation factor while categorizing into subdivisions under a hierarchical system. Some mechanisms can be controlled numerically, some receive their limitations on movement based on electronic signals received from the set of sensors used onboard, while some of them get limited by mechanical stoppers or limiters added from the early design stage. With the increasing acceptance and appreciation of robotic equipment in the rescue and safety section, the evaluation of climbing mechanisms for the availability of fail-safes and recovery majors is also considered a factor. This review introduces a categorical structure to the classification of autonomous climbing mechanisms which can be used efficiently while selecting a climbing mechanism for a given set of requirements, or tasks.