RESEARCH ARTICLE Girish Sudhir MODAK, Manmohan Manikrao BHOOMKAR Innovative stair climber using associated wheels © Higher Education Press and Springer-Verlag Berlin Heidelberg 2016 Abstract The study proposes an innovative and com- pletely new but low-cost configuration of a platform that can easily climb stairs. This platform serves the purpose of a chassis. Different versions, such as staircase-climbing wheelchair or staircase-climbing trolley for material transferring, can be derived depending on the structure built on the platform. The driving wheels have a shape that completely matches with the profile of the steps. Complex components are eliminated. Thus, this platform is conveniently applicable in the configurations useful for climbing staircases. Keywords stair-climbing platform, matching wheels, impaired mobility, affordable configuration 1 Introduction The old constructions in the heavily crowded areas of cities do not have elevators. The task of climbing stairs is a major challenge for physically handicapped people or for elderly people because of the age-dependent impaired mobility. Transferring a material from the ground floor to the upper levels is another challenge even for a normal person living in old and high buildings which do not have elevators. Hence, a platform for climbing steps of the stairs is a major requirement at least in underdeveloped regions. The platform serves the purpose of a chassis. Different versions, such as staircase-climbing wheelchair or stair- case-climbing trolley for material transferring, can be derived depending on the object built on the platform. These platforms are also useful in the buildings with elevators, particularly when power backup is unavailable. Several rehabilitation devices are currently available or in development. They are critically reviewed as follows. The design for a wheelchair [1] for locomotion on an uneven terrain attempts to combine the advantages of the legged locomotion (e.g., versatility and adaptability) with those of the wheeled locomotion (e.g., reliability and superior stability). The experimental prototype is equipped with six direct current (DC) motors, position and force sensors, and an on- board computer. It weighs 28.2 kg (≈ 62 lb) without the batteries and controller, and it can climb 30 cm (≈1 ft) curb with a payload of 68.2 kg (≈150 lb). The powered wheels are used to navigate a flat surface as in a conventional wheelchair, whereas the legs and wheels are used to traverse an uneven terrain. In addition to enhancing the mobility of the chair, the legs provide additional traction on unprepared and slippery surfaces. The controller uses foot force information in coordinating the actuators of the legs and wheels to minimize the tendency of a slip. The hybrid system is more attractive than a walking chair because it relies on a wheeled locomotion, which is established to be reliable and safe. The legs can be used as crutches when needed. The legs are not used to support the entire weight of the chair; thus, the motors, controllers, and legs can be also made compact as needed. The legs can be used as manipulators to push open doors, reach for objects, and move obstacles out of the way when they are not required for support. They can be also tucked away below the armrest to make them inconspicuous when they are not needed. However, unlike a legged system, the hybrid chair cannot move without wheels. The reduced complexity, low cost, and improved reliability and safety result in the loss in mobility. An important design consideration is the aesthetics of the design and consumer acceptance. The disadvantage of employing a fundamentally different method for locomotion is that the user may feel conspicuous in using such chair. Although this “distract- ibility factor” depends largely on the environment and society, making any design “unrobot-like” is necessary. The designs proposed by Lawn et al. [2–4] are acceptable; however, they are yet to be converted in actual products. Moreles et al. [5] proposed a new prototype of the design along with the validation; however, the key parameters in that analysis are not discussed adequately. Fang et al. [6] proposed a design of the mechanism and the Received October 4, 2015; accepted November 9, 2015 Girish Sudhir MODAK (✉), Manmohan Manikrao BHOOMKAR Department of Mechanical Engineering, Amrutvahini College of Engineering, Sangamner 422608, India E-mail: gsmodak@yahoo.com Front. Mech. Eng. DOI 10.1007/s11465-016-0374-1