Development of an Optimized Stair-Climbing Mechanism Using Parametric Curved Wheels Inspired by Human Foot Strides on Flat Stairs

This research presents a novel stair-climbing wheelchair mechanism using parametric curved tri-spoke wheels inspired by human foot gait patterns. The design addresses the accessibility challenges faced by wheelchair users in India, where 26.8 million disabled persons struggle with stair navigation due to inadequate infrastructure. The curved tri-spoke wheel system enables multimodal operation, functioning on both flat surfaces and stairs through a retractable mechanism. The wheel design was parametrically optimized using kinematic modeling, multibody simulations, and robotic prototype validation. Key design parameters include rotation angle β = 70°, rotation distance d = 90mm, and parent circle radius of 160-180mm, optimized for IS 456-2000 standard staircase dimensions (300mm tread, 150mm riser). The mechanism mimics human foot stance phases (heel strike, mid-stance, toe-off) through rolling and pivoting motions. Testing with seven subjects demonstrated that the manual lever-operated system requires maximum torques of 10 N-m, well within human capability (49-74 N-m available). Vibration analysis showed acceptable sway amplitudes, with user surveys indicating no discomfort during operation. A functional prototype wheelchair was fabricated incorporating transformation mechanisms for dual-mode operation, validating the feasibility of affordable manual stair-climbing wheelchairs for the Indian market.