A novel step climbing strategy for a wheelchair with active-caster add-on mechanism

We have previously developed a five-wheeled wheelchair with an active-caster drive system. To improve motion performance of the wheelchair, we have proposed the function which two types of motions, such as rear-like drive and front-like drive mode, can be selected by using the linear actuator. In this paper, we propose a step climbing strategy and develop a mechanism. The proposed five-wheeled wheelchair has five points of contact to the ground in the stand condition. To make the front casters of the wheelchair to be hovered from the ground, a “static wheelie” configuration in which large wheels and a drive wheel touch to the ground is taken by maintaining the static stability of a wheelchair. We propose a novel and unique strategy by utilizing the statically stable wheelie configuration. Additionally, the drive wheel is lifted onto the step by cooperative control between the linear actuator and the drive wheel. We confirm that the proposed method is applicable by comparing it with a step climbing method that uses only the traction force of the drive wheel. To achieve the proposed step climbing method, we develop a novel link mechanism that can perform not only the step climbing method but also the functions mentioned above and confirm the design conditions. After the prototype is built, we confirm that a user can climb over a step by the proposed method and mechanism.