A hybrid wheelchair/bed system for bedridden persons is developed and tested. A powered wheelchair can be docked to a bed portion and reconfigured to a flat stationary bed so that the bedridden person does not have to change seating when transferring between the chair and bed. Moreover the wheelchair can also be docked to a toilet directly and automatically. A holonomic omnidirectional vehicle with a ball wheel mechanism is used for the wheelchair. The high maneuverability and holonomic nature of the vehicle allow the chair to be docked easily and precisely against a fixture. The wheelchair is equipped with teleconferencing facility so that the bedridden patient may communicate face-to-face with a distal caregiver, friends and relatives. This paper describes the basic concept of the reconfigurable holonomic omnidirectional mobile bed with unified seating (RHOMBUS). Issues on the mechanical design of the vehicle, chair, and bed are addressed, followed by control issues. A force-guided docking control method using force sensors embedded in the bumper of the vehicle is developed. A prototype system is designed and tested.
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