Kinematic analysis and design of surface wave distributed actuators with application to a powered bed for bedridden patients

Natural surface waves, created by periodic circular motion of material part icles, can transfer a long object placed upon the crests of the waves in an arbitrary direction within the horizontal plane. Inspired by this natural behavior, a surface wave distributed actuation method and its potential for transporting bedridden patients is explored in this paper. First, the basi c principle of surface wave distributed actuation is presented, followed by kinematic modeling and analysis. Based on the analysis, modifications to n atural wave transport are made to enhance transport efficiency and human co mfort. Further kinematic analysis reveals that an object can be transferred by a simplified actuator architecture that makes the concept amenable to h ardware realization. Two proof-of-concept prototypes are designed, built, a nd tested, The first is a powered water bed consisting of a water vat, a fl exible mat placed on the water surface, and an exciter creating surface wav es at resonant frequencies. The other is a powered mechanical bed having an array of coordinated active nodes that generate psuedocontinuum surface wa ves. Experiments demonstrate the surface wave actuation concept and verify the analytical results, Finally, design tradeoffs and guidelines for develo ping a feasible and practical surface wave bed are discussed based on the p rototyping and experiments.