Abstract

We have previously considered a class of passive devices for helping individuals transition from sit to stand and walk. These design have been inspired by a commercially available device called UP’N FREE®1. The objective of the apparatus is to lift the user from seating to a standing position employing of a four bar mechanism which can be actuated in different fashions. A partial compensation for the gravity load can be provided while standing without taxing the arms and shoulders with the use of crouches. The user of this class of devices can transition from sit to stand without the help of a care giver and receive a gravity compensation effect during walking. This paper illustrates a new actuation system to implement the dynamic lifting support where the force profile is modulated using a cam and acting on an elastic band. We were able to obtain a linear profile of the force avoiding sudden increase in force that are typical of previous actuation solutions encompassing gas pistons acting on a variable moment arm.

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