An extender is defined to be an active manipulator worn by a human to increase his strength [6] . The human, in physical contact with the extender, exchanges power and information signals with the extender. The human arm, the extender, and the environment comprise the dynamic model of the extender system. In this paper, an expression for system performance is derived to determine the force augmentation of the extender. The stability and the performance of the extender are proven via simulation

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... nd via experiments with a single-degree-of-freedom hydraulic extender. The trade-off between performance and stability is discussed: the better the required performance (larger force amplification in this experiment), the narrower the stability range is.