Among self-toning eontrollcrs, the explicit typt is the most commonly osed in industrial applications due to its simple strnctore; on the other hand the implicit shllctores are less attractive because of their largest shpchlr~l complexity. This paper presents a modification to the generalized minimum variance with pole assignment controller. The modiPr*tion pretends to simplify the origi0.1 algorithm and to make easier its implementation io practical projects, conserving most o f the original attributes. PRINCIPAL SYMBOLS A . MPolynomials of order n,, mb and n, corresponding to, respectively, system output, control input, and disturbance input; e+=co=l.

This study presents the comparison of the theoretical and experimental results of the performance of an adjustable stiffness mechanism. In particular, the use of redundant actuation is emphasized in the design of a one degree-of-freedom Watt II mechanism capable of independently controlling the effective stiffness without a change in equilibrium position. This approach is in contrast to spring mechanism designs unable to actively control the spring rate independent of deflection, and with potential applications in various types of suspension and assembly systems. Results indicate that two direct drive brush-type direct current motors are required to drive the redundantly actuated mechanism and create a system that behaves as an adjustable stiffness spring.