Robot Control Without Velocity Measurements: New Theory and Experimental Results

Modeling and observer-based augmented adaptive control of flexible-joint free-floating space manipulators

“…The robot model (17) has the following structural properties [33][34][35][36] Property 1: M x 1 ð Þ is symmetric and positive definite, and both M x 1 ð Þ and M À 1 x 1 ð Þ are uniformly bounded as function of x 1 .…”

Output-feedback control of nonlinear bilateral teleoperators

“…For further details the interested reader should consult [6], [8]. For system (5), consider the manifold M = {(y, x, ξ,x,ŷ : ξ − x + β(y,ŷ, x) = 0}, where ξ ∈ R 2n ,ŷ ∈ R 2n andx ∈ R 2n are (part of) the observer state, whose dynamics, as well as the mapping β ∈ R 2n × R 2n × R 2n → R 2n , are defined below. To prove that the manifold M is attractive and invariant, it is shown that the off-the-manifold coordinate z = ξ + β(y,ŷ,x) − x, whose norm determines the distance of the state from the manifold M, is such that: C1 (Invariance) z(0) = 0 ⇒ z(t) = 0, for all t ≥ 0 C2 (Attractivity) z(t) asymptotically (exponentially) converges to zero.…”

“…Other practical reasons for incorporating an observer in the closed-loop are that it reduces the complexity of the setup, reduces costs due to the smaller number of sensors and can be considered as an alternative way of reconstructing velocities in case of sensor fault. In the case of simple mechanical systems, the output-feedback problem has been well explored, see [3], [4], [5], [6], [7], [8], [9] and references therein for an exhaustive list of related works. To the best of our knowledge, the literature on the output-feedback control for teleoperators, with unmeasurable velocities, is scarce with only exceptions the recent works [10], [11], [12].…”

Velocity Observer for Mechanical Systems

“…Velocity observer design is a very important topic that continues to be studied, as in (Arteaga and Kelly, 2004;Berghuis and Nijmeijer, 1993;Canudas de Wit and Fixot, 1992). Discontinuous state observers for inexact nonlinear plants have been designed in (Choi et al, 1999;Xiong and Saif, 2001;Xian et al, 2004).…”