Showing papers by "Rogelio Lozano published in 1992"
TL;DR: In this paper, an adaptive control scheme for flexible joint robot manipulators is presented, and joint position and velocity tracking errors are shown to converge to zero with all the signals in the system remaining bounded.
Abstract: Presents an adaptive control scheme for flexible joint robot manipulators. Asymptotic stability is insured regardless of the joint flexibility value, i.e., the results are not restricted to weak joint elasticity. Moreover, the joint flexibility is not assumed to be known. Joint position and velocity tracking errors are shown to converge to zero with all the signals in the system remaining bounded. >
258 citations
TL;DR: In this paper, an adaptive control scheme for nonlinear systems of the form x=c*/sup T/f(x)+b*u, where f(x) is Lipschitz, c* is a constant vector, and b* is constant scalar, is presented.
Abstract: The authors present an adaptive control scheme for nonlinear systems of the form x=c*/sup T/f(x)+b*u, where f(x) is Lipschitz, c* is a constant vector, and b* is a constant scalar. The control scheme achieves asymptotical model matching without a priori knowledge of the sign of the b* gain. The adaptive scheme is free from singularities in the sense that the estimate of b*, entering in the denominator of the control law, is bounded away from zero. The singularity has been overcome through a suitable modification of the parameter estimates which is based on standard least squares covariance matrix properties. >
87 citations
TL;DR: In this article, an alternative stability analysis is presented for recent results on global stabilization of a nonlinear system in cascade with a linear system. The analysis is carried out using passivity arguments and the relationship between passivity and an important class of Lyapunov function is also presented.
Abstract: An alternative stability analysis is presented for recent results on global stabilization of a nonlinear system in cascade with a linear system. The analysis is carried out using passivity arguments. The relationship between passivity and an important class of Lyapunov function is also presented. >
73 citations
TL;DR: In this article, an adaptive control scheme for manipulators with redundant degrees of freedom is presented, where the control purpose is to achieve a desired interaction force between the end-effector and the environment as well as to regulate the robot tip position in the Cartesian space.
Abstract: An adaptive control scheme for manipulators with redundant degrees of freedom is presented. The control purpose is to achieve a desired interaction force between the end-effector and the environment as well as to regulate the robot tip position in the Cartesian space. This control approach does not require measurement of the joint acceleration or the force derivative. >
72 citations
TL;DR: In this article, an approach to avoid singularities in adaptive pole-placement control algorithms is presented, which is applicable to either minimum or non-minimum phase plants and the closed-loop stability is guaranteed in spite of bounded disturbances.
37 citations
24 Jun 1992
TL;DR: In this paper, an adaptive control scheme for first order systems of the form y + a*y = b* 0 u + b* 1 u which may possibly be nonminimum phase is presented.
Abstract: This paper presents an adaptive control scheme for first order systems of the form y + a*y = b* 0 u + b* 1 u which may possibly be nonminimum phase. The control scheme achieves asymptotical stabilization without any apriori knowledge on the plant parameters. The adaptive scheme is free from singularities in the sense that the plant estimated model is always controllable. The singularity has been overcome through a suitable modification of the parameters estimates which is based on standard least squares covariance matrix properties.
6 citations
TL;DR: In this article, a pole placement control scheme for indirect adaptive control is proposed, which is applicable to either minimum or non-minimum phase systems, and requires only a priori knowledge of the system order and an upper bound of the disturbance.
6 citations
16 Dec 1992
TL;DR: In this article, an indirect model reference adaptive control for minimum-phase linear systems of arbitrary order with unknown high-frequency gain is presented, and it is proved that the (modified) estimate of the highfrequency gain has a uniform positive lower bound.
Abstract: An indirect model reference adaptive control for minimum-phase linear systems of arbitrary order with unknown high-frequency gain is presented. It is proved that the (modified) estimate of the high-frequency gain has a uniform positive lower bound. The problem has been solved by using the least squares covariance matrix properties to define an appropriate modification of the parameter estimates. The proposed algorithm requires neither signal normalization nor the definition of an augmented error. >
5 citations
TL;DR: In this article, the standard least squares (LS) estimation algorithm is modified in such a way that it becomes passive, and the scope of application of the LS algorithm is extended to those adaptive schemes whose convergence proof is based on passivity.
Abstract: The standard least squares (LS) estimation algorithm is modified in such a way that it becomes passive. Therefore the scope of application of the LS algorithm is extended to those adaptive schemes whose convergence proof is based on passivity. The passive version of LS is presented in both continuous and discrete time.
4 citations
TL;DR: An adaptive controller for a class of first order nonlinear systems: x = − θ∗Tf(x) − b∗u, subject to bounded input and output disturbances, with unmodelled dynamics considered.
4 citations
01 Jan 1992
TL;DR: In this paper, an adaptive control scheme for a standard least squares covarianc matrix is presented, which achieves asymptotic stabilization without anya priori knowledge on the plant parameters.
Abstract: This paperpresents anadaptive control scheme forfrstordersystemsoftheform= boi+b;u whichmaypossibly benonminimum phase. Thecontrol scheme achieves asymptotical stabilization without anya- priori knowledge ontheplant parameters. Iheadaptive scheme isfree fromsingularities inthesense that theplant estimated model isalways controllable. Thesingularity has beenovercome through a suitable modification ofthe parameters estmates which isbased onstandard least squares covarianc matrix ppertes.
TL;DR: In this article, an adaptive control scheme was proposed to stabilize second order systems of the form y + a 1 * y ˙ + a 2 * y = b 0 * u ǫ + b 1 * u which may possibly be non-minimum phase.
TL;DR: In this article, an adaptive control scheme for nonlinear systems of the form x ˙ = c * T f (x ) + b * u where c* is a constant vector and b* a constant scalar is presented.