A cheap output feedback tracking controller with robustness: the RLFJ problem

IEEE Trans. Automat. Contr.

Panteley

2017

We study under-actuated Lagrangian systems without dissipative forces, augmented by a chain of integrators. For such systems, we solve the open problem of global tracking control via position measurements only; strictly speaking, we establish uniform global asymptotic stability for the closed loop system. As a corollary, we obtain an original statement for flexible-joint robots, which closes a long-standing open problem of output feedback nonlinear control.

Section: Introductionmentioning

confidence: 99%

A Separation Principle for Underactuated Lossless Lagrangian Systems

Avila-Becerril

IEEE Trans. Automat. Contr.

Panteley

2017

“…In [11] the authors presented a result based on a semi-global nonlinear observer for the unmeasured variables, which needs only the link positions. In [19] the authors propose a robust output-feedback link position tracking control ensuring semi-global uniformly ultimately bounded link position tracking; and in the same spirit, in [3] based on a set of filters, removes the need of measuring link and actuator velocities, however the result relies on the restrictive assumption that the system is internally damped by viscous friction. In [17] a nonlinear observer-based certaintyequivalence tracking controller for Euler Lagrange systems is presented; global conditions are obtained under the assumption that one disposes of a controller that can be bounded by an affine function in the position times a polynomial of the velocities.…”

Section: Introductionmentioning

confidence: 99%

Global position-feedback tracking control of flexible-joint robots

Avila-Becerril¹,

2016 American Control Conference (ACC)

Panteley

2016

International audienceWe solve the open problem of global tracking control of 2nd-degree under-actuated lossless (without friction) Lagrangian systems via position measurements only. For flexible-joint robots, we design a dynamic controller which is based on measurements of link and joint positions only. Then, approximate differentiation is used for link velocities and a simple Luenberger observer for rotor velocities. The main results constitute a significant extension of recent work on observerless output-feedback control of Lagrangian systems. Strictly speaking, we establish uniform global asymptotic stability for the closed loop system

Output-feedback global tracking control of robot manipulators with flexible joints

2014 American Control Conference

Avila-Becerril²

2014

International audienceWe present a controller for flexible-joint robots without link velocity measurement. Our main result consists in a simple controller of the type proportional-derivative plus feedforward and a series of cascaded filters; the control design is reminiscent of classical backstepping control. To avoid the assumption that link velocities, accelerations and jerks are measured, we use approximate differentiation. The originality of our work lays in establishing uniform global asymptotic stability for the closed-loop system