Friction compensation for an industrial hydraulic robot

Dept. of Autom. Control, Los Andes Univ., Merida
IEEE control systems (Impact Factor: 2.09). 03/1999; 19(1):25 - 32. DOI: 10.1109/37.745763
Source: IEEE Xplore


A model based friction compensation scheme using a novel dynamical
friction model was implemented on an industrial Schilling Titan II
hydraulic robot. Off-line estimation of parameters was carried out,
using the results of two kinds of experiments. These experiments were
done independently at each joint. A nonlinear PI type controller was
used in the inner torque loop to improve its performance. The complete
control scheme has shown to substantially improve the position precision
in regulation and tracking. Higher precision applications can be
performed by the hydraulic robot with this controller

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Available from: Guillaume Morel, Mar 20, 2015
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    • "Therefore, this model is investigated experimentally (e.g. the observation of discrepancies [17] and modifications for overcoming them [18], [19], [20], [21]), is done mathematically (e.g. the passivity analysis [22]), and is applied to a wide range of systems (e.g. [14], [23], [24], [25]). "
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    ABSTRACT: In this paper, for motion planning and controlling on manipulation system, a novel contact transition model is proposed by employing the LuGre friction model instead of Coulomb friction. The LuGre model is a differential equation with a state variable defined as the microscopic average bristle deflection between bodies and has the capability of more realistic friction properties. The stick-slip transition in the tangential directions at contact points is firstly formulated as a continuous system because the LuGre model is continuous at zero tangential contact velocities. The impact transition is secondly formulated by describing the dynamics of collided bodies during the impact as differential equations with respect to the normal impulse instead of time. Here, the LuGre model is modified to the differential one with respect to the normal impulse, where the state variable can be interpreted as the stored energy of the bristle deflection. Numerical simulations are performed to show the effectiveness of the formulations.
    10th International Workshop on Robot Motion and Control, Poznan, Porland; 07/2015
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    Measurement 06/2015; 69:210-221. DOI:10.1016/j.measurement.2015.02.058 · 1.48 Impact Factor
    • "In some of them, the control goal is defined as the elimination of self-excited stick-slip oscillations [2] [3]. The analysis and elimination of friction-induced stick-slip periodic motion have been extensively treated in the literature from different viewpoints [7] [8] [9] [10] [11] [12] [13] [14]. "
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    ABSTRACT: The slow-motion control of an experimental hydraulically actuated robot with unknown friction forces and stick-slip oscillations is considered. A solution based on a design well-suited for engineering implementation is proposed. This consists of a double integral action controller with adequate stability margins. With such a configuration, harmful jerky motion is eliminated. Limited resolution of the sensors, friction forces and the integral actions of the controller give rise to stick-slip oscillations. The consideration of a switching control based on a linear observer designed for the closed-loop system makes the mechanism be free of these oscillations. Experimental results show the effectivity of the control scheme. The relevance of the solution here proposed is threefold: (a) well-known control engineering techniques are applied, (b) modelling and identification of elaborated friction force models usually required for more sophisticated controllers are not needed for the solution here proposed, and (c) the control system stability margin specifications considered are adequate.
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