No abstract

Recently, an adaptive control approach has been proposed. This approach, named L 1 adaptive control, involves the insertion of a low-pass filter at the input of the Model Reference Adaptive Control (MRAC). This controller has been designed to overcome several limitations of classical adaptive controllers such as (i) the initialization of estimated parameters, (ii) the stability problems with high adaptation gains, and (iii) the appropriate parameter excitation. In this paper, a new design of the filter is presented, used for L 1 adaptive control, for which the desired performances are guaranteed (appropriate values of the control during start-up, a high filtering of noises, a reduced time lag, and a reduced energy consumption). Parameters of the new proposed filter have been optimised by genetic algorithms. The proposed L 1 adaptive fractional control is applied to a polyarticulated robotic system. Simulation results show the efficiency of the proposed control approach with respect to the classical L 1 adaptive control in the nominal case and in the presence of a multiplicative noise.

This study proposes an approach to synthesize a three-impulse sequence input shaper with a negative impulse, known as Unity Magnitude (UM) shaper. The corresponding analytic model has been already achieved for undamped and low-damped systems. In this paper, the analytic design of UM shaper is demonstrated for the generalized case of damped systems for both types: integer and fractional orders. Hence, the UM shaper model has been designed for second-order systems with damped dynamics, associating a graphical fitting and an analytical procedure; then, it has been extended to explicit fractional derivative systems. Moreover, the feasibility and the effectiveness of the proposed on-off profile prefilter applied on a second-generation controller have been substantiated by experimental results on an instrumented DC motor bench.

An approach to path tracking design based on fractional differentiation has been proposed with its application on a multivaribale systems. In previous works, a first approach using Davidson-Cole prefilter has been developed and applied to MIMO (Multi Inputs Multi Outputs) systems. The goal of this paper is the extension of this work using a Frequency Band Limited Fractional Differentiator (FBLFD) prefilter. The global transfer function is assimilated to a FBLFD prefilter, whose main properties are to have no overshoot on the plant and to have maximum control value for starting time. The MIMO-QFT (Multi Input Multi output-Quantitative Feedback Theory) robust synthesis design combined with CRONE control procedure and taking into account plant uncertainties is used in this paper to extract the CRONE controller expression. After that, the prefilter parameters are optimized taking into account tracking performance specifications and actuators physical constraints. The proposed design is applied to an example taken from the literature.