Joaquin Collado

Model reference robust adaptive control without a priori knowledge of the high frequency gain

A novel model-reference robust adaptive controller that does not require a priori knowledge of the high-frequency-gain sign is proposed. The scheme is applicable to minimum-phase plants of arbitrary relative degree and ensures that in the absence of unmodeled dynamics the tracking error converges to zero and all the signals remain bounded. The control law uses a particular projected parameter vector instead of the current estimates to avoid division by zero. >

Exponential estimates for neutral time delay systems: an LMI approach

Exponential estimates and sufficient conditions for the exponential stability of linear neutral time delay systems are given. The estimates are obtained for the case of known parameters as well as the uncertain case, including uncertainties in the difference term. The proof is based on Lyapunov-Krasovskii functionals, and the conditions are expressed in terms of linear matrix inequalities (LMIs).

Resetting process-model control for unstable systems with delay

A modification of process-model control schemes is introduced. This modification consists in a periodic resetting of the initial condition of the predictor. It allows us to extend the use of these control laws to unstable linear systems with delay. The robustness of the scheme with respect to parameter uncertainty, delay uncertainty and external disturbances is shown. An illustrative example is presented.

Control of a Parametrically Excited Crane: A Vector Lyapunov Approach

In this brief, a controller is proposed in order to avoid the parametric resonance effect and to attenuate the load oscillations in a parametrically excited crane, ensuring precise load transfer during the load movement despite model uncertainties and un-modeled dynamic actuators. The nonlinear controller proposed in this brief is motivated by the Twisting algorithm and the design uses the vector Lyapunov function approach ensuring the ultimate bounded stability of the overall closed-loop system. The experiments conducted over a laboratory platform resemble quite well the simulations, confirming the obtained results.

Super twisting control of a parametrically excited overhead crane

The principal contribution of this note is to avoid the parametric resonance effect and attenuate the payload oscillations in an overhead-crane system subject to periodic variations in the base support. Considering an appropriate sliding output with relative degree one, we present the sliding mode control design based on the Super-Twisting Algorithm (STA), ensuring finite time convergence to the desired sliding surface for the linear periodic system with Lipschitz continuous matched and unmatched uncertainties bounded together by their gradients by known functions. The suggested approach also provide chattering phenomenon attenuation. Obtained results are verified experimentally.

Using an Observer to Transform Linear Systems Into Strictly Positive Real Systems

In this note, we study the extension of the class of linear time invariant plants that may be transformed into SPR systems introducing an observer. It is shown that for open loop stable systems a cascaded observer achieves the result. For open loop unstable systems an observer-based feedback is required to succeed. In general any stabilizable and observable system may be transformed into an SPR system defining a new output based on the observer state. This overcomes the old conditions of minimum phase and relative degree one for the case of keeping the original output. The result is illustrated with some examples.

Second-Order Sliding Mode Control of a Perturbed-Crane

A fiv degrees-of-freedom overhead crane system affected by external erturbaions is the topic f study. Existing method justhandle the nperturbed case or, in addition, the analysis is limited to thre ...

Model Reference Robust Adaptive Control without a Prior Knowledge of the High Frequency Gain

This paper proposes a new model reference robust adaptive controller that does not require a priori knowledge of the high frequency gain sign. The scheme is applicable to minimum phase plants of arbitrary relative degree and ensures that, in the absence of unmodelled dynamics, the tracking error converges to zero and all the signals remain bounded. The control law uses a particular projected parameter vector instead of the current estimates to avoid division by zero.

Parametric Resonance Cancellation Via Reshaping Stability Regions: Numerical and Experimental Results

In this brief, a vibrational control law is designed and applied to an unstable and parametrically excited mechanical system, namely, a gantry crane. The control law cancels the parametric resonance by reshaping the stable regions. The parameters of the control law are tuned by using a graphic scheme based on the symbolic computation of the monodromy matrix. The control law is implemented experimentally in the laboratory model of a gantry crane, confirming the theoretical results.

Second order sliding mode control of a 3-Dimensional Overhead-Crane

In this paper the 3-Dimensional Overhead Crane is the subject of study. The note includes the Euler-Lagrange equations of a 5 degrees of freedom, 5DOF, Overhead Crane and the design of a Second Order Sliding Mode Controller in order to ensure the precise load transfer during the load movement despite of model uncertainties and un-modeled dynamics. Moreover, the system is under-actuated and 5DOF should be controlled with 3 control actions. The stability analysis is developed based on Lyapunov second method ensuring the finite time convergence to the desired sliding output. Simulations and Experimental results are presented.