Antonio Osorio

Adaptive stabilization of nonminimum phase first-order continuous-time systems

Presents an adaptive control scheme for first order systems of the form y/spl dot/+a*y=b/sub 0/*u/spl dot/+b/sub 1/*u which may possibly be a nonminimum phase. The control scheme achieves asymptotical stabilization without any a priori 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 parameter estimates, which is based on standard least squares covariance matrix properties, and the use of a hysteresis switching function. >

Disturbance rejection for a Quadrotor aircraft through a robust control

This paper addresses the problem of designing and experimentally validating a nonlinear disturbance observer, focus on the attitude regulation control problem of a quad-rotor in presence of external disturbances. The proposed nonlinear observer scheme is based on the angular velocity measurements and the control inputs in order to compensate external disturbances. The stability analysis of the nonlinear observer scheme is proven via the use of Lyapunov theory. Finally, simulation and experimental results in a education platform are presented to show the effectiveness of the proposed nonlinear algorithm in presence of external disturbances.

Altitude control of an Unmanned Aircraft System using a Super-Twisting controller based on High Order Sliding Mode Observer

In this paper, the altitude tracking problem for an Unmanned Aircraft System (UAS) is considered under the assumption that the altitud velocity is unknown. Since in a practical implementation the employed sensors used to measure the altitude (Barometer and GPS) do not provide the altitude velocity. The proposed strategy was designed by using a Super-Twisting controller based on a High Order Sliding Mode Observer. A comprehensive stability analysis based on the Lyapunov Stability Theory guarantees the convergence of the tracking error in finite time. To demonstrate the performance of the proposed solution, a set of simulation results are presented.

Stability analysis and experiments for a force augmenting device

We present preliminary results of a one degree of freedom (DOF) linear moving force augmenting device (FAD) with a force sensor for enhancing the lifting capabilities of a human user. We perform a stability test of the feedback loop formed by the device and a model of the human operator. It is shown that the operator lifts a small fraction of the total weight of the load. The proposed control scheme is illustrated using numerical simulations and an experiment.

Stability Analysis for a Force Augmenting Device Considering Delays in the Human Model

This paper presents a stability analysis of the interaction between a human and a linear moving Force Augmenting Device (FAD). The analysis employs the mathematical models of the human, the FAD and their interaction. As a depart from past works, this article presents a stability analysis considering time-delays in the human model. A key ingredient in the analysis is the use of the Rekasius substitution for replacing the time-delay terms. It is proved that the human machine interaction is stable when the human model has no delays. The analysis provides an upper bound for the time-delays preserving a stable interaction. Numerical simulations allow to assess the human-FAD interaction. An experiment is performed with a laboratory prototype, where a human operator lifts a load. It is observed that the human machine interaction is stable and the human operator is able to move the load to its desired position by experiencing very little effort.

Modeling and analysis of a tricopter/flying-wing convertible UAV with tilt-rotors

The aim of this paper is to provide a mathematical model for a convertible unmanned aerial vehicle that combines the capabilities of a flying wing and tricopter with tilt rotors. This article presents the mathematical model for airplane and tricopter modes as well as the way they are related during the transition phase. Also is presented a control strategy to hover flying. Finally, it is presented simulation results of tricopter mathematical model under controls developed.

Mathematical model and simulation of finger movement with electromyographic signals

A mathematical model that describes the movement of the fingers of the hand is reported in this paper. Electromyographic signals (EMG) are recorded from the forearm and are analyzed to detect which of them are responsible of the movement of each finger. The way the EMG signals are analyzed to determine which of them produce the movement of the fingers is also described. These will be used in an ongoing project that consists of a glove used to enhance the force of the hand of a user.

Hybrid, discrete, non-linear, suboptimal force augmenting exoskeleton for the elbow joint

The design and implementation of a force augmenting exoskeleton for the elbow joint is presented in this paper. The force augmentation comes from electric motors as well as from pneumatic muscles that are the actuators of the device. This is the reason to say that the device is hybrid. Electric motors are more easily and precisely controlled than pneumatic muscles, however the last ones can move heavier weights. The autonomy of a device of this kind is reduced due to the energy expenditure of the two types of actuators employed. For this reason a suboptimal discrete nonlinear control was implemented which improves performance and lengthens considerably the operation time. A dynamical model of the device is also presented and a comparison between a PD+G and a suboptimal control is made. Simulation results are presented.

Robust control with disturbance observer for UAV translational tracking

An integral robust observer with rejection control disturbance is proposed in this paper. The design of the observer is performed employing the canonical obervable model of the original non-linear system, obtained by a change of coordinates. A practical stability is proved using the Lyapunov approach with using a high gain to maintain the solution in a convergence ball. Several simulations cases are carried out to illustrate the performance of the closed-loop system in a disturbance wind prepense. In other cases, noise in the states are added to emulate a real system.

Study of the interaction between a one degree of freedom force augmenting device and a human operator

In this paper a one degree of freedom (DOF) force augmenting device (FAD) is presented. A laboratory set-up has been built and some tests of the interaction between the FAD and a user were performed. The stability of the closed loop system is essential for the performance of the FAD. The FAD by itself is a stable device, but what is important is to assure the stability of the interaction between the FAD and a human being. To deal with this matter, two situations were analyzed. The case of no delays in the model is first considered. This situation might appear unrealistic, for this reason, a second analysis is performed considering a human model with delays. In order to deal with delays a Rekasius substitution is used. To perform the stability analysis, it is sufficient to apply the Routh-Hurtwitz criteria. Attempts with other techniques have given more conservative stability results. The stability has been proven for delays smaller than upper-bounds which have been computed. None of these upper-bounds are reached by any healthy human being. Therefore, we can assure that the whole system is stable for most of the practical situations. This proves the robustness of the closed loop system with respect to delays. In real time experiments, measurement from the sensors are normally noisy. In order to reduce the effect of the noise, a low pass filter was included. The introduction of this filter alters the order of the system, changing the stability conditions of the whole set up. So the stability analysis is performed again with the inclusion of the filter.