Gustavo Osorio

Corner-Impact Bifurcations: A Novel Class of Discontinuity-Induced Bifurcations in Cam-Follower Systems

This paper is concerned with the analysis of a class of impacting systems of relevance in applications: cam-follower systems. We show that these systems, which can be modeled as discontinuously forced impact oscillators, can exhibit complex behavior due to the detachment at high rotational speeds between the follower and the cam. We propose that the observed phenomena can be explained in terms of a novel type of discontinuity-induced bifurcation, termed as corner-impact. We present a complete analysis of this bifurcation in the case of a nonautonomous impact oscillator and explain the transition to chaos observed in a representative cam-follower example. The theoretical findings are validated numerically.

Existence, stability and robustness analysis of limit cycles in hybrid anti-lock braking systems

We investigate the stability and robustness properties of anti-lock braking systems (ABS) based on actuators with on/off dynamics. Namely, we propose a hybrid ABS controller which gives rise to an asymptotically stable limit cycle on the wheel slip. The proposed approach allows to derive exact information on the maximum allowable uncertainty in the measured variables which guarantee the cycle stability. Moreover, a structural stability analysis is performed with respect to different road conditions and to the actuator rate limit.

Limit cycles analysis in hybrid anti-lock braking systems

We investigate the stability and robustness properties of anti-lock braking systems based on hydraulic actuators with on/off dynamics. Namely, we propose a hybrid ABS controller which gives rise to an asymptotically stable limit cycle on the wheel slip. The proposed approach allows to perform a structural stability analysis with respect to different road conditions and to the actuator rate limit.

Design of a FPGA based position PI servo controller for a DC motor with dry friction

In this paper we present the design, implementation and experimental validation of a FPGA based position servo controller for a DC motor with dry friction. VHDL and block diagram modules for trajectory generation, encoder signal decoding, PI controller and PWM control signal generation are described. The control system is implemented in the DE3 board of Terasic Technologies Inc using Quartus II environment of Altera Corporation. Servo system simulation was made using Simulink. The analytical non linear model for the anti-windup saturation on the integral control action, saturation on the actuator and dry friction is validated through experiments and simulations.

An experimental comparison of a hierarchical range image segmentation algorithm

This paper describe a new algorithm to segment range images into continuous regions represented by Bezier polynomials. The main problem in many segmentation algorithms is that it is hard to accurately detect at the same time large continuous regions and their boundary location. In this paper, a Bayesian framework is used to determine through a region growing process large continuous regions. Following this process, an exact description of the boundary of each region is computed from the mutual intersection of the extracted parametric polynomials followed by a closure and approximation of this new boundary using a gradient vector flow algorithm. This algorithm is capable of segmenting not only polyhedral objects but also sculptured surfaces by creating a network of closed trimmed Bezier surfaces that are compatible with most CAD systems. Experimental results show that significant improvement of region boundary localization and closure can be achieved. In this paper, a systematic comparison of our algorithm to the most well known algorithms in the literature is presented to highlight its performance.

Hierarchical segmentation of range images with contour constraints

This paper describes a new algorithm to segment in continuous parametric regions range images. The algorithm starts with an initial partition of small first order regions using a robust fitting algorithm constrained by the detection of depth and orientation discontinuities. The algorithm then optimally group these regions into larger and larger regions using parametric functions until an approximation limit is reached. The algorithm uses Bayesian decision theory to determine the local optimal grouping and the complexity of the parametric model used to represent the range signal. After the segmentation process an exact description of the boundary of each region is computed from the mutual intersections of the extracted surfaces. Experimental results show significant improvement of region boundary localization. A systematic comparison of our algorithm to the most well known algorithm in the literature is presented to highlight the contributions of this paper.

Performance Analysis of a Peak-Current Mode Control with Compensation Ramp for a Boost-Flyback Power Converter

High voltage gain power converters are very important in photovoltaic applications mainly due to the low output voltage of photovoltaic arrays. This kind of power converters includes three or more semiconductor devices and four or more energy storage elements, making the dynamical analysis of the controlled system more difficult. In this paper, the boost-flyback power converter is controlled by peak-current mode with compensation ramp. The closed-loop analysis is performed to guarantee operation conditions such that a period-1 orbit is attained. The converter is considered as a piecewise linear system, and the closed-loop stability is determined by using the monodromy matrix, obtained by the composition of the saltation matrixes with the solutions of the dynamical equations in the linear intervals. The largest eigenvalue of the monodromy matrix gives the stability of the period-1 orbit, and a deep analysis using bifurcation diagrams let us reach a conclusion about the loss of the stability, which is experimentally verified. To avoid overcompensation effects, the minimum value required by the compensation ramp is obtained, and the minimum and maximum values of the load resistance are found too. The system has a good transient response under disturbances in the load and in the input voltage.

Event-driven simulation of Filippov systems: The case of a nonlinear Wien bridge oscillator

Here, we will show how to simulate systems with sliding dynamics, also known as Filippov systems. The current simulation techniques have blocks, wrong solutions, and very long times when dealing with Filippov systems. We will study the case of a Wien bridge oscillator with a diode. The piecewise smooth model of the diode generates a sliding dynamics.

Nonlinear numerical analysis of a cam-follower impacting system

In this paper we present the piecewise smooth model, simulation and numerical nonlinear analysis of a camfollower impacting system, characterized by a cam with non-smooth profile - a discontinuous second derivate - and a follower modeled as a rod pendulum. The model include three main dynamical modes, free body mode, sliding mode and impacting mode. We will show the description of the algorithm to simulate cam-follower impacting systems. The algorithm was developed under an event driven strategy and implemented in Matlab.

Coexistence of solutions in a boost-flyback converter with current mode control

In many practical applications power Converters are designed to work in a desired operation point depending on the needs of the appliance. The ability of the system to work in that point is related to a correct dynamic analysis that eventually leads to de design of a proper control strategy. Linear model approximations are an option to design control loops, but using this kind of models the nonlinear dynamics are neglected. In this paper we propose to study a boost-flyback converter by means of the numerical analysis of the converter hybrid model. The bifurcations diagrams show that the converter exhibits coexistence of solutions when varying the coupling coefficient of the inductors. Four different coexistence scenarios are reported, including period-1, period-2 and chaotic solutions. Results for two cases of study are experimentally validated.