Showing papers by "Gonzalo López-Nicolás published in 2010"

Homography-Based Control Scheme for Mobile Robots With Nonholonomic and Field-of-View Constraints

Abstract: In this paper, we present a visual servo controller that effects optimal paths for a nonholonomic differential drive robot with field-of-view constraints imposed by the vision system. The control scheme relies on the computation of homographies between current and goal images, but unlike previous homography-based methods, it does not use the homography to compute estimates of pose parameters. Instead, the control laws are directly expressed in terms of individual entries in the homography matrix. In particular, we develop individual control laws for the three path classes that define the language of optimal paths: rotations, straight-line segments, and logarithmic spirals. These control laws, as well as the switching conditions that define how to sequence path segments, are defined in terms of the entries of homography matrices. The selection of the corresponding control law requires the homography decomposition before starting the navigation. We provide a controllability and stability analysis for our system and give experimental results.

Reset adaptive observers and stability properties

Abstract: This paper proposes a novel kind of adaptive observer called reset adaptive observer (ReO). A ReO is an adaptive observer consisting of an integrator and a reset law that resets the output of the integrator depending on a predefined condition. The main contribution of this paper is the application of the reset element theory to the adaptive observer LTI framework. The introduction of the reset element in the adaptive laws can decrease the overshooting and settling time of the estimation process without sacrificing the rising time. The stability and convergence LMI-based analysis of the proposed ReO is also addressed. Additionally, an easily computable method to determine the ℒ 2 gain of the ReO dealing with noise-corrupted systems is presented. A simulation example shows the potential benefit of the proposed reset adaptive observer.

Omnidirectional visual homing using the 1D trifocal tensor

Abstract: This paper presents a new method for visual homing to be used on a robot moving on the ground plane. A relevant issue in vision-based navigation is the field-of-view constraints of conventional cameras. We overcome this problem by means of omnidirectional vision and we propose a vision-based homing control scheme that relies on the 1D trifocal tensor. The technique employs a reference set of images of the environment previously acquired at different locations and the images taken by the robot during its motion. In order to take advantage of the qualities of omnidirectional vision, we define a purely angle-based approach, without requiring any distance information. This approach, taking the planar motion constraint into account, motivates the use of the 1D trifocal tensor. In particular, the additional geometric constraints enforced by the tensor improve the robustness of the method in the presence of mismatches. The interest of our proposal is that the designed control scheme computes the robot velocities only from angular information, being this very precise information; in addition, we present a procedure that computes the angular relations between all the views even if they are not directly related by feature matches. The feasibility of the proposed approach is supported by the stability analysis and the results from simulations and experiments with real images.

QFT-Based Robust Simmering Control for Domestic Induction Cookers Using an Infrared Sensor

Abstract: This paper presents a robust simmering control for induction hobs. This kind of process is almost impossible to carry out in a domestic cooker where the pot temperature is unknown. We exploit an analytical model of the cooking process to design a QFT-based controller. The resultant controller satisfies all user requirements such as a quick heating up, an accurate temperature control and a fast disturbance rejection. Additionally, the proposed temperature control can also minimize the energy consumption and, as a consequence, it can increase the efficiency of the cooking process. Finally, the effectiveness of our proposal has been verified by means of verification test in real induction hobs.

On robust pi adaptive observers for nonlinear uncertain systems with bounded disturbances

Abstract: Robust adaptive observers for uncertain systems corrupted by bounded disturbances have to overcome two main problems. They have to guarantee a bounded parameter estimation, because it is well known that an arbitrarily small disturbance might drift to infinity the parameter estimation error even if the state estimate error remains bounded, and they have to ensure a robust state and parameter estimation independently of the uncertainty of the system. The contribution of this paper is a solution of both issues. We present a robust adaptive observer based on a normalized dead zone which guarantees a bounded estimate dealing with noise corrupted systems and on an adaptive gain which increases the robustness against uncertain systems. Tuning parameters are computed minimizing the effect of disturbances on the estimation error. The performance and the stability of the proposed adaptive observer is analyzed and demonstrated through simulation examples.

Catadioptric camera model with conic mirror

Abstract: Catadioptric systems consist of the combination of lenses and mirrors. From them, central panoramic systems stand out because they provide a unique effective viewpoint, leading to the well-known unifying theory for central catadioptric systems. This paper considers catadioptric systems consisting of a conic mirror and a projective camera. Although a system with conic mirror does not possess a single projection point, it has some advantages as the cone is a very simple shape to produce, it has higher resolution in the peripheral, and adds less optical distortion to the images. The contributions of this work are the model of this non-central system by means of projective mappings from a torus to a plane, and the definition of the conic fundamental matrix with a role similar to that of perspective cameras. Additionally, a procedure to compute the relative motion between two views from the conic fundamental matrix is presented.