Plamen Petrov

Modeling and Nonlinear Adaptive Control for Autonomous Vehicle Overtaking

In this paper, we present a mathematical model and adaptive controller for an autonomous vehicle overtaking maneuver. We consider the problem of an autonomous three-phase overtaking without the use of any roadway marking scheme or intervehicle communication. The developed feedback controller requires information for the current relative intervehicle position and orientation, which are assumed to be available from onboard sensors. We apply standard robotic nomenclature for translational and rotational displacements and velocities and propose a general kinematic model of the vehicles and the relative intervehicle kinematics during the overtaking maneuver. The overtaking maneuver is investigated as a tracking problem with respect to desired polynomial virtual trajectories for every phase, which are generated in real time. An update control law for the automated overtaking vehicle is designed that allows tracking the desired trajectories in the presence of unknown velocity of the overtaken vehicle. Simulation results illustrate the performance of the proposed controller.

Face detection and tracking with an active camera

This paper consider the problem of face detection and tracking with an active camera. An algorithm using the mean-shift method for face detection has been presented. We propose an algorithm that provides automated control of a pan-tilt camera (PTC) to follow a personpsilas face and keep his image centered in the camera view. An error vector defined in the image plane and representing the face offset with respect to the center of the image is used for camera control. Adaptive feedback control design and stability analysis are performed via Lyapunov techniques. Simulation results are presented to illustrate the effectiveness of the proposed algorithms.

Adaptive steering control for autonomous lane change maneuver

In this paper, we present a two-layer nonlinear adaptive steering controller for autonomous lane change maneuver with respect to a stopped vehicle. First, we derive a dynamic model of the vehicle using the Boltzmann-Hamel method in quasi-coordinates for nonholonomic systems. The lane change maneuver is investigated as a tracking problem with respect to desired cycloidal trajectory, which is generated in real time. An adaptive update control law is designed that allows tracking the desired trajectories in the presence of unknown inertial parameters of the vehicle. Simulation results illustrate the performance of the proposed controller.

Homography-based face orientation determination from a fixed monocular camera

This paper presents a framework for determining the orientation of human faces with a fixed monocular camera which can be used for the purposes of the gaze tracking afterwards. We use homography relation between two views/frames to handle with the lack of depth information. In order to compensate for the lack of depth information in the relationships between the 2D images in the image plane and the 3D Euclidean space, we present a complete vision-based approach to pose estimation. The homography relates corresponding points captured at two different locations of the face and determines the relationships between the two locations using pixel information and intrinsic parameters of the camera. In order to determine the mapping between the two images, it is assumed that in each frame in the video sequence, we are able to locate, extract and labeled four feature points of the face located at virtual plane attached to the face. Face detection and facial feature extraction are executed with Viola-Jones method. The verification stage for face detection use combined cascade of neural network classifiers uses the convolutional neural network.

Modes of unstable resonators with a saturable gain guide

We investigate theoretically gain-guided modes in unstable resonators with a uniformly reflective mirror in the area of highly efficient steady-state lasers, where the gain saturation is the main efficiency factorly. We achieved self-consistent Hermite-Gaussian modes at significant gain saturation as well as the connection of the modes scaling factor and mode amplitude coefficients with the system parameters by using complex paraxial wave optics. A new stabilization mechanism, saturation guiding, works together with gain guiding in unstable resonators. We obtained more actual results for mode generation and selection by integrating the laser rate equation.

Experimental investigation of saturable gain-guided modes

Hermite-Gaussian modes in geometrically unconfined resonators with a four-level system saturable gain guide inside are experimentally observed and proved. The gain guide was formed with a polished cylindrical surface low-concentration Nd:YAG rod exposed to isotropic pump radiation. The connection of the mode scaling factor with the system parameters is compared with the theory. The abilities of the recently established gain-saturation guiding mechanism to support the generation of beams with wide tops and rapidly decreasing intensity in the wings are also experimentally proved. Application areas for saturable gain guiding are briefly discussed.

Development and experimentation of an autonomous vehicle platoon for urban environments

This paper describes a control system for vehicle platoon which permits the ego vehicle to track the trajectory of the vehicle ahead with prescribed inter-vehicle distance. We consider autonomous vehicle following without any information obtained from road infrastructure or communication from the lead vehicle. The relative inter-vehicle position and orientation used for feedback control is obtained with the help of linear camera installed on the following vehicle and three infra-red emitters mounted on the leading vehicle. An adaptive controller for the following vehicle is proposed which deals with unknown leader linear and angular velocities, as well the curvature radius of the path travelled by the lead vehicle. For constant velocity maneuvres of the leader, at steady state, the two-vehicle convoy will travel concentric arcs of same radii with prescribed inter-vehicle spacing. Various simulation and experimental results demonstrating the performance of the controller are presented.

Human gaze tracking in 3D space with an active multi-camera system

This paper presents a framework for determining the direction of human gaze with an active multi-camera system. A fixed 3D depth sensor is employed in order to determine the position of the human face in 3D space and its features, like the eyes. Then an active pan-tilt camera is oriented to one of the users eyes and this way a high precision gaze direction determination is accomplished.

Flattened Gaussian beam generation by using saturable absorbers in conventional mirror unstable Q-switched resonators

It is theoretically shown that using saturable absorbers in unstable resonators can lead to large-volume super-Gaussian beams generation under certain conditions. Practical aspects for Q-switched super-Gaussian beam generation are discussed. The method is experimentally improved.