Leszek Ambroziak

Vision-based obstacle avoidance for unmanned aerial vehicles

A problem of unmanned aerial vehicles (UAVs) being able to avoid obstacles and collisions by means of processing the images taken by one camera is presented in the paper. The optical flow method based on gradient method of Lukas-Kanade was used to obtain the tested structure in 3D space environment (extraction of images depth). This method allows to generate local information flow patterns from particular neighborhood of surrounding points. Presented algorithm for obstacle location and estimation of its shape was developed and implemented on the workstation with real time uClinux system. Proposed vision-based obstacle avoidance algorithm is demonstrated in simulation and in hardware in the loop flight tests on a fixed-wing UAV.

Formation Flight Control Scheme for Unmanned Aerial Vehicles

Cooperative control of Unmanned Aerial Vehicles is currently being researched for a wide range of applications. Applicability of aerial unmanned systems might be increased by formation flight. In this paper, we present an application of a proportional-integral controller for formation flight of three Unmanned Aerial Vehicles (UAVs). A decentralized cooperative control scheme is used with information flow modeled by a leader-follower structure. Control laws, based on velocity and position errors between the vehicles, are defined and derived for each of the three flying objects in formation. The main goal of this work is a simulation study. Three-dimensional motion of the three-object formation was performed and analyzed using a six-degrees-of-freedom state space quadrotor model. The simulation studies presented allow verifying the adopted control structure. Convergence time is used as an indicator of the control system quality and the formation stability. The presented research and diagram of control algorithms tests were done before experimental tests and field trials of formation flight.

UAV Autonomous Formation Flight Experiment with Virtual Leader Control Structure

The problem of autonomous formation flight control of UAVs (Unmanned Aerial Vehicles) is presented in the paper. A decentralized control method of the autonomous formation flight realization is described. A practical approach to the UAV formation flight control was shown. The applied method bases on the information exchange between flying objects. The shared data concern the position and velocity of the aircraft. Constructed UAV airframe was presented as well as used autopilot, developed formation flight control unit, wireless communication links and used data packet structure. The main aim of this work was the in-flight tests. The test of formation flight with Virtual Leader (VL) was examined. The autopilot reactions to the incoming data packets with desired altitude, airspeed and heading from formation flight controller were checked. During the flights the longitudinal and lateral positions of the UAV, orientation angles (pitch, roll, yaw), angular velocities (pitch rate, roll rate, yaw rate) and many other flight parameters were logged. The research and flight tests checked and verified the developed method of formation flight control.

Real time localization system with Extended Kalman Filter for indoor applications

This paper presents the radio based localization system for indoor applications. For position determination radio COTS transceiver chip was used. Localization accuracy was improved by developing Extended Kalman Filter with modified PV model. Mathematical model of the nonlinear filter was presented and implemented. The described model as well as designed localization system was tested in a realistic environment. Presented results show accuracy of the localization system and enable the assessment possibility of using proposed localization system in further navigational investigations.

A GROUND CONTROL STATION FOR THE UAV FLIGHT SIMULATOR

Abstract In the paper implementation of a ground control station for UAV flight simulator is shown. The ground control station software is in cooperation with flight simulator, displaying various aircraft flight parameters. The software is programmed in C++ language and utilizes the windows forms for implementing graphical content. One of the main aims of the design of the application was to simplify the interface, simultaneously maintaining the functionality and the eligibility. A mission can be planned and monitored using the implemented map control supported by waypoint list.

Computationaly Simple Obstacle Avoidance Control Law for Small Unmanned Aerial Vehicles

Abstract The investigations of the system which allow to avoid obstacles by the unmanned aerial vehicles (UAV) are presented in the paper. The system is designed to enable the full autonomous UAV flight in an unknown environment. As an information source about obstacles digital camera was used. Developed algorithm uses the existing relations between the imaging system and the parameters read from the UAV autopilot. Synthesis of the proposed obstacle avoidance control law was oriented for computational simplicity. Presented algorithm was checked during simulation studies and in-flight tests.

Preliminary UAV Autopilot Integration and In-Flight Testing

The paper presents integration process of commercial autopilot. The autopilot was integrated with a fixed wing airframe. The main aim of this work was an experimental study of the autopilot integrated with a micro aircraft. A few manual and autonomous mode flights were performed. During the field trials the autopilot PID parameters were tuned and, as a result, the process of PID gains selection was described. Selected PID gains were presented. Certain telemetry parameters such as longitudinal and lateral position of aircraft, orientation angles, and angular velocities were logged during flight and analyzed. Maximum and minimum airspeeds at a desired altitude were measured and presented. Moreover, Received Signal Strange Indicator between ground station and UAV equipped with special antenna was measured and logged for radio communication quality and range checking. Presented analysis of the autopilots work and obtained results were used to assess the applicability of this hardware to next formation flight operations.