טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentLivshits Arseny
SubjectA Laser-Range-Measurement Based Terrain-Following Concept
for Unmanned Aerial Vehicles
DepartmentDepartment of Aerospace Engineering
Supervisor Professor Moshe Idan
Full Thesis textFull thesis text - English Version


Abstract

                This research addresses the design and performance analysis of a laser range finder based terrain following system for unmanned aerial vehicles. A terrain following system is a type of an advanced auto pilot that allows an aircraft to maintain flight at a constant altitude above the terrain. The terrain following system can be integrated in tandem with additional autonomous systems thus enabling complex unmanned missions.

           

            The complexity and performance of such systems depend predominantly on the chosen concept and the layout of its hardware components, mainly its sensors. The related estimation and control algorithms designed for the terrain following task have to address also system uncertainties and disturbances.

           

            In this research, such a low cost, laser range finder based terrain following system is proposed, designed and analyzed. The problem is mathematically modeled and the various algorithmic components of the suggested approach are designed and evaluated. The various error factors are discussed and thoroughly examined. Building on that, an analytical error model for the system is derived. It should be noted that no stochastic error analysis are currently available in the terrain following literature. The error model provides a useful tool for performance investigation and parametric study.

           

            The error model is first validated using a numerical simulation environment constructed for this purpose. Then it is utilized to quantify the system tracking error, outline the preferred values for various system parameters in order to achieve higher terrain following performance, and mainly suggest the optimal pointing angle for the laser range finders. The effect of multiple sensors on performance is also examined and discussed.

           

            One of the primary factors impacting terrain following accuracy is the aircraft velocity. A trade off exists between higher aircraft velocity and terrain following performance. Therefore, the proposed approach was extended by incorporating adjustable aircraft velocity. This required the development of a parameter identification scheme which allows in-flight adaptation to varying terrain characteristics, thus improving both performance and robustness of the suggested approach.

            The performance of this extended approach was evaluated via numerical simulation methods. It was concluded that this adaptive approach provides additional performance improvement over the non-adaptive scheme and is highly suitable for multi-rotor unmanned aircraft that can easily change their flight velocity.

           

            Ultimately, this research developed, analyzed, and demonstrated the feasibility of a novel laser range finder based terrain following approach.

            Additionally, it was concluded that overall, the suggested analysis method and results grant an effective analytical method for gauging the terrain following performance for the suggested system.