Learning Control of Fixed-Wing Unmanned Aerial Vehicles Using Fuzzy Neural Networks

A learning control strategy is preferred for the control and guidance of a fixed-wing unmanned aerial vehicle to deal with lack of modeling and flight uncertainties. For learning the plant model as well as changing working conditions online, a fuzzy neural network (FNN) is used in parallel with a conventional P (proportional) controller. Among the learning algorithms in the literature, a derivative-free one, sliding mode control (SMC) theory-based learning algorithm, is preferred as it has been proved to be computationally efficient in real-time applications. Its proven robustness and finite time converging nature make the learning algorithm appropriate for controlling an unmanned aerial vehicle as the computational power is always limited in unmanned aerial vehicles (UAVs). The parameter update rules and stability conditions of the learning are derived, and the proof of the stability of the learning algorithm is shown by using a candidate Lyapunov function. Intensive simulations are performed to illustrate the applicability of the proposed controller which includes the tracking of a three-dimensional trajectory by the UAV subject to time-varying wind conditions. The simulation results show the efficiency of the proposed control algorithm, especially in real-time control systems because of its computational efficiency

Navigation of an Autonomous Differential Drive Robot for Field Scouting in Semi-structured Environments

In recent years, the interests of introducing autonomous robots by growers into agriculture fields are rejuvenated due to the ever-increasing labor cost and the recent declining numbers of seasonal workers. The utilization of customized, autonomous agricultural robots has a profound impact on future orchard operations by providing low cost, meticulous inspection. Different sensors have been proven proficient in agrarian navigation including the likes of GPS, inertial, magnetic, rotary encoding, time of flight as well as vision. To compensate for anticipated disturbances, variances and constraints contingent to the outdoor semi-structured environment, a differential style drive vehicle will be implemented as an easily controllable system to conduct tasks such as imaging and sampling. In order to verify the motion control of a robot, custom-designed for strawberry fields, the task is separated into multiple phases to manage the over-bed and cross-bed operation needs. In particular, during the cross-bed segment an elevated strawberry bed will provide distance references utilized in a logic filter and tuned PID algorithm for safe and efficient travel. Due to the significant sources of uncertainty such as wheel slip and the vehicle model, nonlinear robust controllers are designed for the cross-bed motion, purely relying on vision feedback. A simple image filter algorithm was developed for strawberry row detection, in which pixels corresponding to the bed center will be tracked while the vehicle is in controlled motion. This incorporated derivation and formulation of a bounded uncertainty parameter that will be employed in the nonlinear control. Simulation of the entire system was subsequently completed to ensure the control capability before successful validation in multiple commercial farms. It is anticipated that with the developed algorithms the authentication of fully autonomous robotic systems functioning in agricultural crops will provide heightened efficiency of needed costly services; scouting, disease detection, collection, and distribution

전자유압밸브를 이용한 자율 주행 트랙터 조향성능 향상 연구

학위논문 (석사)-- 서울대학교 대학원 농업생명과학대학 바이오시스템·소재학부, 2017. 8. 김학진.The most common solution to achieving automated steering in an agricultural tractor is the use of an electric motor in parallel with a conventional hydrostatic valve-based hydraulic steering system owing to its simplicity and low cost. However, the existing overlap, or dead band, of a hydrostatic valve has limited its potential benefit to automated tractor steering in terms of providing various agricultural operations, including planting and spraying, at higher speeds. The main objective of this study was to develop an electro hydraulic steering system applicable to an auto-guidance system, and to compare the performance of the developed system with a conventional automatic steering system. A proportional-feedforward control algorithm was implemented to effectively compensate the non-linear behaviors of the hydraulic cylinders used for changing the steered wheel angle of the tractor. A computer-controlled hardware-in-the-loop electro-hydraulic steering simulator consisting of two different types of valve sub-systems s, i.e., hydrostatic valve and EHPV sub-system, was designed and built for the development of the steering control algorithms and to verify the feasibility of the developed steering controller for accurate steering of the system with acceptable response times. A field test was conducted using a Real Time Kinematic GPS based autonomous tractor equipped with the developed EHPV-based steering system and an EPS-based steering system used as a control to compare and investigate their potential in enhancing the path tracking functionality of an auto-guided system. The use of the EHPV-based steering controller was shown to improve the tracking error by about 29% and 50% for straight and curved paths, respectively, as compared to the EPS-based steering system.Chapter 1. Introduction 1 1.1. Study Background 1 1.2. Description of Tractor Steering System 6 1.3. Automatic Steering System 10 1.3.1. Electric Power Steering System 10 1.3.2. Electro Hydraulic Steering System 12 1.4. Review of Literature 13 1.5. Research Purpose 16 Chapter 2. Materials and Methods 17 2.1. Preliminary Performance Test of Conventional Steering System 17 2.1.1. Purpose of Preliminary Test 17 2.1.2. Zero-Load Test 21 2.1.3. Tractor Traveling Test 22 2.2. Hardware-in-the Loop Simulator 24 2.2.1. Hydraulic Circuit 25 2.2.2. Hardware Description 27 2.3. ISO 11783 Network 37 2.3.1. ISO 11783 (ISOBUS) 37 2.4. Steering Control Algorithm 45 2.4.1. Dead Time 48 2.4.2. Dead Band 51 2.4.3. Static Friction 57 2.5. Virtual Terminal 61 2.6. Vehicle Traveling Test 66 2.6.1. Hardware Configurations 66 2.6.2. Trajectory Tracking Control 72 2.6.3. Zero-Load Test 74 2.6.4. Sinusoidal Tracking Test 75 2.6.5. Path-Tracking and Test Methods 76 2.6.6. Evaluation Method of Path Tracking Deviation 79 Chapter 3. Results and Discussion 81 3.1. Preliminary Test Results of EPS-based Hydrostatic Steering System 81 3.2. Experiment Results of Steering Behavior of Hydrostatic Steering System using HIL simulator 85 3.3. Experiment Results of Electrohydraulic Steering System using HIL simulator 81 3.3.1. Dead-Time Approximation 88 3.3.2. Dead-Band Compensation 90 3.3.3. Static Friction Compensation 92 3.3.4. Steering Controller Test under Load Conditions 94 3.4. Performance Evaluation of Tractor Steering System 96 3.4.1. Zero Load Test 96 3.4.2. Sinusoidal Steering Test 96 3.4.3. Path-Tracking Test 99 Chapter 4. Conclusions 107Maste

Cognitive Vehicle Platooning in the Era of Automated Electric Transportation

Vehicle platooning is an important innovation in the automotive industry that aims at improving safety, mileage, efficiency, and the time needed to travel. This research focuses on the various aspects of vehicle platooning, one of the important aspects being analysis of different control strategies that lead to a stable and robust platoon. Safety of passengers being a very important consideration, the control design should be such that the controller remains robust under uncertain environments. As a part of the Department of Energy (DOE) project, this research also tries to show a demonstration of vehicle platooning using robots. In an automated highway scenario, a vehicle platoon can be thought of as a string of vehicles, following one another as a platoon. Being equipped by wireless communication capabilities, these vehicles communicate with one another to maintain their formation as a platoon, hence are cognitive. Autonomous capable vehicles in tightly spaced, computer-controlled platoons will lead to savings in energy due to reduced aerodynamic forces, as well as increased passenger comfort since there will be no sudden accelerations or decelerations. Impacts in the occurrence of collisions, if any, will be very low. The greatest benefit obtained is, however, an increase in highway capacity, along with reduction in traffic congestion, pollution, and energy consumption. Another aspect of this project is the automated electric transportation (AET). This aims at providing energy directly to vehicles from electric highways, thus reducing their energy consumption and CO2 emission. By eliminating the use of overhead wires, infrastructure can be upgraded by electrifying highways and providing energy on demand and in real time to moving vehicles via a wireless energy transfer phenomenon known as wireless inductive coupling. The work done in this research will help to gain an insight into vehicle platooning and the control system related to maintaining the vehicles in this formation

Aerial Vehicles

This book contains 35 chapters written by experts in developing techniques for making aerial vehicles more intelligent, more reliable, more flexible in use, and safer in operation.It will also serve as an inspiration for further improvement of the design and application of aeral vehicles. The advanced techniques and research described here may also be applicable to other high-tech areas such as robotics, avionics, vetronics, and space

A guiding vector field algorithm for path following control of nonholonomic mobile robots

In this paper we propose an algorithm for path following control of the nonholonomic mobile robot based on the idea of the guiding vector field (GVF). The desired path may be an arbitrary smooth curve in its implicit form, that is, a level set of a predefined smooth function. Using this function and the robot’s kinematic model, we design a GVF, whose integral curves converge to the trajectory. A nonlinear motion controller is then proposed which steers the robot along such an integral curve, bringing it to the desired path. We establish global convergence conditions for our algorithm and demonstrate its applicability and performance by experiments with wheeled robots

Contribuciones en el área del guiado autónomo de tractores agrícolas basado en la utilización de receptores GPS de bajo coste: mejora de la estabilidad y de la precisión de estos sistemas mediante el desarrollo de leyes de control asintóticamente estables y métodos geométricos

En esta tesis se realiza el estudio guiado de vehículos agrícolas con receptores GPS de bajo coste (receptores GPS L 1 de código) y se desarrollan diversas leyes de control y metodologías para mejorar su adaptación. En primer lugar, se analiza la validez de estos receptores para el guiado agrícola, obteniendo que es posible realizar el guiado autónomo a velocidades de hasta 9 km/h. En segundo lugar, se desarrolla una ley de control para el guiado en línea recta y en circunferencia, asintóticamente estable y convergente desde cualquier orientación del vehículo. Finalmente, se estudia el posicionamiento de la antena del receptor sobre el tractor y su influencia sobre el guiado y se desarrolla un método geométrico que obtiene el estado del vehículo a partir de los datos del receptor, con la antena en una posición adelantada del vehículo, incrementando la estabilidad, respuesta y tolerancia a ruido de los sistemas de guiado con receptores de bajo coste. Los métodos desarrollados se validan tanto de forma teórica como experimental.Departamento de Teoría de la Señal, Comunicaciones e Ingeniería Telemátic