Design and control of a loader mechanism for the NMBU agricultural robot

Despite the development of new technologies, manual labour still continuous to play a large role within most modern agricultural operations, especially during harvest. Consequently, there is an increasing demand for new machines to reduce labour as a mean to limit costs, while increasing efficiency in a sustainable manner. This thesis concern itself with the design of a mechanism and control system for a robot arm that can substitute workers in logistical operations during strawberry harvest. More specifically, by lifting berry crates onto a robot platform and transporting them from the fields and to the packaging facilities. The robot arm is to be mounted on the platform composing a vehicle- manipulator system. As this thesis is connected to a general research project on agricultural robotics at the Norwegian University of Life Sciences, the chosen platform is the associated field robot Thorvald II. The thesis is divided into two parts, where Part I concerns the mechanical design of the robot arm, while Part II propose a system for controlling the mechanism. The design development process has involved assessments of available solutions before selecting components on the basis of controllability, mechanical properties and costs. The process of selection in Part II is however, based on finding solutions that are compatible with the robot platform’s network (Controller Area Network) and operating system (Robotic Operating System). Part I: Design and Mechanics The design of the robot arm presented in this thesis begun with a preliminary feasibility study conducted by Bjurbeck in September 2016. Following the assessment of this study, the robot arm is designed to have two degrees of freedom operating in the xz-plane. When mounted on the platform, the arm will be free to operate in a 3-dimensional space, as the platform moves in x and y-direction, and rotates around the z-axis. The arm is assembled from two parallel link pairs made from rectangular aluminium tubes, and a revolute and prismatic joint. Both joints are actuated by LinAk LA36 linear electric actuators. The end effector of the arm is a gripper head designed to grasp the handles of the strawberry crate. The gripper head is self-aligning with the crate’s orientation in order to reduce the precision of control needed to envelop and grasp the crate. The frame of the gripper head is made from aluminium angle profiles and sheet metal. A worm drive DC motor actuate the gripper claws via a double link mechanism. Part II: Modeling and Control The geometry of the design presented in Part I is modelled mathematically and the inverse kinematics solved analytically. The kinematics will be used in future implementation of a position control system. Two RoboteQ SDC2160 dual-channel controllers are chosen to control all four actuator mo- tors. The linear actuators are controlled in closed loop position tracking mode with absolute feedback. The gripper motor is controlled in open loop mode with end stop switches detecting the position of the claws. Experiments was conducted to match the controllers with the actuator motors. The experiments revealed firmware issues with the controller. The experiments also affirmed the controller need a script to operate the actuators efficiently. The thesis provides the foundations to build a prototype and write an operating script to test the mechanical design and control system.Til tross for den stadige utviklingen av ny teknologi spiller manuelt arbeid fortsatt en stor rolle i moderne landbruk, særlig i innhøsting. På grunn av den store arbeidkraften som trengs er det en stadig større etterspørsel etter nye maskiner som kan redusere behovet for manuelt arbeid for å redusere utgifter og effektivisere gårdsbruk på en bærekraftig måte. Denne masteroppgaven omhandler det mekaniske designet og reguleringssystemet til en robotarm laget for å kunne erstatte arbeidere i oppgaver tilknyttet logistikk ved innhøsting av jordbær. Dette gjøres ved at armen løfter kasser med bær opp på en robotplattform som transporterer kassene fra jordet og til et pakkeri. Robotarmen er da montert oppå plattformen. Siden oppgaven er tilknyttet et forskningsprosjekt i landbruksrobotikk ved Norges miljø- og biovitenskapelige universitet, var det naturlig å velge den universitetets robot Thorvald II som plattform.submittedVersionM-MP

Design of Self-Balancing Tracing Bicycle for Smart Car Competition Case Under Engineering Education

Smart car is an academic competition held for cultivating college students\u27 engineering ability in China for 16 years. To improve the performance of smart cars, this study integrates engineering education topics by introducing a smart car system with regard to the selection of key components, design of hardware and circuit boards, processing of sensor signals, as well as assembly, algorithms, and control. After completing this engineering education, students could achieve better results in the academic competition. According to the K model rules of the 16th smart car competition, a self-balancing autonomous tracking bicycle based on steering gear control is designed and developed. A gyroscope is used to detect the posture of the bicycle. It inductively receives the centerline of the track and then combined with the PID control algorithm realizes the autonomous tracking. The whole process from mechanical structure optimization and electronic circuit design to algorithm design, debugging, and competition runs through the CDIO of engineering education, realizing the cultivation of compound engineering innovative abilities

Design and Development of an Automated Mobile Manipulator for Industrial Applications

This thesis presents the modeling, control and coordination of an automated mobile manipulator. A mobile manipulator in this investigation consists of a robotic manipulator and a mobile platform resulting in a hybrid mechanism that includes a mobile platform for locomotion and a manipulator arm for manipulation. The structural complexity of a mobile manipulator is the main challenging issue because it includes several problems like adapting a manipulator and a redundancy mobile platform at non-holonomic constraints. The objective of the thesis is to fabricate an automated mobile manipulator and develop control algorithms that effectively coordinate the arm manipulation and mobility of mobile platform. The research work starts with deriving the motion equations of mobile manipulators. The derivation introduced here makes use of motion equations of robot manipulators and mobile platforms separately, and then integrated them as one entity. The kinematic analysis is performed in two ways namely forward & inverse kinematics. The motion analysis is performed for various WMPs such as, Omnidirectional WMP, Differential three WMP, Three wheeled omni-steer WMP, Tricycle WMP and Two steer WMP. From the obtained motion analysis results, Differential three WMP is chosen as the mobile platform for the developed mobile manipulator. Later motion analysis is carried out for 4-axis articulated arm. Danvit-Hartenberg representation is implemented to perform forward kinematic analysis. Because of this representation, one can easily understand the kinematic equation for a robotic arm. From the obtained arm equation, Inverse kinematic model for the 4-axis robotic manipulator is developed. Motion planning of an intelligent mobile robot is one of the most vital issues in the field of robotics, which includes the generation of optimal collision free trajectories within its work space and finally reaches its target position. For solving this problem, two evolutionary algorithms namely Particle Swarm Optimization (PSO) and Artificial Immune System (AIS) are introduced to move the mobile platform in intelligent manner. The developed algorithms are effective in avoiding obstacles, trap situations and generating optimal paths within its unknown environments. Once the robot reaches its goal (within the work space of the manipulator), the manipulator will generate its trajectories according to task assigned by the user. Simulation analyses are performed using MATLAB-2010 in order to validate the feasibility of the developed methodologies in various unknown environments. Additionally, experiments are carried out on an automated mobile manipulator. ATmega16 Microcontrollers are used to enable the entire robot system movement in desired trajectories by means of robot interface application program. The control program is developed in robot software (Keil) to control the mobile manipulator servomotors via a serial connection through a personal computer. To support the proposed control algorithms both simulation and experimental results are presented. Moreover, validation of the developed methodologies has been made with the ER-400 mobile platform

A graph-theory-based C-space path planner for mobile robotic manipulators in close-proximity environments

In this thesis a novel guidance method for a 3-degree-of-freedom robotic manipulator arm in 3 dimensions for Improvised Explosive Device (IED) disposal has been developed. The work carried out in this thesis combines existing methods to develop a technique that delivers advantages taken from several other guidance techniques. These features are necessary for the IED disposal application. The work carried out in this thesis includes kinematic and dynamic modelling of robotic manipulators, T-space to C-space conversion, and path generation using Graph Theory to produce a guidance technique which can plan a safe path through a complex unknown environment. The method improves upon advantages given by other techniques in that it produces a suitable path in 3-dimensions in close-proximity environments in real time with no a priori knowledge of the environment, a necessary precursor to the application of this technique to IED disposal missions. To solve the problem of path planning, the thesis derives the kinematics and dynamics of a robotic arm in order to convert the Euclidean coordinates of measured environment data into C-space. Each dimension in C-space is one control input of the arm. The Euclidean start and end locations of the manipulator end effector are translated into C-space. A three-dimensional path is generated between them using Dijkstra’s Algorithm. The technique allows for a single path to be generated to guide the entire arm through the environment, rather than multiple paths to guide each component through the environment. The robotic arm parameters are modelled as a quasi-linear parameter varying system. As such it requires gain scheduling control, thus allowing compensation of the non-linearities in the system. A Genetic Algorithm is applied to tune a set of PID controllers for the dynamic model of the manipulator arm so that the generated path can then be followed using a conventional path-following algorithm. The technique proposed in this thesis is validated using numerical simulations in order to determine its advantages and limitations

Using a mobile robot for hazardous substances detection in a factory environment

Dupla diplomação com a UTFPR - Universidade Tecnológica Federal do ParanáIndustries that work with toxic materials need extensive security protocols to avoid accidents. Instead of having fixed sensors, the concept of assembling the sensors on a mobile robot that performs the scanning through a defined path is cheaper, configurable and adaptable. This work describes a mobile robot, equipped with several gas sensors and LIDAR, that follows a trajectory based on waypoints, simulating a working Autonomous Guided Vehicle (AGV). At the same time, the robot keeps measuring for toxic gases. In other words, the robot follows the trajectory while the gas concentration is under a defined value. Otherwise, it starts the autonomous leakage search based on a search algorithm that allows to find the leakage position avoiding obstacles in real time. The proposed methodology is verified in simulation based on a model of the real robot. Therefore, three path plannings were developed and their performance compared. A Light Detection And Ranging (LIDAR) device was integrated with the path planning to propose an obstacle avoidance system with a dilation technique to enlarge the obstacles, thus, considering the robot’s dimensions. Moreover, if needed, the robot can be remotely operated with visual feedback. In addition, a controller was made for the robot. Gas sensors were embedded in the robot with Finite Impulse Response (FIR) filter to process the data. A low cost AGV was developed to compete in Festival Nacional de Robótica (Portuguese Robotics Open) 2019 - Gondomar, describing the robot’s control and software solution to the competition.As indústrias que trabalham com materiais tóxicos necessitam de extensos protocolos de segurança para evitar acidentes. Ao invés de ter sensores estáticos, o conceito de instalar sensores em um robô móvel que inspeciona através de um caminho definido é mais barato, configurável e adaptável. O presente trabalho descreve um robô móvel, equipado com vários sensores de gás e LIDAR, que percorre uma trajetória baseada em pontos de controle, simulando um AGV em trabalho. Em simultâneo são efetuadas medidas de gases tóxicos. Em outras palavras, o robô segue uma trajetória enquanto a concentração de gás está abaixo de um valor definido. Caso contrário, inicia uma busca autônoma de vazamento de gás com um algoritmo de busca que permite achar a posição do gás evitando os obstáculos em tempo real. A metodologia proposta é verificada em simulação. Três algoritmos de planejamento de caminho foram desenvolvidos e suas performances comparadas. Um LIDAR foi integrado com o planejamento de caminho para propôr um sistema de evitar obstáculos. Além disso, o robô pode ser operado remotamente com auxílio visual. Foi feito um controlador para o robô. Sensores de gás foram embarcados no robô com um filtro de resposta ao impulso finita para processar as informações. Um veículo guiado automático de baixo custo foi desenvolvido para competir no Festival Nacional de Robótica 2019 - Gondomar. O controle do veículo foi descrito com o programa de solução para a competição

Analysis of inverse simulation algorithms with an application to planetary rover guidance and control

Rover exploration is a contributing factor to driving the relevant research forward on guidance, navigation, and control (GNC). Yet, there is a need for incorporating the dynamic model into the controller for increased accuracy. Methods that use the model are limited by issues such as linearity, systems affine in the control, number of inputs and outputs. Inverse Simulation is a more general approach that uses a mathematical model and a numerical scheme to calculate the control inputs necessary to produce a desired response defined using the output variables. This thesis develops the Inverse Simulation algorithm for a general state space model and utilises a numerical Newton-Raphson scheme to converge to the inputs using two approaches: The Differentiation method converges based on the state and output equations. The Integration method converges based on whether the output matches the desired and is suitable for grey or black-box models. The thesis offers extensive insights into the requirements and application of Inverse Simulation and the performance parameters. Attention is given to how the inputs and outputs affect the Jacobian formulation and ensure an efficient solution. The linear case and the relationship with feedback linearisation are examined. Examples are given using simple mechanical systems and an example is also given as to how Inverse Simulation can be used for determining system input disturbances. Inverse Simulation is applied for the first time for guidance and control of a fourwheeled, differentially driven rover. The desired output is the time history of the desired trajectory and is used to produce the required control inputs. The control inputs are nominal and are applied to the rover without additional correction. Using insights from the system’s physics and actuation, the Differentiation and Integration schemes are developed based on the general method presented in this thesis. The novel Differentiation scheme employs a non-square Jacobian. The method provides very accurate position and orientation control of the rover while considering the limitations of the model used. Finally, the application of Inverse Simulation to the rover is supported by a review of current designs that resulted in a rover taxonomy

Space Transportation System and associated payloads: Glossary, acronyms, and abbreviations

A collection of acronyms in everyday use concerning shuttle activities is presented. A glossary of terms pertaining to the Space Transportation System is included