Automated Rendezvous & Docking Using 3D Vision

The robustness and accuracy of a vision system for motion estimation of a tumbling target satellite are enhanced by an adaptive Kalman filter. This allows a vision-guided robot to complete the grasping of the target even if occlusion occurs during the operation. A complete dynamics model, including aspects of orbital mechanics, is incorporated for accurate estimation. Based on the model, an adaptive Kalman filter is developed that estimates not only the system states but also all the model parameters such as the inertia ratio, center-of-mass, and the rotation of the principal axes of the target satellite. An experiment is conducted by using a robotic arm to move a satellite mockup according to orbital mechanics while the satellite pose is measured by a laser camera system. The measurements are sent to the Kalman filter, which, in turn, drives another robotic arm to grasp the target. The results demonstrate successful grasping even if the vision system is blocked for several seconds

Six-DOF Spacecraft Dynamics Simulator For Testing Translation and Attitude Control

This paper presents a method to control a manipulator system grasping a rigid-body payload so that the motion of the combined system in consequence of externally applied forces to be the same as another free-floating rigid-body (with different inertial properties). This allows zero-g emulation of a scaled spacecraft prototype under the test in a 1-g laboratory environment. The controller consisting of motion feedback and force/moment feedback adjusts the motion of the test spacecraft so as to match that of the flight spacecraft, even if the latter has flexible appendages (such as solar panels) and the former is rigid. The stability of the overall system is analytically investigated, and the results show that the system remains stable provided that the inertial properties of two spacecraft are different and that an upperbound on the norm of the inertia ratio of the payload to manipulator is respected. Important practical issues such as calibration and sensitivity analysis to sensor noise and quantization are also presented

Unified Modeling of Unconventional Modular and Reconfigurable Manipulation System

Customization of manipulator configurations using modularity and reconfigurability aspects is receiving much attention. Modules presented so far in literature deals with the conventional and standard configurations. This paper presents the 3D printable, light-weight and unconventional modules: MOIRs' Mark-2, to develop any custom `n'-Degrees-of-Freedom (DoF) serial manipulator even with the non-parallel and non-perpendicular jointed configuration. These unconventional designs of modular configurations seek an easy adaptable solution for both modular assembly and software interfaces for automatic modeling and control. A strategy of assembling the modules, automatic and unified modeling of the modular and reconfigurable manipulators with unconventional parameters is proposed in this paper using the proposed 4 modular units. A reconfigurable software architecture is presented for the automatic generation of kinematic and dynamic models and configuration files, through which, a designer can design, validate using visualization, plan and execute the motion of the developed configuration as required. The framework developed is based upon an open source platform called as Robot Operating System (ROS), which acts as a digital twin for the modular configurations. For the experimental demonstration, a 3D printed modular library is developed and an unconventional configuration is assembled, using the proposed modules followed by automatic modeling and control, for a single cell of the vertical farm setup

Optimal Control of Legged-Robots Subject to Friction Cone Constraints

A hierarchical control architecture is presented for energy-efficient control of legged robots subject to variety of linear/nonlinear inequality constraints such as Coulomb friction cones, switching unilateral contacts, actuator saturation limits, and yet minimizing the power losses in the joint actuators. The control formulation can incorporate the nonlinear friction cone constraints into the control without recourse to the common linear approximation of the constraints or introduction of slack variables. A performance metric is introduced that allows trading-off the multiple constraints when otherwise finding an optimal solution is not feasible. Moreover, the projection-based controller does not require the minimal-order dynamics model and hence allows switching contacts that is particularly appealing for legged robots. The fundamental properties of constrained inertia matrix derived are similar to those of general inertia matrix of the system and subsequently these properties are greatly exploited for control design purposes. The problem of task space control with minimum (point-wise) power dissipation subject to all physical constraints is transcribed into a quadratically constrained quadratic programming (QCQP) that can be solved by barrier methods

Autonomous Robots for Active Removal of Orbital Debris

This paper presents a vision guidance and control method for autonomous robotic capture and stabilization of orbital objects in a time-critical manner. The method takes into account various operational and physical constraints, including ensuring a smooth capture, handling line-of-sight (LOS) obstructions of the target, and staying within the acceleration, force, and torque limits of the robot. Our approach involves the development of an optimal control framework for an eye-to-hand visual servoing method, which integrates two sequential sub-maneuvers: a pre-capturing maneuver and a post-capturing maneuver, aimed at achieving the shortest possible capture time. Integrating both control strategies enables a seamless transition between them, allowing for real-time switching to the appropriate control system. Moreover, both controllers are adaptively tuned through vision feedback to account for the unknown dynamics of the target. The integrated estimation and control architecture also facilitates fault detection and recovery of the visual feedback in situations where the feedback is temporarily obstructed. The experimental results demonstrate the successful execution of pre- and post-capturing operations on a tumbling and drifting target, despite multiple operational constraints

Algoritmo de visão computacional para recomendação de um manipulador robótico baseado na pose de objetos

TCC (graduação) - Universidade Federal de Santa Catarina. Campus Blumenau. Engenharia de Controle e AutomaçãoUma das principais dificuldades na aplicação de manipuladores modulares é a escolha da configuração que atenda aos requisitos de uma tarefa estabelecida. Desta forma, vemos surgindo muitos trabalhos que buscam auxiliar o usuário otimizando esta decisão, dado um ou mais atributos da tarefa. Este trabalho propõe o projeto de um algoritmo de visão computacional que, diferente dos outros trabalhos encontrados, o usuário deve passar uma imagem com marcadores fiduciais (representando as poses da tarefa) e uma lista de manipuladores, para que, com base nos pontos, o programa retorne uma recomendação de manipulador. Através do uso da linguagem de programação Python, da biblioteca de visão computacional OpenCV e da biblioteca de robótica Pybotics, foi desenvolvido o algoritmo, que mostrou uma precisão aceitável na identificação das poses e uma recomendação de configuração satisfatória para estes pontos. Este trabalho contém o desenvolvimento do projeto, questões relevantes quanto a identificação dos pontos e recomendação dos manipuladores, e os testes realizados.One of the main difficulties in the application of modular manipulators is the choice of the configuration that meets the requirements of an established task. In this way, we see many works that seek to help the user optimizing this decision, given one or more attributes of the task. This work proposes the design of a computer vision algorithm that, unlike the other works found, the user must pass an image with fiducial markers (representing the task poses) and a list of manipulators, so that, based on the points, the program returns a manipulator recommendation. Through the use of the Python programming language, the OpenCV computer vision library and the Pybotics robotics library, the algorithm was developed, which showed acceptable accuracy in the identification of the poses and a satisfactory configuration recommendation for these points. This work contain the development of the project, relevant issues regarding the identification of the points and the recommendation of the manipulators, and the tests performed

A compliant-mechanism-based lockable prismatic joint for high-load morphing structures

Lockable joints are widely used in robotic systems and adaptive structures for energy management and/or topology reconfiguration. However, it is still challenging to design a joint with desired properties, including high locking load, infinite locking positions, short switching time, energy-efficient control, and a compact and lightweight structure. This paper aims at this open problem by presenting a novel piezoelectric (PZT) actuated lockable prismatic joint. This joint is a compliant mechanism (CM) consisting of a compound bridge-type compliant mechanism (CBCM) and a pair of compound multibeam parallelogram mechanisms (CMPMs). It can produce the required input/output stiffness to transmit large forces for high-load locking. It can also provide a desired input/output motion range for PZT actuation-based unlocking and for facilitating preloading adjustment. An analytical model is presented based on a compliance matrix method and the nonlinear model of the CMPM to predict the joint's static characteristics under various input/output conditions. A two-step optimization framework is proposed for locking applications. The theoretical study and nonlinear FEA/experimental verification confirm the feasibility of the design and the accuracy of the proposed model

Desarrollo de un modelo de sistematización para el proceso de diseño de mecanismos reconfigurables

En la presente memoria se desarrolla un trabajo sobre mecanismos reconfigurables, los cuales consisten en mecanismos capaces de alcanzar diferentes configuraciones a partir de la modificación del número, características y/o de la disposición relativa de sus elementos y/o pares cinemáticos con objeto de desempeñar diversas funciones. Debido a las ventajas que ofrece su polivalencia, estos mecanismos resultan muy interesantes para diferentes sectores, entre los cuales destacan la industria y el sector espacial. Con el fin de sistematizar el proceso de diseño de los mismos, se propone una metodología, dividida en tres bloques: en el primer bloque, se plantea la definición y análisis cinemático y dinámico de las configuraciones; en el segundo, el desarrollo del mecanismo de reconfiguración; y, en el tercero, la determinación del modo de activación de dicha reconfiguración. Junto a la descripción de los bloques propuestos, se proporcionan y desarrollan ejemplos de aplicación que sirvan para facilitar la comprensión de los conceptos expuestos.Dokumentu honetan mekanismo birkonfiguragarriei buruzko lana garatzen da, bere elementu edota junta zinematikoen kopurua, ezaugarriak edota antolaketa erlatiboa eraldatuz konfigurazioz alda daitezkeen eta, ondorioz, hainbat funtzio burutu ditzaketen mekanismoei buruz, hain zuzen ere. Haien balio-aniztasunak eskaintzen dituen abantailak direla eta, mekanismo hauek oso interesgarriak dira zenbait arlotarako, industria eta sektore espazialerako, batez ere. Diseinu prozesua sistematizatzeko xedez, metodologia bat proposatzen da, hiru bloketan banatuta: lehenengo blokean, konfigurazioen definizioa eta analisi zinematikoa eta dinamikoa planteatzen da; bigarrenean, birkonfigurazio mekanismoaren garapena; eta, hirugarrenean, birkonfigurazio horren aktibazio moduaren zehaztapena. Proposatutako blokeen deskribapenarekin batera, azaldutako kontzeptuen ulermena errazteko asmoz gauzatutako adibideak aurkezten dira.In this document a project about reconfigurable mechanisms is developed, which consist of a particular kind of mechanism capable of reaching different configurations by changing the number, characteristics and/or the relative disposition of their elements and/or kinematic joints in order to perform several functions. Due to the advantages offered by the polyvalence of these mechanisms, they are very interesting for different sectors, among which the industry and the space sector stand out. Aiming for the systematization of the design process of this type of mechanism, a methodology is proposed, divided in three main blocks: in the first block, the definition and study of the kinematics and dynamics of the configurations is set out; in the second one, the development of the reconfiguration mechanism; and, in the third one, the determination of the reconfiguration trigger. Along with the description of the blocks suggested, developed examples of application are provided, so as to help the understanding of the concepts involved

Desarrollo de un modelo de sistematización para el proceso de diseño de mecanismos reconfigurables

En la presente memoria se desarrolla un trabajo sobre mecanismos reconfigurables, los cuales consisten en mecanismos capaces de alcanzar diferentes configuraciones a partir de la modificación del número, características y/o de la disposición relativa de sus elementos y/o pares cinemáticos con objeto de desempeñar diversas funciones. Debido a las ventajas que ofrece su polivalencia, estos mecanismos resultan muy interesantes para diferentes sectores, entre los cuales destacan la industria y el sector espacial. Con el fin de sistematizar el proceso de diseño de los mismos, se propone una metodología, dividida en tres bloques: en el primer bloque, se plantea la definición y análisis cinemático y dinámico de las configuraciones; en el segundo, el desarrollo del mecanismo de reconfiguración; y, en el tercero, la determinación del modo de activación de dicha reconfiguración. Junto a la descripción de los bloques propuestos, se proporcionan y desarrollan ejemplos de aplicación que sirvan para facilitar la comprensión de los conceptos expuestos.Dokumentu honetan mekanismo birkonfiguragarriei buruzko lana garatzen da, bere elementu edota junta zinematikoen kopurua, ezaugarriak edota antolaketa erlatiboa eraldatuz konfigurazioz alda daitezkeen eta, ondorioz, hainbat funtzio burutu ditzaketen mekanismoei buruz, hain zuzen ere. Haien balio-aniztasunak eskaintzen dituen abantailak direla eta, mekanismo hauek oso interesgarriak dira zenbait arlotarako, industria eta sektore espazialerako, batez ere. Diseinu prozesua sistematizatzeko xedez, metodologia bat proposatzen da, hiru bloketan banatuta: lehenengo blokean, konfigurazioen definizioa eta analisi zinematikoa eta dinamikoa planteatzen da; bigarrenean, birkonfigurazio mekanismoaren garapena; eta, hirugarrenean, birkonfigurazio horren aktibazio moduaren zehaztapena. Proposatutako blokeen deskribapenarekin batera, azaldutako kontzeptuen ulermena errazteko asmoz gauzatutako adibideak aurkezten dira.In this document a project about reconfigurable mechanisms is developed, which consist of a particular kind of mechanism capable of reaching different configurations by changing the number, characteristics and/or the relative disposition of their elements and/or kinematic joints in order to perform several functions. Due to the advantages offered by the polyvalence of these mechanisms, they are very interesting for different sectors, among which the industry and the space sector stand out. Aiming for the systematization of the design process of this type of mechanism, a methodology is proposed, divided in three main blocks: in the first block, the definition and study of the kinematics and dynamics of the configurations is set out; in the second one, the development of the reconfiguration mechanism; and, in the third one, the determination of the reconfiguration trigger. Along with the description of the blocks suggested, developed examples of application are provided, so as to help the understanding of the concepts involved

Parallel robots with unconventional joints to achieve under-actuation and reconfigurability

The aim of the thesis is to define, analyze, and verify through simulations and practical implementations, parallel robots with unconventional joints that allow them to be under-actuated and/or reconfigurable. The new designs will be derived from the: * 6SPS robot (alternatively 6UPS or 6SPU, depending on the implementation) when considering the spatial case (i.e., robots with 3 degrees of freedom of rotation and 3 degrees of freedom of translation). * S-3SPS robot (alternatively S-3UPS or S-3SPU, depending on the implementation) when considering spherical robots (i.e., robots with 3 degrees of freedom of rotation). In both cases, we will see how, through certain geometric transformations, some of the standard joints can be replaced by lockable or non-holonomic joints. These substitutions permit reducing the number of legs (and hence the number of actuators needed to control the robot), without losing the robot's ability to bring its mobile platform to any position and orientation (in case of a spatial robot), or to any orientation (in case of a spherical robot), within its workspace. The expected benefit of these new designs is to obtain parallel robots with: * larger working spaces because the possibility of collisions between legs is reduced, and the number of joints (with their intrinsic range limitations) is also reduced; * lower weight because the number of actuators and joints is reduced; and * lower cost because the number of actuators and controllers is also reduced. The elimination of an actuator and the introduction of a motion constraint reduces in one the dimension of the space of allowed velocities attainable from a given configuration. As a result, it will be necessary, in general, to plan maneuvers to reach the desired configuration for the moving platform. Therefore, the obtained robots will only be suitable for applications where accuracy is required in the final position and a certain margin of error is acceptable in the generated trajectories.El objetivo de esta tesis es definir, analizar y verificar, mediante simulaciones e implementaciones prácticas, robots paralelos con articulaciones no-convencionales con el fin de incorporarles propiedades de sub-actuación y reconfigurabilidad. Los nuevos diseños se basaran en robots paralelos tipo: * 6SPS (alternativamente 6UPS o 6SPU, dependiendo de la implementación) para el caso de robot espacial (es decir, robots con 3 grados de libertad de rotación y de 3 grados de libertad de la traducción). * S-3SPS (alternativamente S-3UPS o S-3SPU, dependiendo de la implementación) para el caso de robot esférico (es decir, robots con 3 grados de libertad de rotación). En ambos casos, veremos cómo, a través de ciertas transformaciones geométricas, algunas de la articulaciones convencionales pueden ser sustituidas por articulaciones bloqueables o no holonómicos. Estas sustituciones permiten la reducción de la número de patas (y por tanto el número de actuadores necesarios para controlar el robot), sin perder la capacidad del robot para llevar su plataforma móvil a cualquier posición y orientación (en el caso de un robot espacial), o para cualquier orientación (en el caso de un robot esférico), dentro de su espacio de trabajo. El beneficio esperado de estos nuevos diseños es la obtención de robots paralelos con: * Espacios de trabajo mayores debido a que la posibilidad de colisiones entre las patas se reduce, y el número de articulaciones (con sus limitaciones intrínsecas de rango) también se reduce; * Menor peso debido a que el número de actuadores y de articulaciones se reduce; y * Un menor coste debido a que el número de actuadores y controladores también se reduce. La eliminación de un actuador y la introducción de una restricción de movimiento reduce, en uno, la dimensión del espacio de velocidades alcanzables para una configuración dada. Como resultado, será necesario, en general, planificar maniobras para llegar a la configuración deseada de la plataforma móvil. Por lo tanto, los robots obtenidos sólo serán adecuados para aplicaciones donde la precisión se requiera en la posición final y exista un cierto margen de error aceptable en las trayectorias generadasPostprint (published version