549 research outputs found
A Vision-based Scheme for Kinematic Model Construction of Re-configurable Modular Robots
Re-configurable modular robotic (RMR) systems are advantageous for their
reconfigurability and versatility. A new modular robot can be built for a
specific task by using modules as building blocks. However, constructing a
kinematic model for a newly conceived robot requires significant work. Due to
the finite size of module-types, models of all module-types can be built
individually and stored in a database beforehand. With this priori knowledge,
the model construction process can be automated by detecting the modules and
their corresponding interconnections. Previous literature proposed theoretical
frameworks for constructing kinematic models of modular robots, assuming that
such information was known a priori. While well-devised mechanisms and built-in
sensors can be employed to detect these parameters automatically, they
significantly complicate the module design and thus are expensive. In this
paper, we propose a vision-based method to identify kinematic chains and
automatically construct robot models for modular robots. Each module is affixed
with augmented reality (AR) tags that are encoded with unique IDs. An image of
a modular robot is taken and the detected modules are recognized by querying a
database that maintains all module information. The poses of detected modules
are used to compute: (i) the connection between modules and (ii) joint angles
of joint-modules. Finally, the robot serial-link chain is identified and the
kinematic model constructed and visualized. Our experimental results validate
the effectiveness of our approach. While implementation with only our RMR is
shown, our method can be applied to other RMRs where self-identification is not
possible
Improving robotic machining accuracy through experimental error investigation and modular compensation
Machining using industrial robots is currently limited to applications with low geometrical accuracies and soft materials. This paper analyzes the sources of errors in robotic machining and characterizes them in amplitude and frequency. Experiments under different conditions represent a typical set of industrial applications and allow a qualified evaluation. Based on this analysis, a modular approach is proposed to overcome these obstacles, applied both during program generation (offline) and execution (online). Predictive offline compensation of machining errors is achieved by means of an innovative programming system, based on kinematic and dynamic robot models. Real-time adaptive machining error compensation is also provided by sensing the real robot positions with an innovative tracking system and corrective feedback to both the robot and an additional high-dynamic compensation mechanism on piezo-actuator basis
Automatic Modeling for Modular Reconfigurable Robotic Systems: Theory and Practice
A modular reconfigurable robot consists of a collection of individual link and joint components that can be assembled into a number of different robot ge-ometries. Compared to a conventional industrial robot with fixed geometry, such a system can provide flexibility to the user to cope with a wide spectru
On adaptive robot systems for manufacturing applications
System adaptability is very important to current manufacturing practices due to frequent
changes in the customer needs. Two basic concepts that can be employed to achieve
system adaptability are flexible systems and modular systems. Flexible systems are fixed
integral systems with some adjustable components. Adjustable components have limited
ranges of parameter changes that can be made, thus restricting the adaptability of systems.
Modular systems are composed of a set of pre-existing modules. Usually, the parameters
of modules in modular systems are fixed, and thus increased system adaptability is
realized only by increasing the number of modules. Increasing the number of modules
could result in higher costs, poor positioning accuracy, and low system stiffness in the
context of manufacturing applications. In this thesis, a new idea was formulated: a
combination of the flexible system and modular system concepts. Systems developed
based on this new idea are called adaptive systems. This thesis is focused on adaptive
robot systems.
An adaptive robot system is such that adaptive components or adjustable parameters are
introduced upon the modular architecture of a robot system. This implies that there are
two levels to achieve system adaptability: the level where a set of modules is
appropriately assembled and the level where adjustable components or parameters are
specified. Four main contributions were developed in this thesis study.
First, a General Architecture of Modular Robots (GAMR) was developed. The starting
point was to define the architecture of adaptive robot systems to have as many
configuration variations as possible. A novel application of the Axiomatic Design
Theory (ADT) was applied to GAMR development. It was found that GAMR was the
one with the most coverage, and with a judicious definition of adjustable parameters.
Second, a system called Automatic Kinematic and Dynamic Analysis (AKDA) was
developed. This system was a foundation for synthesis of adaptive robot configurations.
In comparison with the existing approach, the proposed approach has achieved
systemization, generality, flexibility, and completeness. Third, this thesis research has
developed a finding that in modular system design, simultaneous consideration of both
kinematic and dynamic behaviors is a necessary step, owing to a strong coupling
between design variables and system behaviors. Based on this finding, a method for
simultaneous consideration of type synthesis, number synthesis, and dimension synthesis
was developed. Fourth, an adaptive modular Parallel Kinematic Machine (PKM) was
developed to demonstrate the benefits of adaptive robot systems in parallel kinematic
machines, which have found many applications in machine tool industries. In this
architecture, actuators and limbs were modularized, while the platforms were adjustable
in such a way that both the joint positions and orientations on the platforms can be
changed
Self-sufficiency of an autonomous self-reconfigurable modular robotic organism
In recent years, getting inspiration from simple but complex biological organisms, several advances have been seen in autonomous systems to mimic different behaviors that emerge from the interactions of a large group of simple individuals with each other and with the environment. Among several open issues a significantly important issue, not addressed so far, is the self-sufficiency, or in other words, the energetic autonomy of a modular robotic organism. This feature plays a pivotal role in maintaining a robotic organism\u27s autonomy for a longer period of time.
To address the challenges of self-sufficiency, a novel dynamic power management system (PMS) with fault tolerant energy sharing is proposed, realized in the form of hardware and software, and tested. The innate fault tolerant feature of the proposed PMS ensures power sharing in an organism despite docked faulty robotic modules. Due to the unavailability of sufficient number of real robotic modules a simulation framework called Replicator Power Flow Simulator is devised for the implementation of application software layer power management components. The simulation framework was especially devised because at the time of writing this work no simulation tool was available that could be used to perform power sharing and fault tolerance experiments at an organism level. The simulation experiments showed that the proposed application software layer dynamic power sharing policies in combination with the distributed fault tolerance feature in addition to self-sufficiency are expected to enhance the robustness and stability of a real modular robotic organism under varying conditions.Inspiriert von einfachen aber komplexen biologischen Organismen wurden in den letzten Jahren verschiedenste autonome Systeme entwickelt, welche die Verhaltensweisen einer großen Gruppe einfacher Individuen nachahmen. Das zentrale und bis heute ungelöste Problem dieser Organismen ist deren autonome Energieversorgung.
Zur Sicherstellung der Energieversorgung eines aus mehreren Robotern zusammengesetzten Organismus wurde in dieser Arbeit ein neuartiges Power-Management-System (PMS) konzipiert, aufgebaut und an einzelnen Robotermodulen und einem Roboterorganismus getestet. Die Hardware eines bestehenden Roboters wurde um ein neues Konzept erweitert, das auch bei fehlerhaften Robotermodulen einen Energieaustausch sicherstellt und so zu einer erhöhten Robustheit des PMS führen soll. Das entwickelte PMS wurde in modulare Roboter integriert und beispielhaft anhand eines Roboterorganismus getestet. In Ermangelung einer ausreichenden Anzahl von Robotermodulen wurde eine Simulationsumgebung entwickelt und die Software des PMS im Simulationsprogramm, anstatt im Roboter, implementiert. Dieses Simulationswerkzeug ist momentan das Einzige, das unter Berücksichtigung des Bewegungsmodells des Organismus den Energietransport im Roboterorganismus visuell darstellt und das Verhalten in verschiedenen Fehlerfällen simulieren kann. Die Simulationen und Messungen zeigen, dass das entwickelte PMS geeignet ist, die Energieversorgung von Roboterorganismen auch in Fehlerfällen sicherzustellen und so die Stabilität und Robustheit zu erhöhen
Graphical modelling of modular machines
This research is aimed at advancing machine design through specifying and implementing
(in "proof of concept" form) a set of tools which graphically model modular machines.
The tools allow mechanical building elements (or machine modules) to be selected and
configured together in a highly flexible manner so that operation of the chosen configuration
can be simulated and performance properties evaluated. Implementation of the tools
has involved an extension in capability of a proprietary robot simulation system. This research has resulted in a general approach to graphically modelling manufacturing machines
built from modular elements.
A focus of study has been on a decomposition of machine functionality leading to the establishment
of a library of modular machine primitives. This provides a useful source of
commonly required machine building elements for use by machine designers. Study has
also focussed on the generation of machine configuration tools which facilitate the construction
of a simulation model and ultimately the physical machine itself. Simulation aspects
of machine control are also considered which depict methods of manipulating a
machine model in the simulation phase. In addition methods of achieving machine programming
have been considered which specify the machine and its operational tasks.
Means of adopting common information data structures are also considered which can facilitate
interfacing with other systems, including the physical machine system constructed
as an issue of the simulation phase. Each of these study areas is addressed in its own context,
but collectively they provide a means of creating a complete modular machine design
environment which can provide significant assistance to machine designers.
Part of the methodology employed in the study is based on the use of the discrete event
simulation technique. To easily and effectively describe a modular machine and its activity
in a simulation model, a hierarchical ring and tree data structure has been designed and
implemented. The modularity and reconfigurability are accommodated by the data structure,
and homogeneous transformations are adopted to determine the spatial location and
orientation of each of the machine elements.
A three-level machine task programming approach is used to describe the machine's activities.
A common data format method is used to interface the machine design environment
with the physical machine and other building blocks of manufacturing systems (such as
CAD systems) where systems integration approaches can lead to enhanced product realisation.
The study concludes that a modular machine design environment can be created by employing
the graphical simulation approach together with a set of comprehensive configuration.
tools. A generic framework has been derived which outlines the way in which
machine design environments can be constructed and suggestions are made as to how the
proof of concept design environment implemented in this study can be advanced
Navigating in 3D Uneven Environments through Supervoxels and Nonlinear MPC
Navigating uneven and rough terrains presents difficulties, including stability, traversability, sensing, and robustness, making autonomous navigation in these terrains a challenging task. This study introduces a new approach for mobile robots to navigate uneven terrains. The method uses a compact graph of traversable regions on point cloud maps, created through the utilization of supervoxel representation of point clouds. By using this supervoxel graph, the method navigates the robot to any reachable goal pose by utilizing a navigation function and Nonlinear Model Predictive Controller (NMPC). The NMPC ensures kinodynamically feasible and collision-free motion plans, while the supervoxel-based geometric planning generates near-optimal plans by exploiting the terrain information. We conducted extensive navigation experiments in real and simulated 3D uneven terrains and found that the approach performs reliably. Additionally, we compared resulting motion plans to some state-of-the-art sampling-based motion planners in which our method outperformed them in terms of execution time and resulting path lengths. The method can also be adapted to meet specific behavior, like the shortest route or the path with the least slope route. The source code is available in a GitHub repository
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