26 research outputs found
Safe and Efficient Human-Robot Collaboration Part I: Estimation of Human Arm Motions
No full textA significant barrier regarding a successful im-
plementation of fenceless robot cells into manufacturing ar-
eas with humans is given by the inefficiency due to safety
requirements. Robot motions have to be slowed down so that
an unexpected collision with a human does not result in human
injuries. This velocity reduction leads to longer cycle times
and, hence, fenceless robot cells turn out as uneconomic. In
this paper, a new approach for human-robot collaboration
in assembly tasks is presented. For a better performance of
the robot, methods are investigated on how the robot can
exploit a maximum performance while maintaining the safety
of collaborating humans. For this purpose, the kinematics and
dynamics of a human arm are described by a control-oriented
dynamic model to determine its capability and reachability.
Successful experiments validate the dynamic model as well as
a corresponding projection approach for calculating possible
movements of the human arm that may lead to a collision
with the robot. Finally, this information is used to calculate an
admissible path velocity that minimizes the danger of human
injuries
Triadocypris spitzbergensis Weitschat 1983
No full textTriadocypris spitzbergensis Weitschat 1983 a Fig. 3 L, M Triadocypris spitzbergensis Weitschat 1983 a: 309 –323, 10 figs.— 1983 b: 127–138.— Weitschat & Guhl 1994: 17 –31, figs. 1, 9. — Cohen et al. 1998: 258.— Kornicker & Sohn 2000: 22. Holotype GeologischPaläontologisches Institut und Museum, University of Hamburg (GPIHM), no. 2558. Type locality Sticky Keep Formation, Lower Triassic (subrobustus Zone); Flowerdalen, Spitsbergen, lat. 78 °N, long. 17 °E (Weitschat 1983 b). Material No material examined herein. Distribution Triassic of Spitsbergen. Diagnosis (from Weitschat 1983 b) Myodocopid with carapace 2.9–3.1 mm long; oval in lateral view. With small rostrum and shallow rostral incisur. Posterior margin forming very slight angle at midpoint, but fairly evenly rounded. Left valve overlaps right. Delicate dentition present along dorsal margin of each valve. Ornamentation composed of small, closely spaced pits. Gills welldeveloped, with three lobes on each side. Lateral eye with about 20 ommatidia. Foreign attachments. Weitschat & Guhl (1994: 17) described fossil ciliates attached to the body of one specimen. Comparisons Carapace differs from that of M. hollandica in having a shallower incisure and a different arrangement of central adductor muscle scars. Remarks Weitschat (1983 a: 314) referred this species to the Cypridinidae; however, the presence of five dorsal bristles on the second article of the first antenna indicates that the species belongs in the Cylindroleberididae. Weitschat (1983 a: 314) proposed a new subfamily Triadocypridininae Weitschat 1983 a for T. spitzbergensis, and Cohen et al. (1998: 254, 259) raised the status to family level as Triadocyprididae. The soft parts of T. spitzbergensis differ in some respects from those of extant Cylindroleberididae (Cohen et al. 1998: 258, 259), and the species may be a new family or subfamily. Nevertheless, the senior author believes it conservative at this time to interpret the differences as variations within the Cylindroleberididae. Several species known only from specimens without soft parts but with carapaces somewhat similar to that of T. spitzbergensis have been referred tentatively to Triadocypris.Published as part of Kornicker, Louis S., Van, Barry W. M., Bakel, Fraaije, René H. B. & Jagt, John W. M., 2006, Revision of Mesozoic Myodocopina (Ostracoda) and a new genus and species, Mesoleberis hollandica, from the Upper Cretaceous of Belgium and The Netherlands, pp. 15-54 in Zootaxa 1246 on pages 35-36, DOI: 10.5281/zenodo.17293
Towards a Real-Time Optimal Motion Framework
No full textVariable stiffness robots have a distinct feature that makes them especially interesting to application of energetic optimality: their ability to mechanically store and release energy. However, solving any kind of optimization problem for such highly nonlinear dynamics is only possible numerically, i.e. offline. In turn, numerical optimal solutions would only contribute a clear benefit for dynamic environments / tasks (apart from rather general insights), if they would be accessible/ generalizable in real-time. In this thesis, a general framework for executing near-optimal motions for Rigid Robots and Variable Stiffness Arms in real-time is proposed. The approach for the problem is formulated as follows. First, a set of prototypical optimization problems, which represent a reasonable set of motions are sought to execute is defined. For some of these distinct tasks, the optimization problem for an ensemble roughly covering the respective task space is solved. Then, the associated cost function is used as a clustering metric for learning manifolds of the optimal solution space and encode them in a dynamical system via Dynamic Movement Primitives (DMPs). Then, a distance and cost function based metric is proposed to generalize from the learned parameterizations to a new optimization problem in real-time. In short, this thesis intense to overcome some of the well known problems of optimal control and nonlinear optimization, which are offline schemes, and the one of learning with associated generalization, which is suboptimality. The developed verified on two robotic systems, namely the DLR Light Weight Robot and the DLR Hand-Arm System. Several dynamic tasks as ball throwing or energy optimal point-to-point motions are considered and experimental
validated
Industrial Human-Robot Collaboration: Maximizing Performance While Maintaining Safety
No full textFor many years, separated autonomous robotic systems have been an essential component in industrial manufacturing. In particular, these heavy-payload robots perform a wide range of tasks, where high precision and repeatability is crucial. A flexible adaptation of fast changing tasks or environments as well as the interaction with humans can rather not be realized by these types of robots. Recently, a paradigm shift regarding customer demand could be observed. Short product life-cycles as well as increasing individualization of products require flexible manufacturing processes. Therefore, novel light-weight robot technology was developed, which enables the collaboration of humans and robots. In particular, highly productive robots are combined with the high flexibility of humans. However, only a few collaborative applications have been established in industry, which is mainly due to the low efficiency, i.e., large cycle times caused by safety regulations.
The goal of this thesis is to maximize performance in collaborative applications, while maintaining safety. For this, assembly workplaces are analyzed, typical tasks identified, and the potential of collaborative robots is elaborated. Current safety regulations are analyzed in order to identify the challenges in safe human-robot collaboration. Then, a novel control method is presented, which enables intuitive, safe, and efficient control of robots. The Mirroring Human Arm Motions approach presents a velocity-limited trajectory generation, in particular, for orientations in quaternion space. This method is extended to an online via-point trajectory generation in order to enable an adjustment of velocity limits for guaranteeing safety in realtime. Furthermore, in collaborative applications particularly collisions with the human arm are likely to occur. Therefore, human-arm performance is analyzed and experiments similar to typical collaborative scenarios are executed, to determine the dynamic properties. By exploiting the obtained information on human arm dynamics, a novel approach to improve the performance of robot motions is presented. From the experiments, a simplified human arm model is derived, which enables the calculation of movements of the human into the path of the robot. With this approach, a maximum robot velocity depending on kinematic limitations of robots and human-in-the-loop constraints can be determined. This idea is further developed into a nonlinear optimization problem, where minimal-time motions are found and applications with low-cycle times can be realized. In order to enable flexible robot motions within the entire workspace of the robot, a generalization method using Dynamic Movement Primitives is presented. It contains a novel real-time consideration of spacial and kinematic constraints, to fulfill the requirements on safe human-robot collaboration. Experiments on a collaborative workbench prove the effectiveness of the presented methods. Finally, a novel airbag technology is proposed, which enables a protective coverage of dangerous tools and objects and protects humans against injuries, caused by a collision with the robot. The so called Robotic Airbag is inflated with pressured air to create a cushion around sharp edges of tool and object. Intrinsic safety is guaranteed, as the airbag is always inflated before initiating a robot motion. In order to exclude an affect of the tool functionality, the Robotic Airbag can be deflated whenever required. Experiments with a crash-test dummy, and finally with a volunteer, prove the functionality and compliance with current safety standards. In Summary, the presented methods in this thesis enable a significant improvement of efficiency and safety in collaborative applications
Skill parametrization approaches and skill architecture for human-robot interaction
No full textThere is an ongoing shift in industries from mass production to low-batch-production with highly individualized goods. This increases the programming effort required for the producing machines and robots, which is currently carried out by robot experts. For keeping the production economical, new programming approaches are required, allowing shop-floor workers to instruct robots. One approach is to develop robotic skills, which are pre-programmed software modules that only need to be parametrized by the shop-floor user. In this paper, a new software architecture for robot skills is presented, which aims at robustness and human-robot interaction. In addition, four basic demands on the skill parametrization are described that fasten up the process and increase intuitiveness for the user. We give several examples and implement a screwing skill and a pick & place skill, which are demonstrated in two case studies
Dynamic Projection of Human Motion for Safe and Efficient Human-Robot Collaboration
No full textIn the modern manufacturing process, novel technologies enable the collaboration between humans and robots, which increases productivity while keeping flexibility. However, these technologies also lead to new challenges, e.g., maximization of Human-Robot Collaboration (HRC) performance while ensuring safety for the human being in fenceless robot applications. In this paper, an approach of the dynamic human motion projection is proposed for typical assembly tasks. The human upper body is simplified as a five-degree-of-freedom (5-DOF) rigid-body model. A control-oriented projection model is proposed, and its parameters are estimated from the test data of human capability. Combined with a human-state estimator and a collision estimator, the ``worst-case" collision motion is projected in the HRC scenario. The dynamic projection method is feasible online. Finally, the estimated collision time is adopted to increase the robot's speed limit, which validates the improvement of HRC's efficiency
Safe and Efficient Human–Robot Collaboration Part II: Optimal Generalized Human-in-the-Loop Real-Time Motion Generation
No full textThe coexistence of humans and robots in fenceless robot cells requires robust safety precautions to prevent humans from being injured. Currently, safety is ensured by limiting the robot velocity, force, and power. This results in large cycle times and, hence, very inefficient industrial applications, where no amortization of the robotic system can be expected. In this letter, a novel method for improving the robot performance is presented that still complies with the international safety standards for collaborative robots. The approach of this letter is based on a projection of a human arm motion into the robot's path to estimate a possible collision with the robot. This idea is addressed in an optimization approach by minimizing the time needed by the robot to reach the goal position under human-in-the-loop constraints. The segmented path is optimized by solving a nonlinear programming problem, and the effect of crucial parameters is analyzed. To guarantee a flexible motion of the resulting optimized path, a generalization method using dynamic movement primitives and the compliance of constraints are proposed. Experiments validate this new method that significantly improves the efficiency of human–robot coexistence
Industrial human-robot collaboration: maximizing performance while maintaining safety
No full textThe goal of this thesis is to maximize performance in collaborative applications, while maintaining safety. For this, assembly workplaces are analyzed, typical tasks identified, and the potential of collaborative robots is elaborated. Current safety regulations are analyzed in order to identify the challenges in safe human-robot collaboration. Different methods are proposed to solve inefficiency in collaborative applications, in particular, intuitive programming of collaborative robots, efficient control with human-in-the-loop constraints, and a hardware solution, the Robotic Airbag.Das Ziel dieser Arbeit ist die Steigerung der Effizienz in kollaborativen Anwendungen, bei gleichzeitiger Einhaltung der Sicherheitsbestimmungen. Dazu werden Montagearbeitsplätze analysiert und das Potenzial kollaborativer Roboter erarbeitet. Aktuelle Sicherheitsvorschriften werden analysiert, um die Herausforderungen einer sicheren Mensch-Roboter-Zusammenarbeit zu identifizieren. Verschiedene Methoden wie intuitive Programmierung von kollaborativen Robotern, eine effiziente Steuerung mit Human-in-the-Loop Beschränkungen und eine Hardwarelösung - der Robotic Airbag - werden präsentiert
Unified Impedance and Hybrid Force-Position Controller with Kinestatic Filtering
No full textInteraction control is a mature, but still, current
area of research in robotics. Various approaches have been
developed for passive and active force regulation and tracking,
e.g. impedance control, direct force and hybrid force-position
control. The latter method implements a force feedback outer
loop on top of a position controller inner loop, where commands
are issued with respect to a compliant frame. However, if
the compliant frame undergoes a rigid transformation, e.g. in
order to specify the same task relative to another reference
frame, then commands can be rendered non-compliant with
the task at hand. As a consequence, the robot can be damaged
or hurt somebody, this is further aggravated by the rigidness
of a position controller. In the present paper, we propose a
unified impedance and hybrid force-position control scheme to
address such issues. The unified controller benefits from the
impedance control compliance while an explicit force value can
be achieved. Furthermore, we augment the designed controller
with a kinestatic filter, which ensures that the commanded pose
and wrench are consistent with a given task model. We validate
the designed system through experiments with a lightweight
robot (LWR). The proposed approach finds applications in
industrial settings where interactions with the environment are
required in order to fulfill a task and the system must be robust
w.r.t. input commands
End-Effector Airbags to Accelerate Human-Robot Collaboration
No full textA fundamental problem in human-robot collaboration
is to ensure safety for humans being located in the
workspace of the robot. Several new robots, referred to as
collaborative robots, are pushing into the market. Most of
these so-called co-bots have similar properties. They are small,
lightweight and designed with big roundings to ensure safety
in the case of a collision with a human. Equipped with torque
sensors, external torque observers, tactile skins, etc., they are
able to stop the robot when an emergency occurs. While
developing more and more co-bots, the main focus lies on the
robot itself. But to make a robot deployable, a special tool for
a defined task is needed. These tools are often sharp-edged and
dangerous in case of a collision with a human. In this paper
we present a new safety module for robots to ensure safety for
different tools in collaborative tasks. This module, filled with
air pressure during the robot motion, covers mounted tools and
carried workpieces. In case of a non or very slow moving robot,
the safety module is able to pull back and the tool is uncovered.
In our experiments we found out that we can increase the
velocity up to 1 m/s while satisfying the requirements of the
ISO/TS 15066 and retain the full functionality of the tool
