This video presents a collision avoidance framework for mechanisms with complex geometries. The performance of the framework is showcased with the haptic interface HUG [3]. We are able to avoid contacts with the robot links and with moving objects in the environment in 1 kHz. The main contribution of our approach is its generic and extensible nature; it can be applied to any mechanism consisting of arbitrarily complex rigid bodies, in contrast to common solutions that use simplified models [2], [7]. In the preprocessing phase, first, the kinematic chain of the mechanism is described [1]. Second, we generate voxelized distance fields and point-sphere hierarchies for the geometry of each mechanism link and each object in the environment [6]. After that, our system requires only the joint angles and information of the environment state (e.g., object poses tracked by optical sensors) to compute collision avoidance forces. At runtime, each link is artificially dilated by a safety isosurface. If a point of an object goes through this surface, a normal force scaled by its penetration depth is computed and applied to the corresponding link. If humans are generically modeled as mechanisms and properly tracked, our system can also prevent collisions with them, ensuring save human-machine collaboration. Figure 1 illustrates the framework and its basic components. The multi-body collision computation architecture was first developed for virtual maintenance simulations with haptic feedback [5], [4], and thereafter extended to collision avoidance of mechanisms. A first prototype was previously published in [8].

This work presents an evaluation study in which the effects of a penalty-based and a constraint-based haptic rendering algorithm on the user performance and perception are analyzed. A total of N = 24 participants performed in a within-design study three variations of peg-in-hole tasks in a virtual environment after trials in an identically replicated real scenario as a reference. In addition to the two mentioned haptic rendering paradigms, two haptic devices were used, the HUG and a Sigma.7, and the force stiffness was also varied with maximum and half values possible for each device. Both objective (time and trajectory, collision performance, and muscular effort) and subjective ratings (contact perception, ergonomy, and workload) were recorded and statistically analyzed. The results show that the constraint-based haptic rendering algorithm with a lower stiffness than the maximum possible yields the most realistic contact perception, while keeping the visual inter-penetration between the objects roughly at around 15% of that caused by penalty-based algorithm (i.e., non perceptible in many cases). This result is even more evident with the HUG, the haptic device with the highest force display capabilities, although user ratings point to the Sigma.7 as the device with highest usability and lowest workload indicators. Altogether, the paper provides qualitative and quantitative guidelines for mapping properties of haptic algorithms and devices to user performance and perception.

The observation of robotic assembly tasks is required as feedback for decisions and adaption of the task execution on the current situation. A sequential Monte Carlo observation algorithm is proposed, which uses a fast and accurate collision detection algorithm as a reference model for the contacts between complex shaped parts. The main contribution of the paper is the extension of the classic random motion model in the propagation step with sampling methods known from the domain of probabilistic roadmap planning in order to increase the sample density in narrow passages of the configuration space. As a result, the observation performance can be improved and a risk of sample impoverishment reduced. Experimental validation is provided for a peg-in-hole task executed by a lightweight-robot arm equipped with joint torque sensors.

Collision detection and force computation between complex geometries are essential technologies for virtual reality and robotic applications. Penalty-based haptic rendering algorithms provide a fast collision computation solution, but they cannot avoid the undesired interpenetration between virtual objects, and have difficulties with thin non-watertight geometries. God object methods or constraint-based haptic rendering approaches have shown to solve this problem, but are typically complex to implement and computationally expensive. This paper presents an easy-to-implement god object approach applied to six-DoF penalty-based haptic rendering algorithms. Contact regions are synthesized to penalty force and torque values and these are used to compute the position of the god object on the surface. Then, the pose of this surface proxy is used to render stiff and stable six-DoF contacts with friction. Independently of the complexity of the used geometries, our implementation runs in only around 5 μs and the results show a maximal penetration error of the resolution used in the penalty-based haptic rendering algorithm.

We present a virtual reality platform which addresses and integrates some of the currently challenging research topics in the field of virtual assembly: realistic and practical scenarios with several complex geometries, bimanual six-DoF haptic interaction for hands and arms, and intuitive navigation in large workspaces. We put an especial focus on our collision computation framework, which is able to display stiff and stable forces in 1 kHz using a combination of penalty- and constraint-based haptic rendering methods. Interaction with multiple arbitrary geometries is supported in realtime simulations, as well as several interfaces, allowing for collaborative training experiences. Performance results for an exemplary car assembly sequence which show the readiness of the system are provided.

In the quest for better human-machine interfaces (HMIs) for teleoperation and virtual reality, we hereby present the first integrated application of medical ultrasound imaging to remotely control a virtual piano playing environment in real-time.

The growth of space debris is becoming a serious problem. There is an urgent need for mitigation measures based on maintenance, repair and de-orbiting technologies. Our video presents a virtual reality framework in which robotic maintenance tasks of satellites can be simulated interactively. The two key components of this framework are a realistic virtual reality simulation and an immersive interaction device. The peculiarity of the virtual reality simulation is the combination of a physics engine based on Bullet with an extremely efficient haptic rendering algorithm inspired by an enhanced version of the Voxmap-Pointshell Algorithm. A central logic module controls all states and objects in the virtual world. To enable the human operator an optimal immersion into the virtual environment, the DLR bimanual haptic device is used as interaction device. Equipped with two light-weight robot arms, this device is able to provide realistic haptic feedback at both human hands, while covering the major part of human operator's workspace. The applicability of this system is enhanced by additional force sensors, active hand interfaces with an additional degree of freedom, smart safety technologies and intuitive robot data augmentation. Our platform can be used for verification or training purposes of robotic systems interacting in space environments.

This work presents an evaluation study of two different collision feedback modalities for virtual assembly verification: visual and force feedback. Forty-three subjects performed several assembly tasks (peg-in-hole, narrow passage) designed with two levels of difficulty. The used haptic rendering algorithm is based on voxel and point data-structures. Both objective - time and collision performance - and subjective measures have been recorded and analyzed. The comparison of the feedback modalities revealed a clear and highly significant superiority of force feedback in virtual assembly scenarios. The objective data shows that whereas the assembly time is similar in most cases for both conditions, force collision feedback yields significantly smaller collision forces, which indicate higher assembly precision. The subjective ratings of the participants define the force feedback condition as the most appropriate for determining clearances and correcting collision configurations, being the best suited modality to predict mountability.

Abstract-This article accompanies a video that presents a bimanual haptic device composed of two DLR/KUKA Light weight Robot (LWR) arms. The LWRs have similar dimensions to human arms, and can be operated in torque and position control mode at an update rate of 1kHz. The two robots are mounted behind the user, such that the intersecting workspace of the robots and the human arms becomes maximal. In order to enhance user interaction, various hand interfaces and additional tactile feedback devices can be used together with the robots. The presented system is equipped with a thorough safety architecture that assures safe operation for human and robot. Additionally, sophisticated control strategies improve performance and guarantee stability. The introduced haptic system is well suited for versatile applications in remote and virtual environments, especially for large unsealed movements.

We present a benchmarking suite for rigid object collision detection and collision response schemes. The proposed benchmarking suite can evaluate both the performance as well as the quality of the collision response. The former is achieved by densely sampling the configuration space of a large number of highly detailed objects; the latter is achieved by a novel methodology that comprises a number of models for certain collision scenarios. With these models, we compare the force and torque signals both in direction and magnitude.