Simon Schätzle

Evaluation of a vibrotactile feedback device for spatial guidance

In the present study, a vibrotactile feedback device for spatial guidance was evaluated in a tracking task paradigm. Participants (N = 18) had to translate and rotate virtual objects according to the vibrotactile vs. verbal cues without visual information. Both types of spatial guidance were evaluated using objective performance data (i.e. speed, accuracy) as well as subjective judgments. Results indicate that distinguishing spatial cues during the translational task was more difficult when being guided by vibrotactile feedback compared to verbal feedback. Nevertheless, individuals with vibrotactile guidance showed better performance at rotational tasks. Implications for the further design process and other areas of application are discussed.

The DLR bimanual haptic device with optimized workspace

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 1 kHz. 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 unscaled movements.

VibroTac: An ergonomic and versatile usable vibrotactile feedback device

This paper presents an ergonomic vibrotactile feedback device for the human arm. Due to the developed concept, the device can be used for a large spectrum of applications and a wide range of arm diameters since vibration segments are self-aligning to their intended positions. Furthermore, the device improves user convenience and movement capability as it is battery powered and controlled through a wireless communication interface. Vibrotactile stimuli are used to give collision feedback or guidance information to the human arm when interacting with a Virtual Reality scenario. The usefulness of this device has been shown in a Virtual Reality automotive assembly verification and a telerobotic system.

A functional anatomy based kinematic human hand model with simple size adaptation

For the purpose of ergonomic human-machine interaction and geometrical design of hand held haptic devices, a kinematic model that represents the functional anatomy of different human hands is desired. It is the goal of this paper to present a kinematic hand model that is based on human physiology and that is easily adaptable to represent various real human hand sizes. This is achieved by exploiting body proportions to derive finger segment lengths from the hand length. A partial hand model validation, involving index- and middle finger validation using a group of subjects, indicates that the use of body proportions offers a good estimate of finger length from a given hand length. Model estimated fingertip positions over a motion trajectory remain within reasonable limits when compared with experimental data for this subject group. The model is promising for usage in practical situations since only hand length, which is easy to measure or to obtain from literature, is required as an input. Phalange lengths, which are sparsely available from literature and difficult to measure, are generated by the model.

Towards Vibrotactile Direction and Distance Information for Virtual Reality and Workstations for Blind People

In the current paper psychophysical aspects of a vibrotactile feedback device were investigated and its potential of signal modulation was analyzed. We identified magnitude calibration factors for equal perceptions of the different stimulation locations of the device and determined the spatial acuity with which the user is able to correctly detect the stimulation’s location. Furthermore we investigated different approaches of vibrotactile stimulation for communicating direction and distance information to the human arm (motion guidance) and also explored different approaches of signal modulation for the transmission of additional information content.

A platform for bimanual virtual assembly training with haptic feedback in large multi-object environments

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.

VR-OOS: The DLR's virtual reality simulator for telerobotic on-orbit servicing with haptic feedback

The growth of space debris is becoming a severe issue that urgently requires mitigation measures based on maintenance, repair, and de-orbiting technologies. Such on-orbit servicing (OOS) missions, however, are delicate and expensive. Virtual Reality (VR) enables the simulation and training in a flexible and safe environment, and hence has the potential to drastically reduce costs and time, while increasing the success rate of future OOS missions. This paper presents a highly immersive VR system with which satellite maintenance procedures can be simulated interactively using visual and haptic feedback. The system can be used for verification and training purposes for human and robot systems interacting in space. Our framework combines unique realistic virtual reality simulation engines with advanced immersive interaction devices. The DLR bimanual haptic device HUG is used as the main user interface. The HUG is equipped with two light-weight robot arms and is able to provide realistic haptic feedback on both human arms. Additional devices provide vibrotactile and electrotactile feedback at the elbow and the fingertips. A particularity of the realtime simulation is the fusion of the Bullet physics engine with our haptic rendering algorithm, which is an enhanced version of the Voxmap-Pointshell Algorithm. Our haptic rendering engine supports multiple objects in the scene and is able to compute collisions for each of them within 1 msec, enabling realistic virtual manipulation tasks even for stiff collision configurations. The visualization engine ViSTA is used during the simulation to achieve photo-realistic effects, increasing the immersion. In order to provide a realistic experience at interactive frame rates, we developed a distributed system architecture, where the load of computing the physics simulation, haptic feedback and visualization of a complex scene is transferred to dedicated machines. The implementations are presented in detail and the performance of the overall system is validated. Additionally, a preliminary user study in which the virtual system is compared to a physical test bed shows the suitability of the VR-OOS framework.

Weight and Weightlessness Effects on Sensorimotor Performance During Manual Tracking

The effects of extra arm weight and weightlessness on sensorimotor performance were investigated in three studies. In all studies, subjects performed two-dimensional tracking tasks with a joystick. Results indicated that extra arm weight did not decrease tracking performance, but decreased acceleration variance. In weightlessness, tracking performance decreased and the control of movement impulses was deteriorated. This result pattern was found during water immersion as well as during spaceflight. The sensorimotor performance losses in weightlessness could be compensated by providing additional haptic cues with the input device.

VibroTac S: An Electronic Assistive Device for Blind and Visually Impaired People to Avoid Collisions

This paper presents a new concept for an electronic assistive device for blind and visually impaired people. Due to the integration of tiny distance sensors into the vibrotactile wristband VibroTac®, this novel device enables to detect obstacles in the user’s vicinity and thus to avoid collisions. The simultaneous monitoring of areas in different directions up to about one meter as well as an intuitive notification of the direction and the distance of detected objects through corresponding vibrating actuators is unique and makes its use very intuitive. A prototype was tested with three blind people in a mobility and in a table scenario. We received very positive and promising feedback and blind people rated the device to have great potential to be a useful aid in their daily life.