Stereo Viewing and Virtual Reality Technologies in Mobile Robot Teleguide

“This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." “Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.” DOI: 10.1109/TRO.2009.2028765The use of 3-D stereoscopic visualization may provide a user with higher comprehension of remote environments in teleoperation when compared with 2-D viewing, in particular, a higher perception of environment depth characteristics, spatial localization, remote ambient layout, faster system learning, and decision performance. Works in the paper have demonstrated how stereo vision contributes to the improvement of the perception of some depth cues, often for abstract tasks, while it is hard to find works addressing stereoscopic visualization in mobile robot teleguide applications. This paper intends to contribute to this aspect by investigating the stereoscopic robot teleguide under different conditions, including typical navigation scenarios and the use of synthetic and real images. This paper also investigates how user performance may vary when employing different display technologies. Results from a set of test trials run on seven virtual reality systems, from laptop to large panorama and from head-mounted display to Cave automatic virtual environment (CAVE), emphasized few aspects that represent a base for further investigations as well as a guide when designing specific systems for telepresence.Peer reviewe

Telepresence: Design, Implementation and Study of an HMD-controlled Avatar with a Mechatronic Approach

Telepresence describes technologies that allow users to remotely experience the sensation of being present at an event without being physically present. An avatar exists to represent the user whilst in a remote location and is tasked to collect stimuli from its immediate surroundings to be delivered to the user for consumption. With the advent of recent developments in Virtual Reality technology, viz., head-mounted displays (HMDs), new possibilities have been enabled in the field of Telepresence. The main focus of this thesis is to develop a solution for visual Telepresence, where an HMD is used to control the direction of a camera‟s viewpoint, such that the user‟s head is tracked by the avatar, while providing visual feedback to the user. The design and development of the device follows a mechatronic approach, where a real time operating system (RTOS) is used in conjunction with a microcontroller for mechanical actuator control. The first-generation prototype, HOG-1 (HMD-Operated Gimbal, rev. 1), developed for this thesis serves as a foundation for study; the implementation and analysis of the prototype contributes to the state of the art by providing a clearer glimpse of hardware and software requirements that are necessary to construct an improved model. Additionally, qualitative and quantitative measurements are developed in the process of this research

Development and evaluation of mixed reality-enhanced robotic systems for intuitive tele-manipulation and telemanufacturing tasks in hazardous conditions

In recent years, with the rapid development of space exploration, deep-sea discovery, nuclear rehabilitation and management, and robotic-assisted medical devices, there is an urgent need for humans to interactively control robotic systems to perform increasingly precise remote operations. The value of medical telerobotic applications during the recent coronavirus pandemic has also been demonstrated and will grow in the future. This thesis investigates novel approaches to the development and evaluation of a mixed reality-enhanced telerobotic platform for intuitive remote teleoperation applications in dangerous and difficult working conditions, such as contaminated sites and undersea or extreme welding scenarios. This research aims to remove human workers from the harmful working environments by equipping complex robotic systems with human intelligence and command/control via intuitive and natural human-robot- interaction, including the implementation of MR techniques to improve the user's situational awareness, depth perception, and spatial cognition, which are fundamental to effective and efficient teleoperation. The proposed robotic mobile manipulation platform consists of a UR5 industrial manipulator, 3D-printed parallel gripper, and customized mobile base, which is envisaged to be controlled by non-skilled operators who are physically separated from the robot working space through an MR-based vision/motion mapping approach. The platform development process involved CAD/CAE/CAM and rapid prototyping techniques, such as 3D printing and laser cutting. Robot Operating System (ROS) and Unity 3D are employed in the developing process to enable the embedded system to intuitively control the robotic system and ensure the implementation of immersive and natural human-robot interactive teleoperation. This research presents an integrated motion/vision retargeting scheme based on a mixed reality subspace approach for intuitive and immersive telemanipulation. An imitation-based velocity- centric motion mapping is implemented via the MR subspace to accurately track operator hand movements for robot motion control, and enables spatial velocity-based control of the robot tool center point (TCP). The proposed system allows precise manipulation of end-effector position and orientation to readily adjust the corresponding velocity of maneuvering. A mixed reality-based multi-view merging framework for immersive and intuitive telemanipulation of a complex mobile manipulator with integrated 3D/2D vision is presented. The proposed 3D immersive telerobotic schemes provide the users with depth perception through the merging of multiple 3D/2D views of the remote environment via MR subspace. The mobile manipulator platform can be effectively controlled by non-skilled operators who are physically separated from the robot working space through a velocity-based imitative motion mapping approach. Finally, this thesis presents an integrated mixed reality and haptic feedback scheme for intuitive and immersive teleoperation of robotic welding systems. By incorporating MR technology, the user is fully immersed in a virtual operating space augmented by real-time visual feedback from the robot working space. The proposed mixed reality virtual fixture integration approach implements hybrid haptic constraints to guide the operator’s hand movements following the conical guidance to effectively align the welding torch for welding and constrain the welding operation within a collision-free area. Overall, this thesis presents a complete tele-robotic application space technology using mixed reality and immersive elements to effectively translate the operator into the robot’s space in an intuitive and natural manner. The results are thus a step forward in cost-effective and computationally effective human-robot interaction research and technologies. The system presented is readily extensible to a range of potential applications beyond the robotic tele- welding and tele-manipulation tasks used to demonstrate, optimise, and prove the concepts

Impact of Imaging and Distance Perception in VR Immersive Visual Experience

Virtual reality (VR) headsets have evolved to include unprecedented viewing quality. Meanwhile, they have become lightweight, wireless, and low-cost, which has opened to new applications and a much wider audience. VR headsets can now provide users with greater understanding of events and accuracy of observation, making decision-making faster and more effective. However, the spread of immersive technologies has shown a slow take-up, with the adoption of virtual reality limited to a few applications, typically related to entertainment. This reluctance appears to be due to the often-necessary change of operating paradigm and some scepticism towards the "VR advantage". The need therefore arises to evaluate the contribution that a VR system can make to user performance, for example to monitoring and decision-making. This will help system designers understand when immersive technologies can be proposed to replace or complement standard display systems such as a desktop monitor. In parallel to the VR headsets evolution there has been that of 360 cameras, which are now capable to instantly acquire photographs and videos in stereoscopic 3D (S3D) modality, with very high resolutions. 360° images are innately suited to VR headsets, where the captured view can be observed and explored through the natural rotation of the head. Acquired views can even be experienced and navigated from the inside as they are captured. The combination of omnidirectional images and VR headsets has opened to a new way of creating immersive visual representations. We call it: photo-based VR. This represents a new methodology that combines traditional model-based rendering with high-quality omnidirectional texture-mapping. Photo-based VR is particularly suitable for applications related to remote visits and realistic scene reconstruction, useful for monitoring and surveillance systems, control panels and operator training. The presented PhD study investigates the potential of photo-based VR representations. It starts by evaluating the role of immersion and user’s performance in today's graphical visual experience, to then use it as a reference to develop and evaluate new photo-based VR solutions. With the current literature on photo-based VR experience and associated user performance being very limited, this study builds new knowledge from the proposed assessments. We conduct five user studies on a few representative applications examining how visual representations can be affected by system factors (camera and display related) and how it can influence human factors (such as realism, presence, and emotions). Particular attention is paid to realistic depth perception, to support which we develop target solutions for photo-based VR. They are intended to provide users with a correct perception of space dimension and objects size. We call it: true-dimensional visualization. The presented work contributes to unexplored fields including photo-based VR and true-dimensional visualization, offering immersive system designers a thorough comprehension of the benefits, potential, and type of applications in which these new methods can make the difference. This thesis manuscript and its findings have been partly presented in scientific publications. In particular, five conference papers on Springer and the IEEE symposia, [1], [2], [3], [4], [5], and one journal article in an IEEE periodical [6], have been published

Intuitive Robot Teleoperation Based on Haptic Feedback and 3D Visualization

Robots are required in many jobs. The jobs related to tele-operation may be very challenging and often require reaching a destination quickly and with minimum collisions. In order to succeed in these jobs, human operators are asked to tele-operate a robot manually through a user interface. The design of a user interface and of the information provided in it, become therefore critical elements for the successful completion of robot tele-operation tasks. Effective and timely robot tele-navigation mainly relies on the intuitiveness provided by the interface and on the richness and presentation of the feedback given. This project investigated the use of both haptic and visual feedbacks in a user interface for robot tele-navigation. The aim was to overcome some of the limitations observed in a state of the art works, turning what is sometimes described as contrasting into an added value to improve tele-navigation performance. The key issue is to combine different human sensory modalities in a coherent way and to benefit from 3-D vision too. The proposed new approach was inspired by how visually impaired people use walking sticks to navigate. Haptic feedback may provide helpful input to a user to comprehend distances to surrounding obstacles and information about the obstacle distribution. This was proposed to be achieved entirely relying on on-board range sensors, and by processing this input through a simple scheme that regulates magnitude and direction of the environmental force-feedback provided to the haptic device. A specific algorithm was also used to render the distribution of very close objects to provide appropriate touch sensations. Scene visualization was provided by the system and it was shown to a user coherently to haptic sensation. Different visualization configurations, from multi-viewpoint observation to 3-D visualization, were proposed and rigorously assessed through experimentations, to understand the advantages of the proposed approach and performance variations among different 3-D display technologies. Over twenty users were invited to participate in a usability study composed by two major experiments. The first experiment focused on a comparison between the proposed haptic-feedback strategy and a typical state of the art approach. It included testing with a multi-viewpoint visual observation. The second experiment investigated the performance of the proposed haptic-feedback strategy when combined with three different stereoscopic-3D visualization technologies. The results from the experiments were encouraging and showed good performance with the proposed approach and an improvement over literature approaches to haptic feedback in robot tele-operation. It was also demonstrated that 3-D visualization can be beneficial for robot tele-navigation and it will not contrast with haptic feedback if it is properly aligned to it. Performance may vary with different 3-D visualization technologies, which is also discussed in the presented work

Remote Visual Observation of Real Places Through Virtual Reality Headsets

Virtual Reality has always represented a fascinating yet powerful opportunity that has attracted studies and technology developments, especially since the latest release on the market of powerful high-resolution and wide field-of-view VR headsets. While the great potential of such VR systems is common and accepted knowledge, issues remain related to how to design systems and setups capable of fully exploiting the latest hardware advances. The aim of the proposed research is to study and understand how to increase the perceived level of realism and sense of presence when remotely observing real places through VR headset displays. Hence, to produce a set of guidelines that give directions to system designers about how to optimize the display-camera setup to enhance performance, focusing on remote visual observation of real places. The outcome of this investigation represents unique knowledge that is believed to be very beneficial for better VR headset designs towards improved remote observation systems. To achieve the proposed goal, this thesis presents a thorough investigation of existing literature and previous researches, which is carried out systematically to identify the most important factors ruling realism, depth perception, comfort, and sense of presence in VR headset observation. Once identified, these factors are further discussed and assessed through a series of experiments and usability studies, based on a predefined set of research questions. More specifically, the role of familiarity with the observed place, the role of the environment characteristics shown to the viewer, and the role of the display used for the remote observation of the virtual environment are further investigated. To gain more insights, two usability studies are proposed with the aim of defining guidelines and best practices. The main outcomes from the two studies demonstrate that test users can experience an enhanced realistic observation when natural features, higher resolution displays, natural illumination, and high image contrast are used in Mobile VR. In terms of comfort, simple scene layouts and relaxing environments are considered ideal to reduce visual fatigue and eye strain. Furthermore, sense of presence increases when observed environments induce strong emotions, and depth perception improves in VR when several monocular cues such as lights and shadows are combined with binocular depth cues. Based on these results, this investigation then presents a focused evaluation on the outcomes and introduces an innovative eye-adapted High Dynamic Range (HDR) approach, which the author believes to be of great improvement in the context of remote observation when combined with eye-tracked VR headsets. Within this purpose, a third user study is proposed to compare static HDR and eye-adapted HDR observation in VR, to assess that the latter can improve realism, depth perception, sense of presence, and in certain cases even comfort. Results from this last study confirmed the author expectations, proving that eye-adapted HDR and eye tracking should be used to achieve best visual performances for remote observation in modern VR systems