No abstract

No abstract

No abstract

Vibrotactile signals convey the touch-based characteristics of object surfaces felt through a tool. They particularly enhance the quality of human-machine interactions by providing realistic haptic perception of textures. In this paper, inspired by the similarities observed between vibrotactile texture signals and speech signals, we present a novel vibrotactile texture codec for bilateral teleoperation, based on well-known speech coding techniques. The proposed low bitrate, high quality codec preserves not only the spectral signature vital to the general feel of the texture, but also important temporal features of the texture signal. We report a compression ratio of 8:1 (12.5%) with a constant output bitrate of 4 kbps, and we validate the perceptual transparency of the codec via rigorous subjective tests and analyses.

Teleoperation systems give us the ability to immerse ourselves in environments that are remote or inaccessible to human beings. Teleoperation systems are also referred to as telemanipulation systems, considering their ability to provide manipulations in a remote environment. In addition to auditory and visual feedback, the bidirectional exchange of haptic information enables the human operator to interact physically with the remote objects. Throughout the years, in haptics and control engineering fields, researchers have focused on the development of stable and transparent teleoperation systems providing remote touch functionality. The major goal is to present high-quality kinesthetic feedback in a bilateral control loop closed by a human operator and a network that introduces delays and losses to the exchanged signals. On the other hand, communicating multimodal signals, such as video, audio and haptics, demands a high bitrate to facilitate remote manipulation. Very few frameworks investigating the communication issues of a multimodal teleoperation system have been developed. This thesis introduces a complete setup of a teleoperation system using commercially available robotic devices and computer hardware and proposes a novel communication protocol as an application layer multiplexing scheme for multimodal signals, which is embedded into the bilateral control loop of a teleoperation system. The multiplexing scheme applies preemptiveresume scheduling to stream audio and video data by giving high priority to haptic signals. Meanwhile, a real-time transmission rate estimator is implemented for the prediction of the transmission capacity in order to adapt the video bitrate and data throughput rate. Moreover, a detection scheme for unexpected transmission rate drops is introduced to make the system resilient to such abrupt changes in the network. Additionally, low-delay video communication is critical for a teleoperation system to achieve good-quality and fast visual feedback. Consequently, a video encoder with an accurate bitrate controller is developed to stream the compressed teleoperation scenes fitting into the target bitrate. The performance of the overall system is thoroughly evaluated using objective metrics to monitor the end-to-end delay provided by the system. According to the evaluations, the multiplexing scheme can guarantee end-to-end delays under a variety of network conditions, and the teleoperation system is resilient to unexpected changes in the available transmission rate. v This dissertation was produced as a member of the research and teaching staff at the Chair of Media Technology (LMT) at the Technical University of Munich. My research activities at LMT were supported initially by the German Academic Exchange Service (DAAD) and later by the European Research Council under the European Union's 7 th Framework Programme (FP7/2007-2013)/ERC Grant agreement no. 258941. To make this great work happen, many people have supported me morally, personally and professionally. I am genuinely grateful to al...

Abstract-Applications involving indirect interpersonal communication, such as collaborative design/assembly/exploration of physical objects, can benefit strongly from the transmission of contact-based haptic media, in addition to the more traditional audiovisual media. Inclusion of haptic media has been shown to improve immersiveness, task performance, and the overall experience of task execution. While several decades of research have been dedicated to the acquisition, processing, coding, and display of audio and video streams, similar aspects for haptic streams have been addressed only recently.Simultaneous masking is a perceptual phenomenon widely exploited in the compression of audio data. In the first part of this paper, to the best of our knowledge, we present first-time empirical evidence for masking in the perception of wideband vibrotactile signals. Our results show that this phenomenon for haptics is very similar to its auditory analog. Signals closer in frequency to a powerful masker (25 dB above detection threshold) are masked more strongly (peak threshold-shifts of up to 28 dB) than those away from the masker (threshold-shifts of 15-20 dB). The masking curves approximately follow the masker's spectral profile. In the second part of this paper, we present a bitrate scalable haptic texture codec, which incorporates the masking model and describe its subjective and objective performance evaluation. Experiments show that we can drive down the codec output bitrate to a very low value of 2.3 kbps, without the subjects being able to reliable discriminate between the codec input and distorted output texture signals.

High packet rates in telepresence and teleaction systems pose grave challenges to teleoperation over existing communication infrastructure like the Internet. To counter these issues, efficient perceptually motivated packet-rate reduction schemes have been developed. These schemes are conventionally evaluated for perceived quality via subjective user tests. Such tests are time-consuming, expensive and require precise control of experimental conditions. Computer modeling of telepresence sessions can, on the other hand, bring repeatability, ease of observation, definite control over system parameters and task description and fairness of comparison. In this paper, we present first steps towards a methodology and a framework to model and simulate a networked haptic interaction and evaluate it objectively for the quality of experience. Towards this purpose, we model the human control action and haptic perception process in teleoperation. Our results show that simulations of these models for a range of data reduction scheme parameters produce quality estimates whose trend is comparable to carefully performed subjective user tests.

Abstract. We propose a novel multiplexing scheme for teleoperation over constant bitrate (CBR) communication links. The proposed approach uniformly divides the channel into 1ms resource buckets and controls the size of the transmitted video packets as a function of the irregular haptic transmission events generated by a perceptual haptic data reduction approach. The performance of the proposed multiplexing scheme is measured objectively in terms of delay-jitter and packet rates. The results show that acceptable multiplexing delays on both the visual and haptic streams are achieved. Our evaluation shows that the proposed approach can provide a guaranteed constant delay for the time-critical force signal, while introducing acceptable video delay.