Brain-robot interaction (BRI) empowers individuals to control (semi-)automated machines through brain activity, either passively or actively. In the past decade, BRI systems have advanced significantly, primarily leveraging electroencephalogram (EEG) signals. This article presents an up-to-date review of 87 curated studies published between 2018 and 2023, identifying the research landscape of EEG-based BRI systems. The review consolidates methodologies, interaction modes, application contexts, system evaluation, existing challenges, and future directions in this domain. Based on our analysis, we propose a BRI system model comprising three entities: Brain, Robot, and Interaction, depicting their internal relationships. We especially examine interaction modes between human brains and robots, an aspect not yet fully explored. Within this model, we scrutinize and classify current research, extract insights, highlight challenges, and offer recommendations for future studies. Our findings provide a structured design space for human-robot interaction (HRI), informing the development of more efficient BRI frameworks.

Capturing informative electroencephalogram (EEG) signals is a challenging task due to the presence of noise (e.g., due to human movement). In extreme cases, data recordings from specific electrodes (channels) can become corrupted and entirely devoid of information. Motivated by recent work on deep-learning-based approaches for EEG signal denoising, we present the first benchmark study on the performance of EEG signal denoising methods in the presence of corrupted channels. We design our study considering a wide variety of datasets, models, and evaluation tasks. Our results highlight the need for assessing the performance of EEG deep-learning models across a broad suite of datasets, as provided by our benchmark.

Expressive robot motion can help establish acceptance of this technology in everyday life, but understanding what makes movement expressive is a complex and multifaceted task. This paper presents the results of an online study with 46 participants, it aims to explore how people perceive and interpret the expressive qualities of human movement and how they envision the translation of their description into an imagined non-humanoid, quadrupedal robot. Through a qualitative analysis of responses, we conceptualize three themes: their understanding of intent, their interpretations of movement qualities, and finally, their translation from human to robot movement. Respondents' descriptions of their initial understanding of the performer's intent fall into two modes, bio-mechanical and narrative. We illustrate their interpretations of movement qualities through four strategies: movement features as kinematic indicators, intent indicators, attributed context, and perceived internal states. Lastly, we observe their translation from human to robot movement, with a particular focus on respondents' use of kinaesthetic empathy and anthropomorphism. Our findings aim to support a bottom-up approach, using users' general knowledge for designing expressive robot motion.

Most wearable robots such as exoskeletons and prostheses can operate with dexterity, while wearers do not perceive them as part of their bodies. In this perspective, we contend that integrating environmental, physiological, and physical information through multi-modal fusion, incorporating human-in-the-loop control, utilizing neuromuscular interface, employing flexible electronics, and acquiring and processing human-robot information with biomechatronic chips, should all be leveraged towards building the next generation of wearable robots. These technologies could improve the embodiment of wearable robots. With optimizations in mechanical structure and clinical training, the next generation of wearable robots should better facilitate human motor and sensory reconstruction and enhancement.

Human-robot collaboration (HRC) relies on smooth and safe interactions. In this paper, we focus on the human-to-robot handover scenario, where the robot acts as a taker. We investigate the feasibility of detecting the intention of a human-to-robot handover action through the analysis of electroencephalogram (EEG) signals. Our study confirms that temporal patterns in EEG signals provide information about motor planning and can be leveraged to predict the likelihood of an individual executing a motor task with an average accuracy of 94.7%. We also suggest the effectiveness of the time-frequency features of EEG signals in the final second prior to the movement for distinguishing between handover action and other actions. Furthermore, we classify human intentions for different tasks based on time-frequency representations of pre-movement EEG signals and achieve an average accuracy of 63.5% for contrasting every two tasks against each other. The result encourages the possibility of using EEG signals to detect human handover intention in HRC tasks.

Retrieval of mental images from measured brain activity may facilitate communication, especially when verbal or muscular communication is impossible or inefficient. The existing work focuses mostly on retrieving the observed visual stimulus while our interest is on retrieving the imagined mental image. We present a closed-loop BCI framework to retrieve mental images of human faces. We utilize EEG signals as binary feedback to determine the relevance of an image to the target mental image. We employ the feedback to traverse the latent space of a generative model to propose new images closer to the actual target image. We evaluate the proposed framework on 13 volunteers. Unlike previous studies, we do not restrict the possible attributes of the resulting images to predefined semantic classes. Subjective and objective tests validate the ability of our model to retrieve face images similar to the actual target mental images.

Human-robot collaboration (HRC) relies on accurate and timely recognition of human intentions to ensure seamless interactions. Among common HRC tasks, human-to-robot object handovers have been studied extensively for planning the robot's actions during object reception, assuming the human intention for object handover. However, distinguishing handover intentions from other actions has received limited attention. Most research on handovers has focused on visually detecting motion trajectories, which often results in delays or false detections when trajectories overlap. This paper investigates whether human intentions for object handovers are reflected in non-movement-based physiological signals. We conduct a multimodal analysis comparing three data modalities: electroencephalogram (EEG), gaze, and hand-motion signals. Our study aims to distinguish between handover-intended human motions and non-handover motions in an HRC setting, evaluating each modality's performance in predicting and classifying these actions before and after human movement initiation. We develop and evaluate human intention detectors based on these modalities, comparing their accuracy and timing in identifying handover intentions. To the best of our knowledge, this is the first study to systematically develop and test intention detectors across multiple modalities within the same experimental context of human-robot handovers. Our analysis reveals that handover intention can be detected from all three modalities. Nevertheless, gaze signals are the earliest as well as the most accurate to classify the motion as intended for handover or non-handover.