When humans work together to complete a joint task, each person builds an internal model of the situation and how it will evolve. Efficient collaboration depends on how these individual models overlap to form a shared mental model among team members; shared models are also important for collaborative processes in human–robot teams. The development and maintenance of an accurate shared mental model requires bidirectional communication of individual intent and the ability to interpret the intent of other team members. To enable effective human–robot collaboration, this article investigates the use of augmented reality (AR) technology and user eye gaze to enable bidirectional communication of intent in a joint action task. We tested this approach through a user study with 37 participants and found that this communication improves task efficiency, trust, as well as task fluency. We conclude that using AR and eye gaze to enable bidirectional communication and support shared mental models is a promising means for improving collaboration between humans and robots.

Navigating effectively and safely in unknown urban environments is a crucial ability for service robot applications such as last-mile package delivery. To reach the entrance of its target destination, the robot must make informed local and global path planning decisions. We present a mapless global planning strategy based on pedestrian following. Our method allows the robot to exploit natural routes taken by surrounding pedestrians to make informed and efficient path planning decisions for reaching its goal. The algorithm also includes a recovery system to assist the robot when insufficient progress is made (i.e. robot stuck in dead end). Once the robot is within the vicinity of the target building, a wall following behaviour is used to reach the entrance of the target building. Simulated experiments and a proof-of-concept demonstration on a real robot were shown to validate the approach.

Existing approaches to direct robot-to-human handovers are typically implemented on fixed-base robot arms, or on mobile manipulators that come to a full stop before performing the handover. We propose "on-the-go" handovers which permit a moving mobile manipulator to hand over an object to a human without stopping. The on-the-go handover motion is generated with a reactive controller that allows simultaneous control of the base and the arm. In a user study, human receivers subjectively assessed on-the-go handovers to be more efficient, predictable, natural, better timed and safer than handovers that implemented a "stop-and-deliver" behavior.

Safety is a basic requirement in any human-robot collaboration scenario. To ensure user safety, from both physical and psychological aspects, we propose a novel Virtual Barrier system facilitated by an augmented reality interface1. Our system provides two types of Virtual Barriers to ensure safety: 1) a Virtual Person Barrier which encapsulates and follows the user to protect them from collisions with the robot, and 2) Virtual Obstacle Barriers which users can spawn to protect objects or regions that the robot should not enter. Our system utilizes augmented reality to visually display these protective barriers to the user during operation. To enable effective human-robot collaboration, our system automatically replans the robot’s motion when potential collisions are detected as a result of a barrier intersecting the robot’s planned path. Comparing our novel system with a standard 2D display interface in a user study with a mock industrial manufacturing task showed that our system increases both physical and psychological safety, task efficiency and interaction intuitiveness.

Humans are highly skilled in communicating their intent for when and where a handover would occur. However, even the state-of-the-art robotic implementations for handovers typically lack of such communication skills. This study investigates visualization of the robot’s internal state and intent for Human-to-Robot Handovers using Augmented Reality. Specifically, we explore the use of visualized 3D models of the object and the robotic gripper to communicate the robot’s estimation of where the object is and the pose in which the robot intends to grasp the object. We tested this design via a user study with 16 participants, in which each participant handed over a cube-shaped object to the robot 12 times. Results show communicating robot intent via augmented reality substantially improves the perceived experience of the users for handovers. Results also indicate that the effectiveness of augmented reality is even more pronounced for the perceived safety and fluency of the interaction when the robot makes errors in localizing the object.

The use of hand-based gestures has been proposed as an intuitive way for people to communicate with robots. Typically the set of gestures is defined by the experimenter. However, existing works do not necessarily focus on gestures that are communicative, and it is unclear whether the selected gesture are actually intuitive to users. This paper investigates whether different people inherently use similar gestures to convey the same commands to robots, and how teaching of gestures when collecting demonstrations for training recognizers can improve resulting accuracy. We conducted this work in two stages. In Stage 1, we conducted an online user study (n=190) to investigate if people use similar gestures to communicate the same set of given commands to a robot when no guidance or training was given. Results revealed large variations in the gestures used among individuals With the absences of training. Training a gesture recognizer using this dataset resulted in an accuracy of around 20%. In response to this, Stage 2 involved proposing a common set of gestures for the commands. We taught these gestures through demonstrations and collected ~ 7500 videos of gestures from study participants to train another gesture recognition model. Initial results showed improved accuracy but a number of gestures had high confusion rates. Refining our gesture set and recognition model by removing those gestures, We achieved an final accuracy of 84.1 ± 2.4%. We integrated the gesture recognition model into the ROS framework and demonstrated a use case, where a person commands a robot to perform a pick and place task using the gesture set.

We provide an experimental evaluation of a wearable augmented reality (AR) system we have developed for human-robot teams working on tasks requiring collaboration in shared physical workspace. Recent advances in AR technology have facilitated the development of more intuitive user interfaces for many human-robot interaction applications. While it has been anticipated that AR can provide a more intuitive interface to robot assistants helping human workers in various manufacturing scenarios, existing studies in robotics have been largely limited to teleoperation and programming. Industry 5.0 envisions cooperation between human and robot working in teams. Indeed, there exist many industrial tasks that can benefit from human-robot collaboration. A prime example is high-value composite manufacturing. Working with our industry partner towards this example application, we evaluated our AR interface design for shared physical workspace collaboration in human-robot teams. We conducted a multi-dimensional analysis of our interface using established metrics. Results from our user study (n = 26) show that, subjectively, the AR interface feels more novel and a standard joystick interface feels more dependable to users. However, the AR interface was found to reduce physical demand and task completion time, while increasing robot utilization. Furthermore, user’s freedom of choice to collaborate with the robot may also affect the perceived usability of the system.

We present an approach for visualizing mobile robots through an Augmented Reality headset when there is no line-of-sight visibility between the robot and the human. Three elements are visualized in Augmented Reality: 1) Robot’s 3D model to indicate its position, 2) An arrow emanating from the robot to indicate its planned movement direction, and 3) A 2D grid to represent the ground plane. We conduct a user study with 18 participants, in which each participant are asked to retrieve objects, one at a time, from stations at the two sides of a T-junction at the end of a hallway where a mobile robot is roaming. The results show that visualizations improved the perceived safety and efficiency of the task and led to participants being more comfortable with the robot within their personal spaces. Furthermore, visualizing the motion intent in addition to the robot model was found to be more effective than visualizing the robot model alone. The proposed system can improve the safety of automated warehouses by increasing the visibility and predictability of robots.

An appropriate user interface to collect human demonstration data for deformable object manipulation has been mostly overlooked in the literature. We present an inter-action design for demonstrating cloth folding to robots. Users choose pick and place points on the cloth and can preview a visualization of a simulated cloth before real-robot execution. Two interfaces are proposed: A 2D display-and-mouse interface where points are placed by clicking on an image of the cloth, and a 3D Augmented Reality interface where the chosen points are placed by hand gestures. We conduct a user study with 18 participants, in which each user completed two sequential folds to achieve a cloth goal shape. Results show that while both interfaces were acceptable, the 3D interface was more suitable for understanding the task, and the 2D interface was suitable for repetition. Results also found that fold previews improve three key metrics: task efficiency, the ability to predict the final shape of the cloth, and overall user satisfaction.

This article surveys the literature on human–robot object handovers. A handover is a collaborative joint action, where an agent, the giver, gives an object to another agent, the receiver. The physical exchange starts when the receiver first contacts the object held by the giver and ends when the giver fully releases the object to the receiver. However, important cognitive and physical processes begin before the physical exchange, including initiating implicit agreement with respect to the location and timing of the exchange. From this perspective, we structure our review into the two main phases delimited by the aforementioned events: a prehandover phase and the physical exchange. We focus our analysis on the two actors (giver and receiver) and report the state of the art of robotic givers (robot-to-human handovers) and the robotic receivers (human-to-robot handovers). We report a comprehensive list of qualitative and quantitative metrics commonly used to assess the interaction. While focusing our review on the cognitive level (e.g., prediction, perception, motion planning, and learning) and the physical level (e.g., motion, grasping, and grip release) of the handover, we also discuss safety. We compare the behaviors displayed during human-to-human handovers to the state of the art of robotic assistants and identify the major areas of improvement for robotic assistants to reach performance comparable to human interactions. Finally, we propose a minimal set of metrics that should be used in order to enable a fair comparison among the approaches.

The increasing presence of robots alongside humans, such as in human-robot teams in manufacturing, gives rise to research questions about the kind of behaviors people prefer in their robot counterparts. We term actions that support interaction by reducing future interference with others as supportive robot actions and investigate their utility in a co-located manipulation scenario. We compare two robot modes in a shared table pick-and-place task: (1) Task-oriented: the robot only takes actions to further its task objective and (2) Supportive: the robot sometimes prefers supportive actions to task-oriented ones when they reduce future goal-conflicts. Our experiments in simulation, using a simplified human model, reveal that supportive actions reduce the interference between agents, especially in more difficult tasks, but also cause the robot to take longer to complete the task. We implemented these modes on a physical robot in a user study where a human and a robot perform object placement on a shared table. Our results show that a supportive robot was perceived more favorably as a coworker and also reduced interference with the human in one of two scenarios. However, it also took longer to complete the task highlighting an interesting trade-off between task-efficiency and human-preference that needs to be considered before designing robot behavior for close-proximity manipulation scenarios.

This paper investigate potential use of augmented reality (AR) for physical human-robot collaboration in large-scale, labour-intensive manufacturing tasks. While it has been shown that use of AR can help increase task efficiency in teleoperative and robot programming tasks involving smaller-scale robots, its use for physical human-robot collaboration in shared workspaces and large-scale manufacturing tasks have not been well-studied. With the eventual goal of applying our AR system to collaborative aircraft body manufacturing, we compare in a user study the use of an AR interface we developed with a standard joystick for human robot collaboration in an experiment task simulating industrial carbon-fibre-reinforced-polymer manufacturing procedure. Results show that use of AR yields reduced task time and physical demand, with increased robot utilization.

Programming and executing robot trajectories is a routine manufacturing procedure. However, current interfaces (i.e., teach pendants) are bulky, unintuitive, and interrupts task flow. Recently, augmented reality (AR) has been used to create alternative solutions. However, input modalities of such systems tend to be limited. By introducing the use of electromyography (EMG), we have created a novel multimodal wearable interface for online trajectory programming and execution. Through the use of EMG, our system aims to bridge the user's force activation to the robot arm force profile. Our proposed system provides two interaction methods for trajectory execution and force control using 1) arm EMG and 2) arm orientation. We compared these methods with a standard joystick in a user study to test their usability. Results show that proposed methods have increased physical demands but yield equivalent task performance, demonstrating the potential of our proposed interface to provide a wearable alternative solution.

In this paper, we propose a novel navigation system for mobile robots in pedestrian-rich sidewalk environments. Sidewalks are unique in that the pedestrian-shared space has characteristics of both roads and indoor spaces. Like vehicles on roads, pedestrian movement often manifests as linear flows in opposing directions. On the other hand, pedestrians also form crowds and can exhibit much more random movements than vehicles. Classical algorithms are insufficient for safe navigation around pedestrians and remaining on the sidewalk space. Thus, our approach takes advantage of natural human motion to allow a robot to adapt to sidewalk navigation in a safe and socially-compliant manner. We developed a group surfing method which aims to imitate the optimal pedestrian group for bringing the robot closer to its goal. For pedestrian-sparse environments, we propose a sidewalk edge detection and following method. Underlying these two navigation methods, the collision avoidance scheme is human-aware. The integrated navigation stack is evaluated and demonstrated in simulation. A hardware demonstration is also presented.

This paper presents a future-focused approach for robot programming based on augmented trajectories. Using a mixed reality head-mounted display (Microsoft Hololens) and a 7-DOF robot arm, we designed an augmented reality (AR) robotic interface with four interactive functions to ease the robot programming task: 1) Trajectory specification. 2) Virtual previews of robot motion. 3) Visualization of robot parameters. 4) Online reprogramming during simulation and execution. We validate our AR-robot teaching interface by comparing it with a kinesthetic teaching interface in two different scenarios as part of a pilot study: creation of contact surface path and free space path. Furthermore, we present an industrial case study that illustrates our AR manufacturing paradigm by interacting with a 7-DOF robot arm to reduce wrinkles during the pleating step of the carbon-fiber-reinforcement-polymer vacuum bagging process in a simulated scenario.

To enable robots to learn handover orientations from observing natural handovers, we conduct a user study to measure and compare natural handover orientations with giver-centered and receiver-centered handover orientations for twenty common objects. We use a distance minimization approach to compute mean handover orientations. We posit that, computed means of receiver-centered orientations could be used by robot givers to achieve more efficient and socially acceptable handovers. Furthermore, we introduce the notion of affordance axes for comparing handover orientations, and offer a definition for computing them. Observable patterns were found in receiver-centered handover orientations. Comparisons show that depending on the object, natural handover orientations may not be receiver-centered; thus, robots may need to distinguish between good and bad handover orientations when learning from natural handovers.

Object handover is a basic task in many human-robot interactive scenarios and therefore, it is important for assistive robots to be able to perform proper handovers. We previously designed a human-inspired grip-force-varying handover controller for a robot giver and showed on a Willow Garage PR2 robot that the controller yields human-like and human-preferred handovers. The PR2 robot had a non-compliant fully-actuated gripper. However, recently, compliant underactuated grippers have been gaining more popularity. Although compliant underactuated grippers can provide more flexibility in manipulation, it is generally difficult to accurately measure and control the amount of applied grip force. In this paper, we present an implementation of the human-inspired handover controller on a Kawada Industries HRP4R robot, which has compliant underactuated hands, using joint position error measurement for estimating the amount of applied grip force. Through an experiment, we show that we are able to achieve safe, smooth, and intuitive robot-human handovers despite the lack of accurate grip force control on our robot.

We present a method for enabling robots to determine appropriate grasp configurations for handovers - i.e., where to grasp, and how to orient an object when handing it over. In our method, a robot first builds a knowledge base by observing demonstrations of how certain objects are used and their proper handover grasp configurations. Objects in the knowledge base are then organized based on their movements and inter-object interaction features. The key point in this process is that similarity in affordances should be recognized. When subsequently asked to handover an object, the robot then computes an appropriate grasp configuration based on the object's recognized affordances. Experimental results show that our method was able to differentiate and group together objects according to their affordances. Furthermore, when given a new object, our method was able to generalize data in the knowledge base and determine an appropriate grasp configuration.

In this study, we investigate and characterize haptic interaction in human-to-human handovers and identify key features that facilitate safe and efficient object transfer. Eighteen participants worked in pairs and transferred weighted objects to each other while we measured their grip forces and load forces. Our data show that during object transfer, both the giver and receiver employ a similar strategy for controlling their grip forces in response to changes in load forces. In addition, an implicit social contract appears to exist in which the giver is responsible for ensuring object safety in the handover and the receiver is responsible for maintaining the efficiency of the handover. Compared with prior studies, our analysis of experimental data show that there are important differences between the strategies used by humans for both picking up/placing objects on table and that used for handing over objects, indicating the need for specific robot handover strategies as well. The results of this study will be used to develop a controller for enabling robots to perform object handovers with humans safely, efficiently, and intuitively.