This article proposes a collision detection algorithm without external sensors that can detect potential collisions in man–robot interaction. The algorithm is based on a modified first-order momentum ...deviation observer that also takes friction into account. The collision detection algorithm uses joint angles, angular velocities, and torques during the detection process, without any need to consider angular acceleration. The algorithm also uses an accurate friction model that is based on a Stribeck model with second-order Fourier series compensation. The friction model is applied in advance so that compensation can be made in real time during collision detection. Identification data are filtered through a first-order low-pass filter to reduce high-frequency noise. In order to verify the algorithm, a simulation and experiment were carried out using a collaborative robot experimental platform. The results confirmed that collisions can be detected by setting appropriate threshold values. Different possible responses can be implemented according to different response strategies, with the ultimate arbiter being that collision forces are kept strictly within ordinary human tolerances. This makes sure that safety can be preserved in man–robot interaction processes.
Aiming at the problem of collision detection and collision point information evaluation in the process of human-robot collaboration, the binocular camera is used as an external sensor to observe. ...Collision detection is realized by tracking the motion of human-robot through the color information of joints. Firstly, the Camshift algorithm is used to track the position of the manipulator joints and the human arm joints based on the color information. In order to solve the factors that may cause target loss during tracking process, such as shelter and background color similar problems, Kalman filter is integrated on the basis of Camshift algorithm. A similarity threshold is set to judge whether there is interference in the tracking process. The tracking experiment proved that the Kalman filter is effective and enhances the robustness of the tracking algorithm. Secondly, a bounding box collision detection method based on space domain is designed. The sphere bounding box and the cylindrical bounding box is used as the human-robot bounding boxes. The equations of the distance between different boxes are derived and the position of the collision point on the manipulator is calculated. Finally, an experimental environment is built for verification. The distance error of the collision is within 0–10 mm, and the position error between the calculated collision point and the pre-determined collision point is within 10%.
In modern industrial plants, collisions between humans and robots pose a significant risk to occupational safety. To address this concern, we sought to devise a reliable system for human-robot ...collision avoidance system employing computer vision. This system enables the proactive prevention of dangerous collisions between humans and robots. In contrast to previous approaches, we used a standard RGB camera, making implementation more convenient and cost-effective. Furthermore, the proposed method greatly extends the effective detection range compared to previous studies, thereby enhancing its utility for monitoring large-scale workplaces.
Background: Human-robot collaboration is becoming increasingly prevalent in the manufacturing industry, but the risk of collisions between human workers and collaborative robots poses safety concerns.
Purpose: We aimed to address these safety concerns and enhance occupational safety by developing a camera-based motion tracking method combined with a collision-avoidance scheme.
Methods: The approach involves a single RGB camera and computer-vision algorithms to track the position of a human worker relative to a collaborative robot. A comprehensive collision-avoidance scheme is then employed, using the worker's position and motion data for robot action planning and execution. The collision avoidance actions include generating visual and auditory alarm signals and retracting robot arms.
Results: Our preliminary validation demonstrated that the proposed collision avoidance scheme effectively enables a collaborative robot to respond to a human worker approaching from different directions.
Conclusion: The proof-of-concept human-robot collision avoidance scheme presented in this study significantly reduces the risk of collisions and holds potential for improving workplace safety in future human-robot collaboration applications.
Joint attention is a key mechanism for humans to coordinate their social behavior. Whether and how this mechanism can benefit the interaction with pseudo-social partners such as robots is not well ...understood. To investigate the potential use of robot eyes as pseudo-social cues that ease attentional shifts we conducted an online study using a modified spatial cueing paradigm. The cue was either a non-social (arrow), a pseudo-social (two versions of an abstract robot eye), or a social stimulus (photographed human eyes) that was presented either paired (e.g. two eyes) or single (e.g. one eye). The latter was varied to separate two assumed triggers of joint attention: the social nature of the stimulus, and the additional spatial information that is conveyed only by paired stimuli. Results support the assumption that pseudo-social stimuli, in our case abstract robot eyes, have the potential to facilitate human-robot interaction as they trigger reflexive cueing. To our surprise, actual social cues did not evoke reflexive shifts in attention. We suspect that the robot eyes elicited the desired effects because they were human-like enough while at the same time being much easier to perceive than human eyes, due to a design with strong contrasts and clean lines. Moreover, results indicate that for reflexive cueing it does not seem to make a difference if the stimulus is presented single or paired. This might be a first indicator that joint attention depends rather on the stimulus' social nature or familiarity than its spatial expressiveness. Overall, the study suggests that using paired abstract robot eyes might be a good design practice for fostering a positive perception of a robot and to facilitate joint attention as a precursor for coordinated behavior.
Humans use collaborative robots as tools for accomplishing various tasks. The interaction between humans and robots happens in tight shared workspaces. However, these machines must be safe to operate ...alongside humans to minimize the risk of accidental collisions. Ensuring safety imposes many constraints, such as reduced torque and velocity limits during operation, thus increasing the time to accomplish many tasks. However, for applications such as using collaborative robots as haptic interfaces with intermittent contacts for virtual reality applications, speed limitations result in poor user experiences. This research aims to improve the efficiency of a collaborative robot while improving the safety of the human user. We used Gaussian process models to predict human hand motion and developed strategies for human intention detection based on hand motion and gaze to improve the time for the robot and human security in a virtual environment. We then studied the effect of prediction. Results from comparisons show that the prediction models improved the robot time by 3% and safety by 17%. When used alongside gaze, prediction with Gaussian process models resulted in an improvement of the robot time by 2% and the safety by 13%.
In this paper, we propose a novel system in which a human and a device work in unison on a single task with the aim to simultaneously support human cognitive and physical functions. In this system, ...the cognitive and physical burdens of the task are shared between the human and device, with the human understanding the entire task and performing rough upstream actions. Additionally, the device understands the surrounding environment, objects, and the human and executes detailed downstream actions. A prototype device was developed to assist in solving silhouette puzzles that abstract and generalize cognitive and physical tasks. The prototype is a pen-shaped device held in the user's hand. The device picks up puzzle pieces and rotates them to the appropriate position. A display is placed in front of the user and provides feedback information for communication between the system and user. Experiments showed that the proposed device reduced the time required to solve these puzzles. Furthermore, the work was found to be accurate with no errors, and the time required was stable with no irregularities. The subjective evaluation results using the NASA Task Load Index showed that the proposed system can decrease mental load and burden. Moreover, it was confirmed that the human and device must communicate with each other to work simultaneously on one task. In conclusion, the proposed device can support human cognitive and physical functions simultaneously.
Collaborative robots are used in scenarios requiring interaction with humans. In order to improve the safety and adaptability of collaborative robots during human–robot interaction, this paper ...proposes a modular wire-actuated robotic arm with symmetric variable-stiffness units. The variable-stiffness unit is employed to extend the stiffness-adjustment range of the robotic arm. The variable-stiffness unit is designed based on flexure, featuring a compact and simple structure. The stiffness–force relationship of the variable-stiffness unit can be fitted by a quadratic function with an R-squared value of 0.99981, indicating weak nonlinearity. Based on the kinematics and stiffness analysis of the symmetric joint module of the robotic arm, the orientation of the joint module can be adjusted by regulating the length of the wires and the stiffness of the joint module can be adjusted by regulating the tension of the wires. Because of the actuation redundancy, the orientation and stiffness of the joint module can be adjusted synchronously. Furthermore, a direct method is proposed for the stiffness-oriented wire-tension-distribution problem of the 1-DOF joint module. A simulation is carried out to verify the proposed method. The simulation result shows that the deviation between the calculated stiffness and the desired stiffness was less than 0.005%.
Aiming at the characteristics of high efficiency and smoothness in the motion process of collaborative robot, a multi-objective trajectory planning method is proposed. Firstly, the kinematics model ...of the collaborative robot is established, and the trajectory in the workspace is converted into joint space trajectory using inverse kinematics method. Secondly, seven-order B-spline functions are used to construct joint trajectory sequences to ensure the continuous position, velocity, acceleration and jerk of each joint. Then, the trajectory competitive multi-objective particle swarm optimization (TCMOPSO) algorithm is proposed to search the Pareto optimal solutions set of the robot’s time-energy-jerk optimal trajectory. Further, the normalized weight function is proposed to select the appropriate solution. Finally, the algorithm simulation experiment is completed in MATLAB, and the robot control experiment is completed using the Robot Operating System (ROS). The experimental results show that the method can achieve effective multi-objective optimization, the appropriate optimal trajectory can be obtained according to the actual requirements, and the collaborative robot is actually operating well.
This paper presents a new bi-objective safety-oriented path planning strategy for robotic manipulators. Integrated into a sampling-based algorithm, our approach can successfully enhance the task ...safety by guiding the expansion of the path towards the safest configurations. Our safety notion consists of avoiding dangerous situations, e.g. being very close to the obstacles, human awareness, e.g. being as much as possible in the human vision field, as well as ensuring human safety by being as far as possible from human with hierarchical priority between human body parts. Experimental validations are conducted in simulation and on the real Baxter research robot. They revealed the efficiency of the proposed method, mainly in the case of a collaborative robot sharing the workspace with humans.
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