Human-friendly Robot Research Articles

Amplification of photothermally induced reversible actuation in non-woven fabrics compared to bulk films

The burgeoning field of soft robotics has witnessed a surge in interest, driven by the pursuit of creating precise machines with soft actuators capable of surpassing or aiding human manufacturing capabilities. This work explores light-responsive shape memory actuators derived from electrospun fibers, integrating a "push-pull" azo compound into a poly(ε-caprolactone) matrix. Driven by photothermal conversion, the resulting system exhibits reversible actuation under UV light, demonstrating rapid responses and superior performance compared to film counterparts. More specifically, the significant impact of morphology on both the photothermal behavior and the actuation performance is highlighted by comparing non-woven and bulk shape memory material. The temperature variation induced by UV light in the non-woven was notably affected by scattering effects, leading to the formation of temperature gradients throughout the material. Notably, the study establishes a unique stress-responsive range for fibrous actuators, demonstrating that their porous structure contributes to higher actuation magnitudes at lower stresses compared to conventional films. This innovation holds promise for applications in micro-robotics and biomedical fields, showcasing the potential of fibrous actuators in augmenting human-friendly robotics through their lightweight, flexible, and remotely actuated features.

Two-link Manipulator Driven by a Pair of Antagonistic Rubber Artificial Muscle

Pneumatic rubber artificial muscles have been extensively researched as a driving device capable of soft movements that are compatible with humans, and are expected to be applied to human friendly robots. However, it is difficult in principle to achieve high-precision positioning and high-rigidity position retention due to low stiffness and delayed response as a result of air compressibility. Normally, a 2-link manipulator requires 4 (2 pairs) artificial muscles, but here, by attaching two MR brakes to each axis and switching the drive shaft, a manipulator that controls a 2-link manipulator with 2 (1 pair) artificial muscles, is proposed.

Estimation of Confidence in the Dialogue based on Eye Gaze and Head Movement Information

In human-robot interaction, human mental states in dialogue have attracted attention to human-friendly robots that support educational use. Although estimating mental states using speech and visual information has been conducted, it is still challenging to estimate mental states more precisely in the educational scene. In this paper, we proposed a method to estimate human mental state based on participants’ eye gaze and head movement information. Estimated participants’ confidence levels in their answers to the miscellaneous knowledge question as a human mental state. The participants’ non-verbal information, such as eye gaze and head movements during dialog with a robot, were collected in our experiment using an eye-tracking device. Then we collect participants’ confidence levels and analyze the relationship between human mental state and non-verbal information. Furthermore, we also applied a machine learning technique to estimate participants’ confidence levels from extracted features of gaze and head movement information. As a result, the performance of a machine learning technique using gaze and head movements information achieved over 80 % accuracy in estimating confidence levels. Our research provides insight into developing a human-friendly robot considering human mental states in the dialogue.

A Task-Based Post-Impact Safety Protocol Based on Energy Tanks

As situations with robots working in human environments are becoming increasingly important, the aspect of safety is crucial. As a consequence, the design of human friendly robots has been intensively researched in the past years, producing both mechanical and control design advancements. In this work, a safety-aware control architecture is proposed in a scenario in which a predefined task has to be executed. At the core of its implementation, a novel dynamic energy injection protocol is introduced for energy tanks. Contrarily to their most common employment in the past, energy tanks are used to provide relevant information on energy flows used by the safety protocol, rather than to guarantee passivity of the controlled robot, which does not imply safety. The algorithm is able to detect collisions and divergence from nominal task execution by identifying unwanted energy flows, encoded in the energy tanks. A reaction strategy based on low impedance control is implemented in case of collision detection. Experiments on a 7-DoF manipulator successfully validate the proposed strategy.

Design of a Novel Sensing Method for a Pneumatic Artificial Muscle Actuator-Driven 2-Degrees of Freedom Parallel Joint.

The development of soft actuators and robots has spurred interest in human-friendly robots and devices that can operate in proximity with living things. Researchers have used soft actuators to drive hybrid soft/rigid mechanical platforms with multiple degrees of freedom (DOFs) that are both compliant and produce precise motions. However, the addition of sensors on these systems for feedback control remains a critical issue as they require multiple sensors operating simultaneously while the system undergoes complex motions. This article introduces the use of two spring-tensioned tendons passing through angular encoders for yaw and pitch orientation measurement into a pneumatic artificial muscle-driven two DOFs platform. This system possesses several advantages such as having a large range of motion and enables feedback control of the joint for position control. The joint is shown to be able to follow diverse motion patterns and capable of operating through external disturbances and was implemented as the base joint of an inflatable member.

車輪移動型ロボットのための速度ベースメカニカル安全ブレーキ組込み機構の開発

Recently, many human-friendly robots have been developed. Since human-friendly robots work in the same space as humans, it is necessary to ensure a high level of safety. We developed a velocity-based mechanical safety brake for human-friendly robots. If this safety brake detects an unexpected driveshaft’s angular velocity, it switches off all of the robot’s motors and then stops the driveshaft by gradually reducing the velocity of the driveshaft. However, to use this brake, the robot needed to be equipped with twice as many safety brakes as the robot’s driveshafts. Therefore, we have developed a mechanism to detect an unexpected driveshaft’s angular velocity, switch off all of the robot’s motors, and then stop all of the driveshafts by using only one velocity-based mechanical safety brake. This paper describes the development of the mechanism. We present experimental results to check whether the mechanism achieved the necessary function or not.

Collision force suppression system for human‐friendly robot

AbstractA collision force suppression system for a human friendly robot, which consists of two arms, a trunk, a waist, an omnidirectional mobile base, is proposed. In this paper, the proposed passive collision force suppression system is realized by the collision force suppression mechanisms and the reaction system. When the collision occurs between the robot and an object, the joints of the arm and the waist are disconnected by the collision force suppression mechanism depending on the magnitude of collision forces. The reaction system is based on the strength and existence time of the collision force, and the joints are disconnected by the order of arm and waist, and the finally the mobile base will move if the reactions are not enough to decrease the passive force. The effectiveness of the proposed system is proven by experiments.

Human-friendly control system design for two-wheeled service robot with optimal control approach

This paper proposes a novel control system design for a two-wheeled service robot that follows a person as an assistant without knowing the person’s destination. For this kind of service robot, the key skill is to realize human-friendly movement. However, appropriate motion always changed depending on the situation. For instance, when the robot is close and person turns toward it, it is important to suppress the robot’s acceleration. Likewise, if the person turns away from the robot, the robot should maintain its position within an appropriate area. Therefore, to deal with various required movements, our control system is able to change its properties automatically and suitably depending on the situation by using weights of the cost function in nonlinear model predictive control (NMPC) as a function of the relative distance between the person and the robot. Unlike previous methods, our design includes only one controller. Consequently, we are able to take into account system stability. Moreover, owing to proposing in NMPC framework, it is easy to extend our method by adopting other recognition or goal-setting methods. We conducted simulations using actual human walking data taken by the robot’s laser range sensors. The experiments demonstrate that the robot can follow a person who performs U-turn, confirming that our method can produce human-friendly robot movement in a practical scene.

3D Shrinking for Rapid Fabrication of Origami-Inspired Semi-Soft Pneumatic Actuators

Soft actuators are an essential component of soft robots. They are also well suited for human-friendly robots due to their intrinsic safety. The advantages of origami structures have motivated the development of origami-inspired semi-soft actuators. In this paper, a novel rapid, systematic and cost-effective fabrication method for durable origami-inspired semi-soft pneumatic actuators is presented. The proposed method employs heat-shrinkable polymers conforming to reusable molds. It is applicable to a variety of origami patterns, and it produces actuators with consistent performance. Two origami semi-soft pneumatic actuator designs (accordion and Yoshimura patterns) have been fabricated. Each actuator was fabricated in less than 10 minutes (not including the time required to create the molds and plastic components). A nonlinear finite-element model is developed to predict the actuator's folding behavior and blocked force. The results show that it can predict the blocked force with a maximum error of 5.7% relative to experimental measurements. This model can be used to improve the design of future actuators. Experimental results for isometric, isobaric, isotonic and cyclic fatigue tests for the accordion pattern actuator are included and discussed. The actuator prototype has a maximum stroke of 40 mm (or 36% of its effective length) and a maximum blocked force of 124 N at a vacuum pressure of -80 kPa. It also showed no decrease in performance and no leakage after 1000 cycles with a payload of 0.9 kg, demonstrating its durability compared to previous origami-inspired semi-soft pneumatic actuators. Finally, it has a high force-to-weight ratio as it can lift a load more than 118 times its own weight. Its performance demonstrates that powerful, lightweight and durable actuators can be easily produced by the proposed fabrication method.

A bimodal soft electronic skin for tactile and touchless interaction in real time

The emergence of smart electronics, human friendly robotics and supplemented or virtual reality demands electronic skins with both tactile and touchless perceptions for the manipulation of real and virtual objects. Here, we realize bifunctional electronic skins equipped with a compliant magnetic microelectromechanical system able to transduce both tactile—via mechanical pressure—and touchless—via magnetic fields—stimulations simultaneously. The magnetic microelectromechanical system separates electric signals from tactile and touchless interactions into two different regions, allowing the electronic skins to unambiguously distinguish the two modes in real time. Besides, its inherent magnetic specificity overcomes the interference from non-relevant objects and enables signal-programmable interactions. Ultimately, the magnetic microelectromechanical system enables complex interplay with physical objects enhanced with virtual content data in augmented reality, robotics, and medical applications.

A Self-Deformation Robot Design Incorporating Bending-Type Pneumatic Artificial Muscles

With robots becoming closer to humans in recent years, human-friendly robots made of soft materials provide a new line of research interests. We designed and developed a soft robot that can move via self-deformation toward the practical application of monitoring children and the elderly on a daily basis. The robot’s structure was built out of flexible frames, which are bending-type pneumatic artificial muscles (BPAMs). We first provide a description and discussion on the nature of BPAM, followed by static characteristics experiment. Although the BPAM theoretical model shares a similar tendency with the experimental results, the actual BPAMs moved along the depth direction. We then proposed and demonstrated an effective locomotion method for the robot and calculated its locomotion speed by measuring its drive time and movement distance. Our results confirmed the reasonability of the robot’s speed for monitoring children and the elderly. Nevertheless, during the demonstration, some BPAMs were bent sharply by other activated BPAMs as the robot was driving, leaving a little damage on these BPAMs. This will be addressed in our future work.

Investigation of Transient Response on Starting Up of Differential Planetary Gear Train with High-Speed Monitoring

Planetary gear trains (PGTs) are widely used in various kinds of machines owing to its advantages, such as high gear ratio, compactness, light weight, and high-load capacity. Needs for PGT especially as a differential device are getting bigger and bigger such as in the human friendly robot and assisting suite. Although there are many studies about PGTs, experimental studies are few, and also almost all studies are dealing steady conditions in ordinary simple usage for reduction. Therefore in this study, transient conditions in starting up are dealt, and the motion of planet gear, which is hidden in ordinary PGT, is directly observed by high-speed camera on novel PGT named U/2K-HV equipping clear acrylic carrier.

Development of Human-Friendly Robot with Passive Collision Force Suppression Mechanism

Development of Human-Friendly Robot with Passive Collision Force Suppression Mechanism

Design of a compact mechanical safety device for human-friendly robots

Design of a compact mechanical safety device for human-friendly robots

Collaborative Assembly in Hybrid Manufacturing Cells: An Integrated Framework for Human–Robot Interaction

Recent emergence of safe, lightweight, and flexible robots has opened a new realm for human–robot collaboration in manufacturing. Utilizing such robots with the new human–robot interaction (HRI) functionality to interact closely and effectively with a human co-worker, we propose a novel framework for integrating HRI factors (both physical and social interactions) into the robot motion controller for human–robot collaborative assembly tasks in a manufacturing hybrid cell. To meet human physical demands in such assembly tasks, an optimal control problem is formulated for physical HRI (pHRI)-based robot motion control to keep pace with human motion progress. We further augment social HRI (sHRI) into the framework by considering a computational model of the human worker’s trust in his/her robot partner as well as robot facial expressions. The human worker’s trust in robot is computed and used as a metric for path selection as well as a constraint in the optimal control problem. Robot facial expression is displayed for providing additional visual feedbacks to the human worker. We evaluate the proposed framework by designing a robotic experimental testbed and conducting a comprehensive study with a human-in-the-loop. Results of this paper show that compared to the manual adjustments of robot velocity, an autonomous controller based on pHRI, pHRI and sHRI with trust, or pHRI and sHRI with trust, and emotion result in 34%, 39%, and 44% decrease in human workload and 21%, 32%, and 60% increase in robot’s usability, respectively. Compared to the manual framework, human trust in robot increases by 38% and 42%, respectively, in the latter two autonomous frameworks. Moreover, the overall efficiency in terms of assembly time remains the same. Note to Practitioners —Conventionally, industrial robots are used to perform repetitive tasks in human-free cages with minimal HRI for safety concerns. Thanks to the new safety and flexibility functions embedded in human-friendly manufacturing robots, humans and robots can now collaborate closely with each other accomplishing the tasks that were previously done by human workers solely. However, existing criteria for designing robot controllers need to be modified by considering the human workers’ demands since the performance of a human worker would vary due to factors such as individual strength, working pattern, and interaction with the robot. To address this problem, we propose a novel framework that integrates HRI factors in controlling the motion of a robot for the collaborative assembly tasks. Within this framework, the speed of robot can be controlled such that its motion progress synchronizes with that of the human during the task to improve pHRI. Moreover, for better sHRI, human trust in robot is calculated and used to select robot path and modify its speed control. Furthermore, we dynamically change the robot facial expression to provide visual feedbacks for performance and safety concerns. The results of the experimental study show that integrating both pHRI and sHRI in the robot controller leads to a significant drop of human perceived workload and considerable increase of robot usability and human trust in robot while the overall efficiency in terms of assembly time remains intact. For practical utilization in assembly plants, sensory devices for tracking the human motion are required. The robot is also required to have built-in safety functions that reduce the impact of possible collisions between the human and the robot. We believe that this paper addresses how the implementation of human-friendly robots in the manufacturing environments can improve HRI and reduce workload.

Development of a Safety- and Energy-Aware Impedance Controller for Collaborative Robots

In contexts where robots share their workspace with humans, safety is of utmost importance. Consequently, in recent years, a big impulse has been given to the design of human-friendly robots by involving both mechanical and control design aspects. Regarding controller design, this often involves introducing compliance and ensuring asymptotic stability using an interaction control scheme and passivity theory. Moreover, when human operators physically interact with the robot during work, strict safety measures become necessary with some of these including power and force limitations [1]. In this letter, a novel impedance control technique for collaborative robots is presented. The featured controller allows a safe human–robot interaction through energy and power limitations, assuring passivity through energy tanks. The proposed controller is evaluated with a KUKA LWR 4+ arm in a comanipulation environment.

Development of Human-Friendly Robot with Passive Collision Force Suppression Mechanism

Development of Human-Friendly Robot with Passive Collision Force Suppression Mechanism

Enhancing Interpretation of Ambiguous Voice Instructions based on the Environment and the User’s Intention for Improved Human-Friendly Robot Navigation

Human-friendly interactive features are preferred for domestic service robots. Humans prefer to use verbal communication in order to convey instructions to peers. Those voice instructions often include uncertain terms such as “little” and “far”. Therefore, the ability to quantify such information is mandatory for human-friendly service robots. The meaning of such voice instructions depends on the environment and the intention of the user. Therefore, this paper proposes a method in order to interpret the ambiguities in user instructions based on the environment and the intention of the user. The actual intention of the user is identified by analyzing the pointing gestures accompanied with the voice instructions since pointing gestures can be used in order to express the intention of the user. A module called the motion intention switcher (MIS) has been introduced in order to switch the intention of the robot based on the arrangement of the environment and the point referred by the gesture. Experiments have been carried out in an artificially-created domestic environment. According to the experimental results, the behavior of the MIS is effective in identifying the actual intention of the user and switching the intention of the robot. Moreover, the proposed concept is capable of enhancing the uncertain information evaluation ability of robots.

東芝のビーチバレーボールロボット : 人と共存するロボットを目指して (ロボット工学の新しい展開を探る特集号)

東芝のビーチバレーボールロボット : 人と共存するロボットを目指して (ロボット工学の新しい展開を探る特集号)

Compliant Ultrasound Proximity Sensor for the Safe Operation of Human Friendly Robots Integrated with Tactile Sensing Capability

The robot proximity and tactile sensors can be categorized into two groups: grip sensors and safety sensors. They have different performance requirements. The safety sensor should have long proximity range and fast response in order to secure enough response time before colliding with ambient objects. As for the tactile sensing function, the safety sensor need to be fast and compliant to mitigate the impact from a collision. In order to meet these requirements, we proposed and demonstrated a compliant integrated safety sensor suitable to human-friendly robots. An ultrasonic proximity sensor and a piezoelectric tactile sensor made of PVDF films have been integrated in a compliant PDMS structure. The implemented sensor demonstrated the maximum proximity range of 35 cm. The directional tolerance for 30 cm detection range was about ±15° from the normal axis. The integrated PVDF tactile sensor was able to detect various impacts of up to 20 N in a controlled experimental setup.