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In the field of rehabilitation engineering, wearable robots for upper limbs tend to help powerless arms of patients smoothly complete daily activities. Compared with traditional rigid exoskeleton, soft exosuit takes the advantage of high movement flexibility and relatively compact structure so that it could be a more adaptive and compliant alternative for the elder and the disabled. In this study, a novel dual-arm exosuit is proposed to provide active assistance for multiple joints through bidirectional cable-driven modules. Several Bowden cables achieve power transmission from actuators mounted on the back to shoulders and elbows. The actuator is designed with reference to the principle of differential mechanism, in order to automatically preload both cables wrapped around it, generate assistive torque in two opposite rotation directions of a joint, and keep the human-robot interaction as safe as possible. This study adopts the constant torque control to assist in the pre-tightening process, and develop a model-based control strategy for bidirectional joint motion enhancement according to mathematical models of the human-robot system. The experimental results demonstrate that the prototype can impose pretension on each cable, and offer enough support on the joint according to the wearers' demands. [ABSTRACT FROM AUTHOR]

Surgical robots have been widely researched due to their features of accurate positioning, no jitter, high precision, and low error rate under certain tasks. However, it is generally relatively slow to the feedback generated by force, deformation, or sudden and arbitrary impact during operation. Besides, the feedback is always provided through a vision that cannot meet the actual operation requirements for doctors. The customized design and integration of force perception functions on different robots have become one of the research hotspots of surgical robotics-worldwide recently. A force perception sensor for surgical robots based on Fiber Bragg grating (FBG) is proposed in this paper. It can be used to measure three-dimensional force. The experimental parameters are utilized to calibrate the model through the least square method. A four DoFs experimental platform is constructed. The system errors of the sensor involved are evaluated. The effectiveness of the proposed algorithm can be proved by the experimental results

In recent years, more and more research has begun to focus on the flexible and lightweight design of wearable robots. During this process, many novel concepts and achievements have been continuously made and shown to the public, while new problems have emerged at the same time, which need to be solved. In this paper, we give an overview of the development status of soft wearable robots for human movement assistance. On the basis of a clear definition, we perform a system classification according to the target assisted joint and attempt to describe the overall prototype design level in related fields. Additionally, it is necessary to sort out the latest research progress of key technologies such as structure, actuation, control and evaluation, thereby analyzing the design ideas and basic characteristics of them. Finally, we discuss the possible application fields, and propose the main challenges of this valuable research direction. [ABSTRACT FROM AUTHOR]

Human intention recognition belongs to the algorithm basis for exoskeleton robots to generate synergic movements and provide corresponding assistance. In this article, we acquire and analyze the mechanomyography (MMG) to estimate the current joint torque and apply this method to the rehabilitation training research of the upper extremity exosuit. In order to obtain relatively pure biological signals, a MMG processing method based on the Hilbert-Huang Transform (HHT) is proposed to eliminate the mixed noise and motion artifacts. After extracting features and forming the dataset, a random forest regression (RFR) model is designed to build the mapping relationship between MMG and human joint output through offline learning. In addition, an upper extremity exosuit is constructed for multi-joint assistance. Based on the above research, we develop a torque estimation-based control strategy and make it responsible for the intention understanding and motion servo of this customized system. Finally, an actual test verifies the accuracy and reliability of this recognition algorithm, and an efficiency evaluation experiment also proves the feasibility for power assistance. [ABSTRACT FROM AUTHOR]

With the increasing demand for efficiency and intelligence in grinding operations, the research of the automatic robotic processing method for complex surface workpieces becomes necessary. This paper proposes a new approach for robotic grinding on the free-form surface. Particularly, the authors design a novel force-controlled belt grinding tool, on which a contact model of grinding process is further developed. In order to improve the efficiency of grinding, a rapid robot trajectory planning method is proposed based on the workpiece's computer-aided design model, and the process parameters are identified from simple experiments. Furthermore, a piecewise parameterized force control method based on impendence control for the tool is presented, and the purpose of this method is to compensate for the error caused by the rapid planning method and low consistency workblanks. Finally, the grinding experiments of the plate workpiece and complex shape workpiece are performed. The experiment results demonstrate that the proposed method is effective. [ABSTRACT FROM AUTHOR]

This article presents the design, control, and test of a piezo-based passive compliant micro-gripper capable of combining position and force control. The gripper's structure is compact due to a super-large amplification ratio of 52 that is achieved by a two-stage displacement amplifier. The position/force switching control strategy is utilized for the position and force regulation. Particularly, a dual feedforward controller combining Gaussian process regression based hysteresis compensator and input shape technique based vibration suppressor is employed to the position regulation, while a hybrid controller composed of dual feedforward and PID feedback is used for the precision force control. Compared to the conventional design, the system is simplified because displacement sensor is removed. In order to protect the micro-object from contact, the passive compliance design method is introduced to the gripper tip. An experimental study, executing grasp-hold-release operations of a gold wire, is carried out to validate the feasibility of the gripper system. The result confirms that the proposed scheme is feasible and the stable clamping operations can be achieved. [ABSTRACT FROM AUTHOR]

As there are increasing demands for efficiency and quality in airframe assembly, automation integration is required to replace manual operation. This paper presents a design of a robotic riveting cell for wedge part riveting, which is used on the trailing edge of airfoil. To complete the continuous riveting in a row of rivets at the trailing edge, a robotic riveting cell is designed to realize a set of process actions including rivet feeding/injection/cutting and press riveting. Based on the visual compensation of the hole position, a forceless feedback spiral track rivet injection compensation method is proposed. The stress feedback-based riveting process control method is introduced after rivet injection and cutting. The proposed approach is applied to the robotic riveting cell and the rivet injector works stably. No indentation has been detected using the force-controlled riveting method. The prototype can achieve the riveting task well on the wedge part. The proposed design and approach can be applied on both wedge parts and flat parts. This will give a new way to solve the automation integration problem in airframe assembly. A robotic riveting cell is designed to realize a set of process actions. A forceless feedback spiral track rivet injection compensation method is proposed. The stress feedback-based riveting process control method is employed after rivet injection and cutting. [ABSTRACT FROM AUTHOR]

In the grinding process of friction stir weld seams, excessive grinding will cause damage to the base metal and bring significant economic losses. In this paper, the authors design a robotic system for grinding the weld seam and present a monitoring method of excessive grinding. The designed system consists of an industrial robot, a line scanner for measuring the weld seam and a force-controlled grinding tool. Since the result of the measurement of the weld seam is a point cloud, the extraction method of the weld seam point cloud based on graph-cut is proposed in this paper. The extracted features are used as prior knowledge of the monitoring algorithm. On the other hand, by combining the features from the point cloud and force-position information during the processing, a monitoring method for excessive grinding based on PSO-SVM is proposed and verified by experiments. The experiments demonstrate that the proposed method can identify excessive grinding, and the accuracy of recognition is 91.5%. [ABSTRACT FROM AUTHOR]

To overcome the limitations of conventional bistable mechanisms, this paper proposes a novel type of bistable mechanism with linear negative stiffness and large in-plane lateral stiffness. By connecting the novel negative-stiffness mechanism in parallel with a positive-stiffness mechanism, a novel quasi-zero stiffness compliant mechanism is developed, which has good axial guidance capability and in-plane lateral anti-interference capability. Analytical models based on a comprehensive elliptic integral solution of bistable mechanism are established and then the stiffness curves of both conventional and novel bistable mechanisms are analyzed. The quasi-zero stiffness characteristic and High-Static-Low-Dynamic-Stiffness characteristic of the novel compliant mechanism are investigated and its application in constant-force mechanism and vibration isolator is discussed. A prototype with adjustable load-carrying capacity is designed and fabricated for experimental study. In the two experiments, the effectiveness of the proposed quasi-zero stiffness mechanism used in the field of constant-force output and vibration isolation is tested. [ABSTRACT FROM AUTHOR]

The inconsistency of casting parts is a major issue for subsequent automated machining processes. The lack of reasonable machining allowance analysis methods results in low automation level of finish machining process though higher accuracy sensors are well applied in 3D scanning of cast parts. Traditional analysis methods based on nonlinear optimisation are only suitable for sparse point data obtained by CMM (Coordinate-Measuring Machine). As the development of scanners and 3D point cloud registration technology, new methods are applied to machining allowance analysis, but those still fail to face the conditions, such as uncertain datum, casting defect and allowance adjustment. In this paper, an automated approach based on point cloud registration to machining allowance evaluation is presented. Three constraints – envelopment, localisation datum and evenly distributed allowance – are concerned for uncertain conditions of casting parts. Two stages, initial alignment and machining allowance optimisation, are detailed in implementation. This approach is validated to be practical and effective via two created models and several real casting parts. [ABSTRACT FROM AUTHOR]

Traditional renal puncture surgery requires manual operation, which has a poor puncture effect, low surgical success rate, and high incidence of postoperative complications. Robot-assisted puncture surgery can effectively improve the accuracy of punctures, improve the success rate of surgery, and reduce the occurrence of postoperative complications. This paper provides a dual-armed robotic puncture scheme to assist surgeons. The system is divided into an ultrasound scanning arm and a puncture arm. Both robotic arms with a compliant positioning function and master–slave control function are designed, respectively, and the control system is achieved. The puncture arm's position and posture are decoupled by the wrist RCM mechanism and the arm decoupling mechanism. According to the independent joint control principle, the compliant positioning function is realized based on the single-joint human–computer interactive admittance control. The simulation and tests verify its functions and performance. The differential motion incremental master–slave mapping strategy is used to realize the master–slave control function. The error feedback link is introduced to solve the cumulative error problem in the master–slave control. The dual-armed robotic puncture system prototype is established and animal tests verify the effectiveness. [ABSTRACT FROM AUTHOR]

Industrial robots have advantages in the processing of large-scale components in the aerospace industry. Compared to CNC machine tools, robot arms are cheaper and easier to deploy. However, due to the poor consistency of incoming materials, large-scale and lightweight components make it difficult to automate robotic machining. In addition, the stiffness of the tandem structure is quite low. Therefore, the stability of the milling process is always a concern. In this paper, the robotic milling research is carried out for the welding pre-processing technology of large-scale components. In order to realize the automatic production of low-conformity parts, the on-site measurement–planning–processing method is adopted with the laser profiler. On the one hand, the laser profiler hand–eye calibration method is optimized to improve the measurement accuracy. On the other hand, the stiffness of the robot's processing posture is optimized, combined with the angle of the fixture turntable. Finally, the experiment shows the feasibility of the on-site measurement–planning–processing method and verifies the correctness of the stiffness model. [ABSTRACT FROM AUTHOR]

Methods of point cloud registration based on ICP algorithm are always limited by convergence rate, which is related to initial guess. A good initial alignment transformation can sharply reduce convergence time and raise efficiency. In this paper, we propose a global registration method to estimate the initial alignment transformation based on HEALPix (Hierarchical Equal Area isoLatitude Pixelation of a sphere), an algorithm for spherical projections. We adopt EGI (Extended Gaussian Image) method to map the normals of the point cloud and estimate the transformation with optimized point correspondence. Cross-correlation method is used to search the best alignment results in consideration of the accuracy and robustness of the algorithm. The efficiency and accuracy of the proposed algorithm were verified with created model and real data from various sensors in comparison with similar methods. [ABSTRACT FROM AUTHOR]

Background: Robotic systems are increasingly used to enhance clinical outcomes in prostate intervention. To evaluate the clinical value of the proposed portable robot, the robot-assisted and robot-targeted punctures were validated experimentally., Method: The robot registration utilising the electromagnetic tracker achieves coordinate transformation from the ultrasound (US) image to the robot. Subsequently, Transrectal ultrasound (TRUS)-guided phantom trials were conducted for robot-assisted, free-hand, and robot-targeted punctures., Results: The accuracy of robot registration was 0.95 mm, and the accuracy of robot-assisted, free-hand, and robot-targeted punctures was 2.38 ± 0.64 mm, 3.11 ± 0.72 mm, and 3.29 ± 0.83 mm sequentially., Conclusion: The registration method has been successfully applied to robot-targeted puncture. Current results indicate that the accuracy of robot-targeted puncture is slightly inferior to that of manual operations. Moreover, in manual operation, robot-assisted puncture improves the accuracy of free-hand puncture. Accuracy superior to 3.5 mm demonstrates the clinical applicability of both robot-assisted and robot-targeted punctures., (© 2023 John Wiley & Sons Ltd.)

Research on robotic exoskeletons both in the military and medical fields has rapidly expanded over the previous decade. As a human-robot interaction system, it is a challenge to develop an assistive strategy that makes the exoskeleton supply efficient and natural assistance following the user's intention. This paper proposed a novel interaction learning control strategy for the lower extremity exoskeleton. A powerful representative tool probabilistic movement primitives (ProMPs) is adopted to model the motion and generate the desired trajectory in real-time. To adjust the trajectory by the user's real-time intention, a compensation term based on human-robot interaction force is designed and merged into the ProMPs model. Then, compliant impedance control is adopted as a low-level control where the desired trajectory is put into. Moreover, the model will be dynamically adapted online by penalizing both the interaction force and trajectory mismatch, with all the parameters that can be further learned by learning algorithm PI BB . The experimental results verified the effectiveness of the proposed control framework., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Wang, Wu, Gao and Dong.)