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Abstract: Recently, soft grippers have garnered considerable interest in various fields, such as medical rehabilitation, due to their high compliance. However, the traditional PneuNet only reliably grasps medium and large objects via enveloping grasping (EG), and cannot realize pinching grasping (PG) to stably grasp small and thin objects as EG requires a large bending angle whereas PG requires a much smaller one. Therefore, we proposed a multi-structure soft gripper (MSSG) with only one vent per finger which combines the PneuNet in the proximal segment with the normal soft pneumatic actuator (NSPA) in the distal segment, allowing PG to be realized without a loss in EG and enhancing the robustness of PG due to the height difference between the distal and proximal segments. Grasping was characterized on the basis of the stability (finger bending angle describes) and robustness (pull-out force describes), and the bending angle and pull-out force of MSSG were analyzed using the finite element method. Furthermore, the grasping performance was validated using experiments, and the results demonstrated that the MSSG with one vent per finger was able to realize PG without a loss in EG and effectively enhance the PG robustness. PubDate: 2023-06-01
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Abstract: To reduce the risk of infection in medical personnel working in infectious-disease areas, we proposed a hyper-redundant mobile medical manipulator (HRMMM) to perform contact tasks in place of healthcare workers. A kinematics-based tracking algorithm was designed to obtain highly accurate pose tracking. A kinematic model of the HRMMM was established and its global Jacobian matrix was deduced. An expression of the tracking error based on the Rodrigues rotation formula was designed, and the relationship between tracking errors and gripper velocities was derived to ensure accurate object tracking. Considering the input constraints of the physical system, a joint-constraint model of the HRMMM was established, and the variable-substitution method was used to transform asymmetric constraints to symmetric constraints. All constraints were normalized by dividing by their maximum values. A hybrid controller based on pseudo-inverse (PI) and quadratic programming (QP) was designed to satisfy the real-time motion-control requirements in medical events. The PI method was used when there was no input saturation, and the QP method was used when saturation occurred. A quadratic performance index was designed to ensure smooth switching between PI and QP. The simulation results showed that the HRMMM could approach the target pose with a smooth motion trajectory, while meeting different types of input constraints. PubDate: 2023-06-01
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Abstract: We proposed a method for shape sensing using a few multicore fiber Bragg grating (FBG) sensors in a single-port continuum surgical robot (CSR). The traditional method of utilizing a forward kinematic model to calculate the shape of a single-port CSR is limited by the accuracy of the model. If FBG sensors are used for shape sensing, their accuracy will be affected by their number, especially in long and flexible CSRs. A fusion method based on an extended Kalman filter (EKF) was proposed to solve this problem. Shape reconstruction was performed using the CSR forward kinematic model and FBG sensors, and the two results were fused using an EKF. The CSR reconstruction method adopted the incremental form of the forward kinematic model, while the FBG sensor method adopted the discrete arc-segment assumption method. The fusion method can eliminate the inaccuracy of the kinematic model and obtain more accurate shape reconstruction results using only a small number of FBG sensors. We validated our algorithm through experiments on multiple bending shapes under different load conditions. The results show that our method significantly outperformed the traditional methods in terms of robustness and effectiveness. PubDate: 2023-06-01
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Abstract: This study focuses on a robot vision localization method for coping with the operational task of automatic nasal swab sampling. The application is important in the detection and epidemic prevention of Corona Virus Disease 2019 (COVID-19) to alleviate the large-scale negative impact of individuals suffering from pneumonia owing to COVID-19. In this method, the idea of a hierarchical decision network is used to consider the strong infectious characteristics of the COVID-19, which is followed by processing the robot behavior constraint condition. The visual navigation and positioning method using a single-arm robot for sampling is also planned, which considers the operation characteristics of medical staff. In the decision network, the risk factor for potential contact infection caused by swab sampling operations is established to avoid the spread among personnel. A robot visual servo control with artificial intelligence characteristics is developed to achieve a stable and safe nasal swab sampling operation. Experiments demonstrate that the proposed method can achieve good vision positioning for the robots and provide technical support for managing new major public health situations. PubDate: 2023-06-01
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Abstract: For effectively improving the overall performance of fire truck frame structure, and solving the complexity of previous methods in the frame optimization design process, the traditional grey relational grade ranking needs to be improved. First, the first-order modal test was conducted to verify the validity of the initial frame model. Then, based on this model, a high-strength steel frame was designed to reduce deformation, maximum stress, and frame mass, and increase the fatigue life and the frequencies of the first bending modal and first torsional modal. Sixty groups of sample points were generated through Hammersley method. Subsequently, improved grey relational analysis with principal component analysis was proposed to realize the optimal design of the frame structure. Finally, the optimal combination of design parameters for the frame was obtained using the proposed method. Meanwhile, the optimized frame structure is found by comparing the models before and after optimization, and the mass is reduced by 14.8%. Moreover, the computational cost can be reduced by 135% when the proposed method is compared with the previous algorithm. Therefore, the proposed method can effectively improve the performance of the frame and improve the computational efficiency. PubDate: 2023-04-28
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Abstract: With advancements in medical imaging and robotic technology, the idea of fully autonomous diagnosis and treatment has become appealing, from ethereal to tangible. Owing to its characteristics of non-invasiveness, non-radiation, and fast imaging speed, ultrasonography has been increasingly used in clinical practice, such as in obstetrics, gynecology, and surgical puncture. In this paper, we propose a real-time image-based visual servo control scheme using a hybrid slice-to-volume registration method. In this manner, the robot can autonomously locate the ultrasound probe to the desired posture according to preoperational planning, even in the presence of disturbances. The experiments are designed and conducted using a thyroid biopsy phantom model. The results show that the proposed scheme can achieve a refresh rate of up to 30 Hz and a tracking accuracy of (0.52±0.65) mm. PubDate: 2023-04-28
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Abstract: Age-related diseases can lead to knee joint misfunction, making knee assistance necessary through the use of robotic wearable braces. However, existing wearable robots face challenges in force transmission and human motion adaptation, particularly among the elderly. Although soft actuators have been used in wearable robots, achieving rapid response and motion control while maintaining portability remains challenging. To address these issues, we propose a soft-robotic knee brace system integrated with multiple sensors and a direct-drive hydraulic actuation system. This approach allows for controlled and rapid force output on the portable hydraulic system. The multi-sensor feedback structure enables the robotic system to collaborate with the human body through human physiological signal and body motion information. The human user tests demonstrate that the knee robot provides assistive torques to the knee joint by being triggered by the electromyography signal and under human motion control. PubDate: 2023-04-28
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Abstract: Force sensing is vital for situational awareness and safe interaction during minimally invasive surgery. Consequently, surgical robots with integrated force-sensing techniques ensure precise and safe operations. Over the past few decades, there has been considerable progress in force-sensing techniques for surgical robots. This review summarizes the existing electrically- and optically-based force sensors for surgical robots, including piezoresistive, piezoelectric, capacitive, intensity/phase-modulated, and fiber Bragg gratings. Their principles, applications, advantages, and limitations are also discussed. Finally, we summarize our conclusions regarding state-of-the-art force-sensing technologies for surgical robotics. PubDate: 2023-04-28
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Abstract: Moving object segmentation (MOS) is one of the essential functions of the vision system of all robots, including medical robots. Deep learning-based MOS methods, especially deep end-to-end MOS methods, are actively investigated in this field. Foreground segmentation networks (FgSegNets) are representative deep end-to-end MOS methods proposed recently. This study explores a new mechanism to improve the spatial feature learning capability of FgSegNets with relatively few brought parameters. Specifically, we propose an enhanced attention (EA) module, a parallel connection of an attention module and a lightweight enhancement module, with sequential attention and residual attention as special cases. We also propose integrating EA with FgSegNet_v2 by taking the lightweight convolutional block attention module as the attention module and plugging EA module after the two Maxpooling layers of the encoder. The derived new model is named FgSegNet_v2_EA. The ablation study verifies the effectiveness of the proposed EA module and integration strategy. The results on the CDnet2014 dataset, which depicts human activities and vehicles captured in different scenes, show that FgSegNet_v2_EA outperforms FgSegNet_v2 by 0.08% and 14.5% under the settings of scene dependent evaluation and scene independent evaluation, respectively, which indicates the positive effect of EA on improving spatial feature learning capability of FgSegNet_v2. PubDate: 2023-04-20
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Abstract: Recognizing and reproducing spatiotemporal motions are necessary when analyzing behaviors and movements during human-robot interaction. Rigid body motion trajectories are proven as compact and informative clues in characterizing motions. A flexible dual square-root function (DSRF) descriptor for representing rigid body motion trajectories, which can offer robustness in the description over raw data, was proposed in our previous study. However, this study focuses on exploring the application of the DSRF descriptor for effective backward motion reproduction and motion recognition. Specifically, two DSRF-based reproduction methods are initially proposed, including the recursive reconstruction and online optimization. New trajectories with novel situations and contextual information can be reproduced from a single demonstration while preserving the similarities with the original demonstration. Furthermore, motion recognition based on DSRF descriptor can be achieved by employing a template matching method. Finally, the experimental results demonstrate the effectiveness of the proposed method for rigid body motion reproduction and recognition. PubDate: 2023-04-20
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Abstract: A blasting-like lubricating process (combination of shot blasting and lubricating processes) is proposed. In this process, the specimens to be treated, alloy shots, and solid lubricating powder are rotated together in a roller. The surface pockets formed due to the impact by the shots can store lubricants, and the lubricant can also adhere to the specimen surface by hitting. The effects of process parameters, including rolling time, rotational speed, mass of alloy shots, and the diameter of shots, on the surface topography of the steel specimen are investigated using 13 experimental schemes. The distribution ratio and average depth of surface pockets on the defined areas of the specimen are quantitatively analyzed. Four selected schemes with the MoS2 solid lubricating powder are further carried out to lubricate the cylindrical billets, and the lubricating effect is evaluated using the steady combined forward and backward extrusion test. The indicated friction factor of the novel blasting-like process is smaller than that of the conventional phosphate-soap coating process. PubDate: 2023-04-19
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Abstract: Permanent magnet synchronous motor (PMSM) is widely used in alternating current servo systems as it provides high efficiency, high power density, and a wide speed regulation range. The servo system is placing higher demands on its control performance. The model predictive control (MPC) algorithm is emerging as a potential high-performance motor control algorithm due to its capability of handling multiple-input and multiple-output variables and imposed constraints. For the MPC used in the PMSM control process, there is a nonlinear disturbance caused by the change of electromagnetic parameters or load disturbance that may lead to a mismatch between the nominal model and the controlled object, which causes the prediction error and thus affects the dynamic stability of the control system. This paper proposes a data-driven MPC strategy in which the historical data in an appropriate range are utilized to eliminate the impact of parameter mismatch and further improve the control performance. The stability of the proposed algorithm is proved as the simulation demonstrates the feasibility. Compared with the classical MPC strategy, the superiority of the algorithm has also been verified. PubDate: 2023-04-13
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Abstract: In view of the problem that crystalline particles cause wall vibration at a low temperature, based on two-phase flow model, computational fluid dynamics is used to conduct the numerical simulation of internal flows when the valve openings are 20%, 60% and 100% respectively. The molten salt flow may be changed under strict conditions and produce forced vibration of the inner parts of molten salt particle shock valve body. Euler two-phase flow model is used for different molten salt sizes to extract temporal pressure pulse information and conduct statistical data processing analysis. The influence of the molten salt crystallization of molten salt particles on the flow and pressure pulse strength is analyzed. The results show that the crystallization of molten salt has a serious impact on the vibration of the valve body, especially in the throttle rate. The valve oscillation caused by the pressure pulsation mostly occurs from the small opening rate. As the opening increases, the pressure pulse threshold and its change trend decrease. PubDate: 2023-04-13
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Abstract: Large unmanned underwater vehicles can carry big payloads for varied missions and it is desirable for them to possess an upright orientation during payload release. Their attitude can hardly be maintained during and after the phase of payload release. Releasing a payload from the vehicle induces uncertainties not only in rigid-body parameters, e.g, the moment of inertia tensor due to the varying distribution of the masses on board the vehicle, but also in the hydrodynamic derivatives due to the vehicle’s varying geometric profile. A nonlinear attitude stabilizer that is robust to these time-varying model uncertainties is proposed in this paper. Stability is guaranteed via Lyapunov stability theory. The simulation results verify the effectiveness of the proposed approach. PubDate: 2023-04-01
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Abstract: Novel gel polymer electrolytes (GPEs) composed of polyvinyl alcohol (PVA) and sodium thio-cyanate were developed via a solution casting technique. An ionic liquid (IL), 1-ethyl-3-methyl-imidazolium tricyanomethanide ([EMIM][TCM]), was doped into a polymer-salt complex system (PVA + NaSCN) to further enhance the conductivity. IL-doped polymer electrolyte (ILDPE) films were characterized using X-ray diffraction (XRD), polarized optical microscopy (POM), Fourier-transform infrared (FTIR) spectroscopy, and conductivity measurements. XRD was performed to check the degree of crystallinity and amorphicity of the ILDPE films, and the amorphicity of GPEs increased with the increase of the IL content. POM was employed to evaluate the changes in the surface morphology due to the inclusion of salt and IL in the PVA. The compositional nature of the GPE films was examined via FTIR studies. The electrical and electrochemical properties were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The maximum conductivity for the GPE film was estimated to be 1.10 × 10−5 S/cm for 6% (mass fraction) of IL in the polymer-salt complex. The ionic transference number was approximately 0.97. An electrochemical double-layer capacitor (EDLC) was built from optimized GPE films and reduced graphene oxide-based electrodes. The specific capacitance calculated from the cyclic voltammograms of the EDLC cells was 3 F/g. PubDate: 2023-04-01
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Abstract: Using fast multiple rotation rolling (FMRR), a nanostructure layer was fabricated on the surface of Ti6Al4V alloy. The microstructure of the surface layer was investigated using optical microscopy, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. The results indicated that a nanostructured layer, with an average grain size of 72–83 nm, was obtained in the top surface layer, when the FMRR duration was 15 min. And the average grain size further reduced to 24–37 nm when the treatment duration increased to 45 min. High density dislocations, twins, and stacking faults were observed in the top surface layer. The microhardness of FMRR specimen, compared with original specimen, was significantly increased. A uniform, continuous and thicker compound layer was obtained in the top surface of FMRR sample, and the diffusion speed of N atom in the top surface layer was accelerated. FMRR treatment provides corrosion improvement. PubDate: 2023-04-01
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Abstract: The mechanical state of cantilever gearbox housing is different from ordinary ones due to the long arm of force caused by cantilever structure. Conventional mechanical analysis methods either took cantilever gearbox housing as ordinary ones or cantilever beam. Few published papers have specially focused on mechanical analysis method for cantilever gearbox housing. This paper takes a longwall shearer cutting unit gearbox (SCUG) as an example and the mechanical analysis method is investigated according to the causes of fatigue for SCUG. Force analysis model is established for finding out regions of static fatigue caused by low-frequency loads, and local resonance analysis is used for finding out regions of vibration fatigue caused by high-frequency loads. Not only bending moment but also torque caused by gear meshing forces is taken into account in the force analysis model. Vibration response is obtained from cutting experiment, and dominant frequencies of local resonance are obtained by frequency domain analysis. Finite element model of SCUG is established, and natural frequencies and strain modes are analyzed for obtaining the main vibration modes corresponding to dominant frequencies. Hence, large stress regions caused by low and high frequency loads are obtained. Results show that the worst working condition is oblique cutting, and the stress of B-B in 600 mm cutting depth can reach 166 MPa. Obviously, 950 Hz, 1 250 Hz, and 1400 Hz are dominant frequencies of SCUG (23rd, 25th and 27th natural frequencies). Generally, this paper proposes some principles for mechanical analysis method of cantilever gearbox housing. PubDate: 2023-04-01
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Abstract: On the multi-layer forging die used in daily life, stressed ring can strength the die structure within elastic deformation and the die material can be self-strengthened through uniform plastic deformation by autofrettage effect, whereas the thermal effect generated during forging process can directly influence the stress state and dimension of the forging die in service. In this study, an analytical solution of the thermo-elastic-plastic deformation in the forging die is derived. The relationships between the radial and circumferential stresses and the temperature distribution, which are directly related to geometric parameters, material properties and working pressure, are determined. This helps to better understand the thermo-elastic-plastic deformation behavior of the die and design the combined forging die to achieve long service life and high accuracy product. PubDate: 2023-04-01
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Abstract: China is rapidly becoming an aging society, leading to a significant demand for chronic disease management and personalized healthcare. The development of rehabilitation and assistive robotics in China has gathered significant attention not only in research fields but also in industries. Such robots aim to either guide patients in completing therapeutic training or assist people with impaired functions in performing their daily activities. In the past decades, we have witnessed the advancement in rehabilitation and assistive robotics, with diverse mechanical designs, functionalities, and purposes. However, the construction of dedicated regulations and policies is relatively lagged compared with the flourishing development in research fields. Moreover, these kinds of robots are working or collaborating closely with human beings, bringing unprecedented considerations on ethical issues. This paper aims to provide an overview of major dilemmas in the development of rehabilitation and assistive robotics in China and propose several potential solutions. PubDate: 2023-04-01
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Abstract: Nasopharyngeal carcinoma is a malignant tumor originating from the nasal mucosa. It is a malignant tumor of the head and neck. Concentric tube robot (CTR), as it can form a complicated shape and access hard-to-reach lesions, is often used in minimally invasive surgeries. However, some CTRs are bulky because of their transmission design. In this paper, a light CTR based on double-threaded helical gear tube is proposed. Such a CTR is less cumbersome than the traditional CTR as its actuation unit is compact and miniaturized. The mapping relationship between the gear tube attitude and motor output angle is obtained by kinematic analysis. The precision, stability, and repeatability of the driving mechanism are tested. The experimental results show that the positioning error in the translation test is less than 0.3 mm, the rolling angle error in the stability test is less than 0.6°, and the error in the translation repeatability test is less than 0.005 mm. Finally, a tip-targeting test is performed using the new CTR, which verifies the feasibility of the CTR for surgeries. PubDate: 2023-04-01
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