The zebrafish is a highly promising model organism in biomedical research. A critical procedure for its use is the microinjection of larvae, which is commonly performed manually. Manual injection, however, suffers from inherent limitations, including low efficiency, success rate, and consistency. To address these challenges, this paper presents a Robotic Batch Microinjection System (RBMS) designed for targeting the hearts of zebrafish larvae. The system’s uniqueness lies in a novel computer vision algorithm that efficiently locates the heart region based on key physiological features, significantly accelerating image processing. Furthermore, an Agarose Petri Dish (APD) is employed for batch immobilization of larvae. We established a dedicated hardware system for automated microinjection and developed an intuitive software interface. Experimental results demonstrate that the RBMS achieves high-throughput automated microinjection into the larval heart at a rate of 11 seconds per sample. The developed system offers a robust and efficient solution for large-scale cardiovascular drug screening using zebrafish larvae.

Regular cleaning and maintenance of high-altitude pipes and curved surfaces on high-rise buildings are high-risk tasks for human workers due to the difficulty of working on curved planes. To address such challenge, automated robots are widely used for cleaning buildings with flat walls, but they cannot climb on curved surfaces, limiting their practical applications. This paper proposes a novel biped curved-surface climbing robot (BCCR) with five-degree-of-freedom (5-DOF) motion. The BCCR features adaptive vacuum suction modules that can adhere to both curved and flat surfaces, allowing seamless movement of the BCCR across various surfaces. Each terminal suction module is composed of three small suction cups, which are capable of rotating in all directions to achieve adaptive adhesion on various surfaces. The 5-DOF structure enables the robot to cross obstacles and makes it highly versatile for various cleaning tasks on a wide range of surfaces, including large curved pipes. The mechanism design and analytical modeling of the BCCR are carried out, demonstrating its robust curved-surface climbing capabilities. Moreover, a prototype is fabricated for experimental investigation. The results indicate that the proposed 5-DOF BCCR can achieve stable climbing on curved surfaces.

This paper proposes a novel adaptive global sliding mode control strategy for a two-degree-of-freedom (2-DOF) piezoelectric nanopositioning system based on the integral extended state observer (IESO) technique. Its uniqueness is that a global robustness property is generated in the whole precision motion control process, which effectively circumvents sensitivity to the perturbations during the reaching phase. First, to generate an accurate disturbance estimation for compensation control, the IESO is constructed by incorporating an integral action into the observer design. Then, a global sliding mode control approach is developed for the nanopositioning system to ensure global robustness against the unknown hysteresis nonlinearity and cross-axis coupling motion. Moreover, an adaptive rule is established for the global sliding mode controller, which does not require a priori knowledge of the estimation error, hysteresis, and cross-coupling nonlinearity in the control design. Both simulation and experimental studies are conducted to demonstrate the effectiveness and superiority of the proposed motion control scheme over existing ones. Note to Practitioners—Nanopositioning systems actuated by piezoelectric actuators impose a great challenge to achieve precision motion tracking control. This work reports a global sliding mode control strategy of 2-DOF piezoelectric nanopositioning systems for the first time. By constructing a global sliding surface and control compensator, the global robustness to unknown hysteresis and cross-axis coupling effect can be improved in the whole process to achieve high-precision motion. To guarantee the estimation performance of unknown nonlinearities, an IESO is designed in this paper to suppress the total disturbance. Additionally, to suppress the effects of estimation errors and achieve high-precision motion tracking, two adaptive rules are established to approximate the upper bounds of estimation errors and the integral term in IESO. Compared to previous works, the proposed control scheme is easy to implement and provides superior results, as verified by simulation and experimental results.

This paper proposes a new teleoperated telepresence robot system with high-fidelity haptic feedback for interaction work, such as pre-operation of explosive ordnance disposal (EOD). The system includes a master device and a slave collaborative robot. The master device enables the human operator to feel the operation procedure when performing the environmental interaction task. The system’s kinematics and dynamics models are derived, laying the foundation for the control scheme design. To meet the requirements of EOD missions, a hybrid motion mapping method including position-velocity (PV) and position-position (PP) mapping modes is presented to achieve a balance between working efficiency and manipulation accuracy. A hybrid haptic force rendering method is introduced to facilitate the human’s feeling of the interacting force and control the slave robot in PP and PV mapping modes, respectively. Experimental results reveal that the developed system exhibits good position and velocity tracking performance with root-mean-square (RMS) errors of 0.004 m and 0.007 m/s, respectively. The haptic tracking is realized with an RMS force error of 0.14 N. Moreover, the developed system can improve the EOD working efficiency by 10.7% with accurate operation while ensuring the fidelity of the haptic feedback to feel the contact process. The reported telepresence robot system provides a promising solution to delicate remote interaction operations.Note to Practitioners—Teleoperated robotic systems are commonly utilized to perform hazardous tasks such as EOD tasks. However, the existing EOD robots controlled by the joystick have limited dexterity. Moreover, visual feedback alone cannot provide enough telepresence for an operator, which leads to low efficiency. This paper proposes a new teleoperated robot system with high-fidelity haptic feedback assistance intended for EOD tasks. The system integrates the motion mapping method that combines PP and PV modes to improve the working efficiency while maintaining manipulation accuracy. The haptic sensations feedback can switch the rendering mode according to different control modes. The haptic feedback mechanism enables the operators to feel reliable contact under PP mapping mode and ensures safety and stability under PV mapping mode. Performance testing and application experiment verified the feasibility of the reported robotic system.

The steering dynamics of marine robots play a pivotal role in achieving precise maneuvering. However, complex and unpredictable ocean disturbances pose challenges for rapid online learning of accurate dynamics. This paper presents the Online Memory Koopman Learning (OM-Koop) framework, a hybrid model that combines physical priors, online data and stability preserving mechanisms to solve the nonlinear dynamic capture challenge and dynamically adapt to the marine environment. Firstly, we construct the Koopman operator-based uncertainty model online using the state error of the steering model and sliding window methods. The model can effectively capture the nonlinear features that are not represented in the predefined steering model. To ensure stability, the eigenvalues of the Koopman operator are constrained during online learning, guaranteeing Lyapunov stability. Secondly, in order to improve the efficiency of online learning, the Long Short-Term Memory (LSTM) neural network is involved in the construction process of the Koopman operator, which enhances the model’s memory capability. Finally, through field experiments using Autonomous Surface Vehicles (ASVs) and Autonomous Underwater Vehicles (AUVs) in field environments, comparative analyses with other learning strategies show that OM-Koop has excellent adaptability and robustness while guaranteeing Lyapunov stability. Note to Practitioners—The motivation of this article is that the steering dynamic behavior of marine robots is highly affected by unpredictable ocean environments, which poses great challenges in achieving precise manipulation in practical applications. In this paper, we propose the OM-Koop framework to address these challenges by integrating physical priors, online data learning, and stability preserving mechanisms. Theoretical analyses show that the proposed framework ensures Lyapunov stability while dynamically adapting to nonlinear disturbing forces imposed by the environment. Field experiments on AUV and ASV validate the robustness and adaptability of the framework, demonstrating its potential for practical deployment in dynamic marine environments. And the proposed framework has prospects for practical applications in other robotic systems.

Cleaning high-altitude building windows is traditionally a high-risk task for human workers due to the danger of falls. To enhance safety in facade cleaning and similar tasks, the development of window-cleaning robots has become increasingly essential. However, current robots face challenges in navigating exoskeleton structures due to obstructive beams, limiting their application. This article proposes a novel biped window-cleaning robotic system (BWCRS) designed for exoskeleton structures. The system comprises two key components: a multifunctional biped climbing robot (BCR) and a specialized cleaning robot. The BCR is adept at overcoming obstacles inherent in exoskeleton structures and transitioning across various inclined window surfaces. The BCR adopts a symmetrical construction, and the ends of the feet are equipped with vacuum suction cups and electromagnets, which can switch between different actuators at the geometric base and end of the system. The system is further enhanced by air pressure sensors that monitor the suction cup adhesion in real time, ensuring stable operation. A crucial functionality of the BCR is its manipulation mode, guided by a visual camera. This mode enables precise location and manipulation of the cleaning robot, ensuring effective coverage of all window areas. The mechanical design and mathematical modeling of the BWCRS are thoroughly examined, demonstrating its robust window-cleaning capabilities. The experimental results reveal that the proposed BCR has a favorable window-climbing and manipulation ability and that the BWCRS has a favorable cleaning effect on the exoskeleton-structure windows. Note to Practitioners—This paper is motivated by the problem of window-cleaning for exoskeleton structures, but it also applies to solving window maintenance and inspection. Previous window-cleaning robots were mainly aimed at the facades or surfaces with low obstacles that cannot be applied directly to exoskeleton-structured windows. This paper proposes an exoskeleton-structure window-cleaning method based on a biped window-climbing robot and a cleaning robot. The biped robot can climb over obstacles on the exoskeleton structures and manipulate the cleaning robot to different cleaning areas. Here, we introduce the biped window-climbing robot from the perspective of mechanical design and mathematical kinematics. We then demonstrate multiple obstacle-crossing motion modes of the biped window-climbing robot. Combined with visual-based manipulation, the window-cleaning process for the exoskeleton structures by a biped window-climbing robot integrated with a cleaning robot is demonstrated. The results verify that the proposed design can complete window-cleaning tasks on exoskeleton structures.

Wirelessly actuated magnetic microrobots are promising tools in medical applications due to their tiny sizes and attractive robotic properties. However, it remains a huge challenge to integrate sufficient functionalities in a limited volume. Microscopic natural phenomenon is a great reference for current microrobot design, where the underlying intelligence and subtlety spurs related modern artificial systems. Inspired by air bubbles in nature, herein, we report a kind of novel magnetic air bubble microrobots. The air bubble-based structure enables multiple functionalities including cargo delivery, multimode locomotion, micromanipulation, medical imaging, and biosensing. The proposed microrobot is essentially Pickering bubbles composed of magnetic particles and air bubbles. Their hollow structures help produce lighter microrobots with density less than 1 g/cm3, enabling buoyancy-based self-propulsion. Buoyancy and magnetic forces actuation enables flexible 3D locomotion in fluidic environments. Experimental results show that the microrobots can be controlled properly for designated assignments. Furthermore, the introduction of air bubble enhances ultrasound imaging, facilitating further in vivo applications. These findings offer a significant microrobot design paradigm by exploiting natural physical intelligence at the small scale.

This paper presents an intraoperatively iterative Hough transform (IHT) based in-plane hybrid control of extracorporeal ultrasound (US) guided magnetic catheterization for arterial intervention. One uniqueness lies in that both control and tracking of the arterial robotic ultrasound end-effector have been implemented to improve performance. Firstly, the magnetic catheter model and hybrid visual/force servoing control scheme of the extracorporeal ultrasound-integrated tracking arm (EUTA) are derived based on the interaction Jacobian matrix and impedance modeling. Meanwhile, we implement a tracking method of in-plane ultrasound catheter’s tip and detection of vascular boundaries utilizing intensity-level iterative Hough-transform with Iterative End-Ponit Fitting (IEPF). The effectiveness of the proposed control and tracking method has been verified by conducting in vitro experimental studies for catheter steering of a soft tissue-imitating phantom. Results show that an average steering error of 0.56 mm and signal-to-noise-ratio (SNR) of 12.2 are obtained for the ultrasound imaging at high synchronization along with a low target lost rate (15.8%) and constant-force tracking (2.50±1.02 N).

This paper presents the design and development of a new flexure-based XYZ micropositioner with a hybrid kinematic configuration. A piezoelectric-driven Z stage is embedded into a parallel-kinematic XY stage actuated by two voice coil motors. The XYZ micropositioner features a sizeable workspace with a compact architecture, which benefits from employing deployable mechanisms and mixed actuators. One uniqueness is that the Z-axis crosstalk error of the XYZ micropositioner is compensated by the closed-loop motion control of the Z stage, which achieves a constant vertical position of the center platform when performing planar motion tasks. Analytical models have been derived based on fixed-guided beam theory to assess the driving stiffness of the mechanism. The finite element analysis is carried out to verify the accuracy of the derived models. A prototype system of the XYZ micropositioner is fabricated with the dimension of 116 mm$\times$116 mm$\times$45 mm (i.e., 216 mm$\times$216 mm$\times$45 mm with actuators). Experimental results indicate that it obtains a workspace of 4.15 mm$\times$4.06 mm$\times$0.04 mm with a crosstalk of less than 1% among the three axes. With the active control of the Z-axis position, the vertical crosstalk error has been dramatically reduced from 7.333 to 1.719$\mu$m. The proposed design provides a promising approach to enable pure planar motion for ultrahigh precision applications requiring optical or electron focusing, such as electron beam lithography.Note to Practitioners—Flexure-based micropositioners are essential for the semiconductor manufacturing process, atomic force microscopy, and microassembly, due to their high precision and reliability. Many applications demand a planar motion without vertical crosstalk to realize ultrahigh precision operation. For the first time, this paper proposes the concept design of an XYZ micromanipulator by utilizing a Z stage to compensate for the vertical crosstalk error generated by the X/Y-axis motion, which is not considered and is difficult to realize in conventional XY flexible stage design. The simulation has confirmed the effectiveness of the derived analytical models. The XYZ micropositioner’s static and dynamic characteristics are then experimentally evaluated on a fabricated prototype. The travel stroke, coupling displacement, driving stiffness, and resonant frequency have been tested. Experimental results reveal that the active compensation has significantly diminished the Z-axis parasitic errors. The performance comparison results validate the superiority of the proposed concept design.

This paper presents the design and development of a novel bioinspired rigid-soft hybrid robotic gripper with versatile grasping primitives and enhanced robustness. It achieves variable joint/tissue stiffness by resorting to hybrid ratchet joints and phalanges. For the first time, the proposed hybrid ratchet joint (HRJ) can selectively switch to four modes to generate tunable flexion/extension locking torque by activating specific clutching ratchets with soft-cell structures. The multi-layer hybrid phalanx can exert suction-lift grasp and adjustable contact stiffness, which are theoretically modeled and experimentally validated by mounting them on articulated fingers. With the proposed HRJs and hybrid phalanges, a tendon-based hybrid gripper is designed and fabricated to evaluate the grasping performance for universal picking and manipulation. Extensive grasping tests are conducted in six representative primitives (including suction-lift and suction-pinch), demonstrating the multi-mode grasping capability in extremely thin and wide objects. Compared with conventional gripper configurations, the proposed hybrid phalanges and HRJs improve the grasping force and enveloping stiffness by 205.1% and 97.9%, respectively.Note to Practitioners—For automated grasping of diverse objects, a bioinspired robotic gripper is proposed to enable adjustable compliant stiffness and suction-lift motion. With the same mobility as conventional tendon grippers, the reported hybrid gripper exhibits wide-range adjustable stiffness and demonstrates versatile adhesive primitives and enhanced robustness in grasping tasks. Experimental investigation is conducted to verify the tissue suction effect and stiffness modulation, demonstrating their contributions to grasping operations in terms of suction-augmented primitives and improved grasping stability. With the characteristics of HRJs and hybrid phalanges, the gripper actuation strategies are elaborated via six representative primitives, including parallel grasp, suction-lift, and newly defined suck-pinch. Extensive grasping trials are demonstrated to pick thin, large, and tiny objects (e.g., wide plates, toolboxes, and tweezers). The experimental results validate the feasibility and superiority of the proposed hybrid gripper design by fusing intrinsic dexterity, manipulability, and compliance from rigid and soft mechanisms.

Microinjection with force sensing plays an important role in delivering foreign materials into biological entities. In this paper, a new force-sensing microinjector with compliant mechanism is presented. It provides a high sensitivity of force sensing by offering a small stiffness in the direction of microinjection. Meanwhile, it enables a sufficient load-bearing capability thanks to a large stiffness in the lateral direction. The small stiffness is realized by the combination of a positive-stiffness mechanism and a negative-stiffness mechanism, rather than a zero-stiffness mechanism. A custom-made capacitive force sensor based on tilted micropillar array is introduced to measure the microinjection force based on the microinjector’s output displacement. Moreover, a prototype has been fabricated for experimental testing. Experimental results show that the sensitivity of the proposed design has been improved by two-fold over previous work. The developed microinjector has been applied to successfully detect the microinjection force during the injection of zebrafish larvae, which renders a promising solution for regulating the microinjection force.Note to Practitioners—Force-assisted microinjection can provide force feedback, which is desirable to protect biological samples from excessive force and to judge successful penetration. Currently, most existing force sensor-based microinjectors can only puncture biological samples, rather than injecting materials, mainly due to the inability of bearing the weight of linker for the injection needle and actuator. In this work, a new microinjector with capacitive force sensor is presented for microinjection of zebrafish larvae. Based on the combination of a positive-stiffness mechanism and a negative-stiffness mechanism, a small-stiffness mechanism is introduced to design the microinjector. It simultaneously provides large axial sensitivity and large lateral loading ability. Moreover, a capacitive force sensor based on tilted micropillar array is devised to measure the microinjection force based on the overall displacement of the microinjector. For fixing zebrafhish larvae, a micro-array petri dish is fabricated by silicon wafer mould. Experimental results show that the microinjector is capable of delivering foreign materials and detecting the microinjection force, which is beneficial to the microinjection operation.

Event cameras are neuromorphic vision sensors that record a scene as sparse and asynchronous event streams. Most event-based methods project events into dense frames and process them using conventional vision models, resulting in high computational complexity. A recent trend is to develop point-based networks that achieve efficient event processing by learning sparse representations. However, existing works may lack robust local information aggregators and effective feature interaction operations, thus limiting their modeling capabilities. To this end, we propose an attention-aware model named Event Voxel Set Transformer (EVSTr) for efficient spatiotemporal representation learning on event streams. It first converts the event stream into voxel sets and then hierarchically aggregates voxel features to obtain robust representations. The core of EVSTr is an event voxel transformer encoder that consists of two well-designed components, including the Multi-Scale Neighbor Embedding Layer (MNEL) for local information aggregation and the Voxel Self-Attention Layer (VSAL) for global feature interaction. Enabling the network to incorporate a long-range temporal structure, we introduce a segment modeling strategy (S2TM) to learn motion patterns from a sequence of segmented voxel sets. The proposed model is evaluated on two recognition tasks, including object classification and action recognition. To provide a convincing model evaluation, we present a new event-based action recognition dataset (NeuroHAR) recorded in challenging scenarios. Comprehensive experiments show that EVSTr achieves state-of-the-art performance while maintaining low model complexity.

The nonlinearity and cross-axis coupling of piezo-driven multiple-degree-of-freedom (multi-DOF) nanopositioning systems impose challenges to achieving precise and reliable motion control. This paper develops a new adaptive reliable control approach for a 2-DOF piezoelectric nanopositioning system utilizing a fuzzy back-stepping strategy. First, a virtual tracking model is constructed to address the stabilization problem via a system transformation method. Then, a fuzzy logical system (FLS) model is introduced to mitigate the effects of hysteresis and unmodeled high-order nonlinearity. To obtain high-precision motion tracking with high reliability, the approximation of the unknown piezoelectric actuator's efficiency factor is injected into the reliable controller of nanopositioning systems. Furthermore, an adaptive mechanism based on tracking errors is designed to adjust control parameters automatically to improve the robustness to unknown perturbations. Simulation and practical experiment examples are presented to show the effectiveness and potential of the developed fuzzy reliable nanopositioning control method over existing control approaches.

Autonomous magnetic catheterization has become a promising technology for next-generation minimally invasive cardiovascular surgery. In this paper, a novel homocentric variable-stiffness magnetic robotic catheter (HVS-MRC) is presented. This device is controlled by a multi-arm robot-assisted catheterization system for use in radiation-free coronary ultrasound intervention. The uniqueness of the HVS-MRC is the generation of variable stiffness through the telescopic motion of three homocentric components with embedded internal magnets. These components can be used to achieve multiple curvatures and large deflections ($>$120 degrees) under a magnetic wrench provided by an external mobile magnet module (EMMM) to adapt to the complex coronary environment. The variable-stiffness kinematics modeling, multivessel selection strategy, and preoperative surgical planning of the proposed magnetic robotic catheter are established. Meanwhile, an extracorporeal mobile ultrasound module (EMUM) is adopted to intraoperatively localize the catheter's in-plane motion with a dominant visual/force feedback controller. A hierarchical relative control scheme is proposed based on the relative Jacobian method to synchronize the motions of the multi-arm robot-assisted catheterization system. The overall performance is evaluated with anin vitrohuman-sized coronary arterial phantom with challenging anatomical variabilities. The results reveal that the HVS-MRC exhibits a high-accuracy intervention performance (average error of 1.52$ \pm$0.35 mm) with smoother steering compared with conventional catheters. High synchronization with a low ultrasound target loss rate (15.8%) and constant-force tracing (2.50$\pm$1.02 N) of the multi-arm robot-assisted catheterization system demonstrate promising application potential in radiation-free autonomous ultrasonographic coronary intervention operations.

As diverse robotic hands keep emerging for industrial and household use, designing general grasp synthesis algorithms applicable to multiple grippers remains challenging. To improve the generality and effectiveness of multigripper planar grasping algorithms, we propose a grasping framework featuring gripper-agnostic scene inference and gripper-changeable optimization. In our approach, we introduce an interaction probability map that bridges the scene inference and grasp optimization modules. It efficiently decouples the learning of grasping knowledge and modeling of gripper's kinematics. The inference module adopts a modified directional ensemble method with a generated fingertip dataset to refine scene information. In grasp optimization, we formulate gripper-kinematic constraints for different grippers according to joint types. Extensive evaluations on the Cornell Grasping Dataset (with a success rate of 95.51%) and on multifingered grippers (ten grippers in the real world) demonstrate that our hybrid approach generalizes learnable knowledge across various grippers. This work enables the direct transfer of learned grasping knowledge to new grippers in real-world applications.

This paper proposes the concept design of a novel XY compliant parallel manipulator (CPM) with spatial configuration, which is beneficial to promote the performance of the XY CPM. Evolved from a planar configuration, a spatial compliant parallelogram flexure is devised as the basic module structure. Then, a mirror-symmetric XY CPM adopting spatial layout is proposed based on four-prismatic-prismatic (4-PP) parallel mechanism. The prototypes are fabricated by 3D printing for testing. The performance analysis and verification is conducted through theoretical modeling, finite element simulation, and experimental study. For comparison study, a planar XY CPM with similar mechanism is also developed. Results show that the proposed XY CPM with spatial configuration provides the benefits of smaller plane footprint, large working stroke, and enhanced load-bearing capacity as compared to the planar one. It is appropriate for precise positioning scenarios, like soft-contact lithography, which require high loading capacity and great compactness.

Physical environment perception, modification, and measurement are challenging in constrained space at a small scale due to the lack of accessible sensors and related equipment. Here, we report a novel environmental learning strategy that utilizes microrobot swarms' responses to physical environments and interactions to detect useful details about surroundings, such as physical sizes and environmental viscosity. Inspired by natural collective behaviors, magnetic microparticle-based microrobots are organized into multiple cilia-like swarms. Under wireless magnetic actuation, these swarms demonstrate attractive performances in crowded and constrained spaces. By observing their responses to different surroundings, such as passing through different obstacles, it is feasible to obtain the detailed parameters of the obstacles and learn information on the surface, including slope angles and heights. Swarm pattern generation is also a great reflection of environmental viscosity. Detailed physical analysis and theoretical explanation are conducted to demonstrate the effectiveness. Several experiments are conducted to verify the proposed strategy. This work paves a valuable path to learning and modifying the environment and surroundings at a small scale.

This paper presents the design of a new multi-arm robotic system with mobile magnetic actuation and extracorpo-real ultrasound guidance dedicated to magnetic catheterization. The kinematic model of the external mobile actuation arm (EMAA) and extracorporeal ultrasound-integrated tracking arm (EUTA) are derived based on Denavit-Hartenberg (DH) parameters, including specially designed end-effectors. The synchronous control scheme for the mobile magnet and mobile ultrasound probe is introduced with polar coordinate-based magnetic actuation and visual servo-based ultrasound tracking method. Meanwhile, a denoising algorithm based on Speckle Reduction Anisotropic Diffusion (SRAD) is implemented. The effectiveness of the proposed robotic system has been verified by conducting several experimental studies, e.g., ex-vivo tests of catheter steering in endovascular phantom and soft tissue-imitating phantom with the average error of 0.32 mm and signal-to-noise-ratio (SNR) of 12.2 for the ultrasound imaging.

The flexure-based XYZ micropositioner with hybrid configuration has become more prevalent due to the characteristics of less mechanism decoupling and high motion precision. However, traditional mechanism design suffers from a large plane occupation with Z stage stacking, which leads to a low space-utilization efficiency. To address this issue, a novel conceptual design is proposed in this paper by integrating a spatially structured XY stage and an embedded Z stage together. After completing the design of the mechanism, the driving stiffness of the stage in three axes is evaluated by the mechanics analysis. Then, the model is verified by performing finite element analysis simulation study and experimental test. The theoretical model, simulation results, and experimental data indicate a good agreement. Experimental results show that the proposed flexure-based XYZ micropositioner can deliver a stroke of$\boldsymbol{4.15 \text{mm} \times 4.06 \text{mm} \times 0.04}$mm with a physical size of$\boldsymbol{116 \text{mm} \times 116 \text{mm} \times 45 \text{mm}. }$The performance comparison reveals that it has a superior space-utilization efficiency. In consideration of the feasibility of the proposed conceptual design, it provides a reference for diversified and refined design of XYZ micropositioners.

The COVID-19 pandemic shows growing demand of robots to replace humans for conducting multiple tasks including logistics, patient care, and disinfection in contaminated areas. In this paper, a new autonomous disinfection robot is proposed based on aerosolized hydrogen peroxide disinfection method. Its unique feature lies in that the autonomous navigation is planned by developing an atomization disinfection model and a target detection algorithm, which enables cost-effective, point-of-care, and full-coverage disinfection of the air and surface in indoor environment. A prototype robot has been fabricated for experimental study. The effectiveness of the proposed concept design for automated indoor environmental disinfection has been verified with air and surface quality monitoring provided by a qualified third-party testing agency. Note to Practitioners—Robots are desirable to reduce the risk of human infection of highly contagious virus. For such purpose, a novel autonomous disinfection robot is designed herein for automated disinfection of air and surface in indoor environment. The robot structure consists of a mobile carrier platform and an atomizer disinfection module. The disinfection modeling is conducted by using the measurement data provided by a custom-built PM sensor array. To achieve cost-effective and qualified disinfection, a full-coverage path planning scheme is proposed based on the established disinfection model. Moreover, for specifically disinfecting the frequently contacted objects (e.g., tables and chairs in offices and hospitals), a target perception algorithm is proposed to mark the localization of these objects in the map, which are disinfected by the robot more carefully in these marked areas. Experimental results indicate that the developed disinfection robot offers great effectiveness to fight against the COVID-19 pandemic.

In this paper, a dexterous bilateral robotic system with haptic feedback is designed and developed for microinjection of biological samples. For the first time, the robotic system has been developed for microinjection of both zebrafish larvae and embryos. The master device is constructed by a seven-degree-of-freedom (7-DOF) haptic interface. As the slave device, a 6-DOF microinjection robot is developed by integrating a 3-DOF micropositioning stage and a 3-DOF micromanipulator. One uniqueness of the proposed robotic system is that the injection targets can be placed directly in the Petri dish without prior pose adjustment. The master haptic device not only enables remote control of the microinjection robot by a human operator, but also provides an intuitive haptics feedback to the operator for executing the microinjection operation with a high success rate. The haptic interface is deployed as a viscous damping to enhance the smoothness and stability of its movement. Moreover, a hybrid bilateral control architecture is developed for the system to achieve ideal performance of position tracking and haptic telepresence. A prototype system is developed for performance test. The experimental results of individual and continuous microinjection of zebrafish larvae demonstrate fine position/force tracking capability and flexibility. Note to Practitioners—Microinjection is a universal operation in biological study for delivering foreign materials into biological samples. The existing manual and automated microinjections have limited flexibility. Meanwhile, the stand-alone visual information cannot provide enough telepresence to the operator, which results in low success rate and poor repeatability. This paper proposes a new haptics-based dexterous bilateral robotic system dedicated to microinjection task of both zebrafish larvae and embryos. Both the master haptic interface and slave microinjection robot exhibit multi-DOF motion, which enables a dexterous micromanipulation with high success rate for the human operator. The feasibility of the reported robotic system has been verified by performing microinjection operation of different targets.

In this paper, a new piezoelectric-actuated biaxial compliant microgripper with long strokes is proposed for automatically gripping and rolling tiny rigid objects. In order to improve the working stroke and maintain a compact footprint, a counter-side distributed two-stage lever amplifier with parallelogram mechanism is introduced. Based on the pseudo-rigid body model, analytical models of the displacement amplification ratio, input stiffness, and natural frequency of the left- and right-sided gripper mechanism are established. Structural optimization and performance simulation of the proposed microgripper mechanism are carried out with finite element analysis simulation. A prototype microgripper has been fabricated for open-loop and closed-loop tests to verify its working capabilities. The clamping and rubbing experiments show that the designed microgripper can grasp and rub an optical fiber with the diameter of 200$\mu \text{m}$for rolling over 45°. The developed microgripper has a promising application in precision micromanipulation fields such as optical fiber alignment. Note to Practitioners—This work is motivated by the requirement of designing a biaxial microgripper with both a large working stroke and compact structure for complex operation in optical fiber alignment. Through a series of open-loop and closed-loop experiments on the developed prototype, it is demonstrated that the proposed dual-axis microgripper has superior working performance. The clamping stroke and rubbing stroke of the gripper are$251.2~\mu \text{m}$and$225.0~\mu \text{m}$, respectively. The first two natural frequencies of the gripper are 350.63 Hz and 603.37 Hz, which correspond to the working modes of the right-side and left-side gripper mechanisms, respectively. The closed-loop experimental results show that the resolution of output displacement of the gripper is close to$1.2~\mu \text{m}$and the resolution of the clamping force is 3 mN. As compared with the reported microgrippers in previous work, the designed mechanism exhibits both a large working stroke and high resonant frequency for ensuring the reliability and rapidity of micromanipulation task.

This article proposes the concept design of a novel bio-inspired dual-axis compliant micromanipulator with millimeter working strokes dedicated to fiber alignment. It subtly mimics the gripping and rubbing function of human hand consisting of forefinger, purlicue, and thumb. As compared with traditional dual-axis gripper, its advantages lie in millimeter-level stroke, bidirectional rotation, less slippage, and comprehensive force sensing. To achieve dexterous and reliable manipulation, a two-degree of freedom flexible decoupling mechanism and a displacement reversing mechanism based on the leaf-shaped flexible hinge are introduced. Analytical models are derived to assess the statics and dynamics properties of the micromanipulator, which are verified by conducting finite-element analysis simulation study. A prototype driven by two voice coil motors is fabricated for experimental testing. Three high-precision strain gauges with temperature compensation are glued on the sensitive region to measure the gripping force and rubbing force. Experimental results show that the gripping stroke and rubbing stroke of the manipulator are up to 2.3 and 2.1 mm, respectively. For operating a custom-made fiber flag with a diameter of 200$\mu$m, a rotation stroke of more than 1000$^{\circ }$has been achieved, which cannot be realized by previous work with the same level of compact mechanism design.

This paper reports a new modular phalanx which possesses the capabilities of suction adhesion and adjustable stiffness for grasping tasks. The presented membrane-suction hole patterned layer can generate sufficient suction force to grasp objects with large radius of curvature and weight. Variable-stiffness of the phalanx tuned by granular jamming structure considerably enhances the grasping robustness and lifting force. Suction-lift capability and adjustable constrained stiffness are analytically modeled and experimentally validated by suction and constraint force tests on the fabricated prototype. Through various grasping demonstrations, the objects with a radius of 5 cm and thin plates are successfully suction-picked. The proposed soft phalanges are further integrated in articulated and parallel grippers to show their augmentation in motion sequence (picking thin object) and grasping stability (improving 1.35 times in lifting and preventing slip) over conventional grippers.

The microinjection of zebrafish larvae is a complicated work due to their small size and shape variations. In this article, for the first time, we design an automatic microinjection system dedicated to high-throughput injection of zebrafish larvae. The proposed custom-built microarray Petri dish combined with machine vision-based motion control enables high-efficiency automatic identification and injection of a batch of zebrafish larvae. The feasibility of the developed system is demonstrated by experimental testing on live zebrafish larvae. Results show that the developed system works fast with more stable injection success rate and higher survival rate than the skilled experimenter. The proposed system offers a good working efficiency and maintains a consistent success rate and stability in the process of high-throughput injection. It can be applied in various biomedical experiments based on zebrafish microinjection. Note to Practitioners—Zebrafish is widely used in biomedical experiments due to its obvious advantages. At present, the batch injection task of larvae is mainly conducted by experimenters manually. As the number of injections increases, experimenters will get tired, which makes it difficult for manual injection to maintain a stable success rate. This article reports the first automatic microinjection system for high-throughput batch injection of zebrafish larvae. A new microarray Petri dish has been proposed to fix the larvae, facilitating the microinjection process. Experimental results show that the system can complete a large number of injection tasks quickly while ensuring a stable success rate and survival rate of the larvae. It can free experimenters from repeated and tedious injection work. It also enables efficient zebrafish larvae microinjection for inexperienced experimenters.

High-performance and multi-function micromanipulator is favored by micromanipulation and microassembly systems. In this paper, a piezoelectric-actuated biaxial asymmetrical compliant micromanipulator is designed for gripping and rolling small targets. Parallel operation with large stroke is realized by the left and right sides of the micromanipulator with a well-designed multi-stage flexible amplifying mechanism. The pseudo-rigid-body model and the instantaneous center method are adopted to determine the displacement amplification ratio of the micromanipulator. The accuracy and applicability of the displacement amplification model are verified by conducting simulation studies with finite element analysis (FEA). It is shown that the clamping stroke and rubbing stroke of the micromanipulator are 357.94 μm and 245.48 μm, respectively. Furthermore, the stiffness, gripping force, and natural frequency of the micromanipulator are also evaluated by FEA simulations. The results demonstrate that the designed biaxial compliant micromanipulator has the ability of performing delicate and dexterous operations on small targets such as optical fiber.

This paper proposes the design of a new robot end-effector based on compliant constant-force mechanism for robot-assisted manufacturing, such as polishing. One uniqueness of the proposed end-effector lies in that it offers a constant contact force without using a force sensor and controller. An industrial robot is adopted to position the end-effector and the end-effector regulates the contact force passively. When the end-effector contacts the workpiece, the constant-force motion range acts as a buffer to counteract the excessive displacement caused by inertia. As a result, there is no force overshoot, protecting the consistency of the workpiece. The analytical model of the constant-force mechanism is deduced and the structural parameters are optimized to maximize the constant-force motion range under other constraints. For experimental testing, a prototype of the constant-force end-effector has been fabricated. The mechanism exhibits constant-force tendency with the force varying from 3.4 to 4.2 N between 0.7 and 1.7 mm. Experimental results verify the effectiveness of the presented constant-force end-effector mechanism.

The resonant controller (RC), as a promising candidate for high-speed nonraster nanopositioning applications, can track the sinusoidal reference with zero steady-state error. This article presents a controller composed of several RCs in parallel for tracking nonraster sequential scanning trajectories. The selection for each RC in the parallel array is based on two considerations: one is the spectrum of the reference signal and the other is the harmonics caused by the nonlinearities of the nanopositioning stage. The performance of RC is highly dependent on the accurate placement of the resonant poles, but unfortunately, many existing digital implementation methods could cause a deviation of the resonant poles from their initial locations. To address this problem, a modified Tustin (MTus) method is proposed in this article to implement the controller with better accuracy. Furthermore, the fractional-order (FO) calculus is introduced to improve the transient performance of the RCs. To validate the proposed methods, a comprehensive examination of several types of the nonraster sequential scanning trajectories with a wide frequency range has been carried out on a nanopositioning stage. The results have been compared with other methods, showing that the tracking errors are reduced significantly under the controller implemented by the MTus method especially in high-frequency conditions and that the application of the FO calculus reduces the settling time of the controller by more than 30% in most cases.Note to Practitioners—The demand for high-speed atomic force microscope (AFM) increases rapidly. However, the commonly used raster trajectory limits the achievable scan speed of the AFM. An effective way to improve the scanning and imaging speed of the AFM is the application of the sequential nonraster scanning methods. The trajectories of sequential nonraster scanning patterns mainly composed of few sinusoid signals with different frequencies. Therefore, the resonant controller (RC) is introduced in this article as it is capable to track the sinusoidal reference with zero steady-state error. Several RCs are selected first based on the spectrum analysis of the reference and the consideration of the harmonics caused by the system nonlinearities, and then, they are connected in parallel to form the controller for precise tracking of the reference. In order to realize the digital implementation of the designed controller, a modified Tustin discretization method is proposed, which ensures the accurate resonant pole placement of the RC and thus maintains the tracking performance of the RC. In addition, the fractional-order (FO) calculus is introduced to speed up the convergence of the designed controller while preserving the tracking accuracy, and this parallel-structure FO RC (PSFORC) design can be implemented to other systems that require high-speed and high-accuracy tracking of the periodic signals.

This paper presents the structure design and analysis of a novel bistable vibration energy harvester dedicated to direction of gravity. Its unique feature is that the bistability is realized by combining the elastic potential energy of the bridge compliant mechanism (BCM) and the gravitational potential energy of the proof mass. Therefore, its potential energy traps exhibit less inconsistency under the excitation with the direction of gravity. To evaluate the property of the proposed harvester, an analytical model is established. Parametric study is conducted to evaluate the influence of structural parameter. Static structural analysis is conducted to predict the actual performance of the proposed harvester, which is verified by conducting simulation studies.

Cell microinjection plays an important role in genetics, transgenics, and other biomedical fields. As compared with manual cell microinjection and position-based robotic cell microinjection, force-assisted robotic cell microinjection can improve the success rate and survival rate of the injected cells. In this paper, a novel force-sensing cell injector is designed with piezoresistive force sensor embedded in soft materials. The soft sensors act as fixed-guided beams, which are introduced to achieve the force measurement with high sensitivity in pure one-degree-of-freedom (1-DOF) direction. The injector is developed by considering the installation and replacement issues of the micropipette as well as the connection convenience between the micropipette and tube of compressed air. A prototype of the cell injector with the force sensor is fabricated. Experimental study is conducted to verify its performance in practice.

This paper presents the design, analysis and testing of a novel three-degree-of-freedom (3-DOF) compliant parallel-kinematic active constant-force stage. The active constant-force property enables a large travel and constant driving property, which is enabled by introducing symmetrical bistable flexure hinges. The folded flexure mechanism is adopted to guide the driving input and to balance the stiffness of the stage to zero. In addition, leaf flexure hinges are employed to decouple the cross-axis motion of the 3-DOF parallel stage. Analytical modeling is conducted to evaluate the stage performance. To verify the performance of the constant-force property and motion decoupling, finite-element analysis simulation study is carried out. By minimizing the fluctuation of the constant-force value, design optimization of the stage parameters is implemented with multi-objective genetic algorithm. Moreover, a prototype is fabricated for demonstration of the proposed concept design.

Cell injection plays an important role in genetics, transgenics, molecular biology, drug discovery, reproductive study, and other biomedical fields. Compared with manual cell microinjection and robotic cell microinjection with sole position feedback, force-assisted robotic cell microinjection can improve the success rate and survival rate of cell injection. In this paper, the state-of-the-art research on microinjection of both adherent cells and suspended cells with microforce sensing techniques is reviewed. The significance of force sensors in the robotic cell injection system is also discussed. Five types of prevalent force sensing methods and their applications in cell microinjection are reviewed. The challenges and promising solutions in automating the cell microinjection process are addressed. Note to Practitioners-Microinjection process is a complex task to perform. As the advance progress of high-performance microforce sensors, force-assisted robotic cell injection has been a hot topic in recent years. This paper presents the state-of-the-art survey of recent developments on microforce sensing for robotic cell microinjection to address the research challenges. Based on microforce sensing and control, microinjection of both adherent and suspended cells can benefit from the force-assisted robotic cell injection process. The main challenges and promising solutions in terms of micromanipulator design, injection control design, cell holder design, penetration scheme design, injecting pipette maintenance, injection volume, cost reduction, and microforce sensor calibration issues have been discussed. The related research trends are summarized.

This paper presents the design of a new compact one-degree-of-freedom (1-DOF) compliant stage driven by a piezoelectric actuator (PEA) for micro/nanopositioning in the vertical direction. An orthogonal compound bridge-type amplifier is introduced to amplify the displacement of the PEA. It significantly reduces the height of the stage and leads to a compact design. By analytical modeling of the mechanism, the design variables are determined, which are then optimized via the multiobjective genetic algorithm based on the finite-element analysis. Simulation results show that the 1-DOF stage is able to provide the maximum displacement of 181.18 μm in theory, which is more than 12 × the input displacement of PEA. Payload test results indicate that the stage can support a maximum load of about 80 N. Comparison study reveals that the presented vertical positioning stage offers a more compact structure than existing ones. A prototype is fabricated for experimental studies, and the deviation between the experimental and simulation results is discussed in detail. Moreover, closed-loop performance test exhibits a resolution of 10 nm for the developed vertical positioning stage.

This paper presents the design of a novel flexure-based precision positioning stage with constant output force for biological cell micromanipulation. One uniqueness of the proposed design is that it produces a constant force without using a force controller. Only a motion control is needed to produce a constant output force, which significantly simplifies the system design process. The stage is driven by a piezoelectric actuator through a displacement amplifier. Analytical models of the displacement amplifier and the zero-stiffness structure are established and verified by conducting finite-element analysis simulations. The structure parameters are optimally designed to guarantee the requirement on output force, motion range, and physical size. A prototype stage is fabricated by 3-D printing process and a series of experiments is carried out. Experimental results show that the developed positioning stage delivers a near constant output force with slight fluctuation in the reachable constant-force motion range of 138 μm. The applications of the developed constant-force stage in biological cell manipulation have been demonstrated through experimental investigations.

This paper reports on a novel 3D-printed polymeric compliant constant-force buffering gripping mechanism. The motivation of this work is to develop a buffering gripping mechanism to avoid the damage of manipulated biological object induced by excessive displacement output. The presented zero-stiffness mechanism is realized by connecting the negative-stiffness part and positive-stiffness part in parallel. The negative stiffness is obtained by a bistable buckled fixed-guided beam mechanism. Analytical modeling and simulation study are carried out before the prototype fabrication with 3D printing. Experimental results show that the proposed gripping mechanism can provide a constant output force of 780 mN in 500 μm motion range. Results also reveal that the manipulated object bears no deformation in the constant-force range, which is enabled as the excessive displacement output is buffered by the mechanism. The proposed design can be used to replace the existing combined force-displacement control strategy for fragile object manipulation.

This paper presents the design of a flexure-based precision positioning micro-motion stage system with constant output force. The stage mechanism is devised using folded leaf flexure (FLF) to achieve positive-stiffness structure. Bistable beams are employed to design negative-stiffness structure by using their buckling characteristics. Two bistable beams and two FLFs are combined together as a zero-stiffness structure. Complete models of the amplifier and the zero-stiffness structure are established and verified by using finite element analysis (FEA) simulation. The structural parameters are carefully designed to guarantee the performance requirement of motion range, stiffness and driving force. A prototype stage is fabricated by 3D printing process and a series of experiments are conducted for performance testing. Experimental results show that the developed positioning stage delivers a reachable constant-force motion range of 138 μm with good motion repeatability.

Limited travel constrains the widely application of XYZ parallel micro/nano-positioning stage. In this paper, a novel parallel-kinematics micro/nano-positioning stage is proposed with the goal of enlarging the travel range. In order to obtain a large input displacement for actuating the stage, voice coil motors (VCM) are adopted. For a large-travel parallel stage, the cross-axis motion increases the difficulty of closed-loop control process. Thus, the I-shaped flexure hinges are employed to decouple the parallel stage's motion. In view of the lower output force of the VCM, the guiding flexure mechanism is designed with an optimized sectional dimension of 140 mm × 44 mm. To verify the performance of the stage, analytical modeling and simulation study are conducted. Results show that the proposed large-travel parallel micro/nano-positioning stage owns the 3-DOF motion range of 3.527 mm, an oversize of 176 mm × 176 mm × 198 mm, and negligible isolation ratio of 0.0034%.

This paper presents the precision motion control of a piezoelectric nanopositioning stage using a new scheme of adaptive sliding mode control with uncertainty and disturbance estimation (ASMC-UDE). One uniqueness of the reported ASMC-UDE scheme is that an inherent chattering-free control action is guaranteed by eliminating the use of discontinuous control term. The reported ASMC-UDE strategy is easy to realize because the hysteresis effect is not needed to be modeled. Instead, the hysteresis is estimated and compensated by the robust control scheme. The control scheme is applicable to a system plant with either matched or unmatched disturbances. Unlike the existing UDE-based SMC control schemes, a reference model is not required by the proposed ASMC-UDE scheme. The stability of the chattering-free SMC strategy is proved in theory under the Lyapunov framework. The superiority of the presented control scheme over conventional approaches has been confirmed through comparative experimental studies. Moreover, the robustness of the controller in the presence of model disturbance and external disturbance has been verified.

This paper proposes a new compliant gripper with integrated position and force sensors dedicated to automated microassembly tasks. The uniqueness of the gripper is that it possesses a large gripping range with a bidirectional drive, and it is capable of detecting grasping force and environmental interaction forces in horizonal and vertical axes, respectively. This is enabled by a mechanism design based on a rotary flexure bearing. Moreover, a compliant mechanism with two-stage stiffness is designed to provide the force sensing with dual sensitivities and measuring ranges to accommodate the grasp of objects with different sizes and weights. Analytical models are derived to predict the grasping range, force sensing sensitivities, and ranges. These models are verified by conducting finite-element analysis simulations. A proof-of-concept prototype gripper is developed for experimental calibration and performance testing. Results reveal that the single set of strain-gauge force sensor is able to detect both grasping and interaction forces in an alternate manner. The dual-sensitivity, dual-range force sensor provides a solution to large-range gripper with finer and coarser force sensing in a small and large ranges, respectively .

In this paper, an autonomous cell injection system based on vision and motion control is proposed for automatic batch injection of suspended biological cells. A plate for accommodating cells is specifically designed to hold and fix the suspended cells. The plate is fixed in a two-axis compliant micropositioning stage to transport cells to pre-planed positions. The cells are located using image-based visual servoing control. The injector used for biological cell micro-injection is actuated by a piezoelectric actuator, which not only provides a largerange displacement but also offers a compact size. In order to guarantee the injection accuracy, a learning-based adaptive control scheme is implemented to fulfill the cell injection task. The eggs of salmon are adopted as injecting targets for demonstration in experimental investigation. Experimental results reveal the effectiveness of the proposed approach.

This paper presents the design of a compact flexure-based parallel-kinematics XY precision positioning stage with constant-force output. One uniqueness of the stage is that it can produce a constant output force without using a force controller. The stage mechanism is devised using leaf flexures to achieve decoupled structures with positive stiffness. Bistable beams are used as negative-stiffness structures. By combining two negative beams and four leaf flexures, a zero-stiffness mechanism is devised. Analytical model of the zero-stiffness structure is established and verified by carrying out finite-element simulation studies. Afterwards, the structure parameters are carefully designed to cater for the requirements on the range, stiffness, resonant frequency, and payload capabilities. The parametric design is verified by conducting finite-element analysis, which reveals a sufficient reachable constant-force motion rang about 700 μm in each working axis along with better performance in other aspects.

This paper proposes a new sensor deployment strategy based on quantitative cause-effect graph (QCEG) to handle the heterogeneity among the properties of sensors and faults. A QCEG is developed to model the cause-effect relationship between the system faults and sensor readings. A multi-objective optimization is performed to facilitate the monitoring of single-station multistep manufacturing process (SMMP). A stream of fault information model is built to describe the propagation of fault state in the SMMP. By means of state-space transformation, a detection factor is used to provide the initial sensor deployment. The optimal sensor deployment in an SMMP is achieved by an improved shuffled frog leaping algorithm (ISFLA), which minimizes the fault unobservability, maximizes the system stability, and minimizes the cost for the whole system, under the constraints on detectability, stationarity, and limited resources. Two experimental investigations on an assembly unit and a manufacturing unit are conducted to verify the methodology. Comparative studies demonstrate that the proposed QCEG is able to overcome the shortcomings of directed graph (DG) in handling sensor heterogeneity and multiple objectives. As a goal-oriented swarm-intelligence search strategy, the ISFLA performs better than the popular integer programming in dealing with the multi-objective optimization problem.

This study proposes a hybrid model for evaluating surface roughness in hard turning using a Bayesian inference-based hidden Markov model and least squares support vector machine (HMM-SVM). The model inputs are multidirectional fusion features that are extracted from the acquired monitoring signals through independent component analysis and singular spectrum analysis. Based on a detailed analysis of the workpiece surface formation mechanism, the cutting vibration signals are determined as monitoring signals and an experimental scheme based on the multifeed rate is designed. The error rate of HMM-SVM is further reduced by introducing the stratification factor comparison method rather than using the conventional probability comparison method. A five-step iterative algorithm is presented to select and optimize the training set, which effectively solves the problems of precision degradation and training data insufficiency. Experimental studies show that the proposed model can accurately predict the surface roughness in case of missing samples. The advantages of the proposed model over least squares support vector machine (LSSVM) and multiple regression approaches are demonstrated via statistical analysis. Note to Practitioners-As an alternative to traditional grinding, hard turning is an attractive machining method, in which surface quality is a crucial measurement index. However, under the scenario of sample missing, a straightforward and relatively accurate model for predicting surface roughness is challenging to establish using conventional strategies. This paper reports on a new HMM-SVM model based on Bayesian inference for modeling and predicting surface roughness in hard turning. The samples are classified based on the accuracy grade of surface roughness according to the GB/T1031-2009 standard using the expectation maximization algorithm and HMM, which is superior in small-sample classification problem. LSSVM is employed to estimate surface roughness. The effectiveness of the proposed model is demonstrated through experimental investigations. The reported methodology can also be extended to other related fields.

This paper presents the design, analysis, and testing of a novel dual-range, dual-resolution XY micropositioning stage driven by a single actuator in each axis. As compared with dual-servo stages, it allows the reduction on the cost of both hardware and control design workload. The compliant stage is devised using leaf springs to achieve a large stroke. Strain sensors are employed to provide coarse and fine resolutions in the larger and smaller motion ranges, respectively. Analytical models are developed to facilitate the quantitative design of the motion ranges and coarse/fine resolution ratio. The motor selection criteria in terms of driving force and stroke are addressed as well. The models are verified through simulations with finite element analysis. A proof-of-concept prototype is fabricated for experimental investigations. The feasibility of the proposed idea is validated by a collection of experimental studies.

Automated microhandling tasks demand miniature grippers equipped with position and force sensors to execute reliable operations. This paper presents the design, implementation, and control of a piezoelectrically actuated compliant gripper with combined position and force monitoring/control capabilities. The gripper structure is devised based on a compliant rotary bearing mechanism with the displacement amplification lever, which endows a simplified architecture than the existing parallelogram-based ones. Moreover, the challenge of achieving a smooth transition between the position and force switching control is addressed by means of a new incremental control scheme. Precision control under the influence of hysteretic nonlinearity is guaranteed by a discrete sliding-mode control algorithm. The scheme is implemented with an field-programmable gate array (FPGA) platform. Experimental investigations are undertaken to verify the effectiveness of the gripper system by executing grasp-hold-release operations of a micro copper wire. The results confirm that the proposed incremental-based switching control outperforms conventional approach in terms of position/force regulation accuracy and operation time.

This paper presents the design, fabrication, and testing of a compliant rotary nanopositioning stage for precision engineering applications. The major advantage of the rotary stage lies in that it possesses a large rotational range and a compact size simultaneously. A new idea of compound radial flexure is proposed to enable this merit. A novel rotary stage is designed to provide a rotary angle over 10° while delivering a negligible magnitude of center shift. In the design procedure, analytical models are established for the performance evaluation of the stage, which are validated by finite element analysis (FEA). A prototype stage of 10-cm diameter is fabricated by wire-electrical discharge machining (EDM) process for experimental tests. The stage is driven by a voice coil motor and its output motion is measured by laser displacement sensors. Both FEA and experimental results confirm the large rotational range and low level of center shift of the rotary nanopositioning system. The proposed idea can be extended to the design of other precision positioning systems with rotary motion.

Precision position and force control is a critical issue for automated microassembly systems to handle micro-objects delicately. This paper presents two new approaches to regulating both position and contact force of a piezoelectric multimorph microgripper dedicated to microassembly tasks. One of the advantages of the proposed approaches lies in that they are capable of controlling the position and contact force of a gripper arm simultaneously. The methodology is easy to implement since neither a state observer nor a hysteresis model of the system is required. The first approach is a position-based sliding mode impedance control which converts the target impedance into a desired position trajectory to be tracked, and the second one is established on the basis of a proportional-integral type of sliding function of the impedance measure error. Their tracking performances are guaranteed by two devised discrete-time sliding mode control algorithms, whose stabilities in the presence of model uncertainties and disturbances are proved in theory. The effectiveness of both schemes are validated by experimental investigations on a glass microbead gripping task. Results show that both approaches are capable of accomplishing promising interaction control accuracy.

Delicate interaction control is a crucial issue for automated microsystems dedicated to microobjects handling. This paper proposes a new approach to regulate both position and contact force of a piezoelectric-bimorph microgripper for micromanipulation and microassembly applications. The methodology is developed based on the framework of a discrete-time sliding mode generalized impedance control with adaptive switching gain. One unique feature lies in its easy implementation based on a second-order dynamic model, whereas neither a state observer nor a hysteresis/creep model of the system is required. The stability of the control system is proved in theory, which ensures the tracking performance in the presence of model uncertainties and disturbances. The effectiveness of the scheme is validated by experimental investigations on grasp operation of a microgear. Results show that the approach is capable of accomplishing precision position/force control simultaneously. Moreover, the influences of control gains and target impedance parameters on the tracking performance are addressed, and the achievement of balance between the position and force control accuracy is discussed.

A micro-/nanopositioning system with both large motion range and compact size is highly desired in various precision engineering applications. In this paper, the design of a new compliant micropositioning stage with translational motion is proposed based on flexure mechanisms. The stage parameters are optimized by using the genetic algorithm (GA) to achieve a large natural frequency under the constraints on motion range (i.e., over 10 mm) and compact physical dimension along with a high safety factor for the material. Both analytical calculations and simulations based on finite element analysis are performed to validate the stage performances. A physical prototype system which employs a voice coil motor and a laser displacement sensor for actuation and sensing, respectively, is fabricated for experimental tests. Result confirms the long-stroke performance of the developed micropositioning system.

Dual-servo systems (DSSs) are highly desirable in micro-/nanomanipulation when high positioning accuracy, long stroke motion, and high servo bandwidth are required simultaneously. This paper presents the design and development of a new flexure-based dual-stage nanopositioning system. A coarse voice coil motor (VCM) and a fine piezoelectric stack actuator (PSA) are adopted to provide long stroke and quick response, respectively. A new decoupling design is carried out to minimize the interference behavior between the coarse and fine stages by taking into account actuation schemes as well as guiding mechanism implementations. Both analytical results and finite-element model (FEM) results show that the system is capable of over 10 mm traveling, while possessing a compact structure. To verify the decoupling property, a single-input-single-output (SISO) control scheme is realized on a prototype to demonstrate the performance of the DSS without considering the interference behavior. Experimental results not only confirm the superiority of the dual-servo stage over the standalone coarse stage but reveal the effectiveness of the proposed idea of decoupling design.

Flexure-based micropositioning systems with a large workspace are attractive for a variety of precision engineering applications. In this paper, a new idea of multistage compound parallelogram flexure is proposed for the mechanism design of a novel parallel-kinematic XY micropositioning system, which has a motion range larger than 10 mm along with a compact structure. The established quantitative models and the stage performances are validated by conducting finite-element analysis (FEA) and experimental studies. Moreover, an enhanced model-predictive control (EMPC) is presented for positioning control of the system, which has a nonminimum-phase plant. It is shown that the EMPC is capable of producing a low magnitude of output tracking error by imposing an appropriate suppression on the control effort. Simulation and experimental studies reveal that the EMPC scheme outperforms the conventional proportional-integral-derivative (PID) and MPC methods in terms of transient response speed and steady-state accuracy. The idea that is presented in this paper is extendable to design and control of other micro-/nanopositioning systems with either minimum- or nonminimum-phase plants.

Piezoelectric hysteresis usually relies on the frequency of the input signal. Most of the existing rate-dependent models use a lot of parameters to capture the rate-dependent hysteresis. In this paper, a simple rate-dependent hysteresis model is proposed to describe the frequency dependency effect of a micropositioning stage driven by piezoelectric actuators. This model is extended from an enhanced Coleman-Hodgdon (C-H) model. It has only 9 parameters and exhibits an accuracy better than 97%. The dependencies of the model parameters on the input rate are derived based on open-loop experimental tests. As inverse rate-dependent C-H model is established to construct a feedforward compensation. Experimental results demonstrate the effectiveness of the rate-dependent model over the traditional rate-independent one. The feedforward in conjunction with a PID feedback control is constructed to further attenuate the modeling errors and creep effects. Results show that the combined control scheme suppresses the tracking error by more than 8 times compared to the stand-alone PID control. It provides a sound base of practical control of the micropositioning system for micro/nano scale manipulation.

This paper reports the design and development processes of a totally decoupled flexure-based XYZ parallel-kinematics micropositioning stage with piezoelectric actuation. The uniqueness of the proposed XYZ stage lies in that it possesses both input and output decoupling properties with integrated displacement amplifiers. The input decoupling is realized by actuation isolation using double compound parallelogram flexures with large transverse stiffness, and the output decoupling is implemented by employing two-dimensional (2-D) compound parallelogram flexures. By simplifying each flexure hinge as a two-degree-of-freedom (2-DOF) compliant joint, analytical models of kinematics, statics, and dynamics of the XYZ stage are established and then validated with finite-element analysis (FEA). The derived models are further adopted for optimal design of the stage through particle swarm optimization (PSO), and a prototype of XYZ stage is fabricated for performance tests. The nonsymmetric hysteresis behavior of the piezo-stage is identified with the modified Prandtl-Ishlinskii (MPI) model, and a control scheme combining the inverse model-based feedforward with feedback control is constructed to compensate the plant nonlinearity and uncertainty. Experimental results reveal that a submicron accuracy 1-D and 3-D positioning can be achieved by the system, which confirms the effectiveness of the proposed mechanism and controller design as well.

This paper presents the design and fabrication process of a new piezoelectrically actuated flexure-based XYZ compliant parallel-kinematics micropositioning stage with totally decoupled properties. The proposed XYZ stage consists of three limbs which are assembled in an orthogonal manner, and it has both input and output decoupling properties. Analytical models for kinematics, statics, and dynamics of the XYZ stage are established, which are validated by finite element analysis performed with ANSYS. Based on the derived models, architectural parameters of the stage are optimized and a prototype is developed for experimental studies. The results not only verify the effectiveness of the conducted optimum design but also confirm the well-decoupled performance of the XYZ stage, which will be used to execute micro-/nanomanipulation tasks.

In this paper, a global sliding mode control (GSMC) scheme is implemented on a piezo-driven XY parallel micropositioning stage to compensate for the unmodeled hysteresis aiming at a sub-micron accuracy motion tracking control. The GSMC controller is designed with the consideration of all uncertainty bounds. In the controller implementation, a high-gain velocity observer is adopted to estimate the feedback velocity from the measured position. The effectiveness of the GSMC over ordinary SMC and traditional PID control is demonstrated through simulations, while the variations of design parameters on control performances are examined as well. Results show that the GSMC can reduce the hysteresis to a negligible level and lead to a sub-micron accuracy tracking with tolerance to some degrees of external disturbances, which provides a sound base of practical control of the micropositioning system for micro/nano scale manipulation.

This paper presents a complete design and development procedure of a new XY micromanipulator for two-dimensional (2-D) micromanipulation applications. The manipulator possesses both a nearly decoupled motion and a simple structure, which is featured with parallel-kinematic architecture, flexure hinge-based joints, and piezoelectric actuation. Based on pseudo-rigid-body (PRB) simplification approach, the mathematical models predicting kinematics, statics, and dynamics of the XY stage have been obtained, which are verified by the finite-element analysis (FEA) and then integrated into dimension optimization via the particle swarm optimization (PSO) method. Moreover, a prototype of the micromanipulator is fabricated and calibrated using a microscope vision system, and visual servo control employing a modified PD controller is implemented for the accuracy improvement. The experiments discover that a workspace size of 260 mum times 260 mum with a 2-D positioning accuracy and repeatability around 0.73 and 1.02 mum, respectively, can be achieved by the micromanipulator.

In this paper, a concept of totally decoupling is proposed for the design of a flexure parallel micromanipulator with both input and output decoupling. Based on flexure hinges, the design procedure for an XY totally decoupled parallel stage (TDPS) is presented, which is featured with decoupled actuation and decoupled output motion as well. By employing (double) compound parallelogram flexures and a compact displacement amplifier, a class of novel XY TDPS with simple and symmetric structures are enumerated, and one example is chosen for further analysis. The kinematic and dynamic modeling of the manipulator are conducted by resorting to compliance and stiffness analysis based on the matrix method, which are validated by finite-element analysis (FEA). In view of predefined performance constraints, the dimension optimization is carried out by means of particle swarm optimization, and a prototype of the optimized stage is fabricated for performance tests. Both FEA and experimental studies well validate the decoupling property of the XY stage that is expected to be adopted into micro-/nanoscale manipulations.

This paper presents the design and development procedures of a new decoupled XY micromanipulator for micro scale positioning applications. The manipulator is featured with parallel-kinematic architecture, flexure hinge-based joints, and piezoelectric actuation. Based on the lumped model, the efficient models for kinematics, statics and dynamics of the XY stage have been obtained, which are verified by resorting to the finite element analysis via ANSYS software package. Moreover, the stage dimensions are optimized through the particle swarm optimization (PSO) approach, and a manipulator with performances satisfying the requirements is generated. Furthermore, a prototype of the manipulator has been fabricated via the wire-EDM process. The developed micromanipulator is expected to be adopted in practical applications.

The design procedure for a totally decoupled XY flexure parallel kinematic manipulator is presented in this paper. The designed XY stage is featured with flexure hinges and a relatively simple structure. The output decoupling is allowed by the employment of compound parallelogram flexure, and the input decoupling is implemented by actuation isolation which is enabled by the double compound parallelogram flexure with large transverse stiffness. An improved displacement amplifier is adopted to amplify the stroke of linear actuator and to simplify the stage architecture. Kinematic models of both the amplifier and the XY stage are conducted by resorting to compliance analysis based on matrix method, which are validated by finite element analysis performed with ANSYS. The presented results are helpful for the design of a new XY flexure parallel manipulator for micro/nano scale manipulation.

A novel design of a mobile parallel manipulator (MPM), which is composed by a multi-degree of freedom (DOF) parallel robot and an autonomous wheeled mobile platform, is proposed in this paper to overcome the shortcomings of the parallel robot and perform high accuracy tasks. Both the position and differential kinematics problems for the hybrid system are solved in details, and the dynamic model for the MPM is derived via Lagrangian formulation approach with simplifying hypotheses. Furthermore, taking the MPM self motion into consideration due to its redundancy, the dynamic control in task space is implemented by employing a model-based controller. Simulation results illustrate that not only the control algorithms are effective well, but also the established dynamic models are accurate enough as well

The stiffness modeling for a compliant parallel manipulator (CPM) is very important since it provides a basis for the characterization of static, modal, and dynamic behavior of the CPM. This paper presents the stiffness modeling of a three-prismatic-revolute-cylindrical (3-PRC) CPM with orthogonally mounted actuators, that is designed to provide three spatial translational DOF for nano scale manipulation. A straightforward method is developed to establish the analytical stiffness model for a spatial CPM by considering the compliance of each compliant element, which is then applied to stiffness modeling of the 3-PRC CPM. Furthermore, the finite element analysis is carried out to validate the developed model. And to demonstrate the utility of the stiffness model, the influence of architectural parameters on stiffness factors is analyzed, which is valuable for a cost-effective design of the CPM

A new 2-degrees of freedom compliant parallel micromanipulator (CPM) utilizing flexure joints is proposed for two-dimensional nanomanipulation in this paper. By a proper selection of actuators, flexure hinges, and materials, this system is constructed and analyzed by a pseudorigid-body model, architectural optimization, and finite-element analysis. Both the position and velocity kinematic modelings are established, and afterwards, statics analysis is performed. In view of the physical constraints imposed by pizeo-actuators and flexure hinges, the CPM's workspace area is determined. And in order to achieve a maximum workspace subjected to the given dexterity indices, kinematic optimization of the design parameters is carried out, which results in a manipulator satisfying the operational requirements. Furthermore, the finite-element analysis has been undertaken to validate the analytical modeling, and the influence of architectural parameters on CPM performance has been evaluated as well. Note to Practitioners-This paper is motivated by the problem of designing a nanomanipulator for two-dimensional (2-D) assembly of nanoscale objects via nanomanipulation. A novel planar parallel mechanism incorporating compliant mechanisms is designed for such a purpose. Since the application of the manipulator depends significantly on the kinematic mathematical models, the designed compliant parallel micromanipulator (CPM) is analyzed by the established pseudorigid-body (PRB) model. The architectural optimization leads to a CPM satisfying the workspace and resolution requirements of this work. Moreover, finite-element analysis is performed to verify the accuracy of the developed PRB model, and simulation results illustrate the efficiency of the PRB model in designing and analyzing the CPM. Since the designed CPM is composed solely of flexural elements which are known to be competent in high precise applications, it is reasonable to expect that the CPM could find its way into 2-D manipulation of nanoscale components.

A new three degrees of freedom translational parallel manipulator (TPM) with fixed actuators, called a general 3-PRC TPM, is proposed in this paper. The mobility of the manipulator is analyzed via screw theory. The inverse kinematics, forward kinematics, and velocity analysis are performed and the singularity problems are investigated afterwards, which can be applied to a general 3-PRC TPM regardless of actuators arrangement. With the variation on actuators layout angle, the reachable workspace of the manipulator is generated and compared. Especially, it is illustrated that the manipulator in principle possesses a uniform workspace with a constant hexagon shape cross section. Furthermore, the dexterity characteristics is investigated in the global sense. Simulation results show that different specific tasks should be considered when the actuators layout angles of a general 3-PRC TPM are designed.

The concept of a medical robot constructed by parallel mechanisms for chest compressions in rescuing a patient is proposed in this paper. In light of the requirements of cardiopulmonary resuscitation (CPR) from medical aspects, a new translational parallel manipulator (TPM) employing the architecture of a modified version of DELTA parallel robot is designed, which utilizes an architectural optimization methodology for such applications. The mobility and velocity analysis of the manipulator is carried out in details. By introducing a simplifying hypothesis, the inverse dynamic modeling is performed based upon the principle of virtual work. Moreover, the dynamic control using computed torque method is implemented, and simulation results illustrate the well performance of the control algorithm. The research works lay a sound foundation on developing a medical robot prototype to assist in CPR operation.