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This paper presents an adaptive probabilistic recurrent Takagi-Sugeno-Kang fuzzy neural PID controller for handling the problems of uncertainties in nonlinear systems. The proposed controller combines probabilistic processing with a Takagi-Sugeno-Kang fuzzy neural system to proficiently address stochastic uncertainties in controlled systems. The stability of the controlled system is ensured through the utilization of Lyapunov function to adjust the controller parameters. By tuning the probability parameters of the controller design, an additional level of control is achieved, leading to enhance the controller performance. Furthermore, it can operate without relying on the system's mathematical model. The proposed control approach is employed in nonlinear dynamical plants and compared to other existing controllers to validate its applicability in engineering domains. Simulation and experimental investigations demonstrate that the proposed controller surpasses alternative controllers in effectively managing external disturbances, random noise, and a broad spectrum of system uncertainties. • We propose an adaptive probabilistic recurrent TSK fuzzy neural PID controller. • The Lyapunov stability criterion is used to update the proposed controller parameters. • The proposed controller is applied practically for controlling a servo motor. [ABSTRACT FROM AUTHOR]

The reliability of sensors and servos is paramount in diagnosing the Heavy-Legged Robot (HLR). Servo faults stemming from mechanical wear, environmental disturbances, or electrical issues pose significant challenges to traditional diagnostic methods, which rely heavily on delicate sensors. This study introduces a framework that solely relies on joint position and permanent magnet synchronous motor (PMSM) information to mitigate dependency on fragile sensors for servo-fault diagnosis. An essential contribution involves refining a model that directly connects PMSM currents to HLR motion. Moreover, to address scenarios where actual servo outputs and HLR cylinder velocities are unavailable, an improved sliding mode observer (ISMO) is proposed. Additionally, a Fourier expansion model characterizes the relationship between operation time and fault-free disturbance in the HLR. Subsequently, the dual-line particle filter (DPF) algorithm is employed to predict fault-free disturbance. The outputs of DPF serve as a feedforward to the ISMO, enabling the real-time servo torque fault diagnosis. The accuracy and validity of this technical framework are verified through various simulations in MATLAB/SIMSCAPE and real-world experiments. • A refined model is constructed to address the unknown outputs of the robot servo. • The cylinder velocities are observed in the presence of uncertainties and faults. • The fault-free disturbance is characterized by a Fourier expansion model. • The dual-line particle filter (DPF) compensates for the fault-free disturbance. [ABSTRACT FROM AUTHOR]

Diamond turning of microstructured surfaces based on slow slide servo or fast tool servo technologies suffers from either low machining efficiency or low surface accuracy, due to the highly mixed low-frequency and high-frequency tool trajectory. This work proposes a new parallel tool servo (PTS) turning technology, in which the original tool path is filtered according to an optimal cut-off frequency and then decomposed into independent trajectories separately for a slow slide and a fast stage in parallel. This approach is experimentally validated and compared with existing single-mode servo technologies, with significantly enhanced cutting performance, thus offering a novel perspective for ultra-precision machining. [ABSTRACT FROM AUTHOR]

Increasing the observer bandwidth of the extended state observer (ESO) can significantly enhance the disturbance rejection performance of the active disturbance rejection control (ADRC). However, a large observer bandwidth can also amplify the noise and degrade the control quality. This study proposes a novel fractional-order ADRC (FOADRC) approach. A fractional-order model-aided extended state observer (FOMESO) is designed by leveraging available plant information. Under a given observer bandwidth, the disturbance estimation performance of FOMESO is improved, while noise sensitivity is not aggravated. Additionally, FOMESO transforms a typical second-order plant into a fractional-order double-integrator model, reducing the phase lag to below 180 ∘. Consequently, the derivative component, which is sensitive to noise, is unnecessary in the feedback controller. Simulation and comprehensive comparisons demonstrate that the proposed FOADRC scheme outperforms the traditional ADRC in tracking, noise sensitivity, disturbance rejection, and stability. Furthermore, the proposed FOADRC approach is robust to plant parameter variations. The proposed method is validated through experiments on a permanent magnet synchronous motor speed servo system, confirming its superiority and effectiveness. • An optimization method using plant information is used to design the fractional-order model-aided extended state observer (FOMESO). • The second-order plant is transformed into a cascade fractional integrators model by FOMESO. • A fractional-order active disturbance rejection control is proposed consisting of a proportional feedback controller and FOMESO. • The proposed method has superior disturbance rejection, stability, robustness, and noise suppression performance. [ABSTRACT FROM AUTHOR]

The ball screw feed system of CNC machine tools is a typical mechatronic motion mechanism. During the operation of the machine tool, not only the dynamic characteristics of the mechanical structure will affect its performance, but also the electrical characteristics of the servo system will affect the movement of the worktable, which will lead to displacement fluctuation and bring adverse effects on the precision of the machine tool and even the quality of the processed parts. Therefore, the electrical system and the mechanical system are strongly coupled to each other due to their high integration. In this paper, the fluctuation of current, torque, and displacement during the motion of the worktable is studied. Firstly, the mechatronic model of the ball screw feed system, which not only consists of all components of the feed system but also takes different nonideal characteristics of each component into consideration, is established to realize the physical simulation of the whole system. Then, with the consideration of the impacts of inverter dead zone, motor cogging torque, rotor mixed-eccentricity, winding asymmetry, and collecting error of feedback current, the frequency components of fluctuations caused by the nonlinear electrical characteristics of inverter and servo motor in the servo drive system are obtained. Finally, the influences of load, feedrate, servo parameters, and dynamic characteristics of mechanical structure on fluctuation are analyzed in the time domain and frequency domain. The phenomenon of displacement fluctuation of the worktable caused by the electrical characteristics of the servo system indicates that it is necessary and meaningful to build the integrated model to study the ball screw feed system from the view of the whole system. • Ball screw feed system integrated model including control system, inverter, motor, mechanical system. • Physical simulation of feed system considering nonlinear electrical characteristics of servo system. • Feed system fluctuation due to nonlinear electrical characteristics of servo system is studied. • Low frequency components of servo system harmonics can pass through mechanical system. • Analysis of impact of load, feedrate, servo parameter, mechanical system dynamic characteristics on fluctuation. [ABSTRACT FROM AUTHOR]

Performance evaluation (PE) is an important part of equipment health management. If the monitoring information of the equipment is interfered, the evaluation results may be erroneous. A robust performance evaluation (RPE) method is proposed to solve this problem. The performance evaluation results are obtained by distinguishing the cases of single evidence with interference and two evidence with interference, and a robustness measurement based on interval similarity is proposed. To improve the accuracy of the evaluation results, the referential values in the IER evaluation model are optimized. The robustness thresholds of the input indexes are obtained under the satisfaction of the robustness constraints. If the interference value of the input index is within the thresholds, the deviation between the evaluation results using monitoring information with interference and those using monitoring information without interference is small. Finally, the proposed method is applied to a type of electric servo mechanism performance evaluation, and the case shows the validity of the RPE method. • Proposed a robustness measurement method based on interval similarity. • Analyzed the robustness of performance evaluation method based on IER approach. • Determined the robustness threshold of the input indexes under robustness constraint. [ABSTRACT FROM AUTHOR]

Every homeowner wants maximum security for their home from various disturbances and threats. Many homeowners have installed a surveillance camera (CCTV) as their home security system. Apart from its relatively high price, the security camera system has weaknesses, which are difficult to integrate with stable and secure user devices in real-time. This research proposes a security system that integrates the Internet of Things (IoT) with the Arduino Uno microcontroller, PIR, and Ultrasonic sensors. The two sensors are used as scouts connected to a servo motor, an automatic locking device. The proposed system can be utilized as a safe and relatively inexpensive preventive measure. [ABSTRACT FROM AUTHOR]

In this article, the problem of high precision motion control for motor servo systems with modeling uncertainties and unknown actuator backlash is addressed. The combination of synthesized adaptive laws and continuous nonlinear robust term handles parameter uncertainties and system disturbances. The adaptive technique updates the unknown parameters of actuator backlash in real time and the backlash inverse function eliminates the backlash effect. Meanwhile, the designed controller without knowing the range of the disturbance upper bound but automatically estimates through the adaptive law, which improves the engineering practicability. Finally, the theoretical analysis proves the perfect asymptotic stability of the presented controller even with unmodeled disturbances and unknown actuator backlash. Extensive comparative experiments reveal the superiority of the presented method. • A nonlinear robust adaptive controller is proposed for motor servo system with unknown actuator backlash. • The unknown upper bound of unmodeled disturbances can be updated by adaptive laws online. • Excellent asymptotic output tracking performance is achieved with the proposed controller. • The effectiveness of the proposed controller is verified by comparative experimental results. [ABSTRACT FROM AUTHOR]

The performance of a typical string-connected Photovoltaic (PV) panels will be adversely affected even if only one of its panels is partially shaded. Therefore, the monitoring of these panels becomes crucial to ensure reliable operation of the whole PV plant. In this paper, a low-cost solution for real-time monitoring and diagnosis of PV plants is proposed. In fact, our approach is based on the use of pre-trained AlexNet Convolutional Neural Network (CNN) to predict whether a given panel is under partial shading conditions (PSC) or not, by extracting features from two-dimensional (2-D) scalograms generated in real-time from PV data acquisition system. It should be noted that, in addition to a disconnection circuit and a servo motor mounted on it, each panel of the proposed system is equipped with four sensors namely: voltage, current, temperature and irradiance sensor. All these components are connected to Adafruit PyBadge microcontroller unit (MCU). In fact, a Continuous Wavelet Transform was applied to the time series data provided by these sensors to generate the 2-D scalograms. On the hand, we performed transfer learning by fine-tuning the last fully connected layer of the pre-trained AlexNet CNN and modifying its architecture to get only two neurons which represent our two classes (i.e., PV panel under PSC or not). The model, achieving a high fault detection accuracy of 98.05%, was built in Keras framework with TensorFlow where only the parameters of the last fully connected layer of the pre-trained AlexNet CNN are retrained. Afterward, this model was converted into TensorFlow Lite format and successfully implemented on PyBadge MCU. Several experiments were carried out in this work have shown that, our monitoring system allows not only the automatic disconnection of the partial shaded PV panels, to avoid thermal issues under bypass conditions, but also removing undesired objects accumulated on their surface by actioning the corresponding servo motor, in order to restore in real-time the normal operation of the whole PV system. [ABSTRACT FROM AUTHOR]

This study investigates the spatial pointing control of a motor-mechanism coupling tank gun. The tank gun control system (TGCS) is driven and stabilised by the motor servo system. However, complicated nonlinearities in the TGCS are inevitable, such as friction, parameter uncertainty, and modelling errors. To solve this problem, the TGCS is regarded as a coupling system composed of mechanical, motor, and control systems. Accordingly, the mechanical and motor models of the marching tank gun are developed first in this paper. The motor-mechanism coupling dynamics model is established based on the principle of equivalent torque. On this basis, a computed torque controller, whose uncertainty was estimated using a radial basis function neural network (RBFNN), is constructed. A modified adaptive algorithm is used to estimate the weights of the RBFNN, and the estimation error of the uncertain observer is compensated by a compensation controller. Simulation results under different conditions validated the effectiveness of the proposed control system, revealing that the proposed control system has good tracking accuracy, strong adaptability, and robustness. • A 2-DOF nonlinear dynamics model of the yaw body and pitch body was established considering the 6-DOF motion of tank chassis. • The motor-mechanism coupling dynamics model was built. • A computed torque controller with RBFNN was designed. A compensation controller was adopted to compensate for the minimum approximation error. • The modified adaptive law was designed to ensure that the tracking error converges to zero. • Simulation results under different conditions validate the effectiveness of the proposed control system. [ABSTRACT FROM AUTHOR]

Kaplan turbines are nowadays used to provide Frequency Containment Reserve (FCR) to the grid due to their fast capacity to regulate their power maintaining high efficiency. However, this continuous power regulation increases the wear and tear of the regulation system considerably. To reduce the amount of movements in the regulation servomotors, and thus their wear and tear, a new technology is being investigated within the frame of the European project XFLEX Hydro. This new technology is based on hybridizing the hydro unit with a small size battery in parallel, this one being in charge of compensating the small frequency fluctuations in the grid by providing or absorbing power. In this paper, the benefits of the implementation of this new technology are evaluated. A Kaplan turbine prototype located in Vogelgrun, France, has been hybridized and different parameters have been monitored while the unit was working in hybrid mode and in normal standalone hydro mode. Wear and tear of the regulation system have been compared for both hybrid and standalone hydro modes. A reduction of about 25% in servomotors mileage and of 50% in fatigue damage have been obtained by hybridizing the unit. • Benefits of hybridizing hydro units with a battery are studied. • A small size battery is installed in parallel with a prototype Kaplan unit. • The battery helps to provide primary frequency control reducing the wear and tear of the hydro unit. • A reduction of wear and tear in the hydro unit regulating systems is obtained. [ABSTRACT FROM AUTHOR]

Recently, the application of low frequency vibration has been attempted in the turning process. The tool is vibrated in the feed direction by numerical control to break up long continuous chips that adversely affect the surface quality and tool wear, etc., by generating a duration of cutting edge leaving workpiece. In order to achieve higher machining efficiency in vibration cutting, however, it is necessary to focus on chatter stability. When chattering occurs, a higher frequency chatter vibration is superimposed on the low-frequency tool vibration caused by the feed motion of the servo drive. However, the chatter amplitude decreases due to system damping, because the cutting force does not act in the air-cutting section of vibration cutting. In addition, tool displacement is regenerated not only before one spindle rotation, but also before two or more rotations in vibration cutting. Therefore, the application of low frequency vibration has an important influence on the chatter stability. The purpose of this study is to reveal the detailed effects of vibration conditions on the stability limit, and identify the vibration conditions that achieve high chatter stability. We consider the effect of the air-cutting and multi-rotation delayed regeneration described above, in which chatter displacement occurring more than two spindle rotations before is regenerated, and analyze regenerative chatter vibration during vibration cutting in the frequency domain. In this study, the phase difference φ of tool motion in vibration cutting is focused as an important vibration condition parameter that affects the stability limit. In the conventional condition (φ = π), the air-cutting ratio is limited to a relatively low value, and only the dynamic displacements before one and two spindle revolutions are regenerated. On the other hand, setting φ appropriately under the condition φ ≠ π , the air-cutting ratio is increased. Furthermore, the dynamic displacement is regenerated not only before one and two spindle rotations but also before three or more spindle rotations. These results indicate that proper setting of the phase difference φ is effective in suppressing regenerative chatter vibration due to the effects of both the air-cutting phenomenon and multi-rotation delay. Finally, cutting experiments show that the phase difference φ specified by the analysis was effective in suppressing chatter vibration. In summary, the application of low frequency vibration with an appropriately set phase difference φ is an effective strategy for suppressing chatter vibration without reducing the material removal rate in the turning process. [Display omitted] • We performed chatter stability analysis in low frequency vibration cutting. • Chatter stability is affected by vibration cutting parameters. • Phase difference φ and amplitude ratio A / F heavily impact chatter stability. • Using the specific φ depending on A / F is an effective chatter-suppression strategy. [ABSTRACT FROM AUTHOR]

Uncertain dynamics and unknown time-varying disturbances always exist in servo systems and deteriorate tracking accuracy significantly. To tackle the problem, this paper presents a novel adaptive robust control scheme based on neural networks and the robust integral of the sign of the error (RISE) method. In the proposed scheme, a new neural network compensator is developed, where a reference-driven neural network and an error-driven neural network are employed to compensate for uncertain system dynamics and unknown time-varying disturbances, respectively. And an RISE-based robust feedback controller is designed to suppress uncompensated dynamics. Asymptotic tracking control of the servo system with uncertain dynamics and unknown time-varying disturbances is guaranteed by using the Lyapunov theory. Comparative experiments and simulations with different reference signals and various types of external disturbances were conducted based on a linear motor-driven stage. Experimental and simulational results verify the superior tracking performance and powerful disturbance rejection ability of the proposed method. • An NNRISE control method with enhanced disturbance rejection performance is proposed. • An NN compensator consisting of two different NNs is developed. • A continuous update law is designed to train the NN compensator online. • Experiment and simulation results reveal the validity of the proposed method. [ABSTRACT FROM AUTHOR]

• Industrial robot's servomotor bearing fault detection is presented. • Simple motion and welding motion of industrial robots is considered. • Currents signals of servomotor are converted to scalogram images for analysis. • Transfer learning expunged model training from scratch and streamlined operation. In consequence of their superior performance and durability, industrial robots have enjoyed widespread adoption across a variety of industries. However, despite their sturdy build, they are susceptible to malfunction. The servomotor is a fundamental component of industrial robots, and to ensure smooth and uninterrupted functioning, it is essential to detect any defects it may develop. Although research has addressed methods for detecting bearing failure, diagnosis of a servomotor bearing failure in the industrial robot remains difficult and requires intensive research. In this paper, a novel method for detecting servomotor bearing defects in the industrial robot is provided by integrating knowledge transfer via transfer learning. Initially, current signals of the servomotor are transformed to scalogram images. This processed data is utilized to build the model for fault detection. Applying transfer learning eliminates model training from scratch and streamlined operations. The purported approach shows an average accuracy of more than 99 %. [ABSTRACT FROM AUTHOR]

In the production of paper cups in industrial factories, it is tried to print high quality cups with less waste loss with the help of sensors and heating resistances mounted on the paper cup machine. In this study, a system that detects faulty products based on image processing and removes it by controlling the machine with servo motors, asynchronous motors and programmable logic controller (PLC) is designed. For fault product detection, classification has been performed using real-time Haarcascade algorithm and You Only Look Once (YOLO) algorithm which is a deep learning methods, and real-time object detection has been carried out using the OpenCv library. With this study, an effective faulty product detection and removing hardware system was realized by adapting artificial intelligence algorithms to a machine used in industry. Based on the results, a whole system can be applied to systems that involve removing a faulty product from a band in any production, packaging etc. facility is proposed. A hardware consisting of servo motors, asynchronous motors and PLC was designed to separate faulty cups from the existing paper cup production machine in this study. Then, a data set composed of 1068 images was created with images taken from the camera for faulty and faultless paper cups. Using this dataset, the effect of different deep learning methods on performance in the real-time system has been examined and successful results have been obtained. The optimal outcome was achieved, yielding a real-time application accuracy rate of 90.8% through the utilization of the Yolov5x architecture. [ABSTRACT FROM AUTHOR]

In this paper, a novel robust tracking control strategy based on funnel control is proposed for servo drive systems with unknown disturbances. A modified funnel variable is defined and incorporated into the control design to guarantee the tracking error within a prescribed boundary. To reject the bounded disturbances, a robust integral of the sign of the error (RISE) controller based on the funnel variable is proposed for servo drive systems. Moreover, the desired compensation technique is incorporated into the developed controller to reduce the sensor noise. The proposed robust controller theoretically guarantees asymptotic tracking control performance with external disturbances. The closed-loop system convergence is analyzed via the Lyapunov stability theory. Comparative numerical and experimental results of the servo drive system are provided. • A novel funnel variable is modified and incorporated into control design to improve the transient and steady-state performance. • Using the FC and RISE technique, a funnel tracking control scheme is proposed for servo mechanisms to achieve asymptotic tracking control. • Comparative experimental studies show the advantages of the proposed control method in comparison to other control schemes. [ABSTRACT FROM AUTHOR]

Non-axisymmetric aspheric machining is increasingly important in photoelectric industry. The machining process requires an external feeding device mounted to a machine tool to achieve fast-tool servo (FTS) function. In this study, a piezoelectric (PZT, Lead zirconate titanate) FTS was used to perform non-axisymmetric aspheric machining by control methods. In the beginning, system identification of the PZT tool holder was conducted to obtain the mathematical model of the system and then the simulations were performed for various controllers, including the PID (Proportional-integral-derivative), sliding mode control (SMC), non-singular terminal sliding mode control (NTSMC), and adaptive NTSMC. The simulation results showed that the NTSMC and the adaptive NTSMC had excellent control performances with the tracking errors of 0.0 and 3.1 nm, respectively. Then, control practices without machining were performed with the PV (Peak-to-valley) tracking errors of 0.96 μm, 0.77 μm, and 0.95 μm obtained by the PID controller, NTSMC, and adaptive NTSMC, correspondingly. The large PV errors were found due to the low sampling rate of position commands. Finally, experiments of non-axisymmetric aspheric machining with the implemented controllers were performed for a workpiece of oxygen-free copper (OFC) having 5 mm diameter. The measured results of the machined surfaces were with the PV form errors of 7.2 μm , 2.8 μm , and 3.8 μm in corresponding to the usual machining, using NTSMC and adaptive NTSMC. The effectiveness of the implemented controllers was demonstrated, and the NTSMC showed the best performance. Future works are to examine the repeatability of various controllers with a large hardware memory size and improved environment. - Nonlinear control strategies were proposed for the applications of non-axisymmetric aspheric machining using a PZT-based FTS. - System identification was performed for the machining system using the nonlinear FTS. - Simulation works demonstrated that the tracking errors for the non-axisymmetric component could reach several nanometers only. - Experiments of control practices without actual machining were conducted. The non-singular terminal sliding mode control (NTSMC) showed the best tracking error of submicron. - Experiments of machining controls were performed. The NTSMC also exhibited the best performance. [ABSTRACT FROM AUTHOR]

• Dynamic model of a flexible manipulator considering two-dimensional deformation and friction torque is established. • Analyze the influence of the nonlinear terms in the dynamic model on the deformation. • Combined control method of sliding mode control and fuzzy compensation to control the flexible manipulator. • 4.Flexible manipulator control experiment platform verify the correctness of the model and control strategy The flexible manipulator servo system considering the second-order modal and two-dimensional deformation is too complicated, which is not conducive to real-time control. In order to establish dynamic equations that can be controlled in real-time, it is necessary to analyze each nonlinear factor. Based on the results of dynamic analysis, a model simplification method is proposed that ignores the second-order modal deformation. What's more, an improved fuzzy compensation sliding mode control (FCSMC) strategy is proposed to control the angular velocity of the servo system. The friction torque and the ignoring nonlinear factors are compensated by the fuzzy systems. The improved FCSMC strategy can reduce the chattering phenomenon and the angular velocity errors. Simulation experiments and physical control experiments prove the effectiveness of the improved FCSMC strategy. The results show that the improved FCSMC strategy has smaller angular velocity errors. Therefore, the strategy can effectively improve the movement accuracy of flexible manipulators, which is conducive to the precise end-effectors. [ABSTRACT FROM AUTHOR]

A dual-flexible manipulator with a telescopic arm is affected by joint flexibility, load flexibility, and bearing friction, which will cause angular velocity fluctuation. Besides, the motion of the telescopic arm leads to dynamic parameters of the flexible load in the servo system time-varying. The variation of dynamic parameters increases fluctuations of angular velocity. Fluctuations in angular velocity will aggravate the vibration of the manipulator and affect the control accuracy of end-effectors. In this paper, the adaptive PI control strategy with the disturbance observer (DOB) suppresses the vibration of the manipulator by weakening the angular velocity fluctuations. Firstly, dynamics equations of the dual-flexible manipulator servo system considering the bearing friction are established by using the assumed mode method. Next, the low-pass filter in DOB is designed according to the robust stability theorem, so that the servo system can satisfy the stability under dynamic parameters time-varying and friction torque simultaneously. Then, the adaptive law and the over-load compensation control law are designed by Lyapunov's stability theorem. Finally, numerical simulation analysis and control experiments of the manipulator are carried out. The simulation and experimental results show that: 1) The bearing friction torque can cause angular velocity fluctuations, but the DOB can effectively reduce the influence of the disturbance torque. 2) The adaptive control strategy can effectively reduce angular velocity errors under conditions that the telescopic arm is in different lengths. Therefore, the adaptive PI control strategy with the DOB can effectively suppress angular velocity fluctuations of the manipulator. [ABSTRACT FROM AUTHOR]

Fast tool servo (FTS) is an efficient and reliable method in precision machining for fabricating freeform surfaces or microarrays with sub-micrometric form accuracy. In this paper, a Lorentz force FTS is designed where the voice coil motor is located inside the slide, and four air bearings are used as support components. Three different control algorithms, namely conventional PID control, advanced PID control with velocity/acceleration feed-forward (FF) and sliding mode control (SMC) are implemented in the system, and corresponding Simulink simulation models are built including for both mechanical and electrical systems. The results show that advanced PID and SMC can reduce phase error and overshoot, and tracking error can be controlled at 3.13% at 50 Hz. A new hybrid control algorithm (PID + SMC + FF) is developed, with system tracking error subsequently decreased to 0.871% at 50 Hz. In addition, with a suitable compensation method, the steady state tracking error is further decreased to 0.029%. Consistent results from testing with signals of different input frequency also indicate the general effectiveness of the algorithm. • A novel long stroke fast tool servo system was designed based on voice coil motor. • Different control algorithms were implemented, tested, and evaluated. • A new hybrid control algorithm was proposed and tested for the designed system. • Significant improvement on tracking performance was achieved using the proposed algorithm. [ABSTRACT FROM AUTHOR]

At present, the servo press is developing vigorously. This paper focuses on the main drive system of the servo press. Different from conventional main drive systems (single-sided output servo motor; unilateral bias fixed installation; large belt wheel or large gear transmission), the novel main drive system adopts a two-side output integrated servo motor (floating and central installation). The integrated servo motor is connected with the symmetrical toggle booster mechanism through a planetary roller screw pair, making full use of the resources of the integrated motor and transmission structure. By removing the large belt wheel, the moment of inertia of the novel main drive system can be greatly reduced. Furthermore, the novel main drive system has excellent mechanical and motion characteristics (Low-speed forging, high-speed return). More importantly, the novel main drive system through simple mechanical combination in parallel, constituting multiple sets of the novel main drive system, can be applied to servo presses of different tonnages (small, medium, and large). It facilitates the standardization and serialization of the main drive system, and it has the characteristics of large-scale industrialization and low-cost manufacturing. Accordingly, theoretical analysis and simulation are carried out for the novel main drive system, and a new servo press synchronously driven by two sets of the novel main drive systems is designed and manufactured for motion characteristics experiments and sheet blanking tests. The results manifest that the novel main drive system can achieve the above objectives and has feasibility and practicability. [ABSTRACT FROM AUTHOR]

A multi-bodies hydroelastic model is developed and coupled to the full aero-hydro-servo-elastic analysis of a VLFS (very large floating structure) floating wind turbine. The proposed hydroelastic model discretizes the VLFS into a set of interconnected submodules. The hydrodynamic load acting on the entire VFLS is lumped to the mass center of submodules whilst the structural flexibility is represented by the finite element model used to connect submodules. The multi-bodies character makes the developed hydroelastic model robust to the floating structure and convenient to be embedded into coupled dynamic modelling of offshore floating wind turbines. The established model is validated against model test first and subsequently coupled to the numerical model of a moored VFLS floating wind turbine. The wind turbine power production, VFLS flexible deformation and structural loads are investigated. The analysis results reveal the significance of hydroelasticity on wind turbine power production and structural dynamics. [ABSTRACT FROM AUTHOR]

• A cascaded-type model of a flexible-link robot is obtained for a simple representation of tip position in robot workspace. • Controller easy to implement using only joint angle and tip position measurements. • Asymptotic trajectory tracking of the robot tip is achieved. [Display omitted] The control problem of a single flexible-link robot is addressed for tip position and trajectory tracking control, with no other actuators into the mechanical system than a servomotor installed at the rigid joint. A multi-modal cascaded-type model of the robot is obtained, where the angle of the rigid joint is considered as the control input for the flexible-link rather than the torque provided by the servomotor. A Sliding-Mode Control approach is used to overcome the rigid mode dynamics and ensure a precise tracking of a flexible-state dependent trajectory at the joint level. The proposed control scheme is simple, easy to implement and yet robust against parametric uncertainties. The main results show that, trajectory tracking at the tip of the flexible-link is achieved, with guaranteed closed-loop stability, since the problem is reduced to the tracking of an adequate trajectory at the joint level. The proposed results are validated with several experimental results. Finally, the control scheme is quantitatively compared with two different controllers for flexible robots. [ABSTRACT FROM AUTHOR]

This paper introduces a novel approach to fault detection in the servo motor bearings of industrial robots within the context of Industry 4.0 prognostics and health management. The proposed solution leverages the innovative feature aggregation network for robotic fault detection in the application of smart factory. Overcoming challenges associated with traditional techniques that include handcrafted features, transfer learning, and deep learning models, the proposed approach offers a hierarchical information aggregation mechanism. The model is customized through hyperparameter tuning, resulting in a streamlined architecture with significantly fewer parameters. This parameter efficiency is notably distinct when compared to off-the-shelf transfer learning models that commonly feature extensive parameter counts in the range of hundreds of thousands or millions. The proposed model subjected to rigorous validation across diverse experimental scenarios that affirm its adaptability and robust performance. The model showcases accuracy in fault detection under both simple and welding motion scenarios, while its generalization capabilities are demonstrated as it successfully predicts health states in welding motion, showcasing versatility and reliability across various operational scenarios. [ABSTRACT FROM AUTHOR]

This paper presents a solution to address wear and tear of Run-of-River (RoR) Hydropower Plants (HPPs) providing enhanced Frequency Containment Reserve (FCR). In this respect, the study proposes the integration of a Battery Energy Storage System (BESS) with RoR HPPs controlled by a double-layer Model Predictive Control (MPC). The upper layer MPC acts as a state of energy manager for the BESS, employing a forecast of the required regulating energy for the next hour. The lower-layer MPC optimally allocates the power set-point between the turbine and the BESS. Reduced-scale experiments are performed on a one-of-a-kind testing platform to validate the proposed MPC-based control considering a comparison with different control strategies and different BESS sizes. The results demonstrate superior performance of the proposed framework, compared to simpler techniques like dead-band control or to the standalone RoR scenario, leading to improved FCR provision, reduced servomechanism stress, and extended hydropower asset lifespan. • BESS hybridization of Kaplan turbines is studied to enhance FCR and asset lifetime. • A double-layer MPC is used to optimally control the hybrid system. • Experiments validate the control strategies on a unique reduced-scale model testing platform. • Results show superior FCR provision and reduced wear of the BESS-hybridized Kaplan. [ABSTRACT FROM AUTHOR]

This study explores the practical viability of repurposing aging Kaplan turbines into variable-speed propellers by employing full-size frequency converters. The motivation behind this approach is to improve the provision of Frequency Containment Reserve (FCR) while reducing fatigue in the Kaplan blades servomechanism. We evaluate the performance of these modified Kaplan turbines against the one of another hydro asset composed of the same Kaplan turbine hybridized with a Battery Energy Storage System (BESS). Experiments are conducted on a one-of-its-kind reduced-scale model testing platform. Our findings reveal that Kaplan turbines repurposed as variable-speed propellers exhibit similar dynamic response characteristics compared to the standalone Kaplan operation, with the added benefit of effectively eliminating blade movements. Furthermore, the ability to control the speed increases the hydraulic efficiency for certain operating points. In summary, investment in variable speed technology emerges as a viable alternative to BESS-based hydropower hybridization. • Repurposing Kaplan turbines as variable speed propellers enhances FCR provision. • Variable-speed propellers shown to reduce wear on blades and increase it on guide vanes. • Experimental comparison with BESS hybridization validates both approaches to enhance FCR provision. [ABSTRACT FROM AUTHOR]

It is important to ensure the transient safety and stability of Hydropower generating system (HGS) both in the design and operation stages. Many uncertainties in the Hydropower Generating Units (HGUs) have a strong effect on the transient characteristics. In this study, a transient analysis framework under parameter uncertainty is proposed, which includes: integrating modeling, uncertain transient analysis, and transient calibration. First, not only a physical HGS including a comprehensive model of hydro-turbine but also Polynomial-Chaos-Kriging data-driven models are established for transient considering uncertain HGU parameters. Secondly, based on the evaluation system, the contributions of uncertain HGU parameters on the transient characteristics are quantified objectively. The results show that: (1) in evaluation systems, 6 HGU parameters play a key effect on transient characteristics, and the uncertain properties of 6 indicators can reach moderate variabilities; (2) the effect of HGU uncertainty can be reduced by optimizing the control strategies. Finally, uncertain HGU parameters are calibrated considering 3 measured transient processes. Compared with the conventional HGU model, the max relative absolute error of the volute pressure, the HGU speed, and the servomotor stroke are reduced by 2.14%, 2.70%, and 37.81%. This framework provides new insight into the effect of the uncertain HGU model on transient characteristics, which could be beneficial for the safe and stable operation of HGSs. • Propose a transient analysis framework for parameter uncertainty analysis and transient calibration. • Quantify and rank the contribution of the major influencing HGU parameters to transient characteristics. • The max error in P v , n t, and Y s are reduced by 2.14%, 2.70%, and 37.81% using the calibrated model. • Guide uncertain transient analysis of hydropower generating systems in both the design and operation stages. [ABSTRACT FROM AUTHOR]

Maternal recognition of pregnancy (MRP) is a term utilized in mammals to describe pathways in which the conceptus alters the endometrial environment to prevent regression of corpora lutea to ensure continued production of progesterone (P4) required for establishment and maintenance of pregnancy. For nearly 40 years after publication of the endocrine/exocrine theory, conceptus estrogen (E2) was considered the primary maternal recognition signal in the pig. Conceptus production of prostaglandin E2 (PGE2) was also considered to be a major factor in preventing luteolysis. An addition to E2 and PGE2, pig conceptuses produce interleukin 1B2 (IL1B2) and interferons (IFN) delta (IFND) and gamma (IFNG). The present review provides brief history of the discovery of E2, PGs and IFNS which led to research investigating the role of these conceptus secreted factors in establishing and maintaining pregnancy in the pig. The recent utilization of gene editing technology allowed a more direct approach to investigate the in vivo roles of IL1B2, E2, PGE2, AND IFNG for establishment of pregnancy. These studies revealed unknown functions for IFNG and ILB2 in addition to PGE2 and E2. Thus, pregnancy recognition signal is via a servomechanism in requiring sequential effects of P4, E2, IL1B2, PGE2 and IFNG. Results indicate that the original established dogma for the role of conceptus E2 and PGs in MRP is a far too simplified model that involves the interplay of numerous mechanisms for inhibiting luteolysis, inducing critical elongation of the conceptuses and resolution of inflammation in pigs. • Review of the history of estrogen, prostaglandin and interferon discovery and function. • Models for maternal recognition of pregnancy in the pig. • Role of estrogen and prostaglandin E in CL maintenance in the pig. • Utilization of conceptus gene editing to establish the role conceptus factors in establishment of pregnancy. [ABSTRACT FROM AUTHOR]

We present a 4-degrees-of-freedom (4-DoF) wearable haptic device for the palm, able to provide the sensation of interacting with slanted surfaces and edges. It is composed of a static upper body, secured to the back of the hand, and a mobile end-effector, placed in contact with the palm. They are connected by two articulated arms, actuated by four servo motors housed on the upper body and along the arms. The end-effector is a foldable flat surface that can make/break contact with the palm to provide pressure feedback, move sideways to provide skin stretch and tangential motion feedback, and fold to elicit the sensation of interacting with different curvatures. The paper presents the design of the wearable haptic device, together with its mobility, statics, and manipulability, as well as direct, inverse, and differential kinematics. We also present a position control scheme for the device, which is then quantitatively evaluated. [ABSTRACT FROM AUTHOR]

Escape is one of the most essential behaviors for an animal's survival because it could be a matter of life and death. Much of our current understanding of the neural mechanisms underlying escape is derived from the looming paradigm, which mimics a diving aerial predator. Yet, the idea of the looming paradigm does not account for all types of threats like lions hunting antelopes or cats stalking mice. Escape responses to such terrestrial threats may require different strategies and neural mechanisms. Here, we developed a real-time interactive platform to study escape behavior to terrestrial threats in mice. A closed-loop controlled robot was magnetically pulled to mimic a terrestrial threat that chases a mouse. By using strong magnets and high-precision servo motors, the robot is capable of moving precisely with a high spatial-temporal resolution. Different algorithms can be used to achieve single approach or persistent approach. Animal experiments showed that mice exhibited consistent escape behavior when exposed to an approaching robotic predator. When presented with a persistently approaching predator, the mice were able to rapidly adapt their behavior, as evidenced by a decrease in startle responses and changes in movement patterns. In comparison to existing methods for studying escape behavior, such as the looming paradigm, this approach is more suitable for investigating animal behavior in response to sustained threats. In conclusion, we have developed a flexible platform to study escape behavior to terrestrial threats in mice. • A flexible platform to study escape behavior to terrestrial threats in mice. • Mice perceive the approaching robotic predator as a threat and escape quickly. • Mice can quickly adapt their behavior when facing a persistent threat. • The visual information is still critical in eliciting escape behavior to terrestrial threats. [ABSTRACT FROM AUTHOR]

• Firstly, an interactive interface for human–machine interaction was developed based on kinematic analysis and the system's hardware configuration. • Simultaneously, we constructed a negative feedback control model for the lateral movement speed of the conveying device. We integrated an adaptive genetic algorithm-optimized fuzzy PID control algorithm with the servo motor's S-curve acceleration and deceleration control. • In order to determine the relevant control parameters, the control accuracy of the system, and the transplanting performance indexes, simulation and comparative tests, indoor whole machine dynamic speed control transplanting tests, and field tests were carried out in terms of response speed, steady state, and robustness, to provide a theoretical basis and reference for the precise control of rice potting. Aiming at the problems of low transverse conveying accuracy and poor speed adaptability in the mechanized transplanting of rice potted seedlings, this study focused on a precision transplanting machine with an independent motor drive and designed a precision control system using a GA-Fuzzy PID controller. Firstly, an interactive interface for human–machine interaction was developed based on kinematic analysis and the system's hardware configuration. Simultaneously, we constructed a negative feedback control model for the lateral movement speed of the conveying device. We integrated an adaptive genetic algorithm-optimized fuzzy PID control algorithm with the servo motor's S-curve acceleration and deceleration control. This combination enabled variable-speed input control for the lateral movement of the conveying device, enhancing lateral conveying accuracy while reducing vibration interference. Then, we conducted comparative experiments to evaluate the system's control precision and the performance of transplanting operations. Simulation results showed that the response speed, steady state, and robustness of GA-Fuzzy PID were better than those of traditional PID and fuzzy PID control. The dynamic speed transplanting test of the indoor whole machine showed that the average transplanting success rate of the GA-Fuzzy PID control system was 92.21 %, the average maximum speed error was 1.50 mm/s, the average speed coefficient of variation was 0.19 %, and the average plant spacing coefficient of variation was 1.29 % when the walking speed was in the range of 0.26 ∼ 0.48 m/s. A comparison of the field test results and the indoor test showed that the system could still operate stably under external interference, and the system had strong robustness and operational stability. Therefore, it showed that the GA-Fuzzy PID control system can adapt to different speeds, has good control performance, and meets fast and stable design requirements. The results of this study can provide a theoretical basis and reference for the precise control of rice pot seedling transplanting. [ABSTRACT FROM AUTHOR]

This paper investigates the accurate servo position control of the permanent magnet synchronous motor (PMSM)-driven system under varying external disturbance and unknown mechanical friction. Firstly, to overcome the difficulty of state observer design caused by uncertainties, the interval type-2 fuzzy logic system (IT2 FLS) is introduced to approximate the nonlinear friction. Meanwhile, the nonlinear disturbance observer (NDO) is employed to estimate the lumped disturbance. Then aiming to solve the problem of explosion of complexity and filtering error, a finite-time (FT) adaptive IT2 fuzzy output feedback controller is proposed by combining the error compensation mechanism and FT control. In addition, to further improve the performance of the closed-loop system, the adaptive law is updated by the compensation error signal. By means of Lyapunov stability theory, all signals in the closed loop system can be guaranteed to be finite-time stable. Numerical simulations and real-time experiments are presented to demonstrate the effectiveness and superiority of the proposed controller. • A kind of finite-time type-2 fuzzy servo position control of PMSM is designed. • A type-2 fuzzy state observer considering the disturbance is designed. • The finite-time control technique is introduced to ensure the finite time bounded. • The adaptive laws ensure the stability of the system by the Lyapunov stability theory. [ABSTRACT FROM AUTHOR]

This paper presents force servo single point diamond cutting of freeform surfaces with nano-precision on a micro-precision machine. For nanometric machining accuracy, traditional diamond cutting based on position servo, requires accurate machine axial motions by ultra-precision machine with high cost, or utilizes a fast tool servo to compensate for machine slide vibration and motion error of common machines that is a complicated procedure. In this paper, nanometric machining accuracy was achieved on a micro-precision machine by force servo diamond cutting, in which the tool can be driven to trace the workpiece surface to compensate for the machine slide vibration, machine motion errors and workpiece incline errors accurately and automatically. For highly sensitive and stable force controlling, force servo nanocutting mechanism (FSNM) based on flexible structures was designed with force sensing resolution down to submillinewton level, and a damping controller was developed to suppress the resonant vibration of the FSNM. For extending application of force servo cutting from fabrication of only discontinuous microstructures to continuous freeform surfaces, referring force maps were developed by considering the real material removal volume of each cutting point. Force servo cutting was then validated by fabricating freeform surfaces with surface form errors of less than 10 nm on silicon spherical surfaces based on the micro-precision machine. The works discussed in this paper provide an effective technique for the fabrication of complex and continuous microstructured and freeform surfaces with nano-precision by common machines only with micron even tens of microns precision. [Display omitted] • Force servo nanocutting mechanism was designed with force sensing resolution of submillinewton level. • Machine slide vibration and motion errors were automatically compensated in force servo cutting process. • Fabrication of nano-precision complex freeform surfaces was achieved on a machine with only micro-precision. [ABSTRACT FROM AUTHOR]

Floating vertical axis wind turbines (VAWTs) have many advantages over floating horizontal axis wind turbines (HAWTs) at large scales in deep water; however, there are several key challenges to overcome as well. One of the challenges is accurate prediction of the dynamic motion and loads performance of a floating VAWT. A new semi-coupled aero-servo-hydro method is developed to assess dynamic responses of a floating VAWT by modeling the system as a 7-degree-of-freedom (7-DOF) model: the supporting platform is considered as a 6-DOF rigid body; the rotation of the rotor is considered as the 7th DOF. Aerodynamic, hydrodynamic, and mooring loads and control of the rotor speed are fully considered. This model can predict performance of floating VAWTs with reasonable fidelity according to validation with OrcaFlex through static and dynamic responses of a floating VAWT with Darrieus rotor operating on a new tension-leg platform (TLP). Being a reduced complexity model, the 7-DOF model can be efficiently applied to assess performance of the newly designed floating VAWT. This model is used to examine the relative contributions of aerodynamic and wave loads imparted to the floating system and the benefits of a three-bladed VAWT over a two-bladed VAWT through dynamic and fatigue analysis. • A semi-coupled aero-servo-hydro 7-DOF model is developed and validated for floating VAWTs. • The coupling or interaction between the VAWT rotor and floating system loads and dynamics is studied. • Contributions of different loading components are assessed to determine which are more important to floating system design. • Three-bladed floating VAWTs have better performance of platform motions and tendon fatigue life than two-bladed VAWTs. • Impacts of intra-cycle RPM control on floating VAWTs are studied. [ABSTRACT FROM AUTHOR]

• A novel hardware configuration is proposed to reduce the throttle loss and overflow loss simultaneously. • The nonlinear model of the proposed system is established and the key parameters are analyzed. • A desired compensation approach based output feedback controller is proposed for the asymmetric hydraulic actuator. • The proposed system and controller can achieve the multi-objective task of position tracking and energy saving. Eliminating substantial energy dissipation and achieve precise tracking accuracy are both vital for the hydraulic actuated servo system, especially in the face of the global energy crisis and energy exhaustion. When an asymmetric hydraulic cylinder moves symmetrically back and forth, the pressure and flow in the two chambers differ a lot, resulting in huge energy loss. To reduce the throttle loss and overflow loss of the system simultaneously, a hydraulic servo system structure based on dual hydraulic accumulators is proposed in this paper. On the one hand, two hydraulic accumulators with different pressure levels can switch the supply pressure based on the motion direction of the hydraulic cylinder to reduce the throttle loss. On the other hand, the hydraulic accumulators can absorb the excess flow to reduce the overflow loss. In addition, an output feedback controller based on the desired compensation approach is proposed to guarantee the control performance. First, the pressure and velocity signals are replaced by their desired values to reformulate the state equation. Subsequently, the state variables and lumped disturbance are estimated by the low-pass filter-based observer. Compared with the conventional method, this method has the advantages of low noise interference, fewer control parameters and intuitive form. To validate the feasibility of the proposed strategy, the stability of the controller and the energy efficiency of the system are analyzed. The results indicate that the proposed method can significantly improve the system efficiency and ensure tracking accuracy simultaneously. [ABSTRACT FROM AUTHOR]

High energy efficiency and tracking accuracy are both vital for hydraulic lifting servo systems. However, the appropriate hardware configuration and its corresponding nonlinear controller is always a problem to be solved. To address this multi-objective task, an integrated energy-saving and position tracking controller is developed. Specifically, to reduce the substantial energy dissipation, a system configuration referring to the structure of the three-position-six-way valve is proposed. To ensure accurate tracking performance, a hybrid observer-based output feedback controller is developed. By doing so, the function of flow regeneration and the property of flow matching are achieved, and the tracking accuracy is guaranteed by using only position signal. To validate the effectiveness of the proposed method, a common Lyapunov function is used to prove the stability of the multi-model system, and case studies are conducted to demonstrate the system performance. • The multi-objective task is achieved. • System efficiency is improved by using the proposed scheme. • Tracking accuracy is guaranteed by the proposed controller. • Stability of the system is proved by common Lyapunov theory. • Estimates of states and unmatched uncertainties are obtained. [ABSTRACT FROM AUTHOR]

In this paper, a novel resilient control technique is proposed for discrete-time stochastic Brownian systems with simultaneous unknown inputs and unexpected faults. Prior to previous work, the stochastic Brownian system under consideration is quite general, where stochastic perturbations exist in states, control inputs, uncertainties, and faults. Moreover, the unknown input uncertainties concerned cannot be fully decoupled. Innovative observer by employing augmented system approach, decomposition observer, and optimization algorithms is proposed to achieve simultaneous estimates of both states and faults. Furthermore, fault reconstruction-based signal compensation is formulated to alleviate the effects from actuator faults and sensor faults. An observer-based controller is eventually constructed to enhance the stability and robustness of the closed-loop dynamic system. The integrated resilient control technique can ensure the system has reliable output even under faults. Both linear systems and Lipschitz nonlinear systems are investigated and the design procedures are addressed, respectively. Finally, the proposed resilient control techniques are validated via an electromechanical servo-system, and an aircraft system. • Novel estimation techniques for discrete-time stochastic Brownian systems. • Resilient control to mitigate the influences from the faults to the system. • Robust stochastic stabilizations are proven. • Validation by an electromechanical servo system and a flight control system. [ABSTRACT FROM AUTHOR]

This work aims to explore methods to retain the robustness and performance of a wind turbine controller under different wind conditions. A method of optimizing the control parameters in response to different turbulence intensity is proposed, which is referred to as adaptive turbulence-based control (ATBC). Specifically, the power spectrum of the rotor effective wind speed has been derived and the analytical expression is explicitly considered in the control optimization. Also, a linear aero-servo-elastic (ASE) model is established, which captures the closed-loop dynamics of the rotor speed, pitch activity and tower fore-aft vibration mode. Subsequently, a computationally-efficient component damage prediction method is proposed that uses rainflow counting and inverse fast Fourier transform. Based on the proposed ASE model and damage prediction method, the controller optimization problem is established using a quadratic cost function to achieve the optimal trade-off between the rotor speed variation and the damage of turbine components. A model validation shows that the proposed scheme is able to predict the component fatigue load and the rotor speed variation in an efficient way. Finally, one design case is given to illustrate the procedure of ATBC and to demonstrate the feasibility of the proposed method in different operating wind conditions. • An analytical expression of power spectral density of rotor effective wind speed is explicitly considered in control optimization. • Fast and reliable component damage estimation is proposed based on a linear aero-elastic-servo model. • The proposed scheme is applicable to predict the component fatigue load and the rotor speed variation in an efficient way. • The optimization framework can retain the robustness and performance of the controller under different wind conditions. [ABSTRACT FROM AUTHOR]

In this study, the influence of mechanical vibration characteristics on the efficiency of a servo motor was experimentally investigated. For this purpose, a dedicated apparatus comprising two servo motors connected to a coupling was used. The efficiency of the motor was investigated by first considering the signals of voltage and current; then, the mechanical power was calculated from the acquired torque and angular velocity supplied by the motor. Subsequently, working conditions involving different angular velocities and loading torques were investigated to generate a motor efficiency map. To clarify the influence of the vibration characteristics on the motor efficiency, two types of couplings differing in torsional stiffness and damping characteristics were considered—Type A and Type B. The efficiency was calculated for eight vibration conditions imposed via the selection of the velocity control gain settings for both types. Resultantly, the manner in which the efficiency is affected by the vibration conditions was clarified. Moreover, coupling in the case of better vibration damping characteristics was confirmed to yield a higher motor efficiency for all gain settings. Furthermore, motor working conditions corresponding to high and low motor efficiencies were evaluated, and the motor thermal behavior was investigated. Overall, a lower motor efficiency was confirmed to be associated with increasing temperatures. These results suggest the importance of the vibration characteristics of mechanical systems for achieving high efficiency. • Influence of mechanical vibration on the motor efficiency is newly evaluated. • Power consumption of vibration part is quantitatively evaluated. • Relationship of the motor efficiency and temperature rises of a motor is confirmed. [ABSTRACT FROM AUTHOR]

Fast tool servo (FTS) cutting has the superiority of high efficiency and high precision, which has attracted great attention from the field of microstructure machining. 3-degree-of-freedom (DOF) FTS device driven by piezoelectric (PZT) actuator, with high frequency, high precision, and low crosstalk property, are quite appealing for realizing complex microstructure machining. Therefore, a novel 3-DOF piezo-actuated FTS mechanism with high natural frequency and decoupling property is proposed in this paper. First, the static and dynamic models of the mechanism are established by using the compliance matrix and Lagrange equation methods, respectively. Then, the structural parameters of the mechanism are optimized by the genetic algorithm (GA) based Pareto multi-objective optimization algorithm. With the purpose of verifying the property of the above approach, the finite element analysis (FEA) acting on the designed mechanism has been carried out. Moreover, the modeling tasks in terms of cutting principle and trajectory planning are demonstrated in detail. Besides, a series of tests are carried out to verify the performance of the developed 3-DOF FTS. The testing results indicate that the working stroke of the mechanism is up to 40 μ m, the natural frequency is above 873 Hz, and the mechanism has excellent motion decoupling performance (within 2%). The error of the trajectory tracking in all three directions are kept within ±0.7 μ m. Finally, compared with the desired surface, the error of the machined microstructural surface is kept within ±1.5 μ m, which further verifies its satisfactory performance towards ultra-precision FTS machining of microstructure. ● We focus on fast tool servo with three degrees-of-freedom for ultra-precision machining of microstructures. ● In view of the limitations of traditional 1-DOF FTS on complex microstructure machining, a novel 3-DOF FTS device with high speed, high precision, and decoupling property is proposed. ● With the developed 3D-FTS cutting system, high-precision microstructure surfaces are fabricated. ● The theoretic, simulated, and practical experimental results uniformly prove that the developed 3D-FTS cutting system is feasible and effective. [ABSTRACT FROM AUTHOR]

This paper proposes a new vibration cutting method named "multimode vibration cutting" for precision surface texturing. The proposed cutting method utilizes multiple unidirectional vibration modes mainly in the depth-of-cut direction. The vibrations at multiple frequencies induced to the tool tip can generate not only sinusoidal but also highly-flexible trajectories such as trapezoidal, triangular, and distorted triangular waves. Notably, only a sinusoidal vibration can be induced when a single resonant vibration is applied to the tool tip. Compared to conventional highly-flexible cutting methods for surface texturing, such as the utilization of fast tool servo and amplitude control of ultrasonic elliptical vibration cutting, the proposed method is highly-efficient because of its direct usage of high resonant frequencies. Compared to conventional highly-efficient cutting methods for surface texturing, such as linear and elliptical vibration cutting which mainly utilizes the vibration component in the depth-of-cut direction, the proposed method can generate highly-flexible trajectories for various micro texture profiles. In this study, an ultrasonic multimode vibration device is developed, and the mechanics of generating multimode vibrations are demonstrated. Turning experiments with several texture profiles are performed to confirm the validity of the proposed method for highly-efficient and highly-flexible micro/nano surface texturing. • A novel method is proposed which utilizes multiple unidirectional vibration modes in the depth-of-cut direction. • Developed vibration device and precise vibration generation methodology is demonstrated. • Highly-efficient and highly-flexible micro/nano surface texturing is realized. [ABSTRACT FROM AUTHOR]

The paper presents a nonlinear dynamic model for DGMSCMGs, sometimes used as actuators to control the attitude of large satellites. The developed models describe the translation dynamics, the rotation dynamics of the Active Magnetic Bearing Rotor, as well as the rotation dynamics of the two mobile gimbals. Two control architectures are initially designed by using the dynamic inversion concept, proportional-integrator-derivative/proportional-derivative dynamic compensators, linear observers, and a neural network to compensate the effect of the dynamic inversion error. One also develops a similar adaptive control architecture consisting of a proportional-integrator dynamic compensator, a feed-forward neural network, and a linear observer. The latter system models two interconnected nonlinear servo-systems and controls the angular rates of the two mobile gimbals actuated by the attitude controller of the satellite. The validation of the novel control architectures is achieved in Matlab/Simulink, the obtained results proving a very good angular rate precision and the robustness of the control systems in relation to the external disturbances. [ABSTRACT FROM AUTHOR]

Cutting force measurement is important for monitoring the diamond cutting process. In this paper, a new measurement method of thrust cutting force associated with a voice coil motor (VCM) driven fast tool servo (FTS) system has been developed. Instead of integrating additional force sensors to the FTS which would influence the dynamics of the FTS, the force measurement in the proposed system is achieved associated with in-process monitoring the variation of the driving current of the VCM and pre-process determining the system parameters. In this way, the cutting forces are accurately obtained by subtracting the influences of the driving force, the spring force, the damping force and the inertial force associated with the system as well as the cutting process. Based on the proposed method, a microstructure array was machined using the developed VCM-FTS and the cutting force during the machining process was monitored in real time. The measured force signal was in good agreement with the machining result. The surface profile error of the fabricated microstructure could be clearly distinguished by the variation of the measured cutting force signal. This provides a new approach for in-process cutting force measurement associated with FTS based diamond cutting process. • A cutting force measuring method associated with a voice coil motor (VCM)-driven fast tool servo (FTS) system has been developed. • Cutting force in diamond cutting are in-process measured without any force sensor by the VCM-FTS. • The influences of servo motion induced forces are separated for accurately obtaining the cutting forces. [ABSTRACT FROM AUTHOR]

This paper proposes a finite-time adaptive neural network (NN) position tracking control method for the permanent magnet synchronous motor (PM SM) servo system with full-state constraints. NNs are utilized to compensate the parameter uncertainties and load torque disturbances of the PMSM servo system. Multiple barrier Lyapunov functions are introduced in the backstepping based control design, such that the rotor position, the rotor angular velocity and the currents of the d-q axis are constrained in given compact sets. In addition, the finite-time control technique is adopted to the control design, which can accelerate the convergence speed and improve the robustness of the PMSM servo system. Under the proposed control algorithm, the position tracking control is realized in finite time, and the tracking error can converge to a small neighborhood of the origin. Finally, simulation results are presented to show the effectiveness of the developed control approach, and some comparisons are given to show the rapid and accurate position tracking control performance. [ABSTRACT FROM AUTHOR]

The grid has increasingly higher reliability requirements for hydropower supply and regulation, imposing higher requirements for the stability of hydraulic turbine governing system (HTGS). The mechanical structure of the unit is complex, and the adjustment of the active guide vane needs the hydraulic servo system with multistage amplifier to provide force, which makes the governor response output lag. The control of an HTGS that focuses on Lyapunov asymptotic stability may have poor transient performance. Therefore, a brand-new nonlinear finite-time Takagi–Sugeno fuzzy control scheme for HTGSs with mechanical time delay is proposed. First, based on the Takagi–Sugeno fuzzy model with time delay, a time-delay HTGS that considers the inherent delay effect of the HTGS relay component as well as its fuzzy model is presented. Second, based on the finite-time stability theorem, a nonlinear finite-time Takagi–Sugeno fuzzy controller for the HTGS is proposed and a practical stability condition is given in the form of matrix inequalities. Furthermore, the matrix inequalities are transformed into a set of linear matrix inequalities, which are easy to solve. Finally, numerical experiments on HTGS under various operating conditions demonstrate the proposed scheme's effectiveness and superiority compared with the traditional proportional integral derivative control. • A nonlinear time-delay hydraulic turbine governing system as well as its Takagi–Sugeno fuzzy model is established. • A brand-new nonlinear finite-time Takagi–Sugeno fuzzy control scheme for the hydraulic turbine governing system is proposed. • A sufficient stability condition where the hydraulic turbine governing system achieves finite-time stability is given. • The gain matrices of the controller can be easily obtained by solving a set of linear matrix inequalities. • Numerical experimental results verify the validity and superiority. [ABSTRACT FROM AUTHOR]

• A novel adaptive law updated by the event-triggered sampled data is developed over the plant-control communication network. • The measurement error induced by the event-triggered mechanism is compensated by introducing a novel kind of dynamics. • The parameter mismatch difficulties for the event-triggered adaptive law design are tackled. In this paper, the adaptive event-triggered output regulation problem for the parametric strict feedback system is addressed. The adaptive control strategy over the plant-control communication network is developed and governed by the transmission sampled data of the plant, completely. By introducing an augment dynamic to compensate the event-triggered measurement errors, the event-triggered mechanism is developed independent on the stability of the adaptive algorithm. Therefore, a more flexible and robust event-triggered mechanism is proposed than the existing method where the threshold coefficients are constrained with the closed-loop system stable requirement. It is proved that, the asymptotical output regulation error upper bound is continuously dependent on the event-triggered threshold coefficient, but independent on the upper bound of unknown parameters. Therefore, the output regulation error upper bound can be modified by the feedback gains and threshold coefficients without considering the bounded unknown parameters. What's more, the Zeno phenomenon is discussed carefully and excluded. Finally, the event-triggered adaptive control method is applied to control the double-rod electro-hydraulic servo system. It is shown that, the proposed scheme has smaller output regulation error than the existing methods with less communication times. [ABSTRACT FROM AUTHOR]

This paper presents a fractional order (FO)-active disturbance rejection control (ADRC) with a FO extended state observer (FOESO) design. Applying this FOESO, a typical second order motion plant can be converted into a c a s c a d e d f r a c t i o n a l o r d e r i n t e g r a t o r (1 ∕ s 2 r ; 0 < r < 1) with considering all other dynamics and internal/external disturbances as t o t a l d i s t u r b a n c e s. Therefore, a single proportional controller which is not sensitive to system noise can realize a stable control system. According to the frequency characteristics of equivalent FO system model, the FO-ADRC control system is robust to systematic uncertain dynamics and disturbances. Furthermore, without differential action which is needed for the typical double integrator plant control, the proposed control system achieves good robustness to high-frequency noise. Simulation and experiments on PMSM speed servo system are performed, showing that the proposed FO-ADRC behaves better than integer order ADRC (IO-ADRC) and FOPI controller. This FO-ADRC methodology can be simply extended to general control plants. • A fractional order ADRC structure is proposed with a fractional order extended state observer. • The fractional order cascaded integrator idea is proposed for the overall FOADRC system to realize an equivalent system with proper phase margin, with which a stable closed-loop system can be achieved by using a simple proportional controller. • Simulation and experiments are performed on PMSM speed servo, to demonstrate the control performance advantages of the proposed FO-ADRC over the traditional integer order ADRC and FOPI controller. [ABSTRACT FROM AUTHOR]