High Speed Precision Research Articles

Feature level fusion of vibration and acoustic emission signals in tool condition monitoring using machine learning classifiers

To implement the tool condition monitoring system in a metal cutting process, it is necessary to have sensors which will be able to detect the tool conditions to initiate remedial action. There are different signals for monitoring the cutting process which may require different sensors and signal processing techniques. Each of these signals is capable of providing information about the process at different reliability level. To arrive a good, reliable and robust decision, it is necessary to integrate the features of the different signals captured by the sensors. In this paper, an attempt is made to fuse the features of acoustic emission and vibration signals captured in a precision high speed machining center for monitoring the tool conditions. Tool conditions are classified using machine learning classifiers. The classification efficiency of machine learning algorithms are studied in time-domain, frequencydomain and time-frequency domain by feature level fusion of features extracted from vibration and acoustic emission signature.

Theoretical and Experimental Study on Active Stiffness Control of a Two-Degrees-of-Freedom Rope-Driven Parallel Mechanism

Abstract Rope-driven mechanisms with the characteristics of high speed, low inertia, and high precision are widely utilized in numerous fields. Stiffness is an important indicator to illustrate the precision and compliance of the mechanism. However, realizing active stiffness control is difficult for the mechanisms due to the coupling of rope tension and controller stiffness. To solve the problem, a verification prototype, 2-DOF rope-driven parallel mechanism (RDPM), is designed and manufactured, and its mechanical model is established. And then the general stiffness model of the RDPM is derived. Meanwhile, the rope-hole friction is calculated based on the Stribeck model. An active stiffness control scheme considering the pose retention, vibration suppression, and friction compensation is proposed. According to the stiffness model and active stiffness control law, the linear motion stiffness of the RDPM is analyzed in detail. The conclusion shows the motion stiffness is linear with the controller stiffness and initial rope tension. Finally, the theoretical stiffness, simulation stiffness and experimental stiffness are calculated and compared by the co-simulation technique and physical prototype experiment. The error between experimental data and simulation data is within 10%, which verifies the stiffness model and active stiffness control scheme.

ADAPTIVE WAVELET FUZZY CMAC TRACKING CONTROL FOR INDUCTION SERVOMOTOR DRIVE SYSTEM

In this study, a control system is proposed for the induction servomotor to achieve the highprecision speed tracking based on wavelet fuzzy cerebellar model articulation controller. In this proposed scheme, the wavelet fuzzy cerebellar model articulation controller (WFCMAC) is used to imitate an ideal controller due to it incorporates the advantages of the wavelet decomposition property with a fuzzy CMAC fast learning ability and the smooth compensator controller with bound estimation is designed to attenuate the effect of the approximation error caused by the WFCMAC approximator. The online tuning laws of WFCMAC and the smooth compensator with bound estimation parameters are derived in gradient-descent learning method and Lyapunov function so that the stability of the system can be guaranteed. Finally, through the experimental results of proposed control system is developed for induction servomotor is provided to verify the effectiveness of the proposed control methodology even the dynamical model of the induction servomotor is complete unknown.

A piezoelectric stick–slip drive nanopositioner with large velocity under high load

Piezoelectric stick–slip drive nanopositioners are of central importance in in situ SEM nanorobotic systems due to their high precise positioning, large stroke, high speed, and compact structure. However, the output velocity under high load will be seriously influenced. In this paper, a new piezoelectric stick–slip drive nanopositioner with large velocity under high load by introducing the adjust bolts to decouple the driving unit and moving unit is presented. A MATLAB simulation model has been created to optimize the nanopositioner for a certain velocity, and a FEM is used to confirm that the leaf hinge has sufficient stiffness. The size of the prototype is 30 × 32 × 25 mm3. Testing results indicate that the nanopositioner achieves a maximum velocity of 3.467 mm/s and a minimum resolution of 6 nm. When the load increases from 0.4 kg to 2 kg, the maximum velocities only decrease from 3.457 mm/s to 3.143 mm/s. The proposed piezoelectric stick–slip nanopositioner shows large velocity under high load.

An acoustic remote sensing method for high-precision speed estimation of micro-UUVs

Understanding the dominant sources of acoustic noise in unmanned underwater vehicles (UUVs) is important for passively tracking UUVs and for designing quieter propulsion systems. This work describes how the speed of a vehicle can be passively measured by the unique high frequency acoustic signature of a brushless DC motor propulsion system. First, the causes of high frequency tones were determined through direct measurements of two micro-UUVs and an isolated thruster. From this analysis, the vehicle noise was mapped to speed and the common and dominant features of noise were established: strong tones at the motor's pulse-width modulated frequency and its second harmonic, each of which is a carrier with sidebands at frequency intervals equivalent to the propeller rotation frequency multiplied by the poles of the motor. Field experiments were performed where the speed of two micro-UUVs was predicted by measuring the sidebands of the two dominant tones. When the mapping of rotational to translational speed of the UUV was known, this method produced speed predictions with 0.004 m/s accuracy. These findings are applicable to many off-the-shelf vehicles available today which rely on brushless DC motors and can be easily integrated into passive acoustic security systems for target motion analysis. [Work supported by the Department of Defense NDSEG program, ONR, and Draper.]

Paper counting display device based on STM32F103 single chip computer

This system uses the STM32F103 single-chip microcomputer as the control center, and the capacitance-to-digital converter FDC2214 collects the current paper value, performs data collection and transmits it to the main control single-chip microcomputer. Methods: Calculate accurate data through Kalman filtering, and accurately calculate and display the number of measured paper sheets on this basis. The device also sets a buzzer to accurately short circuit alarm. The circuit structure of the entire system is simple, and the reliability is high. Results: The system has high precision and fast speed, and can complete the basic requirements and expansion requirements of the problem. Although it is limited by time and venue, it can also have a high reference value for the design of practical applications such as detecting the number of banknotes. Conclusions: Experimental test results show that this design can complete the basic indicators required by the topic and play part of the content. This paper focuses on the hardware design, software design and test result analysis of the system.

Online Compensation of Mechanical Load Defects With Composite Control in PMSM Drives

Online monitoring of various faults that are associated with the permanent magnet synchronous motor (PMSM) is receiving much attention with the increasing demand in PMSM applications. Mechanical load imbalance is one of the mechanical defects that causes increase in the torque ripple, motor vibration, and can lead to accelerated wear and unstable drive operation, if the fault is undetected. Unlike existing methods that are limited to detection of rotor defects, in this article, a novel composite-control scheme is designed to estimate and compensate for the load torque disturbance (produced due to load imbalance) in the feedforward compensation design. It is shown that the proposed design with the feedback control law provides accurate compensation of load torque disturbance and achieves high-precision speed control (improved tracking performance up to 90% and smaller convergence time of up to 70%). Simulations as well as experimental testing validate the effectiveness and reliability of the proposed scheme.

Fabricating THz spiral zone plate by high throughput femtosecond laser air filament direct writing

The sixth-generation wireless communication will exploit the radio band with frequencies higher than 90 GHz, reaching terahertz (THz) band, to achieve huge signal bandwidths. However, the cost-effective fabrication methods of the key components in THz band, which can compromise large scale, high precision, and high efficiency, remain great challenges at present. In this work, we have developed a high throughput fabrication method based on the femtosecond laser filament direct writing. The ability of fabricating large-scale THz elements with high precision and fast speed has been demonstrated by fabricating 100 × 100 mm2 spiral zone plates (SZPs), which can convert the Gaussian THz beam into vortex beam. The performance of the obtained THz vortex beam is in good agreement with the theoretical predictions. The fabrication method reported here has promising applications in fabricating various kinds of THz elements on substrates with both flat and curved surfaces.

Applied Research of Hierarchical Multi-objective Optimization Method in High Speed and High Precision Placement Machine

In practical engineering, placement optimization of multi-head in the high speed and high precision Surface Mount Technology (SMT) is a multi-objective optimization problem. It mainly includes the feeder distribution optimization, the component placement sequence optimization and the nozzle configuration optimization. Optimization problems are complicated and mutual coupling between them. In this paper, the hierarchical multi-objective optimization model is developed. In the hierarchical structure, the nozzle optimization is constructed as a 0-1 integer programming optimization model for the first master hierarchy. In the second hierarchical, component mounting sequence, feeder optimization and picking order are parallel optimized based on the first hierarchy optimization. The respective problems related algorithm strategies have been proposed. The engineering experiments show that this hierarchical multi-objective optimization method can significantly improve the overall performance of the multi-head placement machine with high speed and high precision.

Feeder Layout Optimization and Feeding Sequence Optimization in High Speed and High Precision Placement Machine

As for the multi-optimization mutual coupling process optimization for mounting production with multiple 1210 or1812 resistor components and the relatively low nozzle requirement, a fast multi-objective hierarchical optimization method with low matching requirement for parallel nozzle and placement sequence optimization is proposed. In the hierarchical structure, the nozzle optimization is constructed as a 0-1 integer programming optimization model for the first master hierarchy. In the second hierarchical, feeder optimization and picking order are parallel optimized based on the first hierarchy optimization. The respective problems related algorithm strategies have been proposed. The engineering experiments show that this Feeder layout optimization and Feeding sequence optimization method can significantly improve the overall performance of the multi-head placement machine with high speed and high precision.

Development of real-time prediction module for precision and error of CNC system finishing

High speed and high precision are the important trends in the development of CNC machine tools. In order to improve the machining accuracy of CNC machine tools, the errors of CNC machine tools must be reduced as much as possible. Generally speaking, the errors of CNC machine tools include spatial errors, thermal errors, cutting force errors, tool wear errors, etc., in which spatial errors account for a large part of CNC machine tool errors, so reasonable control of reducing spatial errors is of great significance to improve the accuracy of CNC machine tools. Methods commonly used to reduce spatial errors include error prevention methods and error compensation methods. Error prevention is a method to eliminate and reduce error sources through design, manufacturing, assembly, etc. Although this method can reduce the original error, it is limited by improving manufacturing and assembly accuracy to reduce errors, and it is economically expensive. The error compensation method is to artificially create a new error to offset the current original error to achieve the purpose of improving machining accuracy. This method is easy to implement and has low cost. Therefore, the error compensation method is the most economical and effective method to improve the accuracy of the machine tool.

A Novel Real-Time Fault Diagnosis Method for Planetary Gearbox Using Transferable Hidden Layer

Planetary gearbox with high speed and high precision is important for sophisticated power equipment, and the effective sensor data are necessary for reliability and stability. However, the traditional models for the fault diagnosis of planetary gearbox are difficult to maintain the high accuracy and effectiveness when the amount of training data are scarce. To solve this problem, inspired by deep learning, a novel intelligent method for planetary gearbox fault diagnosis is proposed by utilizing advantage of gated recurrent neural network (RNN) in the feature extraction. Moreover, the dropout technology is introduced to the proposed method to further reduce the requirement of training data. By dividing the parameters of the classification layer and using a few new fault data to fine-tune the learned network parameters, the proposed method can quickly realize the diagnosis of new type faults while maintaining the original recognition ability. Finally, the test signals of the planetary gearbox are used to verify the proposed method. The results show the proposed method has the advantages of high diagnostic accuracy, fast recognition speed, and well real-time in fault diagnosis. Furthermore, the proposed method can make full use of the less information to diagnose different types of faults under the different working conditions.

Hydrochromic CsPbBr3 Nanocrystals for Anti-Counterfeiting.

Hydrochromic materials that can reversibly change color upon water treatment have attracted much attention owing to their potential applications in diverse fields. Herein, for the first time, we report that space-confined CsPbBr3 nanocrystals (NCs) are hydrochromic. When CsPbBr3 NCs are loaded into a porous matrix, reversible transition between luminescent CsPbBr3 and non-luminescent CsPb2 Br5 can be achieved upon the exposure/removal of water. The potential applications of hydrochromic CsPbBr3 NCs in anti-counterfeiting are demonstrated by using CsPbBr3 NCs@mesoporous silica nanospheres (around 100 nm) as the starting material. Owing to the small particle size and negatively charged surface, the as-prepared particles can be laser-jet printed with high precision and high speed. We demonstrate the excellent stability over repeated transformation cycles without color fade. This new discovery may not only deepen the understanding of CsPbX3 , but also open a new way to design CsPbX3 materials for new applications.

Hydrochromic CsPbBr3 Nanocrystals for Anti‐Counterfeiting

AbstractHydrochromic materials that can reversibly change color upon water treatment have attracted much attention owing to their potential applications in diverse fields. Herein, for the first time, we report that space‐confined CsPbBr3 nanocrystals (NCs) are hydrochromic. When CsPbBr3 NCs are loaded into a porous matrix, reversible transition between luminescent CsPbBr3 and non‐luminescent CsPb2Br5 can be achieved upon the exposure/removal of water. The potential applications of hydrochromic CsPbBr3 NCs in anti‐counterfeiting are demonstrated by using CsPbBr3 NCs@mesoporous silica nanospheres (around 100 nm) as the starting material. Owing to the small particle size and negatively charged surface, the as‐prepared particles can be laser‐jet printed with high precision and high speed. We demonstrate the excellent stability over repeated transformation cycles without color fade. This new discovery may not only deepen the understanding of CsPbX3, but also open a new way to design CsPbX3 materials for new applications.

Research on analysis method of dynamic friction torque of high speed precision miniature bearings

High-speed precision miniature bearings are used in the gyro spindle of precision inertial navigators in the aerospace industry. The dynamic friction torque of the bearings is difficult to be accurately analyzed and calculated using existing methods because it is small and has many influencing factors.The special testing machine for dynamic friction torque testing of high-speed miniature bearings is be used to test the dynamic friction torque of specific high-speed precision miniature bearings under various operating conditions. It is related to the speed, axial preload, and radial external load. The test data of bearing dynamic friction torque was obtained. On this basis, the least squares method of regression analysis theory is used to fit polynomial fitting of the dynamic friction torque of the tested bearing and the corresponding working condition parameters, and the regression equation for analyzing the dynamic friction torque of the tested bearing is obtained. The test results show that under different test conditions, the measured values of the bearing’s dynamic friction torque are in good agreement with the calculated values using the regression equation. The obtained regression equation can be used to analyze the dynamic friction torque characteristics of the same bearing under other operating conditions. A reliable and effective method was proposed for quickly and easily obtaining accurate high-speed precision miniature bearing dynamic friction torque.

Gravitational search algorithm based on multiple adaptive constraint strategy

In order to improve the convergence speed and optimization accuracy of gravitational search algorithm, the improved gravitational algorithm with dynamically adjusting inertia weight and trend factors of speed and position is proposed. This kind of algorithm with dynamic inertia weight improves the updating way of particle mass. Moreover, the mass change has a nonlinear decreasing trend and improves the algorithm’s optimization accuracy and convergence speed. At the same time, the speed trend factor and location adaptive factor is introduced, which can dynamically constrain the moving step of each generation of particles according to the number of iterations of the current population. So the algorithm is multi-adaptive. Through classical test function and the CEC2017 benchmark function, the improved algorithm is compared and tested. The theoretical analysis proves the convergence and time complexity of the improved algorithm. Simulation results show that the improved algorithm has a remarkable improvement in terms of optimal performance, high convergence speed and optimization precision.

Experimental and theoretical analysis of ball screw under thermal effect

With the increasing demand for high speed and high precision in the manufacturing industry, the thermal effect of the ball screw has gradually attracted the attention of manufacturing enterprises and scholars. This paper aims at the thermal performance of the ball screw, establishing a quasi-static model and a thermal-mechanical model. On this basis, a calculation scheme considering the dynamic change of boundary conditions is proposed. The proposed scheme can accurately predict the temperature field and thermal error of the ball screw in real-time. Besides, the thermal-induced variations in friction torque and stiffness are measured and identified in a linear feeding test-bed, and the above phenomena are explained and quantitatively predicted based on the coupling analysis.

IJCropSeed: An open-access tool for high-throughput analysis of crop seed radiographs

Optical technologies that are able to analyze physical properties of biological samples are increasingly drawing interest in modern agriculture. The use of X-rays for analysis of internal properties of agricultural products, such as seeds, has proven its worth in providing information regarding their quality in a non-destructive manner. However, visual evaluations of radiographic images are time-consuming, subjective, and highly prone to error. Therefore, it is necessary to develop methods that allow these analyses to be performed in an efficient and assertive manner. To that end, a free-access, open-source, and easy-to-use tool called IJCropSeed has been developed for high-throughput analysis of radiographic images of seeds from several agricultural crops. In addition, an experiment was conducted in which machine learning models were developed from the information obtained from the tool to predict the seed germination capacity and seedling vigor of Crambeabyssinica. The results showed that IJCropSeed had a high performance for the analysis of digital radiographic images of the 24 agricultural crops evaluated, with high speed and high precision of segmentation of the images. The use of parameters obtained with the tool, in combination with the machine learning models, proved to be highly efficient in classifying the quality of C. abyssinica seeds. It is a non-destructive and highly effective method.

Comprehensive effect of multi-parameters on vibration in high-speed precision milling

Precision milling processes have been widely applied to manufacturing parts in fields including automotive, aerospace, and precision machinery. Vibrations created in the milling process contribute significantly to machining accuracy and quality. While the direct and interaction effects of machining parameters on vibration amplitude have been analyzed statistically, the comprehensive effect considering machine tool non-cutting vibrations has not been fully explored. In this paper, the comprehensive effect of several machining parameters on the process vibration is studied and a cutting vibration signal-based optimization method is proposed. First, taking the frequency response function (FRF) and non-cutting rotating vibration into consideration, the spindle speed–related dynamic load in machining is studied to analyze the influence of machining accuracy. The main factors influencing the process dynamic performance are then studied using orthogonal experimental analysis of the vibration signal in milling. Finally, the comprehensive effect is determined and the optimal selection approach of machining parameters is put forward based on the experimental research of vibration in machining processes.

Hyperspectral Inversion of Soil Organic Matter Content Based on a Combined Spectral Index Model.

Soil organic matter (SOM) refers to all carbon-containing organic matter in soil and is one of the most important indicators of soil fertility. The hyperspectral inversion analysis of SOM traditionally relies on laboratory chemical testing methods, which have the disadvantages of being inefficient and time-consuming. In this study, 69 soil samples were collected from the Honghu farmland area and a mining area in northwest China. After pretreatment, 10 spectral indicators were obtained. Ridge regression, kernel ridge regression, Bayesian ridge regression, and AdaBoost algorithms were then used to construct the SOM hyperspectral inversion model based on the characteristic bands, and the accuracy of the models was compared. The results showed that the AdaBoost algorithm based on a grid search had the best accuracy in the different regions. For the mining area in northwest China, = 0.91, = 0.22, and = 0.2. For the Honghu farmland area, = 0.86, = 0.72, and = 0.56. The detection of SOM content using hyperspectral technology has the characteristics of a high detection precision and high speed, which will be of great significance for the rapid development of precision agriculture.