High-precision System Research Articles

Design and implementation of speed fluctuation reduction for a ball screw feed system at low-speed operation

Abstract. In the high-precision servo feed system, when the permanent magnet synchronous motor (PMSM) is operated at low speed in the classical drive feed system (CDFS), the speed fluctuation caused by the motor torque harmonics seriously affects the speed smoothness of the servo system. In this paper, a novel double-drive differential feed system (DDFS) is proposed to effectively suppress the effect of torque harmonics of PMSM on speed fluctuation of the linear feed system at low-speed operation. Firstly, the effect of motor torque harmonics on motor speed for the DDFS is analyzed by the sensitivity function of the servo system, which indicates that the torque harmonics have little effect on the motor speed at high-speed operation. Then, in the DDFS, we make two motors rotate in the same direction at high speed and differentially synthesize at the ball screw to obtain low-velocity linear motion. Compared with the CDFS, the DDFS can suppress the effect of motor torque harmonics on speed fluctuation of the table and improve speed smoothness at low-speed operation.

Comprehensive Temperature Control of a Hot Metal Rolling Thickness Measurement System

The work is devoted to the development of integrated thermostating subsystem of a high-precision system for measuring the thickness of hot metal rolling. The developed thermostatting subsystem includes active and passive modules, which ensured thermostability of the measuring modules at the level of 0.5 degrees in a hot metallurgical workshop. Thermal stabilization made it possible to ensure high accuracy in measuring the thickness of hot metal rolling in a hot metallurgical production workshop.

Stochastic Estimation of Orientation Parameters of an Antenna Complex based on Strapdown Inertial System Measurements

The problem of high-precision determination of the spatial orientation of the antennas of radio complexes located on high-rise masts of various designs is considered. It is established that the methods currently used, based on measurements of satellite navigation systems and autonomous measurements of strapdown inertial orientation systems, do not provide the required accuracy in solving the problem. It is shown that the low accuracy of existing methods is due to both weak noise immunity of information processing algorithms and the lack of the ability to take into account the dynamic properties of orientation parameters measured under conditions of high intensity interference, the properties of which, as a rule, are not taken into account. A dynamic algorithm is proposed for estimating the stochastic orientation parameters of the antenna of a radio complex, which is invariant to the nature of the movement of the mast base and provides stability and the required estimation accuracy under general assumptions about the nature of the interference of the sensitive elements of the strapdown inertial orientation system. The Rodrigue–Hamilton parameter vector was used as the observed state vector – the antenna orientation parameter vector – and the vector of measurements of the angular velocity sensors of the strapdown inertial system was used as the observation vector for it. The instrumentation of the strapdown inertial system includes three accelerometers and three angular velocity sensors located orthogonally at the center of mass of the antenna. Based on the obtained non-linear stochastic equations for the dynamics of the change in the parameter vector of the current orientation of the strapdown inertial orientation system on a moving base and the equations of their observation, a stochastic model of measurement signals for sensitive elements of the strapdown inertial orientation system, a non-linear (generalized) Kalman filter is constructed that provides the desired solution to the problem of estimating the parameters of the current antenna orientation on a perturbed base. We present the results of a numerical experiment and a conclusion about the possibility of using a fi lter to solve the problem of operational orientation of antennas of radio engineering complexes using medium- and high-precision strapdown inertial orientation systems and without correction over a long time.

Modular Current Stimulation System for Pre-clinical Studies.

Electric stimulators with precise and reliable outputs are an indispensable part of electrophysiological research. From single cells to deep brain or neuromuscular tissue, there are diverse targets for electrical stimulation. Even though commercial systems are available, we state the need for a low-cost, high precision, functional, and modular (hardware, firmware, and software) current stimulation system with the capacity to generate stable and complex waveforms for pre-clinical research. The system presented in this study is a USB controlled 4-channel modular current stimulator that can be expanded and generate biphasic arbitrary waveforms with 16-bit resolution, high temporal precision (μs), and passive charge balancing: the NES STiM (Neuro Electronic Systems Stimulator). We present a detailed description of the system’s structural design, the controlling software, reliability test, and the pre-clinical studies [deep brain stimulation (DBS) in hemi-PD rat model] in which it was utilized. The NES STiM has been tested with MacOS and Windows operating systems. Interfaces to MATLAB source codes are provided. The system is inexpensive, relatively easy to build and can be assembled quickly. We hope that the NES STiM will be used in a wide variety of neurological applications such as Functional Electrical Stimulation (FES), DBS and closed loop neurophysiological research.

A Novel Subarray Digital Modulation Technique for Wideband Phased Array Radar

A novel wideband digital array radar system is introduced in this article. The system has an open software-based processing architecture that provides a high degree of digitization and a flexible processing mode that employs digital stretch processing and digital modulation techniques to solve the beam divergence problem caused by the wide-angle scanning of both broadband and wideband array radar. The system simultaneously realizes a large range window, a wide dynamic range, and interpulse coherence for wideband array radar. The system is applicable not only to wideband linear frequency modulated (LFM) signals but also to wideband nonlinear frequency modulated (NLFM) signals. An engineering implementation scheme is also introduced. Key techniques, including wideband waveform generation, low data rate transmission, high-precision digitally modulated time-delay compensation, and high-precision system synchronization, are described in detail. In addition, an X-band experimental system is constructed, and the performance of this system is verified using typical target detection experiments.

Diamond Inclusion Reconstruction

In this paper, we make an improvement on the conventional visual hull reconstruction method that runs on a single consumer graphics card. The target application is a high-precision diamond inclusion reconstruction system. One major contribution of this paper is an evaluation system of voxels for high-precision reconstruction. In contrast to existing approaches, it allows us to reconstruct the thin structure of the diamond inclusion. Based on this, we obtain a significant improvement in reconstruction precision, especially for thin inclusion.

Finite-Time Control for Piezoelectric Actuators With a High-Order Terminal Sliding Mode Enhanced Hysteresis Observer

Piezoelectric actuators (PZTs) are essential elements in high-precision systems. However, the hysteresis nonlinearity introduced by PZTs degrades the control accuracy. In this paper, a high-order terminal sliding mode enhanced hysteresis observer is designed, which compensates the error between the Bouc-Wen model and the actual hysteresis. Subsequently, a novel terminal sliding mode control (TSMC) is proposed. Unlike the conventional TSMC, the novel TSMC method makes the tracking error in the sliding mode converge to the origin within a finite time regardless of the initial conditions, which improves the performance of conventional TSMC. The stability of the proposed control method is verified through the Lyapunov theory. Finally, simulations and experiments are implemented to validate the effectiveness of the proposed control method. Experimental results demonstrate that the proposed method has a more superior performance than conventional TSMC.

A novel two-input asymmetric dynamic cross-coupled hysteresis modeling and identification for piezoelectric stack actuators

Piezoelectric Stack Actuators (PEAs) have been widely used in high-precision positioning system because of its fast response. However, under different excitation voltages and external loads with dynamic frequencies, the width and inclination of PEAs hysteresis curves verified correspondingly, and exhibit asymmetry phenomenon. The main contribution of this paper is to present a two-input asymmetric dynamic cross-coupled hysteresis (TADCH) model to describe the complex nonlinear hysteresis of PEAs in dynamic excitation and loading engineering applications. Moreover, we also develop the corresponding identification method of TADCH model. Finally, several experiments are carried out to verify the accuracy of the proposed model.

Применение подводных пассивных ориентиров для навигации автономных необитаемых подводных аппаратов

The article describes the design of passive underwater landmarks (PUL) and their use for navigation of autonomous unmanned underwater vehicles (AUV). The procedure of AUV observation using PUL is considered. It is shown that with proper maneuvering of the AUV during observation, the accuracy of determining its coordinates is limited only by the accuracy of the PUL positioning during installation. This accuracy also affects the distance between neighboring PULs installed along the AUV’s route. If the AUV is equipped with a high-precision autonomous navigation system, the PULs can be installed at the intervals of several hundred kilometers.

Unapređenje metoda vibro-akustične kontrole mehanizma za distribuciju gasa kod SUS motora

A modern vehicle is a system of high-precision systems. In particular, over the past 20 years, the gas distribution mechanism (GRM) has been structurally released from any adjustments. However, alongside with that, the elimination of the adjustments did not entail a decrease in the number of GDM failures. The analysis of a number of works shows that the GDM mechanism accounts for more than 30% of ICE failures. The problem lies in the high sensitivity of modern engine systems to the oil drain interval, fuel quality, timeliness of maintenance, etc., i.e. to carrying out of routine activities. According to the analysis of the operating conditions of modern vehicles, the regulations are significantly violated in more than 50% of cases, which results is a considerable reduction in the service life of vehicles. In this connection, it is relevant to develop diagnostic methods allowing us to determine the degree of wear of engine components at all vehicle operation stages. One of such methods is the vibro-acoustic method. The research aims to develop a methodology and method for diagnosing GRM by analyzing vibration parameters together with a pressure signal in the cylinder, the angle of the ICE crankshaft. As a result, the mechanism for recognizing the fault conditions of individual GRM valves is determined. A set of diagnostic tools for the selective diagnosis of GRM elements has been developed. A methodology for determining the GRM phases and thermal clearances in the valve drive using the nondemountable method has been created.

Peak Filter Tuning based on Disturbance Spectrum for MIMO High-Precision Scan Stage

In high-precision positioning systems such as scanning machines, the feedback controller tuning needs a lot of time and skills. In particular, a feedback controller tuning with six-degree-of-freedoms (x,y,θz,z,θx,θy) is difficult because of the numbers of controller parameters in each axis. The feedback controllers designed as single-input single-output controllers in each axis may not achieve sufficient performance in multi-input multi-output systems, and stability may not be satisfied because of a coupling problem between each axis. The repetitive disturbance makes the performance worse in a constant velocity scanning motion, and they are conventionally rejected by a peak filter in other applications of high-precision systems such as a hard disk drive. In this paper, we propose a tuning method of a peak filter to suppress a repetitive disturbance which satisfies robust stability conditions for six-degree-of-freedom systems by using convex optimization. The effectiveness of the proposed method is verified by the error in the constant velocity scanning motion.

Improving the realism of a wheelchair simulator through tracking of upper body movements

Introduction Safe and efficient use of a manual wheelchair (MWC) requires appropriate training. New MWC users should learn how to maneuver in different environments (restricted spaces, uneven surfaces, etc.). Learning of appropriate balance skills is also crucial, to avoid falls when handling forward or side slopes. Moreover, long-term MWC use can lead to repetitive shoulder strain injuries, which can be avoided through adequate propulsion technique (increasing push amplitude, while decreasing cadence). We have developed a virtual reality MWC simulator for the training of MWC skills. The velocities of the rear wheels control a virtual MWC in a 3D scene presented on a computer screen in front of the participant, while force feedback simulates the effects of gravity and inertia. Our objective was to improve the realism of our existing wheelchair simulator, through the addition of upper body motion tracking that will provide feedback on trunk posture and propulsion movement. Material and methods Ten MWC users participated in the study. They propelled the virtual MWC while their trunk and arm movements were simultaneously recorded by three systems: – five inertial sensors placed on the trunk, arms and forearms; – a markerless, 3D depth camera system; – a high-precision motion capture system (gold standard). Upper body position as measured by the two low-cost approaches (inertial system and depth camera) was compared to the motion capture system. Results and conclusion Findings from this interdisciplinary study will optimize mobility of MWC users, through better MWC skills (balance and propulsion techniques), while possibly decreasing the incidence of falls and shoulder injuries.

Recurrent-Neural-Network-Based Predictive Control of Piezo Actuators for Trajectory Tracking

Precise trajectory tracking of piezo actuators (PEAs) in real time is essential to high-precision systems and applications. However, the real-time tracking accuracy is rather limited as the PEA cannot be accurately modeled over large bandwidth and displacement range due to its nonlinearities. In this article, we propose to use recurrent-neural-network (RNN) to model the PEA system and develop a nonlinear predictive controller for PEA trajectory tracking. Considering the computation efficiency, first, an RNN is trained to model the nonlinear dynamics of the PEA system at high-frequency range. Then, a second-order linear model is proposed to account for the PEA low-frequency dynamics. Therefore, the PEA dynamics is modeled by the nonlinear model consisting of the RNN and the linear model, which is further used for nonlinear predictive control of the displacement. To increase the prediction accuracy, an unscented Kalman filter is designed to estimate the states of the nonlinear model. The nonlinear predictive control problem is solved based on a gradient descent algorithm, in which a method for analytically calculating the gradient of the cost function is developed. The proposed technique was experimentally implemented on a nano piezo stage for demonstration and its performance was compared with that of a PID controller. The accuracy of an iterative learning control approach was used as a benchmark for comparison as well. The results showed that high precision trajectory tracking of PEAs in real time can be achieved using the proposed technique.

A Triple Checked Partial Ambiguity Resolution for GPS/BDS RTK Positioning.

Reliable and accurate carrier phase ambiguity resolution is the key to high-precision Global Navigation Satellite System (GNSS) positioning and application. With the fast development of modern GNSS, the increased number of satellites and ambiguities makes it hard to fix all ambiguities completely and correctly. The partial ambiguity fixing technique, which selects a suitable subset of high-dimensional ambiguities to fix, is beneficial for improving the fixed success rate and reliability of ambiguity resolution. In this contribution, the bootstrapping success rate, bounded fixed-failure ratio test, and the new defined baseline precision defect are used for the selection of the ambiguity subset. Then a model and data dual-driven partial ambiguity resolution method is proposed with the above three checks imposed on it, which is named the Triple Checked Partial Ambiguity Resolution (TC-PAR). The comprehensive performance of TC-PAR compared to the full-fixed LAMBDA method is also analyzed based on several criteria including the fixed rate, the fixed success rate and correct fixed rate of ambiguity as well as the precision defect and RMS of the baseline solution. The results show that TC-PAR could significantly improve the fixed success rate of ambiguity, and it has a comparable baseline precision to the LAMBDA method, both of which are at centimeter level after ambiguities are fixed.

Determining the Initial Orientation for Navigation and Measurement Systems of Mobile Apparatus in Reforestation

This paper considers the method of determining the initial orientation of the navigation and measuring complexes of mobile objects. The method is based on analytical gyrocompassing, using angular velocity sensors whose measurements are distorted by additive noise, with a priori uncertain statistical characteristics. The proposed approach requires small computational costs and can be effectively used in the development of high-precision systems of initial orientation of navigation–measurement systems of various mobile objects.

Comparator effect on equivalence of results of calibrating current transformers

Many different high-precision systems for determining the ratio error and phase displacement of current transformers have been developed by leading specialists in the world. The latest research solutions with the use of the latest measurement tools, instantaneous sampling techniques, and analysis of sources of uncertainty have been applied in these developments. The objective difficulty is that only a limited number of specialized institutes implement such projects with the involvement of leading experts in the field of measurement and significant funds. First of all, these are the national metrological institutes of countries with high economic opportunities. At the level of conventional calibration laboratories equipped with modern facilities and highly qualified personnel, the uncertainty of measurements increases 10 times or more when calibrating precision instrument transformers. Thus, it has not been investigated to what extent the readouts of commercial comparators of different manufacturers in the calibration of instrument transformers of class 0.2S and more precise are equivalent. Determination of the equivalence level of AC comparators of different types in the day-to-day calibration of current transformers is the main objective of this research. More than 50 comparators of different types (with inductive or resistive current transducers) were investigated relative to 2 well-characterized reference current transformers. Comparison of the results obtained by two instruments with radically different principles of measurement gave a difference of 23 μA/A in ratio error and 52 μrad in phase displacement. The results of estimating the readout stability of modern comparators of serial production are also highlighted. The results of the analysis of the data obtained allow us to assume that measurement results of ratio error of about 50 μA/A have equivalence level within ±20 μA/A. The measurement results of phase displacement of about 50 μrad have equivalence level within ±15 μrad. Concerning the determination of metrological characteristics of current transformers with accuracy class 0.2S, their equivalence must be considered taking into account all exploited comparators. The results cause the question about the adequacy of the accuracy margin of the current transformer in the production to overlap the difference in the readouts of 260 μA/A and 500 μrad

Comparative Analysis among Single-Stage, Dual-Stage, and Triple-Stage Actuator Systems Applied to a Hard Disk Drive Servo System

In modern times, the design and optimization of different actuator systems for controlling a high-precision position control system represent a popular interdisciplinary research area. Initially, only single-stage actuator systems were used to control most of the motion control applications. Currently, dual-stage actuation systems are widely applied to high-precision position control systems such as hard disk drive (HDD) servo systems. In the dual-stage system, a voice coil motor (VCM) actuator is used as the primary stage and a piezoelectric micro-actuator is applied as the secondary stage. However, a dual-stage control architecture does not show significant performance improvements to achieve the next-generation high-capacity HDD servo system. Research continues on how to fabricate a tertiary actuator for a triple-stage HDD servo system. A thermal positioning controller (TPC) actuator is considered promising as the tertiary stage. The triple-stage system aims to achieve greater bandwidth, track density, and disk speed, with minimum sensitivity and greater error minimization. In this work, these three actuation systems with different combinations of proportional plus integral (PI), proportional plus derivative (PD), and proportional plus integral plus derivative (PID) controller, lag-lead controller, lag filter, and inverse lead plus a PI controller were designed and analyzed through simulation to achieve high-precision positioning. The comparative analyses were done on the MATLAB/Simulink simulation platform.

Three-dimensional image-based approach for imperfect structures surface modeling

Great attention has been given, in the scientific literature, to the effect of initial imperfections on the structural behavior of experimental samples under compression loads. Geometrical reconstruction of the as-built surface is therefore required to allow accurate numerical modeling. High-precision systems for inverse engineering are expensive, and most of the times geometrical imperfections are rather complex to be described without high computational efforts. In this paper, an image-based approach to model the surface of imperfect structures using open-source software and a common digital camera is presented. The proposed approach aims to generate high-quality surfaces from real imperfect structures, by employing the surface-from-motion and multi-view stereo techniques. A controlled frame capture is introduced to decrease both the computational effort and number of repeated correspondences. The surface fit is then computed by meshing the dense cloud of points and adjusting several surface regions describing the samples’ profiles. The procedure is illustrated by using two damaged tubular member samples reconstructed by the proposed approach. Then, resulted geometries are verified by comparing measures from a three-dimensional high-precision laser scanner and a common mechanical procedure. Finally, a comparison of three-dimensional mappings of a ship panel with proposed approach and commercial photogrammetry software is performed. Verification results refer to the possibility of prototyping geometry surfaces from real imperfect samples by using inexpensive hardware and public domain software tools with acceptable level of accuracy.

Design and experiment of noncontact eddy current damping module in air bearing–guided linear motion system

As a method for reducing the friction of high-precision system, air bearings have been widely used for various industrial applications. However, their small damping leads to poor in-position stability and therefore systems are susceptible to residual vibration and disturbance. In this study, a linear motion stage which is guided by air bearing for a noncontact eddy current damping module is proposed. The eddy current damping module consists of a Halbach array of permanent magnets and a fixed conductor plate. An eddy current is generated in the conductor in the direction opposing the change in the magnetic field when the magnets move, after which the resistivity in the conductor dissipates the kinetic energy of the moving part; therefore, the module has a damping effect without contact and system is shown good in-position stability. In order to specify the damping effect, the motion of the moving part was experimentally analyzed. The step response confirmed that the eddy current damping module can improve the performance of the positioning system: the settling time decreased by 36.8% and the resolution improved by 59.4%. These improvements verify that eddy current damping is a suitable method for application in precision industries.

Design & implementation of a high precision & high dynamic range power consumption measurement system for smart energy IoT applications

Internet of Things (IoT) devices have strict necessity for power consumption in order to achieve expected battery life. IoT nodes feature extreme power consumption range over 100 dB, between their operating modes. The main focus of this paper is to design and implement a high precision, high dynamic range, low power, and flexible power measurement system, which can be applied to different applications. The proposed system consists of a voltage regulating control loop, zero offset amplifiers, high precision analog to digital converters, and reference voltage. The proper operation of the proposed circuit are verified numerically with simulations and experimental measurements. The implemented system features maximum sampling rate of 5 MHz, load regulation error of 0.16%, and linearity error of 0.32%. It is expected that the proposed system provides clear information of power behavior of IoT devices, which can be used for network’s power optimization as well as a self-power test equipment.