Precise Linear Motion Research Articles

Robust feature design for early detection of ball screw preload loss

The ball screw is a critical device for precision linear motion control that has widespread applications in industrial robots, computer numerical control (CNC) machines, and high-precision leveling systems, among others. Because high-precision positioning is ensured by the addition of a preload to the ball screw system, it is crucial to detect and monitor the loss of preload at the earliest possible stage of degradation. The degradation process of the ball screw can be characterized in two stages: the initial reduction of preload without backlash, followed by a loss of preload with an emergence of backlash. To explore the change of the ball screw dynamics caused by degradation, a novel fixed cycle feature test (FCFT) is implemented in combination with multi-level mass experiments and a run-to-failure (RTF) test. The relationships of the ball screw dynamics with preload, worktable mass, and axis position are investigated, with a focus on the axial natural frequency as an indicator of preload loss. Experimental results validate the axial natural frequency’s role as a reliable early detector of preload loss for interventive use in a prognostic system.

Design of an Intermediate Die for the Multi-Pass Shape Drawing Process.

The multi-pass shape drawing process is mainly used in metal forming processes to manufacture long components with constant arbitrary cross-sectional shapes along their lengths. The cross-roller guide is a typical component that is manufactured by a multi-pass shape drawing process. The cross-roller guide is mostly used in optical measurement equipment where high-precision movement is required. Therefore, the dimensional accuracy of the cross-roller guide is very important since it can influence precision linear motion. However, the unfilled defects can occur in a case where the product has a complex cross-sectional shape. In this study, a new design method for an intermediate die is suggested by using an equal-radial-velocity variation method in order to reduce the unfilled defects. The proposed design method can reduce the unfilled defects by minimizing the radial velocity variation in the deformation zone of the drawing die. The intermediate die was designed by geometrical information of the final product without prior finite element (FE) analysis. The suggested method was applied to design the multi-pass shape drawing process for manufacturing the cross-roller guide. FE analysis was performed to validate the effectiveness of the proposed method in comparison to the conventional design method that uses equipotential lines in the multi-pass shape drawing process. Finally, a shape drawing experiment was performed to compare the target shape and the FE analysis with the experimental data.

Research on High Precision Linear Motor Driving Technology

Aiming at the problem that the output of motor driver driving linear motor is not stable enough and will be accompanied by large power ripple, which makes the motor speed unstable and has a great impact on the accuracy, a linear driver is designed. The AB power amplifier circuit is mainly used by the linear driver to achieve linear output of current, and the negative current feedback is used to stabilize the output current. For the software part, a program based on ARM is designed to parse the commands of the upper computer and control the hardware circuit according to the commands, so as to achieve specific functions. The test results show that the non-linear error of the power amplifier driver is only 3.6%, and the three-phase sinusoidal current with different frequencies and amplitudes can be output as needed.

An Intelligent Hybrid Scheme for Identification of Faults in Industrial Ball Screw Linear Motion Systems

Reliability of high precision linear motion system is one of the main concerns in industrial and military systems. The performance and repeatability of these systems are influenced by their respective linear drives and load bearings. A fault in these members severely affects the safe working of overall system. This paper gives a reliable intelligent approach to detect and classify faults for linear motion systems based on deep learning methods. Accuracy in faults identification is highly dependent on improved features extraction. For this purpose, a novel Residual Twin CNN (ResT-CNN) is proposed that uses combination of 1-D and 2-D CNN in parallel learning which improves features extraction performance; followed by knowledge base-Remnant-PCA (Kb-Rem-PCA) architecture in combination with multi-class support vector machine (Mc-SVM). This novel hybrid combination proved very effective in accurate faults identification. The performance of proposed methodology was also validated by IMS-UC (Intelligent Maintenance Systems - University of Cincinnati) public bearing dataset. The results confirm the effectiveness of proposed scheme in comparison to existing state of the art techniques.

A Novel 2-D Current Signal-Based Residual Learning With Optimized Softmax to Identify Faults in Ball Screw Actuators

Ball screw electro-mechanical actuators are commonly found in high precision motion control applications including aerospace systems as well as automated setups for industries. These actuators perform flight / application critical job and ball screw drives are responsible to provide precise linear motion while carrying thrust loading. A failure in ball screw drive may disturb positioning accuracy of overall system. At present, few techniques are available to monitor electro-mechanical actuators for aerospace and industrial systems. This paper provides a deep learning based intelligent technique to monitor condition of ball screw actuators. The proposed scheme utilizes modified residual learning scheme to extract features from two-dimensional transformed motor current signals. The current signal data was collected under different load domains in terms of magnitude and direction reversal. A 2D-Remanant-CNN (2D-Rem-CNN) model was developed for features extraction with proposed optimized softmax for classification of mechanical faults. The proposed technique was validated against different ball screw fault cases. The testing results prove the superiority of 2D-Rem-CNN model against different state of the art techniques. The proposed framework was also tested for system's stability under different load domains.

A Novel Thrust Force Test Method for a Class of Precision Noncontact Linear Motion Actuators

Precision linear motion is widely used in industrial application. For precision linear motion actuators, ripples of thrust force can deteriorate the driving performance and increase mechanical vibrations. It is very important to precisely test the thrust force of a linear motion actuator. This paper proposes a novel method based on testing reaction force and on the aerostatic method to achieve high-precision and universal testing capability. In this method, the mover and the stator of tested linear motion actuators are suspended by two air-bearing modules. In contrast to traditional testing methods, the force sensor is connected to the stator to avoid the influence of vibration on the sensor. The air-bearing modules eliminate the friction between the stator and the mover, so that it would not affect the results. To validate the strategy, a sample testing platform is manufactured, then a series of experiments is carried out, and the testing performance is compared with that of the traditional method. Experimental results demonstrate the high accuracy achieved by eliminating interferences due to friction and the vibration of the force sensor.

Characterization of the sensitivity of piezoelectric resonant pressure/force sensor with a new automatic device

ABSTRACTA fully automated novel apparatus for the characterization of the sensitivity of piezoelectric resonant pressure/force sensor is proposed. The force-frequency effect of piezoelectric resonant sensors is the correlation between the force applied on the crystal resonator and the relative response resonant frequency shift of the resonator to the applied force. The force-frequency effect is closely related to the sensitivity of the pressure/force sensors. The new apparatus has been designed and fabricated to automatically measure the force-frequency relation at different azimuth angles ψ and force sensitivity coefficient Kf m.s/N which relates to parameters such as crystal geometry (diameter, thickness), orientation angle, and force direction (azimuth angle ψ). PI control is utilized for the automated measurement of force-frequency relation in crystal resonator. In addition, a lead screw mechanism is designed to yield precise linear motion of the clamp and minimize the backlash of the moving parts. As a result, the apparatus can automatically apply force on the crystal, measure the corresponding output frequency shift and yield the force-frequency relation graph. It also has a better force resolution and is simpler to adjust for force alignment. Moreover, the measurement time is reduced and the measurement result is more accurate. In order to validate this novel automated loading device, experiment tests on samples have been performed, and a comparison of the experiment outcomes with peers' measurement results shows a good agreement.

Sliding-mode control combined with improved adaptive feedforward for wafer scanner

Abstract In this paper, a sliding-mode control method combined with improved adaptive feedforward is proposed for wafer scanner to improve the tracking performance of the closed-loop system. Particularly, In addition to the inverse model, the nonlinear force ripple effect which may degrade the tracking accuracy of permanent magnet linear motor (PMLM) is considered in the proposed method. The dominant position periodicity of force ripple is determined by using the Fast Fourier Transform (FFT) analysis for experimental data and the improved feedforward control is achieved by the online recursive least-squares (RLS) estimation of the inverse model and the force ripple. The improved adaptive feedforward is given in a general form of nth-order model with force ripple effect. This proposed method is motivated by the motion controller design of the long-stroke PMLM and short-stroke voice coil motor for wafer scanner. The stability of the closed-loop control system and the convergence of the motion tracking are guaranteed by the proposed sliding-mode feedback and adaptive feedforward methods theoretically. Comparative experiments on a precision linear motion platform can verify the correctness and effectiveness of the proposed method. The experimental results show that comparing to traditional method the proposed one has better performance of rapidity and robustness, especially for high speed motion trajectory. And, the improvements on both tracking accuracy and settling time can be achieved.

Modeling and Simulation on Errors of Feed Unit by Considering Change of Force Bearing Point

The linear feed unit is a type of precision linear motion component that is widely used in computer numerical control (CNC) machine tools. The contact stiffness and error influences the performance of the feed unit directly. Thus, investigating contact stiffness and error is important in optimizing the design and improving the performance of the linear feed unit. In this study, the contact mechanics and the deformation of the roller between the roller and rail are analyzed. Calculation model of the contact stiffness and error based on the Hertz theory and multi-body kinematics are established and the change of the contact angle is also considered. Errors and the contact stiffness curve of five directions and the changes of the slope of the stiffness curve after the load increases to a certain size are obtained. The Motion precision errors of The roller linear feed unit are analyzed. The effectiveness of the proposed models on contact stiffness and error is verified through simulation on a specialized test system of the linear feed unit

Components of a Heart Catheter System for High Risk Patients

As late as fifteen years ago the intracardiac catheter was only used for diagnostic purposes. Since then it has also been established as a therapeutic method. The latest studies have shown that the reduction in convalescence that normally follows a catheter-interventional implantation of aortic valves by transcatheter aortic valve implantation is less significant in comparison to that of a cardiac surgery operation. It is expected that such minimal-invasive technologies will grow to a great extent, also helping to reduce socio-economic costs for the European health care system. Patients of higher ages with acquired cardiac defects or children with congenital cardiac defects of heart valves, especially of the pulmonary valve, are currently the main target groups. We present an alternative and optimized mechanism for stent placement and similar therapeutical interventions. This project focuses on the manipulation unit and tube system. It carries out a highly precise and repeatable linear motion. Ergonomic requirements are taken into account. Furthermore a possibility to support the linear motion by minimal strain is presented. The product is designed for disposable applications but is generally also suitable for long-term applications.

Fractional-order generalized principle of self-support (FOGPSS) in control system design

This paper reviews research that studies the principle of self-support U+0028 PSS U+0029 in some control systems and proposes a fractional-order generalized PSS framework for the first time. The existing PSS approach focuses on practical tracking problem of integer-order systems including robotic dynamics, high precision linear motor system, multi-axis high precision positioning system with unmeasurable variables, imprecise sensor information, uncertain parameters and external disturbances. More generally, by formulating the fractional PSS concept as a new generalized framework, we will focus on the possible fields of the fractional-order control problems such as practical tracking, U+03BB -tracking, etc. of robot systems, multiple mobile agents, discrete dynamical systems, time delay systems and other uncertain nonlinear systems. Finally, the practical tracking of a first-order uncertain model of automobile is considered as a simple example to demonstrate the efficiency of the fractional-order generalized principle of self-support U+0028 FOGPSS U+0029 control strategy.

A Novel Continuum Manipulator Design Using Serially Connected Double-Layer Planar Springs

There is a surge of research interest in the field of “continuum robotics.” Robots created under this paradigm offer many advantages and represent unique features in terms of flexibility, dexterity, safety, and weight reduction. This paper introduces a novel continuum manipulator that integrates multiple layers of compliant planar springs—a structure that provides several notable advantages over existing designs. First, it possesses precise linear large-displacement motion. In this context, we utilize the linear output motion of each layer of springs. With the serial connection of multiple conjoined layers, the manipulator demonstrates linear predictable bending even when executing large bends. An analytical method is provided to study the compliance characteristics of the planar spring and derive the compliance matrix to represent the force–deflection relationships, allowing an accurate motion prediction. Second, compared with work elsewhere, this structure demonstrates an effective way of decoupling bending from contraction and expansion. It reduces the uncontrolled compression when generating normal deflections, thus controlling robot bending is simplified. Third, the reachable workspace of the end effector is enlarged by means of varying the length of the continuum manipulator via controlled contraction and expansion. A 3-D printed prototype of this continuum manipulator is experimentally evaluated. The conducted experiments demonstrated validity of our approach.

Development and Precise Positioning Control of a Novel Linear Motor

A Novel Two-Phase Brushless Tubular Linear Motor And Its Precise Positioning Control System Are Presented In This Paper. The Magnetic Field Distribution In The Air Gap Of The Linear Motor Is Trapezoidal With Optimization By Halbach Magnet Array, And An Ironless Structure Is Adopted To Eliminate Force Ripples. A Simple And Practical Controller Called Active Disturbance Rejection Controller Is Used To Implement Positioning Control Of The Linear Motor Prototype, Which Is Affected By Parameter Uncertainties And Friction. Simulation And Experimental Results Show That The Position Step Response Is Smooth And Micrometer Positioning Accuracy Is Achieved Without Significant Overshoot Or Oscillation. It Can Be Concluded That The Proposed Linear Motor Is Suitable For Smooth And Precise Linear Motion Applications.

Electric Machine Technology Needs Analysis of the Linear Motor

This article is in view of the linear motor aspects of application development in the field of electric machine tool equipment technical requirements analysis, linear motor with its high speed and high acceleration transmission has been in processing center, CNC milling machine, lathe, grinding machine, compound machine, laser is widely used in machine tools and heavy machine tool, in the aerospace, automotive, mold, energy, general machinery in areas such as plays a special role. Linear motor has precise control test system, reasonable matching of the technical indicators, to make it on the electric machine driven by linear motor can realize stable precision mobile and linear motor used for electric spark machine tool is another innovative application achievement of the modern advanced manufacturing industry. Domestic electric machine mostly adopts five axis NC gear rack drive control system, using the linear motor drive control system was still in the stage of research, to promote the linear motor is widely used in the field of electric machine, and the demand analysis.

A square-plate piezoelectric linear motor operating in two orthogonal and isomorphic face-diagonal-bending modes

We report a piezoelectric linear motor made of a single Pb(Zr,Ti)O3 square-plate, which operates in two orthogonal and isomorphic face-diagonal-bending modes to produce precision linear motion. A 15 × 15 × 2 mm prototype was fabricated, and the motor generated a driving force of up to 1.8 N and a speed of 170 mm/s under an applied voltage of 100 Vpp at the resonance frequency of 136.5 kHz. The motor shows such advantages as large driving force under relatively low driving voltage, simple structure, and stable motion because of its isomorphic face-diagonal-bending mode.

Optimization of the cooling system in a double multilayer monochromator

This paper presents the results of heat transfer and deformation analyses of the first of two monochromator crystals installed in a DMM (double multilayer monochromator) for SAXS (small angle X-ray scattering) beamline at the Pohang Light Source (PLS). The DMM was developed to allow precise rotational and linear motion of the crystal. The two crystals have independent driving systems and can be rotated simultaneously, but the first crystal absorbs most of the heat power, so we used the ANSYS program to calculate the temperature distribution and the deformation in the first crystal and in the crystal holder. When the contact geometry between the crystal and the crystal holder is changed, the surface slope error coming from thermal deformation varies. With these analyses of deformation and slope error, an optimized cooling system was designed for the first crystal holder.

그리스 윤활 소형 이송계 마찰력의 이력현상 측정 및 분석

Article history: A precision linear motion table plays a crucial role in manufacturing systems used in various industries such as machine tools, semiconductors, and nanofabrication. In particular, one of the most typical mechanisms for a linear motion table is to use a ballscrew and LM guides. However, this mechanism is inevitably influenced by friction because of the relative motion in its joint regions. One of the most complex phenomena in friction is the hysteresis behavior of dynamic friction, which was compared with the steady dynamic friction that was presented using a Stribeck curve in this study. Therefore, we investigated the dynamic friction and its hysteresis behavior using a miniaturized linear table equipped with a ballscrewand LM guides that were lubricated with grease. Subsequently, it could be seen that hysteresis could be considered a time delay after zero-velocity crossing and that it was influenced by acceleration.

Dynamic workspace control method for underwater manipulator of floating ROV

This paper presents a dynamic workspace control method of underwater manipulator mounted on a floating ROV (Remotely Operated vehicle) in undersea. This method is developed for precise linear motion control of a manipulator’s end-effector considering the motion of a floating ROV caused by sea wave. In the proposed method, the motion of ROV is modeled as nonlinear first-order differential equation. For online manipulator control achievement, the position tracking technique based on extended Kalman filter (EKF) and the input velocity compensation technique for differential inverse kinematics solution are applied. In addition, for precise workspace control, the third-order differential inverse kinematics is utilized. In this paper, the proposed method is verified by both experimental data based test of ROV position tracking and simulations of the proposed control method. In these tests, the specification of the KIOST deep-sea ROV Hemire is utilized.

Model for wear prediction of roller linear guides

The roller linear guide is a type of precision linear motion component that is widely used in computer numerical control machine tools. Stiffness and wear directly influence the performance and service life of roller linear guides. Thus, investigating stiffness and wear is important in optimizing the design and improving the performance of roller linear guides. In this study, we analyze the contact mechanics between the roller and raceway and the deformation of the roller. We also establish a calculation model of the contact stiffness based on the Palmgren formula and rigid body dynamics. By using the Archard wear theory, we analyze the wear process of roller linear guides. Furthermore, we develop a calculation model of the displacement of the slider, which is due to the wear loss of the slider's raceway in its reciprocating motion under loading, to predict the wear of roller linear guides. The effectiveness of the proposed models on contact stiffness and wear prediction is verified through simulations and experiments on a specialized test system.

A newly developed rotary-linear motion platform with a giant magnetostrictive actuator

Demands for machining and measuring three-dimensional geometries have recently increased in a variety of industries. In order to meet such demands, it is necessary to develop a compact versatile high performance spindle system. This paper presents a newly developed rotary motion platform combined with a linear motion mechanism driven by a giant magnetostrictive actuator. The developed platform can be characterized by a compact structure, a noncontact structure, and high accuracy. Performance evaluation results confirm that the developed platform provides precise linear motion during rotating.