Dual Linear Motors Research Articles

Research on the Dynamic Characteristics of a Dual Linear-Motor Differential-Drive Micro-Feed Servo System

(1) Objectives: This article presents a dual linear-motor differential drive micro-feed servo system, mainly through the optimization design of the transmission mechanism. Owing to the differential synthesis of the micro feed from the upper and under linear motors, the impact of friction nonlinearity during the ultra-low velocity micro feed is avoided, endowing the system with a lower stable feed speed to achieve precise micro-feed control. (2) Methods: Transmission components of the dual linear-motor differential-drive system are analyzed using the lumped parameter method, and a dynamic model of electromechanical coupling is created, which takes into account nonlinear friction. The motion relationship of the dual linear-motor differential-drive servo feed system is characterized using a transfer function block diagram. (3) Discussions: Through simulation, the differences in response between the linear-motor single-drive system and the dual linear-motor differential-drive system are examined under fixed or variable feeding velocities as well as the impact of varying velocity combinations of dual linear motors on the output speed of the differential drive system. (4) Results: Nonlinear friction factors exert an impact on the feed velocity of both linear-motor single-drive and dual linear-motor differential-drive systems during low-velocity micro feed. However, regardless of the constant or variable speed conditions, the dual linear-motor differential-drive servo system significantly outperforms the linear-motor single-drive system regarding low-velocity micro feed. Our simulation results are basically consistent with engineering practice, thus validating the rationality of the created system models, which paves the ground for the micro-feed control algorithms.

Cross-Coupled Synchronous Control of Dual Linear Motor Servo System Based on Disturbance-Assignment Observer and Iterative Learning Control

Cross-Coupled Synchronous Control of Dual Linear Motor Servo System Based on Disturbance-Assignment Observer and Iterative Learning Control

Research on the Precision Measurement Method of Flat Screen Gap Based on Mobile Vision

In view of the problem that the measurement accuracy of screen gaps is affected by the R region of the transition rounded corner of the large-size flat back cover, a mobile vision system with dual linear motor synchronous drive is designed to realize precise positioning of monocular vision in 16 local image acquisition positions set in the R region. Full-size measurement of the R region is achieved using local information fusion to accurately measure the screen gap. First, to solve the problem of edge breaking and the blurring of local images, a region extraction and segmentation method based on block statistics is proposed to quickly obtain accurate outer edges. Then, an adaptive Hough line detection method based on dichotomy is proposed to accurately locate the outer edges. The experimental results show that the accuracy of region extraction and segmentation is up to 99.68% within 60 ms; the angle error and position error of line detection are less than 0.01° and 0.2 pixels, respectively. With optimal anti-interference performance, the proposed algorithm realizes the adaptive and accurate positioning of the outer edge within 200 ms; the measurement time and the measurement error of the measurement system are less than 6.0 s and 0.03 mm, respectively.

The Emirates Mars Mission (EMM) Emirates Mars InfraRed Spectrometer (EMIRS) Instrument

The Emirates Mars Mission Emirates Mars Infrared Spectrometer (EMIRS) will provide remote measurements of the martian surface and lower atmosphere in order to better characterize the geographic and diurnal variability of key constituents (water ice, water vapor, and dust) along with temperature profiles on sub-seasonal timescales. EMIRS is a FTIR spectrometer covering the range from 6.0-100+ μm (1666-100 cm−1) with a spectral sampling as high as 5 cm−1 and a 5.4-mrad IFOV and a 32.5×32.5 mrad FOV. The EMIRS optical path includes a flat 45° pointing mirror to enable one degree of freedom and has a +/- 60° clear aperture around the nadir position which is fed to a 17.78-cm diameter Cassegrain telescope. The collected light is then fed to a flat-plate based Michelson moving mirror mounted on a dual linear voice-coil motor assembly. An array of deuterated L-alanine doped triglycine sulfate (DLaTGS) pyroelectric detectors are used to sample the interferogram every 2 or 4 seconds (depending on the spectral sampling selected). A single 0.846 μm laser diode is used in a metrology interferometer to provide interferometer positional control, sampled at 40 kHz (controlled at 5 kHz) and infrared signal sampled at 625 Hz. The EMIRS beamsplitter is a 60-mm diameter, 1-mm thick 1-arcsecond wedged chemical vapor deposited diamond with an antireflection microstructure to minimize first surface reflection. EMIRS relies on an instrumented internal v-groove blackbody target for a full-aperture radiometric calibration. The radiometric precision of a single spectrum (in 5 cm−1 mode) is <3.0×10−8 W cm−2 sr−1/cm−1 between 300 and 1350 cm−1 over instrument operational temperatures (<∼0.5 K NEDelta T @ 250 K). The absolute integrated radiance error is < 2% for scene temperatures ranging from 200-340 K. The overall EMIRS envelope size is 52.9×37.5×34.6 cm and the mass is 14.72 kg including the interface adapter plate. The average operational power consumption is 22.2 W, and the standby power consumption is 18.6 W with a 5.7 W thermostatically limited, always-on operational heater. EMIRS was developed by Arizona State University and Northern Arizona University in collaboration with the Mohammed bin Rashid Space Centre with Arizona Space Technologies developing the electronics. EMIRS was integrated, tested and radiometrically calibrated at Arizona State University, Tempe, AZ.

Research on the process technique of electrical discharge machining based on dual-linear motors

In order to research the electrical discharge machining（EDM） process of the dual-linear motors driving system, in this paper, a dual-linear motor driving spindle structure with balance cylinder is proposed, in which the cross-coupling control algorithm is used to control the dual-linear motors.This structure and control method can improve the thermal balance of the spindle, and availably reduce the influence of the motor heating on the accuracy. In this paper, the method of simulation analysis and positioning detection is applied to verify the effectiveness of the design. Furthermore, the machining ability of dual-linear motors EDM and the ball-screw EDM spindle are compared through efficiency discharging process test and mirror process test. By the comparative results, the dual-linear motors driving technique in EDM filed has higher machining efficiency. The tests results show that the EDM database of the ball-screw EDM spindle can be replaced by dual-linear motors EDM spindle seamlessly. So the dual-linear motors driving technique is suitable for the EDM process.

Nonlinear Synchronous Control for H-Type Gantry Stage Used in Electric Vehicles Manufacturing

The H-type gantry stage (HGS) is widely used in electric vehicle manufacturing and other fields. However, resulting from the existence of mechanical coupling, the synchronous control problem of HGS always troubles many engineers. Most synchronization schemes were either engaged in improving each motor’s tracking performance or committed to pure motion synchronization only. However, tracking and synchronous performance are interconnected, because of the mechanical coupling. In this paper, a rigid assumed system model of HGS, concerning the effects of mid-beam rotary inertia, mid-beam stiffness, and end-effector movement, is presented. Based on the proposed model, an adaptive robust synchronous control based on a rigid assumed model (ARSCR) is proposed to improve both synchronous and tracking performance of the HGS. From the Lyapunov analysis, the proposed ARSCR can achieve the convergence of synchronous error and tracking error, simultaneously. An HGS driven by dual linear motors is built and used to perform the experimental verification. The experimental results indicate the effectiveness of the proposed method.

Detailed Magnetic Force Analysis of A 4-Pole Hybrid Electromagnet by Magnetic Equivalent Circuit Method

In this paper, detailed magnetic force analysis of a 4-pole hybrid electromagnet system providing an advantage of full-redundant levitation is studied. The novel fragmented magnetic equivalent circuit method (MEC) is developed to accurately capture inherited nonlinear characteristics of 4-pole hybrid electromagnet to investigate force characteristics and magnetic field distribution. To confirm this method, two possible scenarios, which are levitation under plain core and levitation under dual-linear motor are composed. As well as, they are examined by both proposed method and FEM analyses. Comparative analyses of both methods revealed that force, inclination torque, and mutual interference can be easily captured with adequate accuracy while at the same time yielding less computation and set up time. Furthermore, the fragmented formulations of permeance functions can be generalized for the analysis and the design of similar devices which specifically involve inclination motions.

Self-tuning cross-coupled two degree-of-freedom PID control for position synchronization of dual linear motors

• Operational principleand dynamic analysisof two kinds of dual linear motors driven stages are discussed. • Aself-tuning cross-coupled two-DOF PIDcontrollerisproposed with synchronous performance and self-tuning mechanism. • An improved artificial bee colonyalgorithm is proposed to tune the control parameters online. • Simulationsand experimentationsof five differentcontrollers are examined and compared. The objective of this study is to propose a self-tuning cross-coupled two degree-of-freedom (DOF) proportional-integral-derivative (PID) control strategy for position synchronization of a dual linear motors (DLMs) driven stage. First, independent one DOF PID (I1PID) control and cross-coupled 1PID (C1PID) control are designed to control the DLMs. Subsequently, independent two DOF PID (I2PID) control and cross-coupled 2PID control (C2PID) are built to further examine the enhanced control performances of the two DOF control systems; the structure of the C2PID control provides improvement over the C1PID in control performance. Nevertheless, it is arduous to tune three main parameters including the proportional gain, the integral time, and the derivative time as well as two compensation parameters including the proportional and the derivative constants. In this regard, a self-tuning C2PID (SC2PID) control is developed in which all the control parameters are dynamically and concurrently optimized through an improved artificial bee colony algorithm. Numerical simulations and experimental results indicate that the proposed SC2PID control exhibits optimal tracking performance with lowest synchronous error when compared with other control schemes.

Intelligent Synchronous Control for Gantry Position Stage

A cross-coupled proportional-integral-derivative neural network (PIDNN) control is proposed in this study for the synchronous control of a dual linear motors servo system which is installed in a gantry position stage. First, the dynamics of the field-oriented control PMLSM servo drive with a lumped uncertainty, which contains parameter variations, external disturbance and friction force, is introduced. Then, to achieve accurate trajectory tracking performance with robustness, an intelligent control approach using PIDNN is proposed for the field-oriented control PMLSM servo drive system. In the proposed approach, the on-line learning algorithms of the PIDNN are derived using back-propagation (BP) method to guarantee the convergence of the network. Finally, some experimental results are illustrated to depict the validity of the proposed control approach.

Research on Contouring Control of Dual Linear Motors

In dual-axis contouring motion, contouring error is a more important performance index than tracking error. Considering direct drive XY table control accuracy, the influence of load disturbance and the velocity mismatch between X and Y axis are great. As a result, the position tracking iterative learning controller based on DOB controller is adopted at single axis, it can overcome the influence of the load disturbance, and ensure the robustness of the system; For the velocity mismatch between X and Y axis, a control strategy based on hybrid error iterative learning control (HILC) and the real-time contour error model was proposed. Simulation results show that the designed control system of XY table has strong robustness, high contour accuracy and simple structure.

Development of miniature Stirling cryocooler technology for Infrared Focal Plane array

A reliable miniature cryocooler is one of the basic and foremost requirements for successful operation of high performance cooled infrared focal plane array (IRFPA) used for defence applications. Technological complexity and requirement of long duration fail-safe operation of the cryocooler demands robust design, fabrication and assembly with tolerances and, perfection of an array of sub-technologies. The paper presents the progress of the development activities in Stirling cryocooler technology at SSPL, which evolved through essential milestones like the development of single and dual piston linear motor driven split coolers to the state-of-the-art integral Brushless DC (BLDC) motor crank-driven type highly miniaturized coolers of capacities ranging from 0.25 to 0.5W at 80K. The theoretical investigations in the design of Stirling cycle cryocooler have been reported and the issues related to the design aspects are discussed in sufficient details. Experimental results of cryocooler performance tests are also presented. The paper also focuses on regenerator design optimization. The results of optimizations have been shown at the end considering a sample data. Defence Science Journal, 2013, 63(6), pp. 571-580 , DOI:http://dx.doi.org/10.14429/dsj. 63.5756

DSP-Based Cross-Coupled Synchronous Control for Dual Linear Motors via Intelligent Complementary Sliding Mode Control

A digital signal processor (DSP)-based cross-coupled intelligent complementary sliding mode control (ICSMC) system is proposed in this paper for the synchronous control of a dual linear motor servo system. The dual linear motor servo system with two parallel permanent magnet linear synchronous motors is installed in a gantry position stage. The dynamic model of single-axis motion control system with a lumped uncertainty, which comprises parameter variations, external disturbances, and nonlinear friction force, is introduced first. Then, to achieve an accurate trajectory tracking performance with robustness, a cross-coupled ICSMC is developed. In this approach, a Takagi-Sugeno-Kang-type fuzzy neural network estimator with accurate approximation capability is implemented to estimate the lumped uncertainty. Moreover, since a cross-coupled technology is incorporated into the proposed intelligent control scheme for the gantry position stage, both the position tracking and synchronous errors of the dual linear motors will simultaneously converge to zero. Furthermore, to effectively demonstrate the control performance of the proposed intelligent control approach, a 32-b floating-point DSP-based control computer is developed for the implementation of the proposed cross-coupled ICSMC system. Finally, some experimental results are illustrated to show the validity of the proposed control approach.

Synchronized Control of Dual Linear Motors Position Servo System Based on Multi-Axes Motion Control Card

This paper introduces a position synchronized control strategy to deal with the synchronous error caused by the external disturbance in dual linear motors servo system. In order to achieve satisfactory results, a new control scheme combing feedforward control, feedback control and cross-coupled control is proposed and makes progress in decreasing the synchronous error which was shown by the experiment.

DSP-based synchronous control of dual linear motors via Sugeno type fuzzy neural network compensator

A digital signal processor (DSP)-based complementary sliding mode control (CSMC) with Sugeno type fuzzy neural network (SFNN) compensator is proposed in this study for the synchronous control of a dual linear motors servo system installed in a gantry position stage. The dual linear motors servo system comprises two parallel permanent magnet linear synchronous motors (PMLSMs). The dynamics of the single-axis motion system with a lumped uncertainty which contains parameter variations, external disturbances and nonlinear friction force is briefly introduced first. Then, a CSMC is designed to guarantee the precision position tracking requirement in single-axis control for the dual linear motors. Moreover, to enhance the robustness to uncertainties and to eliminate the synchronous error of dual linear motors, the CSMC with a SFNN compensator is proposed where the SFNN compensator is designed mainly to compensate the synchronous error. Furthermore, to increase the control performance of the proposed intelligent control approach, a 32-bit floating-point DSP, TMS320VC33, is adopted for the implementation of the proposed CSMC and SFNN. In addition, some experimental results are illustrated to show the validity of the proposed control approach.

Hybrid Fuzzy PID Control for Synchrodrive System of Dual Linear Motors

In this paper, a synchrodrive scheme for dual linear motors position servo system in gantry moving type milling machine is presented. The feedforward control, disturbance observer and electrical cross coupled control algorithm based on fuzzy PID are applied to the position servo system to counteract the influence of mechanical coupling rapidly, and then meet dynamic synchronized performance in machining. From the simulated, the results show that the proposed control method is effective and yield superior performance.

Digital signal processor-based cross-coupled synchronous control of dual linear motors via functional link radial basis function network

A digital signal processor-based cross-coupled functional link (FL) radial basis function network (FLRBFN) control is proposed in this study for the synchronous control of a dual linear motors servo system that is installed in a gantry position stage. The dual linear motors servo system comprises two parallel permanent magnet linear synchronous motors (PMLSMs). First, the dynamics of the field-oriented control PMLSM servo drive with a lumped uncertainty, which contains parameter variations, external disturbance and friction force, is introduced. Then, to achieve accurate trajectory tracking performance with robustness, an intelligent control approach using FLRBFN is proposed for the field-oriented control PMLSM servo drive system. The proposed FLRBFN is a radial basis function network embedded with a FL neural network. Moreover, to guarantee the convergence of the FLRBFN, a discrete-type Lyapunov function is provided to determine the varied learning rates of the FLRBFN. In addition, since a cross-coupled technology is incorporated into the proposed intelligent control scheme for the gantry position stage, both the position tracking errors and synchronous errors of dual linear motors will converge to zero, simultaneously. Finally, some experimental results are illustrated to depict the validity of the proposed control approach.

Dynamics Analysis of a Parallel Mill-turn Tool Spindle Head Driven by Dual-linear Motors Using Extended Transfer Matrix Method

The hybrid dynamics of multi-rigid-body and multi-flexible-body system becomes the mainstream of multi-body dynamics.Currently there lacks a compact approach to model the hybrid dynamics,especially in modern machine tool application,due to the difficulty of solving the hybrid equations or the limitation of current software when dealing with the hybrid dynamics.The extended transfer matrix method(E-TMM),which extends elements in three-dimensional space with higher matrixes,is proposed to simplify the modeling process of the hybrid dynamics.The E-TMM modeling approaches of 3 basic elements including 3D vibrant rigid body,joint and flexible body are studied in details.A parallel mill-turn tool spindle head unit driven by dual-linear motors is chosen as a plant to demonstrate the E-TMM modeling process.By using E-TMM,the spindle head unit is simplified as a topological network consisting of the three types of element,i.e.,3D vibrant rigid body,joint and flexible body,including 11 rigid bodies,14 joints and 1 3D-Timoshenko beam.Then the dynamic model of the system can be easily obtained by deducing the element-network by means of state vector transformation.The dynamic characteristics of the spindle head,such as natural frequencies,dynamic flexibility,etc.can be predicted by solving the obtained model.Experiment verification indicates that the E-TMM is valid with enough accuracy in the dynamic analysis of the parallel mill-turn tool spindle head.The E-TMM is capable of modeling the dynamics of machine tool structure with no requirements of deducing and solving the sophisticated differential equations.Moreover,the E-TMM provides a simple and elegant tool for hybrid dynamic analysis in future dynamic design of machine tools.

Novel Jump Control for Debris Processes of Electrical Discharge Machining with Direct-Drive Spindle

Owing to its low removal rate and debris ejection nature, EDM is a very slow machining process. A novel jump motion control for electrode in electrical discharge machining (EDM) equipped with dual linear motors (LmEDM) was proposed to release this debris efficiency point. The direct drive EDM and a novel pulse discriminator were developed. By introducing the discriminator to count effective discharge pulses, an EDM jump control was proposed. Experiments for verification of the EDM efficiency were conducted for 35 mm deep and thin EDM processes with 2 mm thin platelet. EDM efficiency of proposed jump control is verified to be four times over the traditional EDM.

Tracking control for a synchronized dual parallel linear motor machine tool

This paper analyses and compares several different synchronized controllers and motion command schemes, and implements them using a PC-based gantry-type machine tool. First, an integral-proportional (IP) controller and a proportional controller are applied to the velocity and position loop of a single-axis system respectively. The tracking control accuracy of the motor is advanced by the fastened response and improved lag. Next, for the dual-axis synchronized system, the equation of the cross-coupled controller (CCC) parameters can be acquired by analysing the tracking error and the synchronized error of the dual linear motors. The equation can be further applied to integrate the synchronized motion and reduce the synchronized error. The experiment results have proved these theories to be successful in reducing synchronized error and realizing the performance demand of tracking control.

Servo design of a vertical axis drive using dual linear motors for high speed electric discharge machining

This paper proposes a synchronous control scheme for a linear servo system applied to the vertical axis drive of a die-sinking electric discharge machine (EDM) tool. The investigated vertical axis drive is constructed with dual parallel linear motors, which are arranged to jointly drive the feed axis for improvement of the overall thrust and structural stiffness. A pneumatic cylinder is employed to compensate the gravitational effect of the feed axis with its electrode and holder. A mechanical coupling is designed to firmly bridge the two linear motors and carry the feed axis. Therefore, synchronous control for the motors is critical for not only position accuracy, but also machine safety. Moreover, by controlling the thrust outputs and positions of the motors to be as equal as possible, the potential “pull and drag” effect between the motors can be reduced and loads can also be equally shared. The proposed “position/thrust hybrid synchronous control” scheme is applied to the EDM to achieve high-speed, accurate machining, and the experimental results show that the synchronization error between the two parallel motors and the positioning accuracy are both satisfactory when operated under high-speed conditions.