Linear Slide Research Articles

Optimized Control of 3DOF Variable Stiffness Link Manipulator Using Feedback Linearization PD and Sliding Mode Approaches

Purpose: This study focuses on the control of a 3-degree-of-freedom (3DOF) variable stiffness flexible links manipulator, employing diverse control techniques to address the challenges associated with its inherent structural flexibilities. Variable Stiffness Link (VSL) manipulators offer enhanced adaptability and safety in various applications by dynamically adjusting their link stiffness. This feature allows them to optimize performance for different tasks, from delicate operations to robust industrial use. However, the variable stiffness introduces complex nonlinear dynamics, significantly complicating precise control and necessitating advanced control strategies. Methodology: The research investigates two advanced control methods: linearized feedback proportional-derivative (PD) control and sliding mode control (SMC). These techniques are employed for both position and trajectory control of the system, aiming to maintain precise joint angles while minimizing oscillations in the end effector. The controller designs for both linearized feedback PD and sliding mode control are presented, including stability analyses using Lyapunov theory. Experimental work is conducted to evaluate the effectiveness of both control strategies. Findings: The results demonstrate that both controllers achieve satisfactory performance in managing the complex dynamics of the flexible link system. The linearized feedback PD controller shows good tracking capabilities across the three joints while the sliding mode controller exhibits superior performance. Comparative analysis reveals that while both controllers effectively maintain stability and achieve precise trajectory tracking, the sliding mode controller displays marginally better performance in terms of steady-state errors and robustness to system nonlinearities. Unique contribution to theory, policy and practice: This research contributes to the advancement of control techniques for flexible manipulators, offering promising solutions for improving the performance and reliability of this manipulator for automation applications.

Compound Control Design of Near-Space Hypersonic Vehicle Based on a Time-Varying Linear Quadratic Regulator and Sliding Mode Method

The design of a hypersonic vehicle controller has been an active research field in the last decade, especially when the vehicle is studied as a time-varying system. A time-varying compound control method is proposed for a hypersonic vehicle controlled by the direct lateral force and the aerodynamic force. The compound control method consists of a time-varying linear quadratic regulator (LQR) control law for the aerodynamic rudder and a sliding mode control law for the lateral thrusters. When the air rudder cannot continuously produce control force and torque, the direct lateral force is added to the system. To solve the problem that LQR cannot directly obtain the analytical solution of the time-varying system, a novel approach to approximate analytical solutions using Jacobi polynomials is proposed in this paper. Finally, the stability of the time-varying compound control system is proven by the Lyapunov–Krasovskii functional (LKF). The simulation results show that the proposed compound control method is effective and can improve the fast response ability of the system.

Comparison of the Application of Linear Regression with Sliding Window Validation and K-Fold Cross-Validation for Forecasting Covid-19 Recovered Cases

The increase in confirmed cases and deaths due to Covid-10 continues to spread and increase day by day throughout the world. This has resulted in a world health crisis that impacts all sectors of life. The government declared a movement to suppress the spread of Covid-19, so it is necessary to understand the pattern of Covid-19 problems. Researchers contribute scientifically to finding patterns of death or recovery due to COVID-19 by applying Machine Learning methods. The Linear Regression and Sliding Window preprocessing methods are appropriate for forecasting time series data. This research obtained RMSE results at 0.320 with linear regression with sliding window validation and RMSE at 0.320 with linear regression with K-Fold cross-validation. This proves that Linear Regression with Sliding Window Validation can improve performance much better than k-fold cross-validation in forecasting COVID-19 recovery cases in China. The sliding window validation method has been proven to increase accuracy for forecasting with time series data compared to other standard preprocessing methods, namely K-Fold cross-validation. In the future, further research is needed to test different types of time series data by comparing the application of sliding window validation and K-Fold cross-validation or developing other validation models.

Implementation of a motion planning technique for a low-frequency piezo-actuated inchworm drive

A novel piezoelectric inchworm drive capable of long-range motion has been designed, fabricated, and tested in this research work. To control the motion of the inchworm drive, trajectory planning has been proposed. The trajectory planning ensures that the inchworm drive achieves smooth and continuous motion with high accuracy. Two trajectory planning methods were incorporated for the developed inchworm drive: a linear function with a parabolic blend trajectory and a cubic polynomial trajectory. Simulations for both the cubic polynomial and trapezoidal trajectories were conducted, with the estimated displacement results closely verified through experimental validation. The fabricated inchworm drive is tested for varying input voltages and frequencies. The experimental findings demonstrate that the proposed piezoactuated Inchworm drive can achieve substantial displacement, constrained only by the linear slide’s length. When an input signal of 150 V peak to peak and frequency of 10 Hz is applied to the inchworm drive, it was capable of moving at a speed of 1425 μm/s. When incorporating trajectory planning for the Inchworm drive the experimental results show that the maximum percentage error for the trapezoidal motion profile is 1.56% and the cubic polynomial profile trajectory is within 1% for the corresponding target position for a travel range of 25 mm of the inchworm drive.

High-precision fruit localization using active laser-camera scanning: Robust laser line extraction for 2D-3D transformation

Recent advancements in deep learning-based approaches have led to remarkable progress in fruit detection, enabling robust fruit identification in complex environments. However, much less progress has been made on fruit 3D localization, which is equally crucial for robotic harvesting. Complex fruit shape/orientation, fruit clustering, varying lighting conditions, and occlusions by leaves and branches have greatly restricted existing sensors from achieving accurate fruit localization in the natural orchard environment. In this paper, we report on the design of a novel localization technique, called Active Laser-Camera Scanning (ALACS), to achieve accurate and robust fruit 3D localization. The ALACS hardware setup comprises a red line laser, an RGB color camera, a linear motion slide, and an external RGB-D camera. Leveraging the principles of dynamic-targeting laser-triangulation, ALACS enables precise transformation of the projected 2D laser line from the surface of apples to the 3D positions. To facilitate laser pattern acquisitions, a Laser Line Extraction (LLE) method is proposed for robust and high-precision feature extraction on apples. Comprehensive evaluations of LLE demonstrated its ability to extract precise patterns under variable lighting and occlusion conditions. The ALACS system achieved average apple localization accuracies of 6.9 - 11.2 mm at distances ranging from 1.0 m to 1.6 m, compared to 21.5 mm by a commercial RealSense RGB-D camera, in an indoor experiment. Orchard evaluations demonstrated that ALACS has achieved a 95% fruit detachment rate versus a 71% rate by the RealSense camera. By overcoming the challenges of apple 3D localization, this research contributes to the advancement of robotic fruit harvesting technology.

Active Laser-Camera Scanning for High-Precision Fruit Localization in Robotic Harvesting: System Design and Calibration

Robust and effective fruit detection and localization is essential for robotic harvesting systems. While extensive research efforts have been devoted to improving fruit detection, less emphasis has been placed on the fruit localization aspect, which is a crucial yet challenging task due to limited depth accuracy from existing sensor measurements in the natural orchard environment with variable lighting conditions and foliage/branch occlusions. In this paper, we present the system design and calibration of an Active LAser-Camera Scanner (ALACS), a novel perception module for robust and high-precision fruit localization. The hardware of the ALACS mainly consists of a red line laser, an RGB camera, and a linear motion slide, which are seamlessly integrated into an active scanning scheme where a dynamic-targeting laser-triangulation principle is employed. A high-fidelity extrinsic model is developed to pair the laser illumination and the RGB camera, enabling precise depth computation when the target is captured by both sensors. A random sample consensus-based robust calibration scheme is then designed to calibrate the model parameters based on collected data. Comprehensive evaluations are conducted to validate the system model and calibration scheme. The results show that the proposed calibration method can detect and remove data outliers to achieve robust parameter computation, and the calibrated ALACS system is able to achieve high-precision localization with the maximum depth measurement error being less than 4 mm at distance ranging from 0.6 to 1.2 m.

Multivariable Linear Position Control Based on Active Disturbance Rejection for Two Linear Slides Coupled to a Mass

Active Disturbance Rejection Control (ADRC) is a promising approach that has emerged to deal with uncertainties, which has received many practical applications in motion controls. This paper presents a multivariable controller for active disturbance rejection (ADR) based on an extended state linear observer for tracking the linear position trajectory of a mass moved by two linear slides, each one driven by a DC motor. The linear extended state observer is used to estimate the endogenous and exogenous disturbances of the system, which are assumed to be unknown, but bounded. Therefore, the feedback system prevents each actuator from operating at different forward speeds, and thus a synchronization between the two actuators is achieved by moving the common mass smoothly. The simulation and the experimental results show the effectiveness and robustness of the controller proposal when moving the mass with both actuators.

Optimization of Machining Parameters to Minimize Cutting Forces and Surface Roughness in Micro-Milling of Mg13Sn Alloy.

This comprehensive study investigates the micro-milling of a Mg13Sn alloy, a material of considerable interest in various high-precision applications, such as biomedical implants. The main objective of the study was to explore the optimizations of variable feed per tooth (fz), cutting speed (Vc), and depth of cut (ap) parameters on the key outcomes of the micro-milling process. A unique experimental setup was employed, employing a spindle capable of achieving up to 60,000 revolutions per minute. Additionally, the study leveraged linear slides backed by micro-step motors to facilitate precise axis movements, thereby maintaining a resolution accuracy of 0.1 μm. Cutting forces were accurately captured by a mini dynamometer and subsequently evaluated based on the peak to valley values for Fx (tangential force) and Fy (feed force). The study results revealed a clear and complex interplay between the varied cutting parameters and their subsequent impacts on the cutting forces and surface roughness. An increase in feed rate and depth of cut significantly increased the cutting forces. However, the cutting forces were found to decrease noticeably with the elevation of cutting speed. Intriguingly, the tangential force (Fx) was consistently higher than the feed force (Fy). Simultaneously, the study determined that the surface roughness, denoted by Sa values, increased in direct proportion to the feed rate. It was also found that the Sa surface roughness values decreased with the increase in cutting speed. This study recommends a parameter combination of fz = 5 µm/tooth feed rate, Vc = 62.8 m/min cutting speed, and ap = 400 µm depth of cut to maintain a Sa surface roughness value of less than 1 µm while ensuring an optimal material removal rate and machining time. The results derived from this study offer vital insights into the micro-milling of Mg13Sn alloys and contribute to the current body of knowledge on the topic.

Looking for the smallest linear slide in the world?

AbstractPM bv, a manufacturer of precision linear bearings and linear slides in the Netherlands, has the smallest linear precision slide available in the industry, the MSR 3. It is designed for the optical, microelectronics, and laser industry where precise movements are required, often within tight installation spaces. The design offers ultrasmooth motion and high repeatability.

Implementation and Performances Evaluation of Advanced Automotive Lateral Stability Controls on a Real-Time Hardware in the Loop Driving Simulator

This study concerns the comparative investigation of two advanced lateral stability automotive controllers with respect to a commercial solution. The research aims to improve the stability performances achieved by a combined tracking of yaw rate and side-slip angle through the application of optimal efforts. The proposed solutions are based on Linear Quadratic Regulation and Sliding Mode Control, respectively. Both rely on the same approach for the control objective definition but differ from the action perspective. This solution involves the adoption of a differential braking actuation technique to deliver a desired yaw moment to the car body to track controlled states. Indeed, a sliding controller can also traction torques of hub-motor configurations as well as steering corrections, achieving vehicle stability and a driving response in accordance with the pilot’s intentions. Calibration and validation of the controllers are performed through a Hardware-in-the-Loop simulation rig, along with a real-time static simulator, performing different close-loop maneuvers to assess achievements in terms of lateral stability. Results show that both solutions ensure higher handling performances if compared to Non-controlled or Commercial-controlled vehicle scenarios.

Miniature camera module with a hollow linear ultrasonic motor-based focus feature

The construction of a miniature camera module that can explore inside limited spaces is of great interest for the design of millimeter-scale devices, such as endoscopes. This article presents a miniature camera module with a focus feature using a hollow linear ultrasonic motor. The hollow stator, which is simplified by the expansion and thickness-shear piezoelectric effects, is suitable for the miniaturization of the camera module because it can contain a lens group. The linear slider, which is thin and cylindrical with a slit, is inserted into the stator’s hole and generates a preload that exploits optimal motor performance measures. The resultant camera module is 4.6 mm × 4.6 mm square, which is the smallest one of camera modules reported to date. The motion of the miniature camera module is demonstrated by the wire-driven mechanism and a visual feedback control system. The orientation of the camera module head is controlled by a wire-driven mechanism until the target object is set in the range of view. The lens group placed inside the slider is controlled by the hollow linear ultrasonic motor in a visual feedback-loop system.

Development of a Mini Compression Test Machine using Arduino Microcontroller as Texture Analyzer Prototype

A texture analyzer is a standard device to measure food texture properties. This study aims to develop a mini compression test machine prototype that can function as a texture analyzer with simple operation and portability. The components and materials were chosen based on: low cost, manufacturability, and availability in the local Indonesian market. The prototype dimension was 375 × 215 × 450 mm, and used a linear ball screw slider for the translation movement with a 200 mm effective sliding distance. For obtaining the compression load, a 10 kg load cell was used, and it was replaceable by a load cell with a lower capacity if a higher measurement accuracy was required. After calibration, the linear vertical displacement and load cell had ±0.1 mm and ±1 g of accuracy, respectively. The prototype was tested to measure the texture properties of potato chops. As a result, the machine could successfully measure the load and displacement data and detect a crack phenomenon, verifying its usability as a food texture analyzer.

Interactive deformable electroluminescent devices enabled by an adaptable hydrogel system with optical/photothermal/mechanical tunability.

Deformable electroluminescent devices (DELDs) with mechanical adaptability are promising for new applications in smart soft electronics. However, current DELDs still present some limitations, including having stimuli-insensitive electroluminescence (EL), untunable mechanical properties, and a lack of versatile stimuli response properties. Herein, a facile approach for fabricating in situ interactive and multi-stimuli responsive DELDs with optical/photothermal/mechanical tunability was proposed. A polyvinyl alcohol (PVA)/polydopamine (PDA)/graphene oxide (GO) adaptable hydrogel exhibiting optical/photothermal/mechanical tunability was used as the top ionic conductor (TIC). The TIC can transform from a viscoelastic state to an elastic state via a special freezing-salting out-rehydration (FSR) process. Meanwhile, it endows the DELDs with a photothermal response and thickness-dependent light shielding properties, allowing them to dynamically demonstrate "on" or "off" or "gradually change" EL response to various mechanical/photothermal stimuli. Thereafter, the DELDs with a viscoelastic TIC can be utilized as pressure-responsive EL devices and laser-engravable EL devices. The DELDs with an elastic TIC can withstand both linear and out-of-plane deformation, enabling the designs of various interactive EL devices/sensors to monitor linear sliders, human finger bending, and pneumatically controllable bulging. This work offers new opportunities for developing next-generation EL-responsive devices with widespread application based on adaptable hydrogel systems.

Ocean Wave Energy Harvesting via Scotch Yoke-based Rotational Generation

Harvesting energy from ocean wave is a promising renewable energy source due to its high efficiency, carbon-free, it is not affected by depletion of fossil fuels, and it is replenished constantly. The existing generators used in wave energy harvesting such as linear generator and slider crank mechanism have some limitations, which include lower efficiency and technologically challenging. Thus, in this work, wave energy harvesting technique using rotational generator based on scotch yoke mechanism is proposed. A typical slider crank to convert linear motion into rotational motion is replaced by scotch yoke mechanism to yield higher efficiency. A comparison of the performance of wave energy system between employing slider crank and scotch yoke is made to evaluate the superiority of the proposed mechanism. From the results obtained in this work, it is found that the output voltage of rotational generator employing scotch yoke mechanism is higher compared to that of rotational generator employing slider crank for the same input power. Thus, rotational generator by employing scotch yoke mechanism can be one of the alternative methods for ocean wave energy harvesting.

Classification of Guide Rail Block by Xception Model

Linear guide rail blocks are used in linear slide rail accessories to scrape off oil stains in the rails, installed on the front and rear ends of the slider. They are also used in milling machines, lathes, automated machines, robotic arms, electronic instruments, and so on. At present, the industry relies on manpower to carry out the quality inspection of this rail block which is difficult to standardize. Thus, automatic and digital deep learning inspection technology is introduced for the inspection. To understand the suitability of deep learning techniques applied to the linear guide block inspection process, we adopt the convolutional neural network model architecture and use the Xception model. In model training, the training effect is improved by amplifying the image method and testing many different defects. Through the Xception model, the training accuracy is about 98.7% after 30 epochs, the validation accuracy is about 97.4%, and the test accuracy is about 91.8%.

Ultra high precision in-vacuum long trace profiler for real time slope determination of optical surface

The development of an in-vacuum long trace profiler (IVLTP) which can provide ultra high precision real time measurements on the surface slope of optical elements is reported. The unique features of this instrument include a specifically designed ultra high repeatability linear slide, a pentamirror composed of two plane mirrors of ultra low slope error, and an ultra high vacuum (UHV) compatible complementary metal oxide semiconductor (CMOS) image sensor. The mechanical system is made of Invar 36 alloy to reduce the room temperature drift effect during data acquisitions. Each IVLTP scan completes in 120 seconds, covering a 168 mm of surface length and generating more than 5000 slope data points. The root mean square (RMS) of the difference between two consecutive scans was found to be 0.0081 μrad on average and 0.0045 μrad RMS at its best. The main application of this IVLTP is to provide the real time feedback signals needed for controlling the 25-actuator surface benders of the active mirrors and active gratings installed in the ultra high resolution soft X-ray beamlines at the Taiwan Photon Source (TPS).

Implementation and Stabilization of a Quadcopter Using Arduino and the Combination of LQR and SMC Methods

This paper presents a combination of Linear Quadratic Regulator (LQR) and Sliding Mode Control (SMC) methods to control a four-rotor unmanned aerial vehicle (UAV) that takes off and lands vertically (VTOL). Although controlling UAVs is difficult due to their highly nonlinear characteristics, the controller successfully controlled and stabilized the quadcopter in altitude and attitude by combining the advantages of the nonlinear and linear controllers. The Newton-Euler method is employed to build the dynamic model of the quadcopter, which is divided into two subsystems: the under-controlled subsystem and the fully actuated subsystem. The entire controller model was demonstrated in MATLAB/Simulink, and results demonstrating the controller's performance in various scenarios were obtained.

Comparative study of post-impact motion control of a flexible arm space robot

Designing a controller to manipulate a flexible space robot is hampered by the inherent complex nonlinear dynamics. Furthermore, the collision of a space robot with an external object in the space environment often leads to degradation of the space robot system. Therefore, an effective control algorithm is necessary for a successful space robot mission to regulate the motion of the entire system after an impact. This paper presents a comparative study on the performance of two different composite controllers to control post-impact motion of the space robot with two-link flexible arms. A performance comparison study helps to choose a better controller to carry out specific tasks. The dynamics of a space robot with flexible manipulators are highly nonlinear and coupled, hence split into rigid and flexible motion to make the control design easier. In this paper, two different composite controllers, namely Nonlinear Model Predictive Control with a Linear Quadratic Regulator (NMPC-LQR) and Sliding Mode Control with Linear Quadratic Regulator (SMC-LQR) are developed. NMPC and SMC are used to control rigid motion of the system, while LQR is used to suppress the flexible motion. The objective of the proposed controllers is to regulate the motion of the entire space robot system, including the flexible manipulator, after impact with an external object. The effectiveness of the proposed composite controllers is demonstrated using numerical simulations. Simulation results confirm that, in the absence of uncertainties, the performance of the control system using the proposed NMPC-LQR is more accurate compared to using SMC-LQR. Furthermore, given uncertainties of mass and inertia of the system, we find NMPC-LQR provides a higher level of accuracy when compared to SMC-LQR.

A roller scanning type prostate palpation sensor system using a cantilever beam type force measurement.

Palpation has been used for centuries in medicine as a screening and diagnosis modality for a number of pathological conditions. However, this technique is subjective since palpation sensitivity depends on the skill and experience of a medical examiner. An objective approach to acquire quantitative tactile information is needed. A roller scanning type palpation sensor system consisting of an x-axis linear slider and a palpation probe for detecting lumps in a soft object such as the prostate tissue is proposed and fabricated in this study. By translating the slider and changing the palpation angle of the probe, a chrome steel ball which was the contact component indented and scanned the surface of soft silicone phantoms embedded with hard lumps. Lumps were detected by measuring reaction force waveform fluctuations. Fundamental characteristics of the proposed sensor system were validated by comparison with the ground truth load cell output and showed a strong linear correlation with r2=0.9985. On silicone samples with hard lumps, the system was able to detect lumps of various sizes embedded at the depth of 5mm. From the results, the proposed sensor system holds potential for tissue characterization.

Automatic alignment system device of micro–nanofluid control chip and its application

PurposeThe purpose of this study is to provide a micro-nano chip automatic alignment system. Used for micron and nanometer channel alignment of microfluidic chip.Design/methodology/approachIn this paper, combined with the reconstructed micro–nanoscale Hough transform theory, a “clamp–adsorb–rotate” chip alignment method is proposed. The designed alignment system includes a microscopic identification device, a clamping device and a suction device. After assembly, the straightness of the linear slide rail in the horizontal and vertical directions was tested, respectively. The results show that in the horizontal and vertical directions, the linearity error of the linear slide is +0.29 and 0.30 µm, respectively, which meets the requirement of chip alignment accuracy of 15 µm. In the direction of rotation, the angular error between the microchannel and the nanochannel is ±0.5°. In addition, an alignment flow experiment of the chip is designed. The results demonstrate that the closer the angle between the microchannel and the nanochannel is to 90°, the fluid fills the entire channel. Compared with the conventional method, the method and the assembly system realize fully automatic double-layer chip alignment.FindingsA mechanical device designed by Hough transform theory can realize microfluidic chip alignment at nanometer and micron level.Originality/valueThe automatic alignment device adopts Hough transform principle and can be used for microfluidic chip alignment.