Servo Technology Research Articles

The docking control system of an autonomous underwater vehicle combining intelligent object recognition and deep reinforcement learning

This study develops a visual-based docking system (VDS) for an autonomous underwater vehicle (AUV), significantly enhancing docking performance by integrating intelligent object recognition and deep reinforcement learning (DRL). The system overcomes traditional navigation limitations in complex and unpredictable environments by using a variable information dock (VID) for precise multi-sensor docking recognition in the AUV. Employing image-based visual servoing (IBVS) technology, the VDS efficiently converts 2D visual data into accurate 3D motion control commands. It integrates the YOLO (short for You Only Look Once) algorithm for object recognition and the deep deterministic policy gradient (DDPG) algorithm, improving continuous motion control, docking accuracy, and adaptability. Experimental validation at the National Cheng Kung University towing tank demonstrates that the VDS enhances control stability and operational reliability, reducing the mean absolute error (MAE) in depth control by 42.03% and pitch control by 98.02% compared to the previous method. These results confirm the VDS's reliability and its potential for transforming AUV docking.

Energy-Aware Camera Location Search Algorithm for Increasing Precision of Observation in Automated Manufacturing

Visual servoing technology is well developed and applied in many automated manufacturing tasks, especially in tools’ pose alignment. To access a full global view of tools, most applications adopt an eye-to-hand configuration or an eye-to-hand/eye-in-hand cooperation configuration in an automated manufacturing environment. Most research papers mainly put efforts into developing control and observation architectures in various scenarios, but few have discussed the importance of the camera’s location in the eye-to-hand configuration. In a manufacturing environment, the quality of camera estimations may vary significantly from one observation location to another, as the combined effects of environmental conditions result in different noise levels of a single image shot in different locations. In this paper, we propose an algorithm for the camera’s moving policy so that it explores the camera workspace and searches for the optimal location where the image’s noise level is minimized. Also, this algorithm ensures the camera ends up at a suboptimal (if the optimal one is unreachable) location among the locations already searched with the limited energy available for moving the camera. Unlike a simple brute-force approach, the algorithm enables the camera to explore space more efficiently by adapting the search policy by learning the environment. With the aid of an image-averaging technique, this algorithm, in the use of a solo camera, achieves observation accuracy in eye-to-hand configurations to a desirable extent without filtering out high-frequency information in the original image. An automated manufacturing application was simulated, and the results show the success of this algorithm’s improvement in observation precision with limited energy.

Generation of uniform micro-textured structures by two-dimensional modulation fly-cutting

Micro-textured structures are widely applied in the fields of aerospace, military and medical etc. because of their unique properties such as self-cleaning, structural color and antibacterial effects. The traditional fast tool servo technology is believed to be an ideal machining method for the fabrication of micro-textured structures, however, its frequency response is limited by the varied linear velocity along the radial direction of workpieces, which make it difficult to machine uniform micro-textured structures. In this paper, a novel two-dimensional modulation fly-cutting system is developed to machine uniform micro-textured structures. In the machining system, the principal cutting motion is generated by a fly-cutting while a sinusoidal excitation motion as the assistive modulation is generated by a two-dimensional vibration platform. The two-dimensional vibration platform can apply excitation both in the x- and z-directions to the workpiece. By changing the excitation frequency, tool rotation radius and feed rate in X-axis, the corresponding optimal offset angle, length-width ratio and density of micro-textured structures can be obtained. Also, uniform concave-convex micro-textured structures are fabricated further by two-dimensional modulation of the principal cutting motion. According to the experimental results, uniform concave-convex micro-textured structures have good quality, which proves that the present machining method is effective. The present study provides an effective machining method for fabrication of micro-textured structures, and also serves as a reference for the fabrication of other similar micro-textured structures.

Crop Recognition Method Based On End-effector

With the increasing global population, the demand for agriculture is also on the rise. The crucial stages of agricultural production, namely fruit identification and picking, play a vital role in enhancing product quality and minimizing losses. Traditional manual processing methods, although time-tested, are not only inefficient but also challenging to maintain consistency, making them inadequate to meet the large-scale requirements of modern agricultural production. Consequently, the integration of automation technology has become a necessity. For agricultural robot the machine vision system often need to work in two typical environments, the field environment and the orchard environment. Depending on the varying objectives of operation in diverse environments, crop robots require the ability to rapidly identify fruits within images featuring significant color disparities between crops and two-dimensional field backgrounds. Consequently, a visual servo control system is being investigated. A novel camera attitude search method that employs active visual servo technology to minimize occlusions during orchard search is proposed. The recognition function of the end-effector is exceedingly crucial. The precision of the end effector's identification capabilities directly influences the success rate of automated operations. This is particularly evident in fruit picking, sorting, and other tasks, where the diverse shapes, maturity levels, and colors of fruits present significant challenges to the robotic arm's end effector. The rapid advancement of deep learning technology, however, offers a novel solution for the recognition of fruits by the robotic arm's end effector. By emulating the human visual system, deep learning models can extract the feature representation of fruits from vast amounts of data, enabling accurate identification of fruits in various conditions.

The-Application-of-Servo-Control-Technology-in-Robot-Positioning-and-Tracking-System-via-Heuristic-Algorithm

Based on the visual servo technology, this paper focuses on the visual tracking algorithm of moving objects and the dynamic grasping control method of robots, and realizes the automatic loading and unloading of moving workpieces to improve production efficiency. Firstly, aiming at the difficulties in the selection of high-dimensional features extracted by visual servo, this paper proposes a training method of generation countermeasure network based on heuristic algorithm by using the efficient search ability of heuristic algorithm. Secondly, we use image processing technology to realize real-time recognition and location of workpieces under complex background. According to the positioning results, an adaptive dual rate unscented Kalman filter visual tracking algorithm is proposed to solve the problem of delay and multi sampling rate in visual servo, and realize visual tracking of moving objects. The experimental results show that the proposed visual tracking algorithm has better stability and real-time performance.

Research on Electro-hydraulic Servo Valve Structure and Control Algorithm of System with Servo Valve

Background: With the continuous progress of electronic information technology, people have begun to study the combination of electronic information technology and hydraulic technology to achieve more accurate and flexible control. Electro-hydraulic servo technology was thus developed. Much attanetion has been paid to electro-hydraulic servo valve,a key component of electrohydraulic servo technology. Objective: The number of stages of the electro-hydraulic servo valve, the structure form of the electro- hydraulic servo valve hydraulic front stage, the feedback form of the electro-hydraulic servo valve, the output form of electro-hydraulic servo valve, and the control algorithm based on the application of electro-hydraulic servo valve are analyzed and commented respectively. Combined with associated patents, the research direction and hot topics of electro-hydraulic servo valves are analyzed. Method: The electro-hydraulic servo valves were briefly classified; and then the problems of different types of valves were discussed in depth. Results: By analyzing the problems of electro-hydraulic servo valves, the problems of how to improve the control accuracy, response speed, anti-interference ability, service life and cost reduction of electro-hydraulic servo valves are analyzed comprehensively, and the future development prospect of electro-hydraulic servo valves is predicted and outlooked. Conclusion: Analyzing and discussing the existing hot issues of electro-hydraulic servo valves helps to update and change the electro-hydraulic servo valves, and makes corresponding references for the subsequent research of electro-hydraulic servo valves.

Numerical Simulation and Monitoring Analysis of Deep Foundation Pit Excavation Based on Concrete Support Axial Force Servo Technology

Numerical Simulation and Monitoring Analysis of Deep Foundation Pit Excavation Based on Concrete Support Axial Force Servo Technology

Integrated Application and Optimized Design Strategies of Automatic and Servo Control Systems for Industrial Robots

Abstract At present, industrial robots have been widely used in industrial fields. This topic focuses on optimizing the system of servo control technology for the automatic control of industrial robots. Taking the optimization of robot automatic grasping technology with visual servo as an example, image-based and position-based visual servo control schemes are designed, respectively, and adaptive gain and first-order non-singular linear equations are used for visual servo performance enhancement. Open-loop control and closed-loop control are combined to create the visual servo-based automatic robot grasping docking method. The dynamic tracking effect of visual servo technology and the grasping performance of automatic grasping technology are evaluated through test experiments. The results can be obtained that the image-based and position-based visual servo control schemes can realize better dynamic tracking of objects, and the tracking accuracy is kept within 1.1mm and 8mm in the uniform and variable speed experiments, respectively. The robot’s automatic target grasping error gradually decreases to about 0 with the increase in the number of steps, and the system exhibits high grasping accuracy (over 96.67%) and speed (within 0.80s) at an operating speed lower than 20 m/s. Dynamic tracking performance and target grasping accuracy are certain features of the automatic robot grasping method based on the visual servo in this paper.

A Review of Advances in Fabrication Methods and Assistive Technologies of Micro-Structured Surfaces

Micro-structured surfaces possess excellent properties of friction, lubrication, drag reduction, antibacterial, and self-cleaning, which have been widely applied in optical, medical, national defense, aerospace fields, etc. Therefore, it is requisite to study the fabrication methods of micro-structures to improve the accuracy and enhance the performance of micro-structures. At present, there are plenty of studies focusing on the preparation of micro-structures; therefore, systematic review of the technologies and developing trend on the fabrication of micro-structures are needed. In present review, the fabrication methods of various micro-structures are compared and summarized. Specially, the characteristics and applications of ultra-precision machining (UPM) technology in the fabrication of micro-structures are mainly discussed. Additionally, the assistive technologies applied into UPM, such as fast tool servo (FTS) technology and slow tool servo (STS) technology to fabricate micro-structures with different characteristics are summarized. Finally, the principal characteristics and applications of fly cutting technology in manufacturing special micro-structures are presented. From the review, it is found that by combining different machining methods to prepare the base layer surface first and then fabricate the sublayer surface, the advantages of different machining technologies can be greatly exerted, which is of great significance for the preparation of multi-layer and multi-scale micro-structures. Furthermore, the combination of ultra-precision fly cutting and FTS/STS possess advantages in realizing complex micro-structures with high aspect ratio and high resolution. However, residual tool marks and material recovery are still the key factors affecting the form accuracy of machined micro-structures. This review provides advances in fabrication methods and assistive technologies of micro-structured surfaces, which serves as the guidance for both fabrication and application of multi-layer and multi-scale micro-structures.

Research on VR equipment based on VR technology

Virtual reality technology, also known as virtual reality or psychic technology, is a new practical technology developed in the 20th century. Virtual reality technology includes computer, electronic information, simulation technology, its basic realization is based on computer technology, the use and integration of three-dimensional graphics technology, multimedia technology, simulation technology, display technology, servo technology and other high-tech latest development achievements, With the help of computer and other equipment to produce a realistic three-dimensional vision, touch, smell and other sensory experience of the virtual world, so that people in the virtual world have a sense of being in the scene. With the continuous development of social productivity and science and technology, the demand for VR technology is increasingly strong in all walks of life. VR technology has also made great progress and gradually become a new field of science and technology.

Modeling of Rapid Response Characteristics of Piezoelectric Actuators for Ultra-Precision Machining

Piezoelectric actuators are characterized by high positioning accuracy, high stiffness and a fast response and are widely used in ultra-precision machining technologies such as fast tool servo technology and ultrasonic machining. The rapid response characteristics of piezoelectric actuators often determine the overall quality of machining. However, there has been little research on the fast response characteristics of piezoelectric actuators, and this knowledge gap will lead to low precision and poor quality of the final machining. The fast response characteristics of a piezoelectric actuator were studied in this work. Firstly, the piezoelectric actuator was divided into a no-load state and a load state according to the working state. A fast response analysis and output characteristic analysis were carried out, the corresponding dynamic model was established, and then the model was simulated. Finally, an experimental system was established to verify the dynamic model of the piezoelectric actuator's fast response by conducting an experiment in which the piezoelectric actuator bounces a steel ball. The experimental results verify the correctness of the model and show that the greater the cross-sectional area and height of the piezoelectric actuator, the higher the bouncing height of the ball, and the better the dynamic performance of the piezoelectric actuator. It is believed that this study has guiding significance for the application of the dynamic characteristics of piezoelectric actuators in the machining field.

Image moments-based visual servoing control of bagged agricultural materials handling robot

Manual handling is less efficient and sometimes even hazardous to humans in many areas, for example, agriculture. Using robots in those areas not only avoids human contact with such dangerous agricultural materials but also improves working efficiency. The motion of a robot is controlled using a technique called visual servoing that uses feedback information extracted from a vision sensor. In this study, a visual servoing method was proposed based on learning features and image moments for 3D targets to solve the problem of image moment-based visual servoing. A Gaussian process regression model was used to map the relationship between the image moment invariants and the rotational angles around the X- and Y-axes of the camera frame (denoted as γ and β). To obtain maximal decoupled structure and minimal nonlinearities of the image Jacobian matrix, it was assumed two image moment features, which are linearly proportional to γ and β. In addition to the other four standardized image moment features, a 6-DOF image moment-based visual servoing controller for the agricultural material handling robot was designed. Using this method, the problem of visual servoing task failure due to the singularity of the Jacobian matrix was solved, and it also had a better convergence effect for the part of the target image beyond the field of view and large displacement visual servoing system. The proposed algorithm was validated by carrying out experiments tracking bagged flour in a six-degree-of-freedom robotic system. The final displacement positioning accuracy was accurate to the millimeter level and the direction angle positioning accuracy was accurate to the 0.1 level. The method still has a certain convergence effect when the target image is beyond the field of view. The experimental results have been presented to show the adequate behavior of the presented approach in robot handling operations. It provides reference for the application of visual servoing technology in the field of agricultural robots and has important theoretical significance and practical value. Keywords: image moments, visual servoing, Jacobian matrix, agricultural material handling robot DOI: 10.25165/j.ijabe.20231601.7050 Citation: Li H, Zuo Z J, Chi R Q, Du Y F, Mao E R. Image moments-based visual servoing control of bagged agricultural materials handling robot. Int J Agric & Biol Eng, 2023; 16(1): 212–219.

A Novel Fast Servo Tool Device with Double Piezoelectric Driving.

The fast tool servo (FTS) technology has unique advantages in the machining of complex surfaces such as special-shaped targets and free-form surfaces. In view of the shortcomings in the performance of the existing FTS device, this paper puts forward a novel FTS which uses two piezoelectric ceramics instead of flexure hinges to provide restoring force. Firstly, the feasibility of the double-drive principle is verified theoretically, and the corresponding mechanism is optimized accordingly. Then, the system control hysteresis model is established and identified, and the appropriate control strategy is designed. Finally, the performances of the proposed FTS device are tested, and a typical microstructure is machined based on the device and ultra-precision lathe. The results indicate that the proposed device effectively improves the performance of the FTS system, which is useful for the processing of microstructures and free-form surfaces.

Tool path modeling and fabrication of multi-boundary lens array by tool offset end-fly-cutting

Lens arrays are widely used in advanced industrial fields, such as national defense, medical care, and aerospace, because of their exceptional optical performance. Single-point diamond turning based on fast/slow tool servo technology is a common machining method for fabricating lens arrays; however, the constant-angle or constant-arc-length sampling of its spiral tool trajectory leads to an uneven cutting speed, and thus, the machined morphology of the lens arrays deviates from their theoretical morphology. This shortcoming seriously restricts the high-efficiency production of large-scale lens arrays, as well as reduces design accuracy. Accordingly, a novel method is proposed herein for the fabrication of multi-boundary lens arrays by tool offset end-fly-cutting. First, a mathematical model was established to generate a uniform tool trajectory for the subsequent fabrication of square and hexagonal boundary lens arrays. From a comparison of the measured and simulated results, the root-mean-square error of the sectional curves of the multi-boundary lens array is below 1 μm, proving the effectiveness of the production method. The developed method provides a new technical scheme for the fabrication of multi-boundary lens arrays and a theoretical reference for machining multiscale microstructures.

Navigation Control Method of Indoor Mobile Robot Based on Visual Servo

In order to improve the navigation control effect of indoor mobile robot, this paper studies the navigation control method of indoor mobile robot combined with visual servo technology. For the problem that the target may be out of the camera’s field of view during the servo process, a control algorithm with field-of-view constraints is proposed, which assigns a certain weight to the image feature error at each moment. Moreover, this paper realizes the servo process that the image features are always located in the field of view by setting the variable values involved in the weight value calculation method. Through the simulation test, it is verified that the indoor mobile robot navigation control method based on visual servo has certain effects.

Offset-tool-servo diamond end flycutting multi-layer hierarchical microstructures

Microstructural functional surfaces inspired by nature have been widely applied in the fields of optics, aerospace, electronics and communication. There function not only originates from a single layer of surface microstructures, but also depends largely on the combined effect of hierarchical structures. Hierarchical microstructures are generally overlapped by two or more layers to generate a functional complementary and combined surface. Fast/slow tool servo technology is usually employed to fabricate micro/nanostructures. However, it is challenging to fabricate multi-layer hierarchical microstructures with sharp edges using only a commercial three-axis ultra-precision lathe. In the present study, a novel ultra-precision offset-tool-servo end flycutting (OTSEF) system was developed. Considering the geometry and installation pose of the diamond tool, a tool path based on the OTSEF system was planned, and different hierarchical microstructures could be fabricated using a compensated linear tool trajectory. Furthermore, a mathematical modeling for tool path generation for complex multi-layer hierarchical microstructures, overlapping micro-lens units with secondary pyramid structures, was established. After determining and compensating for the misalignment between the center of the diamond tool and workpiece, hierarchical microstructures with high precision and quality were successfully fabricated. The theoretical and experimental results demonstrate that the OTSEF system has unique advantages in the fabrication of multi-layer hierarchical microstructures. The present research not only provides a deep insight into tool path modeling but also a machining method for multi-layer hierarchical microstructures.

Research on PID Position Control of a Hydraulic Servo System Based on Kalman Genetic Optimization

With the wide application of hydraulic servo technology in control systems, the requirement of hydraulic servo position control performance is greater and greater. In order to solve the problems of slow response, poor precision, and weak anti-interference ability in hydraulic servo position controls, a Kalman genetic optimization PID controller is designed. Firstly, aiming at the nonlinear problems such as internal leakage and oil compressibility in the hydraulic servo system, the mathematical model of the hydraulic servo system is established. By analyzing the working characteristics of the servo valve and hydraulic cylinder in the hydraulic servo system, the parameters in the mathematical model are determined. Secondly, a genetic algorithm is used to search the optimal proportional integral differential (PID) controller gain of the hydraulic servo system to realize the accurate control of valve-controlled hydraulic cylinder displacement in the hydraulic servo system. Under the positioning benchmark of step signal and sine wave signal, the PID algorithm and the genetic optimized PID algorithm are compared in the system simulation model established by Simulink. Finally, to solve the amplitude fluctuations caused by the GA optimized PID and reduce the influence of external disturbances, a Kalman filtering algorithm is added to the hydraulic servo system to reduce the amplitude fluctuations and the influence of external disturbances on the system. The simulation results show that the designed Kalman genetic optimization PID controller can be better applied to the position control of the hydraulic servo system. Compared with the traditional PID control algorithm, the PID algorithm optimized by genetic algorithm improves the system’s response speed and control accuracy; the Kalman filter is a good solution for the amplitude fluctuations caused by GA-optimized PID that reduces the influence of external disturbances on the hydraulic servo system.

Development of two-redundant multi-turn absolute encoder based on small modulus reducer

In order to meet the development needs of aerospace servo technology, the angular displacement sensor, which compact structure, high reliability, and be able to adapt to harsh working environments is used for the measurement and feedback of the high speed of the servo motor output shaft. The design of a two-redundant multi-turn absolute encoder based on a single-turn absolute encoder and a precision small modulus reducer, which realizes the high speed measurement of the servo motor shaft at 8000 rpm. Product performance meets the technical indicators of similar products of HEIDENHAIN encoders, can withstand high temperature, long working life, good dynamic performance, small space and light weight. System test and simulation analysis show that the design technical scheme is effective and feasible, can meet the requirements of the servo system.

Localized electrodeposition micro additive manufacturing of pure copper microstructures

The fabrication of pure copper microstructures with submicron resolution has found a host of applications, such as 5G communications and highly sensitive detection. The tiny and complex features of these structures can enhance device performance during high-frequency operation. However, manufacturing pure copper microstructures remain challenging. In this paper, we present localized electrochemical deposition micro additive manufacturing (LECD-μAM). This method combines localized electrochemical deposition (LECD) and closed-loop control of atomic force servo technology, which can effectively print helical springs and hollow tubes. We further demonstrate an overall model based on pulsed microfluidics from a hollow cantilever LECD process and closed-loop control of an atomic force servo. The printing state of the micro-helical springs can be assessed by simultaneously detecting the Z-axis displacement and the deflection of the atomic force probe cantilever. The results showed that it took 361 s to print a helical spring with a wire length of 320.11 μm at a deposition rate of 0.887 μm s−1, which can be changed on the fly by simply tuning the extrusion pressure and the applied voltage. Moreover, the in situ nanoindenter was used to measure the compressive mechanical properties of the helical spring. The shear modulus of the helical spring material was about 60.8 GPa, much higher than that of bulk copper (∼44.2 GPa). Additionally, the microscopic morphology and chemical composition of the spring were characterized. These results delineate a new way of fabricating terahertz transmitter components and micro-helical antennas with LECD-μAM technology.

Intelligent Shopping Cart Design Based on the Multi-Sensor Information Fusion Technology and Vision Servo Technology

In order to promote the intelligent transformation of service-oriented robot used in supermarkets, an intelligent shopping cart has been designed in this paper to realize the integration of auto following, shopping and payment based on the multi-sensor information fusion technology and vision servo technology. Firstly, a distributed sensor fusion structure was designed including photoelectric, ultrasonic sensors and monocular camera. Then, all the collected data were fused during auto following process of the intelligent shopping cart, and the commodity information could be identified to form the billing information by which the customer could complete the payment by scanning the payment QR code and the corresponding records also can be viewed by logging in the Wechat applet.